JP4633857B1 - Method for evaluating heat-sinterability of organic-coated metal particles, method for producing heat-sinterable metal paste, and method for producing metal member assembly - Google Patents

Abstract

[PROBLEMS] To provide an evaluation method capable of easily, quickly and easily judging the heat-sinterability of organic-coated metal particles, an efficient method for producing a heat-sinterable metal paste excellent in heat-sinterability, and a metal having excellent bondability. Provided is an efficient manufacturing method for a member-made assembly.
Each of the organic-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature of the organic substance covering the surface of the metal particles and the pyrolysis peak temperature of the organic substance itself. Are compared to determine the heat sinterability of the metal particles. The activation energy in the thermal decomposition reaction of the organic matter is calculated, and the heat sinterability of the metal particles is determined from the value. By using these evaluation methods, organic coated metal particles having excellent heat sinterability are selected and mixed with a volatile dispersion medium to produce a paste. The heat-sinterable metal paste is interposed between metal members and heat-sintered to produce a metal member assembly.
[Selection] Figure 2

Description

The present invention relates to a method for evaluating the heat-sinterability of organic-coated metal particles, and a heat-sinterable metal paste comprising selecting organic-coated metal particles having excellent heat-sinterability by this evaluation method and mixing with a volatile dispersion medium. And a manufacturing method of a metal member assembly comprising manufacturing a heat-sinterable metal paste by this manufacturing method and heat-sintering the metal paste between the metal members.

A conductive ink using heat-sinterable metal particles as a conductive filler has a characteristic of having excellent conductivity. In particular, it is known that metal nanoparticles having an average particle size of 100 nm or less sinter even at temperatures considerably lower than the melting point of the bulk material (for example, 1064 ° C. for gold and 962 ° C. for silver). Silver nanoparticles of several nm to several tens of nm can be sintered at about 200 ° C., and conductive ink in which such metal nanoparticles are dispersed in a liquid binder (for example, epoxy resin, organic solvent) is wired. Many paste agents for pattern formation have been proposed (Patent Documents 1 to 3).

So-called non-nanometallic particles having an average particle diameter of 100 nm or more necessarily have a lower sinterability at a lower temperature than nanoparticles. However, it does not sinter at all even at low temperatures, and there are very rare cases that can be sintered at low temperatures depending on the manufacturing method, particle diameter, surface coating agent, manufacturing company, and the like. However, whether such non-nanometallic particles can be sintered at low temperature is not a method other than evaluating the various properties of the sintered product by actually preparing and heating a paste using a mixer or the like. However, the laborious work which requires time with a test equipment was forced (patent document 4).

JP 2002-324966 A JP 2004-273205 A JP 2008-233503 A WO2007 / 034833A1

As a result of diligent research to solve the above problems, the present inventors can easily, quickly, and easily determine whether organic-coated metal particles are excellent in heat-sinterability. Heat-sinterability of organic-coated metal particles The present invention was completed by finding an evaluation method.
An object of the present invention is to provide an evaluation method that can easily, quickly, and easily determine the heat-sinterability of organic-coated metal particles, an accurate and efficient method for producing a heat-sinterable metal paste having excellent heat-sinterability, and bonding An object of the present invention is to provide an accurate and efficient method for producing a metal member assembly having excellent properties.

This purpose is
“[1] A method for evaluating the heat-sinterability of organic-coated metal particles by thermal analysis,
Each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is the pyrolysis peak temperature of the organic substance itself ( 2) If lower, it is determined that the heat-sinterability of the organic-coated metal particles is excellent,
When the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is equal to or higher than the pyrolysis peak temperature (2) of the organic substance itself, the heat-sinterability of the organic substance-coated metal particles is poor. The method for evaluating heat-sinterability of organic-coated metal particles, characterized in that
[2] If the pyrolysis peak temperature (1) is 2 ° C or more lower than the pyrolysis peak temperature (2), it is judged that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1) is Heat-sintering of organic-coated metal particles according to [1], characterized in that when the temperature is higher than the thermal decomposition peak temperature (2) by 2 ° C or more, the organic-coated metal particles are judged to have poor heat-sinterability Evaluation method of sex.
[2-1] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is lower than 2 ° C, and the pyrolysis peak temperature (1) is the same as the pyrolysis peak temperature (2). The method for evaluating the heat-sinterability of organic-coated metal particles according to [1], wherein the case of equality or higher is higher by 2 ° C or higher.
[2-2] If the pyrolysis peak temperature (1) is 5 ° C. or more lower than the pyrolysis peak temperature (2), it is determined that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1 ) Is higher than the thermal decomposition peak temperature (2) by 5 ° C. or more, it is determined that the heat-sinterability of the organic-coated metal particles is inferior, and the heating of the organic-coated metal particles according to [1] Evaluation method of sinterability.
[2-3] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is lower than 5 ° C, and the pyrolysis peak temperature (1) is the same as the pyrolysis peak temperature (2). The method for evaluating the heat-sinterability of organic-coated metal particles according to [1], wherein the case of equality or higher is higher by 5 ° C or higher.
[2-4] The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic material covering the surface of the organic-coated metal particles is high. -Organic substance according to any one of [1], [2], [2-1], [2-2], [2-3], characterized in that it is selected from intermediate fatty acids and water-repellent derivatives thereof Evaluation method of heat-sinterability of coated metal particles.
[3] A method for evaluating the heat-sinterability of organic-coated metal particles by thermal analysis,
The organic matter-coated metal particles are subjected to thermal analysis in an air stream, and are calculated from the relationship between the temperature increase rate in the thermal analysis and the thermal decomposition peak temperature (1) of the organic matter covering the surface of the metal particles. When the activation energy in the pyrolysis reaction of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, the method for evaluating the heat-sinterability of the organic-coated metal particles is characterized by determining that the heat-sinterability of the organic-coated metal particles is poor.
[3-1] The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic material covering the surface of the organic-coated metal particles is high. -The method for evaluating heat-sinterability of organic-coated metal particles according to [3], wherein the method is selected from intermediate fatty acids and water-repellent derivatives thereof. Is achieved.

This purpose is also
“[4] Each of the organic-coated metal particles and the organic matter itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic matter covering the surface of the metal particles is the heat of the organic matter itself. If it is lower than the decomposition peak temperature (2), it is determined that the heat-sinterability of the organic-coated metal particles is excellent, and the thermal decomposition peak temperature (1) of the organic material covering the surface of the metal particles is the organic material itself. When the thermal decomposition peak temperature (2) is equal to or higher than the thermal decomposition peak temperature (2), it is determined that the organic-coated metal particles have poor heat-sinterability, and then the organic-coated metal particles determined to have excellent heat-sinterability are volatile. A method for producing a heat-sinterable metal paste, wherein the paste is mixed with a dispersion medium to form a paste.
[5] If the pyrolysis peak temperature (1) is 2 ° C or more lower than the pyrolysis peak temperature (2), it is determined that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1) is The production of the heat-sinterable metal paste according to [4], wherein the heat-sinterability of the organic-coated metal particles is judged to be inferior when the temperature is 2 ° C or higher than the thermal decomposition peak temperature (2) Method.
[5-1] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is lower than 2 ° C, and the pyrolysis peak temperature (1) is the same as the pyrolysis peak temperature (2). The method for producing a heat-sinterable metal paste according to [4], wherein the case of equality or higher is a case of higher by 2 ° C. or higher.
[5-2] If the pyrolysis peak temperature (1) is 5 ° C. or more lower than the pyrolysis peak temperature (2), it is determined that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1 ) Is higher than the thermal decomposition peak temperature (2) by 5 ° C. or more, the heat-sinterable metal paste according to [4], wherein the organic-coated metal particles are judged to have poor heat-sinterability Manufacturing method.
[5-3] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is lower than 5 ° C, and the pyrolysis peak temperature (1) is the same as the pyrolysis peak temperature (2). The method for producing a heat-sinterable metal paste according to [4], wherein the case of equality or higher is higher by 5 ° C or higher.
[6] Organic coated metal particles are silver particles or copper particles having an average particle size (median diameter D50) of 0.1 μm or more and 50 μm or less, and organic materials covering the surface of organic coated metal particles are high / intermediate Heat-sintered according to any of [4], [5], [5-1], [5-2], [5-3], characterized by being selected from fatty acids and water-repellent derivatives thereof For producing a conductive metal paste.
[6-1] The boiling point of the volatile dispersion medium is lower than the melting point of the organic-coated metal particles and is 60 ° C. to 300 ° C. [4], [5], [5-1], [ 5-2], [5-3], [6] The method for producing a heat-sinterable metal paste according to any one of [6].
[7] The organic-coated metal particles are subjected to thermal analysis in an air stream, and calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic material covering the surface of the metal particles. When the activation energy in the thermal decomposition reaction of the organic material is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic material-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, it is determined that the heat-sinterability of the organic-coated metal particles is inferior, and then the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste. A method for producing a heat-sinterable metal paste.
[8] The organic-coated metal particles are silver particles or copper particles having an average particle size (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic material covering the surface of the organic-coated metal particles is a high / intermediate grade. The method for producing a heat-sinterable metal paste according to [7], wherein the heat-sinterable metal paste is selected from fatty acids and water-repellent derivatives thereof.
[8-1] The heat-sinterable metal according to [7] or [8], wherein the volatile dispersion medium has a boiling point lower than the melting point of the organic-coated metal particles and is 60 ° C. to 300 ° C. Manufacturing method of paste. Is achieved.

This purpose is also
“[9] Each of the organic-coated metal particles and the organic matter itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic matter covering the surface of the metal particles is the heat of the organic matter itself. If it is lower than the decomposition peak temperature (2), it is determined that the heat-sinterability of the organic-coated metal particles is excellent, and the thermal decomposition peak temperature (1) of the organic material covering the surface of the metal particles is the organic material itself. When the thermal decomposition peak temperature (2) is equal to or higher than the thermal decomposition peak temperature (2), it is determined that the organic-coated metal particles have poor heat-sinterability, and the organic-coated metal particles determined to have excellent heat-sinterability are used as volatile dispersion media. To prepare a heat-sinterable metal paste, and then interpose the heat-sinterable metal paste between a plurality of metal members so that the heat-sinterable metal can be sintered at a temperature higher than that. A method for producing a metal member assembly, comprising heating at
[10] If the pyrolysis peak temperature (1) is 2 ° C or more lower than the pyrolysis peak temperature (2), it is determined that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1) is The method for producing a metal member assembly according to [9], wherein when the temperature is higher than the thermal decomposition peak temperature (2) by 2 ° C or more, it is determined that the heat-sinterability of the organic-coated metal particles is poor. .
[10-1] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is lower than 2 ° C, and the pyrolysis peak temperature (1) is the same as the pyrolysis peak temperature (2). The method for producing a metal member assembly according to [9], wherein the case of equality or higher is a case where the temperature is higher by 2 ° C or higher.
[10-2] When the pyrolysis peak temperature (1) is 5 ° C. or more lower than the pyrolysis peak temperature (2), it is determined that the organic-coated metal particles have excellent heat sinterability, and the pyrolysis peak temperature (1 ) Is higher than the thermal decomposition peak temperature (2) by 5 ° C. or more, it is determined that the heat-sintering property of the organic-coated metal particles is inferior. The metal member assembly according to [9] Production method.
[10-3] The case where the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) is 5 ° C or more lower than the pyrolysis peak temperature (1). The method for producing a metal member joined body according to [9], wherein the case of equality or higher is a case of higher by 5 ° C or higher.
[11] The organic coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic material covering the surface of the organic coated metal particles is a high / intermediate grade. The metal member according to any one of [9], [10], [10-1], [10-2], and [10-3], which is selected from fatty acids and water-repellent derivatives thereof Manufacturing method of joined body.
[11-1] The metal member is made of gold, silver, copper, platinum, palladium, or an alloy of these metals, [9], [10], [10-1], [10 -2], [10-3], [11] The method for producing a metal member assembly according to any one of [11].
[11-2] [9], [10], [10-], characterized in that the heating temperature is 70 ° C. or higher and 400 ° C. or lower, and the atmospheric gas during the heating and sintering is an oxidizing gas containing oxygen. [1], [10-2], [10-3], [11], [11-1] The method for producing a metal member assembly according to any one of [11-1].
[12] The metal member assembly is an electronic component, [9], [10], [10-1], [10-2], [10-3], [11], [ 11-1], [11-2] The method for producing a metal member assembly according to any one of [11-2].
[13] The organic-coated metal particles are subjected to thermal analysis in an air stream, and are calculated from the relationship between the heating rate in the thermal analysis and the thermal decomposition peak temperature (1) of the organic material covering the surface of the metal particles. When the activation energy in the thermal decomposition reaction of the organic material is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic material-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, it is determined that the heat-sinterability of the organic-coated metal particles is poor, and the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste and heat-sinterable. A metal member characterized in that a metal paste is prepared, and then the heat-sinterable metal paste is interposed between a plurality of metal members and heated at a temperature at which the heat-sinterable metal can be sintered. Manufacturing method of joined body.
[14] The organic coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic material covering the surface of the organic coated metal particles is a high / intermediate grade. The method for producing a metal member assembly according to [13], wherein the metal member assembly is selected from fatty acids and water-repellent derivatives thereof.
[14-1] The metal member assembly according to [13] or [14], wherein the material of the metal member is gold, silver, copper, platinum, palladium, or an alloy of these metals. Production method.
[14-2] [13], [14], [14-], wherein the heating temperature is 70 ° C. or more and 400 ° C. or less, and the atmospheric gas during the heating and sintering is an oxidizing gas containing oxygen. [1] The method for producing a metal member assembly according to any one of [1].
[15] The metal member assembly according to any one of [13], [14], [14-1], and [14-2], wherein the metal member assembly is an electronic component. Production method. Is achieved.

According to the method for evaluating the heat-sinterability of the organic-coated metal particles of the present invention, without using the complicated method of evaluating the heat-sinterability after mixing the organic-coated metal particles with a volatile dispersion medium to form a metal paste. In addition, the heat-sinterability of organic-coated metal particles can be evaluated easily, quickly and easily.

According to the method for producing a heat-sinterable metal paste of the present invention, organic coated metal particles having good heat-sinterability are selected by the method for evaluating heat-sinterability of the present invention, and this is mixed with a volatile dispersion medium. Since it is made into a paste, a heat-sinterable metal paste having excellent heat-sinterability can be produced accurately and efficiently.

Since the manufacturing method of the metal member assembly of the present invention manufactures a heat-sinterable metal paste by the manufacturing method of the heat-sinterable metal paste of the present invention and uses this to bond the metal members, Metal members are firmly bonded to each other, and a metal member bonded body excellent in bondability can be accurately and efficiently manufactured.

It is a top view of the test body A for the shear bond strength measurement of the metal member assembly in the examples. The heat-sinterable metal paste 2 is printed on the silver substrate 1 with a metal mask, and after mounting the silver chip 3, the metal particles are heated to sinter, and the shear bond strength between the silver substrate 1 and the silver chip 3 Is to measure. It is the XX sectional view taken on the line in FIG. It is a chart figure of the thermogravimetric analysis of the stearic acid itself of the reference example 1. 2 is a chart of thermogravimetric analysis of oleic acid itself of Reference Example 2. FIG. 2 is a chart of thermogravimetric analysis of stearic acid covering the surface of flaky silver particles of Example 1. FIG. 3 is a chart of thermogravimetric analysis of oleic acid covering the surface of spherical silver particles of Example 3. FIG. It is a chart figure of the thermogravimetric analysis of the oleic acid which has coat | covered the surface of the granular copper particle of Example 4. FIG. 6 is a chart of thermogravimetric analysis of stearic acid coating the surface of flaky nickel particles of Example 5. FIG.

The method for evaluating the heat-sinterability of the organic-coated metal particles according to the present invention is a method for evaluating the heat-sinterability of the organic-coated metal particles by thermal analysis. When the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particle is lower than the thermal decomposition peak temperature (2) of the organic substance itself, subjected to thermal analysis in an air stream, the organic substance-coated metal particle When the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is determined to be excellent in heat sinterability, and the organic substance is more than or equal to the thermal decomposition peak temperature (2) of the organic substance itself, It is determined that the heat-sinterability of the coated metal particles is inferior.

The above-mentioned evaluation method for the heat-sinterability of the organic-coated metal particles is that when the pyrolysis peak temperature (1) is 2 ° C. or more lower than the pyrolysis peak temperature (2), the heat-sinterability of the organic-coated metal particles is When it is determined that the pyrolysis peak temperature (1) is 2 ° C. or more higher than the pyrolysis peak temperature (2), it is preferable to determine that the heat-sinterability of the organic-coated metal particles is inferior. .
The above-mentioned evaluation method for the heat-sinterability of the organic-coated metal particles is that when the pyrolysis peak temperature (1) is 5 ° C. or more lower than the pyrolysis peak temperature (2), the heat-sinterability of the organic-coated metal particles is It is determined that the thermal decomposition peak temperature (1) is 5 ° C. or more higher than the thermal decomposition peak temperature (2), and it is determined that the heat-sinterability of the organic-coated metal particles is inferior. And

Another method for evaluating the heat-sinterability of organic-coated metal particles according to the present invention is a method for evaluating the heat-sinterability of organic-coated metal particles by thermal analysis. For the thermal analysis, the activation energy in the thermal decomposition reaction of the organic matter calculated from the relationship between the rate of temperature rise in the thermal analysis and the thermal decomposition peak temperature (1) of the organic matter covering the surface of the metal particles is If it is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent, and the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature of the organic material covering the surface of the metal particles ( When the activation energy in the thermal decomposition reaction of the organic substance calculated from the relationship with 1) is 95 kJ / mol or more, it is determined that the heat-sinterability of the organic substance-coated metal particles is inferior.
Hereinafter, a method for evaluating the heat-sinterability of these organic-coated metal particles will be described in detail.

The method for evaluating the heat-sinterability of the two organic-coated metal particles is technically closely related for the following reasons and has common technical features.
In order for the metal particles in the organic material-coated metal particles to sinter, it is necessary that the organic material is thermally decomposed by heating and removed from the organic material-coated metal particles. When the heat-sintering property of the organic material-coated metal particles is excellent, the organic material covering the surface of the organic material-coated metal particles is thermally decomposed at a temperature lower than the thermal decomposition temperature of the organic material itself, and the organic material-coated metal particles Although it is removed, this means that the organic-coated metal particles have an action of promoting the thermal decomposition of the organic material covering the surface. Thermal decomposition is a chemical reaction, and the susceptibility of the chemical reaction can be compared by the size of the activation energy, and the activation energy when the organic-coated metal particles have a catalytic action in the thermal decomposition reaction of the organic substance is the catalytic action. This is smaller than the activation energy in the absence of.
That is, when the pyrolysis peak temperature (1) of the organic substance covering the surface of the organic substance-coated metal particles is lower than the pyrolysis peak temperature (2) of the organic substance itself, the organic substance-coated metal particles are In addition to acting as a catalyst for promoting thermal decomposition, the catalyst promotes a chemical reaction. Therefore, the activation energy in this thermal decomposition is small, specifically less than 95 kJ / mol.

Examples of the material of the metal particles coated with the organic substance include gold, silver, copper, palladium, nickel, tin, aluminum, and alloys of these metals that are solid at room temperature, and further, metal compounds of these metals are included. Illustratively, silver and copper are preferable in terms of thermal conductivity and conductivity, and nickel is also preferable. The silver particles may be partly or entirely silver oxide or silver peroxide on the surface or inside. It is preferable that copper has little copper oxide. The metal particles are usually made of a single material, but may be a mixture of particles made of a plurality of materials.

Metal particles coated with organic matter are metal (for example, copper, nickel, aluminum) particles whose surfaces are plated with these metals (for example, silver), and resins whose surfaces are plated with these metals (for example, silver) (for example, , Epoxy resin, polyethersulfone resin) particles.

The shape of the organic-coated metal particles is not particularly limited, and examples thereof include a spherical shape, a needle shape, a square shape, a dendritic shape, a fiber shape, a flake shape (a piece shape), a granular shape, an irregular shape, and a teardrop shape (JIS Z 2500). reference). Furthermore, an elliptical spherical shape, a spongy shape, a grape shape, a spindle shape, a substantially cubic shape, and the like are exemplified. Among these, spherical shape, granular shape, or flake shape is preferable from the viewpoint of storage stability of the heat-sinterable metal paste of the present invention.
The spherical shape referred to here is a shape that is almost a sphere (see JIS Z2500: 2000). The spherical shape is not necessarily required, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as sphericity or spherical coefficient) is 1.0 to 1. Those in the range of .2 are preferred.
Granular is not an irregular shape but a shape with almost equal dimensions (see JIS Z2500: 2000).
The flake shape (strip shape) is a plate-like shape (see JIS Z2500: 2000) and is also called a scale shape because it is a thin plate shape like a scale. No matter the shape, the particle size distribution is not limited.

The method for producing the organic-coated metal particles is not limited, but is preferably a reduction method or a wet method. Many methods for producing metal particles by the reduction method have been proposed. For example, silver oxide is prepared by adding an aqueous solution of sodium hydroxide to an aqueous solution of silver nitrate, and an aqueous solution of a reducing agent such as formalin is added thereto. An example is a method of producing a silver particle dispersion by reduction, filtering the dispersion, washing the filtration residue if necessary, and drying. At this time, in order to prevent aggregation of the silver particles, for example, a water-repellent organic substance which is a high / intermediate fatty acid or a derivative thereof is added to coat the surface of the silver particles (see Japanese Patent Laid-Open No. 54-121270). As described above, the surface of the organic-coated metal particles is coated with an organic material to prevent surface oxidation and aggregation of the particles during storage after production.

The organic substance covering the surface of the organic-coated metal particles is not particularly limited as long as the heat-sinterability of the metal particles is not hindered, and an alkyl alcohol comprising an aliphatic hydrocarbon group having 5 or less carbon atoms and a hydroxy group An alkylamine composed of an aliphatic hydrocarbon group having 5 or less carbon atoms and an amino group, an alkanethiol composed of an aliphatic hydrocarbon group having 5 or less carbon atoms and a sulfanyl group, an aliphatic hydrocarbon group and a hydroxy group. 2 or more alkane polyols, hydrophilic organic substances such as lower fatty acids composed of aliphatic hydrocarbon groups having 5 or less carbon atoms and carboxyl groups; high and intermediate fatty acids and their water-repellent derivatives, fats having 6 or more carbon atoms An alkyl alcohol composed of an aromatic hydrocarbon group and a hydroxy group, an alkylamine composed of an aliphatic hydrocarbon group having 6 or more carbon atoms and an amino group, Illustrative are water-repellent organic substances such as alkanethiols composed of aliphatic hydrocarbon groups having 6 or more elemental atoms and sulfanyl groups, but water-repellent organic substances having excellent storage stability at room temperature of organic-coated metal particles are preferred. . Water repellency is also called hydrophobicity.

The water-repellent organic substance is more preferably a high / intermediate fatty acid or a water-repellent derivative thereof. Examples of the derivatives of high / intermediate fatty acids include high / intermediate fatty acid metal salts (excluding alkali metal salts), high / intermediate fatty acid amides, and high / intermediate fatty acid esters. High and intermediate fatty acids are particularly preferred in terms of coating effect and treatment effect.

A higher fatty acid is a fatty acid having 15 or more carbon atoms, such as pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid (stearic acid), 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), eicosanoic acid ( Linear saturated fatty acids such as arachidic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), hexacosanoic acid (serotic acid), octacosanoic acid (montanic acid); 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2- Examples include branched saturated fatty acids such as heptyldodecanoic acid and isostearic acid; unsaturated fatty acids such as palmitoleic acid, oleic acid, isooleic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid, gadrenic acid, erucic acid, and ceracolic acid The

Intermediate fatty acids are fatty acids having 6 to 14 carbon atoms, such as hexanoic acid (caproic acid), heptanoic acid, octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), undecanoic acid, Linear saturated fatty acids such as dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid); isohexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, 2-propylheptanoic acid, isodecanoic acid, Illustrative examples include branched saturated fatty acids such as isoundecanoic acid, 2-butyloctanoic acid, isododecanoic acid and isotridecanoic acid; and unsaturated fatty acids such as 10-undecenoic acid.

The amount of the organic substance covering the surface of the organic-coated metal particles varies depending on the average particle diameter, specific surface area, shape, specific gravity, etc. of the metal particles, but is preferably 0.01 to 10% by weight of the metal particles, 0.1 More preferred is ˜2% by weight. This is because if the amount is too small, the organic-coated metal particles tend to aggregate and the storage stability is lowered, and if too much, the heat-sinterability of the metal particles is lowered.

The amount of the organic substance covering the surface of the organic substance-coated metal particle can be measured by a usual method. A method of measuring weight loss by heating to a temperature at which organic substances can volatilize (for example, near or above the boiling point), heating carbon particles in an oxygen stream, and carbon in organic substances adhering to the metal particles to carbon dioxide Instead, a method of quantitatively analyzing carbon dioxide gas by infrared absorption spectroscopy is exemplified.

In order for the organic material-coated metal particles to be sintered by heating, it is necessary to remove the organic material covering the surface. On the other hand, in order to stably prevent oxidation and aggregation of the metal particles for a long period of time, the organic substance preferably has a coordinate bond with the surface of the metal particles (see JP-A-2007-83288).

When the organic material-coated metal particles are heated, the organic material covering the surface is removed, and the metal particles are sintered together.
At this time, in particular, the organic substance (monolayer organic substance directly in contact with the metal surface) coated directly in contact with the metal particle surface is not simply attached to the metal surface but is bonded to the metal particle surface. Therefore, it is difficult to volatilize and remove. For example, when the temperature of organic coated metal particles is raised from room temperature, the organic material covering the surface of the metal particles is first volatilized mainly in excess (except for monolayer organic materials that are in direct contact with the metal surface). However, the organic substance in the monomolecular layer directly in contact with the metal particle surface is in a bonded state with the metal particle surface, so it is not removed by volatilization, but is oxidized and decomposed by oxygen and heat in the atmosphere. Can be removed. At this time, since the decomposition reaction due to oxidation is an exothermic reaction, the temperature of the thermal decomposition can be measured by thermal analysis, and the exothermic peak temperature can be set to the temperature at which the organic matter is removed from the metal surface. Note that, at this exothermic peak temperature, organic substances on the surface of the metal particles that hindered the sintering of the metal particles are removed, so that the metal particles are also sintered at the same time. For this reason, the exothermic peak in the method for evaluating the heat sinterability by thermal analysis may include a contribution due to heat generation or endotherm accompanying the sintering of the metal particles.

Examples of such thermal analysis include differential thermal analysis (DTA) and differential scanning calorimetry (DSC), but the apparatus is simple and the pyrolysis gas generated from the sample has little influence on the sensor of the analyzer. Differential thermal analysis is preferred.

In the differential thermal analysis method, the temperature is raised from room temperature at a constant rate of temperature, and the temperature generated between one reference and the other sample due to the electromotive force of the thermocouples installed in the two sample holders. A difference is detected, and an exothermic reaction or an endothermic reaction is detected as a differential heat curve, and can be measured as an exothermic peak when the organic substance covering the surface of the organic substance-coated metal particles is thermally decomposed. At this time, if thermogravimetric analysis (TGA) is performed at the same time, the degree of organic matter removal can be confirmed in the form of weight loss of the organic matter, and therefore differential thermothermal gravimetric simultaneous analysis in which differential thermal analysis and thermogravimetric analysis are performed simultaneously is preferable. Many such measuring devices are commercially available. For example, the DTG-60A differential thermal thermogravimetric simultaneous measurement device manufactured by Shimadzu Corporation can be used in combination with an autosampler, so it is possible to continuously evaluate organic-coated metal particles, and heat sinterability from many metal particles. It is possible to efficiently select metal particles that are superior to the above.

In the differential scanning calorimetry method, the temperature is raised from room temperature at a constant rate of heating, and is generated between one reference and the other sample due to the electromotive force of thermocouples installed in two sample holders. The temperature difference is detected as calorific value, and the exothermic reaction and endothermic reaction are detected as a differential scanning calorimetric curve. It can be measured as an exothermic peak when the organic matter covering the surface of the organic matter-coated metal particles is thermally decomposed. it can. Many such measuring apparatuses are commercially available, and examples include a differential scanning calorimeter manufactured by Perkin Elmer and a differential scanning calorimeter manufactured by Seiko Electronics Corporation.

Thus, both differential thermal analysis and differential scanning calorimetry are common in that they detect the temperature difference between the reference and the sample. Therefore, the pyrolysis peak temperature in the present invention is different depending on the sensitivity of each device. Is basically the same except for.

In the case of differential thermal analysis (DTA), the organic matter covering the surface of the organic-coated metal particles reaches a certain temperature unique to the metal particles when the organic-coated metal particles are heated from room temperature in air. At that time, a thermal decomposition reaction due to oxidation occurs, and the amount of organic matter rapidly becomes zero by generating heat at a stretch. At this time, the differential heat (DTA) curve in the differential thermal analysis forms a peak on the exothermic side, and the temperature at this time is the thermal decomposition peak temperature (1) of the organic matter.
This thermal decomposition peak temperature appears on the exothermic side because thermal decomposition due to oxidation of organic substances is an exothermic reaction called combustion.

In the case of differential scanning calorimetry (DSC), the organic matter covering the surface of the organic-coated metal particles reaches a certain temperature unique to the metal particles when the organic-coated metal particles are heated from room temperature in air. At that time, a thermal decomposition reaction due to oxidation takes place and heat is generated at once, and the amount of organic matter rapidly becomes zero. At this time, the differential scanning calorimetry (DSC) curve in the differential scanning calorimetry analysis forms a peak on the exothermic side, and the temperature at this time is the thermal decomposition peak temperature (1) of the organic matter.
This thermal decomposition peak temperature appears on the exothermic side because thermal decomposition due to oxidation of organic substances is an exothermic reaction called combustion.

The pyrolysis peak temperature (1) of the organic substance covering the surface of the organic-coated metal particles measured in this way should be essentially the same as the pyrolysis peak temperature (2) of the organic substance measured in the same manner. However, when the organic-coated metal particles are excellent in heat sinterability, the metal particles themselves promote the thermal decomposition of the organic material covering the surface, so that the thermal decomposition peak temperature (1) is lowered. As a result, the pyrolysis peak temperature (1) is lower than the pyrolysis peak temperature (2) of the organic substance itself.
On the other hand, when the heat-sinterability of the organic-coated metal particles is inferior, the thermal decomposition peak temperature (1) of the organic material covering the surface of the organic-coated metal particles is the thermal decomposition peak temperature (2) of the organic material itself. The same or higher. That is, it becomes equal or better.

In any of the above cases, the temperature difference between the pyrolysis peak temperature (1) of the organic substance covering the surface of the organic-coated metal particles and the pyrolysis peak temperature (2) of the organic substance itself is preferably 2 ° C. or more. When it is preferably 5 ° C. or higher, the determination of the heat-sinterability of the organic-coated metal particles becomes easy.
The pyrolysis peak temperature of the organic substance itself for coating the heat-sinterable metal particles, and the pyrolysis peak temperature of the organic substance covering the surface of the heat-sinterable metal particles are usually 100 to 330 ° C. Therefore, this determination method is useful when the thermal decomposition peak temperature is usually 100 to 330 ° C., but is not limited to this temperature range.

As described above, if the pyrolysis peak temperature (1) of the organic substance covering the surface of the organic substance-coated metal particles is lower than the pyrolysis peak temperature (2) of the organic substance itself, the heat sinterability of the metal particles is excellent. Can be judged. If the organic-coated metal particles are excellent in heat-sinterability, sintering is possible even at a lower temperature. Therefore, the pyrolysis peak temperature (1) of the organic material covering the surface of the organic-coated metal particles is the heat of the organic material itself. It is preferably 2 ° C. or more lower than the decomposition peak temperature (2), more preferably 5 ° C. or more.

When the evaluation is “excellent”, the organic-coated metal particles evaluated by the heat sinterability evaluation method of the present invention have good sinterability regardless of the heat sintering temperature, and the evaluation is “poor”. ", The actual sinterability is poor regardless of the heating and sintering temperature. In other words, when it is determined as “excellent” by the evaluation method for heat sinterability of the present invention, the actual heating temperature is higher than the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles. Needless to say, the heat-sinterability is excellent even when the temperature is lower than the thermal decomposition peak temperature (1). Further, when it is determined as “inferior” by the heat sinterability evaluation method of the present invention, the actual heating temperature may be higher than the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles. Heat sinterability remains poor.

When the metal particles in the organic material-coated metal particles lower the thermal decomposition temperature of the organic material covering the surface, the organic material-coated metal particles have a function as a catalyst for promoting the thermal decomposition of the organic material. means.
In order to determine that the metal particles are excellent in heat sinterability in the heat sinterability evaluation method of the present invention, activation in the pyrolysis reaction of the organic material covering the surface of the organic material-coated metal particles The energy needs to be low, specifically less than 95 kJ / mol. When the activation energy is 95 kJ / mol or more, it is determined that the heat sinterability of the metal particles is inferior.
This activation energy is derived from the Kissinger equation derived from the assumption that the reaction rate of the thermal decomposition reaction is a primary reaction in the proportion of the amount of unreacted substances. It can be easily determined by measuring the thermal decomposition peak temperature (1) of the organic substance covering the surface.

A specific method for measuring the activation energy is, for example, as follows. In the case of differential thermal analysis (DTA), using an apparatus for simultaneous differential thermothermal gravimetry, organic-coated metal particles are heated at a rate of 1 ° C./min, 5 ° C./min, 10 ° C./min, 50 ° C. in an air stream. The temperature is raised from 23 ° C. to 400 ° C. per minute, and the relationship between each heating rate (Φ, unit K / s) and the exothermic peak temperature (T, unit K) appearing in the DTA curve during the temperature rising is measured. . Next, Kissinnger's formula was applied, plotted on a graph with 1 / T on the horizontal axis and ln (Φ / RT ² ) on the vertical axis, and the slope of the obtained straight line was determined as -E / R, and the activity The conversion energy (E, unit kJ / mol) is calculated. Here, R is a gas constant.

In the case of differential scanning calorimetry (DSC), using a differential scanning calorimeter, the organic coated metal particles are heated at a rate of 1 ° C./min, 5 ° C./min, 10 ° C./min, 50 ° C./min in an air stream. The temperature is raised from 23 ° C. to 400 ° C. per minute, and the relationship between each heating rate (Φ, unit K / s) and the exothermic peak temperature (T, unit K) appearing in the DSC curve during the temperature increase is measured. Next, Kissinnger's formula was applied, plotted on a graph with 1 / T on the horizontal axis and ln (Φ / RT ² ) on the vertical axis, and the slope of the obtained straight line was determined as -E / R, and the activity The conversion energy (E, unit kJ / mol) is calculated. Here, R is a gas constant.

In the method for producing a heat-sinterable metal paste in the present invention, each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the thermal decomposition peak of the organic substance covering the surface of the metal particles. If the temperature (1) is lower than the pyrolysis peak temperature (2) of the organic substance itself, it is determined that the heat-sintering property of the organic substance-coated metal particles is excellent, and the heat of the organic substance covering the surface of the metal particles is determined. When the decomposition peak temperature (1) is equal to or higher than the thermal decomposition peak temperature (2) of the organic substance itself, it is determined that the heat-sintering property of the organic-coated metal particles is poor, and then the heat-sintering property is excellent. The organic coated metal particles thus determined are mixed with a volatile dispersion medium to form a paste.

In another method for producing a heat-sinterable metal paste according to the present invention, organic-coated metal particles are subjected to thermal analysis in an air stream, and the temperature rise rate in the thermal analysis and the surface of the metal particles are coated. When the activation energy in the thermal decomposition reaction of the organic substance calculated from the relationship with the thermal decomposition peak temperature (1) of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic substance-coated metal particles is excellent. And the activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol. If it is above, it is determined that the heat-sinterability of the organic-coated metal particles is poor, and then the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste. And wherein the door.

The material and shape of the organic-coated metal particles, the type and amount of the organic material covering the surface of the metal particles, and the method for determining the heat-sinterability of the metal particles are the method for evaluating the heat-sinterability of organic-coated metal particles Is as described above.

There are many varieties of organic-coated metal particles depending on the type of metal, the method for producing the metal particles, the average particle size of the metal particles, the shape of the metal particles, the type of organic material that coats the surface of the metal particles, etc. There are few metal particles with excellent sinterability, and sintering is possible even at a temperature of about 70 ° C. to 250 ° C., and metal particles capable of firmly joining metal members are extremely rare.
In order to select metal particles having excellent heat sinterability from a large number of organic-coated metal particles, in the conventional method, the metal particles are mixed with a volatile dispersion medium one by one to produce a metal paste, Although it is not easy to evaluate by judging the heat sinterability by heating the metal paste, according to the method for evaluating the heat sinterability of the organic-coated metal particles of the present invention, Therefore, it is possible to easily, quickly and easily select metal particles having excellent heat sinterability, so that a heat sinterable metal paste having excellent heat sinterability can be accurately and efficiently manufactured.

The average particle size of the organic-coated metal particles in the present invention is preferably from 0.1 μm to 50 μm. This average particle diameter is an average particle diameter (median diameter D50) of primary particles obtained by a laser diffraction / scattering particle size distribution measurement method. If the average particle diameter exceeds 50 μm, it becomes difficult to dispense (discharge) from a syringe having a needle having a small diameter after preparing a heat-sinterable metal paste. From this point, the average particle diameter is small. Is preferred.
For this reason, it is preferable that an average particle diameter is 20 micrometers or less, and it is especially preferable that it is 10 micrometers or less. The lower limit of the average particle diameter is not limited, but so-called metal nanoparticles having an average particle diameter of less than 0.1 μm are very expensive to manufacture and lose versatility, so the average particle diameter is 0.1 μm or more. It is preferable. From this viewpoint, the average particle size is more preferably 0.2 μm or more, and more preferably 0.7 μm or more.
The median diameter D50 is also referred to as a laser diffraction method 50% particle size (see Japanese Patent Application Laid-Open No. 2003-55701) or a volume cumulative particle size D50 (see Japanese Patent Application Laid-Open No. 2007-84860).

The laser diffraction / scattering particle size distribution measurement method is a method of irradiating a metal beam with a laser beam and measuring the intensity of the diffracted light or scattered light emitted in various directions depending on the size of the metal particle. This is a general-purpose measurement method for determining the particle size of particles. Many measuring devices are commercially available (for example, a laser diffraction particle size distribution measuring device SALD manufactured by Shimadzu Corporation, a laser diffraction scattering particle size distribution measuring device Microtrac manufactured by Nikkiso Co., Ltd.), and using these, the average particle size can be easily obtained. The diameter (median diameter D50) can be measured. In the case where the aggregation of the metal particles is strong, it is preferably measured after being dispersed in a primary particle state by a homogenizer.

The surface of the organic-coated metal particles only needs to be covered with more than half of the organic material, but it is preferable that the entire surface is covered. In order to coat the surface of the metal particles with an organic material, a method of coating the surface of the metal particles by introducing an organic material during the production of the metal particles, after the metal particles are produced, the metal particles are immersed in an organic solution. Thereafter, a method of taking out and drying the metal particles, and a method of spraying and drying an organic solution after producing the metal particles are exemplified.

The volatile dispersion medium is blended in order to form organic powder-coated metal particles in a paste form, and the paste form includes a cream form or a slurry form.
In order to heat the heat-sinterable metal paste thus prepared to sinter the metal particles, the dispersion medium needs to be volatile rather than non-volatile. This is because if the dispersion medium is volatilized when the metal particles are sintered, the metal particles are sintered and easily used as a bonding agent and a wiring material. The boiling point of the volatile dispersion medium is preferably lower than the melting point of the organic-coated metal particles, and is preferably 60 ° C to 300 ° C. This is because if the boiling point is less than 60 ° C., the solvent easily evaporates during the operation of preparing the heat-sinterable metal paste, and if the boiling point exceeds 300 ° C., the volatile dispersion medium may remain even after heating. .

Such volatile dispersion media include volatile hydrocarbon compounds composed of carbon atoms and hydrogen atoms, volatile organic compounds composed of carbon atoms, hydrogen atoms and oxygen atoms, volatile organic compounds composed of carbon atoms, hydrogen atoms and nitrogen atoms. A compound, a volatile organic compound composed of a carbon atom, a hydrogen atom, an oxygen atom and a nitrogen atom, a mixture of a hydrophilic volatile organic compound of the volatile organic compounds and water, and the like are selected. These are all liquid at room temperature.
The water is preferably pure water, and its electric conductivity is preferably 100 μS / cm or less, more preferably 10 μS / cm or less. The pure water production method may be a normal method, and examples include an ion exchange method, a reverse osmosis method, and a distillation method.

Specific examples of volatile organic compounds composed of carbon, hydrogen and oxygen include volatile compounds such as ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol and decyl alcohol. Monohydric alcohol: ethylene glycol monomethyl ether (methyl cellosolve, methyl carbitol), ethylene glycol monoethyl ether (emethyl cellosolve, ethyl carbitol), ethylene glycol monopropyl ether (propyl cellosolve, propyl carbitol), ethylene glycol monobutyl ether (Butyl cellosolve, butyl carbitol), propylene glycol monomethyl ether, methyl methoxybutanol, diethylene glycol Volatile monohydric alcohols and volatile dihydric alcohols having ether bonds such as recall and dipropylene glycol; Volatile terpene alcohols such as terpineol, linalool and geraniol; Volatile aralkyl alcohols such as benzyl alcohol and 2-phenylethyl alcohol And volatile polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol and glycerin are exemplified.

Furthermore, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexene-1- ON), volatile aliphatic ketones such as dibutylketone (2,6-dimethyl-4-heptanone); ethyl acetate (ethyl acetate), butyl acetate, acetoxyethane, methyl butyrate, methyl hexanoate, methyl octoate, decane Volatile aliphatic carboxylic acid esters such as methyl acid, methyl cellosolve acetate, propylene glycol monomethyl ether acetate; tetrahydrofuran, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene Glycol dibutyl ether, propylene glycol dimethyl ether, volatile aliphatic ethers such as ethoxyethyl ether, and the like.

As volatile hydrocarbon compounds composed of carbon atoms and hydrogen atoms, volatile aliphatic hydrocarbons such as lower n-paraffins and lower isoparaffins; volatile terpene hydrocarbons such as limonene and α-terpinene; volatilization of toluene, xylene and the like An aromatic hydrocarbon is exemplified.

Examples of volatile organic compounds composed of carbon atoms, hydrogen atoms and nitrogen atoms include volatile alkyl nitriles such as acetonitrile and propionitrile.
Examples of volatile organic compounds composed of carbon atoms, hydrogen atoms, oxygen atoms and nitrogen atoms include volatile carboxylic acid amides such as acetamide and N, N-dimethylformamide. Other examples include low molecular weight volatile silicone oils and volatile organic modified silicone oils.

The blending amount of the volatile dispersion medium is an amount sufficient to make the organic-coated metal particles into a paste at room temperature. The amount sufficient to form a paste varies depending on the material, particle size, surface area, shape, specific gravity, type of volatile dispersion medium, viscosity, specific gravity, etc. of the organic-coated metal particles. 3 to 30 parts by weight per 100 parts by weight of the coated metal particles.
The heat-sinterable metal paste used in the present invention includes metal particles other than organic-coated metal particles, non-metallic powders, metal compounds, metal complexes, thixotropic agents, and colorants, unless they are contrary to the object of the present invention. Such additives may be contained in a small amount or a trace amount.

Specifically, the method for producing the heat-sinterable metal paste of the present invention includes organic-coated metal particles excellent in heat-sinterability and volatilization selected by the method for evaluating the heat-sinterability of organic-coated metal particles of the present invention. This is because the conductive dispersion medium is charged into a mixer and mixed with stirring until a uniform paste is obtained.

The heat-sinterable metal paste produced by the method for producing a heat-sinterable metal paste of the present invention is a mixture of organic-coated metal particles and a volatile dispersion medium, and is paste-like at room temperature. The paste form includes a cream form and a slurry form. By making it into a paste, it can be ejected from a cylinder or nozzle into dots or fine lines, and printing with a metal mask is easy. Although the thickness of the heat-sinterable metal paste in the case of interposing between a plurality of metal members is not limited, it is usually 5 μm or more and 1000 μm or less.

The heat-sinterable metal paste produced by the heat-sinterable metal paste production method of the present invention is interposed between metal members and heated to a temperature equal to or higher than the sintering temperature of the organic-coated metal particles. The volatile dispersion medium is volatilized and the metal particles are sintered to form a porous sintered product having excellent conductivity and thermal conductivity, and metal members can be joined to each other.

At this time, the volatile dispersion medium is volatilized, and then the metal particles may be sintered together, or the metal particles may be sintered together with the volatilization of the volatile dispersion medium. In particular, when the metal particles are silver particles or copper particles, silver or copper inherently has high strength and extremely high electrical and thermal conductivity, so that sintered products of silver particles or copper particles also have high strength. It has extremely high electrical and thermal conductivity.

The heating temperature at this time may be a temperature at which the volatile dispersion medium is volatilized and the organic-coated metal particles can be sintered, and is usually 70 ° C. or higher, and more preferably 150 ° C. or higher. However, if the temperature exceeds 400 ° C., the volatile dispersion medium may evaporate suddenly. Therefore, the temperature must be 400 ° C. or less, preferably 350 ° C. or less, more preferably 300 ° C. or less. .

The heat-sintered product of organic-coated metal particles has many fine pores, voids, and continuous pores, that is, is porous, and the porosity is usually 5 to 50% by area. It is preferable that it is 1 to 50 area% during pressure sintering. This is because if the porosity is less than the lower limit, the Young's modulus of the sintered product is increased and the stress relaxation property against thermal shock is lowered. Moreover, if the porosity exceeds 50 area%, even if the strength of the heat-sintered material is lowered, it becomes brittle and the adhesive strength is lowered.
In addition, the normal measuring method can be utilized for the measuring method of the porosity. For example, a cross-section of a sintered body is photographed with an electron microscope, image analysis software is used to determine the area ratio between the metal part and the space part, and the photograph taken with the electron microscope is printed on homogeneous paper, etc. An example is a method in which a portion and a space portion are separated with scissors or the like to measure the weight of each portion and the weight ratio is set to area%.

Moreover, since the heat-sintered material of organic-coated metal particles is made of a solid metal, it has excellent conductivity and thermal conductivity. In particular, when the metal of the organic-coated metal particles is silver, it is preferable that the volume resistivity is not more than 5 × 10 ^-5 Ω · cm, more preferably not more than 1 × 10 ^-5 Ω · cm . The thermal conductivity is preferably 20 W / m · K or more, and more preferably 30 W / m · K or more. When the metal in the organic-coated metal particles is copper, the volume resistivity is preferably 1 × 10 ⁻² Ω · cm or less, and more preferably 1 × 10 ⁻³ Ω · cm or less. The thermal conductivity is preferably 20 W / m · K or more, and more preferably 30 W / m · K or more.

In the method for producing a metal member assembly of the present invention, each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature of the organic substance covering the surface of the metal particles. When (1) is lower than the thermal decomposition peak temperature (2) of the organic substance itself, it is determined that the organic material-coated metal particles are excellent in heat-sinterability, and the organic substance covering the surface of the metal particles is thermally decomposed. When the peak temperature (1) is equal to or higher than the pyrolysis peak temperature (2) of the organic matter itself, it was determined that the heat-sinterability of the organic-coated metal particles was poor and the heat-sinterability was determined to be excellent. Organic coated metal particles are mixed with a volatile dispersion medium to make a paste to prepare a heat-sinterable metal paste, and then the heat-sinterable metal paste is interposed between a plurality of metal members and heat-sintered. Heating at a temperature above the sinterable temperature of porous metal That. A plurality of metal members are joined together by a porous sintered product produced by sintering the heat-sinterable metals to produce a metal member joined body.

Another method for producing a metal member assembly according to the present invention is to provide organic matter-coated metal particles for thermal analysis in an air stream and to coat the surface of the metal particles with a temperature increase rate in the thermal analysis. When the activation energy in the thermal decomposition reaction of the organic substance calculated from the relationship with the thermal decomposition peak temperature (1) of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent. The activation energy in the thermal decomposition reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more Is determined to be poor in heat-sinterability of the organic-coated metal particles, and the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste and heat-sintered. Metal Prepared paste, then the heating sintered metal paste is interposed between the plurality of metallic members, characterized by heating by heat sintering metal sinterable temperature more. A plurality of metal members are joined together by a porous sintered product produced by sintering the heat-sinterable metals to produce a metal member joined body.

The material and shape of the organic-coated metal particles, the type and amount of the organic material covering the surface of the metal particles, and the method for determining the heat-sinterability of the metal particles are the method for evaluating the heat-sinterability of the organic-coated metal particles. Is as described above.

In the metal member used in the method for producing a metal member assembly of the present invention, the applied heat-sinterable metal paste is heated to volatilize the volatile dispersion medium in the composition, and the metal particles are It is an object to be joined that is sintered and joined. Examples of the material of the metal member include gold, silver, copper, platinum, palladium, nickel, tin, aluminum, and alloys of these metals. Among these, gold, silver, copper, platinum, palladium, or an alloy of these metals is preferable in terms of conductivity and bondability. The metal member may be plated with the metal. Examples of the metal member include a lead frame, a printed circuit board, a semiconductor chip, and a heat sink, all or part of which is made of metal.

The temperature above the temperature at which the heat-sinterable metal particles can be sintered is preferably 70 ° C. or higher and 400 ° C. or lower. The atmosphere gas at the time of heating and sintering is exemplified by an oxidizing gas, a reducing gas, and an inert gas, but is preferably an oxidizing gas containing oxygen. Examples of such oxidizing gas include air and a mixed gas of oxygen gas and inert gas such as nitrogen gas. In the case of a heat-sinterable metal particle or metal member that oxidizes in an oxidizing gas, it can be reduced by heating in a reducing gas after sintering in the oxidizing gas.

The reducing gas is exemplified by hydrogen gas, but a mixed gas of hydrogen gas and inert gas that is easy to handle is preferable. The ratio of the reducing gas to the inert gas is not limited, but when the reducing gas is hydrogen gas, it is preferably 1 to 40% by volume, and particularly, the hydrogen gas is 5 to 25% by volume and the nitrogen gas 95 to 95%. A reducing gas called forming gas composed of 75% by volume is preferred.

In the method for producing a metal member assembly of the present invention, pressure or ultrasonic vibration may be applied during the heat sintering of the heat-sinterable metal paste interposed between the metal members.

Although the minimum of the pressure at the time of pressurization is not limited, It is preferable that it is 0.001 MPa or more, and it is more preferable that it is 0.01 MPa or more. The upper limit is the maximum pressure at which the metal member to be joined is not destroyed.

The frequency of ultrasonic vibration is 2 kHz or more, preferably 10 kHz or more, and the upper limit is not particularly limited, but is about 500 kHz due to the capability of the apparatus. The amplitude of the ultrasonic vibration is preferably 0.1 to 40 μm, more preferably 0.3 to 20 μm, and particularly preferably 0.5 to 12 μm. At this time, pressure may be applied, and the degree of the pressure is as described above.

In the metal member assembly manufactured using the method for manufacturing a metal member assembly of the present invention, a plurality of metal members are firmly bonded to each other by a sintered product of heat-sinterable metal particles.

The shear bond strength between the plurality of metal members in the metal member assembly manufactured using the method for manufacturing a metal member assembly of the present invention is preferably 5 MPa or more, more preferably 10 MPa or more. It is.

In the heat-sinterable metal paste used in the method for producing a metal member assembly of the present invention, the volatile dispersion medium is volatilized by heating, and the heat-sinterable metal particles are sintered. When this is used for joining between a plurality of metal members, the metal member that has been in contact, such as a gold-plated substrate, silver substrate, silver-plated metal substrate, copper substrate, aluminum substrate, nickel-plated substrate, tin-plated metal substrate, etc. Adhering firmly to metal substrates and strongly adhering to metal parts such as electrodes on electrically insulating substrates, it is useful for joining metal substrates and electronic parts, electronic devices, electric components, electric devices etc. with metal parts It is.

Such bonding includes bonding of chip parts such as capacitors and resistors and circuit boards, bonding of semiconductor chips such as diodes, memories, ICs, and CPUs to lead frames or circuit boards, and high-heat generation CPU chips and cooling plates. Are exemplified. Therefore, in the method for producing a metal member assembly according to the present invention, the metal member assembly is preferably an electronic component, an electronic device, an electrical component, an electrical device, or the like having a metal substrate or a metal portion.

Examples of the present invention will be given below. In the examples, “parts” means “parts by weight”. The average particle size of organic coated metal particles, the amount of organic material covering the surface of organic coated metal particles, the thermal decomposition peak temperature of the organic material coating the surface of organic coated metal particles, and the surface of organic coated metal particles Activation energy of the pyrolysis reaction of the organic matter, the pyrolysis peak temperature of the organic matter itself, the porosity, volume resistivity and thermal conductivity of the porous sintered product which is a sintered product of the heat-sinterable metal paste The shear bond strength of the metal member assembly was measured as follows. In addition, the measurement temperature in case there is no description in particular is 23 degreeC.

[Average particle diameter of organic coated metal particles]
The average particle diameter of the organic-coated metal particles is the average particle diameter (median diameter D50) of primary particles obtained by a laser diffraction / scattering particle size distribution measuring method using a laser diffraction particle size distribution measuring device SALD manufactured by Shimadzu Corporation. is there.
[Amount of organic material covering the surface of organic-coated metal particles]
The amount of organic material covering the surface of organic coated metal particles is determined by heating the organic coated metal particles in an oxygen stream to change the carbon in the organic material adhering to the metal particles to carbon dioxide, and absorbing carbon dioxide by infrared radiation. According to the method of quantitative analysis by the spectral method.

[Pyrolysis peak temperature of organic substance covering the surface of organic substance-coated metal particles]
Using a differential thermothermal gravimetric simultaneous measurement device (DTG-60AH type, manufactured by Shimadzu Corporation), the organic-coated metal particles were heated from 23 ° C. to 400 ° C. at a temperature rising rate of 5 ° C./min. The exothermic peak temperature appearing in the DTA curve during the warming was taken as the thermal decomposition temperature of the organic substance covering the metal particle surface. At this time, in some examples, thermogravimetric analysis (TGA) was simultaneously performed to obtain a TGA curve.

[Activation energy of thermal decomposition reaction of organic substance covering organic substance-coated metal particle surface]
Using a differential thermothermal gravimetric simultaneous measurement device (DTG-60AH type, manufactured by Shimadzu Corporation), the organic coated metal particles were heated at a rate of 1 ° C./min, 5 ° C./min, 10 ° C./min, 50 ° C. in an air stream. The temperature was increased from 23 ° C. to 400 ° C. at a rate of 1 min / min, and the relationship between each heating rate (Φ, unit K / s) and the exothermic peak temperature (T, unit K) appearing in the DTA curve during the temperature increase was measured. .
Next, Kissinnger's formula was applied, plotted on a graph with 1 / T on the horizontal axis and ln (Φ / RT ² ) on the vertical axis, and the slope of the obtained straight line was determined as -E / R, and the activity The conversion energy (E, unit kJ / mol) was calculated. Here, R is a gas constant.

[Pyrolysis peak temperature of organic substance itself]
Using a differential thermothermal gravimetric simultaneous measurement device (DTG-60AH type, manufactured by Shimadzu Corporation), the organic matter was heated from 23 ° C. to 400 ° C. at a rate of temperature increase of 5 ° C./min in the air stream. The exothermic peak temperature appearing in the DTA curve was defined as the pyrolysis peak temperature of the organic substance itself.

[Porosity of porous sintered product]
A 1 mm thick stainless steel mask having a 15 mm square opening was placed on the polytetrafluoroethylene resin plate, and a heat-sinterable metal paste was applied by printing. This was heated and removed in a hot air circulation oven at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour, and after cooling, it was removed from the polytetrafluoroethylene resin plate and heat-sinterable metal A metal sheet, which is a porous sintered product of particles, was prepared. Take a cross-section of this metal sheet with an electron microscope and use image analysis software (NIH Image, manufactured by the National Institute of Health, USA) to calculate the proportion of the area occupied by the space in the cross-section. ; Area%).
In addition, in the case of copper particles and nickel particles, in which the metal particles are easily oxidized by heating in an air stream, each of the above is heated at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour. In a forming gas stream, which is a mixed gas of 10% by volume of gas and 90% by volume of nitrogen gas, copper was oxidized by heating at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour, respectively. Nickel was reduced.

[Volume resistivity of porous sintered product]
A 1 mm thick stainless steel mask having a 15 mm square opening was placed on the polytetrafluoroethylene resin plate, and a heat-sinterable metal paste was applied by printing. This was heated and removed in a hot air circulation oven at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour, and after cooling, it was removed from the polytetrafluoroethylene resin plate and heat-sinterable metal A metal sheet, which is a porous sintered product of particles, was prepared. The volume resistivity (unit: Ω · cm) of this metal sheet was measured by a method according to JIS K 7194.
When the metal particles are copper particles and nickel particles that are easily oxidized by heating in an air stream, hydrogen gas is heated after heating at 180 ° C. for 2 hours, at 250 ° C. for 1 hour, and at 300 ° C. for 1 hour, respectively. Oxidized copper, oxidized nickel by heating at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour in a forming gas stream which is a mixed gas of 10% by volume and 90% by volume of nitrogen gas, respectively. The process which reduced was performed.

[Thermal conductivity of porous sintered product]
A 2 mm thick stainless steel mask having a 10 mm square opening was placed on the polytetrafluoroethylene resin plate, and a heat-sinterable metal paste was applied by printing. This was heated and removed in a hot air circulation oven at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour, and after cooling, it was removed from the polytetrafluoroethylene resin plate and heat-sinterable metal A metal sheet, which is a porous sintered product of particles, was prepared. The thermal conductivity (unit: W / m · K) of this metal sheet was measured by a laser flash method using a thermal constant measuring device.
When the metal particles are copper particles and nickel particles that are easily oxidized by heating in an air stream, the hydrogen gas 10 is heated after heating at 180 ° C. for 2 hours, 250 ° C. for 1 hour, and 300 ° C. for 1 hour, respectively. By heating at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour in a forming gas stream which is a mixed gas of volume% and nitrogen gas 90 volume%, respectively, oxidized copper and oxidized nickel Processing to reduce.

[Shear bond strength of metal member assembly]
100 μm thick having four openings (2.5 mm × 2.5 mm) at a distance of 10 mm on a silver substrate (silver purity 99.99%) of width 25 mm × length 70 mm × thickness 1.0 mm A heat-sinterable metal paste was printed and applied using a stainless steel mask, and a silver chip (silver purity 99.99%) having a size of 2.5 mm × 2.5 mm × 0.5 mm was mounted thereon. This was joined by heating in a hot air circulation oven at 180 ° C. for 2 hours, 250 ° C. for 1 hour and 300 ° C. for 1 hour, respectively. This metal member joined body was set in an adhesive strength tester, the side surface of the silver chip was pushed at a speed of 23 mm / min, and the load when the joint was sheared was determined as the shear adhesive strength (unit: MPa). .
When the metal particles are copper particles and nickel particles that are easily oxidized by heating in an air stream, hydrogen gas is heated after heating at 180 ° C. for 2 hours, at 250 ° C. for 1 hour, and at 300 ° C. for 1 hour, respectively. In a forming gas stream, which is a mixed gas of 10% by volume and 90% by volume of nitrogen gas, by heating at 180 ° C. for 2 hours, at 250 ° C. for 1 hour and at 300 ° C. for 1 hour, oxidized copper, oxidized The nickel was reduced.

[Reference Example 1]
The thermal decomposition peak temperature of stearic acid (Kanto Chemical Co., Ltd., reagent grade 1) itself, which is a water-repellent organic substance, was measured. The thermal decomposition peak temperature was 254 ° C. The measurement results are shown in FIG.

[Reference Example 2]
The thermal decomposition peak temperature of oleic acid (Kanto Chemical Co., Ltd., reagent grade 1) itself, which is a water-repellent organic substance, was measured. The thermal decomposition peak temperature was 240 ° C. The measurement results are shown in FIG.

[Reference Example 3]
The thermal decomposition peak temperature of lauric acid (Kanto Chemical Co., Ltd., reagent grade 1) itself, which is a water-repellent organic substance, was measured. The thermal decomposition peak temperature was 209 ° C.

[Reference Example 4]
The thermal decomposition peak temperature of stearamide (Kanto Chemical Co., Ltd., reagent grade 1) itself, which is a water-repellent organic substance, was measured. The thermal decomposition peak temperature was 263 ° C.

[Example 1]
Commercially available flaky silver particles having an average particle size of 3.5 μm coated with stearic acid, which is a water-repellent organic substance, and flakes formed by adding stearic acid to granular silver particles produced by the reduction method The thermal decomposition peak temperature of stearic acid was measured for the particles (the amount of stearic acid was 0.4% by weight). At this time, thermogravimetric analysis of stearic acid was simultaneously performed, and FIG. 5 shows a DTA curve and a TGA curve together.
As a result, the thermal decomposition peak temperature of stearic acid on the surface of the silver particles was 203 ° C., which was 51 ° C. lower than 254 ° C. which is the thermal decomposition peak temperature of stearic acid itself measured in Reference Example 1. From this, it was determined that the flaky silver particles coated with stearic acid were excellent in heat sinterability.
The activation energy of the thermal decomposition reaction of stearic acid coating the surface of the flaky silver particles was 71 kJ / mol. From this, it was determined that the flaky silver particles coated with stearic acid were excellent in heat sinterability. The pyrolysis peak temperature and activation energy are shown in Table 1.

By adding 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) as a volatile dispersion medium to 100 parts of the flaky silver particles coated with stearic acid, and uniformly mixing with a spatula A heat-sinterable silver paste was prepared.

For this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered material, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 1. .
This heat-sinterable silver paste was cured by heating to become a porous sintered product excellent in conductivity and thermal conductivity, and the metal member joined body was firmly joined.
From the above results, it was found that this method for evaluating the heat sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of flaky silver particles coated with stearic acid.

[Example 2]
A granular silver particle having an average particle diameter of 0.8 μm and coated with oleic acid, which is a water-repellent organic substance, manufactured according to the reduction method described in the examples of JP-A No. 54-121270. The oleic acid thermal decomposition peak temperature was measured for an oleic acid amount of 0.3% by weight.
As a result, the thermal decomposition peak temperature of oleic acid on the silver particle surface was 227 ° C., which was 13 ° C. lower than 240 ° C., which is the thermal decomposition peak temperature of oleic acid itself measured in Reference Example 2. From this, it was determined that the granular silver particles coated with oleic acid were excellent in heat sinterability.
The activation energy of the thermal decomposition reaction of oleic acid covering the surface of the granular silver particles was measured and found to be 87 kJ / mol. From this, it was determined that the granular silver particles coated with oleic acid were excellent in heat sinterability. The thermal decomposition peak temperature and activation energy are shown in Table 2.

To 100 parts of the granular silver particles coated with oleic acid, 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) is added as a volatile dispersion medium, and heated by uniformly mixing with a spatula. A sinterable silver paste was prepared.

With respect to this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered material, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 2. .
This heat-sinterable silver paste was cured by heating to become a porous sintered product excellent in conductivity and thermal conductivity, and the metal member joined body was firmly joined.
From the above results, it was found that this method for evaluating the heat-sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of granular silver particles coated with oleic acid.

[Example 3]
Spherical (sphericity: 1.07) silver particles produced by the atomization method are dipped in oleic acid, pulled up, washed with methanol and air-dried, and the particle surface is coated with oleic acid, a water-repellent organic substance. The thermal decomposition peak temperature of oleic acid was measured for spherical silver particles having a sphericity of 1.07 (the amount of oleic acid was 0.3% by weight) having a particle size of 1.5 μm. At this time, thermogravimetric analysis of oleic acid was simultaneously performed, and FIG. 6 shows a DTA curve and a TGA curve together.
As a result, the thermal decomposition peak temperature of oleic acid on the surface of the silver particles was 282 ° C., which was 42 ° C. higher than 240 ° C., which is the thermal decomposition peak temperature of oleic acid itself measured in Reference Example 2. From this, it was determined that the spherical silver particles coated with oleic acid were inferior in heat sinterability.
The activation energy of the thermal decomposition reaction of oleic acid covering the surface of the spherical silver particles was measured and found to be 99 kJ / mol. From this, it was determined that the spherical silver particles coated with oleic acid were inferior in heat sinterability. The thermal decomposition peak temperature and activation energy are shown in Table 3.

To 100 parts of the spherical silver particles coated with oleic acid, 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) is added as a volatile dispersion medium, and heated by uniformly mixing with a spatula. A sinterable silver paste was prepared.

For this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered material, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 3. .
This heat-sinterable silver paste was not sufficiently cured even when heated, and the electrical conductivity, thermal conductivity, and joining of the metal member assembly were insufficient.
From the above results, it was found that this method for evaluating the heat-sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of spherical silver particles coated with oleic acid.

[Example 4]
For commercially available copper particles (the amount of oleic acid is 0.8% by weight) produced by a wet method and coated with oleic acid whose surface is coated with water-repellent organic material and having an average particle size of 1.2 μm, oleic acid is used. The pyrolysis peak temperature of was measured.
As a result, the thermal decomposition peak temperature of oleic acid on the copper particle surface was 234 ° C., which was 6 ° C. lower than 240 ° C., which is the thermal decomposition peak temperature of oleic acid itself measured in Reference Example 2. From this, it was determined that the granular copper particles coated with oleic acid were excellent in heat sinterability. The measurement results are shown in FIG.
The activation energy of the thermal decomposition reaction of oleic acid covering the surface of the granular copper particles was measured and found to be 91 kJ / mol. From this, it was determined that the granular copper particles coated with oleic acid were excellent in heat sinterability. The thermal decomposition peak temperature and activation energy are shown in Table 4.

Heat by adding 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) as a volatile dispersion medium to 100 parts of the granular copper particles coated with oleic acid, and mixing uniformly using a spatula. A sinterable copper paste was prepared.

For this heat-sinterable copper paste, the porosity, volume resistivity and thermal conductivity of the porous sintered product, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 4. .
This heat-sinterable copper paste was cured by heating to become a porous sintered product excellent in conductivity and thermal conductivity, and the metal member joined body was firmly joined.
From the above results, it was found that this method for evaluating the heat sinterability of heat-sinterable copper particles is useful for determining the heat-sinterability of granular copper particles coated with oleic acid.

[Example 5]
Commercially available flaky nickel particles having an average particle diameter of 7.5 μm, which is obtained by adding stearic acid to granular nickel particles produced by the carbonyl method and coating the surface with stearic acid which is a water-repellent organic substance. For (the amount of stearic acid is 0.3% by weight), the thermal decomposition peak temperature of stearic acid was measured. The measurement results are shown in FIG.
As a result, the thermal decomposition peak temperature of stearic acid on the nickel particle surface was 279 ° C., which was 25 ° C. higher than 254 ° C. which is the thermal decomposition peak temperature of stearic acid itself measured in Reference Example 2. From this, it was determined that the flaky nickel particles coated with stearic acid had poor heat sinterability.
The activation energy of the thermal decomposition reaction of stearic acid covering the surface of the flaky nickel particles was measured and found to be 97 kJ / mol. From this, it was determined that the flaky nickel particles coated with stearic acid had poor heat sinterability. The thermal decomposition peak temperature and activation energy are shown in Table 5.

By adding 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) as a volatile dispersion medium to 100 parts of the flaky nickel particles coated with stearic acid, and uniformly mixing with a spatula A heat-sinterable nickel paste was prepared.

For this heat-sinterable nickel paste, the porosity, volume resistivity and thermal conductivity of the porous sintered material, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 5. .
This heat-sinterable nickel paste was not sufficiently cured even when heated, and the electrical conductivity, thermal conductivity, and joining of the metal member assembly were insufficient.
From the above results, it was found that this method for evaluating the heat-sinterability of the heat-sinterable nickel particles is useful for determining the heat-sinterability of the flaky nickel particles coated with stearic acid.

[Example 6]
A granular silver particle having an average particle diameter of 0.9 μm (coated with lauric acid, which is a water-repellent organic substance), manufactured according to the reduction method described in the examples of JP-A No. 54-121270. The thermal decomposition peak temperature of lauric acid was measured for a lauric acid amount of 0.2% by weight.
As a result, the thermal decomposition peak temperature of lauric acid on the silver particle surface was 201 ° C., which was 8 ° C. lower than 209 ° C., which is the thermal decomposition peak temperature of lauric acid itself measured in Reference Example 3. From this, it was determined that the granular silver particles coated with lauric acid were excellent in heat sinterability.
The activation energy of the thermal decomposition reaction of lauric acid covering the surface of the granular silver particles was measured and found to be 83 kJ / mol. From this, it was determined that the granular silver particles coated with lauric acid were excellent in heat sinterability. The pyrolysis peak temperature and activation energy are shown in Table 6.

To 100 parts of the granular silver particles coated with lauric acid, 10 parts of dipropylene glycol (manufactured by Kanto Chemical Co., Ltd., reagent grade 1) is added as a volatile dispersion medium, and heated by uniformly mixing with a spatula. A sinterable silver paste was prepared.

For this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered product, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 6. .
This heat-sinterable silver paste was cured by heating to become a porous sintered product excellent in conductivity and thermal conductivity, and the metal member joined body was firmly joined.
From the above results, it was found that this method for evaluating the heat sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of granular silver particles coated with lauric acid.

[Example 7]
The average particle size is obtained by dipping granular silver particles whose surface is not coated with organic matter in lauric acid, pulling them up, washing with methanol, and air drying to coat the surface of particles with water-repellent organic lauric acid. The thermal decomposition peak temperature of lauric acid was measured for granular silver particles (the amount of lauric acid was 0.1% by weight) having a particle size of 1.1 μm.
As a result, the thermal decomposition peak temperature of lauric acid on the silver particle surface was 226 ° C., which was 17 ° C. higher than 209 ° C., which is the thermal decomposition peak temperature of lauric acid itself. From this, it was determined that the granular silver particles coated with lauric acid were poor in heat sinterability.
The activation energy of the thermal decomposition reaction of lauric acid covering the surface of the granular silver particles was measured and found to be 97 kJ / mol. From this, it was determined that the granular silver particles coated with lauric acid had poor heat sinterability. The pyrolysis peak temperature and activation energy are shown in Table 7.

To 100 parts of the granular silver particles coated with lauric acid, 8 parts of isoparaffin which is a hydrocarbon as a volatile dispersion medium (manufactured by Shin Nippon Oil Co., Ltd., trade name isozole, isozole is a registered trademark), A heat-sinterable silver paste was prepared by mixing uniformly using a spatula.

For this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered product, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 7. .
This heat-sinterable silver paste was not sufficiently cured even when heated, and the electrical conductivity, thermal conductivity, and joining of the metal member assembly were insufficient.
From the above results, it was found that this method for evaluating the heat sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of granular silver particles coated with lauric acid.

[Example 8]
An average particle size of 3 coated with stearamide, which is a water-repellent organic material, is formed into flakes by adding stearamide to granular silver particles whose surface is not coated with an organic material manufactured by the reduction method. The thermal decomposition peak temperature of stearamide was measured for commercially available flaky silver particles having a particle size of 0.5 μm (the amount of stearamide is 0.2% by weight).
As a result, the thermal decomposition peak temperature of stearamide on the silver particle surface was 251 ° C., which was 12 ° C. lower than 263 ° C. which is the thermal decomposition peak temperature of stearamide itself. From this, it was determined that the flaky silver particles coated with stearamide had excellent heat sintering properties.
The activation energy of the thermal decomposition reaction of stearamide that coats the surface of the flaky silver particles was measured and found to be 85 kJ / mol. From this, it was determined that the flaky silver particles coated with stearamide had excellent heat sinterability. The thermal decomposition peak temperature and activation energy are shown in Table 8.

To 100 parts of the flaky silver particles coated with stearic acid amide, 10 parts of dipropylene glycol (Kanto Chemical Co., Ltd., reagent grade 1) is added as a volatile dispersion medium, and mixed uniformly using a spatula. Thus, a heat-sinterable silver paste was prepared.

With respect to this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered material, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 8. .
This heat-sinterable silver paste was cured by heating to become a porous sintered product excellent in conductivity and thermal conductivity, and the metal member joined body was firmly joined.
From the above results, it was found that the method for evaluating the heat sinterability of the heat-sinterable silver particles is useful for determining the heat-sinterability of the flaky silver particles coated with stearamide.

[Example 9]
Spherical (sphericity: 1.15) silver particles produced by the atomization method are dipped in oleic acid, pulled up, washed with methanol, air-dried, and the particle surface coated with oleic acid, which is a water-repellent organic substance. The thermal decomposition peak temperature of oleic acid was measured for spherical silver particles having a sphericity of 1.15 (the amount of oleic acid was 0.3% by weight) having a diameter of 1.1 μm.
As a result, the thermal decomposition peak temperature of oleic acid on the silver particle surface was 249 ° C., which was 9 ° C. higher than 240 ° C., which is the thermal decomposition peak temperature of oleic acid itself. From this, it was determined that the spherical silver particles coated with oleic acid were inferior in heat sinterability.
The activation energy of the thermal decomposition reaction of oleic acid covering the surface of the spherical silver particles was measured and found to be 100 kJ / mol. From this, it was determined that the spherical silver particles coated with oleic acid were inferior in heat sinterability. The pyrolysis peak temperature and activation energy are shown in Table 9.

To 100 parts of the spherical silver particles coated with oleic acid, 8 parts of isoparaffin which is a hydrocarbon as a volatile dispersion medium (manufactured by Shin Nippon Oil Co., Ltd., trade name ISOZOL, ISOZOL is a registered trademark) is added, A heat-sinterable silver paste was prepared by mixing uniformly using a spatula.
For this heat-sinterable silver paste, the porosity, volume resistivity and thermal conductivity of the porous sintered product, and the shear bond strength of the metal member assembly were measured, and the results are summarized in Table 9. .

This heat-sinterable silver paste was not sufficiently cured even when heated, and the electrical conductivity, thermal conductivity, and joining of the metal member assembly were insufficient.
From the above results, it was found that this method for evaluating the heat-sinterability of heat-sinterable silver particles is useful for determining the heat-sinterability of spherical silver particles coated with oleic acid.

The method for evaluating the heat-sinterability of organic-coated metal particles of the present invention is useful for accurately and efficiently selecting organic-coated metal particles having excellent heat-sinterability.
The method for producing a heat-sinterable metal paste according to the present invention is suitable for producing a heat-sinterable metal paste that is a porous sintered material having excellent conductivity, heat conductivity, and bonding strength accurately and efficiently. Useful.
The heat-sinterable metal paste produced by the production method of the present invention is used to form electrodes for various electronic components such as resistors and capacitors and various display elements; to form an electrically conductive film for electromagnetic shielding; capacitors, resistors, and diodes. Bonding chip components such as memory and arithmetic elements (CPU) to substrates; forming solar cell electrodes; forming external electrodes for chip-type ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors and multilayer ceramic actuators Useful.
The method for producing a metal member assembly of the present invention is useful for accurately and efficiently producing a metal member assembly excellent in bondability.

A Bonding strength test specimen 1 Silver substrate 2 Paste-like metal particle composition (porous sintered product after heat sintering)
3 Silver chip

Claims (15)

A method for evaluating the heat-sinterability of organic-coated metal particles by thermal analysis,
Each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is the pyrolysis peak temperature of the organic substance itself ( 2) If lower, it is determined that the heat-sinterability of the organic-coated metal particles is excellent,
When the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is equal to or higher than the pyrolysis peak temperature (2) of the organic substance itself, the heat-sinterability of the organic substance-coated metal particles is poor. The method for evaluating heat-sinterability of organic-coated metal particles, characterized in that If the pyrolysis peak temperature (1) is 2 ° C. or more lower than the pyrolysis peak temperature (2), it is judged that the heat-sintering property of the organic-coated metal particles is excellent, and the pyrolysis peak temperature (1) is the pyrolysis peak. The evaluation of the heat-sinterability of the organic-coated metal particles according to claim 1, wherein the heat-sinterability of the organic-coated metal particles is determined to be inferior when the temperature is 2 ° C or higher than the temperature (2). Method. A method for evaluating the heat-sinterability of organic-coated metal particles by thermal analysis,
The organic matter-coated metal particles are subjected to thermal analysis in an air stream, and are calculated from the relationship between the temperature increase rate in the thermal analysis and the thermal decomposition peak temperature (1) of the organic matter covering the surface of the metal particles. When the activation energy in the pyrolysis reaction of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, the method for evaluating the heat-sinterability of the organic-coated metal particles is characterized by determining that the heat-sinterability of the organic-coated metal particles is poor. Each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is the pyrolysis peak temperature of the organic substance itself ( 2) If lower, it is determined that the heat-sinterability of the organic-coated metal particles is excellent,
When the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is equal to or higher than the pyrolysis peak temperature (2) of the organic substance itself, the heat-sinterability of the organic substance-coated metal particles is poor. Next, a method for producing a heat-sinterable metal paste comprising mixing organic substance-coated metal particles determined to have excellent heat-sinterability with a volatile dispersion medium to form a paste. If the pyrolysis peak temperature (1) is 2 ° C. or more lower than the pyrolysis peak temperature (2), it is judged that the heat-sintering property of the organic-coated metal particles is excellent, and the pyrolysis peak temperature (1) is the pyrolysis peak. The method for producing a heat-sinterable metal paste according to claim 4, wherein when the temperature is higher than the temperature (2) by 2 ° C or more, it is determined that the heat-sinterability of the organic-coated metal particles is inferior. The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic substances covering the surface of the organic-coated metal particles are high- and intermediate-grade fatty acids and their The method for producing a heat-sinterable metal paste according to claim 4 or 5, wherein the heat-sinterable metal paste is selected from water-repellent derivatives. The organic matter-coated metal particles are subjected to thermal analysis in an air stream, and are calculated from the relationship between the temperature increase rate in the thermal analysis and the thermal decomposition peak temperature (1) of the organic matter covering the surface of the metal particles. When the activation energy in the pyrolysis reaction of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, it is determined that the heat-sinterability of the organic-coated metal particles is inferior, and then the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste. A method for producing a heat-sinterable metal paste. The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic substances covering the surface of the organic-coated metal particles are high- and intermediate-grade fatty acids and their The method for producing a heat-sinterable metal paste according to claim 7, wherein the method is selected from water-repellent derivatives. Each of the organic substance-coated metal particles and the organic substance itself is subjected to thermal analysis in an air stream, and the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is the pyrolysis peak temperature of the organic substance itself ( 2) If lower, it is determined that the heat-sinterability of the organic-coated metal particles is excellent,
When the pyrolysis peak temperature (1) of the organic substance covering the surface of the metal particles is equal to or higher than the pyrolysis peak temperature (2) of the organic substance itself, the heat-sinterability of the organic substance-coated metal particles is poor. The organic-coated metal particles determined to have excellent heat sinterability are mixed with a volatile dispersion medium to prepare a paste, and then the heat sinterable metal paste is prepared. A method for producing a metal member assembly, comprising interposing between a plurality of metal members and heating at a temperature at which the heat-sinterable metal can be sintered. If the pyrolysis peak temperature (1) is 2 ° C. or more lower than the pyrolysis peak temperature (2), it is judged that the heat-sintering property of the organic-coated metal particles is excellent, and the pyrolysis peak temperature (1) is the pyrolysis peak. The method for producing a metal member bonded body according to claim 9, wherein when the temperature is higher than the temperature (2) by 2 ° C or more, it is determined that the heat-sinterability of the organic-coated metal particles is inferior. The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic substances covering the surface of the organic-coated metal particles are high- and intermediate-grade fatty acids and their The method for producing a metal member assembly according to claim 9 or 10, wherein the metal member assembly is selected from water-repellent derivatives. The method for producing a metal member assembly according to any one of claims 9 to 11, wherein the metal member assembly is an electronic component. The organic matter-coated metal particles are subjected to thermal analysis in an air stream, and are calculated from the relationship between the temperature increase rate in the thermal analysis and the thermal decomposition peak temperature (1) of the organic matter covering the surface of the metal particles. When the activation energy in the pyrolysis reaction of the organic substance is less than 95 kJ / mol, it is determined that the heat-sintering property of the organic-coated metal particles is excellent,
The activation energy in the pyrolysis reaction of the organic substance calculated from the relationship between the rate of temperature increase in the thermal analysis and the thermal decomposition peak temperature (1) of the organic substance covering the surface of the metal particles is 95 kJ / mol or more. In some cases, it is determined that the heat-sinterability of the organic-coated metal particles is poor, and the organic-coated metal particles determined to have excellent heat-sinterability are mixed with a volatile dispersion medium to form a paste and heat-sinterable. A metal member characterized in that a metal paste is prepared, and then the heat-sinterable metal paste is interposed between a plurality of metal members and heated at a temperature at which the heat-sinterable metal can be sintered. Manufacturing method of joined body. The organic-coated metal particles are silver particles or copper particles having an average particle diameter (median diameter D50) of 0.1 μm or more and 50 μm or less, and the organic substances covering the surface of the organic-coated metal particles are high- and intermediate-grade fatty acids and their The method for producing a metal member assembly according to claim 13, wherein the metal member assembly is selected from water-repellent derivatives. The method for producing a metal member assembly according to claim 13 or 14, wherein the metal member assembly is an electronic component.