JPS6375025A - Epoxy resin composition for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain the titled composition having reduced stress without deteriorating water-vapor resistance, by blending a novolak type epoxy resin composition containing a large amount of an inorganic filler with specific components such as a specific butadiene-acrylonitrile copolymer, etc. CONSTITUTION:(A) An epoxy resin composition which comprises a novolak type epoxy resin as a base resin and contains 50-85wt% inorganic filler (e.g. silica, etc.) is blended with (B) 1-30pts.wt. based on 100pts.wt. epoxy resin composition of a butadiene-acrylonitrile copolymer which is shown by formula (x, y and z are positive integer, 1<=x/y<=20 and z is 5-20) and contains a terminal COOH group, (C) 25-75pts.wt. phenolic curing agent (preferably novolak type phenolic resin), (D) 0.5-5pts.wt. phosphine type curing promoter (e.g. triphenylphosphine, etc.) and (E) 0.1-15pts.wt. coupling agent.

Description

[Detailed Description of the Invention] [Summary of the Invention] The present invention provides an epoxy resin composition for semiconductor encapsulation,
The moisture resistance of the resin is improved by using a novolac type epoxy resin as the base resin and further containing a predetermined amount of butadiene-acrylonitrile (a) copolymer, a phenolic curing agent, a phosphine curing agent, and a camping agent. The aim is to overcome various obstacles caused by stress by reducing the stress while maintaining the stress.

[Industrial application field]

The present invention relates to an epoxy resin composition for semiconductor encapsulation, and more particularly to an epoxy resin composition for semiconductor encapsulation that suppresses stress that causes deformation of aluminum wiring, passivation cranks, package cracks, etc.

[Prior Art and Problems to be Solved by the Invention] Today, the mainstream method for sealing electronic components such as ICs and LSIs is to use a thermosetting resin. this is,
This is because sealing using resin is cheaper and easier to mass produce than hermetic sealing using glass, metal, or ceramics. As a base resin for semiconductor encapsulation resin compositions, it has excellent moldability, moisture resistance, and electrical properties.
Cheap epoxy resins are most commonly used.

However, as chips become larger and patterns become finer due to increased integration of LSIs, and packages become smaller due to high-density packaging, problems have arisen that cannot be addressed by conventional epoxy resin compositions for semiconductor encapsulation. In other words, since a resin-sealed LSI is made of resin and a Si chip, which are materials with different thermal expansion coefficients, stress acts between these materials, causing the LSI to
The problem is that I is damaged. This stress increases as the chip becomes larger, and as the pattern becomes finer, it becomes more susceptible to damage. Damage modes of resin-sealed LSIs due to stress include deformation and disconnection of aluminum wiring, puffy basic crank, and package crank.

For this reason, it has become necessary to develop a resin for semiconductor encapsulation that can suppress the stress applied to the chip.

Stress (σ) that the Si chip receives from the sealing resin (cured material)
is expressed by the following equation (1) by rough approximation.

σ-k・α・E-Tg...(1) k: Constant of proportionality α: Coefficient of thermal expansion of sealing resin E: Modulus of elasticity of sealing resin Tg: Glass transition temperature stress of sealing resin (1) Since it can be approximated by the formula, the following method has been considered as a conventional method for reducing stress in semiconductor sealing resin. That is, (a) lowering the coefficient of thermal expansion;

(b) Decrease the elastic modulus.

(c) Lowering the glass transition temperature.

There are 03 types. However, although lowering the glass transition temperature of the sealing resin reduces stress, it also causes deterioration of moisture resistance, heat resistance, mechanical properties, etc., so essentially as a means of reducing stress, ( a) and (b) are possible.

Adding a large amount of inorganic filler can be considered as an effective means of lowering the coefficient of thermal expansion of the cured resin. However, when a large amount of inorganic filler is added, although the coefficient of thermal expansion decreases, the modulus of elasticity also increases, so there is almost no change in stress after all. In addition, if the amount added is too large, the melt viscosity of the resin will increase, resulting in deformation and breakage of the bonding wire, and unfilled areas where the resin does not reach every corner of the mold, resulting in a significant deterioration in workability during molding. do.

Furthermore, as a means for reducing the elastic modulus of the sealing resin, a method of adding a flexibility imparting agent has been proposed. However, this method lowers the glass transition temperature of the cured resin,
It has the disadvantage that moisture resistance, heat resistance, mechanical properties and high temperature electrical properties deteriorate.

Additionally, silicone is added as a method of reducing the elastic modulus without lowering the glass transition temperature, but silicone has high moisture permeability, resulting in defects such as deterioration of moisture resistance and repelling of printing ink.

That is, in the prior art, when trying to reduce stress, it is extremely difficult to reduce stress without deteriorating other properties such as deterioration of moisture resistance.

[Means and effects for solving the problems] The present invention has the following features:
In an epoxy resin composition for semiconductor encapsulation that uses a novolac type epoxy resin as a base resin and contains an inorganic filler in an amount of 50 to 85 wt% based on the entire composition, (1) the following formula (a ): (In the formula, X+y +2 is a positive integer, and 1≦□≦20
and 2 is 5 to 20), 1 to 30 parts by weight of a butadiene-acrylonitrile copolymer having a carboxyl group at the terminal, (2) 25 to 75 parts of a phenolic curing agent, and (3) phosphine curing Accelerator 0.5-5 parts (4) Campling agent 0.
1 to 15 parts.

Further, in the present invention, an inorganic filler having a particle size of 1 μm or less is included in an amount of 1 to 30 wt% of the total inorganic filler.

In the present invention, butadiene represented by the molecular formula (a)
It is essential to add acrylonitrile copolymer (NBR). Such a copolymer preferably has 5 to 20 repeating units and a molecular weight of 1,800 to 7,000. The butadiene-acrylonitrile copolymer has a high flexibility imparting ability, and the terminal carboxyl group easily reacts with the novolac type epoxy resin of the base material, so it is possible to lower the elastic modulus of the sealing material without lowering the glass transition temperature. Can be done.

Furthermore, unlike silicone, even if a butadiene-acrylonitrile copolymer is added, the marking ink will not bleed. As can be seen from the molecular formula (a), the butadiene-acrylonitrile copolymer used in the present invention does not Since there are hydrophilic groups such as -COOH and -CN, it is expected that the moisture resistance will deteriorate, but the water absorption rate will only increase slightly and will not have any adverse effect on the semiconductor device.

The butadiene-acrylonitrile copolymer is added in an amount of 1 to 30 parts per 100 parts of the epoxy resin. This is because if it is less than 1 part, no effect will be seen, and if it exceeds 30 parts, not only will the mechanical properties deteriorate, but there is also a risk that it will not be compatible with the epoxy resin. Preferably, 5 to 20 parts of butadiene-acrylonitrile copolymer may be added.

The epoxy resin used in the present invention is not particularly limited as long as it is a novolac type epoxy resin, but Talesol novolanc type is preferred from the viewpoint of moisture resistance, heat resistance, and mechanical strength.

As the curing agent, for example, phenolic resin can be used. Examples of the phenolic curing agent include novolac type phenolic resins such as phenol novolac, talesol novolac, and nonylphenol novolac, and bisphenol A. Among these, novolac type phenolic resins are preferred from the viewpoint of moisture resistance. The amount of the agent added is 25 to 75 parts per 100 parts of the epoxy resin from the viewpoint of moisture resistance, mechanical properties, heat resistance, etc.

Furthermore, it is essential to use a phosphine-based curing accelerator to promote the reaction between the epoxy resin and the curing agent.

Examples of curing accelerators used in the reaction between epoxy resins and phenolic curing agents include tertiary amines such as triethanolamine and tetramethylpencune diamine, quaternary amines such as cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, and trimethylammonium chloride. ammonium salt, 2-methylimidazole, 2
- imidazole compounds such as undecylimidazole, 2-methyl-4-ethylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1'))ethyl-8-triazine, or triphenylphosphine, methyl The 0 or more curing accelerators include phosphine compounds such as diphenylphosphine, tributylphosphine, and phenylphosphine, and tetraphenylborate salts such as triphenylphosphine tetraphenylborate and triethylamine tetraphenylborate, all of which have a hydrophilic group, Although it is thought that the moisture resistance of the sealing resin may be deteriorated, it has been found that the use of a phosphine curing accelerator has the best moisture resistance. Therefore, in the present invention, by using a phosphine curing accelerator together with NBR, moisture resistance and stress can be maintained.

The phosphine curing accelerator used in the present invention is
The above-mentioned compounds include triphenylphosphine, methyldiphenylphosphine, tributylphosphine, phenylphosphine, triphenylphosphine tetraphenylborate, etc., but triphenylphosphine is preferred from the viewpoint of moisture resistance and workability. In the invention, the material is not particularly limited as long as it is a phosphine and has the effect of promoting the reaction between the epoxy resin and the curing agent.

The amount of the phosphine curing accelerator used in the present invention is 0.5 to 5 parts. The reason for this is that if it is less than 0.5 parts, the effect of promoting curing is weak and the curing time becomes longer. Moreover, if it exceeds 5 parts, the curing time of the sealing resin becomes too short. That is, if the amount of the phosphine curing accelerator added is outside the above range, workability may deteriorate.

In the present invention, inorganic fillers are also used. Silica, alumina, calcium carbonate, etc. are used as the inorganic filler, but silica powder is preferred in order to reduce the coefficient of thermal expansion. Further, the amount of the inorganic filler added is preferably within the range of 50 to 85 wt% of the entire composition. The reason for this is that the amount of inorganic filler added is 50wt%.
If it is less than that, not only will the thermal conductivity and mechanical properties deteriorate,
This is because there is a significant decrease in workability such as the outflow of Paris, and if it is added in excess of 85 wt%, the flowability decreases and there is a possibility that the bonding wire may be deformed or disconnected.

Furthermore, the particle size distribution of the inorganic filler used in the present invention is limited. That is, it is essential that particles with a particle size of 1 μm or less be in the range of 1 to 30 wt% of the entire filler. This means that particles with a particle size of less than 1 μm are
If it is less than t%, the occurrence of paris becomes significant, and
This is because if it exceeds wt%, the fluidity of the composition when it is melted will deteriorate significantly.

In addition, in order to improve the moisture resistance of the resin, a coupling agent is used, such as a silane coupling agent such as 3-glycidoxyprobyltrimethoxysilane or tetraoctyl bis(phosphite).
Add a titanium-based coupling agent such as titanate.

The amount of the coupling agent added depends on the amount and specific surface area of the inorganic filler used and the minimum scratched area of the coupling agent, but in the present invention, 0.1 to 15 parts is preferably used.

Furthermore, carnauba wax, stearic acid and its metal salts, montan wax, etc. may be added as a mold release agent, brominated epoxy resin, antimony trioxide, etc. may be added as a flame retardant, and carbon black, etc. may be added as a pigment.

The epoxy resin composition for semiconductor encapsulation of the present invention can be prepared from the above-mentioned components using conventional means such as a roll, a niegu, an extruder, and the like.

Hereinafter, one embodiment of the present invention will be described, but the present invention is not limited thereto.

〔Example〕

The raw materials used to produce the epoxy resin composition of the present invention are as follows. Epoxy resin: Cresol novolac type epoxy resin Epoxy equivalent: 200, softening point: 72°C Nippon Kayaku 91EOCN-1025 Hardening agent: Phenol novola Hydroxyl group equivalent: 103, softening point: 93°C Curing accelerator A Nitriphenylphosphine Wako Pure Chemical Industries ■ Curing accelerator B: 2,4-diamino-6-(2'-methylimidazolyl-(1')) ethyl-8- Triazine Shikoku Kasei side 2MZ-AZINE Filler Nijirikakimon (IDEP-002 (particle size 1.um or less 10wt%)
) Coupling agent: 3-glycidoxyprobyltrimethoxysilantiso@S-510 Mold release agent: Ester wax Hoechst Japan side Hoechst wax E Flame retardant: Brominated epoxy resin Flame retardant aid: Trioxygenated antimony pigment : Carbon blank additive A: Butadiene-acrylonitrile copolymer molecular weight M n = 3500 Ube Industries HIlycar CTBN-1008 USP Additive B: Silicone East Silicone ■ 5116018 Additive C: Silicone Chisso@Ps-513 Examples 1 to 3 and comparison Table 1 shows the composition of the raw materials used in Examples 1 to 4. The compositions shown in the table were prepared by kneading all of these raw materials using a pressurized double-arm kneader. In addition, the test pieces were prepared as follows.

First, the composition obtained by mixing and purification was made into powder of 8 mesh passes, and then 2 tons/c11! φ35■
1 tablet. This tablet was transferred molded (175℃, 60 kg/CIA, 2.5 m
1n) was after-cured at 175°C for 8 hours.

Characteristics of the composition thus obtained were evaluated as follows.

Flexural modulus: Compliant with JIS K 6911.

Thermal expansion coefficient: Measured by TMA (thermo mechanical testing machine) method.

Glass transition temperature: Measured by TMA (thermo-mechanical test 81) method.

Water absorption rate...PCT (Pressure test:
121℃, 2atm, 100%R)l,
Weight increase crack in test piece due to 168h) Thermal shock test using 16-pin SOP molded with 5x6 crane semiconductor chips (150°C, 2m1n--196°C, 2m1n.

Package Clarac PCT electrolytic corrosion test after 500 cycles... MOS type LSI molded 1
PCT (121'C, 2atm) when applying IHIAS (DS20v) using 6 pin:/DIP.

100% RH, 1000 h), it was checked whether the device operated normally.

Pipe stress: The stress measurement method for semiconductor encapsulating resins described in Japanese Patent Application Sho was followed.

Table 1 shows the results of Examples and Comparative Examples of the present invention.

According to Table 1, it can be seen that all of the Examples satisfy both lower stress and moisture resistance than the Comparative Examples.

According to the present invention, by adding several types of substances including butadiene-acrylonitrile copolymer with high flexibility imparting ability, it is possible to obtain the effect of reducing stress without deteriorating moisture resistance. can.

Claims (1)

[Claims] 1. In an epoxy resin composition for semiconductor encapsulation, which uses a novolac type epoxy resin as a base resin and contains an inorganic filler in an amount of 50 to 85 wt% based on the total composition, based on 100 parts by weight of the base resin, (1) The following formula (a): ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, x, y, and z are positive integers, 1≦x/y≦20, and z is 5 to 20. 1 to 30 parts by weight of a butadiene-acrylonitrile copolymer having a carboxyl group at the terminal, represented by (4) Epoxy resin composition 2 for semiconductor encapsulation containing 0.1 to 15 parts of a coupling agent, an inorganic filler with a particle size of 1 μm or less based on 1 part of the entire inorganic filler.
The epoxy resin composition for semiconductor encapsulation according to claim 1, which contains ~30 wt%.