JPH06177284A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve high temperature left, characteristics with excellent solder reflow resistance by sealing with a resin composite containing an epoxy resin, a specific phenol resin hardener, and a hardening propellent as essential components. CONSTITUTION:Sealing is made with an epoxy resin composite containing an epoxy resin, a phenol resin hardener having biphenyl skeletons expressed by formulas I and/or II as essential components. In the formulas I, II, R1, R2 express C1-C4 alkyls, R3, R4, H, C1-C4 alkyls, and X-CH2-,-C (CH3)2-. Since a jointly used phenol resin hardener has two phenolic hydroxyl groups in a molecule, it is preferable to use an epoxy resin of multifunctionality having two or more epoxy groups in a molecule to improve reactivity, hardenability, and heat resistance. Further, as the hardening propellent, a phosphorous-containing organic basic compound such as triphenylphosphine and a ternary amine such as tetra substituted salt are used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention has excellent moldability such as handleability, reactivity and fluidity during use, and solder reflow crack resistance sealed with an epoxy resin composition having low moisture absorption and low internal stress. The present invention relates to a resin-sealed semiconductor device excellent in

[0002]

2. Description of the Related Art For semiconductor elements such as transistors, ICs and LSIs, resin encapsulation using a plastic package has become the mainstream from the viewpoint of mass productivity. As a semiconductor encapsulating material, a composition in which a curing accelerator is mixed with an epoxy resin and a novolac type phenolic resin as a curing agent is used because it is excellent in moldability, hygroscopicity and heat resistance.

However, with the recent increase in the degree of integration of semiconductors, changes in package size, package shape, mounting method, etc., further improvement in reliability including heat resistance, moisture resistance, and low stress is desired. There is. For example, with the transition of the package mounting method from the pin insertion type to the surface mounting type, the package is exposed to a high temperature of 200 ° C. or higher when mounted on a printed circuit board, and thus the package may crack. The interface between the chip and the sealing resin is peeled off, and the moisture resistance is lowered.

To solve this problem, the glass transition temperature of the encapsulating resin has conventionally been raised to a temperature (200 to 2) during reflow.
Various attempts have been made to increase the high temperature strength at 60 ° C., reduce the moisture absorption rate of the sealing resin, and reduce the stress.
Among these, particularly in thin semiconductor packages, the stress generated by the water vapor pressure of the absorbed moisture far exceeds the high temperature strength of the encapsulating resin, so lower moisture absorption and higher adhesion than raising the glass transition temperature of the resin Effective in reducing stress. As a method therefor, a semiconductor device encapsulated with an epoxy resin composition containing an epoxy resin having a biphenyl in the skeleton and a phenol aralkyl resin curing agent is disclosed in JP-A-3-20771.
No. 4 and Japanese Patent Laid-Open No. 4-48759. Further, Japanese Patent Laid-Open Nos. 4-50223, 4-199856 and
4-199857 discloses a low hygroscopic epoxy resin composition having a naphthalene skeleton.

[0005]

Although the above-mentioned prior art has some effect on the occurrence of cracks during solder reflow, the effect of suppressing the cracks is still insufficient. Further, since these epoxy resin compositions exhibit high adhesion, low moisture absorption and low stress, the glass transition temperature of the cured product tends to be low. On the other hand, in order to raise the glass transition temperature, a method of introducing a rigid molecular structure into the resin is adopted, but in this case, the viscosity of the resin becomes high, and the reactivity and curability are poor, so in terms of moldability. There's a problem. Therefore, it was not satisfactory in any case for the significant improvement of the reflow resistance while maintaining other properties.

An object of the present invention is to provide a resin semiconductor device which is excellent in moldability and is also excellent in solder reflow resistance which is sealed with an epoxy resin composition having a low moisture absorption rate and a low internal stress.

[0007]

In order to achieve the above object, the present inventors have found that the resin has good fluidity during molding and has a low hygroscopicity and a low internal stress. The structure and composition were investigated. As a result, if a specific resin curing agent having a biphenyl skeleton and two phenolic hydroxyl groups in one molecule is used, the biphenyl skeleton not only greatly contributes to lowering the viscosity above the melting point of the curing agent, but also Since it has an effect on heat resistance and low hygroscopicity after resin curing, molding temperature (160 to 180)
It is possible to achieve both high fluidity at (° C.) and low moisture absorption and heat resistance of the resin.

Further, since this resin curing agent has a structure having two phenolic hydroxyl groups in one molecule, the resin cross-linking density after curing does not increase so much, although it has heat resistance. Therefore, not only the adhesiveness of the resin is improved, but also the internal stress can be reduced by lowering the elastic modulus at the reflow temperature of the package.

That is, the resin-encapsulated semiconductor of the present invention comprises: (a) epoxy resin (b) phenol resin curing agent having a biphenyl skeleton represented by Chemical formula 3 and / or Chemical formula 4

[0010]

[Chemical 3]

[0011]

[Chemical 4]

(Wherein R ₁ and R ₂ are C ₁ -C ₄ alkyl; R
₃ , R ₄ is H, C ₁ -C ₄ alkyl; X is —CH ₂ —, —C
_{(CH 3) 2 -, -} CH (CH 3) -, - C (CH 3) (C 6 H
_{5) -, - CH (C} 6 H 5) -, - SO 2 - represent. (C) A resin-encapsulated semiconductor device, which is encapsulated with an epoxy resin composition containing a curing accelerator as an essential component.

In the present invention, the epoxy resin as the component (a) may be any one as long as it has a plurality of epoxy groups in one molecule and is generally used for semiconductor encapsulation. Good. However, since the phenol resin curing agent used in combination has two phenolic hydroxyl groups in one molecule, in order to improve reactivity, curability and heat resistance, more than two epoxy groups in one molecule should be used. It is preferable to use a polyfunctional epoxy resin having. Such epoxy resin includes bisphenol A, F or S type epoxy resin, novolac type epoxy resin, polyfunctional epoxy resin having biphenyl skeleton or naphthalene skeleton, tri or tetra (hydroxyphenyl) alkane epoxy resin, alicyclic Examples thereof include epoxy resins and brominated epoxy resins thereof. In the present invention, one or more of these are used.

In the present invention, in the phenol resin curing agent represented by the chemical formula 3 which is the component (b), the biphenyl skeleton is nucleus-substituted with an alkyl group in order to keep the softening point of the resin at least not lower than the above molding temperature. Those are preferable. But,
Phenolic resin curing agents substituted at both ortho positions of the phenolic hydroxyl group (3 and 5 positions when the bonding position of the hydroxyl group is the 4th position) have large steric hindrance and are poor in reactivity with the epoxy resin. Excluded from the invention. Also,
As the nucleus-substituted alkyl group, those having 1 to 4 carbon atoms are used in order to maintain reactivity. Such phenol resin curing agents include, for example, 3,3'-dimethyl-4,4'-dihydroxybiphenyl and 3,3'-diethyl-4,4 '.
-Dihydroxybiphenyl.

As the phenol resin curing agent represented by Chemical formula 4, a non-nuclear substitution type phenol group is used in consideration of reactivity and curability. Further, in order to maintain the heat resistance of the resin, the number of nucleus substitutions of the phenyl group with the alkyl group is 2
The number is limited and the number of carbon atoms of the alkyl group is preferably 1 to 4. Such phenolic curing agents include, for example:
5,5 '-(1-methylethylidene) [1,1'-biphenyl] -2-ol, 5,5'-(ethylidene)
[1,1'-biphenyl] -2-ol, 5,5'-
(Methylidene) [1,1′-biphenyl] -2-ol, 5,5 ′-(1,1-cyclohexylidene) [1,
1'-biphenyl] -2-ol, 5,5 '-(1-phenylethylidene) [1,1'-biphenyl] -2-ol, 5,5'-(1-phenylmethylidene) [1,
1'-biphenyl] -2-ol, bis (3-phenyl-4-hydroxyphenyl) sulfone and the like can be mentioned. The phenol resin curing agent represented by Chemical Formula 1 or Chemical Formula 2 may be used alone or in combination depending on moldability such as reactivity and fluidity of the resin and various characteristics such as moisture absorption and heat resistance of the cured resin. You can

In the present invention, the phenol resin curing agent represented by Chemical Formula 3 and / or Chemical Formula 4 is essential, but depending on the above-mentioned characteristics, for example, phenol novolac resin other than these phenol resin curing agents, It is also possible to use together with a cresol novolac resin, a phenol- or cresol-based trifunctional curing agent, and a curing agent of phenol and an aralkyl ether polycondensate. The compounding amount of the curing agent containing the phenol resin represented by Chemical Formula 3 and / or Chemical Formula 4 as an essential component is preferably 0.5 to 1.5 equivalents relative to the epoxy resin. If the compounding amount of the curing agent is less than 0.5 equivalent to the epoxy resin, the epoxy resin is not completely cured, resulting in poor heat resistance, moisture resistance and electric properties of the cured product and 1.5 equivalents. On the other hand, if it exceeds, on the contrary, a large amount of hydroxyl groups contained in the curing agent remain even after the resin is cured, so that the electrical characteristics and the moisture resistance are deteriorated.

The epoxy resin composition used in the present invention includes
Usually, a curing accelerator is added to accelerate the curing reaction of the resin. In the present invention, as the curing accelerator as the component (c), phosphorus-containing organic basic compounds such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate or their tetra-substituted boron salts, triethylenediamine, benzyldimethylamine, etc. Tertiary amine, 1,
At least one kind of 8-diazabicyclo (5,4,0) -undecene, imidazole and the like can be mentioned.

The resin composition for a resin-encapsulated semiconductor device of the present invention contains, if necessary, 55 to 85 with respect to the total composition.
Incorporate vol% inorganic filler. The inorganic filler is added for the purpose of improving the thermal expansion coefficient, thermal conductivity, elastic modulus, etc. of the cured product. If the content is less than 55% by volume, these properties cannot be sufficiently improved, and If the content exceeds 85% by volume, the viscosity of the material remarkably increases and the fluidity decreases. Although various compounds can be mentioned as the inorganic filler, it is important to use a thermochemically stable filler for electronic parts, specifically, fused silica, crystalline silica,
At least one inorganic particle selected from alumina is desirable. The average particle size of these fillers is preferably in the range of 0.3 to 30 μm, and when the average particle size is less than 0.3 μm, the viscosity of the resin composition increases and the fluidity decreases remarkably.
If it exceeds 30 μm, the resin component and the filler are likely to separate during molding, and the cured product becomes non-uniform, resulting in variations in the physical properties of the cured product and poor filling in narrow gaps.

Further, in the present invention, in addition to the above, if necessary,
As the resin composition, it is possible to use a flexibilizing agent for toughness and low elastic modulus of the cured product. The blending amount of the flexibilizer is preferably 2 to 20% by weight based on the total resin composition. If the compounding amount of the flexibilizing agent is less than 2% by weight, there is almost no effect on the toughness and low elastic modulus of the cured product, and if it exceeds 20% by weight, the fluidity of the resin composition becomes extremely poor, When the flexibilizer floats on the surface of the resin cured product, the molding die becomes significantly soiled. A flexibilizing agent that is incompatible with the epoxy resin composition can lower the elastic modulus of the cured product without lowering the glass transition temperature, so that a butadiene-acrylonitrile-based copolymer or their terminal or side chain amino group , Epoxy group, carboxyl group-modified copolymer, acrylonitrile-butadiene-styrene copolymer, etc. butadiene-based flexibilizers and terminal or side chain amino groups, hydroxyl groups, epoxy groups, carboxyl group-modified silicone resin-based flexibilizers The silicone-based flexibilizing agent is particularly useful in terms of moisture resistance and high purity.

If necessary, the epoxy resin composition used in the present invention may further include a coupling agent such as epoxysilane or aminosilane for enhancing the adhesiveness between the resin component and the filler, a dye or pigment for coloring, and a curing agent. Various additives such as a release agent for improving the releasability of the product from the mold can be used within a range that does not impair the object of the invention.

Various methods can be used to prepare an epoxy resin composition for semiconductor encapsulation using such raw materials, but generally, a predetermined amount of the raw material mixture is sufficiently mixed. After that, a method of kneading with a hot roll, an extruder or the like, cooling and pulverizing is simple and suitable.

The resin-encapsulated semiconductor device of the present invention is obtained by encapsulating a semiconductor chip with the epoxy resin composition thus obtained. As the manufacturing method, a low pressure transfer molding method is usually used,
In some cases, a method such as injection molding, compression molding or casting can be used. Further, in order to improve the reliability of the semiconductor device, it is desirable to perform aftercure at a temperature of 150 ° C. or higher for a predetermined time after sealing.

[0023]

[Function] The present invention has excellent moldability and solder reflow resistance,
Moreover, another reason why a resin-encapsulated semiconductor having good reliability is obtained is that a semiconductor chip is encapsulated with an epoxy resin composition containing a phenol resin curing agent having a specific structure and characteristics used in the present invention. .

The phenol resin curing agent in the present invention has a biphenyl skeleton and has two phenolic hydroxyl groups in one molecule. Therefore, the biphenyl skeleton in this resin curing agent not only greatly contributes to lowering the viscosity above the melting point of the curing agent, but also has an effect on heat resistance and low hygroscopicity after resin curing. (160-
It is possible to achieve both high fluidity at 180 ° C. and low moisture absorption and heat resistance of the resin.

Further, since this resin curing agent has a structure having two phenolic hydroxyl groups in one molecule, the resin cross-linking density after curing does not increase so much even though it has heat resistance. Since this structure has an effect of improving the adhesiveness of the resin, the adhesiveness with the chip or the frame is improved, and the reflow resistance can be improved. further,
At the reflow temperature of the package, the elastic modulus of the resin is significantly reduced and the internal stress is reduced, which is a great effect for improving the reflow resistance.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples.

<Examples 1 to 11 and Comparative Examples 1 to 3> Epoxy resin, phenol resin curing agent, silicone flexibilizing agent and curing accelerator shown below, and square fused silica having an average particle size of 6 μm as a filler. 30/70 mixture of spherical fused silica with an average particle size of 30 μm, antimony trioxide as a flame retardant aid, epoxysilane as a coupling agent,
Using montanic acid ester wax as the release agent and carbon black as the coloring agent, molding materials were prepared at the compounding ratios shown in Table 1. A biaxial roll having a diameter of 20 inches was used for kneading each material, and kneading was performed for about 10 minutes at a roll surface temperature of about 55 to 80 ° C.

Epoxy Resin Epoxy Equivalent Softening Point (I) Orthocresol Novolac Type 195 65 Epoxy Resin

[0029]

[Chemical 5]

(II) 215 63

[0031]

[Chemical 6]

(III) 182 79

[0033]

[Chemical 7]

(IV) 161 93

[0035]

[Chemical 8]

(V) 230 90

[0037]

[Chemical 9]

(VI) 195 107

[0039]

[Chemical 10]

(VII) Brominated Epoxy Resin 375 68

[0041]

[Chemical 11]

Phenolic Resin OH Equivalent (I) Dimethyl Biphenol 107

[0043]

[Chemical 12]

(II) 5,5 ′-(1-Methylethylidene) 190 [1,1′-biphenyl] -2-ol

[0045]

[Chemical 13]

(III) 5,5 ′-(methylidene) 176 [1,1′-biphenyl] -2-ol

[0047]

[Chemical 14]

(IV) Phenol Novolac Resin 106

[0049]

[Chemical 15]

(V) Phenol aralkyl resin 172

[0051]

[Chemical 16]

Silicone flexible agent Side chain modified silicone resin (molecular weight 73600, epoxy equivalent 3900) Curing accelerator DBU; 1,8-Biazabicyclo (5,4,0) -undecene TPP; triphenylphosphine

[0053]

[Table 1]

Among the various properties in the table, the moisture absorption rate and the adhesive force were measured by the following.

(1) Spiral flow: Measured at 180 ° C. and 70 kg / cm ² using a mold conforming to the EMMI standard.

(2) Glass transition temperature and linear expansion coefficient: Measured at a sound raising speed of 2 ° C./min using a thermomechanical measuring device.

(3) Mechanical strength (flexural strength and flexural modulus): According to JIS-K6911, room temperature and 215
It was measured at ° C.

(4) Moisture absorption rate: A disk having a size of 90 mmφ and 2 mmt was formed, absorbed at 85 ° C./100% RH for 300 hours, and determined from the weight change.

(5) Adhesive strength: The aluminum peel strength between the 0.03 mmt aluminum foil and the molding material was measured at a pulling speed of 50 mm / min.

As is clear from Table 1, the resin composition for semiconductor encapsulation of the present invention has excellent fluidity as compared with the conventional resin composition comprising the ortho-cresol type epoxy resin and the phenol novolac resin shown in Comparative Example 1. And shows good moldability such as having fluidity close to that of a resin composition (comparative examples 2 and 3) using a biphenyl skeleton epoxy resin which is a low-viscosity epoxy resin. In addition, comparing the cured product characteristics with those of Comparative Examples 2 and 3, it is possible to improve the glass transition temperature without lowering the adhesiveness or the hygroscopic property. Furthermore, since the bending elastic modulus at 215 ° C. is low, an effect can be expected in reducing thermal stress at the reflow temperature. As described above, it can be seen that the resin composition for semiconductor encapsulation of the present invention exhibits various balanced properties in terms of moldability, adhesiveness, moisture absorption characteristics, heat resistance, and the like.

Also, using this material, a silicon chip (6 × 6 m) having aluminum zigzag wiring formed on the surface thereof.
m) is mounted on a 42 alloy lead frame, and a semiconductor device (outside dimension 20 × 14 mm, thickness 2 mm) is further sealed by wire bonding with a gold wire (30 μmφ) between the aluminum electrode on the chip surface and the lead frame. 6 at ℃
Hardened for hours. For the reliability test of solder reflow resistance, this resin-sealed semiconductor device was tested at 168 at 85 ° C. and 85% RH.
After being left for a period of time, a test of heating for 90 seconds in an infrared reflow furnace at 240 ° C. was performed, and the number of cracked packages was examined. In the high temperature storage reliability test, the above resin-encapsulated semiconductor device was placed in a high temperature tank at 200 ° C. for 20 hours.
After standing for 0 hour, the number of defective connections at the joint between the gold wire and the aluminum wiring was examined. The results are summarized in Table 2.

[0062]

[Table 2]

As is clear from Table 2, the resin-encapsulated semiconductor device of the present invention is encapsulated with a resin composition having high adhesion, low moisture absorption rate, and a great effect of reducing thermal stress at the reflow temperature. Therefore, it can be seen that the solder reflow resistance is excellent. Further, since it has high adhesion, low moisture absorption, and a relatively high glass transition temperature, it has good high-temperature storage characteristics, and can balance reliability with solder reflow resistance.

[0064]

The resin-encapsulated semiconductor device obtained by the present invention has a relatively high glass transition temperature as compared with the conventional one, and has the features of low stress, low moisture absorption and high adhesion. It is excellent in solder reflow resistance and can exhibit good characteristics in other reliability such as high temperature storage characteristics.

Front Page Continuation (72) Inventor Hiroyoshi Ogaku, 1-1 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Toshiaki Ishii 7-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd., Hitachi Research Laboratory (72) Inventor, Hiroyuki Hozoji, 1-1 1-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Hitachi Research Laboratory, (72) Inventor Teruo Kitamura 7, Mika-cho, Oita, Ibaraki Prefecture No. 1 in Hitachi, Ltd. Hitachi Research Laboratory

Claims (2)

[Claims] 1. (a) Epoxy resin (b) Phenolic resin curing agent having a biphenyl skeleton represented by Chemical formula 1 and / or Chemical formula 2 [Chemical 2] (Wherein R ₁ and R ₂ are C _{1 to} C ₄ alkyl; R ₃ and R ₄ are H,
C ₁ -C ₄ alkyl; X is _{-CH 2 -, - C (CH} 3)
_{2 -, - CH (CH 3} ) -, - C (CH 3) (C 6 H 5) -, -
_{CH (C 6 H 5) -} , - SO 2 - represent. (C) A semiconductor device which is encapsulated with an epoxy resin composition containing a curing accelerator as an essential component. 2. A resin-encapsulated semiconductor device according to claim 1, which is encapsulated with an epoxy resin composition containing a filler composed of inorganic fine particles in an amount of 55 to 85% by volume based on the total composition.