WO2016076353A1 - Au-Sn ALLOY SOLDER PASTE, METHOD FOR MANUFACTURING Au-Sn ALLOY SOLDER LAYER, AND Au-Sn ALLOY SOLDER LAYER - Google Patents

Abstract

This Au-Sn alloy solder paste includes an Au-Sn alloy powder that includes Sn at a level within a range of 61-70 mass%, with the remainder being Au and unavoidable impurities, and a flux. The oxygen concentration in the Au-Sn alloy powder is within the range of 50-1,800 mass ppm.

Description

Au-Sn alloy solder paste, method for producing Au-Sn alloy solder layer, and Au-Sn alloy solder layer

The present invention relates to, for example, an Au—Sn alloy solder paste used when joining a base material and an object to be joined, a method for producing an Au—Sn alloy solder layer using this Au—Sn alloy solder paste, and Au— The present invention relates to a Sn alloy solder layer.
This application claims priority on November 13, 2014 based on Japanese Patent Application No. 2014-230609 for which it applied to Japan, and uses the content here.

In general, in a semiconductor device such as an LED device, various solder pastes are used when a circuit board (base material) and a semiconductor element (joined body) are joined.
As a solder paste used in the above-described semiconductor device or the like, for example, Patent Document 1 discloses an Au-90 mass% Sn alloy solder containing 90 mass% of Sn. Patent Document 2 discloses an Au-20 mass% Sn alloy solder containing 20 mass% of Sn.

In the Au-90 mass% Sn alloy solder described in Patent Document 1, the melting point (eutectic temperature) is as low as 217 ° C. as shown in the Au—Sn binary phase diagram of FIG. There is a possibility that the formed solder layer may be melted due to heat generation or temperature rise in the use environment. That is, a solder layer having sufficient heat resistance could not be obtained.
In addition, in the Au-20 mass% Sn alloy solder described in Patent Document 2, the melting point (eutectic temperature) is 278 ° C. as shown in the Au—Sn binary phase diagram of FIG. Therefore, it is superior in heat resistance to Au-90 mass% Sn alloy solder. However, since the Au-20 mass% Sn alloy solder contains more Au that is more expensive than the Au-90 mass% Sn alloy solder, there is a problem in that the manufacturing cost is significantly increased.

Therefore, in Patent Document 3, Au-20 mass% Sn alloy solder powder and Au-90 mass% Sn solder alloy powder are mixed, and Sn is 55 to 70 with respect to a total of 100 mass parts of Au and Sn. An Au—Sn alloy solder paste containing parts by mass is disclosed.
In this Au—Sn alloy solder paste, at the time of soldering, the Au-90 mass% Sn solder alloy powder having a low eutectic temperature is melted to wet the semiconductor element or circuit board as the joined body, and then melted. The Au—90 mass% Sn solder alloy and the Au-20 mass% Sn solder alloy diffuse to form an Au—Sn solder alloy layer having a composition in which they are mixed.

JP 2008-137017 A JP 2006-007288 A JP 2011-167741 A

By the way, in the Au—Sn alloy solder paste described in Patent Document 3, Au-20 mass% Sn alloy solder powder and Au-90 mass% Sn solder alloy powder are mixed and melted Au-90 mass% Sn solder. The alloy and Au-20 mass% Sn solder alloy are diffused. For this reason, it has been found that the composition of the Au—Sn alloy solder layer formed after melting is highly likely to vary.
Moreover, since the process which manufactures the powder of two types of alloy compositions, ie, the atomization process and the classification process, is needed, and the process of mixing powders is also required after that, there also existed the subject that throughput was also bad.
Here, it is conceivable to produce an Au—Sn alloy solder paste using the Au—Sn alloy powder having the composition described in Patent Document 3.

However, in the Au—Sn alloy powder, it becomes clear that when the Sn content is increased, the powders easily aggregate together and the yield of the Au—Sn alloy powder after classification is reduced. It was. Further, when the paste is formed in the presence of the agglomerated Au—Sn alloy powder, the agglomerated Au—Sn alloy powder cannot sufficiently contact with the flux, and there is a possibility that poor melting or poor printing may occur. there were. This is because, in an Au—Sn alloy powder having a high Sn content, if the metal surface is not oxidized, the surface activity becomes very high and unstable, and the powder is agglomerated and becomes stable. It is presumed to be due to trying.

The present invention has been made in view of the above-described circumstances, and is an Au—Sn alloy solder paste that is excellent in meltability and can form a solder layer having sufficient heat resistance even when bonded at a relatively low temperature. Another object is to provide an Au—Sn alloy solder layer manufacturing method using this Au—Sn alloy solder paste, and an Au—Sn alloy solder layer.

In order to solve the above problems, an Au—Sn alloy solder paste which is one embodiment of the present invention includes an Au—Sn alloy containing Sn in a range of 61 mass% to 70 mass% with the balance being Au and inevitable impurities. Including the powder and the flux, the oxygen concentration in the Au—Sn alloy powder is in the range of 50 ppm to 1800 ppm by mass.

According to the Au—Sn alloy solder paste, Sn is contained in the range of 61 mass% to 70 mass%, and the balance has Au—Sn alloy powder having a composition composed of Au and inevitable impurities. According to the Au—Sn binary phase diagram shown in FIG. 2, the solidus temperature of this Au—Sn alloy powder is 252 ° C. For this reason, it is possible to perform bonding even under relatively low temperature conditions. Further, since the liquidus temperature is about 300 ° C., the heat resistance of the formed solder alloy layer can be ensured.

Furthermore, since the oxygen concentration in the Au—Sn alloy powder is 50 ppm by mass or more, an oxide film is formed on the surface of the Au—Sn alloy powder, thereby suppressing aggregation of the Au—Sn alloy powder. It becomes possible. Thereby, the yield of Au-Sn alloy powder after classification can be improved. In addition, it is possible to suppress the occurrence of poor melting or printing failure of the Au—Sn alloy solder paste.
Furthermore, since the oxygen concentration in the Au—Sn alloy powder is limited to 1800 ppm by mass or less, the meltability is not adversely affected when mixed with the flux.

Here, in the Au—Sn alloy solder paste which is one embodiment of the present invention, it is preferable that the average particle diameter of the Au—Sn alloy powder is in the range of 1 μm to 25 μm.
In this case, since the average particle diameter of the Au—Sn alloy powder is in the range of 1 μm or more and 25 μm or less, the Au—Sn alloy solder paste can be printed on a minute area without causing printing defects using a printing machine. In addition, since the Au—Sn alloy powder can be reliably melted during the melting process, the occurrence of poor melting can be suppressed.

In the Au—Sn alloy solder paste which is one embodiment of the present invention, the content of the flux is preferably in the range of 5 mass% to 40 mass% of the entire paste.
In this case, since the content of the flux is in the range of 5% by mass or more and 40% by mass or less of the entire paste, the printability of the Au—Sn alloy solder paste is improved and the Au at the time of the melting process is improved. -Insufficient aggregation of Sn alloy powder can be suppressed.

In the method for producing an Au—Sn alloy solder layer which is one embodiment of the present invention, the above Au—Sn alloy solder paste is disposed on the surface of a base material, and the Au—Sn alloy solder paste is heated and melted. It is characterized by that.
According to the manufacturing method of the Au—Sn alloy solder layer having this configuration, since the Au—Sn alloy solder paste described above is heated and melted, the liquidus temperature becomes about 300 ° C., and Au having excellent heat resistance. A Sn alloy solder layer can be obtained.

Here, in the method for producing an Au—Sn alloy solder layer according to an aspect of the present invention, the base material having an Au film formed on the surface thereof is prepared, and the Au—Sn alloy solder is formed on the Au film. It is preferable to dispose a paste and to melt by heating to a temperature between the solidus temperature of the Au—Sn alloy constituting the Au—Sn alloy solder paste + 30 ° C. or more and the liquidus temperature or less.

When the above-mentioned Au—Sn alloy solder paste is heated to a temperature of the solidus temperature of the Au—Sn alloy constituting the Au—Sn alloy solder paste + 30 ° C. or more and the liquidus temperature or less, the Au—Sn alloy solder paste A part of it melts to form a sherbet, and the liquid phase Au—Sn spreads out to form a thin film phase. Further, it was found that a thin film phase was formed, and the remaining composition region of the thin film phase wetted and spread as a liquid phase was formed as a thick film phase at the center of the thin film phase. It was found that the thin film phase spread by wetting was a Sn—Au phase containing Sn as a main component. Further, it was found that the thick film phase in the central part was formed with a high Au content phase in which the Au content was relatively higher than that of the liquid Sn—Au phase. That is, it can be seen that the central portion of the formed Au—Sn alloy solder layer is further heated (the solidus temperature and the liquidus temperature are rising).
In addition, the Sn-Au phase (thin film phase) that has spread out reacts with the Au film formed on the surface of the base material, so that the solidus temperature and the liquidus temperature rise, and solidifies while being held at the heating temperature. To do. Therefore, the Au—Sn alloy solder layer formed after solidification has an increased solidus temperature and liquidus temperature, and is particularly excellent in heat resistance.

Here, at the actual use temperature at the time of joining, reflow is usually performed at a temperature 30 to 50 degrees higher than the melting end temperature of the solder (liquidus temperature, eutectic temperature in the case of a eutectic alloy). Therefore, in the Au-20 mass% Sn alloy solder described in Patent Document 2, since the melting point (eutectic temperature) is 278 ° C., the actual temperature is reflowed from 308 ° C. to 328 ° C. and mounted. Depending on the type of the object, for example, the LED element, it is reflowed at a temperature close to the heat resistant limit temperature, and there is a risk of thermally damaging the mounted object.
On the other hand, in the method for producing an Au—Sn alloy solder layer which is one embodiment of the present invention, the solidus temperature of the Au—Sn alloy powder is 252 ° C., and the liquidus temperature is about 300 ° C. . In Patent Documents 1, 2, and 3, all of eutectic alloy powder paste is used, but in the present invention, an alloy having a difference between the solidus temperature and the liquidus temperature of about 50 ° C. is used instead of the eutectic alloy. . As a result of various evaluations using the above-mentioned alloys, the melting end temperature (liquidus temperature) which is set as the MAX temperature of the normal mounting reflow temperature +30 to 50 ° C., the solidus temperature +30 to It was clarified that the material can be sufficiently melted and bonded at 50 ° C., that is, from 282 ° C. which is a solidus temperature of 252 ° C. + 30 ° C. to 302 ° C. which is a solidus temperature of 252 ° C. + 50 ° C. That is, compared with the case where the Au-20 mass% Sn solder alloy of patent document 2 is used, the thermal damage of a to-be-mounted object can be reduced.

An Au—Sn alloy solder layer which is one embodiment of the present invention is obtained by the above-described method for producing an Au—Sn alloy solder layer.
The Au—Sn alloy solder layer having this structure once formed after reflow has a relatively high solidus temperature and liquidus temperature, and is excellent in heat resistance. Therefore, it can be used satisfactorily even under high temperature use conditions.

According to the present invention, an Au—Sn alloy solder paste having excellent meltability and capable of forming a solder layer having sufficient heat resistance even when bonded at a relatively low temperature, and this Au—Sn alloy solder paste were used. It is possible to provide a method for producing an Au—Sn alloy solder layer and an Au—Sn alloy solder layer.

It is an Au-Sn binary phase diagram. It is explanatory drawing of the manufacturing method of the Au-Sn alloy solder layer which is this embodiment. 2 is an observation photograph of an Au—Sn alloy solder layer of the present invention.

Hereinafter, the Au—Sn alloy solder paste 20, the method for producing the Au—Sn alloy solder layer 30, and the Au—Sn alloy solder layer 30 according to an embodiment of the present invention will be described.
The Au—Sn alloy solder paste 20 according to this embodiment is used when, for example, an LED element (material to be joined) and a circuit board (base material) are joined.

The Au—Sn alloy solder paste 20 according to the present embodiment includes Sn in a range of 61 mass% to 70 mass%, with the balance being Au—Sn alloy powder composed of Au and inevitable impurities, and a flux. The oxygen concentration in the Au—Sn alloy powder is in the range of 50 ppm to 1800 ppm by mass.

In the present embodiment, the average particle diameter of the Au—Sn alloy powder is in the range of 1 μm to 25 μm.
Furthermore, in this embodiment, the content of the flux is in the range of 5% by mass or more and 40% by mass or less of the entire paste.
The reason why the composition of the Au—Sn alloy powder, the oxygen concentration in the Au—Sn alloy powder, the average particle diameter of the Au—Sn alloy powder, and the flux content are specified as described above will be described below.

(Composition of Au-Sn alloy powder)
When the Sn content in the Au—Sn alloy powder is less than 61% by mass, the δ phase having a solidus temperature of 309 ° C. is produced according to the Au—Sn binary phase diagram of FIG. It becomes difficult to melt the material, and there is a concern about thermal damage of the mounted object. On the other hand, if the Sn content in the Au—Sn alloy powder exceeds 70% by mass, the solidus temperature decreases to 217 ° C., and the heat resistance of the formed Au—Sn alloy solder layer 30 may not be ensured. There is.
From the above, in this embodiment, the Sn content in the Au—Sn alloy powder is set in the range of 61 mass% to 70 mass%. The Sn content in the Au—Sn alloy powder is preferably 65% by mass or more and 70% by mass or less, but is not limited thereto.

(Oxygen concentration of Au-Sn alloy powder)
In the Au—Sn alloy powder, as the Sn content increases, the powders tend to aggregate. This is presumably because the surface activity is very high and unstable when the metal surface is not oxidized, and the powder tends to agglomerate and become stable. The
Here, when the oxygen concentration in the Au—Sn alloy powder is less than 50 mass ppm, an oxide film cannot be formed on the surface of the Au—Sn alloy powder, and aggregation of the powder may not be suppressed. is there. On the other hand, when the oxygen concentration in the Au—Sn alloy powder exceeds 1800 ppm by mass, the meltability may be hindered.
From the above, in this embodiment, the oxygen concentration in the Au—Sn alloy powder is set in the range of 50 ppm to 1800 ppm by mass. The oxygen concentration in the Au—Sn alloy powder is preferably 50 mass ppm or more and 400 mass ppm or less, but is not limited thereto.

(Average particle size of Au-Sn alloy powder)
When the average particle diameter of the Au—Sn alloy powder is less than 1 μm, there is a possibility that poor melting occurs when the Au—Sn alloy solder paste 20 is heated. On the other hand, when the average particle diameter of the Au—Sn alloy powder exceeds 25 μm, the printability of the Au—Sn alloy solder paste 20 is deteriorated, and the flux and the Au—Sn alloy powder are separated to cause poor melting. There is a risk.
From the above, in this embodiment, the average particle diameter of the Au—Sn alloy powder is set in the range of 1 μm to 25 μm. The average particle diameter of the Au—Sn alloy powder is preferably 3 μm or more and 15 μm or less, but is not limited thereto.

(Flux content)
In the Au—Sn alloy solder paste 20, when the flux content is less than 5% by mass of the entire paste, the viscosity of the Au—Sn alloy solder paste 20 becomes too high, and the printability may be greatly reduced. . On the other hand, if the flux content exceeds 40% by mass of the entire paste, printing sag is likely to occur when printing the Au—Sn alloy solder paste 20 and the Au—Sn alloy powder is not sufficiently agglomerated during melting. May occur.
From the above, in this embodiment, the content of the flux is set within a range of 5% by mass or more and 40% by mass or less of the entire paste. Although it is preferable to make content of the said flux into 6 mass% or more and 25 mass% or less of the whole paste, it is not limited to this.
Here, as the flux, for example, a general flux (for example, a flux containing rosin, an activator, a solvent, a thickener, etc.) can be used. From the viewpoint of wettability of the Au—Sn alloy solder paste 20, it is preferable to use, for example, a weakly active (RMA) type flux, an active (RA) type flux, or the like.

Next, a method for manufacturing the Au—Sn alloy solder paste 20 according to the present embodiment will be briefly described.
First, an Au—Sn alloy powder containing Sn in a range of 61% by mass to 70% by mass with the balance being Au and inevitable impurities is prepared.

A molten Au—Sn alloy is obtained by weighing and melting the molten raw material so as to have the above-mentioned composition. This Au—Sn alloy molten metal is mechanically stirred while being kept at a predetermined temperature (eg, 700 to 800 ° C.).
As the mechanical stirring, for example, propeller stirring is preferable. Further, mechanical stirring and electrical stirring such as electromagnetic stirring may be used in combination. When propeller stirring is used as mechanical stirring, the rotation speed of the propeller can be set to, for example, 60 to 100 rpm. In this case, the stirring time can be, for example, in the range of 3 to 10 minutes.

Next, the above-mentioned Au—Sn alloy powder is manufactured by a gas atomization method using a molten Au—Sn alloy. Specifically, the pressure is applied to the above-mentioned molten Au—Sn alloy (for example, 300 to 800 kPa) while being derived from a small diameter nozzle (diameter 1 to 2 mm), and atomized gas is sprayed onto the molten Au—Sn alloy. Formed with.
As the spraying conditions, for example, the spraying pressure can be 5000 to 8000 kPa, and the nozzle gap can be 0.3 mm or less.

In this embodiment, the oxygen concentration in the produced Au—Sn alloy powder is controlled by using a mixed gas containing an inert gas and oxygen as the atomizing gas. That is, in this embodiment, the oxygen concentration in the atomized gas is adjusted so that the oxygen concentration of the produced Au—Sn alloy powder is in the range of 50 mass ppm to 1800 mass ppm.
When a gas having the same oxygen concentration is used, when a powder having a large particle size is produced, the specific surface area of the powder is small, so that the oxygen concentration in the powder is inevitably low. On the other hand, when a powder having a small particle size is produced, the specific surface area is increased, so that the oxygen concentration is increased. For this reason, it is necessary to adjust the oxygen concentration in the gas according to the target particle size and oxygen concentration of the powder.

Then, by classifying the Au—Sn alloy powder obtained by the gas atomization method described above, an Au—Sn alloy powder having an average particle size in the range of 1 μm to 25 μm is manufactured.

Next, the Au-Sn alloy solder paste 20 according to the present embodiment is manufactured by mixing the Au-Sn alloy powder and the flux at a predetermined mixing ratio. As a mixing method at this time, a planetary stirring method or a mechanical stirring method can be applied.

Next, a method for manufacturing the Au—Sn alloy solder layer 30 and the Au—Sn alloy solder layer 30 according to this embodiment will be described.
As shown in FIG. 2, the Au—Sn alloy solder layer 30 according to the present embodiment prints the Au—Sn alloy solder paste 20 according to the present embodiment on the substrate 11 on which the Au film 12 is formed. The Au—Sn alloy solder paste 20 is manufactured by heating and melting the Au—Sn alloy constituting the Au—Sn alloy solder paste 20 to a temperature not lower than + 30 ° C. and not higher than the liquidus temperature.
The Au film 12 preferably has a film thickness in the range of 0.01 μm to 0.1 μm. The Au film 12 can be formed by plating or the like.

Here, in the Au—Sn alloy solder paste 20 printed on the Au film 12, an Au—Sn alloy powder containing Sn in a range of 61 mass% to 70 mass% with the balance being Au and inevitable impurities is used. Contains. Therefore, according to the Au—Sn binary phase diagram shown in FIG. 1, the solidus temperature is 252 ° C. and the liquidus temperature is about 300 ° C. In the present embodiment, the MAX temperature in reflow at the time of joining is in the range of the solidus temperature to the liquidus temperature, preferably the solidus temperature + 30 ° C. to the liquidus temperature.

When heated to the above-mentioned temperature, a part of the printed Au—Sn alloy solder paste 20 is melted to form a sherbet, and the liquid Au—Sn spreads out. As a result, as shown in FIG. 2, a thin film phase 31 containing Sn as a main component and a thick film phase 32 in which the Au content is increased by the elimination of the Au—Sn component in the liquid phase are formed. .
And, in the thin film phase 31 mainly composed of Sn formed by wetting and spreading, the solidus temperature and the liquidus temperature are increased by reacting with the Au film 12 formed on the surface of the substrate 11, It solidifies while being kept at the heating temperature. In addition, the solidus temperature and the liquidus temperature also rise in the thick film phase 32 in which the Au content is relatively high due to the elimination of the Au—Sn component in the liquid phase.
The Au film 12 has a larger area than the printed Au—Sn alloy solder paste 20, and the thin film phase 31 formed by wetting and spreading the liquid Au—Sn sufficiently reacts with the Au film 12. Is configured to do.

As described above, the Au—Sn alloy solder layer 30 having a structure in which the thick film phase 32 having a high Au content is formed in the central portion and the thin film phase 31 mainly composed of Sn is formed around the thick film phase 32. Is formed.
Here, in the Au—Sn alloy solder layer 30 shown in FIG. 2, since the solidus temperature and the liquidus temperature of the thick film phase 32 and the thin film phase 31 are increased, the heat resistance is greatly improved.

According to the Au—Sn alloy solder paste of the present embodiment having the above-described configuration, the Au—Sn composition containing Sn in the range of 61 mass% to 70 mass% with the balance being Au and inevitable impurities. Since it has Sn alloy powder, according to the Au—Sn binary phase diagram of FIG. 1, the solidus temperature is 252 ° C., and it is possible to perform bonding even under relatively low temperature conditions. Further, according to the Au—Sn binary phase diagram of FIG. 1, since the liquidus temperature is about 300 ° C., the heat resistance of the formed solder alloy layer can be ensured.

Further, in this embodiment, since the oxygen concentration in the Au—Sn alloy powder is 50 mass ppm or more, an oxide film is formed on the surface of the Au—Sn alloy powder, thereby suppressing the aggregation of the Au—Sn alloy powder. It becomes possible to do. Thereby, the yield of Au-Sn alloy powder after classification can be improved. In addition, it is possible to suppress the occurrence of poor melting or printing failure of the Au—Sn alloy solder paste.
Furthermore, in this embodiment, since the oxygen concentration in the Au—Sn alloy powder is limited to 1800 mass ppm or less, the meltability is not adversely affected when mixed with the flux.

In this embodiment, since the average particle diameter of the Au—Sn alloy powder is in the range of 1 μm to 25 μm, the Au—Sn alloy powder is used when the Au—Sn alloy solder paste is melted after printing. Can be reliably melted, and printing defects and melting defects of the Au—Sn alloy solder paste can be suppressed.
Furthermore, in this embodiment, the flux content is in the range of 5% by mass or more and 40% by mass or less of the entire paste, so that the printability of the Au—Sn alloy solder paste is improved and the melting treatment is performed. It is possible to suppress insufficient aggregation of the Au—Sn alloy powder at the time.

Furthermore, in the manufacturing method of the Au—Sn alloy solder layer according to this embodiment, the Au—Sn alloy solder paste 20 according to this embodiment is printed on the base material 11 on which the Au film 12 is formed, and this Au -Since the Au-Sn alloy constituting the Sn alloy solder paste 20 is heated at a temperature not lower than the solidus temperature and not higher than the liquidus temperature, the wet thin film phase 31 reacts with the Au film 12 to cause the solidus line Since the solidus temperature and the liquidus temperature also rise in the thick film phase 32 as the temperature and the liquidus temperature rise, it is possible to form the Au—Sn alloy solder layer 30 with excellent heat resistance. It becomes.

In the present embodiment, a mixed gas containing an inert gas and oxygen is used as the atomizing gas used when producing the Au—Sn alloy powder, and the oxygen content in the atomizing gas is adjusted. Therefore, the oxygen concentration in the produced Au—Sn alloy powder can be controlled so as to be in the range of 50 ppm to 1800 ppm by mass.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, in this embodiment, although demonstrated as what is used when joining semiconductor elements, such as a LED element, and a circuit board, it is not limited to this, It may be used when joining other members. Good.

In this embodiment, the Au—Sn alloy solder paste printed on the substrate on which the Au film is formed is a liquidus line above the solidus temperature of the Au—Sn alloy constituting the Au—Sn alloy solder paste. Although described as heating at a temperature lower than the temperature, the present invention is not limited to this, and the above-described Au—Sn alloy solder paste is printed on the base material, and MAX at the time of reflow exceeding the normal liquidus temperature The Au—Sn alloy solder layer may be formed by heating to a temperature (eg, liquidus temperature +30 to 50 ° C.). Among the various mounted objects, for those in which thermal damage is a concern from the viewpoint of heat resistance, reflow MAX temperatures not lower than the solidus temperature and not higher than the liquidus temperature can be applied, and bonding of mounted objects having high heat resistance can be applied. Sometimes, the normal reflow MAX temperature, liquidus temperature + 30-50 ° C., can be applied.

Furthermore, in the present embodiment, the description has been made on the assumption that the Au—Sn alloy solder paste is disposed on the base material by the printing method. However, the present invention is not limited to this, and the Au— An Sn alloy solder paste may be disposed.
In the present embodiment, the Au film is formed by plating. However, the present invention is not limited to this, and the Au film may be formed by other means such as vapor deposition.

Hereinafter, the results of a confirmation experiment performed to confirm the effectiveness of the present invention will be described.

Au—Sn alloy powder having the composition shown in Table 1 was produced by the method described in the above embodiment.
Specifically, the melting raw material is weighed so as to have the composition shown in Table 1 and melted to form a molten Au—Sn alloy. The Au—Sn alloy is heated to 700 ° C. and stirred by propeller stirring. . The Au—Sn alloy molten metal was discharged from a small nozzle having a diameter of 1.5 mm under a pressure of 6000 kPa while pressurizing the molten Au—Sn alloy at 500 kPa. Au—Sn alloy powder was produced by spraying O ₂ ).

At this time, as shown in Table 1, the oxygen concentration of the Au—Sn alloy powder was controlled by adjusting the oxygen content in the atomizing gas. The oxygen concentration of the Au—Sn alloy powder was measured by an inert gas melting-infrared absorption method.
Further, the obtained Au—Sn alloy powder was subjected to air classification to adjust the average particle size of the Au—Sn alloy powder as shown in Table 1. The particle size of the Au—Sn alloy powder was measured by a laser diffraction method.

Here, the results of measuring the solidus temperature and the liquidus temperature of the obtained Au—Sn alloy powder by differential scanning calorimetry (DSC) are shown in Table 1.
The maximum temperature during heating was measured using a K thermocouple.
The obtained Au—Sn alloy powder and a flux (RA type) were mixed at a flux ratio of 10% by weight by a planetary stirring method to prepare an Au—Sn alloy solder paste.

A Ni film was formed by plating on a 2 mm square substrate made of Cu, and an Au film was further formed thereon. At this time, the thickness of the Au film was set to 0.05 μm.
On the Au film, the above-described Au—Sn alloy solder paste is printed to a thickness of 20 μm and a diameter of 600 μm, and a 1 mm square LED element is laminated, heated to the temperature shown in Table 1, and melted. An Sn alloy solder layer was formed and the LED element was joined.

Regarding the Au—Sn alloy solder paste and the Au—Sn alloy solder layer described above, presence or absence of aggregation of Au—Sn alloy powder, meltability after reflow, presence or absence of fear of thermal damage of LED elements, bonding of LED elements The heat resistance of the part was evaluated.
Regarding the agglomeration of the Au—Sn alloy powder, the presence or absence of lumps during paste formation was visually confirmed.
The meltability after reflow was observed with a stereomicroscope (20 times), and “poor” was given if the powder was not melted, and “pass” was given if it was not.
Regarding LED element thermal damage, if the mounting reflow temperature (maximum temperature during heating) is higher than 330 ° C, there is a high possibility of thermal damage. Was “B”, and those below 300 ° C. were “A”.
About the heat resistance of the junction part of an LED element, after joining an LED element, the presence or absence of the remelting at the time of reflowing again at the MAX temperature of 300 degreeC was observed with the reflow simulator (Video observation system made from Malcolm). The presence or absence of remelting was judged by observation of the movement of the LED element and the alloy part.
The evaluation results are shown in Table 2.

In Comparative Example 1, the Sn content in the Au—Sn alloy powder was 58 mass%, which was less than the range of the present invention. The solidus temperature measured using DSC was as high as 310 ° C., and the junction temperature had to be 340 ° C. or higher. There is a concern that the LED element is thermally damaged.
In Comparative Example 2, the Sn content in the Au—Sn alloy powder was 73 mass%, which was larger than the range of the present invention. The measurement of the solidus temperature using DSC was as low as 218 ° C., and the MAX temperature in reflow was 248 ° C., which is the solidus temperature + 30 ° C. It was judged that the formed Au—Sn alloy solder layer was insufficient in heat resistance because it was remelted by reflowing at 0 ° C.

In Comparative Example 3 and Comparative Example 4, the MAX temperature during heating was the solidus temperature + 9 ° C. and the solidus temperature + 24 ° C., which was lower than the range of the present invention where the solidus temperature + 30 ° C. or higher. Unmelted residue was generated in the reflowed powder, resulting in poor meltability.

In Comparative Example 5, since the oxygen concentration of the Au—Sn alloy powder was reduced to 30 mass ppm, which was less than the range of the present invention, it was possible to confirm the occurrence of lumps when pasted, and to suppress aggregation between the powders. could not. For this reason, unmelted residue was generated in the powder after reflow, and poor meltability occurred.
In Comparative Example 6, since the oxygen concentration of the Au—Sn alloy powder was 2200 mass ppm, which was larger than the range of the present invention, unmelted residue was generated in the reflowed powder, and poor melting occurred.

On the other hand, in the Au—Sn alloy solder paste and Au—Sn alloy solder layer of the present invention example, agglomeration of powders is suppressed, the meltability after reflow is excellent, and the heat damage property of the LED element is reduced. Without concern, the heat resistance of the joint portion of the LED element was obtained, and the LED element could be reliably joined.
In the inventive examples 1 to 7 in which the Au—Sn alloy solder paste printed on the Au film was heated at a temperature not lower than the solidus temperature and not higher than the liquidus temperature, the formed Au—Sn alloy solder layer The liquidus temperature was rising, melting was not observed even at 300 ° C., and it was confirmed to have high heat resistance. Further, FIG. 3 shows an observation photograph of the Au—Sn alloy solder layer formed by changing only the printing diameter of the paste using the same material and the same procedure as Example 2 of the present invention. An Au—Sn alloy solder layer 30 having a thin film phase 31 mainly composed of Sn that has spread and a thick film phase 32 having a relatively high Au content formed in the central portion is formed. It was confirmed.

From the results of the above confirmation experiment, according to the example of the present invention, an Au—Sn alloy solder paste that can form a solder layer that is excellent in meltability and has sufficient heat resistance even in bonding at relatively low temperature conditions, and It has been confirmed that an Au—Sn alloy solder layer can be provided.

According to the present invention, an Au—Sn alloy solder paste having excellent meltability and capable of forming a solder layer having sufficient heat resistance even when bonded at a relatively low temperature, and this Au—Sn alloy solder paste were used. An Au—Sn alloy solder layer manufacturing method and an Au—Sn alloy solder layer can be provided. According to the Au—Sn alloy solder layer manufacturing method using the Au—Sn alloy solder paste, the thermal damage to the mounted object can be reduced.

20 Au—Sn alloy solder paste 30 Au—Sn alloy solder layer

Claims (6)

1. An Au—Sn alloy powder containing Sn in a range of 61 mass% to 70 mass% with the balance being Au and inevitable impurities, and a flux,
   An Au—Sn alloy solder paste in which an oxygen concentration in the Au—Sn alloy powder is in a range of 50 mass ppm to 1800 mass ppm.
2. The Au-Sn alloy solder paste according to claim 1, wherein an average particle diameter of the Au-Sn alloy powder is in a range of 1 µm to 25 µm.
3. The Au-Sn alloy solder paste according to claim 1 or 2, wherein a content of the flux is in a range of 5 mass% to 40 mass% of the entire paste.
4. An Au-Sn alloy in which the Au-Sn alloy solder paste according to any one of claims 1 to 3 is disposed on a surface of a substrate, and the Au-Sn alloy solder layer is heated and melted. Solder layer manufacturing method.
5. The base material having an Au film formed on the surface is prepared, and the Au—Sn alloy solder paste is disposed on the Au film, and the Au—Sn alloy solder paste constituting the Au—Sn alloy solder paste is prepared. 5. The method for producing an Au—Sn alloy solder layer according to claim 4, wherein the Au—Sn alloy solder layer is melted by heating to a temperature of a phase line temperature of + 30 ° C. or more and a liquidus temperature of not more.
6. An Au-Sn alloy solder layer obtained by the method for producing an Au-Sn alloy solder layer according to claim 4 or 5.

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