JPH0967553A - Resin paste for die bonding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin paste for die bonding which hardly stains a substrate and is excellent in resistance to soldering crack. SOLUTION: This paste contains as the essential components an arom. diepoxy resin liq. at normal temp. and having a hydrolyzable chlorine content of 500ppm or lower, 4,4'-diamino-3,3'-diethyldiphenylmethane as the curative, 0.01-1wt.% (based on the resin) 1,8-diazabicyclo [5,4,0]undecene-7 and/or its salt, 0.05-5wt.% (based on the paste) superfine-particle silica powder having an average size of primary particles of 2-50nm and having silanol groups existing on the surface, and 10-90wt.% (based on the paste) an inorg. filler.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin paste for adhering a semiconductor element such as IC or LSI to a substrate or the like.

[0002]

2. Description of the Related Art With the remarkable development of the electronics industry in recent years, the degree of integration of circuits in transistors, ICs, LSIs, VLSIs and semiconductor devices has been rapidly increasing.
For this reason, the size of the semiconductor element, which has been conventionally about several mm on the long side, has been dramatically increased to about 10 mm. Further, as the lead frame, a copper material, which has a good thermal conductivity and is inexpensive, is becoming the mainstream from the conventional 42 alloy. On the other hand, the mounting of semiconductor products is performed by the surface mounting method, and the size of the semiconductor products themselves is becoming smaller and thinner due to higher density mounting. In accordance with such trends in semiconductor products, the performance requirements for the constituent materials of semiconductor products are also changing, and the reliability of bonding that has been conventionally required for die-bonding resin paste that bonds semiconductor elements and metal frames In addition, stress relaxation characteristics for absorbing and relaxing thermal stress due to the difference in thermal expansion coefficient between a large chip and a copper frame, and solder crack resistance characteristics due to surface mounting in a thin package are beginning to be required.

As conditions for the die-bonding resin paste to withstand solder cracking, there are items such as low stress, low water absorption, and low contamination. Of these items, low stress, low water absorption resin,
Extensive research and development on curing agents, additives, etc. have been made and put to practical use. On the other hand, regarding the stain resistance, the resin paste for die bonding is generally composed of a resin and a filler, but the particle size of the paste is limited in consideration of coating workability. The resin is a viscous liquid or solid, and it is necessary to add a diluent to reduce the viscosity to form a paste. Examples of the diluent include monoepoxy,
There are reactive diluents such as aliphatic polyepoxy and non-reactive diluents represented by solvents. In the former case, part of the gas is volatilized as outgas during curing of the paste,
The chip surface is easily contaminated, and the adhesion between the encapsulation resin and the substrate or chip surface when encapsulating with the encapsulation resin deteriorates, making use of the low stress property used in the encapsulation resin and paste. However, there is a drawback that interface peeling and package cracks easily occur when stress is applied. Although not related to solder cracking property, the reactive diluent is liable to volatilize and generally has a problem in working environment. For this reason, it is not preferable from an environmental point of view that exhaust must be sufficient during curing. On the other hand, when a non-reactive diluent such as a solvent is used, there are problems that the substrate and the chip are hardly contaminated, but voids are easily generated in the paste layer and the paste thickness is not constant. Therefore, it has been desired to develop a paste that does not use a diluent and has excellent solder cracking properties. As a countermeasure, there is a combination of a liquid epoxy resin, a liquid curing agent and a filler, but generally the pot life (the viscosity does not change at room temperature for 2 days or more) is short and it is difficult to apply it to actual work.

[0004]

SUMMARY OF THE INVENTION The present invention has a low pollution property,
It is intended to provide a resin paste for die bonding which is excellent in solder crack resistance.

[0005]

That is, according to the present invention, (A) a bifunctional aromatic epoxy resin which is liquid at room temperature and has a hydrolyzable chlorine content of 500 ppm or less, and (B) a curing agent of 4,4'-
Diamino-3,3'-diethyldiphenylmethane,
(C) 1,8-diazabicyclo [5,4,0] undecene-7 and / or a salt thereof, (D) ultrafine silica powder having an average primary particle size of 2 to 50 nm and having silanol groups on the surface , And (E) an inorganic filler as an essential component, and (C) is 0.01 to 1 with respect to 100 parts by weight of (A).
Parts by weight, 0.05 to 5% by weight of (D) in the total paste,
A resin paste for die bonding containing 10 to 90% by weight of (E).

The bifunctional aromatic epoxy resin used in the present invention is limited to being liquid at room temperature. Also,
The amount of hydrolyzable chlorine contained in the epoxy resin is 500pp
Although limited to m or less, the amount of chlorine extracted from the die bonding resin paste can be greatly reduced by using such an epoxy resin. The extracted chlorine causes the corrosion of the Amyl wiring on the surface of the semiconductor element, and the smaller the amount of extracted chlorine, the higher the reliability. To measure the content of hydrolyzable chlorine, 0.5 g of an epoxy resin is completely dissolved in 30 ml of dioxane, 5 ml of an IN-KOH solution (ethanol solution) is added, and the mixture is boiled under reflux for 30 minutes. To this, 100 ml of 80% acetone water was added, and further 2 ml of concentrated HNO ₃ was added, and
Potentiometric titration is performed with a 1N-AgNO ₃ aqueous solution.

The viscosity of the epoxy resin is preferably as low as possible in order to reduce the paste viscosity. Especially 600
Resins of 0 CPS (E-type viscosity measurement) or less are preferable. Examples thereof include low molecular weight types such as bis A type and bis F type epoxy resins. Next, the addition amount of aromatic amine 4,4'-diamino-3,3'-diethyldiphenylmethane as a curing agent is 0.9 to the equivalent of the epoxy resin.
It is preferably 1.1. If it is less than 0.9, the curability is poor, and if it exceeds 1.1, the pot life is affected.
Next, 1,8-diazabicyclo [5,4,0] undecene-7 (hereinafter referred to as DBU) and / or its salt has an effect of delaying the reactivity of the epoxy resin and the aromatic amine, particularly at room temperature. Found out. Examples of the salt include DBU phenol salt and organic acid salt. DBU
The amount added is 0.01 per 100 parts by weight of the epoxy resin.
-1 part by weight is preferred. If it is less than 0.01 part by weight, the effect of delaying is small, and if it exceeds 1 part by weight, the adhesion to the substrate after curing is impaired. Further, it has been found that the combined use of ultrafine silica powder having a silanol group-containing primary particle having an average particle diameter of 2 to 50 nm as a reaction retarder in combination with DBU and / or a salt thereof is effective in suppressing an increase in viscosity.
It is considered that the addition of this compound delays the reaction with the epoxy group because the silanol group and the amino group interact with each other. This effect does not affect the reactivity at the curing temperature. The amount of the ultrafine silica powder added is preferably 0.05 to 5% by weight based on the total paste. If it is less than 0.1% by weight, the delay of the reaction between the epoxy resin and the amine is small and the pot life becomes short. If it exceeds 5% by weight, the paste viscosity is too high to be practical.

Next, the inorganic filler is not particularly limited, but examples thereof include the following. If the paste after curing needs conductivity, Au, Ag, Cu, Ni
Etc., such as metal powder, carbon, graphite, etc. Next, when the paste after curing requires insulation, SiO ₂ , A
oxides such as l ₂ O ₃ ; metal nitrides such as AlN and BN; Si
There are metal carbides such as C and metal carbonates such as CaCO ₃ . In the case of conductive paste, the amount of inorganic filler added is
It is preferably from 70 to 90% by weight in the total paste, and when it is less than 70% by weight, the conductivity is difficult to develop, and when it exceeds 90% by weight, the viscosity of the paste becomes high, which is not preferable in coating work. Further, in the case of an insulating paste, it is preferably 10 to 90% by weight in the total paste. If it is less than 10% by weight, the adhesive strength will be insufficient, and if it exceeds 90% by weight, the viscosity of the paste will be too high to be suitable for practical use. In the present invention, a flexibility imparting agent, a defoaming agent, a coupling agent and the like can be used if necessary. As an example of the production method of the present invention, after premixing the components, kneading is performed using a three-roll mill, and after kneading, vacuum defoaming is performed to obtain a resin paste. Hereinafter, the present invention will be described specifically with reference to Examples. The mixing ratio is part by weight.

The present invention will be specifically described below with reference to examples.
The mixing ratio is part by weight. Examples 1 to 3 Glycidyl ether obtained by reaction of bisphenol F and epichlorohydrin (hydrolyzed chlorine amount 150 p
pm, epoxy equivalent 165, viscosity 3,000 cps)
(Component A), 4,4′-diamino-3,3′-diethyldiphenylmethane (Component B), phenol salt of 1,8-diazabicyclo [5,4,0] undecene-7 (Component C), primary particles 12 μm Ultrafine silica powder (D component), flake silver powder with an average particle size of 3 μm (E component), γ
-Glycidoxypropyltrimethoxysilane (F component) was blended in a ratio shown in Table 1, and sufficiently kneaded with a three-roll to defoam to obtain a conductive paste, and various performances were evaluated.

Evaluation method Viscosity: The viscosity was measured at a rotation speed of 2.5 rpm using an E-type viscometer at 25 ° C. Volume resistivity: paste 4 mm wide on glass slide,
Apply to a thickness of 30 μm, and place in an oven at 160 ° C. for 120
After curing for one minute, the volume resistivity of the cured product was measured. Adhesive strength: Using a paste, a 2 × 2 mm silicon chip was mounted on a copper frame and cured in an oven at 160 ° C. for 120 minutes. After curing, the die shear strength during heating at 250 ° C. was measured using a push-pull gauge. Further, the cured sample was subjected to a water absorption treatment at 85 ° C. and a relative humidity of 85% for 72 hours, and the die shear strength under heat at 240 ° C. was measured. Water absorption rate: 50 × 50 paste on Teflon sheet
After coating so as to have a thickness of 0.1 mm and curing in an oven at 200 ° C. for 60 minutes, 85 ° C., relative humidity 85%, 72
The water absorption treatment was performed for a period of time, and the water absorption rate was calculated from the weight change before and after the treatment. Void: A 10 mm × 10 mm glass chip was mounted on a lead frame, and after curing, a void was checked by appearance. Good voids of 15% or less of the adhered area, 15%
Anything over 100 was regarded as defective. Package crack resistance: A package molded under the following conditions using a biphenol type epoxy resin / phenol novolac resin-based encapsulating material containing about 78% silica filler was subjected to water absorption treatment at 85 ° C. and 85% relative humidity for 168 hours. After that, IR reflow (240 ℃, 10 seconds),
The number of internal cracks was measured by observing the cross section and used as an index of package crack resistance. Package: 80 pQFP (14 x 20 x 2 mm thickness) Chip size: 7.5 x 7.5 mm (Aluminum wiring only) Lead frame: 42 alloy Form: 175 ° C, 2 minutes Post mold cure: 175 ° C, 4 hours n Number: 12 Pot life: The paste was stored at 25 ° C., the viscosity after 48 hours was measured, and those with an increase of 20% or less of the initial value were evaluated as good, and those exceeding 20% were evaluated as poor.

Example 4 An insulating paste was obtained with the composition shown in Table 1 except that spherical silica filler (G component) having an average particle size of 1 μm was used instead of silver powder. Comparative Examples 1 to 6 Pastes were prepared according to the formulations shown in Table 2, and various performances were evaluated in the same manner as in Examples. Table 2 shows the evaluation results. Comparative Example 7 Epoxy resin (A component of Example) 10.7 parts by weight Reactive dilution (t-butylphenyl glycidyl ether) 7.2 parts by weight Phenol novolac resin 1.8 parts by weight Dicyandiamide 0.2 parts by weight DBU phenol 0.1 parts by weight of salt (component C in the example) 80 parts by weight of silver powder in the example were kneaded in the same manner as in the example to obtain a paste. Various performances were evaluated in the same manner as in the example. Table 2 shows the evaluation results. Comparative Example 8 Epoxy Resin (Component A of Example) 10.7 parts by weight Butyl cellosolve acetate (solvent) 7.2 parts by weight Phenol novolac resin 1.8 parts by weight Dicyandiamide 0.2 parts by weight Phenol salt of DBU (C of Example) Component) 0.1 parts by weight 80 parts by weight of the silver powder of the example was kneaded in the same manner as in the example to obtain a paste. Various performances were evaluated in the same manner as in the example. Table 2 shows the evaluation results.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

EFFECTS OF THE INVENTION The paste of the present invention has excellent storage stability and does not contain a reactive diluent and / or a non-reactive diluent. No voids in the material layer, and excellent solder crack resistance.

Claims (1)

[Claims] 1. A bifunctional aromatic epoxy resin (A) which is liquid at room temperature and has a hydrolyzable chlorine content of 500 ppm or less, and (B).
4,4'-diamino-3,3'-diethyldiphenylmethane as a curing agent, (C) 1,8-diazabicyclo [5,4,0] undecene-7 and / or a salt thereof,
(D) An ultrafine silica powder having an average particle size of primary particles of 2 to 50 nm and having silanol groups on the surface, and (E) an inorganic filler as essential components, and (A) is 100 parts by weight (C). 0.01 to 1 part by weight, 0.05 to 5% by weight of (D) and 10 to 90% by weight of (E) in the total paste.