JPH1149841A - Resin paste for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin paste excellent in heat bond strength and stress relaxation properties by including a liquid epoxy resin, a phenol curing agent, a latent curing agent, a curing promoter and an inorganic filler. SOLUTION: This paste comprises (A) 100 pts.wt. of a liquid epoxy resin composed of a liquid epoxy resin of the formula (m+n>=2) and an epoxy group- containing reactive diluent (e.g. phenyl glycidyl ether etc.), in the weight ratio of 50:50-90:10, (B) 10-30 pts.wt. of a phenol curing agent (e.g. bis phenol A etc.), (C) 0.5-5 pts.wt. of a latent curing agent (e.g. dicyandiamide etc.), (D) 0.1-10 pts.wt. based on 100 pts.wt. of the total of the components A, B and C of a curing promoter (e.g. trimethylenediamine etc.), which is a tertiary amine and (E) an inorganic filler (e.g. silver power or silica 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 bonding a semiconductor element such as an IC or an LSI to a metal frame or the like.

[0002]

2. Description of the Related Art With the recent remarkable development of the electronics industry, transistors, ICs, LSIs, and super LSIs have been evolving. With the spread of semiconductor products using these, improvement in workability and cost reduction in mass production have become important issues. Conventionally, semiconductor elements were replaced with Au-S
In general, they were joined by an eutectic method and then sealed by a hermetic seal to obtain a semiconductor product. However, in view of workability and cost during mass production, a resin encapsulation method has been developed and is now generally used. Along with this, a method using a solder material or a resin paste, that is, a mounting resin has come to be taken up as an improvement of the Au-Si eutectic method in the mounting step.

However, the solder method has low reliability,
The disadvantage is that the electrodes of the element are liable to be contaminated, and the use thereof is limited to power transistors and power IC elements that require high thermal conductivity. On the other hand, the mounting resin is superior in workability and reliability as compared with the soldering method, and the demand thereof is rapidly increasing.

In recent years, chips have been increasing in size due to the increase in the degree of integration of ICs and the like. On the other hand, since the 42 alloy frame which has been conventionally used is expensive, the copper frame is used for cost reduction purposes. Has come to be used. Here, the size of the chip such as IC is about 4
When it is larger than ~ 5 mm square, heating in the assembly process of IC etc., if the Au-Si eutectic method is used as a mounting method, chip cracks and cracks due to the difference between the coefficient of thermal expansion of the chip and the coefficient of thermal expansion of the copper frame Defective characteristics due to warpage have become a problem.

That is, the thermal expansion coefficient of silicon or the like as a chip material is 3 × 10 ⁻⁶ / ° C., whereas that of a 42 alloy frame is 8 × 10 ⁻⁶ / ° C. 20 × 10 ^-6
/ ° C. On the other hand, it is conceivable to use a mounting resin as the mounting method.However, with a conventional epoxy resin-based paste, since the thermosetting resin is three-dimensionally cured, the elastic modulus is high, and the distortion between the chip and the copper frame is reduced. Did not absorb.

If an epoxy resin which reduces the crosslink density during curing, for example, a resin containing a large amount of an epoxy monomer, is used, the modulus of elasticity can be lowered, but there is a disadvantage that the adhesive strength is reduced. Furthermore, a normal epoxy resin has a high viscosity, and if an inorganic filler is added thereto, the viscosity becomes too high, and threading occurs during dispensing, resulting in poor workability. When a large amount of solvent is added to improve workability, there is a problem that voids are generated.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the modulus of elasticity of a cured product without lowering the adhesive strength when hot, and to achieve chip cracking even in a combination of a large chip such as an IC and a copper frame. It is an object of the present invention to provide a resin paste which does not cause characteristic defects such as IC due to warpage and which is fast-cured and free from voids.

[0008]

According to the present invention, there is provided (A) a liquid epoxy resin having a weight ratio of a liquid epoxy resin represented by the general formula (1) to a reactive diluent having an epoxy group of 50:50 to 90:10. Resin, (B) phenol curing agent, (C)
The latent curing agent, (D) a curing accelerator which is a tertiary amine or a salt thereof, and (E) an inorganic filler are essential components, and the component (B) is 10 to 30 parts by weight based on 100 parts by weight of the component (A). Parts, component (C) is 0.5 to 5 parts by weight, and component (D) is 0.1 to 10 parts by weight with respect to a total of 100 parts by weight of components (A), (B) and (C). It is a resin paste for semiconductors.

[0009]

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The liquid epoxy resin (A) used in the present invention has a weight ratio of the liquid epoxy resin represented by the general formula (1) to the reactive diluent having an epoxy group of 50:50 to 90: 1.
There are various types of liquid epoxy resins represented by general formula (1) depending on the molecular weight.
Those having a small molecular weight and being liquid at room temperature are preferred in view of workability at the time of compounding and viscosity after compounding.

Reactive diluents having an epoxy group to be mixed with the liquid epoxy resin represented by the general formula (1) include n-butyl glycidyl ether, glycidyl versatate, styrene oside, ethylhexyl glycidyl ether, and phenyl glycidyl ether. And cresyl glycidyl ether, butylphenyl glycidyl ether and the like, and one or more of these can be used in combination.

The weight ratio of the liquid epoxy resin represented by the general formula (1) to the reactive diluent having an epoxy group is 50: 5.
It is preferably 0 to 90:10. When the weight ratio of the reactive diluent exceeds 50, the adhesive strength is weak, and when it is less than 10, the viscosity becomes high when the resin paste is used, and the workability is reduced.

In the present invention, other epoxy resins may be mixed and used. Other epoxy resins when mixed with the above liquid epoxy resin include, for example, bisphenol A, bisphenol F, phenol novolak, polyglycidyl ether, butanediol diglycidyl ether, and neopentyl glycol obtained by reacting cresol novolaks with epichlorohydrin. Aliphatic epoxies such as aliphatic epoxies such as diglycidyl ether, heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, dicyclopentadiene dioxide, and alicyclic diepoxy-adipate are among these. Can be used in combination with one or more of them.

The phenol curing agent (B) used in the present invention is used as a curing agent for an epoxy resin. The phenol curing agent used in the present invention desirably has two or more active hydrogen groups per molecule which react with epoxy groups and participate in crosslinking. Examples of such phenol compounds include bisphenol A, bisphenol F, bisphenol S, tetramethylbisphenol A, tetramethylbisphenol F, tetramethylbisphenol S, dihydroxydiphenyl ether, dihydroxybenzophenone, o-
Monohydric phenols such as hydroxyphenol, m-hydroxyphenol, p-hydroxyphenol, biphenol, tetramethylbiphenol, ethylidene bisphenol, methylethylidenebis (methylphenol), hexidenehexidenebisphenol, phenol, cresol, xylenol Phenol novolak resin obtained by reacting formaldehyde with a dilute aqueous solution under strong acidity, initial condensate of monohydric phenols with polyfunctional aldehydes such as acrolein and glyoxal, and resorcinol, catechol, hydroquinone, etc. Of polyhydric phenols and formaldehyde under acidic conditions, and these may be used alone or as a mixture.

The amount of the phenol curing agent (B) to be used is preferably from 10 to 30% by weight based on the liquid epoxy resin (A) from the viewpoint of adhesiveness and low stress.

The latent curing agent (C) used in the present invention is used as a curing agent for epoxy resins. It is. When a latent curing agent is used, the adhesive strength when heated becomes significantly higher than when cured with a phenol curing agent alone. Further, since the latent curing agent has a smaller equivalent weight than the phenol curing agent, it is possible to obtain a paste which is not so high in viscosity when used in combination and which has excellent preservability due to the latent curing agent. The amount of the latent curing agent (C) is 0.5 to 5% by weight based on the total epoxy resin.
It is preferred to use. If it is less than 0.5% by weight, the adhesive strength upon heating is weak, and if it exceeds 5% by weight, the low stress property is undesirably reduced.

The curing accelerator used in the present invention is a tertiary amine or a salt thereof, such as dimethylbenzylamine, trisamine or the like.
(Dimethylaminomethyl) phenol, alicyclic superbases,
Desirably, it is a salt of at least one tertiary amine selected from the group of imidazoles with phenols or basic acids. Alicyclic superbases are trimethylenediamine, 1,8
-Diazabicyclo (5,4,0) undecene-7, dodecahydro-1,4,7,9b tetraazaphenalene and the like. The imidazoles are those obtained by introducing a substituent such as methyl, ethyl, propyl or a long-chain alkyl group up to C17 or a phenyl group at the 2- and / or 4-position. Those that form salts with these tertiary amines include phthalic acid (o, m, p), tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid, hexahydrophthalic acid, trimellitic acid, adipic acid, succinic acid , Maleic acid, basic acids such as itaconic acid, or resorcinol, pyrogallol, hydroquinone, phenol, bisphenol A,
Phenols such as bisphenol F, bisphenol S, and low molecular novolak. These tertiary amine salts are used in an amount of 0.1 to 1 with respect to the total amount of the liquid epoxy resin (A), the phenol curing agent (B), and the latent curing agent (C).
It is desirable to use 0% by weight. When the amount is less than this, the accelerated curing is insufficient, and when the amount is more than this, there is a possibility that the preservability may be deteriorated though the curing is not accelerated so much, and neither is desirable.

The inorganic filler (F) used in the present invention includes silver powder, silica filler and the like. Silver powder is used to impart conductivity, and the content of ionic impurities such as halogen ions and alkali metal ions is preferably 10 ppm or less. The shape of the silver powder may be flake, resin, sphere or the like. Depending on the viscosity of the required paste, the particle size of the silver powder used varies, but the average particle size is usually
Those having a size of 2 to 10 μm and a maximum particle size of about 50 μm are preferred.
In addition, a mixture of relatively coarse silver powder and fine silver powder can be used, and various shapes may be appropriately mixed.

The silica filler used in the present invention has an average particle size.
It has a maximum particle size of 50 μm or less with a size of 1 to 20 μm. When the average particle size is 1 μm or less, the viscosity increases, and when the average particle size is 20 μm or more, the resin component flows out at the time of coating or curing, which is not preferable because bleeding occurs. If the maximum particle size is 50 μm or more, when applying the paste with a dispenser, the outlet of the needle is blocked and long-term continuous use cannot be performed. Further, a mixture of a relatively coarse silica filler and a fine silica filler may be used, and various shapes may be appropriately mixed. Further, an inorganic filler other than the present invention may be used in order to impart required properties.

The resin paste according to the present invention may contain a silane coupling agent, a titanate coupling agent, a pigment, a dye, a defoaming agent, a surfactant, a solvent, etc., as long as the properties according to the intended use are not impaired. Additives can be used. The production method of the present invention includes, for example, premixing each component, using a three-roll or the like to obtain a paste, and deconcentrating in a vacuum.

[0021]

EXAMPLES The present invention will be described specifically with reference to examples. The mixing ratio of each component is parts by weight.

Examples 1 to 8 and Comparative Examples 1 to 10 Each component having the composition shown in Table 1 was mixed with an inorganic filler and kneaded with a three-roll mill to obtain a resin paste. After defoaming this resin paste at 2 mmHg for 30 minutes in a vacuum chamber,
Various performances were evaluated by the following methods. Show evaluation results
Shown in 1.

Raw material components used: Liquid epoxy resin represented by the general formula (1) (epoxy A): viscosity 2000 mPa · s, epoxy equivalent 270

[0024]

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Bisphenol A type epoxy resin (BPA): viscosity 9000 mPa · s, epoxy equivalent 185 bisphenol F type epoxy resin (BPF): viscosity 5000 mPa · s, epoxy equivalent 170 reactive diluent: phenyl glycidyl ether Curing agent (B): Bisphenol F ・ Latent curing agent (C): Dicyandiamide (DDA) ・ Curing accelerator (D): 1,8-diazabicyclo (5,4,0) undecene-7 (DBU) ・ Inorganic Filler (F): Silver powder: Flake-shaped silica filler with particle diameter of 0.1 to 50 μm and average particle diameter of 3 μm: Silica filler with average particle diameter of 5 μm and maximum particle diameter of 20 μm

Evaluation method Viscosity: 25 using an E-type viscometer (3 ° cone)
The viscosity was measured at a temperature of 2.5 ° C. and a temperature of 2.5 ° C., and the viscosity was determined. Elastic modulus: Paste 10m width on Teflon sheet
m length about 150mm thickness 100μm, 200 ℃
After curing in an oven for 60 minutes, the modulus of elasticity was calculated from the initial gradient of the stress-strain curve obtained by measuring with a tensile tester a test length of 100 mm and a pulling rate of 1 mm / min. Adhesive strength: A silicon chip of 2 × 2 mm was mounted on a copper frame using a paste and cured in an oven at 200 ° C. for 60 minutes. After curing, the die shear strength under heat at 25 ° C. and 250 ° C. was measured using a mount strength measuring device. Warpage amount: A silicon chip of 6 × 15 × 0.3 mm is mounted on a copper frame (200 μm thick) with a conductive resin paste and cured at 200 ° C. for 60 minutes, and then the warpage of the chip is measured with a surface roughness meter (measuring length 13 mm). Was measured. Pot life: The number of days until the viscosity when the resin paste was allowed to stand in a thermostat at 25 ° C. increased to 1.2 times or more the initial viscosity was measured.

[0027]

[Table 1]

[0028]

[Table 2]

In Examples 1 to 8, pastes having excellent adhesive strength at heat, low stress (low elastic modulus, low warpage) and long pot life can be obtained. Comparative Example 1 uses a bisphenol A type epoxy resin. Poor low stress properties, large warpage, and chip cracks. In Comparative Example 2, a bisphenol F type epoxy resin was used, so that the low stress property was poor, the amount of warpage was large, and chip cracks occurred. In Comparative Example 3, the content of the reactive diluent was large, and the adhesive strength was significantly reduced. In Comparative Example 4, the amount of the reactive diluent was small, the viscosity was significantly increased, and the workability was reduced. Comparative Example 5
The amount of the phenol curing agent is small, and the adhesive strength is significantly reduced. In Comparative Example 6, the amount of the phenol curing agent was large, the amount of warpage was large, and chip cracks occurred. In Comparative Example 7, the amount of the latent curing agent was small, and the adhesive strength was significantly reduced. In Comparative Example 8, the amount of the latent curing agent was large, the amount of warpage was large, and chip cracks occurred. In Comparative Example 9, the amount of the curing accelerator was small, and the adhesive strength was significantly reduced. Comparative Example 10 had a large amount of the curing accelerator,
Pot life is significantly shortened.

[0030]

The resin paste for semiconductors of the present invention has a high adhesive strength when heated and an excellent stress relaxation property.
It is suitable for bonding large-sized chips such as
Characteristic defects such as ICs due to chip cracks and chip distortion in the assembly process can be prevented.

Claims (1)

[Claims] 1. A liquid epoxy resin wherein the weight ratio of the liquid epoxy resin represented by the general formula (1) to the reactive diluent having an epoxy group is 50:50 to 90:10.
(B) phenol curing agent, (C) latent curing agent, (D)
A curing accelerator, which is a tertiary amine or a salt thereof, and an inorganic filler (E) are essential components, and 10 to 30 parts by weight of component (B) and 0 to 100 parts by weight of component (A). 0.5 to 5 parts by weight, and the components (A), (B) and (C)
Component (D) is 0.1 to 10 parts by weight based on 100 parts by weight of
A resin paste for semiconductors, which is in parts by weight. Embedded image