JPH1045872A - Epoxy resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition having excellent moldability without generation of void after molding, capable of realizing excellent resistance to soldering and useful for sealing of a semiconductor by blending a specific epoxy resin, a specific hardener, a polysiloxane, a hardening accelerator and molten silica powder. SOLUTION: This epoxy resin composition is composed of (A) an epoxy resin containing >=30wt.% of a resin expressed by the formula I (R is a 1-9C alkyl or a halogen), (B) a phenolic resin hardener having <=5 poise melt viscosity at 150 deg.C, (C) a polysiloxane compound expressed by the formula II [R1 is R2 , a group of the formula III (R3 is a 1-9C organic group) or a group of the formula IV R5 is a 1-20C organic group may be containing O; R6 is H or a 1-9C organic group; (a) and (b) are each 0-300 and 0<(a+b)<=300}, etc.; R2 is a 1-10C alkyl or aryl, etc.; 0<=(1)<=30; 0<=(m)<=100; 1<=(l+m)<=130; 5<=(l+m+n)<=500], (D) a hardening accelerator and (E) molten silica powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an epoxy resin composition for semiconductor encapsulation having excellent moldability and solder resistance.

[0002]

2. Description of the Related Art As a method for encapsulating semiconductor elements such as ICs and LSIs, a method by transfer molding of an epoxy resin has been employed as a method suitable for low cost and mass production for a long time. Improvements have been made by improving the phenol resin. However, in the recent market trend of miniaturization, weight reduction, and high performance of electronic devices, the integration of semiconductors has been increasing year by year, and the surface mounting of semiconductor packages has been promoted. Demands on compositions (hereinafter referred to as resin compositions) are becoming more and more severe. For this reason, a problem which cannot be solved by the conventional resin composition has come out. The biggest problem is the adoption of semiconductor package surface mounting, which causes the package to be exposed to high temperatures of 200 ° C or more during the solder immersion or reflow process, causing the package to crack, causing the chip, lead frame, and inner leads to be damaged. Various plated joints, or L
In the case of a package having an OC structure, peeling occurs at each interface between a polyimide tape adhesive or the like and a sealing resin, and this is a phenomenon in which reliability is significantly reduced.

Further, in recent years, the thickness of the resin composition occupying in the package has been further reduced with the reduction in the thickness of the package, and a TSOP having a thickness of 1 mm is becoming the mainstream for packages for 64M and 256M DRAMs. In these thin packages, it is important that the package filling property of the resin composition during molding is good, there is little deformation of the gold wire, and there is no chip or lead frame deformation (called chip shift or die pad shift). It is necessary that the resin composition has excellent fluidity during molding. It is also particularly important that no bubbles remain (hereinafter referred to as voids) in the package after molding. In order to improve poor reliability due to soldering, the resin composition uses a resin with low melt viscosity and increases the filling amount of fused silica powder so that the molten resin composition during molding has a low viscosity and high flow A method of achieving low moisture absorption, high strength, and low thermal expansion while maintaining solderability and improving solder resistance has become common. As an epoxy resin, a crystalline epoxy resin which is solid at ordinary temperature and extremely lowers in viscosity when melted, particularly a biphenyl type epoxy resin as a typical example, has begun to be widely used (JP-A-5-175364, JP-A-5-343
570, JP-A-6-80763, etc.). However, conventional crystalline epoxy resins, especially biphenyl type epoxy resins, had the characteristic of low melt viscosity at the molding temperature, but their flowability was limited by the technical trend to increase the amount of fused silica powder even slightly. Had limitations. Furthermore, the biphenyl structure, which is the main skeleton, has a limit of the number of functional groups of two, and it is pointed out that the cured product characteristics such as the strength at heat and the glass transition temperature are low.

[0004]

DISCLOSURE OF THE INVENTION The present invention has a good filling property in a thin package and has a small amount of gold wire deformation, a chip shift and a die pad shift, that is, has a feature of high fluidity at the time of molding, and furthermore, has a The purpose of the present invention is to develop a semiconductor encapsulant which is free from voids in the package and has good cured product characteristics including solder resistance.

[0005]

That is, the present invention provides (A)
An epoxy resin containing 30% by weight or more of the epoxy resin represented by the general formula (1) in the total epoxy resin, (B) 150 ° C.
A phenol resin curing agent having a melt viscosity of 5 poise or less, particularly preferably a phenol resin curing agent represented by the general formula (3), (C) a polysiloxane compound represented by the general formula (2), and (D) a curing accelerator. , (E) a resin composition comprising a fused silica powder.

[0006]

Embedded image

[0007]

Embedded image

[0008]

Embedded image (M ≧ 0, n ≧ 0, and m + n ≧ 0)

Hereinafter, the present invention will be described in detail. The epoxy resin of the general formula (1) used in the present invention is usually called a stilbene structure type epoxy resin, and many studies have already been made and many reports have been published. This structure is a typical structure of a liquid crystal or a liquid crystalline polymer because the molecules have a rigid plane or rod-like structure and molecules are easily aligned. After curing, the resin composition using the epoxy resin having this structure has high strength at heat and low moisture absorption derived from the rigid molecular skeleton of the epoxy resin and the orientation of the molecules. It has the feature of excellent solderability. Further, since the molecules are easily oriented by the shear stress, the fluidity of the resin composition is high even in low-pressure transfer molding, and the filling property in a thin package is excellent.

Specific examples of the epoxy resin represented by the general formula (1) include, but are not limited to, the following.

Embedded image The epoxy resin that can be used in combination with the epoxy resin of the present invention,
Monomers, oligomers, and polymers generally having an epoxy group, for example, bisphenol A type epoxy resin,
Orthocresol novolak type epoxy resin, naphthalene type epoxy resin, triphenolmethane type epoxy resin, epoxidized resin of dicyclopentadiene modified phenols and the like, in particular, in order to obtain a resin composition having excellent solder resistance, Biphenol diglycidyl ether, tetramethyl biphenol diglycidyl ether,
Epoxy resins that exhibit crystallinity at room temperature, such as hydroquinone diglycidyl ether and tetramethylbisphenol F diglycidyl ether, are preferred. These epoxy resins may be used alone or as a mixture. The use ratio of the epoxy resin of the present invention is desirably 30% by weight or more based on the total epoxy resin. 30% by weight
If it is less than 30, the characteristic of high flowability at the time of molding, which is a characteristic of this crystalline epoxy, is not exhibited.

The phenolic resin curing agent used in the present invention is characterized by having a melt viscosity at 150 ° C. of 5 poise or less. When the melt viscosity at 150 ° C. exceeds 5 poise, the melt viscosity of the obtained resin composition increases, so that the fluidity during molding decreases, and the molded product in the mold is not filled, the wire is deformed, and the lead is not formed. Frame deformation (so-called pad shift) occurs. As a method for measuring the melt viscosity of a phenol resin at 150 ° C., an ICI cone-plate viscometer is simple and general. The phenolic resin curing agent refers to any monomer, oligomer, or polymer having a phenolic hydroxyl group capable of forming a crosslinked structure by performing a curing reaction with an epoxy resin, and specifically, a phenol novolak resin, a xylylene-modified phenol resin, Examples include terpene-modified phenolic resins, dicyclopentadiene-modified phenolic resins, bisphenol A, triphenolmethane, and the like, but are not limited thereto. These phenolic resin curing agents can be used alone or in combination. Also, the melt viscosity of 5 poise or less at 150 ° C. when various phenolic resin curing agents are used in combination does not indicate the numerical value of the melt viscosity of each phenolic resin alone, and the melt viscosity of all the used phenolic resin melt mixtures is not shown. Refers to viscosity.

However, a xylylene-modified phenol resin represented by the general formula (2) is preferable as a phenol resin curing agent that is particularly effective from the viewpoint of the solder resistance of the resin composition. This phenolic resin is usually phenol and p
-Xylylene glycol dimethyl ether or m-
It is synthesized by a polycondensation reaction with xylylene glycol dimethyl ether. This structure has low hygroscopicity, low modulus of elasticity when heated, and high adhesion to base materials such as lead frames and chips, reducing the stress generated when the absorbed moisture is vaporized by soldering. The effect of preventing package cracks is great. Furthermore, as the ratio of the m-xylylene skeleton to the p-xylylene skeleton in the structure of the general formula (2) increases, the resin composition has a feature that the strength at the time of heat is improved, and the resin composition tends to have more excellent solder resistance. .

The polysiloxane used in the present invention is used in combination with an epoxy resin represented by the general formula (1):
It is a component having particularly excellent effects. As described above, the epoxy resin represented by the general formula (1) is characterized by high fluidity due to its high degree of orientation, high strength upon curing after curing, and low water absorption. However, due to the high degree of orientation, even in a resin composition heat-kneaded with other components, there is a strong tendency to easily partially crystallize and become non-uniform. This partial crystallization occurs in a cooling step after heat kneading and in a state of storage at a low temperature, and cannot be prevented only by heat kneading with other components at a temperature higher than the melting point of the crystal. This crystallized portion easily melts at the molding temperature, forming a non-uniform liquid epoxy domain. For this reason, voids are generated due to a sudden change in volume, or unreacted epoxy resin components tend to form burrs during molding, which causes deterioration in moldability. As a means for preventing these, it is effective to add a polysiloxane which is partially compatible with the epoxy resin in a molten state and partially incompatible with a surfactant. This polysiloxane component is considered to have an effect of improving the affinity between the epoxy resin and a resin component other than the epoxy resin or an inorganic filler, and inhibiting crystallization of the epoxy resin.

S which is the main skeleton in the polysiloxane compound
The i-O-Si bond is not compatible with the epoxy resin, but the polyether bond or polycaprolactone bond and / or the organic functional group in the formula (2) is compatible with the epoxy resin. The polymerization degree (l + m + n) of the polysiloxane of the formula (3) is preferably from 5 to 500, and if it is less than 5, the compatibility with the epoxy resin is too good, so that no surface active effect can be obtained and the affinity with the inorganic filler is high. Is not improved, the heat resistance is lowered, and if it exceeds 500, the compatibility is inferior, so that it bleeds at the time of molding and causes mold contamination. Also, the number (l) of the organic functional group units in the polysiloxane is preferably 30 or less, and if it exceeds this, the fluidity during molding of the resin composition is reduced. Organic functional groups include glycidyl group, cyclohexene oxide group, carboxyl group,
An amino group is mentioned. The number (m) of polyether bond or polycaprolactone bond units in the polysiloxane is 1
It is preferably at most 00, and if it exceeds this, the moisture resistance may be reduced. (L + m) needs to be 1 or more, and is preferably 130 or less for the above reason. Furthermore, the repeating unit of polyether and the repeating unit of polycaprolactone have 30 units.
0 or less is preferable. If it exceeds 300, the viscosity rises remarkably, lowering the moldability and also lowering the moisture resistance.

The curing accelerator used in the present invention includes:
It refers to a catalyst that can act as a catalyst for a crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically includes an amidine-based compound such as 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, or tetraphenylphosphine. Examples thereof include organic phosphorus compounds such as phenylphosphonium / tetraphenylborate salts and imidazole compounds such as 2-methylimidazole, but are not limited thereto. These curing accelerators may be used alone or as a mixture.

The fused silica powder used in the present invention can be used in any of a crushed form and a spherical form. However, in order to increase the content of the fused silica powder and to suppress an increase in the melt viscosity of the resin composition, It is preferable to use mainly spherical silica. In order to further increase the content of the spherical silica, it is desirable to adjust the particle size distribution of the spherical silica to be wider. The amount of the fused silica powder is desirably 76 to 94% by weight in the total resin composition in view of the balance between moldability and solder resistance. If the amount of the fused silica is less than 76% by weight, the solder resistance is insufficient. If the amount exceeds 94% by weight, the flowability of the resin composition during molding is reduced even when a low-viscosity resin is used. Unfilled molded products in the mold, deformation of the gold wire, chip shift, and die pad shift occur. In addition to the essential components (A) to (E), the resin composition of the present invention may be colored as typified by a brominated epoxy resin, a flame retardant such as antimony trioxide, a coupling agent, and carbon black, if necessary. Agents, release agents such as natural waxes and synthetic waxes, and the like can be appropriately compounded. In order to obtain a resin composition, the components are mixed, heated and kneaded with a heating kneader or a hot roll, and then cooled and pulverized to obtain a desired resin composition.

Hereinafter, the present invention will be described specifically with reference to Examples. Example 1 3.8 parts by weight of an epoxy resin represented by the above formula (5) (melting point: 124 ° C.)

A xylylene-modified phenol resin represented by the formula (7-1) (where m is a mixture of at least 1 and m ≧ 6 components are 32%) (melt viscosity at 150 ° C. 2.8) Poise, hydroxyl equivalent 170) 4.2 parts by weight

Embedded image

0.5 parts by weight of a polysiloxane represented by the formula (8)

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Triphenylphosphine 0.2 parts by weight Spherical fused silica 88.0 parts by weight γ-glycidoxypropyltrimethoxysilane 0.5 parts by weight Antimony trioxide 1 part by weight Brominated bisphenol A type epoxy resin 1 part by weight Carnauba Wax 0.5 part by weight Carbon black 0.3 part by weight After mixing all of the above components with a mixer, kneading was performed 30 times using two rolls having a surface temperature of 90 ° C. and 45 ° C. to obtain a kneaded material sheet. Was cooled and pulverized to obtain a resin composition. The properties of the obtained resin composition were evaluated by the following methods. Table 1 shows the evaluation results.

Evaluation method Spiral flow: Measurement was performed using a mold for measuring spiral flow according to EMMI-1-66, at a mold temperature of 175 ° C., an injection pressure of 70 kg / cm ² , and a curing time of 2 minutes. Solder resistance: 100-pin TQFP package (package size: 14 x 14 mm, thickness: 1.4 mm, silicon chip size: 8.0 x 8.0 mm, lead frame: iron / nickel alloy (42 alloy), chip and inner lead A gold wire having a length of 5 μm was bonded between them), and transfer molding was performed at a mold temperature of 175 ° C. and an injection pressure of 75 kg / cm ² for 2 minutes, and post-cured at 175 ° C. for 8 hours. The molded product package is left for 168 hours in an environment of 85 ° C. and 85% relative humidity, and then 240 ° C.
For 10 seconds. Observe the package with a microscope and determine the number of external cracks
Expressed in% of the total number of packages. Voids: The number of voids present in a 100-pin TQFP package formed by solder resistance evaluation was observed using an ultrasonic flaw detector. The number of voids in one package is shown. Gold wire deformation: 100-pin TQF molded by soldering resistance evaluation
The P package was observed with a soft X-ray fluoroscope, and the deformation rate of the gold wire was expressed as% by flow amount / gold wire length. Heat strength: Flexural strength at 240 ° C. is determined according to JIS-K6911.
The test conditions were as follows. Moisture absorption: The moisture absorption was calculated from the rate of weight increase after leaving a molded disk of 50 mmφ and 2 mm thickness in an environment of 85 ° C. and 85% relative humidity for 168 hours.

Examples 2 to 4 and Comparative Examples 1 to 4 In place of the composition of Example 1, each component was blended in the ratio shown in Table 1, and mixed and kneaded in the same manner as in Example 1 to obtain a resin composition. Obtained. Evaluation was performed in the same manner as in Example 1. Table 1 shows the evaluation results. The epoxy resin (4) shown in Table 1 is the same as the above-described formula (4), and has a melting point of 146 ° C.
The structures of the phenolic resins (7-2) and (9) and the polysiloxanes (10), (11), (12) and (13) are shown below.

[0023]

Embedded image (However, m is a mixture of 1 or more, and the proportion of m ≧ 6 components is 60%. Melt viscosity at 150 ° C. 7.8 poise, hydroxyl equivalent 168)

[0024]

Embedded image (However, m / n = 3/1 by weight ratio, m + n is a mixture of 1 or more, and the proportion of m + n ≧ 6 components is 40%.)
Melt viscosity at 150 ° C 3.3 poise, hydroxyl equivalent 170)

[0025]

Embedded image

[0026]

[Table 1]

[0027]

The resin composition of the present invention can provide a molded article having excellent filling properties even in a thin package and having no voids. Furthermore, the semiconductor package sealed with the resin composition of the present invention has excellent heat resistance and low moisture absorption, and thus has excellent solder resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H01L 23/31

Claims (2)

[Claims] (A) an epoxy resin containing 30% by weight or more of the epoxy resin represented by the general formula (1) in the total epoxy resin, (B) a phenol resin curing agent having a melt viscosity at 150 ° C. of 5 poise or less, An epoxy resin composition for semiconductor encapsulation comprising (C) a polysiloxane compound represented by the general formula (2), (D) a curing accelerator, and (E) fused silica powder. Embedded image Embedded image 2. The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the phenol resin curing agent having a melt viscosity at 150 ° C. of 5 poise or less is a phenol resin curing agent represented by the general formula (3). Embedded image (M ≧ 0, n ≧ 0, and m + n ≧ 0)