JP5887086B2 - Conductive material - Google Patents

Description

  The present invention relates to a conductive material in which a metal powder containing metal nanoparticles and metal particles having an average primary particle size larger than that of the metal nanoparticles is blended, more specifically, a screen printing method or an ink jet printing method. The present invention relates to a conductive material that can form electrodes and wiring patterns on a substrate by low-temperature heat treatment, and can bond electronic components on the substrate by low-temperature heat treatment.

  In recent years, in the field of mounting electronic components on a substrate, lead-free solder, for example, tin-silver solder, tin-copper solder, tin-silver-copper solder, has become the mainstream. However, lead-free solder has a high melting point, and the mounting temperature is as high as 250 ° C. or higher. Therefore, the electronic component or the substrate may be thermally damaged, and it cannot be applied to all the electronic components and the substrate. Therefore, when using a substrate with poor heat resistance, such as PET, or when it must be bonded at a low temperature due to the heat resistance problem of the module, etc., bismuth and indium alloys that can be electrically bonded at a relatively low temperature Was used. However, bismuth has a problem in bonding strength and alloy brittleness, and an indium alloy has a problem in that it is expensive.

  In order to increase the bonding strength between a substrate and an electronic component, a solder paste has been proposed in which solder powders having different melting points are blended and the low melting point solder powders are melted to connect the high melting point solder powders (Patent Documents). 1). In order to achieve both the fine pitch and the reduction of residues generated after soldering, a solder paste containing two or more kinds of solder particles having different average particle diameters has been proposed (Patent Document 2). Furthermore, in order to refine the solder composition after soldering and improve the bonding strength, a solder paste is proposed in which a solder powder in which predetermined nanoparticles of 5 to 300 nm are arranged on the surface of the solder powder and a flux are kneaded ( Patent Document 3).

  However, in all of the above Patent Documents 1 to 3, the melting point of the solder powder is still high and the electronic component and the substrate are easily damaged by heat, and the flux is mixed with the solder paste. There is a problem that residue is generated and the environment is loaded.

  On the other hand, silver paste that can be electrically joined at a relatively low temperature is used for mounting electronic components and modules that are unsuitable for soldering in terms of heat resistance, in order to prevent an increase in conduction resistance. Addition of a low melting point metal, a conductive filler, or metal nanoparticles to the silver paste is performed. Since metal nanoparticles have a large specific surface area and high reaction activity, they have the characteristic of low-temperature sintering that fuses at a low temperature compared to metal bulk. For example, in the case of silver nanoparticles, it is known that a fusion-bonding phenomenon occurs in a heat treatment at about 200 ° C., which is much lower than the original melting point of 964 ° C., and exhibits a conductivity comparable to that of a metal bulk. There is a problem that conductivity and bonding strength are insufficient.

JP-A 63-149094 JP 2005-81382 A WO2006 / 126564

  In view of the above circumstances, the present invention uses a low-temperature sintering property of metal nanoparticles to form a conductive material capable of obtaining a metal bond excellent in conductivity and mechanical properties, and a wiring pattern having good conductivity. An object of the present invention is to provide a conductive material that can be used.

  In an aspect of the present invention, a metal powder containing (A) metal nanoparticles having an average primary particle diameter of 1 to 100 nm and (B) second metal particles having an average primary particle diameter of 1 to 100 μm is blended. It is the electroconductive material characterized by having. The constituent components of the metal powder used in the conductive material of the present invention are the metal nanoparticles that are the first metal particles and the second metal particles having an average primary particle size larger than that of the metal nanoparticles. The “metal nanoparticles” are metal particles having an average primary particle diameter of nano-order, that is, 1 nm or more and less than 1 μm. In the present invention, metal particles having an average primary particle diameter of 1 to 100 nm are used. In the present specification, the “second metal particle” means a metal particle having an average primary particle diameter of micro order, that is, 1 μm or more and less than 1 mm. In the present invention, the average primary particle diameter is 1 to 1 mm. 100 μm metal particles are used. In embodiments of the present invention, no flux is included.

  Heat-treating a metal powder containing metal nanoparticles having an average primary particle diameter of 1 to 100 nm and second metal particles having an average primary particle diameter of 1 to 100 μm at a predetermined temperature lower than the melting point of the metal nanoparticles, That is, when low-temperature sintering is performed, the metal nanoparticles are sintered at a low temperature in a state where the metal nanoparticles are contained in the gap formed between the second metal particles. Thereby, the gap generated between the second metal particles is filled with the metal nanoparticles sintered at low temperature, and the generation of voids (air bubbles) is prevented. Moreover, as above-mentioned, the average primary particle diameter of a 2nd metal particle is larger than the average primary particle diameter of a metal nanoparticle. Therefore, as will be described later, even if the second metal particles are coated with an organic protective film, the amount of gas derived from the organic protective film per unit amount of the second metal particles generated during low-temperature sintering is the organic protective film. The amount of the coated metal nanoparticles is less than the amount of gas derived from the organic protective film per unit amount of metal nanoparticles generated during low-temperature sintering. Also in terms of the difference in the amount of gas generated, the use of metal powder containing metal nanoparticles and second metal particles prevents the generation of voids (air bubbles). Further, the second metal particles are joined to each other through the low-temperature sintered metal nanoparticles.

  On the other hand, when the metal powder composed of metal nanoparticles not containing the second metal particles is sintered at low temperature, the organic protective film covering the surface of the metal nanoparticles volatilizes and disappears upon heating. Sintering in a non-uniform dispersion of nanoparticles. As a result, since the sintered body has a metal network structure, it is considered that many voids (air bubbles) are generated. Moreover, in the metal powder which consists of the 2nd metal particle which does not contain a metal nanoparticle, since low temperature sintering does not arise, it is necessary to heat-process up to melting | fusing point intrinsic | native to a metal.

  “Low-temperature sintering” means that metal nanoparticles are fused and sintered at a temperature lower than the inherent melting point of the metal constituting the metal nanoparticles. In the present specification, the “average primary particle size” is the particle size before aggregation of the metal nanoparticles and the second metal particles, and after dispersion in a well-dispersed solvent by ultrasonic waves, etc. It means the value measured by the meter.

  An aspect of the present invention is the conductive material, wherein the metal powder contains 1 to 30% by mass of the (A) metal nanoparticles.

  An aspect of the present invention is a conductive material in which the metal nanoparticles (A) contain silver nanoparticles. In this embodiment, the metal species of the metal nanoparticles include at least silver.

  An aspect of the present invention is characterized in that the (B) second metal particle is at least one selected from the group consisting of silver, copper, a silver alloy, a copper alloy, and copper coated with silver. It is a conductive material.

  An aspect of the present invention is the conductive material, wherein the (B) second metal particles are covered with an organic protective film. An aspect of the present invention is the conductive material, wherein the organic protective film includes an imidazole derivative having an imidazole and / or a phenyl group.

  An aspect of the present invention is a conductive material characterized in that a solvent (C) is further blended. The solvent is blended for adjusting the viscosity of the conductive material.

  An aspect of the present invention is an electronic component joined body in which an electronic component is mounted on a substrate using the conductive material. According to another aspect of the present invention, there is provided an electronic component assembly in which the electronic component is an LED element.

  An aspect of the present invention includes a step of coating the conductive material on a circuit forming substrate to form an electrode and a wiring pattern, and heating the coated circuit forming substrate at 180 to 230 ° C. And a step of baking the electrodes and the wiring pattern.

  According to the present invention, the metal powder containing metal nanoparticles having an average primary particle diameter of 1 to 100 nm and second metal particles having an average primary particle diameter of 1 to 100 μm suppresses the generation of voids. Compared to metal bonding using only the metal bonding, metal bonding excellent in conductivity and mechanical strength can be obtained. Moreover, the wiring pattern excellent in electroconductivity can be formed rather than the wiring pattern using only metal nanoparticles. Furthermore, since the low-temperature sintering characteristics of the metal nanoparticles are used, metal bonding and wiring patterns can be formed at a low heat treatment temperature, and damage to the electronic components and substrates that are the objects of metal bonding can be prevented. Furthermore, since the conductive material contains no flux, the environmental load can be reduced.

  According to this invention, electroconductivity and mechanical strength improve with a good balance because a metal powder contains 1-30 mass% metal nanoparticles.

  According to the present invention, since the second metal particles are covered with an organic protective film, the second metal particles are prevented from being oxidized during the storage period of the conductive material, so that the conductivity is impaired. And the mechanical strength of the metal bond is further improved.

It is explanatory drawing which shows the outline of the measuring method of the shear strength of a chip resistance component. It is explanatory drawing which shows the outline of the measuring method of volume resistance.

  Next, the conductive material of the present invention will be described. The conductive material of the present invention is composed of (A) metal nanoparticles having an average primary particle diameter of 1 to 100 nm and (B) second metal particles having an average primary particle diameter of 1 to 100 μm. Has been.

(A) Metal nanoparticle The metal nanoparticle which is (A) component is a metal particle which has an average primary particle diameter of nano order. By having a nano-order average primary particle size, the specific surface area is large and the reaction activity of the particle surface is high, so that the electronic component can be electrically bonded to the substrate at a heating temperature much lower than the original melting point of the metal, A wiring pattern can be formed on the substrate. The metal species of the metal nanoparticles are not particularly limited as long as they have good conductivity. For example, gold, silver, copper, platinum, palladium, nickel, bismuth, lead, indium, tin, zinc, titanium, aluminum and Examples thereof include a simple metal used for solder such as antimony and a metal alloy containing the above metal species. Among the above metal species, silver and copper are preferable from the viewpoint of having excellent conductivity and thermal conductivity.

  The upper limit of the average primary particle diameter of the metal nanoparticles can be selected as appropriate, but it is 100 nm from the viewpoint of low-temperature sinterability, and 50 nm is preferable from the viewpoint of surely preventing the generation of voids. 20 nm is particularly preferable from the viewpoint of application to a part and formation of a fine wiring pattern, and 10 nm is particularly preferable from the viewpoint of reliably exhibiting low-temperature sinterability. The lower limit of the average primary particle diameter of the metal nanoparticles can be selected as appropriate, but it is 2 nm from the viewpoint of processability such as coating treatment of the metal nanoparticles, and the mixing property and conductivity with the second metal particles. 5 nm is preferable from the viewpoint of the production stability of the material, and 7 nm is particularly preferable from the viewpoint of further improving the mixing property and the production stability. These metal nanoparticles may be used alone or in combination of two or more.

Since the metal nanoparticles have high surface reaction activity, they tend to aggregate, and as a result, dispersion stability may be impaired. In order to prevent this, the surface of the metal nanoparticles may be covered with an organic protective film. The component of the protective film is not particularly limited as long as it is a compound that covers the surface of the metal nanoparticle and prevents aggregation of the metal nanoparticle. For example, a coordinate bond between the metal nanoparticle and the lone electron pair is formed. Mention may be made of organic compounds having groups containing oxygen, nitrogen or sulfur atoms. The above-described oxygen atom, nitrogen atom, or sulfur atom is bonded to the surface of the metal nanoparticle by intermolecular force due to electrostatic force, so that the protective film covers the metal nanoparticle. Examples of groups containing oxygen atoms include hydroxy groups (—OH), oxy groups (—O—), carbonyl groups (═O), carboxyl groups (═COOH), and groups containing nitrogen atoms such as amino groups ( As an example of a group containing —NH ₂ ) or a sulfur atom, a sulfanyl group (—SH) can be mentioned.

  The method for producing the metal nanoparticles coated with the protective film is not particularly limited. For example, the gas evaporation method described in JP-A-3-34211 and the active continuous interface deposition described in JP-A-2008-150630 And a physical method such as a chemical method, and a chemical method of reducing a silver salt described in JP-A-2009-120949, JP-A-2005-036309, or the like with a reducing agent.

(B) 2nd metal particle The 2nd metal particle which is (B) component is a metal particle which has an average primary particle diameter of a micro order. When the second metal particles are blended with the metal nanoparticles, the metal nanoparticles are sintered at a low temperature in a state where the metal nanoparticles are contained in the gap generated between the second metal particles. As a result, the gaps between the second metal particles are filled with the metal nanoparticles that have been sintered at a low temperature, thereby preventing the generation of voids (air bubbles). Moreover, when the metal nanoparticles that have entered between the second metal particles are sintered at a low temperature, the second metal particles are bonded to each other through the low-temperature sintered metal nanoparticles. Thereby, compared with the electroconductive material which used only the metal nanoparticle as metal powder, the intensity | strength and electroconductivity of metal joining, and the electroconductivity of a wiring pattern improve further. The metal species of the second metal particle is not particularly limited as long as it has good conductivity. For example, gold, silver, copper, platinum, palladium, nickel, bismuth, lead, indium, tin, zinc, titanium, Examples thereof include simple metals used for solder, such as aluminum and antimony, and metal alloys containing the above metal species. Among the above metal species, silver and copper are preferable from the viewpoint of having excellent conductivity and thermal conductivity, and silver is particularly preferable from the viewpoint that both the strength and conductivity of metal bonding are excellent.

  The upper limit of the average primary particle diameter of the second metal particles is 100 μm from the viewpoint of adhesion between the second metal particles, and 50 μm from the viewpoint of the area and pitch size of the joint when used as a joining material. 20 μm is particularly preferable from the viewpoint of enabling supply to a finer region. The lower limit of the average primary particle diameter of the second metal particles is 1 μm from the viewpoint of preventing aggregation of the second metal particles, and preferably 2 μm from the viewpoint of forming a dense metal bond. 3 μm is particularly preferable from the viewpoint of reliably forming a dense metal joint with reduced voids by suppressing the total amount. These 2nd metal particles may be used independently, and 2 or more types may be mixed and used for them.

  The second metal particles may have a surface coated with an organic protective film. The organic protective film covering the surface of the second metal particles prevents oxidation of the second metal particles during storage. Therefore, the protective film improves the strength of metal bonding without impairing conductivity. As an organic substance which coat | covers the surface of a 2nd metal particle, the organic substance which has the group containing the nitrogen atom which can be coordinated by the 2nd metal particle and a lone electron pair can be mentioned, for example. Specific examples include imidazole and imidazole derivatives having a phenyl group. Examples of the imidazole derivative having a phenyl group include imidazole compounds represented by the following general formula.

(In the formula, R ₁ represents hydrogen or a linear or branched alkyl group having 1 to 11 carbon atoms. R ₂ independently represents a linear or branched alkoxy group having 1 to 11 carbon atoms. R ₃ represents, independently of each other, a linear or branched alkyl group having 1 to 11 carbon atoms, chlorine or bromine, m is an integer of 1 to 4, and n is an integer of 0 to 4. .)

  Specifically, 2-phenyl-4- (2-methoxy) phenylimidazole, 2-phenyl-4- (3-methoxy) phenylimidazole, 2-phenyl-4- (3-ethoxy) phenylimidazole, 2-phenyl -4- (3,4-dimethoxy) phenylimidazole, 2-phenyl-4- (3,4-dimethoxy) phenyl-5-methylimidazole, 2-phenyl-4- (2-methoxy-5-methyl) phenylimidazole 2-phenyl-4- (2-chloro-5-methoxy) phenylimidazole, 2-phenyl-4- (2,5-dimethoxy-3-methyl) phenylimidazole, 2-phenyl-4- (2,3, 5-trimethoxy-6-methyl) phenylimidazole and the like.

  The coating amount of the organic substance on the second metal particles can be selected as appropriate, but the upper limit is 10 parts by mass with respect to 100 parts by mass of the second metal particles from the viewpoint of reliably suppressing the generation of voids. Preferably, 5 parts by mass is particularly preferable from the viewpoint of reliably reducing the volatile organic component and forming a dense metal bond. On the other hand, the lower limit is preferably 1 part by mass with respect to 100 parts by mass of the second metal particles from the viewpoint of preventing oxidation of the second metal particles, and 3 masses in terms of reliably covering the second metal particles. Part is particularly preferred. These components of the organic protective film may be used alone or in combination of two or more.

  The method of coating the surface of the second metal particles with an organic material to form an organic protective film is not particularly limited. For example, an organic substance that is a component of the protective film is dissolved in an organic acid (for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, etc.), and then the formation of the protective film of the organic substance on the second metal particles is promoted. Metal compounds that are protective film formation aids (eg, copper formate, cuprous chloride, cupric chloride, copper oxalate, copper acetate, copper hydroxide, cuprous oxide, cupric oxide, copper carbonate, phosphorus Copper oxide, copper sulfate, manganese formate, manganese chloride, manganese oxalate, manganese sulfate, zinc acetate, zinc bromide, zinc hydride, iron chloride, iron oxide, copper iodide, copper bromide, copper bromide, etc.) Dissolve. Next, after adding pure water, the pH is adjusted with an alkali to prepare a protective film-forming treatment solution. The second metal particles are immersed and stirred in the treatment liquid at a predetermined temperature (for example, 30 to 50 ° C.) for a predetermined time (for example, 1 to 3 hours), and then the second metal particles are taken out, washed with water, and dried. By this, the method of creating the 2nd metal particle coat | covered with organic substance is mentioned.

  Moreover, when using metal seed | species (for example, copper) other than silver for the 2nd metal particle, it is good also as the 2nd metal particle which coat | covered silver powder on the surface of this metal seed | species. By coating the surface of the second metal particles of a metal species other than silver with silver, the conductive material containing the second metal particles of silver is produced at a lower cost than that of adding the second metal particles of silver. A conductive material having similar characteristics, that is, a conductive material that is superior in both strength and conductivity of metal bonding can be obtained.

  The coating amount of silver powder can be selected as appropriate, but the upper limit is preferably 30 parts by mass, particularly preferably 20 parts by mass with respect to 100 parts by mass of the second metal particles. On the other hand, the lower limit is preferably 5 parts by mass with respect to 100 parts by mass of the second metal particles from the viewpoint of improving the strength and conductivity of metal bonding, and 10 parts by mass in terms of reliably expressing the characteristics of silver. Is particularly preferred.

  The upper limit of the mixing ratio of the metal nanoparticles in the metal powder containing the metal nanoparticles and the second metal particles is 90% by mass from the viewpoint of suppressing the generation of voids, and the strength of metal bonding is surely increased. 80 mass% is preferable from the point which improves, and 30 mass% is especially preferable from the point which improves the intensity | strength and electroconductivity of metal joining more. Moreover, the lower limit of the compounding ratio of the metal nanoparticles in the metal powder is 0.1% by mass from the point of joining the second metal particles to each other, and the low-temperature sinterability of the conductive material is reliably improved. 0.5 mass% is preferable from the point, and 1 mass% is particularly preferable from the viewpoint of further improving the strength and conductivity of metal bonding.

  In the present invention, (C) a dispersion medium may be blended as necessary. By blending the dispersion medium, the viscosity of the conductive material is adjusted, and for example, by making it into a paste, the coating property of the conductive material can be improved. The solvent also functions as a lubricant when the metal nanoparticles move through the conductive material paste during low-temperature sintering.

  Examples of the dispersion medium include saturated or unsaturated aliphatic hydrocarbons such as decane, tetradecane, and octadecane; ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; methyl cellosolve; Glycol ethers such as ethyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol monoethyl ether, triethylene glycol monoethyl ether; ethyl acetate, acetic acid Butyl, cellosolve acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether Esters such as cetate, propylene glycol monomethyl ether acetate and esterified products of the above glycol ethers; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, hexyl diglycol and terpineol, and unsaturated carbonization having 30 or more carbon atoms such as squalane Examples thereof include hydrogen.

  These dispersion media are preferably organic solvents having a flash point of 50 ° C. or higher and a boiling point of 150 ° C. or higher from the viewpoint of being able to be stably stored at room temperature and suppressing transpiration during low-temperature sintering, for example, hexyl diglycol, terpineol Can be mentioned.

  Although the compounding quantity of a dispersion medium can be mix | blended suitably according to desired viscosity, it is 1-300 mass parts with respect to 100 mass parts of metal powder containing the metal nanoparticle and the 2nd metal particle, for example. From the point which prevents the crack of a coating film, 20-200 mass parts is preferable. When the conductive material is made into a paste, the viscosity in the B-type viscometer is, for example, 5 Pa · s to 400 Pa · s at 25 ° C., and 20 Pa · s to 300 Pa · s at 25 ° C. from the viewpoint of coating workability. In view of application by screen printing or dispenser and function as a lubricant, 50 Pa · s to 200 Pa · s at 25 ° C. is particularly preferable. Moreover, these dispersion media may be used independently and may mix and use 2 or more types.

  Conventional additives may be appropriately blended in the conductive material depending on the application. Examples of additives include gloss imparting agents, metal corrosion inhibitors, stabilizers, fluidity improvers, dispersion stabilizers, thickeners, viscosity modifiers, moisturizers, thixotropic agents, antifoaming agents, and bactericides. An agent, a filler, etc. can be mentioned. These additives may be used alone or in combination of two or more.

  Next, the manufacturing method of the electroconductive material of this invention is demonstrated. The method for producing the conductive material is not particularly limited. For example, the conductive material can be produced by mixing the metal nanoparticles and the second metal particles with a general-purpose mixer. Further, when it is desired to adjust the conductive material to a predetermined viscosity, for example, to form a paste, it is obtained by adding and dispersing metal nanoparticles and second metal particles in a predetermined amount of dispersion medium.

  Next, application examples and usage examples of the conductive material of the present invention will be described. The conductive material of the present invention can be used for various applications. The conductive material of the present invention includes metal nanoparticles, and the metal nanoparticles can be sintered at a temperature lower than the melting point of the constituent metal species (for example, about 200 ° C. in the case of silver and copper). That is, it has low temperature sinterability. Therefore, since the conductive material of the present invention contains metal nanoparticles, it has low-temperature sinterability. Therefore, an electronic component is electrically and physically connected to a material for metal bonding between components, for example, a substrate such as a printed wiring board. There is an application as a conductive bonding material to be bonded, a film material for forming a conductive film, for example, a wiring material for forming a wiring pattern on a substrate such as a printed wiring board.

  When used as a conductive bonding material, for example, the conductive material of the present invention is applied to the position where the electronic component is bonded on the substrate, and the electronic component is placed on the applied conductive material film and then fired. Processing to bond electronic components on the substrate. The method for applying the conductive material is not particularly limited, and examples thereof include a screen printing method, a dispenser method, and an ink jet method. The application amount of the conductive material can be selected as appropriate. For example, the conductive material is applied in a thickness of 1 to 20 μm. The firing temperature is not particularly limited as long as the metal nanoparticles are fused to each other and sintered at a low temperature. For example, when the metal nanoparticles are copper or silver, the firing temperature is 180 to 230 ° C., preferably 190. ~ 210 ° C. Moreover, baking time can be selected suitably, for example, is 5 to 120 minutes. The material of the substrate to be used is not particularly limited, and in addition to inorganic materials such as glass and metal oxides, the conductive material of the present invention has low-temperature sinterability, so it has poor heat resistance compared to inorganic materials. Organic materials such as polyester resins, polycarbonate resins, styrene resins, and fluororesins can also be used.

  When used as a conductive wiring material, for example, a wiring pattern in which a desired wiring pattern is drawn with a conductive material on a substrate, the drawn wiring pattern is baked, and then sintered on the substrate. Form. The coating method of the conductive material is not particularly limited as long as it is a coating method capable of forming a wiring pattern, and examples thereof include a screen printing method and an ink jet method. The application amount of the conductive material, the firing conditions, and the usable substrate material can be appropriately selected as in the case of using the conductive bonding material. This usage example can be applied to the formation of fine wiring patterns by utilizing the fact that metal nanoparticles are blended in metal powder.

  Next, the present invention will be described in more detail using examples. However, this invention is not limited to the aspect of the Example shown below.

Examples 1-11, Comparative Examples 1-3
Hereinafter, examples in which the conductive material of the present invention is used as a conductive bonding material and a conductive wiring material will be described.

(1) About the compounding component of electroconductive material (A) Metal nanoparticle and commercially available silver nanoparticle "TIV-A01" (made by DOWA Electronics Co., Ltd.) were used. These nanoparticles are powders having an average primary particle size of 20 nm and are coated with 5% by mass of hexanoic acid.
(B) Second metal particle / silver particle 1: spherical, average primary particle size 3.5 μm, no coating / silver particle 2: spherical, average primary particle size 3.5 μm, imidazole derivative coated product / copper particle 1: spherical , Average primary particle size 3.0 μm, uncoated copper particles 2: spherical, average primary particle size 3.0 μm, imidazole derivative coated product, copper particles 3: spherical, average primary particle size 3.0 μm, silver coated product

  As the imidazole derivative, 2-phenyl-4- (2-methoxy) phenylimidazole was used. Moreover, as a result of measuring by the thermogravimetric analysis method (TG-DTA method), as for the silver particle 2 and the copper particle 2, all were 3 mass% imidazole derivative coating amount. The silver coat product which is the copper particle 3 is “Ag coat Cu-HWQ 5 μm” manufactured by Fukuda Metal Foil Powder Co., Ltd., and the silver coating amount is 10 mass%.

  The production of the second metal particles (silver particles 2, copper particles 2) coated with the imidazole derivative was carried out as follows. First, 0.3 g of 2-phenyl-4- (2-methoxy) phenylimidazole was dissolved in 10 g of acetic acid, 0.05 g of zinc bromide was dissolved, and the total amount was adjusted to 100 g with pure water. Next, the pH was adjusted to 4 with 17% aqueous ammonia to prepare a treatment solution capable of forming a coating. Next, after 10 g of the second metal particles were immersed in the treatment liquid at 40 ° C. for 2 hours and stirred, the second metal particles were taken out from the treatment liquid, washed with water, and dried to be coated with the imidazole derivative. Second metal particles were produced.

(2) Method for preparing conductive material used as conductive bonding material and conductive wiring material Metal nanoparticles, any one of silver particles 1 and 2, and copper particles 1 to 3, and a dispersion medium for viscosity adjustment Was added and mixed for 5 minutes using a pestle to prepare a paste of conductive material.

  By using the method for preparing the conductive material, the components of the metal nanoparticles and the second metal particles shown in Table 1 below are blended at the blending ratios shown in Table 1 below. Conductive material pastes of Examples 1-3 were prepared. In each of Examples 1 to 11 and Comparative Examples 1 to 3, the amount of the dispersion medium was 20 parts by mass with respect to 100 parts by mass of metal powder composed of metal nanoparticles and second metal particles. As the dispersion medium, terpineol C (manufactured by Nippon Terpene Co., Ltd., α-, β-, γ-terpineol mixture) was used. In addition, the compounding quantity of the metal nanoparticle shown in following Table 1 and a 2nd metal particle represents the mass%.

(3) Performance evaluation (1) Shear strength of chip parts On a copper substrate with Ni / Au plating on the surface, paste the conductive material prepared as described above with a metal squeegee using a 150 μmt metal mask. After printing, 10 Ni / Au plated copper chips of 2 mm × 2 mm were placed on the printed film of the copper substrate. And the Ni / Au plating copper chip mounted on the copper substrate was joined by 200 degreeC and 60 minute oven heating, and the test piece was produced. About this test piece, the shear strength of the Ni / Au plating copper chip was measured on condition of 5 mm / min using the tensile testing machine (EZ-L by SHIMADZU Co., Ltd.). In addition, a measurement result is an average value of ten Ni / Au plating copper chips which measured shear strength.

(2) Volume resistance The conductive material paste prepared as described above was applied on a slide glass by screen printing in a length of 5 cm x width of 1 cm, and the coating film was baked by heating at 200 ° C for 60 minutes. Thereafter, the film thickness was measured, and the volume resistance (specific resistance) value was calculated by measuring the resistance value using a micrometer manufactured by Iwadori Measurement Co., Ltd.

  The evaluation results of Examples 1 to 11 and Comparative Examples 1 to 3 are shown in Table 2 below.

  Regarding the shear strength of the chip parts in Table 2, “impossible to measure” means that the shear strength of the chip parts could not be measured because the Ni / Au plated copper chip could not be bonded onto the copper substrate.

  As shown in Table 2, when a metal powder blended with metal nanoparticles and second metal particles is used as the conductive material, the chip component is compared with a blend of metal nanoparticles or second metal particles. As a result, the shear strength of the metal was improved, and a metal joint excellent in mechanical strength was obtained. From the comparison between Example 1 and Example 8, Example 9 and Example 10, the shear strength of the chip component was further improved by coating the second metal particles with an imidazole derivative. From Example 9 and Example 11, by coating the surface of the copper particles with silver, the shear strength of the chip part is further improved, and the mechanical strength of the metal joint is nearly the same as when silver particles are blended. was gotten. Moreover, the shear strength of the chip part was further improved by setting the blending amount of the metal nanoparticles to 1 to 30% by mass.

  As shown in Table 2, when a metal powder blended with metal nanoparticles and second metal particles is used as the conductive material, it has a volume resistance as compared with that blended with metal nanoparticles or second metal particles. As a result, a wiring pattern having excellent conductivity could be formed. From comparison between Example 1 and Example 8 and Example 9 and Example 10, the volume resistance was not impaired even when the second metal particles were coated with an imidazole derivative. From Example 9 and Example 11, by coating the surface of the copper particles with silver, the volume resistance was further reduced, and the conductivity of the wiring pattern was obtained to the same extent as when silver particles were blended. Moreover, the electroconductivity of the wiring pattern was further improved by making the compounding quantity of a metal nanoparticle into 1-30 mass%.

  The conductive material of the present invention can electrically bond the substrate and the electronic component by a heat treatment at a temperature lower than the melting point of the metal nanoparticles and the second metal particles, and can form a wiring pattern on the substrate by the low-temperature heat treatment. Therefore, the utility value is particularly high in the field of mounting electronic components on a printed wiring board.

Claims (6)

(A) metal nanoparticles having an average primary particle diameter of 7 to 50 nm and (B) at least one second metal particle selected from the group consisting of silver and copper having an average primary particle diameter of 3 to 20 μm And (C) a dispersion medium containing a conductive powder,
The (B) second metal particles have the following general formula:

(In the formula, R ₁ represents hydrogen or a linear or branched alkyl group having 1 to 11 carbon atoms. R ₂ independently represents a linear or branched alkoxy group having 1 to 11 carbon atoms. R ₃ represents, independently of each other, a linear or branched alkyl group having 1 to 11 carbon atoms, chlorine or bromine, m is an integer of 1 to 4, and n is an integer of 0 to 4. .) are coated with an organic protective layer containing an imidazole compound represented by,
Wherein (C) the dispersion medium, a conductive material characterized mixture der Rukoto of α- terpineol and β- terpineol and γ- terpineol.   The conductive material according to claim 1, wherein the metal powder contains 1 to 30% by mass of the (A) metal nanoparticles.   The conductive material according to claim 1, wherein the metal nanoparticles (A) contain silver nanoparticles. An electronic component assembly comprising an electronic component mounted on a substrate using the conductive material according to any one of claims 1 to 3 . The electronic component assembly according to claim 4 , wherein the electronic component is an LED element. Applying a conductive material according to any one of claims 1 to 3 on a circuit forming substrate to form an electrode and a wiring pattern;
Heating the coated circuit-forming substrate at 180 to 230 ° C. and firing the electrodes and the wiring pattern.

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