JPS63300519A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the void remaining in a solder material for preventing deterioration due to local overheating of a semiconductor chip together with improving reliability, by forming the die bonding surface of a heat sink into a tilting surface rising to a greater extent at the central part than at the edge part. CONSTITUTION:At the time of joining a semiconductor chip 11 with a heat sink 12, a solder material 14 comes to start to melt from the top 13a of the die bonding surface 13 of thin thickness, that is, form the vicinity of the central part. Then, a melting range of the solder material 14 slowly advances to the edge part of the die bonding surface 13 of thick thickness. Accordingly, the air in a gap lying between the semiconductor chip 11, the heat sink 12 and the solder material 14 before performing die bonding is slowly pushed out from the central part to the edge side of the die bonding surface 13 in company with a molten solder material 14 for being emitted to its outside, Further, the caking due to cooling of the solder material 14 gradually advances from the central part of thin thickness to the edge part of thick thickness so that the air does not trepass into this solder material 14.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention mainly relates to a semiconductor device formed by die-bonding a power semiconductor chip such as a power transistor to a heat sink, and particularly relates to the die-bonding structure thereof.

[Conventional technology]

Conventionally, as this type of semiconductor device, one having a cross-sectional structure as shown in FIG. 2 is known. This semiconductor device 1O consists of a semiconductor chip 1) and a heat sink 12, and the semiconductor chip 1) is die-bonded to a flat die bonding surface 13 formed on the heat sink 12 by soldering. In addition, the code 1 in the figure
4 is between the semiconductor chip 1) and the heat sink 12,
It shows solder material interposed with a uniform thickness.

Such a die bonding structure is generally formed by melting the solder material 14 by heating from the heat sink 12 side in a reducing atmosphere. That is, during die bonding, substantially the entire surface of the semiconductor chip 1) is simultaneously soldered to the die bonding surface 13 of the heat sink 12 using the molten solder material 14.

[Problem that the invention seeks to solve]

By the way, before die bonding is performed in the semiconductor device i1Q having the above structure, there are many gaps (not shown) between the semiconductor chip 1), the heat sink 12, and the solder material 14, and these gaps have Air exists. Therefore, the die bonding structure in this semiconductor device 1fflo has the following problems.

That is, although the solder material 14 of this semiconductor device 10 is melted by heating during die bonding, this solder material 14
has a uniform thickness, and since the solder material 14 rapidly and simultaneously melts over almost the entire surface by heating, there is not enough room for the aforementioned air to be pushed out and released from the die bonding surface 13. This air is taken into the solder material 14 that has solidified again by cooling, and remains as so-called voids. As a result, the heat generated by the semiconductor chip 1), which should be dissipated to the outside through the heat sink 12 when the semiconductor device 10 is used, is difficult to be transmitted to the heat sink 12.

As a result, the semiconductor chip 1) deteriorates due to local overheating, resulting in reduced reliability.

The present invention has been made to solve these conventional problems, and aims to provide a semiconductor device that can prevent deterioration of semiconductor chips and improve reliability.

[Means for solving problems]

In order to achieve the above object, the present invention is characterized in that the die bonding surface of the heat sink is formed as an inclined surface that is raised from the edge toward the center.

[Effect]

In this invention, since the die bonding surface of the heat sink is formed as a convex inclined surface, the thickness of the solder material interposed between the die bonding surface and the semiconductor chip placed thereon is as follows: Therefore, the melting and solidification of the solder material during die bonding work is
First, it starts near the center of the die bonding surface of the heat sink and gradually moves toward the edges. Therefore, the air present between the semiconductor chip, the heat sink, and the solder material is successively pushed out and released to the outside.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a schematic cross-sectional view showing the configuration of a semiconductor device according to the present invention. In this embodiment, there is nothing different from the conventional example shown in FIG. 2 except for the shape of the die bonding surface of the heat sink, so parts in FIG. 1 that correspond to those in FIG. 2 are given the same reference numerals. The explanation here will be omitted.

Reference numeral 10 in FIG. 1 is a semiconductor device, and this semiconductor device 10 includes a power semiconductor chimp 1) that generates a large amount of heat during use, and a heat sink 12 made of a copper-based metal or the like as a heat sink thereof. The die bonding surface 13 of the heat sink 12 is formed in, for example, a conical shape, which is gently raised toward the center from the edge, and the die bonding surface 13 of the heat sink 12 is formed in a conical shape, for example, and is in contact with the apex 13a of the die bonding surface 13 of the semiconductor chip.
) is now placed. Note that this raised shape is not limited to a conical shape (or may be a pyramidal shape, etc.).Alternatively, the apex 13a may be a ridge line along one direction (in the figure, the vertical direction of the paper surface). , and may have a shape such as a "mountain" shape with gently sloped hem portions on both sides f1).

Then, the die bonding surface 1 of this heat sink 12
A solder material 14 is interposed between the die bonding surface 13 and the semiconductor chip 1), and the thickness of the solder material 14 is greater at the edge than at the center, corresponding to the shape of the die bonding surface 13. It gets thicker towards the sides.

Next, die bonding in this example will be explained.

The solder material 14 of this semiconductor device 10 is similar to the conventional example,
The semiconductor chip 1) is melted by heating from the heat sink 12 side, and the semiconductor chip 1) and the heat sink 12 are bonded together. However, as described above, the thickness of the solder material 14 corresponds to the shape of the die bonding surface 13 of the heat sink 12, which is formed in a convex shape, and becomes thicker from the center to the edge. , this solder material 14 starts to melt from the apex 13a1 of the thin die bonding surface 13, that is, near the center.The melting range of the solder material 14 is as follows. Therefore, before die bonding, the semiconductor chip 1), the heat sink 12 and the solder material 14 are
As the solder material 14 melts, the air in the gap between the die bonding surface 13 is gradually pushed out from the center of the die bonding surface 13 toward the edge, and is discharged to the outside.

On the other hand, the solidification of the solder material 14 due to cooling progresses gradually from the thinner center to the thicker edges, similar to its melting, so that air may not enter into the solder material 14. There isn't.

〔Effect of the invention〕

As explained above, according to the present invention, the die bonding surface of the heat sink to which the semiconductor chip is die-bonded is formed as an inclined surface that is more raised toward the center than the edges, so that the solder that is interposed between these surfaces is The thickness of the material is thicker at the edges than at the center, corresponding to the shape of the die bonding surface.

Therefore, the melting and solidification of the solder material during die bonding starts from near the center of the die bonding surface of the heat sink and gradually progresses toward the edge due to the difference in thickness.

As a result, the air present between the semiconductor chip, the heat sink, and the solder material is successively pushed outward by the melted solder material and is emitted to the outside. As a result, the number of voids remaining in the solder material of the semiconductor device of the present invention is significantly reduced compared to the conventional example.

Therefore, the thermal conductivity between the semiconductor chip and the heat sink is significantly improved, and it is possible to prevent deterioration of the semiconductor chip due to local overheating and to improve reliability.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a semiconductor device according to a conventional example. In the figure, reference numeral 1 is a semiconductor device, 1) is a semiconductor chip, 12 is a heat sink, 13 is a die bonding surface thereof, and 14 is a solder material. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A semiconductor device formed by die-bonding a semiconductor chip to a heat sink, characterized in that the die-bonding surface of the heat sink is formed as an inclined surface that is more raised toward the center than at the edges.