JPH08258077A - Semiconductor device - Google Patents

Abstract

PURPOSE: To enhance both of solder cracking resistance and productivity by sealing a semiconductor element by using a resin compsn. containing an epoxy resin represented by a specific formula, a curing agent containing a plurality of phenolic hydroxyl groups and polyethylene oxide wax. CONSTITUTION: An epoxy resin compsn. sealing a semiconductor element consists of a bisphenyl type epoxy resin represented by fomula (wherein R1 -R4 are a 1-4C alkyl group), a curing agent containing at least two phenolic hydroxyl groups in one molecule thereof and polyethylene oxide wax acting as a release agent. By using this compsn., a semiconductor device excellent in both of solder cracking resistance and productivity can be obtained.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, technological innovations in the semiconductor field have 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, pins are two-dimensionally taken out and fixed to the surface of the mounting substrate directly by soldering or the like. Such a surface-mounting type semiconductor device has the advantages of being thin, light and small, and 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,
Cracks occur in the package due to the vapor pressure of water during solder mounting. That is, in the surface mount type semiconductor device as shown in FIG.
And penetrates into the package 3 and stays mainly 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 FIGS. 1 and 2, reference numeral 8 is wire bonding.

As a solution to such a problem, after sealing a semiconductor element with a package, the entire semiconductor device obtained is hermetically sealed and opened immediately before surface mounting, or the 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 it takes time.

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]

Embedded image

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 lowered, so that the back surface of the die bond pad and the resin portion are Peeling is likely to occur, and as a result, cracks are likely to occur due to solder immersion during moisture absorption, and it is difficult to achieve both productivity and solder crack resistance.

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

[0009]

In order to achieve the above object, the semiconductor device of the present invention seals a semiconductor element using 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.

As a method of preventing the generation 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 strength of the sealing resin itself is increased. There are three possible ways to increase Above all, the package cracking is prevented based on the most effective method. 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 peeling phenomenon from the die bond pad is apt to occur and the solder crack resistance tends to be lowered. Under such circumstances, the present inventors have conducted a series of studies to obtain a solder crack resistance and productivity. As a result, it has been found that when the epoxy resin represented by the general formula (1) is used in combination with an oxidized polyethylene wax as a release agent, improvement in solder crack resistance and improvement in productivity can both be achieved. The invention was reached.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail.

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

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

[0014]

Embedded image

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 are contained in the above general formula (1). ), A special epoxy resin (component A) will be used. Examples of the epoxy resin usually used include various epoxy resins such as cresol novolac type, phenol novolac type, novolac bis A type and bisphenol A type. As the novolac type epoxy resin, those having an epoxy equivalent of 150 to 250 and a softening point of 50 to 130 ° C. are usually used, and as the cresol novolac type epoxy resin, an epoxy equivalent of 180 to 210 and a softening point of 60 to 110 ° C. Is commonly used. When both are used in this way, the epoxy resin (component A) represented by the above general formula (1) is added in an amount of 50% by weight (hereinafter referred to as “%”) of the entire epoxy resin component.
(Abbreviated)) is preferably set above.

The specific curing agent used with the above-mentioned 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 novolac resin, cresol novolac 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. Generally, 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 may be such that the hydroxyl groups in the specific curing agent are 0.7 to 1.3 equivalents per equivalent of epoxy groups 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 mold release agent and partially oxidizes lower polyethylene. It is synthesized. In addition, it is preferable to use an oxidized polyethylene wax 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, when 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. Furthermore, 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, the mixture is 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 a series of steps of tableting if necessary. Thus, the desired epoxy resin composition can be produced.

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

[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). Excellent resistance to solder cracks when immersed in solder. Moreover, it is also excellent in mold 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 equivalent of 105 and a softening point of 80 ° C. were used. * 3: PED-521 (acid value 15, dropping point 105 ° C.) manufactured by Hoechst Co. 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, phenolic 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 as 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 perform 10 shots of molding. And the load at the time of mold release in the 10th shot cured epoxy resin composition was measured. In the figure, 13 is a cull, 14 is a sprue, 15 is a runner, 1
6 is a cavity. Figure 4 shows the measurement of the load at the time of mold release.
As shown in FIG. 3, the middle die 11 of the molding die is placed on the support stand 17, and the push-pull gauge 18 is used to insert 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 was possible was evaluated from the value, and when continuous molding was possible, it was evaluated as ◯, and when it was 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, a semiconductor element is transfer-molded using the above epoxy resin composition (conditions:
A semiconductor device was manufactured by 175 ° C. × 2 minutes, 175 ° C. × 5 hours post-curing). The semiconductor device thus obtained is left to stand in a constant temperature bath of 85 ° C./85% RH to absorb moisture, and then subjected to a test in which it is immersed in a solder melt at 260 ° C. for 10 seconds. The generated semiconductor device was counted. The results are also shown in Table 4 below.

[0036]

[Table 4]

From the results in Table 4, the comparative example products are poor in either releasability, high water absorption rate, low adhesive strength 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.

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