JPS6354223B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor device, and more particularly to an assembly structure of a power semiconductor device in which a semiconductor element is attached to a heat sink.

[Technical Background of the Invention] A conventional hybrid IC module is shown in FIG. The envelope 1 includes a frame-shaped case body 2, a lid-like cover 3 that closes one open end of the case body, and a base 4 that is in close contact with the other open end of the case body and on which a unit to be described later can be attached.
Terminals 5, 5, . . . are provided on the outside of the envelope. Next, a power subunit 6, a control unit 7, etc. are disposed on the main surface inside the envelope of the base, and the envelope is further filled with a gel-like resin (not shown).

Since this invention consists in improving the above-mentioned power subunit 6, the conventional structure of this section will be explained with reference to FIG. A ceramic substrate is usually used as the insulating plate 8, and a heat sink 9 is laminated thereon, and the heat sink is a copper plate plated with nickel. A semiconductor element 10, which is a power transistor chip, is attached to the heat sink, and some electrodes of the semiconductor element are led out by bonding wires 11, 11, . . . . Further, the heat sink 9 is provided with a pad 12 for drawing out the collector lead of the semiconductor element. The bonding of the semiconductor element to the heat sink and the bond between the heat sink and the insulating plate are both accomplished by soldering, and FIG. 2b shows the solder layers 13, 13.

When attaching a semiconductor element that generates a large amount of heat, such as a power transistor, using the above solder joint,
It is necessary to give sufficient consideration to heat dissipation. This is because the solder layer has a relatively high thermal resistance, and it is desirable to make the thickness of the solder layer as thin as possible. but,
When the solder layer thickness is small, stress generated due to the difference in thermal expansion coefficient between the semiconductor element and the heat sink is applied to the semiconductor element, causing cracking, deterioration of element characteristics, etc. Furthermore, it is known that stress is applied to the solder layer, which tends to cause deterioration of the solder.

As mentioned above, controlling the thickness of the solder layer has become a very important factor in extending the life and characteristics.

[Problems with background technology]

Empirically, the solder layer thickness between the semiconductor element and the heat sink is targeted to be about 40 to 50 μm, but to achieve this, the amount of solder supplied and the weight (pressure) applied to the semiconductor element when melting the solder have to be adjusted. Although the solder layer thickness was controlled, there were various problems such as variations in the solder layer thickness, the semiconductor element becoming non-horizontal with the top surface of the heat sink, and misalignment.

One of the reasons for the above is that even if the amount of solder supplied is constant, the solder does not accumulate directly under the semiconductor element due to its structure, so the amount of solder flowing out from directly below to the side cannot be controlled. .

Therefore, when soldering semiconductor elements,
Although it is effective to use heat sinks made of molybdenum plates or beryllium plates, which have thermal expansion coefficients close to those of semiconductor elements, they both have the disadvantage of being expensive, so there is a strong demand for an improved structure using the above-mentioned general heat sinks. It had been.

[Purpose of the invention]

The present invention has been made to improve the above-mentioned conventional problems and meet the demands, and provides an improved structure in which the thickness of the solder layer that joins the semiconductor element and the heat sink is constant.

[Summary of the invention]

In the semiconductor device according to the present invention, a recess having an area smaller than the main surface of the semiconductor element is provided on the semiconductor element mounting surface, and the recess is filled with a bonding material to bond the semiconductor element, and the semiconductor element is connected to the recess and the semiconductor element is connected to the recess. The device is characterized in that it includes a bonding material storage recess that is formed to extend laterally from directly below the element. Next, a recess is provided in the heat sink for fixing the semiconductor element in the correct position, another recess is provided at the bottom of this recess to be filled with bonding material, and this recess is further extended laterally from directly below the semiconductor element for bonding. It is characterized by having a recess for storing material.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained in detail with reference to the drawings.

In FIG. 3 showing the bonding structure between the semiconductor element and the heat sink of the power subunit of the first embodiment, 21
22 is a heat sink, which is a copper plate plated with nickel, and 22 is a recess formed in the semiconductor element mounting portion of the heat sink to be smaller than the main surface of the semiconductor element; this recess is filled with solder; A semiconductor element 10 is attached to cover the recess. This semiconductor element has four corner parts 1 as shown in the figure.
0a is closely and stably fixed to the upper surface of the heat sink 21. The solder 23 is a bonding material for bonding the semiconductor element to the heat sink, and this solder fills the recess 22a directly below the semiconductor element, and
The recess fills a bonding material storage recess 22b extending laterally from directly below the semiconductor element.

As shown in FIG. 4, the solder is supplied in advance by being cut into plate shapes that are slightly thicker than the depth of the recess and of a size that can be freely inserted into the recess. By placing the semiconductor element in a predetermined position, the semiconductor element is placed on the solder plate.
Next, a fixing peg is placed on the semiconductor element, and the semiconductor element is placed in a hydrogen furnace or the like to melt the solder. When the solder melts, the semiconductor element slightly descends and comes into close contact with the top surface of the heat sink at its four corners. Then, it is removed from the oven and allowed to slowly cool. As the solder gradually begins to solidify, its volume shrinks, but since there is a recess for storing the bonding material that extends laterally from just below the semiconductor element, the shrinkage force due to volume reduction is dispersed, and the semiconductor element itself does not No large stress occurs.

As an example, the recessed portion may be 50 μm in size, and can be provided at the same time when the heat sink is punched and formed, so that the number of man-hours in the manufacturing process does not increase and there is no decrease in efficiency.

5A to 5C each show a different embodiment, and in the figures, 22 represents a recess, 22b represents a recess for storing a bonding material, and 23b represents a solder layer in the recess for storing a bonding material.

Next, one embodiment of the second invention of the present application will be described in detail with reference to FIG. 6 and subsequent figures. In the figure, 21 is a heat dissipation plate, 31 is a first recess provided in a fixed position for mounting the semiconductor element 10, and a second rectangular recess 32 smaller than the main surface of the semiconductor element is formed at the bottom of this recess. ing. When the solder 33 is placed in advance in this second recess using a solder piece formed in the shape of a foil and slightly thicker than the depth of the recess, and the semiconductor element 10 is placed on the solder 33, the semiconductor element first moves into the first recess 31. When the solder melts, the four corners of the semiconductor element come into contact with the bottom surface of the first recess 31 and are fixed in position. In this case, with the solder 33 in the second recess 32, the solder 33a at the bottom of the semiconductor element contributes to the attachment of the semiconductor element, and the solder 33b at the side of the semiconductor element (crosshatched in FIG. 6) contributes to the attachment of the semiconductor element. ) is the solder layer in the bonding material storage recess 32b.

〔Effect of the invention〕

According to this invention, the thickness of the bonding material layer disposed below the semiconductor element can be made constant by the recess, and the surplus amount of the bonding material can be released from directly below the semiconductor element by the bonding material storage recess. It is effective to store it.

Next, the second invention further improves the above invention by providing a second recess for orienting the semiconductor element.

As described above, the quality of semiconductor devices formed has been significantly improved, the manufacturing process has been automated, and the process yield has been improved.

[Brief explanation of the drawing]

Figure 1 is a perspective view for explaining the assembly of a hybrid IC module, Figure 2 is a perspective view of the power subunit in Figure 1, Figure a is a perspective view, Figure b is a sectional view, and Figure 3 is a diagram of the present invention. FIG. 4 is a perspective view for explaining the configuration of FIG. 3, and FIGS. Each of FIGS. 6 to 8 is a top view showing another embodiment of the present invention, FIG. 6 is a top view, and FIG. 7 is a top view taken along the line AA' in FIG. 6. Sectional view in the viewing direction, No. 8
The figure is a cross-sectional view of the portion circled by a broken line in FIG. 6. DESCRIPTION OF SYMBOLS 10... Semiconductor element, 10a... Four corners of semiconductor element, 21... Heat sink, 22a... Recessed part just below semiconductor element, 22b... Recessed part for bonding material storage (recessed part on the side of semiconductor element), 23a... Solder layer just below semiconductor element ,
23b...Solder layer in the recess for bonding material storage, 31...First recess, 32a...Second recess directly below the semiconductor element, 32b...Recess for bonding material storage, 33a...Solder layer in the second recess, 33b... Solder layer in the recess for storing bonding material.

Claims (1)

[Scope of Claims] 1. In a semiconductor device in which one main surface of a semiconductor element is bonded to a heat sink using a bonding material, a recess formed in a semiconductor element mounting portion of the heat sink that is smaller than the main surface of the semiconductor element. a bonding material filled in the recess, a semiconductor element bonded to the heat sink by the bonding material, and a recess for storing the bonding material that communicates with the recess and extends laterally from directly below the semiconductor element. A semiconductor device comprising: 2. In a semiconductor device in which one principal surface of a semiconductor element is bonded to a heat sink using a bonding material, a first recess for fixing the semiconductor element in a fixed position in a semiconductor element attachment portion of the heat sink, and the first recess. a second recess formed at the bottom to be smaller than the main surface of the semiconductor element; a bonding material filled in the second recess; and a first recess formed by the bonding material.
A semiconductor device comprising: a semiconductor element bonded to the recess; and a bonding material storage recess communicating with the second recess and extending laterally from immediately below the semiconductor element.