JP3214685B2 - Conductive resin paste - Google Patents

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 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 An in-line curing method in which a die bonder, a wire bonder, and the like are arranged on the same line has been adopted for the purpose of improving productivity in the bonding of semiconductor elements in a semiconductor manufacturing process, that is, a so-called die bonding 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 a conductive resin paste by a batch method.
For example, in the case of the oven curing method, 150 to 200
The curing was performed at 60 ° C. for 60 to 90 minutes. In the case of the in-line curing method, curing for 15 to 90 seconds is required. Furthermore, when in-line curing of semiconductor products with large chip size and copper frame, low-temperature curing is also used to minimize the amount of chip warpage and prevent oxidation of the frame based on the difference in thermal expansion coefficient between the chip and the copper frame. And a shorter curing time is required.

In the case of a conventionally used polyimide conductive paste, it is difficult to cure in a short time of 90 seconds or less because a high boiling solvent such as N-methyl-2-pyrrolidone and dimethylformamide is used. In order to perform curing in a short time, the curing temperature must be 250 ° C. or higher, so that a large amount of voids are generated during curing, and the properties of semiconductor products such as adhesive strength, electrical conductivity and thermal conductivity are deteriorated. Was connected to. On the other hand, in the case of the currently mainstream epoxy-based conductive paste, curing can be performed in about 60 seconds by using, for example, an amine-based curing agent, but 15 to 30 seconds is possible.
It does not deal with ultra-short curing such as seconds.

[0004]

SUMMARY OF THE INVENTION The present invention provides a highly reliable conductive resin paste which can be cured under a curing condition of 200 ° C. or less for 30 seconds or less and which has little ionic impurities such as sodium and chlorine. Things.

[0005]

The present invention provides (A) a silver powder,
(B) a liquid epoxy resin at room temperature, (C) the following formula (1)
And (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 entire 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). The coating workability is good, and by using a biphenol derivative represented by the formula (1) and an imidazole derivative represented by the formula (2) in combination, curing at 200 ° C. or less for 30 seconds or less becomes possible, It is excellent in adhesiveness at high temperature, stress relaxation property, low water absorption and has a sufficient pot life.

[0006]

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

[0007]

Embedded image (R ₁ ＣＨCH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl,
R ₂ , R ₃ ＨH, CH ₃ , or C ₂ H ₅ )

Since the silver powder used in the present invention is used in the field of electronics and electronics, the amount of ionic impurities such as halogen ions and alkali metal ions is desirably 10 ppm or less. Flakes, dendrites or spheres can be used alone or in combination. Further, with respect to the particle size, usually, the average particle size is preferably 2 to 10 μm and the maximum particle size is preferably about 50 μm, and a mixture of relatively fine silver powder and coarse silver powder may be used. When the amount of silver powder in the entire conductive resin paste is less than 60% by weight, the electric conductivity of the cured product decreases, and when the amount exceeds 85% by weight, the viscosity of the resin paste becomes too high, which causes a decrease in 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 lowers the adhesive strength and thermal conductivity of the cured product. The epoxy resin which is liquid at ordinary temperature includes, for example, a resin which is solid at ordinary temperature and shows a stable liquid at ordinary temperature by being mixed with the epoxy resin which is liquid at ordinary temperature. Examples of the epoxy resin used in the present invention include polyglycidyl ether obtained by reacting bisphenol A, bisphenol F, phenol novolak resin, cresol-type novolak resin, etc. with epichlorohydrin, 1,6-dihydroxynaphthalenediglycidyl ether, butanediol diglycidyl. Ethers, aliphatic epoxies such as neopentyl glycol diglycidyl ether, heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, dicyclopentadiene dioxide,
Alicyclic epoxy such as alicyclic diepoxy-adipate, further n-butyl glycidyl ether, glycidyl versatate, styrene oxide,
Ethyl hexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, butyl phenyl glycidyl ether and the like are used as diluents for ordinary epoxy resins, 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. I have. Further, the biphenyl skeleton has a relatively small internal rotation energy, so that 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 preferably 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,
Preferably, it is 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 to be practical.

The imidazole derivative of the formula (2) of the present invention is used in combination with the biphenol derivative of the formula (1) because it has poor curing properties and does not have rapid curing properties as an in-line curing material. In addition, when ordinary imidazoles other than the formula (2) are used, the reactivity becomes good,
On the other hand, the storage stability is poor and the utility is poor. By using the adduct of the imidazoles and vinyltriazine of the present invention, it has become possible to achieve both reactivity and storage stability.
The imidazole derivative represented by the formula (2) is contained in the entire conductive resin paste in an amount of 0.5 to 3.0% by weight. 0.5
If the amount is less than 30% by weight, sufficient curability is not exhibited, and if the amount is more than 3.0% by weight, the adhesive strength at a high temperature, which is a disadvantage of a cured product using imidazoles, is unpreferably reduced. R _{1 in} formula (2) is CH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl, R ₂ , R ₃ ＨH, CH ₃ , or C ₂ H ₅ ; ₁ is CH ₃ and R ₂ and R ₃ are H. That is,
It is an adduct of 2-methylimidazole and vinyltriazine.

Further, if necessary, it may be used in combination with another curing agent such as a latent amine curing agent. As a combination, tertiary amines, other imidazoles, triphenylphosphine, tetraphenylphosphine / tetraphenylborate, 1,8-diazabicycloundecene and the like are generally used for curing epoxy resins and phenolic curing agents. Accelerators. In the present invention, a flexibility-imparting agent, an antifoaming agent, a coupling agent, and the like may be used as necessary. The production method of the present invention includes, for example, preliminarily mixing the components, kneading them using a three-roll mill, kneading and then defoaming under vacuum to obtain a resin paste.

Hereinafter, the present invention will be described in detail with reference to examples. The mixing ratio is shown in parts by weight. Examples 1 to 5 Diglycidyl bisphenol A (epoxy equivalent: 180, liquid at ordinary temperature, hereinafter referred to as bis-A epoxy) obtained by reacting flake silver powder having a particle diameter of 1 to 30 μm and an average particle diameter of 3 μm with bisphenol A and epichlorohydrin; Cresyl glycidyl ether (epoxy equivalent 185), 3,
3 ', 5,5'-Tetramethylbiphenol (hereinafter, biphenol A, manufactured by Honshu Chemical Industry Co., Ltd.), 2-methylimidazoleazine (addition product of 2-methylimidazole and vinyltriazine) (Shikoku Chemical Industry Co., Ltd.)・ 2MZ-
A, hereinafter 2MZ-A), dicyandiamide, and 1,8-diazabicycloundecene were blended in the ratio shown in Table 1, and 3
The conductive resin paste was obtained by kneading with this roll. This conductive resin paste is applied in a vacuum chamber at 2 mmHg for 3 hours.
After defoaming for 0 minutes, various performances were evaluated by the following methods.

Gel time: 1 cc of conductive resin paste
Was placed on a hot plate at 170 ° C. and stirred with a spatula to measure the time until the conductive resin paste showed no fluidity. 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. Also, 25
Measure the viscosity after standing at ℃ for 3 days. Stringing property: 1mmφ in diameter into conductive resin paste
Was inserted to a depth of 5 mm, the pin was pulled up at a speed of 300 mm / min, and the height when the paste was cut was measured. Volume resistivity: A conductive resin paste having a width of 4 mm and a thickness of 30 μm was applied on a slide glass, 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.
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 was cured in an oven at 150 ° C. for 30 minutes.
Water absorption treatment was performed at 5 ° C, 85% for 72 hours, and the water absorption was calculated from the weight change before and after the treatment. 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 30 seconds, and the chip warpage was measured with 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 200 ° C. hot plate for 30 seconds. After curing, the die shear strength at 240 ° C. was measured using a push-pull gauge. Impurities: 2g of cured and ground conductive resin paste
Then, 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 (hereinafter, biphenol B, manufactured by Honshu Chemical Industry Co., Ltd.) was used as a curing agent. And evaluated. Table 1 shows the evaluation results. Comparative Examples 1 to 6 Conductive resin pastes were produced in exactly the same manner as in the examples with the mixing ratios shown in Table 2. In Comparative Example 5, a phenol novolak resin (hydroxyl equivalent: 104, softening point: 85 ° C.) was used as a curing agent. In Comparative Example 6, 2-methylimidazole (Shikoku Chemical Industry Co., Ltd.) was used as a curing agent.
2MZ, hereinafter 2MZ). Table 2 shows the evaluation results.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

The conductive resin paste of the present invention has good workability at the time of dispensing application and has a small amount of ionic impurities such as sodium and chlorine, a metal frame of copper, 42 alloy, a ceramic substrate, a glass epoxy, etc. For bonding semiconductor elements such as ICs and LSIs to organic substrates. In particular, since the curability is good, it can be cured at 200 ° C. or less for 30 seconds or less, and is a highly reliable conductive resin paste for bonding semiconductor elements, which has not existed conventionally.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01B1 / 22 H01B1 / 22 A (56) References JP-A-53-59799 (JP, A) JP-A-53-114844 ( JP, A) JP-A-60-84283 (JP, A) JP-A-62-145601 (JP, A) JP-A-4-339883 (JP, A) JP-A-5-163331 (JP, A) JP-A-5-175253 (JP, A) JP-A-6-84974 (JP, A) JP-A-6-116514 (JP, A) JP-A-6-184282 (JP, A) JP-A-6-322350 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 63/00-63/10 C08K 3/08 C08G 59/56 C08G 59/62 C09J 163/00-163/10 H01B 1 / twenty two

Claims (2)

(57) [Claims] An essential component is (A) silver powder, (B) an epoxy resin 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). A silver powder (A) of 60 to 85% by weight, a biphenol derivative (C) represented by the formula (1) of 0.5 to 5% by weight in the entire conductive resin paste, A conductive resin paste containing the imidazole derivative (D) represented by the formula (2) in an amount of 0.5 to 3.0% by weight. Embedded image (R is H or CH ₃ and may be the same or different.) (R ₁ ＣＨCH ₃ , C ₂ H ₅ , C ₁₁ H ₂₃ , or phenyl,
R ₂ , R ₃ ＨH, 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.