JP2000290468A - Die attach paste for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin paste not causing characteristic inferiority due to chip crack and warp even in a combination of a large-sized chip such as an IC and a copper frame, and capable of rapidly being cured and imparting a void-free cured product by lowering the elasticity of a cured product without lowering the adhesive strength while hot. SOLUTION: This die attach paste comprises a liquid epoxy resin in a liquid state at room temperature, a polycarbodiimide resin, a latently curing agent, an imidazole compound and an inorganic filler. The liquid epoxy resin of 100 pts.wt. is formulated with the polycarbodiimide resin of 1-30 pts.wt.

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, an organic substrate 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. In addition, conventional mounting resins are cured in an oven at 150-200 ° C for 1-2
It was necessary to heat for hours. 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. To achieve fast curing, there is a method of adding a large amount of a curing accelerator, but the shelf life at room temperature or low temperature, that is, the pot life and shell life is shortened, and the one-pack type is not practical and Had a disadvantage that the adhesive strength was low.

[0008]

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.

[0009]

The present invention provides (A) a liquid epoxy resin which is liquid at room temperature, (B) a polycarbodiimide resin, (C) a latent curing agent, (D) an imidazole compound, and (E) an inorganic filler. As an essential component, and component (A) 1
Component (B) is 1 to 30 parts by weight, and component (E) is component (A), (B), (C), and (D) in total of 1 part by weight based on 00 parts by weight.
The die attach paste is 10 to 400 parts by weight with respect to 00 parts by weight.

The liquid epoxy resin (A) used in the present invention is preferably a liquid in view of workability at the time of compounding and viscosity after compounding, but is not particularly limited. Examples of those generally used include aliphatic epoxies such as diglycidyl ethers of bisphenol compounds such as bisphenol A, bisphenol F, bisphenol E and biphenol, butanediol diglycidyl ether, and neopentyl glycol diglycidyl ether, and diglycidyl hydantoin. Alicyclic epoxies such as heterocyclic epoxies, vinylcyclohexene dioxide, dicyclopentadiene dioxide, and alicyclic diepoxy-adipate, and can be used in combination with one or more of these. .

The polycarbodiimide resin (B) used in the present invention is a resin obtained by a decarboxylation reaction of isocyanate. By blending with an epoxy resin, the brittleness of the cured product can be improved, and the heat resistance and adhesiveness can be significantly improved. The addition amount of the polycarbodiimide resin is preferably 1 to 30 parts by weight based on 100 parts by weight of the component (A). If the amount is less than 1 part by weight, the effect of improving the adhesiveness is poor, and if it exceeds 30 parts by weight, the curing speed is lowered or the viscosity becomes too high, and the workability is undesirably lowered.

The latent curing agent (C) used in the present invention is used as a curing agent for epoxy resins. And latent curing agents. 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 compounding amount of the latent curing agent (C) is preferably 0.5 to 5% by weight based on the entire epoxy resin. 0.5% by weight
If it is less than 5%, the adhesive strength upon 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 (E) 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, 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- {2-methylimidazole - (1 )｝ -Ethyl-S-triazine and its isocyanate adducts.
It can be used in combination with one or more types. The amount of the imidazole compound is 0.5 to 10 with respect to all epoxy resins.
It is preferred to use% by weight. If it is less than 0.5% by weight, the adhesive strength at the time of heating is weak, and if it exceeds 10% by weight, the pot life is significantly shortened.

The inorganic filler (E) used in the present invention includes silver powder and silica filler. In the die attach paste of the present invention, 1 to 100 parts by weight of the resin component is used.
0 to 400 parts by weight is blended. If the amount is less than 10 parts by weight, conductivity is not exhibited or the effect of lowering the coefficient of linear expansion is poor. If the amount exceeds 400 parts by weight, the viscosity of the paste increases, and the workability decreases, which is not preferable.

The 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.

The resin paste of 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 the components, kneading using a three-roll mill or the like to obtain a paste, and then deconcentrating under vacuum.

[0019]

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, Comparative Examples 1 to 8> 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. This resin paste was defoamed in a vacuum chamber at 2 mmHg for 30 minutes to obtain a die attach paste for semiconductors. Various performances of the obtained paste were evaluated by the following methods. The evaluation results are shown in Tables 1 and 2.

<Raw materials used> Polycarbodiimide resin (B1); manufactured by Nisshinbo Co., Ltd .:
Carbodilite 10M-SP • Polycarbodiimide resin (B2); manufactured by Nisshinbo Co., Ltd .:
Carbodilite V-05

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 ・ 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 particle diameter of 0.1 to 50 m and average particle diameter of 3 m: Silica filler with average particle diameter of 5 m and maximum particle diameter 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 10 width on Teflon sheet
about 150 mm length and 100 μm thickness, 200
After curing in an oven at 30 ° C. 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 pulling rate of 1 mm / min. 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. Amount of warpage: A silicon chip of 6 × 15 × 0.3 mm was mounted on a copper frame (200 μm thick) with the obtained paste, and cured at 200 ° C. for 20 minutes. ). 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.

[0024]

[Table 1]

[0025]

[Table 2]

In Examples 1 to 7, an excellent paste having a hot adhesive strength, low stress (low elastic modulus, low warpage) and a long pot life can be obtained. In Comparative Example 1, a bisphenol A type epoxy resin is used. As a result, the low stress property is poor, the amount of warpage increases, and chip cracks occur. 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 compounding amount of the compound B1 was large, the viscosity was increased, and the workability was significantly reduced. Comparative Example 4 is bisphenol A
The warpage is significantly increased only with the type epoxy. Comparative Example 5
Has a large amount of silver filler, a high viscosity and a remarkable decrease in adhesive strength. In Comparative Example 6, the compounding amount of the compound B2 was large and the amount of warpage was small, but the viscosity was significantly increased. In Comparative Example 7, the amount of the silica filler was small, and the adhesive strength when heated was significantly reduced. In Comparative Example 8, since the compounding amount of the compound B1 was large and the compounding amount of imidazole was large, the viscosity was high and the pot life was significantly shortened.

[0027]

The die attach 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 with ICs, and can prevent the characteristic failure of ICs and the like due to chip cracks and chip distortion in the IC assembly process.

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Claims (1)

[Claims] 1. An essential component comprising (A) a liquid epoxy resin which is liquid at room temperature, (B) a polycarbodiimide resin, (C) a latent curing agent, (D) an imidazole compound, and (E) an inorganic filler. A) 100 parts by weight of component (B) is 1 to 30 parts by weight, component (E) is component (A),
(B), (C), 1 (D) for a total of 100 parts by weight
A die attach paste for a semiconductor, wherein the amount is 0 to 400 parts by weight.