JPH08176408A - Conductive resin paste - Google Patents

Abstract

PURPOSE: To obtain a high-reliability conductive resin paste which can be cured under such mild conditions as at 200 deg.C or lower for 30sec or lower and contains very low amts. of sodium, chlorine. etc., by compounding a silver powder, an epoxy resin liq. at normal temp., a specific biphenol deriv., and a specific imidazole deriv. as the essential components. CONSTITUTION: This paste contains, as the essential components, 60-85wt.% silver powder, an epoxy resin liq. at a normal temp., 0.5-5wt.% biphenol deriv. represented by formula I (wherein each R is independently H or CH3 ), and 0.5-3.0wt.% imidazole deriv. represented by formula II (wherein R1 is CH3 , C2 H5 , C11 H23 , or phenyl; and R2 and R3 are each H, CH3 , oe C2 H5 ).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive resin paste for adhering semiconductor elements such as IC and LSI to a metal frame or the like.

[0002]

2. Description of the Related Art In-line curing method in which a die bonder, a wire bonder, etc. are arranged on the same line is adopted for the purpose of improving the productivity in the so-called die-bonding process, which is the bonding of semiconductor elements in the semiconductor manufacturing process. is there. In the in-line curing method, the time required for curing is significantly limited as compared with the conventional method of curing the conductive resin paste by the batch method.
For example, in the case of the oven curing method, 150 to 200
The curing was carried out at 60 ° C. for 60 to 90 minutes, but in the case of the in-line curing method, curing in 15 to 90 seconds is required. Furthermore, due to the large chip size and in-line curing of semiconductor products that use a copper frame, low-temperature curing is used to minimize chip warpage and prevent frame oxidation due to the difference in thermal expansion coefficient between the chip and copper frame. In addition, the curing time is required to be shorter.

In the case of the conventional polyimide-based conductive paste, it is difficult to cure in a short time of 90 seconds or less because a high boiling point solvent such as N-methyl-2-pyrrolidone or dimethylformamide is used. However, in order to carry out curing in a short time, the curing temperature must be 250 ° C or higher, so a large amount of voids are generated during curing, resulting in deterioration of adhesive strength, deterioration of electrical conductivity and thermal conductivity, and deterioration of semiconductor product characteristics. Was connected to. On the other hand, in the case of the epoxy-based conductive paste, which is the mainstream at present, it is possible to cure in about 60 seconds by using, for example, an amine-based curing agent, but 15 to 30.
No cure for ultra-short time such as seconds has been made.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a highly reliable conductive resin paste which can be cured even at a curing condition of 200 ° C. or lower for 30 seconds or less and has a small amount of ionic impurities such as sodium and chlorine. It is a thing.

[0005]

The present invention provides (A) silver powder,
(B) Epoxy resin that is liquid at room temperature, (C) The following formula (1)
A biphenol derivative represented by the formula (D), a conductive resin paste containing an imidazole derivative represented by the following formula (2) as an essential component, and 60 to 85% by weight of silver powder (A) in the total conductive resin paste. A conductive resin paste containing 0.5 to 5% by weight of the biphenol derivative (C) represented by the formula (1) and 0.5 to 3.0% by weight of the imidazole derivative (D) represented by the formula (2). By using the biphenol derivative represented by the formula (1) and the imidazole derivative represented by the formula (2) together, it is possible to cure at 200 ° C. or lower for 30 seconds or less, It has excellent adhesiveness at high temperatures, stress relaxation characteristics, low water absorption, and a sufficient pot life.

[0006]

Embedded image (R is H or CH ₃ and may be the same or different)

[0007]

[Chemical 4] (R ₁ = CH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl,
R ₂ , R ₃ = H, CH ₃ , or C ₂ H ₅ )

The silver powder used in the present invention is preferably used in an electronic and electrical field because the amount of ionic impurities such as halogen ions and alkali metal ions is 10 ppm or less. As the shape, flaky, dendritic or spherical shapes can be used alone or in combination. Regarding the particle size, it is usually preferable that the average particle size is 2 to 10 μm and the maximum particle size is about 50 μm, and relatively fine silver powder and coarse silver powder may be mixed and used. If the amount of silver powder in the total conductive resin paste is less than 60% by weight, the electrical conductivity of the cured product will decrease, and if it exceeds 85% by weight, the viscosity of the resin paste will be too high, which will cause deterioration of coating workability. It is not preferable.

The epoxy resin used in the present invention is liquid at room temperature, and unless it is liquid at room temperature, a solvent is required for kneading with silver powder. The solvent is not preferable because it causes bubbles and reduces the adhesive strength and thermal conductivity of the cured product. The epoxy resin which is liquid at room temperature includes, for example, those which are solid at room temperature and which are stable at room temperature when mixed with the epoxy resin which is liquid at room temperature. Examples of the epoxy resin used in the present invention include polyglycidyl ether obtained by the reaction of bisphenol A, bisphenol F, phenol novolac resin, cresol type novolac resin and epichlorohydrin, 1,6-dihydroxynaphthalene diglycidyl ether, butanediol diglycidyl. Ethers, aliphatic epoxies such as neopentyl glycol diglycidyl ether, heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, dicyclopentadiene dioxide,
Alicyclic epoxies such as alicyclic diepoxy-adipate, n-butyl glycidyl ether, versatic acid glycidyl ester, styrene oxide,
Some are used as diluents for ordinary epoxy resins such as ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, butyl phenyl glycidyl ether, and these may be used alone or in combination.

The biphenol derivative of the formula (1) used in the present invention has a high melting point and does not dissolve in ordinary epoxy resins at room temperature. There is. Further, since the biphenyl skeleton has a relatively small internal rotation energy, the obtained cured product is tough, and the free volume of the cured product is small, so that low water absorption can be achieved. R in the formula (1) is H or CH ₃
, And may be the same or different, but preferred is that all R are CH ₃ or H. The biphenol derivative of the formula (1) is 0.5 to 5% by weight in the total conductive resin paste,
It is preferably contained in an amount of 1 to 3% by weight. If it is less than 0.5% by weight, the desired toughness and low water absorption are not exhibited, and if it exceeds 5% by weight, the viscosity of the conductive resin paste becomes too high, which is not practical.

The imidazole derivative of the formula (2) of the present invention is used in combination because the biphenol derivative of the formula (1) alone has poor curability and does not have fast curability as an in-line curable material. In addition, when the usual imidazoles other than the formula (2) are used, the reactivity becomes good,
On the other hand, it is poor in storability and poor in practicality. By using the adduct of the imidazoles of the present invention and vinyltriazine, it becomes possible to achieve both reactivity and storage stability.
The imidazole derivative represented by the formula (2) is contained in the total conductive resin paste in an amount of 0.5 to 3.0% by weight. 0.5
If it is less than wt%, sufficient curability will not be exhibited, and if it exceeds 3.0 wt%, the adhesive strength at high temperature, which is a drawback of a cured product using an imidazole, decreases, which is not preferable. R _{1 in} formula (2) is CH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl, R ₂ , R ₃ ═H, CH ₃ , or C ₂ H ₅ , with preference for R 1. ₁ is CH ₃ and R ₂ and R ₃ are H. That is,
It is an adduct of 2-methylimidazole and vinyltriazine.

If desired, it may be used in combination with another curing agent such as a latent amine curing agent. Examples of the concomitant use include curing of generally epoxy resins such as tertiary amines, other imidazoles, triphenylphosphine, tetraphenylphosphine / tetraphenylborate, and 1,8-diazabicycloundecene with a phenolic curing agent. Examples include accelerators. In the present invention, a flexibility-imparting agent, a defoaming agent, a coupling agent, etc. may be used if necessary. The production method of the present invention includes, for example, premixing the respective components, kneading them using a three-roll mill, and defoaming under vacuum to obtain a resin paste.

The present invention will be specifically described below with reference to examples. The blending ratio is shown in parts by weight. Examples 1 to 5 Diglycidyl bisphenol A (epoxy equivalent 180, liquid at room temperature, hereinafter bis A epoxy) obtained by reaction of flaky silver powder having a particle size of 1 to 30 μm and an average particle size of 3 μm with bisphenol A and epichlorohydrin, Cresyl glycidyl ether (epoxy equivalent 185), 3,
3 ', 5,5'-Tetramethylbiphenol (manufactured by Honshu Chemical Industry Co., Ltd., hereinafter biphenol A), 2-methylimidazole azine (addition product of 2-methylimidazole and vinyltriazine) (Shikoku Chemicals Co., Ltd.)・ Production 2MZ-
A, hereafter 2MZ-A), dicyandiamide, and 1,8-diazabicycloundecene were mixed in the proportions shown in Table 1, and 3
It kneaded with this roll and obtained the conductive resin paste. This conductive resin paste is 3 mm at 2 mmHg in a vacuum chamber.
After defoaming for 0 minutes, various performances were evaluated by the following methods.

Gel time: 1 cc of conductive resin paste
Place on a hot plate at 170 ° C, stir with a spatula, and measure the time until the conductive resin paste shows no fluidity. Viscosity: E type viscometer (3 ° cone), 25
The viscosity was measured by measuring the value at 2.5 ° C. at 2.5 ° C. Also, 25
Measure the viscosity after standing for 3 days at ℃. String pullability: Diameter of 1mmφ into conductive resin paste
Insert the pin up to a depth of 5 mm, pull up the pin at a speed of 300 mm / min, and measure the height when the paste is broken. Volume resistivity: A conductive resin paste having a width of 4 mm and a thickness of 30 μm was applied on a slide glass and cured on a hot plate at 200 ° C. for 30 seconds, and then the volume resistivity of the cured product was measured. Elastic modulus: A conductive resin paste is applied on a Teflon sheet so as to have a size of 10 × 150 × 0.1 mm, and then 15
After curing in an oven at 0 ° C. for 30 minutes, a load-displacement curve was measured with a tensile tester at a test length of 100 mm and a test speed of 1 mm / min, and the elastic modulus was calculated from the initial gradient.

Water absorption: A conductive resin paste was applied on a Teflon sheet so as to have a size of 50 × 50 × 0.1 mm and cured in an oven at 150 ° C. for 30 minutes, and then 8
Water absorption treatment was performed at 5 ° C for 85 hours at 85%, and the water absorption rate was calculated from the weight change before and after the treatment. Chip warpage: A 6x15x0.3mm silicon chip was mounted on a copper frame (thickness: 200 µm) with a conductive resin paste and cured at 200 ° C for 30 seconds, and then the chip warpage was measured using a surface roughness meter (measurement length). 13 mm). Adhesive strength: A 5 × 5 mm silicon chip was mounted on a copper frame using a conductive resin paste and cured on a hot plate at 200 ° C. for 30 seconds. After curing, measure the die shear strength when heated at 240 ° C using a push-pull gauge. Impurity: 2g of hardened and crushed conductive resin paste
And 40 ml of pure water was extracted at 125 ° C. for 20 hours, and the sodium and chloride ion concentrations of the obtained extract were measured by ion chromatography.

Example 6 A conductive resin paste was prepared in the same manner as in Examples 1 to 5 except that p, p'-biphenol (manufactured by Honshu Chemical Industry Co., Ltd., hereinafter biphenol B) was used as a curing agent. And evaluated. Table 1 shows the evaluation results. Comparative Examples 1 to 6 Conductive resin pastes were prepared with the compounding ratios shown in Table 2 in exactly the same manner as in the examples. In Comparative Example 5, a phenol novolac resin (hydroxyl group equivalent 104, softening point 85 ° C.) was used as a curing agent. In Comparative Example 6, 2-methylimidazole (Shikoku Chemicals Co., Ltd.) was used as the curing agent.
Manufactured by 2MZ, hereinafter 2MZ) was used. Table 2 shows the evaluation results.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

EFFECTS OF THE INVENTION The conductive resin paste of the present invention has good workability at the time of dispensing and has less ionic impurities such as sodium and chlorine, copper, metal frame such as 42 alloy, ceramic substrate, glass epoxy, etc. It can be used for adhering semiconductor elements such as IC and LSI to the organic substrate. In particular, since it has good curability, it can be cured at 200 ° C. or lower for 30 seconds or less, and it is a highly reliable conductive resin paste for bonding semiconductor elements, which has never existed before.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C09J 9/02

Claims (2)

[Claims] 1. An essential component comprising (A) silver powder, (B) an epoxy resin which is liquid at room temperature, (C) a biphenol derivative represented by the following formula (1), and (D) an imidazole derivative represented by the following formula (2). Which is a conductive resin paste containing 60 to 85% by weight of silver powder (A) and 0.5 to 5% by weight of the biphenol derivative (C) represented by the formula (1) in the entire conductive resin paste, A conductive resin paste containing 0.5 to 3.0% by weight of the imidazole derivative (D) represented by the formula (2). Embedded image (R is H or CH ₃ and may be the same or different.) (R ₁ = CH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl,
R ₂ , R ₃ = H, CH ₃ , or C ₂ H ₅ ) 2. The conductive resin paste according to claim 1, wherein the imidazole derivative is an adduct of 2-methylimidazole and vinyltriazine.