JPH03116855A - Package structure - Google Patents

Abstract

PURPOSE:To lessen the poor wetting of a sealing part by a method wherein the sealing part that the sealing member of either a package base or a package cap is made to vary gradually in thickness along the inside to the outside of the sealing member is provided to a sealing region. CONSTITUTION:The Au evaporated face of an LSI chip 4 is laid on top of the Au metallized face previously provided to the center of the inner face of a package base 1, which is made to stand under an atmosphere of high temperature, whereby the Au metallized face and the Au evaporated face react with each other to form an Au-Si eutectic, and the LSI chip 4 is bonded to the inner face of the package base 1. After the bonding pad of the LSI chip 4 is connected to a lead frame 5 with a bonding wire 6, the package cap 2 on which a low melting glass 3 has been formed is aligned with the package base 1, and they are pressed against each other in opposed directions keeping them in an atmosphere of high temperature to seal up them. By this setup, the occurrence of voids caused by the discharge failure of the package inner pressure can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a technique for sealing a package of a semiconductor device, and in particular to a technique that is effective when used to reliably make the inside of a package airtight.

[Conventional technology]

In large-scale integrated circuits (LSI), the higher the mounting capacity, the larger the shape and heat generation, and the need for some kind of mounting means and heat dissipation means. One way to do this is to mount an LSI chip inside the package base of a package that is divided into two parts, a package base and a package cap, and then glue and fix the package cap to the base side to make the inside of the package airtight and protect the LSI chip. I'm trying. In addition, a heat sink is fixed in contact with the surface of the base side of the package to dissipate heat.

By the way, the present inventor studied the relationship between the sealing structure of the package and the internal gas.

The following are the techniques studied by the present inventor, and the outline thereof is as follows.

That is, as shown in FIG. 6, the package base on which the LSI chip is mounted and the cap are bonded together by applying low melting point glass 3 (for example, melting point 450° C.) to a uniform thickness, and melting the low melting point glass 3 while bringing the package cap 2 close to the package base 1 in a high temperature atmosphere.

[Problem to be solved by the invention]

However, when the sealing material is uniformly formed on the surface of the legs and welded as described above, the entire surfaces of the two low-melting glasses 3 come into contact at the same time, so the gas pressure inside the package is gradually released to the outside. This may cause the adhesive to bulge, or
The inventor has discovered that there is a problem in that voids are generated and airtightness is reduced.

In this case, for example, as shown in Japanese Patent Application Laid-Open No. 60-20541, it is possible to arrange a gas adsorbent inside the package to absorb the gaseous substance sealed inside the package, but the process and There is a problem that requires a gas adsorbent.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a technique that can prevent the occurrence of voids caused by insufficient discharge of internal pressure of a package during sealing.

The above objects and novel features of the present invention will become clear from the description of Waterproof m* and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a package structure in which an LSI chip is mounted inside one of a package base or a package cap, and a sealing material for adhesively fixing both is formed in a sealing area of the package base and the package cap, A sealing portion is provided in the sealing region, the thickness of which varies from the inside to the outside of the sealing material of either the package base or the package cap.

[Effect]

According to the above-mentioned means, at the start of sealing, the sealing part having a small thickness in the gas venting direction comes into contact with the other parts, and then the other whole-surface contact part comes into contact with the other parts. Therefore, when the sealing portion comes into contact with each other, the internal gas blows out from this thin wall portion and does not affect other thick wall portions, thereby preventing the generation of voids.

[Embodiment 1] FIG. 1 is a front cross-sectional view showing the main parts of a package structure according to the present invention, and FIG. 2 is a front cross-sectional view showing a completed state of a semiconductor device to which the present invention is applied.

As shown in FIG. 2, an LSI (large scale integrated circuit) chip 4
A package base 1 (made of alumina ceramics) is attached to the inner surface, and legs are formed around the package base 1. A package cap 2 (made of alumina ceramics) is bonded to this package base 1 via a low melting point glass 3.
The atmosphere in which the SI chip 4 is installed is made airtight. Note that before sealing, a lead frame 5 is disposed between opposing low melting point glasses (sealing materials) 3, and its inner end is connected to the pad of the LSI chip 4 by a bonding wire 6.

Furthermore, an LSI chip 4 is provided on the surface of the package base 1.
A heat dissipating fin 7 is attached to dissipate the generated heat and perform cooling.

To explain the manufacturing process, first, the Au (gold) metallized surface of the LSI chip 4 is superimposed on the Au (gold) metallized surface that has been applied in advance to the center of the inner surface of the package base l, and then placed in a high temperature (approximately 450° C.) atmosphere. put. As a result, the Au metallized layer and the Au evaporated surface react to form an Au-3i eutectic, and the LSI chip 4 is bonded to the inner surface of the package base 1.

Next, bonding pads (not shown) of the LSI chip 4 and lead frame 5 are connected with bonding wires 6. Thereafter, the package cap 2 on which the low melting point glass 3 is formed is fitted onto the package base 1, placed in a high-temperature atmosphere, and sealed by pressing the package base 1 and the package cap 2 in opposite directions.

The sealing temperature profile in this case is as shown in Figure 3.
The low melting point glass 3 begins to melt at about 400°C and completely melts at 450°C. After this state is maintained for a certain period of time, the ambient air temperature is lowered and the sealing process is completed. In this case, the entire surface of the low melting point glass 3 is flat as in the conventional case, and it is sealed without allowing the internal gas to escape, and the gas, which has expanded in volume due to high temperature, tries to forcefully escape to the outside, creating voids. Become.

Therefore, if we create an escape area for the gas generated inside,
This problem will be resolved. The present invention makes it possible to do this.

As shown in FIG. 1, the sealing part 3a is formed so that the thickness becomes thinner from the inside to the outside (or conversely, the thickness becomes thicker from the inside to the outside). Provided on glass 3. The sealing portion 3a does not need to be provided all around the leg, but may be provided at a few locations such as a portion or a corner. Further, in FIG. 1, the sealing portion 3a is provided on the package cap 2 side, but it may be provided on the package base 1 side.

By doing this, the opposing low melting point glass 3
The first contact between the two ends is made as a line contact at the sealing part 3a. Therefore, the adhesion area of the sealing material at the start of sealing becomes small, and the gas inside that expands in volume due to the temperature rise escapes to the outside of the package through the sealing portion 3a, so that voids are not generated. After this, the sealing part 3a
The entire surface of the low melting point glass 3 other than the above contacts, and the sealing surfaces are completely joined.

[Example 2.3] In addition to the structure shown in FIG. 1, the sealing part 3a has a fourth structure.
As shown in the figure or FIG. 5, a convex portion 8 or 9 may be provided in a portion between the inside and the outside.

Above, the invention made by the present inventor has been specifically explained based on Examples, but it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. stomach.

〔Effect of the invention〕

Among the inventions disclosed in this application, the effects obtained by typical ones are as follows.

That is, the package structure is such that an LSI chip is mounted inside one of the package base and the package cap, and a sealing material is formed in the sealing area of the package base and the package cap for adhesively fixing both. Since the sealing region is provided with a sealing portion having a thickness different from the inside to the outside of the sealing material of either the package base or the package cap, the generation of voids etc. is eliminated. (Also, poor wetting of the sealing portion can be reduced, and the sealing yield can be improved.

[Brief explanation of drawings]

Fig. 1 is a front sectional view showing the main parts of the package structure according to the present invention, Fig. 2 is a front sectional view showing the completed state of a semiconductor device to which the invention is applied, and Fig. 3 is a sealing temperature profile showing the sealing temperature profile. Temperature characteristic diagram. Figure 4 is a front sectional view showing the second embodiment of the present invention. Figure 5 is a front sectional view showing the third embodiment of the invention. Figure 6 shows the main parts of the conventional package structure. FIG. 1...Puff'! -'; base, 2... package cap, 3... low melting point glass (sealing material), 3a...
Sealing part, 4. Permanent LSI chip, 5. Lead frame, 6. Bonding wire, 7. Radiation fin, 8.9. Convex portion. Figure 1 Figure 1 Figure 1

Claims (1)

[Claims] 1. A package in which an LSI chip is mounted inside one of a package base or a package cap, and a sealing material is formed in the sealing area of the package base and package cap to adhesively fix both. The structure is
A package structure characterized in that the sealing region is provided with a sealing portion having a thickness that varies from the inside to the outside of the sealing material of either the package base or the package cap. 2. The package structure according to claim 1, wherein the thickness of the sealing portion gradually decreases from the inside to the outside of the sealing area or from the outside to the inside. 3. The package structure according to claim 1, wherein the sealing portion has a low height portion provided between the inside and the outside or between the outside and the inside of the sealing area.