JPH03290952A - Semiconductor package - Google Patents

Abstract

PURPOSE:To prevent the breakdown of solder balls by constructing a solder- joined part by soldering a spacer which has a thermal expansion coefficient being equal to the one of a base and a cap in the direction parallel with a soldering face and to the one of the balls in the direction vertical to the face. CONSTITUTION:A spacer 7 is put in a solder-joined part between a cap 4 and a base 3 so that a solder material or the like 5 is thereby divided in the direc tion of the thickness thereof. For the spacer 7, a laminated body of an anisotropic material or the like which has about the same thermal expansion coefficient as the solder material in the direction vertical to a soldering face and has a low thermal expansion coefficient being equal to the one of a package material in the direction parallel with the soldering face. Since the thickness of each solder material 5 is made small according to this constitution, the airtightness of the solder material 5 can be maintained with the amount of thermal expansion in the vertical direction of a package matched with that of balls 2. Accordingly, the breakdown of the solder balls can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor package having a hermetically sealed structure, and particularly to a semiconductor package suitable for preventing breakage of solder balls connecting an internal semiconductor and a substrate. Regarding.

[Conventional technology]

The conventional semiconductor hermetically sealed package was published in Japanese Patent Application Laid-open No. 62-249.
The explanation will be given using the one described in Japanese Patent No. 429 as an example. A conventional semiconductor hermetically sealed package has an LS as shown in Figure 11.
II to a wiring board 3 made of ceramics etc. with solder balls 2
There is an electrical connection to the A lid 4 is bonded to the wiring board 3 with a sealing brazing material 5, and S11 and solder balls 2 are placed inside. When the amount of heat generated by this LSII is large, this LSII is fixed to the lid 4 made of a material with high thermal conductivity with a bonding brazing material 6, and the heat generated by the LSII is transferred to the lid 4.
The heat is conducted to and dissipated. The reason why ceramics are used as the material for the wiring board 3 is because of their airtightness, corrosion resistance, insulation, heat resistance, etc.
A feature directly relevant to the present invention is low thermal expansion. L
Semiconductors such as SI are often made of materials with low thermal expansion coefficients and low strength, such as Si and GaAs, so packaging materials for lids, wiring boards, etc. that bond these semiconductors are made by materials with a thermal expansion coefficient of the semiconductor and package material. In order to prevent destruction of the semiconductor due to differential thermal stress, a material with a low coefficient of thermal expansion is required, and ceramics, for example, are suitable for this purpose.

[Problem to be solved by the invention]

A state in which a temperature change occurs in the semiconductor package having the structure shown in FIG. 11 will be explained, and problems with the conventional package will be shown. As mentioned above, the package formed by joining the wiring board and the lid uses a material with low thermal expansion that matches that of a semiconductor, such as ceramics, so even if a temperature change occurs, thermal deformation does not occur much. On the other hand, the LS bonded to the lid
Since the solder ball restrained between I and the wiring board has a large coefficient of thermal expansion, it causes large thermal deformation.

For this reason, for example, when the temperature drops, the solder balls shrink due to heat even though the package hardly shrinks, causing the solder balls to be stretched upward and downward from the package, and when the temperature changes are large, the solder balls break. Sometimes. This conventional structure had such problems.

A first object of the present invention is to provide a semiconductor package that prevents the destruction of solder balls connecting a semiconductor and a substrate, and a second object of the present invention is to provide a semiconductor package that prevents the destruction of the solder balls. Our goal is to provide computers equipped with

[Means to solve the problem]

In order to achieve the above-mentioned first object, a semiconductor package of the present invention includes a lid having a semiconductor bonded to the inner surface, a substrate bonded to the semiconductor via a solder ball, and a peripheral edge of the surface of the substrate. In a semiconductor package whose interior is hermetically sealed by a brazing joint formed between a brazing surface and the lid, the brazing joint is formed between the substrate and the lid in a direction parallel to the brazing surface. It is characterized in that a spacer having a coefficient of thermal expansion substantially equal to that of the lid and having a coefficient of thermal expansion equal to that of the solder ball in a direction perpendicular to the brazing surface is brazed at both ends thereof.

In the semiconductor package of the present invention, the spacer is constituted by a laminate in which plate materials having a small coefficient of thermal expansion and brazing layers having approximately the same coefficient of thermal expansion as the solder balls are alternately provided, and the total of the brazing layers is The thickness is preferably approximately equal to the thickness of the solder ball. Further, the spacer may be made of a fiber-reinforced composite material.

Another semiconductor package of the present invention has a lid having a semiconductor bonded to its inner surface, and a substrate bonded to the semiconductor via a solder ball, and a brazing surface formed by a peripheral edge of the surface of the substrate and a A semiconductor package whose interior is hermetically sealed by a brazed joint formed between the lid and the lid, characterized in that the brazed joint is formed by brazing a spacer with low rigidity on both end faces thereof.

In another semiconductor package of the present invention, the spacer is preferably made of plastic.

Furthermore, another semiconductor package of the present invention includes a lid having a semiconductor bonded to the inner surface thereof, and a substrate bonded to the semiconductor via a solder ball, and a brazing surface formed by a peripheral edge of the surface of the substrate. In a semiconductor package whose interior is hermetically sealed by a brazed joint formed between the brazed joint and the lid, the brazed joint is formed by a diagonal plate having one edge close to the substrate and the other edge close to the lid. It is composed of a spacer and a brazing material filled around the spacer, and the brazing material has an expansion coefficient equivalent to that of the solder ball, and the thickness of the brazed joint is approximately equal to the thickness of the solder ball. It is characterized by being made equal.

In yet another semiconductor package of the present invention, the spacer is preferably made of a material with a small coefficient of thermal expansion.

The second object is achieved by a computer equipped with the semiconductor package of the present invention, another semiconductor package, or another semiconductor package.

[Effect]

The destruction of the solder balls that connect the semiconductor and the board is due to the difference in thermal expansion in the vertical direction between the solder ball and the package that restrains it, so in order to prevent this, the thermal expansion of the solder ball is combined with the thermal expansion in the vertical direction of the package. It is necessary to match the expansion. To achieve this, the first idea is to increase the thickness of the brazing material that joins the lid and the board that make up the package so that it is similar to the solder ball. When the material is melted, bubbles tend to form in the brazing material, which may make it impossible to maintain airtightness.

The two structures described below prevent solder balls from breaking. The first is a structure in which the brazing material is divided in the thickness direction by inserting a spacer in the brazed joint between the lid and the substrate.This structure reduces the thickness of each brazing material, so the package The airtightness of the brazing filler metal can be maintained while keeping the amount of vertical thermal expansion in line with the solder ball. This structure has the disadvantage that a large number of spacers are required to make each filler metal extremely thin. A second structure solves this drawback and uses a spacer that is inclined with respect to the surface of the brazing material. According to this structure, even with a single spacer, part of the spacer is placed close to the package substrate and the other part is placed close to the package lid, so the thickness of the brazing material can be reduced in these parts, and the thickness of the brazing material can be reduced. Airtightness can be maintained. Specifically, this spacer is made of, for example, a thin metal plate or a ceramic plate. Note that this material is desirably a material with low thermal expansion in order to reduce thermal strain occurring in the brazing material.

Apart from the above two structures, in order to match the vertical thermal expansion of the package with the thermal expansion of the solder balls, instead of reducing the thickness of the brazing filler metal and configuring it in multiple layers as described above, heat is applied to the brazed joint. A method of inserting a spacer with a large expansion coefficient is also considered. However, this spacer must have a thermal expansion equivalent to that of a solder ball in a direction perpendicular to the brazing surface, but a low thermal expansion equivalent to a low thermal expansion packaging material in a direction parallel to the brazing surface. be. This is because if the thermal expansion of the spacer in the direction parallel to the brazing surface is significantly different from that of the package material, excessive shear strain will occur in the brazing material between the spacer and the package, causing the brazing material to break. In order to satisfy the thermal expansion conditions for this spacer, the spacer material must be a material with a low rigidity that has a coefficient of thermal expansion similar to that of a brazing filler metal, or a brazing material that has a coefficient of thermal expansion similar to that of a brazing filler metal in the direction perpendicular to the brazing surface. An anisotropic material with a low coefficient of thermal expansion parallel to the plane is required, comparable to the packaging material. As the former material, for example, plastic is used, and because of its low rigidity, thermal expansion is restrained by the brazing material, so that the brazing material does not break. Examples of the latter anisotropic materials include mutual laminates of low thermal expansion metal plates or ceramics and brazing filler metal or materials with a thermal expansion coefficient equivalent to the brazing filler metal, and low thermal expansion fiber cloth or orthogonally aligned materials. Materials such as fiber-reinforced composite materials using fibers are used. These materials have thermal expansion anisotropy because they have a low coefficient of thermal expansion in the plane of the metal plate or in the fiber axis direction.

〔Example〕

One embodiment of the invention is shown in FIG. The semiconductor element] has its front side connected to the wiring board 3 by the solder balls 2,
The back surface is connected to the lid 4 by a bonding brazing material 6. Lid 4
The edges of the wiring board 3 and the wiring board 3 are joined by a sealing brazing material 5 via a spacer 7 to form a package. The sealing brazing material 5 is thin so as to maintain airtightness.

The spacer 7 has a frame shape as shown in FIGS. 2All and 2B, and the cross section 1-1 in FIG. 2A has one of three different structures shown in FIGS. 3 to 5. The spacer 7a shown in FIG. 3 has a metallized film 9 on the entire surface.
A plurality of low thermal expansion Kovar plates 8 (29% Ni-
17% Co--Fe alloy) are mutually joined by a brazing filler metal 10. FIG. 4 shows a spacer 7b which is made of a composite material of a plain-woven cloth of carbon fibers 11 and a copper wire 12 as a spacer having thermal expansion anisotropy, and whose surface is metallized 9. FIG. 5 shows a spacer 7c made of a polyimide member 13 whose surface is coated with a metallized film 9 as a spacer with low rigidity. The metallization 9 is for improving the wettability of the brazing material.

Another embodiment of the invention is shown in FIG. The configuration of this embodiment is almost the same as that in FIG. 1, but a plurality of thin plate spacers 14
The difference is that the sealing brazing material 5 is divided by. As shown in FIGS. 7A and 7B, each thin plate spacer 14 is in the form of a frame made of a thin Kovar plate 8a whose surface is coated with metallization 9 to improve the wettability of the brazing material.

Yet another embodiment of the invention is shown in FIG. The configuration of the present invention is almost the same as that shown in FIG.
is inclined to divide the sealing brazing material 5. The shape of the inclined spacer 15 is shown in FIGS. 9A and 9B.
As shown in the figure, a thin Kovar plate 8 with an inclined cross section is coated with metallization 9 on its surface. The metallization 9 is for improving the wettability of the brazing material.

Further, FIGS. 10A and 10B show another inclined spacer 15.
b. This inclined spacer 15b has slits 16 on the outer periphery of the four corners of the spacer shown in FIG. 9A to further increase its deformability.

〔Effect of the invention〕

According to the present invention, in a semiconductor package, the brazed joint formed between the lid and the edge of the substrate has the same thermal expansion property as the solder ball that is between the lid and the substrate and connects the semiconductor and the substrate. It is constructed by inserting a spacer or a spacer with low rigidity and brazing both ends of the spacer, so the soldered part can be made thinner and air bubbles can be prevented from forming in the soldered part, making the semiconductor package airtight. This has the effect of not only being able to maintain the properties of the solder balls but also preventing the solder balls from breaking.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor package according to an embodiment of the present invention;
Figures 2A and 2B are a plan view and a front view, respectively, of a spacer to be inserted into the joint between the lid and the substrate of a semiconductor package, and Figures 3 to 5 are cross-sections taken along line I-1 in Figure 2A. 6 is a cross-sectional view of a semiconductor package according to another embodiment of the present invention, FIG. 7A is a plan view of a thin plate spacer, FIG. 7B is a cross-sectional view taken along the line ■-■ of FIG. 7A, and FIG. 9 is a sectional view of a semiconductor package according to still another embodiment of the present invention.
Figure A is a plan view of the inclined spacer, Figure 9B is the m of Figure 9A.
-m sectional view, FIG. 10A is a plan view of another inclined spacer,
FIG. 10B is a cross-sectional view taken along the line -■ in FIG. 10A, and FIG. 11 is a cross-sectional view of a conventional semiconductor package. L... Semiconductor element, 2... Solder ball, 3... Wiring board, 4... Lid, 5... Sealing brazing material, 6... Adhering brazing material, 7, 7 a, 7 b , 7 c-spacer 8, 8a-'] Burl plate, 9... Metallized film, 10... Brazing material, 11... Carbon fiber, 12...
Copper wire, 13... Polyimide member, 14, 14a...
Thin plate spacers, 15, 15a, 15b... inclined spacers.

Claims (1)

[Claims] 1. It has a lid with a semiconductor bonded to its inner surface, and a substrate bonded to the semiconductor via a solder ball, and the brazing surface formed by the peripheral edge of the surface of the substrate is connected to the lid. In a semiconductor package whose interior is hermetically sealed by a brazed joint formed therebetween, the brazed joint has a coefficient of thermal expansion substantially equal to that of the substrate and the lid in a direction parallel to the brazing surface; A semiconductor package characterized in that a spacer having a coefficient of thermal expansion equal to that of the solder ball is brazed at both ends in a direction perpendicular to the solder surface. 2. The spacer is composed of a laminate in which plate materials with a small coefficient of thermal expansion and brazing layers having approximately the same coefficient of thermal expansion as the solder balls are alternately provided, and the total thickness of the brazing layers is equal to that of the solder balls. 2. The semiconductor package according to claim 1, wherein the semiconductor package has a thickness substantially equal to the thickness of the semiconductor package. 3. The semiconductor package according to claim 1, wherein the spacer is made of a fiber-reinforced composite material. 4. A lid having a semiconductor bonded to its inner surface and a substrate bonded to the semiconductor via a solder ball, and brazing formed between the brazing surface formed by the peripheral edge of the surface of the substrate and the lid. 1. A semiconductor package whose interior is hermetically sealed by a joint, characterized in that the brazed joint is formed by brazing a spacer with low rigidity on both end faces thereof. 5. The semiconductor package according to claim 4, wherein the spacer is made of plastic. 6. A lid having a semiconductor bonded to its inner surface and a substrate bonded to the semiconductor via a solder ball, and a brazing joint formed between the brazing surface formed by the peripheral edge of the surface of the substrate and the lid. In a semiconductor package whose interior is hermetically sealed by a joint part, the brazing joint part is covered with a spacer made of a diagonal plate with one edge close to the substrate and the other edge close to the lid, and the area around the spacer is filled. Consisting of brazing filler metal,
A semiconductor package characterized in that the brazing material has an expansion coefficient equivalent to that of the solder ball, and the thickness of the brazed joint portion is approximately equal to the thickness of the solder ball. 7. The semiconductor package according to claim 6, wherein the spacer is made of a material having a small coefficient of thermal expansion. 8. A computer equipped with the semiconductor package according to any one of claims 1 to 7.