JPH04744A - Resin-sealed semiconductor device - Google Patents

Abstract

PURPOSE:To acquire a resin-sealed semiconductor device of high heat resistance which is sealed by a resin composition of low water absorption rate, high adhesion and good anti-reflow characteristics by carrying out sealing by a resin composition containing epoxy resin of specified composition and phenol novolak resin curing agent as an essential element. CONSTITUTION:A resin composition which contains epoxy resin expressed by a formula and phenol novolak resin curing agent as an essential element is used. In the formula, (l), (m), (n) shown the number of repetition units of 0 to 2. Thereby, it is possible not only to improve heat resistance of sealing resin to maintain high strength at a temperature of reflow time but also to restrain increase of water absorption rate of resin to improve adhesion. Since a resin composition which contains the epoxy resin expressed by the formula and phenol novolak resin curing agent having two or more phenol hydroxyl groups in one molecule as an essential element can lower elastic modulus of sealing resin, it is also effective in reduction of heat stress which causes strain and damage of an element and cutting of a bonding wire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-sealed semiconductor device having excellent heat resistance, moisture resistance, and solder resistance (reflow resistance).

[Conventional technology]

Compositions containing epoxy resin, novolac type phenolic resin as a curing agent, and a curing accelerator are used as semiconductor encapsulation materials because they have excellent moldability, moisture absorption characteristics, and heat resistance. .

However, with the recent increase in the degree of integration of semiconductors and changes in package size, package shape, mounting method, etc., there is a desire for further improvements in reliability, including heat resistance, moisture resistance, and low stress. For example, with the shift in package mounting methods from pin insertion type to surface mount type, packages are now exposed to high temperatures of over 200°C when mounted on printed circuit boards, which can cause cracks in the pancage and damage to chips. Problems such as peeling at the interface with the sealing resin and reduced moisture resistance have occurred. These problems become more noticeable when the package absorbs moisture, and the demand for reflow resistance is becoming stronger for thin surface-mounted semiconductor devices.

To meet this demand, various efforts have been made to raise the glass transition temperature of the sealing resin, increase its high-temperature strength at reflow temperatures (200 to 260'C), and reduce the water absorption rate of the sealing resin. Attempts are being made. To raise the glass transition temperature of the sealing resin, polyfunctional epoxy resins such as those described in JP-A-64-9214 and JP-A-64-31816 and polyimide resins as described in JP-A-1-126321 are used. It is proposed to use Also,
JP-A-1-108256 describes an epoxy resin sealing material with low water absorption and reflow resistance.

[Problem to be solved by the invention]

The above conventional technology does not give sufficient consideration to achieving both heat resistance and low water absorption, and polyfunctional epoxy resins and polyimide resins that have a high glass transition temperature generally tend to have high water absorption. However, resins with low water absorption had a problem in that the glass transition temperature was slightly inferior to that of conventional resins. Furthermore, since these resins tend to have lower adhesive strength with the lead frame than in the past, water absorption from the interface between the lead frame and the resin tends to increase. Therefore, the improvement in reflow resistance was not satisfactory in any case.

An object of the present invention is to provide a resin-sealed semiconductor device that is encapsulated with a resin composition that has excellent heat resistance, low water absorption, and high adhesive strength, and has excellent reflow resistance.

[Means to solve the problem]

In order to achieve the above object, the present inventors have conducted various studies on sealing resins that can achieve both high heat resistance, low water absorption, and high adhesive strength. Among these, epoxy resins in particular are far superior to other thermosetting resins such as polyimide resins in terms of moldability such as curability and fluidity, so polyfunctional epoxy resins satisfy these characteristics. We investigated the possible chemical structures and compositions. As a result, the epoxy resin represented by the general formula (I) - Tani Q (in the formula, Q, m, and n indicate the number of repeating units of O to 2) and the phenol novolak resin cured If a resin composition containing the agent as an essential component is used, the heat resistance of the sealing resin can be improved and the temperature during reflow (200 to 250°C) can be improved.
The inventors have discovered that not only can high strength be maintained, but also that the increase in water absorption of the resin can be suppressed and the adhesive strength can be improved, leading to the present invention.

In addition, a resin composition containing as essential components an epoxy resin represented by the general formula (I) and a phenol novolac resin curing agent having two or more phenolic hydroxyl groups in one molecule is a conventional cresol or phenol type epoxy resin. It was found that since the elastic modulus of the sealing resin can be lowered compared to that of resin, it is also effective in reducing thermal stress, which causes distortion and damage to elements and breakage of bonding wires.

In the present invention, since the epoxy resin represented by the above general formula (I) is trifunctional, it is possible not only to improve heat resistance, but also to improve the crosslinked resin after curing, in which some of the molecules between the crosslinks are bisphenol. Because it is composed of A-type, it has a structure that has both flexibility and toughness, and has low water absorption and high adhesive strength.
In addition, it has characteristics such as low elastic modulus that can be satisfied at the same time.

The repeating units M, m, and n in the structural formula are in the range of O to 2,0, and exhibit heat resistance, adhesion, and low water absorption characteristics that are satisfactory as a sealing resin, but the values of Ω, m, and n are large. When this happens, the glass transition temperature tends to decrease and the high temperature strength also tends to decrease. On the other hand, when the values of Q, m, and n are small, the heat resistance is excellent, but since the softening temperature of the resin is low, it tends to become semi-solid, and the handling during the mixing operation of the resin composition becomes complicated.

Therefore, in the present invention, epoxy resins other than the epoxy resin represented by general formula (I) may be used in combination depending on the characteristics.

In the present invention, the epoxy resin used in combination with the epoxy resin of general formula (I) refers to all epoxy resins containing two or more epoxy groups in one molecule, such as bisphenol A, bisphenol S, bisphenol F, and phenol novolak. Bisphenol-based epoxy resins and novolac-based epoxy resins obtained by reacting resins and bresol novolanc resins with shrimp chlorohydrin, or their brominated epoxy resins, such as cyclohexene, cyclopentadiene, and dicyclopentadiene. These include epoxy resins obtained from alicyclic compounds, epoxy resins obtained from vinyl polymers, epoxy resins obtained from polyvalent alluloses such as glycerin, and brominated epoxy resins thereof, within a range that does not impede the effects of the present invention. in,
Any number of types can be used as appropriate. In this case, the blending amount is the epoxy resin (A) represented by the general formula (I),
(A) with other epoxy resin (B): (B)=10
It is preferable to mix them in a ratio of 0:0 to 20:80. When the proportion of the epoxy resin (A) represented by the general formula (I) is 20% by weight or less, it becomes difficult to achieve both heat resistance, low water absorption, and high adhesiveness, which are the objectives of the present invention.

Furthermore, among the epoxy resins represented by the general formula (I), repeating units 111. Epoxy resins with m and n values of 0 or very small have a low softening temperature and are semi-solid, so select and use epoxy resins with a softening temperature of 60°C or higher from among the epoxy resins that can be used in combination. be able to. on the other hand,
Repeating unit Q.

Epoxy resins in which m and n have values of 2 or close to 2 are:
On the other hand, since the melt viscosity during molding increases, it is possible to select and use epoxy resins with a softening temperature of 60° C. or lower or viscous liquids from among the epoxy resins that can be used in combination. In these cases, if both epoxy resins are uniformly mixed in advance at a temperature of 70''C or higher and then cooled and used as a solid resin, the complexity of handling can be eliminated.

The purity of the epoxy resin represented by the general formula (I) and the epoxy resin used together is not particularly limited, but if it contains a large amount of ionic impurities such as chlorine ions, various reliability of semiconductors will be significantly reduced. It is preferable that these amounts are small. When the resin component is extracted with 10 times the amount of 120℃ hot water for more than 100 hours, the electrical conductivity of the extracted liquid is 100μ
The object of the present invention can be fully achieved if the pH is 3 to 7 and the amount of halogen ions is 20 ppm or less.

The phenol novolak resin curing agent used in the present invention combines phenols such as phenol, gresol, and xylenol with formaldehyde, p-toluenesulfonic acid, hydrochloric acid,
A condensation product obtained by reaction under an acidic catalyst such as sulfuric acid, perchloric acid, or oxalic acid is used, and basically has a chemical structure shown by general formula (n).

(Here, R1 means either H or CHa, and a represents an integer of 1 or more.) The method for adjusting the molecular weight of the obtained phenol novolac resin is based on the molar ratio of phenols and formaldehyde. The molecular weight can be controlled by the type and amount of catalyst used, but from the viewpoint of resin curing properties and fluidity, the molecular weight is desirably 400 to 3,000. Also,
In order to use it for semiconductor encapsulation, it is preferable to use a product with as little ionic impurities or unreacted raw materials as possible. Therefore, one reaction product should be thoroughly washed with water or steam distilled and dried under reduced pressure, etc., or as necessary. It is also possible to purify using ion exchange resins, ion exchangers, etc.

In the present invention, the phenol novolak resin curing agent is preferably blended in an amount of 0.5 to 1.5 equivalents to the epoxy resin.
The blending amounts are 50 to 95% by weight of epoxy resin,
It is desirable that the amount of the phenol novolac resin curing agent be 5 to 50% by weight. If the epoxy resin is less than 50% by weight, a large amount of hydroxyl groups in the phenol resin remain even after the resin is cured, resulting in poor electrical properties and moisture resistance. On the other hand, if the blending amount of the epoxy resin exceeds 95% by weight, the epoxy resin will not be completely cured, so that the cured product will have poor heat resistance, moisture resistance, and electrical properties.

The resin composition used for semiconductor encapsulation in the present invention contains an inorganic filler in an amount of 55 to 80% by weight based on the entire composition, if necessary. Inorganic fillers are added for the purpose of improving the coefficient of thermal expansion, thermal conductivity, modulus of elasticity, etc. of the cured product, and if the amount added is less than 55% by volume, these properties cannot be sufficiently improved. If the amount exceeds 80% by volume, the viscosity of the material will increase significantly and the fluidity will decrease. Inorganic fillers include various compounds, but it is important to use thermochemically stable fillers for electronic component materials. A type of inorganic particle is preferred. Note that the average particle diameter of these fillers is preferably in the range of 1 to 30 μm. This is because if the average particle size is less than 1 μm, the viscosity of the resin composition will increase and the fluidity will decrease significantly, and if it exceeds 30 μm, separation of the resin component and filler will easily occur during molding, resulting in hardening. things become uneven,
This is because variations occur in the physical properties of the cured product and the ability to fill narrow gaps becomes poor.

Furthermore, in the present invention, if necessary, a softening agent may be used in the resin composition to toughen the cured product or lower the elastic modulus. The blending amount of the flexibility agent is preferably 2 to 20% by weight based on the total resin composition. If the blending amount of the plasticizing agent is less than 2% by weight, it will have little effect on toughening the cured product or lowering the elastic modulus, and if it is more than 20% by weight, the fluidity of the resin composition will be extremely low. The mold becomes noticeably dirty due to deterioration in the quality of the mold, and the appearance of the adhesive on the surface of the cured resin. The flexibility agent is incompatible with the epoxy resin composition because it can lower the elastic modulus of the cured product without lowering the glass transition temperature. Chain amino group, epoxy group, carboxyl group-modified copolymer, butadiene yarn threading agent such as acrylonitrile-butadiene-styrene copolymer, terminal, or side chain amino group, hydroxyl group, epoxy group, carboxyl group-modified silicone resin Thread threading agent and the like can be used, but silicone threading agent is particularly useful from the viewpoint of moisture resistance and high purity.

In addition, the composition used for the resin-encapsulated semiconductor device of the present invention may include, if necessary, a curing catalyst for promoting the curing reaction of the resin, and a coupling agent for improving the adhesion between the resin component and the filler. Various additives such as dyes and pigments for coloring, and mold release agents to improve the mold releasability of the cured product from the mold can be used within the range that does not impair the purpose of the invention. The curing catalyst is a phosphorus-containing organic basic compound such as triphenylphosphine or tetraphinyl phosphonium tetraphenylborate, or a tetra-substituted boron salt thereof, a tertiary amine such as triethylenediamine or benzyldimethylamine, or a 1,8- It is preferable to use at least one type of diazabicyclo(5,4,0)-undecene, imidazole, etc., and further, as a coupling agent, at least one type of epoxysilane, aminosilane, etc.

A general method for producing a molding material for semiconductor encapsulation using the above-mentioned raw materials is to sufficiently mix a raw material mixture of a predetermined amount and then knead it using a heated roll or an extruder.
The product material is obtained by cooling and grinding. Low-pressure transfer molding is usually used as a method for encapsulating semiconductors using the molding material obtained in this way, but in some cases, methods such as injection molding, compression molding, and casting are also used. It is also possible by

[Effect]

The reason why a resin-sealed semiconductor device having excellent heat resistance, moisture resistance, and reflow resistance can be obtained in the present invention is due to the structure of the epoxy resin represented by the general formula (I) used in the present invention.

Since the epoxy resin represented by the general formula (I) is trifunctional, it can exhibit high heat resistance. In addition, in the crosslinked resin formed after curing, some of the molecules between crosslinks are composed of bisphenol A type, resulting in a resin with a structure that has flexibility and toughness, and has high adhesive strength and low elastic modulus at the same time. It can be assumed that the results are satisfactory. Furthermore, although this epoxy resin is a three-dimensionally crosslinked resin, it has a certain degree of flexibility, so the free volume of the resin is small and it exhibits the characteristic of low moisture absorption. Furthermore, the phenol novolak resin curing agent used in the present invention has a structure with excellent moisture resistance. A semiconductor encapsulated with a resin composition containing an epoxy resin of general formula (I) and a phenol novolak resin curing agent as essential components, which has excellent heat resistance, high high-temperature strength, high adhesive strength, and low moisture absorption. The device is difficult to adsorb moisture, which is the cause of package cracks that occur during reflow heating, and also prevents moisture permeation at the interface between the resin and the lead frame, resulting in good reflow resistance. Another factor in the reflow resistance is that it has high high temperature strength that can withstand water vapor pressure during reflow heating.

Further, since the resin composition of the present invention has a characteristic of having a low elastic modulus, thermal stress generated in a semiconductor device is reduced, and reliability can be significantly improved.

〔Example〕

Hereinafter, the present invention will be specifically explained according to examples.

<Example 1> It is shown by the structural formula and has an epoxy equivalent of 210. Epoxy resin “TECHMORE” VG3101 with a softening temperature of 59°C (trade name of Mitsui Petrochemicals Co., Ltd.), brominated bisphenol A type epoxy resin (epoxy equivalent: 394, softening temperature 65°C)
and phenol novolak resin curing agent (hydroxyl equivalent: 1
06, softening temperature 65°C), curing catalyst shown in Table 1, 30/70 mixture of prismatic fused silica with an average particle size of 6 μm and spherical fused silica with an average particle size of 30 μm as a filler, flame retardant aid A molding material was prepared using antimony dioxide as a molding agent, epoxysilane as a coupling agent, montanic acid ester wax as a mold release agent, and carbon black as a coloring agent at the compounding ratios shown in Table 1.

A biaxial roll with a diameter of 20 inches is used to mix each material.
Crosstalk was performed for about 10 minutes at a roll surface temperature of about 55 to 80'C.

<Examples 2 to 7> As shown in Table 1, the epoxy resin “TEC” of Example 1
A molding material was produced in the same manner as in Example 1, except that the type and amount of the epoxy resin used in combination with HMORE'' VG3101 and the type of curing accelerator were changed.

Comparative Example 1> Orthocresol novolac type epoxy resin (epoxy equivalent: 195, softening temperature: 75 to 80') was used as the epoxy resin.
A molding material was produced in the same manner as in Example 1 except that C) was used.

Comparative Example 2> Epoxy resin "TECMORE" of Example 1 15
A molding material was produced in the same manner as in Example 1, except that 15 parts by weight of the brominated bisphenol A epoxy resin and 70 parts by weight of the orthocresol novolak epoxy resin of Comparative Example 1 were used.

<Comparative Example 3> Shown by the structural formula, epoxy equivalent: 160, softening temperature: 110-12
A molding material was produced in the same manner as in Example 1, except that trifunctional epoxy resin TACTIX742 (trade name of Dow Chemical Co., Ltd.) at 0°C was used.

<Examples 8 to 11> The same material as in the previous example was used as the resin component, and a side chain epoxy-modified silicone resin (molecular weight 73,600, epoxy equivalent: 3,900) was used as a new plasticizing agent, and the compounding ratios shown in Table 2 were used. A molding material was prepared.

Comparative Example 4 Using the same materials as in Examples 8 to 10, molding materials were produced in the same manner as described above at the compounding ratios shown in Table 2.

The moldability of the molding material thus obtained at 180°C, mold temperature 180°C, molding pressure cuff 0 kg/aJ,
After molding for 90 seconds and heating at 180℃,
The results of various physical properties of the cured molded product are shown in Tables 1 and 2.
They are summarized in the table. Incidentally, the blending ratios in Tables 1 and 2 are always expressed in parts by weight. Also, among the epoxy resins shown with symbols in the table, E-1032860 (
Epoxy equivalent: 171. Melt viscosity at 150°C: 3.1
The structural formula of p, s (product name of Yuka Shell Epoxy Co., Ltd.) is Y
It has the structure of L-931 (epoxy equivalent: 198, softening temperature: 88° C., trade name of Yuka Shell Epoxy Co., Ltd.).

In addition, the curing catalysts indicated by symbols in the table are DBU: 1.8 diazabicyclo(5,4,0)-undecene, TPP; triphenylphosphine, 2E4MZ 2-ethyl, 4
- Methylimidazole.

Of the various properties listed in the table, water absorption and adhesive strength were measured by the methods shown below.

(I) Water absorption rate = 90Iφ, 2m1t disk was molded, 1
Water was absorbed at 20'C/100% RH for 70 hours, and the weight change was determined.

(2) The aluminum peel strength between a 3 mm thick aluminum foil and a molding material was measured at a tensile speed of 50 min.

As is clear from Table 1, the resin composition for semiconductor encapsulation according to the present invention is shown in Comparative Examples. - High glass transition temperature of 215°C compared to cresol novolac type epoxy resin compositions and other multifunctional epoxy resin compositions
It can be seen that not only the bending strength is increased, but also the adhesiveness and water absorption rate are also excellent. Furthermore, the general formula of the present invention (
If the epoxy resin represented by I) is less than 20 parts by weight based on the total epoxy resin, no improvement in various properties such as heat resistance, adhesiveness, and water absorption rate will be observed. On the other hand, as is clear from Table 2, the resin compositions containing the plasticizing agent of the present invention exhibit almost the same characteristics as in Table 1, except that the modulus of elasticity of the molding material can be lowered. However, it can be seen that when the content of the flexibility agent is less than 2% by weight, there is almost no effect on lowering the elastic modulus, and when it is more than 20% by weight, mold staining and a decrease in spiral flow are significant.

Next, a silicon chip with aluminum zigzag wiring formed on the surface using a molding material is mounted on a 4270 series lead frame, and a gold wire (30 μmφ) is connected between the aluminum electrode on the chip surface and the lead frame. The bonded semiconductor device is sealed and heated to 65℃/65%.
After being left under RH for a predetermined time, a test was conducted in which the package was heated for 60 seconds in a paper reflow oven at 215° C., and the number of cranks in the package is shown in Table 3 as the number of cranks.

As is clear from Table 3, the resin-sealed semiconductor device of the present invention has low water absorption, good adhesion, and is encapsulated with a resin composition that has high high-temperature strength, so it has good reflow resistance. It's extremely good.

〔Effect of the invention〕

The resin-sealed semiconductor device obtained by the present invention not only has high heat resistance and high strength at high temperatures compared to conventional ones, but also has the characteristics of high adhesiveness and low moisture absorption. Excellent reflow resistance.

Claims (10)

[Claims] 1. An epoxy resin represented by general formula (I), and
A resin-sealed semiconductor device characterized in that it is sealed with a resin composition containing a phenol novolac resin curing agent as an essential component. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, l, m, and n indicate the number of repeating units from 0 to 2.) 2. In claim 1, the epoxy resin (A) represented by the general formula (I) and the epoxy resin (B) having a plurality of epoxy groups in one molecule, (A):(B)=10
A resin-sealed semiconductor device sealed with a resin composition containing 50 to 95% by weight of an epoxy resin composition and 5 to 50% by weight of a phenol novolac resin curing agent arranged in a ratio of 0:0 to 20:80. . 3. Claim 1 or 2, wherein the filler made of inorganic fine particles is present in an amount of 55 to 50% based on the total composition.
A resin-sealed semiconductor device containing 80% by volume. 4. In claim 1, the epoxy resin (A) represented by the general formula (I) and the epoxy resin (B) having a plurality of epoxy groups in one molecule, (A):(B)=10
A resin-sealed semiconductor device sealed with an epoxy resin composition mixed in a ratio of 0:0 to 20:80. 5. In claim 1, the epoxy resin (A) represented by the general formula (I) and the epoxy resin (B) having a plurality of epoxy groups in one molecule, (A):(B)=10
A resin-sealed semiconductor device sealed with a phenol novolac resin curing agent blended in a ratio of 0:0 to 20:80. 6. In claim 1, the epoxy resin (A) represented by the general formula (I) and the epoxy resin (B) having a plurality of epoxy groups in one molecule, (A):(B)=10
A resin-sealed semiconductor device sealed with a flexibilizing agent blended in a ratio of 0:0 to 20:80. 7. 7. The resin-sealed semiconductor device according to claim 4, wherein the resin-sealed semiconductor device is encapsulated with a composition in which the amount of the flexibilizing agent is 2 to 20% by weight based on the total resin composition. 8. The resin-sealed semiconductor device according to claim 4, 5, 6, or 7, wherein the plasticizing agent is a silicone compound. 9. Claim 4, 5, 6, 7 or 8, wherein the filler made of inorganic fine particles has a content of 55 to 80% based on the total resin composition.
Resin-encapsulated semiconductor device including volume%. 10. Claim 3, 4, 5, 6, 7, 8 or 9, wherein the filler made of inorganic particles has an average particle size of 1 to 3.
A resin-sealed semiconductor device comprising at least one type of inorganic particle selected from 0 μm fused silica, crystalline silica, and alumina.