JP2002283094A - Brazing filler metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brazing filler metal which does not produce the voids by an oxidized film admitted in a brazing filler metal made of a gold alloy. SOLUTION: This brazing filler metal is an alloy consisting of gold of Au/20Sn, Au/1 to 3.15Si, Au/12Ge as base and is subjected to gold plating of a thickness >=0.01 μm on its top and under surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing material used for joining various electronic parts and the like.

[0002]

2. Description of the Related Art Brazing materials having various metal compositions are widely used for joining electronic parts and the like. The brazing material is generally prepared by mixing a desired metal in a desired ratio, melting and alloying the metal, thinning it, then rolling it to a desired thickness, and finally finishing it into a predetermined shape by punching. ing. Among these brazing materials, those based on gold are common. For example, an Au / 20Sn alloy, an Au / 1 to 3.15Si alloy, and an Au / 12Ge alloy. These are appropriately selected and used depending on the purpose, the target metal to be joined, and the like.

[0003]

Since the above alloy is rolled to a predetermined thickness by warm working, for example, in the case of an Au / 20Sn alloy, a Sn oxide film layer is formed on the surface, so that the Au / 20Sn alloy is When melted, an Sn oxide film layer remains, and when the seal cover is joined, there is a problem that voids are generated and leak failure occurs. For example, in the case of Au / 1 to 3.15 Si alloy, oxidation of Si is caused on the surface. When a film layer is formed and the Au / 1 to 3.15 Si alloy is melted, an oxide film layer of Si remains and a void is generated in a bonding portion, resulting in insufficient heat conduction due to poor bonding. In the case of the 12Ge alloy, a Ge oxide film layer is formed on the surface, and when the Au / 12Ge alloy is melted, the Ge oxide film layer remains. There is a problem that occurs. An object of the present invention is to provide a brazing material that does not have the above-mentioned disadvantages.

[0004]

In order to solve the above-mentioned problems, the present inventor has made various studies. As a result, after removing an oxide film present on the surface of each alloy, gold plating is applied to the surface of each alloy. The present inventors have found that the above problems can be solved, and have reached the present invention.

That is, the brazing material of the present invention that solves the above-mentioned problems is an alloy based on gold, and at least the upper and lower surfaces thereof are plated with gold. The thickness of the gold plating is 0.01 μm or more, and preferably 5 μm or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The brazing material of the present invention has excellent oxidation resistance because at least the upper and lower surfaces are covered with gold,
No oxide of an additional metal such as Sn, Si, or Ge is generated on the surface covered with gold. Therefore, even when the semiconductor device is joined using the brazing material of the present invention, the defect due to the oxide of the additional metal does not substantially occur. The reason why it is substantial is that an oxide film is generated on the side surface of the brazing material at most, but the amount of oxide is within a range that does not hinder use.

[0007] In order to obtain the brazing material of the present invention, a composition is prepared using a desired metal, which is melted and alloyed, then thinned, and then rolled to a desired thickness. After removing the oxide film on the surface of the rolled material, gold plating is performed using the rolled material as a cathode, and then a desired shape is formed by punching or the like.

The gold plating layer is used to prevent oxidation of the surface of the brazing material from which the surface oxide film has been removed, and is effective if the thickness is 0.01 μm or more. As the thickness of the gold plating increases, oxidation can be prevented even when the gold plating is left for a long period of time. However, when the thickness is too large, productivity decreases. Further, since the possibility of a composition deviation increases, it is preferable that the thickness be 5 μm or less. If the composition shift occurs in the brazing material, the melting point of the brazing material increases, which is not preferable.

[0009]

Next, the present invention will be further described with reference to examples.

(Embodiment 1) The thickness of Au / 20Sn is 0.1 mm.
After the 050 mm foil is degreased and etched with hydrochloric acid, it is plated with gold having a thickness of 2 μm.
It was pressed into a washer-shaped gold-tin brazing material having an inner shape of 3 mm and a thickness of 0.030 mm. Using this, the semiconductor element was sealed in a ceramic package, and then the void generation area was examined by an X-ray transmission method. As a result, no void could be confirmed. Note that a conventional Au / 20Sn of this size is used.
Using a brazing material, the void generation area is about 2%.

(Example 2) Au / 20Sn sheet thickness
After the 050 mm foil was degreased and etched with hydrochloric acid, it was plated with gold having a thickness of 0.2 μm, then processed into a ribbon having a width of 2 mm and cut into a length of 2 mm to obtain a rectangular brazing material. Using this, a semiconductor element and a lower plate having a metallized layer for bonding the semiconductor element were joined. Thereafter, the void generation area was examined by the X-ray transmission method. As a result, no void could be confirmed.

(Embodiment 3) Au / 1Si plate thickness 0.04
After the foil of 0 mm is degreased and etched with hydrochloric acid, the surface is plated with gold Au having a thickness of 0.2 μm.
Then, it was pressed into a shape of 1 mm square and 0.040 mm thick to obtain a rectangular brazing material. The heat sink and the substrate were joined using this brazing material. Then, as a result of investigating the void generation area by the X-ray transmission method, no void could be confirmed. In the case of using a conventional Au / 1Si brazing material of this size, the void generation area is about 6%.

(Embodiment 4) Au / 1Si plate thickness 0.04
After degreasing the 0 mm foil and etching with hydrochloric acid, this surface is plated with gold of 0.2 micron thickness,
Then, it was processed into a ribbon having a width of 1.2 mm and cut into a length of 3 mm to obtain a rectangular brazing material. Using this, a semiconductor element and a lower plate having a metallized layer for bonding the semiconductor element were joined. Then, as a result of investigating the void generation area by the X-ray transmission method, no void could be confirmed. In the case of using a conventional Au / 1Si brazing material of this size, the void generation area is about 5%.

(Embodiment 5) Au / 2Si plate thickness 0.02
A 5 mm foil was degreased and etched with hydrochloric acid, and the surface was gold-plated with a thickness of 0.2 μm, then processed into a 5 mm wide ribbon and cut into a 3 mm length to obtain a rectangular brazing material. . Using this brazing material, a semiconductor element and a lower plate having a metallized layer for bonding the semiconductor element were joined. Then, as a result of investigating the void generation area by the X-ray transmission method, no void could be confirmed. In the case of using the conventional Au / 2Si brazing material of this size, the void generation area is about 5%.

(Example 6) A foil of Au / 3.15Si having a thickness of 0.050 mm was degreased and etched with hydrochloric acid, and then the surface thereof was plated with gold having a thickness of 0.2 μm and then 1.5 mm square. It was pressed into a 0.040 mm-thick shape to obtain a rectangular brazing material. As a result of bonding the heat sink and the substrate using the brazing material and then examining the void generation area by the X-ray transmission method, no void could be confirmed. In the case of using the conventional Au / 3.15Si brazing material of this size, the void generation area is about 6%.

(Embodiment 7) Au / 12Ge plate thickness 0.0
A 50 mm foil was degreased and etched with hydrochloric acid. The surface was gold-plated with a thickness of 0.2 μm, and then pressed into a 4 mm square and 0.050 mm thick shape to obtain a rectangular brazing material. . Using this brazing material, the heat sink and the substrate were joined, and thereafter, the void generation area was examined by the X-ray transmission method. As a result, no void could be confirmed. In the case of using a conventional Au / 12Ge brazing material of this size, the void generation area is about 5%.

(Embodiment 8) Au / 12Ge plate thickness 0.0
A 50 mm foil was degreased and etched with hydrochloric acid, and the surface was gold-plated with a thickness of 0.2 μm, then processed into a ribbon having a width of 2 mm and cut into a length of 2 mm to obtain a rectangular brazing material. . Using this brazing material, a semiconductor element and a lower plate having a metallized layer for bonding the semiconductor element were joined. Then, the void generation area was investigated by the X-ray transmission method. As a result, no void could be confirmed. In addition,
In the case of using a conventional Au / 12Ge brazing material of this size, the void generation area is about 5%.

[0018]

As described above, since the surface of the brazing material of the present invention is protected by gold plating and is not oxidized, no voids due to oxides are observed when used as a brazing material, and the yield is low. Is improved. Therefore, the present invention makes it possible to reduce the cost of assembling a semiconductor device.

Claims (5)

[Claims] 1. A brazing material comprising an alloy based on gold, and having at least an upper surface and a lower surface plated with gold having a thickness of 0.01 μm or more. 2. The brazing material according to claim 1, wherein the thickness of the gold plating is 5 μm or less. 3. The gold-based alloy is Au / 20Sn.
The brazing material according to claim 1, wherein 4. The gold-based alloy is Au / 1 to 3.
The brazing material according to claim 1, wherein the brazing material is 15Si. 5. The gold based alloy is Au / 12Ge
The brazing material according to claim 1, wherein