JPH0672202B2 - Epoxy resin composition for semiconductor encapsulation - Google Patents

Description

The present invention relates to an epoxy resin composition for semiconductor encapsulation, which has excellent solder heat resistance and reliability and a small linear expansion coefficient.

<Prior art> Epoxy resin has excellent heat resistance, moisture resistance, electrical properties, adhesiveness, etc., and since various properties can be imparted by blending formulation, it is used as an industrial material such as paints, adhesives, and electrical insulation materials. Has been done.

For example, as a sealing method for electronic circuit parts such as semiconductor devices, hermetic seals made of metal or ceramics and resin seals made of phenolic resin, silicone resin, epoxy resin, etc. have been proposed so far. From the standpoint of balance, the main focus is resin sealing with epoxy resin.

On the other hand, recently, in mounting components on a printed circuit board, densification and automation have been promoted. Instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, components are soldered to the surface of the board. “Surface mounting method” is becoming popular. Along with that, the package is high-density mounting from the conventional DIP (dual in-line package) type,
It is shifting to a thin FPP (flat plastic package) type suitable for surface mounting.

With the shift to the surface mounting method, the soldering process, which has not been a problem so far, has become a big problem. In the conventional pin insertion mounting method, the lead portion is only partially heated in the soldering process, but in the surface mounting method, the entire package is immersed in a heating medium and heated. As the soldering method in the surface mounting method, immersion in a solder bath, heating with a saturated vapor of an inert gas (vapor phase method), infrared reflow method, etc. are used. In either method, the entire package is heated to a high temperature of 210 to 270 ° C. It will be heated.
Therefore, a package sealed with a conventional sealing resin has a problem that a crack is generated in a resin portion during soldering, the reliability is deteriorated, and the package cannot be used as a product.

The occurrence of cracks in the soldering process is said to be due to the moisture absorbed between the post-curing and the mounting process explosively turning into steam and expanding during soldering heating. A method is used in which the entire package is stored in a sealed container that is dried and shipped.

Various improvements have been made to the sealing resin. For example, a method of blending a rubber component with a sealing resin to reduce the internal stress (JP-A-58-219218, JP-A-59-96122) and a method of selecting the type of inorganic filler (JP-A- Sho 58-19
No. 136, JP-A-60-202145), a method of making the stress and strain uniform by making the shape of the inorganic filler spherical or controlling the particle diameter (JP-A-60-171750).
JP, JP-A-60-17937, JP-A-62-74924, JP-A-62-124143, JP-A-62-209128, JP-B-63-26128), water repellency There is a method (Japanese Unexamined Patent Publication (Kokai) No. 60-65023) in which water absorption is reduced by the additive or wax described above to reduce stress generation due to water in the solder bath.

<Problems to be Solved by the Invention> However, the method of enclosing a dry package in a container has the drawbacks that the manufacturing process and the handling of the product are complicated, and the product price is extremely high.

Also, resins improved by various methods have been gradually effective, but they are not sufficient to meet the more severe demands accompanying the progress of packaging technology. Specifically, after humidifying the semiconductor device sealed with the resin obtained by these conventional methods, for example, 85 ° C / 85% RH treatment for 72 hours, or 121 ° C / 2 atmosphere PCT (pressure cooker test). )
If 72 hours after the treatment, it is soaked in a solder bath, the resin part swells or cracks, and the reliability decreases.

In other words, the development of a sealing resin with excellent solder heat resistance that prevents cracks from occurring during soldering heating and has not obtained a highly reliable sealing resin, corresponding to the progress of surface mounting technology Is currently desired.

An object of the present invention is to solve the problem of cracks generated in the soldering process, to provide a highly reliable epoxy resin composition, and to enable a resin-encapsulated semiconductor device capable of surface mounting. .

<Means for Solving the Problems> That is, the present invention relates to an epoxy resin (A) and a curing agent (B).
And an epoxy resin composition containing 75 to 85% by weight of fused silica (C) having an average particle diameter of 20 μm or less, wherein the fused silica (C) is a crushed fused silica (C ′) 90 having an average particle diameter of 10 μm or less. Epoxy resin for semiconductor encapsulation, which comprises 50% by weight and 10 to 50% by weight of spherical fused silica (C ″) having an average particle size of 30 μm or less, and the coefficient of linear expansion of the composition is 15 × 10 ⁻⁶ / ° C. or less. It is a composition.

The configuration of the present invention will be described in detail below.

The epoxy resin (A) in the present invention is not particularly limited as long as it has two or more epoxy groups in one molecule.

For example, cresol novolac type epoxy resin, bishydroxybiphenyl type epoxy resin, bisphenol A type epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, halogenated epoxy resin, spiro ring containing epoxy resin And so on.

Depending on the application, two or more epoxy resins may be used together, but for semiconductor device encapsulation, the epoxy equivalent of cresol novolac type epoxy resin, bishydroxybiphenyl type epoxy resin, etc. is 500 from the viewpoint of heat resistance and moisture resistance.
In particular, it is preferable that the total epoxy resin content of the epoxy resin is 300% or less, especially 50% by weight or more.

In the present invention, the compounding amount of the epoxy resin (A) is usually 5
~ 25% by weight. If it is less than 5% by weight, moldability and adhesiveness are insufficient, and if it exceeds 25% by weight, the coefficient of linear expansion becomes large and it becomes difficult to reduce the stress.

The curing agent (B) in the present invention is not particularly limited as long as it reacts with the epoxy resin (A) and is cured.

For example, novolak resins such as phenol novolac and cresol novolac, bisphenol compounds such as tetrabrom and bisphenol A, acid anhydrides such as maleic anhydride, phthalic anhydride, pyromellitic anhydride, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, etc. Aromatic amines and the like. Bisphenol novolac and cresol novolac are preferably used for sealing semiconductor devices from the viewpoint of heat resistance and storability. Two or more curing agents may be used in combination depending on the application.

In the present invention, the compounding amount of the curing agent (B) is usually 2 to 15% by weight.

Furthermore, the blending ratio of the epoxy resin (A) and the curing agent (B) is (B) to (A) from the viewpoint of mechanical properties and moisture resistance.
It is preferable that the chemical equivalent ratio of is in the range of 0.5 to 1.6, particularly 0.8 to 1.3. In the present invention, a curing catalyst may be used to accelerate the curing reaction between the epoxy resin (A) and the curing agent (B). The curing catalyst is not particularly limited as long as it accelerates the curing reaction. For example, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-
4-methylimidazole, 2-phenylimidazole,
Imidazoles such as 2-phenyl-4-methylimidazole and 2-heptadecylimidazole, triethylamine, benzyldimethylamine, α-methylbenzyldimethylamine, 2- (dimethylaminomethyl) phenol, 2,4,6-tris (dimethyl) Aminomethyl) phenol, tertiary amines such as 1,8-diazabicyclo (5,4,0) undecene-7, zirconium tetramethoxide, zirconium tetrapropoxide, tetrakis (acetylacetonato) zirconium, tri (acetylacetonato) )
Examples thereof include organic metals such as aluminum, triphenylphosphine, triethylphosphine, tributylphosphine, trimethylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, and the like. Depending on the application, two or more curing catalysts may be used together. The addition amount of the curing catalyst is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin (A).

The fused silica (C) in the present invention has an average particle size of 20 μm or less, and 90 to 50% by weight of crushed fused silica (C ′) having an average particle size of 10 μm or less and spherical fused silica (C ″) having an average particle size of 30 μm or less. 10 to 50% by weight, where the average particle size means the particle size (median size) at which the cumulative weight becomes 50% The average particle size of fused silica (C) exceeds 20 μm or is crushed. The average particle size of fused silica (C ') is 10 μm
If it exceeds, the solder heat resistance is insufficient. Also, if the average particle size of spherical fused silica (C ″) exceeds 30 μm,
Damage the Al wiring. The average particle size of the fused silica (C) is preferably 15 μm or less.

The ratio of crushed fused silica (C ′) and spherical fused silica (C ″) in the fused silica (C) of the present invention is (C ′).
Is 90 to 50% by weight and (C ″) is 10 to 50% by weight. When the ratio of the crushed fused silica (C ′) exceeds 90% by weight, the fluidity at the time of molding is lowered to less than 50% by weight. In the present invention, the blending amount of fused silica (C) is 75 to 85% by weight, preferably 75 to 83 parts by weight. However, if it exceeds 85% by weight, the fluidity at the time of molding decreases, which is not practical.

In the present invention, the fused silica (C) is preferably surface-treated in advance with a coupling agent such as a silane coupling agent or a titanate coupling agent from the viewpoint of moisture resistance and mechanical properties.

The epoxy resin composition of the present invention has a linear expansion coefficient of 15 × 16 ⁻⁶ /
C. or less, preferably 13 × 10 ⁻⁶ / ° C. or less. If the coefficient of linear expansion exceeds 15 × 10 ^-6 / ℃, the thermal stress increases and the solder heat resistance decreases. Here, the coefficient of linear expansion is a value at a glass transition temperature or lower measured in accordance with ASTM D696 standard in a state where the epoxy resin composition is sufficiently cured.

The epoxy resin composition of the present invention includes crystalline silica, calcium carbonate, magnesium carbonate, alumina, magnesia,
Clay, talc, calcium silicate, titanium oxide, asbelt, filler such as glass fiber, halogen compound such as halogenated epoxy resin, flame retardant such as phosphorus compound,
Flame retardant aids such as antimony trioxide, carbon black,
Coloring agents such as iron oxide, silicone oil, modified nitrile rubber, modified polybutadiene rubber, olefin rubber, elastomers such as styrene rubber, silane coupling agents, coupling agents such as titanate coupling agents,
A long-chain fatty acid, a metal salt of a long-chain fatty acid, an ester of a long-chain fatty acid, an amide of a long-chain fatty acid, a release agent such as paraffin wax, and a crosslinking agent such as an organic peroxide can be optionally added.

The epoxy resin composition of the present invention is preferably melt-kneaded, and a known method can be used for melt-kneading. For example, using a Banbury mixer, kneader, roll, single-screw or twin-screw extruder, co-kneader, etc.
The resin composition can be prepared at a temperature of up to 150 ° C.

<Examples> Hereinafter, the present invention will be specifically described with reference to Examples.

The number of parts in the examples means parts by weight.

Examples 1 to 7 and Comparative Examples 1 to 5 Reagents were dry-blended with a mixer at the composition ratios shown in Tables 1 and 2. This is the roll surface temperature
The mixture was heated and kneaded for 5 minutes using a 90 ° C. mixing roll, cooled and pulverized to produce an epoxy resin composition.

Using this composition, a low-pressure transfer molding method was used.
44pin molded under the condition of 5 ℃ × 4 minutes and sealed with simulated element
After obtaining QFP, the molded product and the runner portion were post-cured at 175 ° C. for 5 hours. After post-cure, the physical properties of each composition were measured by the following physical property measuring methods.

Solder heat resistance: 16 44-pin QFPs were heated at 85 ° C and 85% RH for 72 hours, and then vapor phase reflow was performed at 215 ° C for 90 seconds, and the number of QFPs without cracks was calculated.

Linear expansion coefficient: AST by using the runner part at the time of 44pin QFP molding
It measured according to MD-696 standard, and calculated | required the value of 50-170 degreeC.

Reliability: Using the 44-pin QFP that has been subjected to the solder heat resistance test described above, heat-treating it at 121 ° C and 100% RH, and pin failure rate is 50%.
I asked for the time.

The results are shown together in Table 2.

Comparative Example 6 In place of the epoxy resin (A) and the curing catalyst shown in Table 1, epoxy equivalent 190 was cresol novolac epoxy resin and 2-phenylimidazole, respectively. ~ 7, Comparative Examples 1-5
Kneading, molding and evaluation were performed in the same manner as in. These results are shown in Table 3.
Shown in.

Comparative Example 7 Same composition as Comparative Example 6 except that the addition amount of the elastomer was 0% by weight and the addition amounts of the epoxy resin (A), the curing agent (B) and the fused silica (C) were changed to the ratios shown in Table 3. The composition was kneaded, molded, and evaluated. The results are shown together in Table 3.

As shown in Table 2, the epoxy resin compositions of the present invention of Examples 1 to 7 have a solder heat resistance of 69% or more and a reliability of 1290.
It is excellent with h.

On the other hand, as seen in Comparative Examples 1 and 3, when the average particle size of the crushed fused silica (C ′) exceeds 10 μm, the ratio of the crushed fused silica (C ″) in the silica is less than 50% by weight. The solder heat resistance is less than 25% and the reliability is less than 300 hours, and the reliability is higher when the ratio of crushed silica in silica exceeds 90% by weight, as seen in Comparative Example 2. Is inferior to 570h.

Further, as seen in Comparative Example 4, when the amount of fused silica (C) added is less than 75% by weight and the coefficient of linear expansion exceeds 15 × 10 ⁻⁶ / ° C., the solder heat resistance is 13% and the reliability is high. Inferior to 260h.

As seen in Comparative Example 5, when the amount of the fused silica (C) added exceeded 85% by weight, the fluidity was lowered and unfilling occurred during molding.

As seen in Table 3, in Comparative Examples 6 and 7, the average particle size is 10 μm.
75 to 85% by weight of fused silica (C) having an average particle size of 20 μm or less consisting of 90 to 50% by weight of crushed fused silica (C ′) of m or less and 10 to 90% by weight of spherical fused silica having an average particle size of 30 μm or less However, the coefficient of linear expansion exceeds 15 × 10 ^-6 / ℃.
In this case, the solder heat resistance is 13% or less, and the reliability is 280 hours or less. From this, it is clear that in the present invention, the linear expansion coefficient needs to be 15 × 10 ⁻⁶ / ° C. or less.

<Effects of the Invention> The present invention provides an epoxy resin composition for semiconductor encapsulation excellent in solder heat resistance and reliability by adding a curing agent and fused silica having a specific composition to an epoxy resin to reduce the linear expansion coefficient. Is obtained.

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Claims (1)

[Claims] 1. An epoxy resin composition containing an epoxy resin (A), a curing agent (B), and 75 to 85% by weight of fused silica (C) having an average particle size of 20 μm or less, wherein the fused silica (C) is used. Is crushed fused silica (C ') with an average particle size of 10 μm or less
90 to 50% by weight and 10 to 50% by weight of spherical fused silica (C ″) having an average particle size of 30 μm or less, and the linear expansion coefficient of the composition is 15 × 10 ⁻⁶ / ° C. or less for semiconductor encapsulation Epoxy resin composition.