JPH05131486A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain semiconductor device excellent in cracking resistance at soldering and productivity by a method wherein semiconductor is sealed by epoxy resin composition containing specified epoxy resin, specified hardener and polyethylene oxide wax. CONSTITUTION:As the epoxy resin, one represented by the formula I is used, in which R1-R4 are alkyl group of C1-C4 and may well be equal to or different from one another. As the hardener, one containing at least two phenolic hydroxyl groups in one molecule is used and phenolic novolak, resol type phenolic resin or the like is exampled. The polyethylene oxide wax serves as releasant. Further, inorganic filler, which occupies 50-90% of the whole epoxy resin composition, is included normally. By sealing semiconductor element by the above- mentioned composition, excellent effect is displayed in resistance to cracking at the immersion into solder and releasability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which is excellent in reliability, particularly in solder cracking resistance during solder mounting and in productivity.

[0002]

2. Description of the Related Art In recent years, technological innovation in the semiconductor field has been remarkable, and semiconductor devices such as LSI chips have been highly integrated and speeded up. Densification is progressing. From such a viewpoint, a surface mount type package is becoming mainstream instead of a pin insertion type package such as a dual in-line package (DIP). In a semiconductor device using this type of package, the pins are taken out in a plane and are fixed directly to the surface of the mounting substrate by soldering or the like. Such a surface-mount type semiconductor device has the advantages of being thin, light, and small, and also has the advantage of occupying a small area on the mounting substrate. It also has the advantage that it can be mounted on both sides of the board.

[0003]

However, in the semiconductor device using the surface mount type package as described above,
If the package itself absorbs moisture before surface mounting,
Cracking occurs in the package due to the vapor pressure of water during solder mounting. That is, in the surface mounting type semiconductor device as shown in FIG.
It penetrates into the package 3 through the through holes and mainly accumulates on the front surface of the Si-chip 7 and the back surface of the die bond pad 4.
Then, when solder surface mounting such as vapor phase soldering is performed, the accumulated water is vaporized by heating during solder mounting, and due to the vapor pressure thereof, as shown in FIG.
The resin portion on the back surface of the die bond pad 4 is pushed downward to form a void 5 therein, and at the same time, a crack 6 is generated in the package 3. In FIG. 1 and FIG. 2, 8 is a wire bonding.

As a solution to such a problem, after sealing the semiconductor element with a package, the entire semiconductor device obtained is hermetically sealed and opened immediately before surface mounting, or the above-mentioned method is used immediately before surface mounting. Semiconductor device at 100 ℃ 2
A method of drying for 4 hours and then performing solder mounting has been proposed and already implemented. However, according to such a pretreatment method, there is a problem that the manufacturing process becomes long and labor is required.

On the other hand, in order to improve the hygroscopicity of the sealing resin, as an epoxy resin composition for semiconductor sealing, for example,
It has been proposed to use an epoxy resin having a skeleton represented by the following general formula (2) and a phenolic curing agent represented by the following general formula (3).

[0006]

[Chemical 3]

However, in the above epoxy resin composition, when the semiconductor element is sealed to form a semiconductor device, the mold releasability from the mold is poor, and there is a problem in productivity. Also,
If the amount of the release agent that has been conventionally used for the purpose of improving the releasability is increased, the releasability is improved but the adhesiveness with the lead frame material is deteriorated. Is easily peeled off, and as a result, cracking due to solder immersion is likely to occur during moisture absorption, and it is difficult to achieve both productivity and solder crack resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor device which is excellent in solder crack resistance as well as in productivity.

[0009]

In order to achieve the above object, the semiconductor device of the present invention seals a semiconductor element with an epoxy resin composition containing the following components (A) to (C). Take the configuration. (A) An epoxy resin represented by the following general formula (1).

[Chemical 4] (B) A curing agent containing at least two phenolic hydroxyl groups in one molecule. (C) Oxidized polyethylene wax.

[0010]

As a method of preventing the occurrence of package cracks, the moisture absorption of the sealing resin is suppressed, the adhesive force between the back surface of the die bond pad and the surface of the semiconductor element and the sealing resin is increased, and the sealing resin itself There are three possible ways to increase the strength of the. Above all, the most effective method is used to prevent the occurrence of package cracks. However, in the case of this method, since the skeleton of the resin used is hydrophobic, the compatibility with the release agent is improved and the release agent is less likely to exude to the surface. As a result, the releasability deteriorates and the productivity decreases. On the contrary, when the amount of the release agent is increased to improve the releasability, the phenomenon of peeling from the die bond pad is likely to occur, and the solder crack resistance tends to decrease. Under such circumstances, the present inventors have conducted a series of studies in order to obtain a solder having both solder crack resistance and productivity. As a result, an epoxy resin represented by the general formula (1),
The inventors have found that the use of a combination of oxidized polyethylene wax as a release agent makes it possible to improve both the solder crack resistance and the productivity simultaneously.

Next, the present invention will be described in detail.

The epoxy resin composition used in the present invention comprises a special epoxy resin (A component) represented by the general formula (1), a specific curing agent (B component), and an oxidized polyethylene wax (C). Component) and is usually in the form of powder or a tablet formed by compressing it.

The special epoxy resin (component A) is a biphenyl type epoxy resin and is represented by the following general formula (1).

[0014]

[Chemical 5]

As described above, by adding a lower alkyl group to the phenyl ring having a glycidyl group, it becomes water repellent. Then, the special epoxy resin (A
The epoxy resin component may be composed of only the component), or may be used in combination with other commonly used epoxy resins. In the former case, all of the epoxy resin components are composed of the special epoxy resin (A component) represented by the above general formula (1), and in the latter case, a part of the epoxy resin components is represented by the above general formula (1). ) A special epoxy resin (component A) represented by Examples of the above-mentioned usually used epoxy resins include various epoxy resins such as cresol novolak type, phenol novolak type, novolak bis A type and bisphenol A type. As the novolak type epoxy resin, one having an epoxy equivalent of 150 to 250 and a softening point of 50 to 130 ° C. is usually used, and as the cresol novolak type epoxy resin, an epoxy equivalent of 180 to 210 and a softening point of 60 to 110 ° C. Things are commonly used. When both are used in this way, the epoxy resin (component A) represented by the general formula (1) is added in an amount of 50% by weight (hereinafter referred to as “%”) of the total epoxy resin component.
It is preferable to set the above.

The specific curing agent used together with the special epoxy resin (component A) has a phenolic hydroxyl group of 1
At least two are contained in the molecule. For example,
Examples thereof include phenol novolak resin, cresol novolak resin, resol type phenol resin, and phenol aralkyl resin represented by the following general formula (4).

[0017]

[Chemical 6]

The above-mentioned phenol aralkyl resin can be obtained by reacting aralkyl ether and phenol with a Friedel-Crafts catalyst. In general, α, α'-
A condensation polymerization compound of dimethoxy-p-xylene and a phenol monomer is known.

The mixing ratio of the epoxy resin component and the specific curing agent is such that the hydroxyl group in the specific curing agent is 0.7 to 1.3 equivalents per equivalent of the epoxy group in the epoxy resin. It is suitable. More preferred is 0.9-
1.1 equivalents.

The oxidized polyethylene wax (component C) used together with the special epoxy resin (component A) and the specific curing agent (component B) acts as a release agent and partially oxidizes lower polyethylene. Is synthesized. In the above-mentioned oxidized polyethylene wax, it is preferable to use one having an acid value of 10 to 30 and a dropping point (a temperature at which it melts to form a droplet) of 90 to 130 ° C. The content of the oxidized polyethylene wax (component C) is 0.05 to 0.50% in the epoxy resin composition.
It is preferable to set the ratio to. That is, 0.05
If it is less than%, the desired releasability cannot be obtained, and as a result, the productivity decreases. On the contrary, if it exceeds 0.50%, the productivity is improved, but the die bond pad and the cured resin are easily separated, and as a result, the solder crack resistance tends to be lowered.

The epoxy resin composition for semiconductor encapsulation usually contains an inorganic filler. The inorganic filler is not particularly limited, and examples thereof include commonly used quartz glass powder, talc, silica powder, alumina powder, calcium carbonate, carbon black powder and the like. Among them, it is preferable to use silica powder, particularly fusible silica powder. The content of such an inorganic filler is preferably set to 50 to 90% of the whole epoxy resin composition. That is, if the content is less than 50%, the effect of containing the filler tends to be significantly reduced.

In the epoxy resin composition used in the present invention, in addition to the above-mentioned components, a conventionally known tertiary amine, quaternary ammonium salt, imidazoles, boron compound or the like may be used alone as a curing accelerator. Or together. Further, a coupling agent such as a silane coupling agent and a flame retardant can be used.

The epoxy resin composition used in the present invention can be manufactured, for example, as follows. That is, the above components and, if necessary, the curing accelerator, the coupling agent, and the flame retardant are mixed in a predetermined ratio. Then, these mixtures are melt-kneaded in a heated state using a kneading machine such as a mixing roll machine, cooled to room temperature, crushed by a known means, and tableted if necessary. The desired epoxy resin composition can be produced by the step.

Using such an epoxy resin composition,
The method of sealing the semiconductor element is not particularly measured, and can be performed by a known molding method such as ordinary transfer molding.

[0025]

As described above, the semiconductor device of the present invention is sealed by using the special epoxy resin composition containing the special epoxy resin (component A) and the oxidized polyethylene wax (component C). Therefore, it has excellent resistance to solder cracking when immersed in solder. Moreover, it is also excellent in releasability, and as a result, productivity is improved.

Next, examples will be described together with comparative examples.

[0027]

Examples 1 to 3 The respective components shown in Table 1 below were blended in the proportions shown in the same table, melt-kneaded for 3 minutes with a mixing roll machine (temperature 100 ° C.), cooled and solidified, and then pulverized to obtain the object. A powdery epoxy resin composition was obtained. The gel time at 175 ° C. of the obtained epoxy resin composition is also shown in Table 1.

[0028]

[Table 1]

* 1: An epoxy resin represented by the following structural formula (epoxy equivalent 190, softening point 107 ° C.) was used.

[0030]

[Chemical 7] * 2: A hydroxyl group equivalent of 105 and a softening point of 80 ° C. were used. * 3: PED-521 manufactured by Hoechst Co. (acid value 15, dropping point 105 ° C.) was used. * 4: An average particle size of 15 μm was used. * 5: 3-glycidoxypropyltrimethoxysilane was used.

[0031]

[Comparative Examples 1 to 12] Epoxy resins, phenol resins and release agents were blended in the combinations shown in Tables 2 and 3 below. A powdery epoxy resin composition was obtained in the same manner as in Example 1 except for the above. Moreover, the compounding ratio of triphenylphosphine which is a curing accelerator was adjusted so that the gel time at 175 ° C. of the obtained epoxy resin composition was 20 to 30 seconds.

[0032]

[Table 2]

[0033]

[Table 3]

Next, the releasability of the epoxy resin compositions of Examples and Comparative Examples thus obtained was evaluated.
The evaluation method of the releasability was performed as follows. That is, a three-layer structure as shown in FIG. 3 (upper mold 10, middle mold 1
1, the lower mold 12) was used to mold 10 shots. And the load at the time of mold release in the epoxy resin composition cured product of the tenth shot was measured. In the figure, 13 is a cull, 14 is a sprue, 15 is a runner, 1
6 is the cavities. Fig. 4 shows the measurement of the load during release.
As shown in FIG. 3, the middle die 11 of the forming die is placed on the support stand 17, and the push-pull gauge 18 is used to attach the middle die 11 from above.
The epoxy resin composition cured product 19 therein was demolded. The load value at this time was measured. Then, whether or not continuous molding is possible was evaluated from the value, and when continuous molding was possible, it was evaluated as ◯, and when impossible, it was evaluated as x. These evaluation results are shown in Table 4 below.
It was shown to.

Further, the water absorption of the cured product of the obtained epoxy resin composition and the adhesive strength with 42 alloy frame were measured and are also shown in Table 4 below. Further, using the above epoxy resin composition, a semiconductor element is transfer molded (conditions:
A semiconductor device was produced by post-curing (175 ° C. × 2 minutes, 175 ° C. × 5 hours). The semiconductor device thus obtained is allowed to absorb moisture by being left in a thermostatic chamber at a relative humidity of 85 ° C./85% RH, and then immersed in a solder melt at 260 ° C. for 10 seconds to carry out a test. The number of semiconductor devices in which the occurrence of ∑ The results are also shown in Table 4 below.

[0036]

[Table 4]

From the results shown in Table 4, the comparative example products are poor in either releasability, high water absorption rate, low adhesive force or poor solder crack resistance. On the other hand, the products of Examples have excellent releasability, low water absorption and high adhesive strength. Moreover, it can be seen that the solder crack resistance is high.

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[Procedure amendment]

[Submission date] December 14, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view illustrating a situation in which a package crack occurs in a conventional semiconductor device.

FIG. 2 is a vertical cross-sectional view illustrating a situation in which a package crack is generated in a conventional semiconductor device.

FIG. 3 is an explanatory diagram showing a method for molding a cured epoxy resin composition used in a method for evaluating releasability.

FIG. 4 is an explanatory diagram showing a load measuring method which is an evaluation method of releasability.

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Claims (2)

[Claims] 1. A semiconductor device obtained by encapsulating a semiconductor element with an epoxy resin composition containing the following components (A) to (C). (A) An epoxy resin represented by the following general formula (1). [Chemical 1] (B) A curing agent containing at least two phenolic hydroxyl groups in one molecule. (C) Oxidized polyethylene wax. 2. An epoxy resin composition for semiconductor encapsulation containing the following components (A) to (C). (A) An epoxy resin represented by the following general formula (1). [Chemical 2] (B) A curing agent containing at least two phenolic hydroxyl groups in one molecule. (C) Oxidized polyethylene wax.