JPH0995651A - Electroconductive resin paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject paste useful for bonding a semiconductor element such as IC and LSI to a metal frame, etc., excellent in curability, especially in adhesiveness, withstanding stress during reflow of solder. SOLUTION: This electroconductive resin paste comprises (A) 60-90wt.% of silver powder, (B) 5-35wt.% of an epoxy resin liquid at a normal temperature, (C) 0.5-8wt.% of a compound containing one or more phenolic hydroxyl groups and alkenyl groups in one molecule (e.g. diallylbisphenol A or diallylbisphenol F), (D) 0.1-5wt.% of a cyclosiloxane of the formula and (E) 100wt.ppm to 50wt. ppm of a platinum-based catalyst [e.g. a complex of platinum and cyclo(vinylmethylsiloxane) as essential components.

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 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.
For this reason, the size of the semiconductor element, which has been conventionally about several mm on the long side, has been dramatically increased to about 10 mm. Further, the lead frame is also made of a copper material, which has good thermal conductivity and is inexpensive, as compared with the conventional 42 alloy, and is becoming the mainstream. On the other hand, the semiconductor product mounting method is a surface mounting method, and due to high-density mounting, the size of the semiconductor product itself is becoming smaller and thinner. In accordance with such trends in semiconductor products, the performance requirements for the constituent materials of semiconductor products are changing, and even for the resin paste for die bonding that bonds the semiconductor element and the metal frame, only the reliability of the bonding that has been conventionally required. However, stress relaxation characteristics that absorb and relax the thermal stress based on the difference in the coefficient of thermal expansion between the large chip and the copper frame,
Furthermore, solder crack resistance characteristics based on surface mounting in thin packages are beginning to be required. Here, regarding the stress relaxation characteristics, the linear thermal expansion coefficient of silicon or the like, which is the material of the semiconductor element, is 3 × 10 ⁻⁶ / ° C., whereas the linear thermal expansion coefficient of the copper frame is 20 × 10 ⁻⁶ / ° C. Since it is large, the copper frame shrinks at a higher rate than the silicon chip in the cooling process after heating and curing the die-bonding resin paste, which may cause chip warpage and chip cracking or peeling of the die-bonding resin paste. This may cause a defect in the characteristics of semiconductor products such as ICs and LSIs.

In order to absorb and relax such thermal stress, the die bonding resin paste needs to have a low elastic modulus. However, the conventional epoxy resin type die bonding resin paste is a thermosetting resin, so that it has a tertiary The original cross-linking resulted in a higher elastic modulus, and the strain due to the difference in the coefficient of thermal expansion between the large chip and the copper frame could not be absorbed. On the other hand, the linear polymer type polyimide resin-based die bonding resin paste has a smaller elastic modulus of the cured product than the epoxy resin-based die bonding resin paste, and the warpage of the chip is improved. However, when a polyimide resin is used as a die-bonding resin paste, it must be dissolved in a large amount of a polar solvent such as N-methyl-2-pyrrolidone or N, N-dimethylformamide to adjust the viscosity in terms of coating workability. I have to. At this time, the amount of the solvent becomes 30% by weight of the resin paste for die bonding, and when it is used for bonding the semiconductor element and the metal frame, voids are generated in the cured product as a trace of the solvent when curing and heating, and the bonding strength is increased. However, it is not preferable in terms of reliability because it causes a decrease in thermal conductivity and conductivity. Reflow crack resistance not only to the semiconductor encapsulant but also to the resin paste for die bonding due to the rapid increase in thermal stress during mounting due to the miniaturization and thinning of the package size for surface mounting or high density mounting. Is being requested. The reflow crack resistance of the die-bonding resin paste has a low elastic modulus near the reflow temperature to absorb and absorb stress during solder reflow, and also has a low water absorption rate in the pretreatment stage of solder reflow, and after water absorption. However, it is necessary to exhibit sufficient bonding strength, particularly strength in the peeling direction in a heated state, but none of them including epoxy resin and polyimide resin paste satisfies these characteristics.

[0004]

SUMMARY OF THE INVENTION According to the present invention, even when a large chip such as an IC and a copper frame are combined, a characteristic defect of the IC such as a chip crack or a warp of the chip does not occur, and a solder reflow crack in a thin package is prevented. It is intended to provide a highly reliable conductive resin paste that does not occur.

[0005]

The present invention provides (A) silver powder,
(B) Epoxy resin liquid at room temperature, (C) compound having at least one phenolic hydroxyl group and alkenyl group in one molecule, (D) cyclosiloxane represented by the formula (1), (E) platinum-based catalyst As an essential component, 60 to 90% by weight of the component (A), 5 to 35% by weight of the component (B), and 0.5 to 8% by weight of the component (C) in the total conductive resin paste,
A conductive resin paste containing 0.1 to 5% by weight of component (D) and 100 to 50 ppm by weight of component (E) in terms of platinum of ppb to 50 ppm by weight.

[0006]

Embedded image

A compound having a low concentration of ionic impurities such as chlorine and sodium, good coating workability, and having at least one phenolic hydroxyl group and alkenyl group in one molecule other than the usual curing reaction of epoxy resin. An alkenyl group and Si of the cyclosiloxane represented by the formula (1)
It has excellent curability because it is also hardened by using the hydrosilylation reaction of H group, and has good adhesive strength. Furthermore, since the adhesive strength is less likely to decrease due to moisture absorption, the conductive resin paste layer peels off due to thermal stress during solder reflow. Is less likely to occur and has excellent reflow crack resistance.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The silver powder used in the present invention preferably has an amount of ionic impurities such as halogen ions and alkali metal ions of 10 ppm or less because the fields of use are electronic and electrical fields. As the shape, flaky, dendritic or spherical shapes can be used alone or in combination. Regarding the particle size, the average particle size is usually 2 to 1
It is preferably 0 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 90% by weight, the viscosity of the resin paste will be too high, which will cause deterioration of coating workability. .

The epoxy resin used in the present invention is limited to a liquid at room temperature, but if it is not 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. Examples of the epoxy resin that is liquid at room temperature include those that are solid at room temperature and those that are stable at room temperature when mixed with an epoxy resin that is liquid at room temperature. Examples of the epoxy resin used in the present invention include aliphatic epoxies such as bisphenol A, bisphenol F, phenol novolac, polyglycidyl ether obtained by reaction of cresol novolacs with epichlorohydrin, butanediol diglycidyl ether, and neopentyl glycol diglycidyl ether. , Cycloaliphatic epoxies such as heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, dicyclopentadiene dioxide, alicyclic diepoxy-adipate, and n-butyl glycidyl ether, versatic acid glycidyl ester , Styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, butyl phenyl glycidyl ether Normal while others are used as diluting agent for epoxy resins, such as equal, they may be used singly or in admixture.

The compound having at least one phenolic hydroxyl group and alkenyl group in one molecule used in the present invention utilizes the reaction of an epoxy group with a phenolic hydroxyl group and the reaction of an Si.H group with an alkenyl group. When the compounds having only the alkenyl group are separately blended, the expected cohesive strength of the cured product and thus the improvement in the adhesive strength are not observed. Further, depending on the compound used, separation occurs during curing and conversely no improvement in adhesive strength is observed, or separation occurs during curing and conversely decreases adhesive strength. Examples of the compound having at least one phenolic hydroxyl group and alkenyl group in one molecule include:
Examples thereof include allylphenol, hydroxystyrene, eugenol, mono- or diallylbisphenol A, mono- or diallylbisphenol F, and diallylbisphenol A or diallylbisphenol F are particularly preferable. The compound having at least one phenolic hydroxyl group and alkenyl group in one molecule is contained in the entire conductive resin paste in an amount of 0.5 to 8% by weight.
If less than 0.5% by weight, the expected effect does not appear, 8% by weight
If the amount is larger than that, unreacted phenolic hydroxyl groups remain in the cured product, which causes reduction in crosslink density, insufficient adhesive strength, deterioration of water absorption property, etc., which is not preferable.

The cyclosiloxane of the formula (1) used in the present invention has m in which R ₁ , R ₂ and R ₃ are methyl groups or phenyl groups.
Is an integer of 2 or more and m + n is 3 to 6. More preferred is a structure represented by the formula (2), m is an integer of 2 or more, and m + n is 4. Examples thereof include tetramethylcyclotetrasiloxane, hexamethylcyclotetrasiloxane, and tetrapentamethylcyclotetrasiloxane. In the case of 1,1,3,3-tetramethyldisiloxane, which is a linear siloxane having a structure different from that of the cyclosiloxane of the formula (1), the boiling point is as low as about 70 ° C., and foaming or volatilization occurs at the time of curing, resulting in a siloxane unit. In the case of a so-called H oil having a ratio of 2 or more, the compatibility with the compound having an alkenyl group, which is a partner of the reaction, becomes poor and there is a drawback that the compound is separated before or during curing. Siloxane does not have these drawbacks. The cyclosiloxane of formula (1) used in the present invention preferably has an ionic impurity such as chlorine or sodium of 50 ppm or less. 0.1 wt% in the total conductive resin paste
If it is less than 5% by weight, the expected performance cannot be obtained, and if it exceeds 5% by weight, unreacted cyclosiloxane remains in the cured product, which is not preferable.

As the platinum-based catalyst used in the present invention, hexachloroplatinic acid generally used in hydrosilylation reaction may be used, but since it is used in the electric and electronic fields, it is corrosive. A complex of platinum with an organic compound or an organic silicone compound is preferable from the viewpoint of reducing the number of ions as much as possible and having catalytic activity. Specifically, there are a complex of platinum and cyclo (vinylmethylsiloxane), a complex of platinum and divinyltetramethyldisiloxane, a complex of platinum and octyl alcohol, and the like, but the complex itself reacts during curing. A complex of platinum and cyclo (vinylmethylsiloxane) and a complex of platinum and divinyltetramethyldisiloxane are more preferable. If the compounding amount of the platinum-based catalyst is less than 100 weight ppb in terms of platinum, the conductive resin paste will not be sufficiently cured or the curing time will be long, and if it exceeds 50 weight ppm, the reaction during curing of the conductive resin paste will be accompanied. The amount of heat generated is too large, and voids are liable to occur in the cured product, resulting in a decrease in adhesive strength and a deterioration in electrical conductivity and thermal conductivity, which is not preferable. In the present invention, if necessary, a latent curing agent, a tertiary amine such as triethylamine, diazabicycloundecene or the like, which is generally known as an accelerator for the reaction between an epoxy group and a phenolic hydroxyl group, triphenylphosphine, tetraphenylphosphine. -Tetraphenyl borate salt, flexibility imparting agent, defoaming agent, coupling agent and the like can also be used. The method for producing the conductive resin paste of the present invention includes, for example, premixing the respective components, kneading them using a three-roll mill, and degassing under vacuum after kneading to obtain a resin paste.

The present invention will be specifically described below with reference to examples. The mixing ratio is shown in parts by weight. Examples 1 to 5 Flake silver powder having a particle size of 1 to 30 μm and an average particle size of 3 μm,
Diglycidyl bisphenol A obtained by the reaction of bisphenol A and epichlorohydrin (epoxy equivalent 180, liquid at room temperature, hereinafter bisA epoxy), cresyl glycidyl ether (epoxy equivalent 185), diallyl bisphenol F, tetramethylcyclotetrasiloxane (hereinafter Silicone compound A), hexamethylcyclotetrasiloxane (hereinafter silicone compound B), cyclo (vinylmethylsiloxane) solution of platinum-cyclo (vinylmethylsiloxane) complex (platinum concentration 1% by weight, platinum catalyst A hereinafter) and coupling agent (Shin-Etsu Chemical Co., Ltd.
KBM-503) and diazabicycloundecene were mixed in a ratio shown in Table 1 and kneaded with a three-roll mill to obtain a conductive resin paste.

After degassing the conductive resin paste in a vacuum chamber at 2 mmHg for 30 minutes, various performances were evaluated by the following methods. Table 1 shows the evaluation results. Gel time: 1 cc of paste was placed on a hot plate at 150 ° C., and agitated with a spatula. The time until the paste showed no fluidity was measured. Viscosity: E type viscometer (3 ° cone) at 25 ° C,
The value at 2.5 rpm was measured and used as the viscosity. String pullability: A pin having a diameter of 1 mmΦ was inserted into a conductive resin paste 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 broken was measured. Volume resistivity: The paste was applied on a slide glass to have a width of 4 mm and a thickness of 30 μm and cured on a hot plate at 150 ° C. for 30 minutes, and then the volume resistivity of the cured product was measured. Adhesive strength: A 5 × 5 mm silicon chip was mounted on a copper frame using a paste and cured at 150 ° C. for 30 minutes. After curing, the die shear strength during heating at 240 ° C was measured using a push-pull gauge. The cured product is at 85 ° C,
The same measurement was performed on a sample that had been subjected to moisture absorption for 72 hours at a relative humidity of 85%. Void: The sample before adhesive strength measurement was observed for voids by the soft X-ray transmission method. Impurities: 2 g of hardened and crushed paste and 40 pure water
The concentration of sodium and chloride ions in the extract obtained by extracting ml for 20 hours at 125 ° C. was measured by ion chromatography.

Example 6 A conductive resin paste was prepared in the same manner as in Examples 1 to 4 except that diallyl bisphenol A was used as the compound having at least one phenolic hydroxyl group and alkenyl group in one molecule. It was produced and evaluated. Example 7 The platinum-based catalyst used was a xylene solution of platinum-divinyltetramethyldisiloxane complex (platinum concentration 3% by weight).
A conductive resin paste was prepared and evaluated in the same manner as in Examples 1 to 4 except that the platinum catalyst B) was used. 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, 1,1,3,3-tetramethyldisiloxane (hereinafter Silicone Compound C) was used instead of Silicone Compound A, and in Comparative Example 6, bisphenol A and 2-hydroxy-1,3 were used.
-Dimethacryloxypropane (hereinafter referred to as a dimethacryl compound) was used. In Comparative Examples 1 and 2, curing was slow and samples could not be prepared, so that evaluation was not possible.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

EFFECT OF THE INVENTION The conductive resin paste of the present invention has good curability and particularly good adhesion, and can withstand stress during solder reflow. Further, it is excellent in workability at the time of dispensing application, has a small amount of ionic impurities, and is most suitable for bonding semiconductor elements such as IC and LSI to a metal frame such as 42 alloy, a ceramic substrate, an organic substrate such as glass epoxy.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09J 183/05 JBF C09J 183/05 JBF H01B 1/22 H01B 1/22 A H01L 21/52 H01L 21 / 52 E

Claims (5)

[Claims] 1. A silver powder, (B) an epoxy resin which is liquid at room temperature, (C) a compound having at least one phenolic hydroxyl group and an alkenyl group in one molecule, and (D) represented by the formula (1). Cyclosiloxane and (E) platinum-based catalyst as essential components, 60 to 90% by weight of (A) component, 5 to 35% by weight of (B), and (C) in the total conductive resin paste.
A conductive resin paste comprising 0.5 to 8 wt% of a component, 0.1 to 5 wt% of a (D) component, and 100 wt ppb to 50 wt ppm of a (E) component in terms of platinum. Embedded image 2. The conductive resin paste according to claim 1, wherein the compound having at least one phenolic hydroxyl group and alkenyl group in one molecule is diallylbisphenol A or diallylbisphenol F. 3. The conductive resin paste according to claim 1, wherein the cyclosiloxane of the formula (1) has the formula (2). Embedded image 4. The platinum-based catalyst is a complex of platinum and cyclo (vinylmethylsiloxane), claim 1,
Alternatively, the conductive resin paste according to claim 3. 5. The platinum-based catalyst is a complex of platinum and divinyltetramethyldisiloxane, 1, 2.
Alternatively, the conductive resin paste according to claim 3.