JPH10120873A - Insulating resin paste for semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-reliability insulating resin paste free from faults due to cracking or warpage when used in combination of a large chip (e.g. IC) with a copper frame and cracks due to heat cycle in a thin package application by using a specified epoxy resin, a liquid polybutadiene compound, an imidazole compound and a silica filler as the essential components. SOLUTION: This paste essentially consists of an epoxy resin (A) containing at least 30wt.%, based on the entire epoxy resin, reaction product of (a)mol of an epoxy resin represented by the formula (wherein R1 and R2 are each a divalent 1-5C aliphatic group or a residue derived by removing two hydrogen atoms from a 6C or higher aromatic) with (b)mol of bisphenol F (a/b=1-3), a liquid epoxy polybutadiene (B) having a molecular weight of 800-2,000, an imidazole compound (C) and a silica filler (D). The ratio (B)/[(A)+(B)+(C)] should be 0.1-0.3 by weight. The silica filler is desirably one having a mean particle diameter of 1-20μm and a maximum particle diameter of 50μm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an insulating 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 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.
The size of a semiconductor element has been dramatically increased from a long side of about several mm to ten and several mm. In addition, the lead frame is also mainly made of inexpensive copper material with good thermal conductivity from the conventional 42 alloy alloy. On the other hand, the mounting method of the semiconductor product is a surface mounting method and the semiconductor product itself is used for high density mounting. The size is getting smaller and thinner. In accordance with the trend of such semiconductor products, the required performance of constituent materials of the semiconductor products is also changing, and even for the resin bonding paste for bonding the semiconductor element and the metal frame, only the conventionally required bonding reliability is required. Instead, a stress relaxation property for absorbing and relaxing thermal stress based on a difference in thermal expansion coefficient between a large chip and a copper frame, and a heat cycle resistance property in a thin package have been required. Here, the stress relaxation characteristic is such that the linear thermal expansion coefficient of silicon or the like as a material of the semiconductor element is 3 × 10 ⁻⁶ ° C. ⁻¹ , whereas the linear thermal expansion coefficient of the copper frame is 20 × 10 ⁻⁶ ° C. ^−1. Because of this, the copper frame shrinks at a larger rate than the silicon chip during the cooling process after heating and curing the die bonding resin paste, and during the cooling and heat treatment, resulting in chip warpage and chip cracking or die bonding resin paste. Of the semiconductor products such as ICs and LSIs.

[0003] In order to absorb and alleviate such thermal stress, it is necessary to make the die bonding resin paste have a low elastic modulus. However, a conventional epoxy die bonding resin paste is a three-dimensional resin because it is a thermosetting resin. Crosslinking increased the modulus of elasticity, and did not absorb the strain due to the difference in thermal expansion coefficient between the large chip and the copper frame. On the other hand, in the linear polymer type polyimide resin-based die bonding resin paste, the elasticity of the cured product is smaller than that of the epoxy-based die bonding resin paste, and the warpage of the chip is improved. However, when a polyimide resin is used as the resin paste for die bonding, N-
The viscosity must be adjusted by dissolving in a large amount of polar solvent such as methyl-2-pyrrolidone, N, N-dimethylformamide. At this time, the amount of the solvent becomes as much as 30 wt% of the die bonding resin paste. When the solvent is used for bonding the semiconductor element and the metal frame, voids are generated in the cured product after the solvent is removed at the time of curing and heating. This causes a decrease in thermal conductivity, which is not preferable in terms of reliability. In addition, due to the rapid increase in thermal stress during heat cycle processing based on the miniaturization and thinning of the package size for surface mounting or high-density mounting, heat resistance to not only semiconductor encapsulant but also die bonding resin paste Cycle cracking properties have been required. The heat cycle rack resistance of the die bonding resin paste has a low elastic modulus to relax and absorb the thermal stress during cooling of the heat cycle treatment, and also exhibits a high adhesive strength, particularly a sufficient strength in a peeling direction. However, none of these properties, including epoxy and polyimide resin pastes, satisfied these characteristics.

[0004]

According to the present invention, even when a large chip such as an IC is combined with a copper frame, chip cracks and characteristic defects of the IC due to warpage of the chip do not occur, and heat cycle cracks occur in a thin package. The purpose of the present invention is to provide a highly reliable insulating resin paste.

[0005]

According to the present invention, (a) a mole of epoxy resin represented by the following formula (1) and b mole of bisphenol F and b mole of bisphenol F are a / b = 1 to 3 in the total amount of epoxy resin.
An epoxy resin containing at least 30% by weight of a product obtained by the reaction

[0006]

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(Wherein, R ₁ and R _{2 each} represent a divalent aliphatic group having 1 to 5 carbon atoms or a residue obtained by removing two hydrogen atoms from an aromatic group having 6 or more carbon atoms. (B) an epoxy group-containing molecular weight of 800 or more, 200
0 or less liquid polybutadiene compound, (C) imidazole compound, (D) silica filler, as essential components,
(B) / [(A) + (B) + (C)] (weight ratio) is 0.
It is an insulating resin paste for semiconductors, which is 1 to 0.3.

The epoxy resin of the formula (1) used in the present invention has a characteristic of a low elastic modulus. The bivalent aliphatic group represented by R1 and R2 in the formula has not been industrialized if it has 6 or more carbon atoms. R1 and R2 in the present invention are preferably propylene. As an example of the reaction between the epoxy resin of the formula (1) and bisphenol F used in the present invention, the epoxy resin of the formula (1) and the bisphenol F have a molar ratio of 1 to 3, and the epoxy resin and the bisphenol F are mixed at 180 ° C. The reaction is performed under the above conditions. The equivalent ratio is preferably from 1 to 3. If the equivalent ratio exceeds 3, the resin bleed and contamination due to outgas occur during the curing of the paste. If the equivalent ratio is less than 1, the adhesive strength decreases. If necessary, a catalyst may be added to promote this reaction. Examples of the catalyst include a salt of an organic borate and an organic phosphine such as a tetraphenylphosphonium tetraphenylborate salt, and a diaza compound such as 1,8-diazabicyclo (5,4,0) undecene-7.

[0009] Other epoxy resins to be mixed with the reaction product include, for example, bisphenol A, bisphenol F, phenol novolak, polyglycidyl ether, butanediol diglycidyl ether, and neoglycol obtained by reacting cresol novolaks with epichlorohydrin. Aliphatic epoxies such as aliphatic epoxies such as pentyl glycol diglycidyl ether, heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, dicyclopentadiene dioxide, alicyclic diepoxy-adipate, and n -Butyl glycidyl ether, versidic acid glycidyl ester, styrene oside, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether Le are those generally used as diluent in epoxy resins such as butyl phenyl glycidyl ether, can be used in combination with one or more of these. The amount of the reaction product is at least 30% by weight, more preferably at least 50% by weight, based on the total amount of the epoxy resin. If the content is less than 30% by weight, the warpage of the chip after bonding is sharply reduced, and the characteristic of low stress cannot be utilized.

The liquid polybutadiene compound is obtained by reacting a product obtained by reacting the epoxy resin represented by the formula (1) with bisphenol F at a molar ratio of 1 to 3 in the total amount of the epoxy resin.
By using in combination with an epoxy resin containing 0% by weight or more,
A low elastic modulus can be obtained. The liquid polybutadiene compound needs to have an epoxy group. If a liquid polybutadiene having no epoxy group is used, the liquid polybutadiene is separated from the epoxy resin after curing, so that the adhesive strength is reduced and the moisture resistance is deteriorated. When the liquid polybutadiene compound (B) is less than 10% by weight of the weight of [(A) + (B) + (C)], the desired elastic modulus cannot be obtained. It is not practical because it is too high and the adhesive strength is lowered. Further, the molecular weight of the polybutadiene compound is preferably about 800 to 2,000 from the viewpoint of workability, and the number of epoxy groups is preferably two or more per molecule. Number average molecule is Vapor Pressure Osmometer
It is measured by the method. As the polybutadiene compound, E-1000-3.5 and E-1000 available from Nippon Petrochemical Co., Ltd.
-6.5, E-1000-8.0, E-1500-8.
0, E-1800-6.5 and the like.

In the present invention, it is essential to use an imidazole compound to enable in-line cure. 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 isocyanate adduct thereof, and these may be used alone or as a mixture.

The silica filler used in the present invention has an average particle size of 1 to 20 μm and a maximum particle size of 50 μm or less. When the average particle size is 1 μm or less, the viscosity increases, and when the average particle size is 20 μm or more, bleeding occurs because the resin component flows out during application or curing, which is not preferable. If the maximum particle size is 50 μm or more, the outlet of the needle is blocked when applying the paste with a dispenser, and continuous use cannot be performed for a long time. Further, a silica filler other than the present invention may be used in combination in order to impart required properties. If necessary, additives such as an antifoaming agent, a coupling agent, and a surfactant can be used for the insulating resin paste in the present invention. As a method for producing the paste of the present invention, for example, there is a method in which the components are premixed, a paste is obtained using a three-roll mill or the like, and the paste is removed under vacuum.

[0013]

The present invention will be specifically described below with reference to examples. The mixing ratio is shown in parts by weight.

[Production example 1 of reaction product] 100 g of an epoxy resin of the following formula (2) (epoxy equivalent: 181), 25 g of bisphenol F, 1 g of tetraphenylphosphonium tetraphenylborate salt (TPPK) as a catalyst
Was added and reacted at 200 ° C. for 2 hours. This reaction product is referred to as reaction product 1.

[Production Example 2 of reaction product] 100 g of an epoxy resin (epoxy equivalent: 181) of the following formula (2), 45 g of bisphenol F, and 1 g of tetraphenylphosphonium tetraphenylborate salt (TPPK) as a catalyst were used.
Was added and reacted at 200 ° C. for 2 hours. This reaction product is referred to as reaction product 2.

[0016]

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Examples 1 to 5 and Comparative Examples 1 to 5 Each component having the composition shown in Tables 1 and 2 was mixed with a silica filler.
The insulating resin paste was obtained by kneading with three rolls. This insulating resin paste is applied in a vacuum chamber at 2 mmHg for 30 minutes.
After defoaming for a minute, various performances were evaluated by the following methods. The evaluation results are shown in Tables 1 and 2.

[Raw materials used] Reaction product 1 Reaction product 2 Bisphenol F type epoxy: Epoxy equivalent 170 Liquid butadiene compound 1: Molecular weight 1000: average epoxy group 8 per molecule 8 Liquid butadiene compound 2 : Molecular weight 2400, average epoxy group 8 per molecule ・ DDA: dicyandiamide ・ 2PHZ: 2-phenyl-4,5-dihydroxymethylimidazole ・ silica filler: average particle diameter 5 μm and maximum particle diameter 20 μm
Silica filler

[Evaluation method] Viscosity: 25 ° C. using an E-type viscometer (3 ° cone);
The value at 5 rpm was measured and defined as viscosity. Adhesive strength: A 2 × 2 mm silicon chip was mounted on a copper frame using a paste and cured on a hot plate at 200 ° C. for 60 seconds. After curing, use a mount strength measurement device 2
The hot die shear strength at 5 ° C. and 250 ° C. was measured.・ Amount of warpage: 6 × 15 × 0.3 mm silicon chip is mounted on a copper frame (200 μm thick) with an insulating resin paste, and cured at 200 ° C. for 60 seconds. Was measured. Elastic modulus: paste on a Teflon sheet with a width of 10 mm,
Apply to a length of about 150mm and a thickness of 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. Bleed: The periphery of the silver paste of the cured sample having the above adhesive strength was observed under a microscope. Heat cycle crack resistance (T / C resistance): Biphenol type epoxy containing about 80% silica filler /
A package molded using a phenol novolak-based sealing material under the following conditions was heat cycled (30 minutes /-
(65 ° C. → 30 minutes / 150 ° C., 1000 cycles), the number of external cracks was measured by observing the appearance, expressed as a defective rate, and used as an index of heat cycle crack resistance. Package: 80pQFP (20 × 20 × 1.5mmt) Chip size: 10 × 10mm (only aluminum wiring) Lead frame: Copper material Molding: 175 ° C for 2 minutes Post mold cure: 175 ° C for 8 hours ・ Comprehensive evaluation: No problem at all The sample was evaluated as ○ and at least one sample having a problem was evaluated as ×.

[0020]

[Table 1]

[0021]

[Table 2]

In Examples 1 to 5, the characteristics were excellent and the T /
Although a paste having good C properties is obtained, in Comparative Example 1, the amount of the liquid polybutadiene compound used is small, the elastic modulus is high, and the T / C resistance is reduced. In Comparative Example 2, since the amount of the liquid polybutadiene compound used was large and the adhesive strength was low, the T / C resistance was low.
Is reduced. Further, bleeding is not practical. In Comparative Example 3, the content of the reaction product 1 was as small as less than 30% by weight of the total epoxy resin, the elastic modulus and the amount of warpage were large, and the T / C resistance was reduced. In Comparative Examples 4 and 5, the molecular weight of the liquid polybutadiene compound 2 was large and the viscosity of the paste was high, which was not practical.

[0023]

The insulating resin paste of the present invention can be cured in an in-line process, and the cured product has a low elastic modulus of copper,
It can be used for bonding semiconductor elements such as ICs and LSIs to metal frames such as alloys, ceramic substrates, and organic substrates such as glass epoxy. It is particularly suitable for bonding large chips to a copper frame, and can prevent chip cracks and chip distortion based on the difference in the coefficient of thermal expansion between the copper frame and the silicon chip, which can prevent characteristics defects such as ICs and LSIs. This is a highly reliable insulating resin paste for bonding semiconductor elements, which has never been produced before and does not cause cracks during cold heat treatment.

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Claims (1)

[Claims] (A) A product obtained by reacting a mole of an epoxy resin represented by the following formula (1) with b moles of bisphenol F at a / b = 1 to 3 in the total amount of epoxy resin. An epoxy resin containing at least 30% by weight (Wherein, R ₁ and R _{2 each} represent a divalent aliphatic group having 1 to 5 carbon atoms or a residue obtained by removing two hydrogen atoms from an aromatic group having 6 or more carbon atoms, and (B) Molecular weight of 800 or more containing epoxy group, 200
0 or less liquid polybutadiene compound, (C) imidazole compound, (D) silica filler, as essential components, and (B) / [(A) + (B) + (C)]
An insulating resin paste for a semiconductor having a weight ratio of 0.1 to 0.3.