JPS61113245A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent any unfavorable effect due to sustained molten state by the process not to leave already brazed semiconductor piece in molten state for a long time by a method wherein many wax layers with different melting points are formed on the same substrate to braze semiconductor pieces from the wax layer with higher melting point in order corresponding to the substrate temperature gradually lowered. CONSTITUTION:Two regions of a substrate 1 are metal-coated by means of baking metal paste to form spare wax layers 2, 3 thereon. The wax layer 2 selects wax with higher melting point than that of wax for the wax layer 3. The substrate 1 is mounted on a heated heat block 4 and after melting both spare wax layers 2, 3 the first semiconductor piece 5 is placed on the wax layer 2 to be brazed. Next the temperature of heat block 4 is gradually lowered. When the temperature of heat block 4 is lowered less than the melting point of layer 2, the layer 2 is solidified. Then the second semiconductor piece 6 is placed on the molten spare solder layer 3 to be brazed. At this time, any unfavorable effect such as deterioration in brazing strength due to advanced alloying of coated metal with semiconductor or solder may prevented from coming into since already solidified solder layer 2 may not be left in molten state for a long time.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to a method for manufacturing a semiconductor device in which a plurality of semiconductor pieces are brazed onto the same substrate.

[Prior art and its problems]

One possible method for fixing a plurality of semiconductor pieces on the same substrate is to use an adhesive, but this poses a problem in terms of reliability in power semiconductor devices where the temperature of the semiconductor pieces is expected to rise. On the other hand, the method of applying metal coating to the surface of a semiconductor piece and brazing it with solder or other wax is as follows.
It is necessary to heat the board, and when brazing the first semiconductor piece to another semiconductor piece, the solder is left in a molten state during the process, so when brazing a semiconductor piece, the metal on the surface Proceeding of alloying with the reward or wax may lead to deterioration of the bonding strength.

[Purpose of the invention]

The present invention eliminates the above-mentioned drawbacks, and when a plurality of semiconductor pieces are sequentially brazed onto a substrate, the charcoal chamber or brazing of the metal coating on the surface of the semiconductor piece that has been brazed first prevents the strength from decreasing. The purpose of the present invention is to provide a method for manufacturing a semiconductor device that can be manufactured using the following methods.

[Key points of the invention]

According to the present invention, a plurality of solder layer regions each having a different melting point are formed on a substrate, and in the process of increasing and then lowering the substrate temperature, semiconductor pieces are sequentially coated with metal starting from the solder layer region having a higher melting point. The above objective is achieved by sequentially solidifying the high melting point solder of the semiconductor piece that has been brazed first, while brazing the subsequent semiconductor piece with a low melting point solder. be done.

[Embodiments of the invention]

The present invention will be described below with reference to embodiments for two semiconductor pieces. A metal coating is applied to two areas of the ceramic substrate l shown in a cross-sectional view in FIG. 1 Ta+ and a plan view in FIG. 2 by baking a metal paste, and a preliminary brazing layer 2.
will be established. The wax in the preliminary wax layer 2 is the wax in the preliminary wax layer 3,
For example, solder with a higher melting point than 5a63% solder, such as S
Select 1% solder. Place this substrate 1 on a heated heat block 4, and after both preliminary solder layers 2 and 3 have melted, place the first semiconductor piece 5 on the solder layer 2 and braze. do. Then, the temperature of the heat block 4 is gradually lowered as shown in FIG. Temperature A indicates the melting point of the solder in the solder layer 2, and temperature B indicates the melting point of the solder in the solder layer 3. When the temperature of the heat block 4 is lower than A, the solder layer 2 becomes il.
[ffi. Here, the second semiconductor piece 6 is placed on the melted preliminary solder layer 3 and brazed. At this time, since the solder layer 2 has already solidified, it is not left in a molten state for a long time, and the solder layer 2 is not left in a molten state for a long time.
Brazing by progressing alloying of a metal coating such as /Ill/^U vapor deposited film or Nl/Au plating with a semiconductor or solder can prevent adverse effects such as a decrease in strength. In the above embodiment, there were two semiconductor pieces, but the present invention can be implemented in the same way when a larger number of semiconductor pieces are fixed on the same substrate by using solders having various melting points accordingly. . Also, it should be possible to implement it not only for ceramic substrates but also for metal substrates. Effects of the Invention The present invention forms a plurality of solder layers with different melting points on the same substrate, and brazes semiconductor pieces in order from the top of the solder layer with a higher melting point as the substrate temperature gradually decreases. Semiconductor pieces that have already been brazed are not left in a molten state for a long period of time, and adverse effects caused by the continuation of a molten state can be prevented. This method can also be applied to the automation of semiconductor mounting using a die bonder, etc., and the effects obtained are extremely large.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the manufacturing process of an embodiment of the present invention, Fig. 2 is a plan view corresponding to Fig. 1 (Fig.
It is a temperature course diagram of the heat block of a figure. 1: ceramic substrate, 2: high melting point solder layer, 3+low melting point solder layer, 4I heat block +5.6+ semiconductor piece. Figure 1 Time Figure 3

Claims (1)

[Claims] 1) When brazing multiple semiconductor pieces onto the same substrate, multiple solder layers with different melting points are formed on the substrate, and in the process of increasing and then lowering the substrate temperature, the wax with the higher melting point is used. 1. A method of manufacturing a semiconductor device, characterized in that semiconductor pieces are sequentially brazed from a layer region to surfaces provided with a metal coating.