JP2001106873A - Resin paste for semiconductor and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin paste for semiconductor which can be cured rapidly, exhibits a high adhesive strength at high temperatures, is excellent in stress relaxation properties, and is suitable for bonding a large chip to a copper frame. SOLUTION: This resin paste comprises a combination of two liquid epoxy resins, a liquid phenol resin, a latent curing agent, an imidazole compound, and an inorganic filler provided the combination of epoxy resins may be diluted with a reactive diluent having epoxy groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 Recent remarkable developments in the electronics industry have evolved into transistors, ICs, LSIs, and ultra-LSIs. The integration of circuits in these semiconductor devices has rapidly increased, and mass production has become possible. 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.

Further, in recent years, the chip has been increased 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, copper is used for cost reduction purposes. Frames have 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 the mounting method, chip cracks and cracks may occur 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, ordinary epoxy resins have high viscosity, and if an inorganic filler is added to this, the viscosity will be too high, threading will occur at the time of dispensing, workability will deteriorate, and if a large amount of solvent is added to improve workability, There was a problem that voids were generated. Further, the conventional mounting resin had to be heat-treated in an oven at 150 to 200 ° C. for 1 to 2 hours for curing. Recently, there has been an increasing demand for in-line curing in an oven within 30 minutes in order to streamline the semiconductor assembly process. There is a method of adding a large amount of a curing accelerator to achieve rapid curing. Had the disadvantage that the adhesive strength was low.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an IC which is not affected by chip cracks or warpage even in a combination of a large chip such as an IC and a copper frame without lowering the adhesive strength when heated.
It is an object of the present invention to provide a resin paste which does not cause poor properties such as the above, is fast-curing, and does not generate voids.

[0008]

SUMMARY OF THE INVENTION The present invention aims at lowering the modulus of elasticity without lowering the adhesive strength when heated, and comprises a liquid epoxy resin represented by the general formula (1) and a liquid epoxy resin represented by the general formula (2). Weight ratio of the liquid epoxy resin to be used is 5:95 to 80: 2.
(A) an epoxy resin which is 0, (B) a liquid phenol resin represented by the general formula (3), (C) a latent curing agent,
It comprises (D) an imidazole compound and (E) an inorganic filler.
It is a resin paste for semiconductors containing up to 30 parts by weight, 0.5 to 5 parts by weight of the component (C), and 0.5 to 10 parts by weight of the component (D). Further, the present invention is a semiconductor device manufactured using the above-mentioned resin paste for a semiconductor.

[0009]

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[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The 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 liquid epoxy resin represented by the general formula (2) of 5: 95-80. : 20 is desirable. The compound represented by the general formula (1) has various types depending on the molecular weight. However, a compound having a small molecular weight and being liquid at ordinary temperature is preferable in view of workability at the time of compounding and viscosity after compounding.

In a weight ratio between the liquid epoxy resin represented by the general formula (1) and the liquid epoxy resin represented by the general formula (2), 9 parts of the liquid epoxy resin represented by the general formula (2) is used.
If it exceeds 5, the stress characteristics deteriorate, and if it is less than 20, the adhesive strength decreases.

In the present invention, other epoxy resins may be mixed and used. Other epoxy resins when mixed with the above epoxy resin include, for example, aliphatic phenol novolaks, polyglycidyl ethers obtained by the reaction of cresol novolaks with epichlorohydrin, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether and the like. Epoxy, heterocyclic epoxy such as diglycidyl hydantoin, alicyclic epoxy such as vinylcyclohexene dioxide, dicyclopentadiene dioxide, alicyclic diepoxy-adipate, and one or more of these. Can be used together.

Further, a reactive diluent having an epoxy may be mixed for adjusting the viscosity. Examples of the reactive diluent having an epoxy group include, for example, n-butyl glycidyl ether, glycidyl versatate, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, butylphenyl glycidyl ether, and the like. One or more of these can be used in combination.

The phenol curing agent (B) used in the present invention is used as a curing agent for an epoxy resin. The phenol curing agent (B) used in the present invention is preferably a liquid novolak type phenol resin obtained by the reaction of an allylphenol / formaldehyde resin, which is liquid at ordinary temperature from the viewpoint of workability.

In the present invention, other phenol resins may be mixed and used. 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-hydroxyphenol, m-hydroxyphenol, Strong acidity in dilute aqueous solution with monohydric phenols such as p-hydroxyphenol, biphenol, tetramethylbiphenol, ethylidenebisphenol, methylethylidenebis (methylphenol), hexidylhexylidenebisphenol, phenol, cresol, xylenol, etc. in dilute aqueous solution Phenol novolak resin obtained by reacting under the following conditions, monofunctional phenols and polyfunctional such as acrolein and glyoxal Initial condensate under acidity with aldehydes,
Acidic initial condensates of polyhydric phenols such as resorcin, catechol and hydroquinone with formaldehyde, and the like, and these may be used alone or as a mixture.

The phenolic curing agent (B) is preferably used in an amount of 10 to 30 parts by weight based on the epoxy resin (A) from the viewpoint of adhesiveness and low stress. If the blending amount of the phenol curing agent (B) is less than 10 parts by weight with respect to the epoxy resin (A), there is a problem that the adhesive strength is weak and it is not practical.
When the amount exceeds 30 parts by weight, there is a problem that the low stress property is remarkably reduced, and bleed out is easily caused.

The latent curing agent (C) used in the present invention is used as a curing agent for epoxy resins. And a latent curing agent such as dicyandiamide. When a latent curing agent is used, the adhesive strength when heated becomes significantly higher than when cured with a phenol curing agent alone. Also, since the latent curing agent has a smaller equivalent weight than the phenolic curing agent, the viscosity is not so high when used in combination,
In addition, since it is latent, a paste having excellent storage stability can be obtained. The compounding amount of the latent curing agent (C) is preferably 0.5 to 5 parts by weight based on all epoxy resins. 0.5
If the amount is less than 5 parts by weight, the adhesive strength at the time of heating is weak, and if it exceeds 5 parts by weight, the low stress property is reduced.

In the present invention, it is essential to use an imidazole compound (D) in order to enable rapid curing. Generally, it is known that an imidazole compound has a short curing time at a target temperature of 170 to 250 ° C. Examples of the imidazole compound include 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, and 2-phenyl-4. , 5-dihydroxy methyl imidazole, 2-C ₁₁ H ₂₃ - adds a generic imidazole or triazine and isocyanuric acid such as imidazole, to impart storage stability of 2,4-diamino-6-
There are {2-methylimidazole- (1)}-ethyl-S-triazine and its isocyanate adduct, and these can be used in combination with one or more of them. The amount of the imidazole compound is based on all epoxy resins.
It is preferable to use 0.5 to 10 parts by weight. If the amount is less than 0.5 part by weight, the adhesive strength at the time of heating is weak, and if it exceeds 10 parts by weight, the pot life is significantly shortened.

The inorganic filler (E) used in the present invention includes silver powder and silica filler.

Silver powder is used for imparting conductivity,
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. The particle size of the silver powder to be used varies depending on the required viscosity of the paste, but usually the average particle size is preferably 2 to 10 μm, and the maximum particle size is preferably about 50 μm. 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. If the average particle size is less than 1 μm, the viscosity increases, and if the average particle size exceeds 20 μm, bleeding occurs because the resin component flows out during coating or curing, which is not preferable. If the maximum particle size exceeds 50 μm, the outlet of the needle is blocked when applying the paste with a dispenser, so that long-time 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 added in order to impart required properties.

In the resin paste of the present invention, a silane coupling agent, a titanate coupling agent, a pigment, a dye, a defoaming agent, a surfactant, a solvent and the like may be used as long as the properties according to the use are not impaired. Additives can be used. The production method of the present invention includes, for example, premixing the components, kneading using a three-roll mill or the like to obtain a paste, and then defoaming under vacuum.

The semiconductor device manufactured by using the resin paste for semiconductor of the present invention can be quickly cured by oven curing, does not decrease in thermal bond strength, and warps even when a large chip and a copper frame are combined. Therefore, a highly reliable semiconductor device can be obtained. A known method can be used for manufacturing a semiconductor device using a resin paste for a semiconductor.

[0024]

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

Examples 1 to 9 and Comparative Examples 1 to 8 Each component having the composition shown in Tables 1 and 2 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. The evaluation results are shown in Tables 1 and 2.

<Raw materials used> Liquid epoxy resin represented by formula (1) Bisphenol F type epoxy resin (BPFEP): viscosity
5000 mPa · s, epoxy equivalent 170 ・ Liquid epoxy resin represented by general formula (2) Glycidylamine type epoxy resin (GAEP): viscosity 15
00 mPa · s, epoxy equivalent 100 • Phenol curing agent (B): liquid allylated phenol novolak (LPN): viscosity 2000 mPa · s, phenol equivalent 140 • latent curing agent (C): dicyandiamide (DDA) • imidazole compound ( D): 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MH
Z) ・ Inorganic filler (E): silver powder: flake-like silica filler with a particle size of 0.1 to 50 μm and an average particle size of 3 μm: silica filler with an average particle size of 5 μm and a maximum particle size of 20 μm

<Evaluation Method> Viscosity: 25 ° C. using an E-type viscometer (3 ° cone);
The value at 5 rpm was measured and defined as viscosity. Elastic modulus: A paste is applied on a Teflon sheet to a width of 10 mm, a length of about 150 mm, and a thickness of 100 μm, and is cured in an oven at 200 ° C. for 30 minutes.
The modulus of elasticity was calculated from the initial gradient of the stress-strain curve obtained by measuring at a stretching speed of 1 mm / minute at a stretching speed of 00 mm. Adhesive strength: A 2 × 2 mm silicon chip was mounted on a copper frame using a paste and cured in an oven at 200 ° C. for 30 minutes. After curing, the die shear strength under heat at 25 ° C. and 250 ° C. was measured using a mount strength measuring device. Chip warpage: A 6 × 15 × 0.3 mm silicon chip was mounted on a copper frame (200 μm thick) with a conductive resin paste, cured at 200 ° C. for 20 minutes, and then cracks due to chip warpage were observed. 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.

[0028]

[Table 1]

[0029]

[Table 2]

In Examples 1 to 9, excellent pastes having a hot adhesive strength, low stress (low elastic modulus, low warpage) and a long pot life can be obtained. In Comparative Example 1, the amount of glycidylamine type epoxy is low. In many cases, low stress property was deteriorated and chip cracks occurred. In Comparative Example 2, the amount of the glycidylamine type epoxy was small, and the adhesive strength was significantly reduced. In Comparative Example 3, the addition amount of the liquid phenol resin was small, and the adhesive strength was significantly reduced. In Comparative Example 4, a large amount of the liquid phenol resin was added, and chip cracks occurred. In Comparative Example 5, the added amount of the latent curing agent was small, and the adhesive strength was reduced. Comparative Example 6
In Example 2, the amount of the latent curing agent was large, and chip cracks occurred. In Comparative Example 7, the amount of the imidazole compound was small and the adhesive strength was low. In Comparative Example 8, the amount of the imidazole compound added was large, and the pot life was significantly shortened.

[0031]

The resin paste for semiconductors of the present invention can be rapidly cured by oven curing, has a high adhesive strength when heated, and has excellent stress relaxation properties. It is suitable for bonding, and it is possible to prevent a characteristic failure of an IC or the like due to a chip crack or a chip distortion in an IC assembling process, and to obtain a highly reliable semiconductor device.

Claims (2)

[Claims] (A) an epoxy resin wherein the weight ratio of the liquid epoxy resin represented by the general formula (1) to the liquid epoxy resin represented by the general formula (2) is 5:95 to 80:20;
(B) a liquid phenolic resin represented by the general formula (3),
(C) a latent curing agent, (D) an imidazole compound,
(E) Consisting of an inorganic filler, with respect to 100 parts by weight of component (A), 10 to 30 parts by weight of component (B), 0.5 to 5 parts by weight of component (C), and 0.5 to 0.5 parts by weight of component (D). 1 to 10 parts by weight of a resin paste for a semiconductor. Embedded image Embedded image Embedded image 2. A semiconductor device manufactured using the resin paste for a semiconductor according to claim 1.