JP4556901B2 - Gold alloy solder ball manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing gold alloy solder balls in a large amount with little variation in shape and size.

  In general, Pb—Sn alloy solder balls are used for bonding a semiconductor element such as a GaAs optical element, a GaAs high frequency element, and a heat transfer element to a substrate. As shown in FIG. 2B, the Pb—Sn alloy solder ball is formed on the surface of the silicon substrate 1 in which the recesses 2 having a uniform shape are formed on the surface, as shown in FIG. The Pb—Sn alloy solder paste 3 is filled and then reflowed. As shown in FIG. 2 (c), the Pb—Sn alloy solder powder contained in the Pb—Sn alloy solder paste 3 melts and aggregates in the recesses 2 to form spherical Pb—Sn alloy solder balls. 4. Thereafter, the flux adhering to the Pb—Sn alloy solder ball is removed by a normal cleaning method to produce a Pb—Sn alloy solder ball (see Patent Document 1).

In recent years, the use of Pb—Sn alloy solder is restricted because Pb, which is a harmful substance, is the main component, and its use is about to be prohibited. For this reason, lead-free solder tends to be mainly used. For bonding a semiconductor element such as a GaAs optical element, a GaAs high frequency element, and a heat transfer element to a substrate, an Au—Sn alloy solder ball or an Au—Ge solder ball is used. Au alloy solder balls have been used. The Au—Sn alloy solder ball contains Sn: 15 to 25% by mass, and the remainder is known to have a composition consisting of Au and inevitable impurities. The Au—Ge solder ball has Ge: 5 to 15 mass. It is also known that the composition has a composition composed of Au and inevitable impurities.
Japanese Patent Laid-Open No. 9-150290

  However, when a silicon substrate having a uniform recess formed on the conventional surface is used and the gold alloy solder paste is filled in the recess and then reflowed, the molten gold alloy solder is a large gold alloy in the center of the recess. Although a solder ball is generated, a fine gold alloy solder ball is formed around a larger gold alloy solder ball by adhering to the wall surface of the recess, and therefore a gold alloy solder ball having a uniform size cannot be obtained. In addition, there is a disadvantage in that it is expensive to form a recess having a smooth surface and a uniform shape on a silicon substrate.

Therefore, the present inventors have studied to obtain a large amount of gold alloy solder balls having a uniform shape at a low cost. as a result,
(B) A gold alloy solder containing Sn: 15 to 25% by mass, the balance being composed of Au and inevitable impurities, and Ge: 5 to 15% by mass, and the balance being composed of Au and inevitable impurities The molten gold alloy solder obtained by melting the gold alloy solder having a large amount of Au, so that the surface tension is large, and it is easy to become a spherical ball,
(B) The molten gold alloy solder is more easily formed into a spherical shape having a uniform shape when placed on an alumina substrate than a silicon substrate, and is simply formed on an alumina flat plate;
(C) The smoother the surface of the alumina substrate, the lower the wettability with respect to the molten gold alloy solder. Therefore, it is preferable that the surface of the alumina substrate is 0.05 μm or less. This knowledge was obtained.

This invention was made based on such knowledge,
(1) Surface roughness: A coated plate made of a flat plate having a through hole penetrating in the thickness direction is placed on an alumina substrate made of a flat surface having a surface smoothness of 0.05 μm or less, and gold is placed in the through hole. A gold alloy solder ball that is filled with an alloy solder paste, removes the cover plate having the through-holes, leaves the gold alloy paste on the alumina substrate, and then reflows the gold alloy paste remaining on the alumina substrate. The manufacturing method is characterized.

  A method for producing a gold alloy solder ball according to the present invention will be specifically described with reference to FIG. First, an alumina substrate 5 made of a flat plate having a surface roughness of 0.05 μm or less is prepared. As shown in FIG. 1A, a covering plate 7 made of a flat plate having a through hole 6 penetrating in the thickness direction is placed on the smooth substrate 5 made of alumina. After filling the through hole 6 with a generally known Au alloy solder paste 8 as shown in FIG. 1 (b), the covering plate 7 having the through hole 6 is removed as shown in FIG. 1 (c). Then, when the gold alloy paste 8 is left on the alumina substrate 5 and then the gold alloy paste 8 remaining on the alumina substrate is reflowed, the surface smooth alumina substrate as shown in FIG. A spherical gold alloy solder ball 9 having a uniform shape is formed thereon.

In the method of filling the through hole 6 of the covering plate with the gold alloy solder paste, the gold alloy solder paste is printed from above the covering plate 7 having the through hole 6 mounted on the alumina substrate 5. Filling the through hole with the gold alloy solder paste can be more efficiently filled. Therefore, the present invention
(2) The gold according to (1), wherein the gold alloy solder paste is filled into the through hole by printing the gold alloy solder paste from the cover plate having the through hole placed on the alumina substrate. It has the characteristics in the manufacturing method of an alloy solder ball.

  The Au alloy solder paste used in the method for producing a gold alloy solder ball according to the present invention includes an Au alloy solder powder obtained by atomization, a flux composed of a commercially available rosin, an activator, a solvent and a thickener, and 5 to 15 mass. %, Or an Au alloy solder paste manufactured by Mitsubishi Materials Corporation obtained by mixing an Au alloy solder powder obtained by atomization and a non-halogen flux.

  The reason why the surface roughness of the alumina substrate used in the method for manufacturing a gold alloy solder ball of the present invention is specified to be 0.05 μm or less is that the smaller the surface roughness of the alumina substrate, the smaller the grain size of the gold alloy solder ball manufactured. This is preferable because the variation in diameter is small, but when the surface roughness of the alumina substrate exceeds 0.05 μm, fine gold alloy solder balls are generated around the large gold alloy solder balls, and the manufactured gold alloy This is because the shape and dimensions of the solder balls are not preferable. “Surface roughness” as used herein indicates Ra (arithmetic average height) defined by JISB0601, and Ra (μm) calculated with a cutoff value λc: 0.25 and an evaluation length Ln: 1.25 mm. It is.

  According to the method of the present invention, the gold alloy solder balls can be manufactured with a uniform shape and no variation in dimensions as compared with the conventional method. Furthermore, the method of the present invention uses a flat plate as a substrate, so that the manufacturing cost is low. Can be suppressed.

Example 1
Alumina substrates made of flat plates with different surface roughness shown in Table 1 were prepared. Furthermore, a SUS304 stainless steel covering plate having a through hole with a diameter of 1 mm and a thickness of 0.05 mm was prepared. Furthermore, an Au—Sn alloy solder paste manufactured by Mitsubishi Materials Corporation, in which a non-halogen flux was mixed with Au—Sn alloy solder powder containing Sn: 20% by mass and the balance consisting of Au and inevitable impurities, was prepared.

  The SUS304 stainless steel coating plate having a through hole with a diameter of 1 mm and a thickness of 0.05 mm was placed on an alumina substrate having different surface roughness shown in Table 1, and the stainless steel coating was applied. The gold alloy solder paste manufactured by Mitsubishi Materials Co., Ltd., which was prepared in advance from the top of the plate, was filled in the through hole, and the SUS304 stainless steel covering plate was removed. After heating at 4 ° C / min, temperature: held at 150 ° C for 60 seconds, further heating rate: heated at 4 ° C / min, temperature: maintained at 320 ° C for 30 seconds, and then washed. By drying, the present invention methods 1 to 5 and comparative method 1 were carried out, and 1000 Au-Sn alloy solder balls were produced. Thirty of the 1,000 Au—Sn alloy solder balls respectively produced by the present invention methods 1 to 5 and comparative method 1 are arbitrarily taken out, and the average of the maximum diameters of the 30 Au—Sn alloy solder balls respectively. The value X and the average value Y of the minimum diameters were measured, and the difference (X−Y) was determined as the shape variation of the Au—Sn alloy solder balls. The results are shown in Table 1.

Conventional Example 1
A silicon substrate having 1000 depressions with a uniform shape formed on the surface was prepared, and the Au-Sn alloy solder paste prepared in Example 1 was filled in the depressions, and then reflow treatment was performed under the same conditions as in Example 1. Then, the conventional method 1 was carried out by washing and drying, thereby producing 1000 Au—Sn alloy solder balls. 30 of the 1000 Au—Sn alloy solder balls manufactured by the conventional method 1 are arbitrarily taken out, and the average value X of the maximum diameter and the average value Y of the minimum diameter of the Au—Sn alloy solder balls are measured. The difference (XY) of the average values was determined as the variation in the shape of the gold alloy solder balls, and the results are shown in Table 1.

Example 2
An Au—Ge alloy solder paste manufactured by Mitsubishi Materials Co., Ltd. prepared by mixing non-halogen flux with an Au—Ge alloy solder powder having a composition containing Ge: 12% by mass and the balance consisting of Au and inevitable impurities is prepared. The gold alloy solder paste was filled in the through hole of the stainless steel coating plate placed on the alumina substrate in the same manner as in Example 1 using the -Ge alloy solder paste, and the SUS304 stainless steel coating plate was removed. Then, after heating at a heating rate of 4 ° C./min, the temperature is maintained at 250 ° C. for 60 seconds, and after heating at a heating rate of 4 ° C./min, the temperature is maintained at 380 ° C. for 30 seconds. The present invention methods 6 to 10 and comparative method 2 are carried out by performing the treatment, and then washing and drying, and each of the Au—Ge alloy solder balls is 100 Pieces at a time to prepare. Thirty of the 1,000 Au—Ge alloy solder balls respectively produced according to the present invention methods 6 to 10 and comparative method 2 are arbitrarily taken out, and the average of the maximum diameters of the 30 Au—Ge alloy solder balls, respectively. The value X and the average value Y of the minimum diameters were measured, and the difference (X−Y) was determined as the shape variation of the Au—Ge alloy solder balls. The results are shown in Table 2.

Conventional example 2
A silicon substrate having 1000 depressions with a uniform shape formed on the surface was prepared, and the Au-Ge alloy solder paste prepared in Example 2 was filled in the depressions, and then reflow treatment was performed under the same conditions as in Example 2. Thereafter, the conventional method 2 was carried out by washing and drying, thereby producing 1000 Au—Ge alloy solder balls. 30 of the 1000 Au—Ge alloy solder balls manufactured by the conventional method 2 are arbitrarily taken out, and the average value X of the maximum diameter and the average value Y of the minimum diameter of the Au—Ge alloy solder balls are measured. The difference (XY) of the average values was determined as the variation in the shape of the gold alloy solder balls, and the results are shown in Table 2.

From the results shown in Tables 1 and 2, the gold alloy solder balls obtained by the present invention methods 1 to 10 are shaped as compared with the gold alloy solder balls obtained by the conventional methods 1 and 2 and the comparison methods 1 and 2. From the fact that the variation is small, it can be seen that a gold alloy solder ball having a more spherical shape can be obtained.

It is sectional explanatory drawing for demonstrating the manufacturing method of Au alloy solder ball of this invention. It is sectional explanatory drawing for demonstrating the manufacturing method of the conventional Au alloy solder ball.

Explanation of symbols

1: Silicon substrate, 2: Depression, 3: Pb—Sn alloy solder paste, 4: Pb—Sn alloy solder ball, 5: Alumina substrate, 6: Through hole, 7: Cover plate, 8: Au alloy solder paste , 9: Gold alloy solder balls

Claims (4)

Surface roughness: A coated plate made of a flat plate having a through hole penetrating in the thickness direction is placed on an alumina substrate made of a flat plate having a smooth surface of 0.05 μm or less, and a gold alloy solder paste is placed in the through hole. The gold alloy paste is removed by removing the covering plate having the through holes and leaving the gold alloy paste on the alumina substrate, and then reflowing the gold alloy paste remaining on the alumina substrate. Solder ball manufacturing method. 2. The gold alloy solder paste is filled in the through hole by printing a gold alloy solder paste on a cover plate having a through hole placed on the alumina substrate. Manufacturing method of gold alloy solder balls. 3. The method for manufacturing a gold alloy solder ball according to claim 1, wherein the gold alloy solder paste contains Sn: 15 to 25 mass%, and the balance is made of Au and inevitable impurities. 3. The method for manufacturing a gold alloy solder ball according to claim 1, wherein the gold alloy solder paste contains 5 to 15 mass% of Ge, and the balance is made of Au and inevitable impurities.

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