JP2000344864A - Resin paste for semiconductor and semiconductor device sealed therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin paste capable of rapid curing by curing in an oven and exhibiting high hot adhesive strength and giving bonding having excellent stress relaxation and high reliability by including an epoxy resin with a latent curing agent, an imidazole compound, and an inorganic filler. SOLUTION: An epoxy resin (100 pts.wt.) prepared by mixing a liquid epoxy resin having a structure of the formula (wherein n>=0) with an epoxy-containing reactive diluent in a weight ratio of 60/40 to 90/10 is mixed with 0.5-5 pts.wt. latent curing agent such as adipic hydrazide or dicyandiamide, 0.5-10 pts.wt. imidazole compound, and an inorganic filler such as a silver powder or a silica filler. The obtained mixture is kneaded with a three-roll mill, and deaerated in a vacuum to obtain a resin paste for semiconductors. This resin paste is suited for bonding of a large chip such as an IC to a copper frame and can give a semiconductor device made proof against malfunction due to chip crack and warpage and having high reliability.

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 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 the size is larger than ~ 5 mm square, chip cracking or cracking 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 when Au-Si eutectic method is used as the mounting method due to heating during the assembly process of ICs and the like. 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. 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, but the storage stability at room temperature or low temperature, that is, the pot life and the shell life is shortened, and the one-pack type is not practical and Had a 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 elastic modulus of a cured product without lowering the adhesive strength during heating.
The weight ratio of the liquid epoxy resin having the structure of the general formula (1) to the reactive diluent having an epoxy group is 60:40 to 9
0:10, comprising (A) an epoxy resin, (B) a latent curing agent, (C) an imidazole compound, and (D) an inorganic filler. It is a resin paste for a semiconductor containing 5 to 5 parts by weight and 0.5 to 10 parts by weight of the component (C). Further, the present invention is a semiconductor device manufactured using the above-mentioned resin paste for a semiconductor.

[0009]

Embedded image

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin (A) used in the present invention has a weight ratio of a liquid epoxy resin having a structure of the general formula (1) to a reactive diluent having an epoxy group of 60:
It is a liquid epoxy resin having a ratio of 40 to 90:10. 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.

The reactive diluent having an epoxy group to be mixed with the liquid epoxy resin represented by the general formula (1) includes, for example, n-butyl glycidyl ether, glycidyl versatate, styrene oside, ethylhexyl glycidyl ether, Phenylglycidyl ether,
There are 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 60: 4.
It is preferably 0 to 90:10. When the weight ratio of the reactive diluent exceeds 40, 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. As other epoxy resins when mixed with the above epoxy resin, for example, bisphenol A,
Bisphenol F, phenol novolak, aliphatic epoxy such as polyglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether obtained by reaction of cresol novolaks with epichlorohydrin, heterocyclic epoxy such as diglycidyl hydantoin, vinyl There are alicyclic epoxies such as cyclohexene dioxide, dicyclopentadiene dioxide, and alicyclic diepoxy-adipate, which can be used in combination with one or more of these.

The latent curing agent (B) used in the present invention is used as a curing agent for epoxy resins, for example, carboxylic acid dihydrazide such as adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, P-oxybenzoic acid dihydrazide and the like. It is 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 amount of the latent curing agent (B) is preferably 0.5 to 5% by weight based on the total epoxy resin. 0.5
If the amount is less than 5% by weight, the adhesive strength at the time of heating is weak, and if it exceeds 5% by weight, the low stress property is reduced.

In the present invention, it is essential to use an imidazole compound (C) 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, 2-phenyl-4,5-dihydroxy methyl imidazole, 2-C ₁₁ H ₂₃ - adds a generic imidazole or triazine and isocyanuric acid such as imidazole, save 2,4-diamino-6- {2} with stability
-Methylimidazole- (1)}-ethyl-S-triazine and its isocyanate adducts, etc., and can be used in combination with one or more of these. The compounding amount of the imidazole compound is 0.1% with respect to all epoxy resins.
It is preferable to use 5 to 10% by weight. If it is less than 0.5% by weight, the adhesive strength under heat is weak, and if it exceeds 10% by weight, the pot life becomes extremely short.

The inorganic filler (D) 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 1 μm or less, the viscosity increases, and if the average particle size is 20 μm or more, 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 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. As the production method of the present invention, for example, there is a method in which each component is premixed, a paste is obtained using a three-roll or the like, and the paste is defoamed under vacuum.

A semiconductor device manufactured by using the resin paste for a semiconductor of the present invention can be quickly cured by oven curing, has no decrease in adhesive strength when heated, and has warpage even in a combination of a large chip and a copper frame. 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.

[0022]

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 7 and Comparative Examples 1 to 8> Each component having the composition shown in Table 1 and an inorganic filler were blended and kneaded with a three-roll mill to obtain a resin paste. After defoaming the resin paste at 2 mmHg for 30 minutes in a vacuum chamber, various performances were evaluated by the following methods. Table 1 shows the evaluation results.

<Raw materials used> Liquid epoxy resin represented by general formula (1): Viscosity 5000
mPas, epoxy equivalent 190

Bisphenol A type epoxy resin (BP
A): viscosity 9000 mPas, epoxy equivalent 185 bisphenol F type epoxy resin (BPF): viscosity 50
00 mPa · s, epoxy equivalent 170 • Reactive diluent: phenylglycidyl ether • Latent curing agent (B): dicyandiamide (DDA) • Imidazole compound (C): 2-phenyl-4-methyl-5-hydroxymethylimidazole ( 2P4MH
Z)-Inorganic filler (D): Silver powder: Flake-like silica filler with particle size of 0.1 to 50 m and average particle size of 3 m: Silica filler with average particle size of 5 m and maximum particle size of 20 m

<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 30 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 tensile speed 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 30 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 6 × 15 × 0.3 mm silicon chip is mounted on a copper frame (200 μm thick) with a resin paste, cured at 200 ° C. for 20 minutes, and then the warpage of the chip is measured with a surface roughness meter (measuring length 13 mm). did. 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 7, pastes excellent in hot adhesive strength, low stress property (low elastic modulus, low warpage) and pot life were obtained, but Comparative Example 1 used a bisphenol A type epoxy resin. Poor low stress properties, large warpage, and chip cracks. In Comparative Example 2, since the bisphenol F type epoxy resin was used, 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 latent curing agent was small, and the adhesive strength was significantly reduced. In Comparative Example 6, the amount of the latent curing agent was large, the amount of warpage was large, and chip cracks occurred. In Comparative Example 7, the amount of the imidazole compound was small, and the adhesive strength was significantly reduced. In Comparative Example 8, the amount of the imidazole compound was large, and the pot life was significantly shortened.

[0030]

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 weight ratio of a liquid epoxy resin having a structure of the general formula (1) to a reactive diluent having an epoxy group is 6:
(A) an epoxy resin having a ratio of 0:40 to 90:10,
(B) a latent curing agent, (C) an imidazole compound, and (D) an inorganic filler, wherein component (B) is 0.5 to 5 parts by weight and component (C) is 100 parts by weight of component (A). Is 0.5 to 10 parts by weight. Embedded image 2. A semiconductor device manufactured using the resin paste for a semiconductor according to claim 1.