JPH08176409A - Conductive resin paste - Google Patents

Abstract

PURPOSE: To obtain a high-reliability conductive resin paste which does not cause defects in characteristics of integrated circuits, etc., nor solder reflow crack in thin packages by compounding a silver powder, an epoxy resin liq. at a normal temp., and a specific reaction product of a phenol compd. with a silicone compd. CONSTITUTION: This contains, as the essential components, 60-85wt.% silver powder, an epoxy resin liq. at a normal temp., and 1-20wt.% reaction product obtd. by the hydrosililation of a compd. having at least one alkenyl group and at least two phenolic hydroxyl groups with a silicone compd. of the formula (wherein each R1 is independently CH3 or OCH3 provided at least two R1 's are CH3 ).

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. Also, the lead frame is mainly made of copper material, which has good thermal conductivity and is inexpensive, from the conventional 42 alloy. On the other hand, the mounting method of semiconductor products is the surface mounting method and the high density mounting.
Despite the increase in the size of semiconductor elements, the package sealing size is becoming smaller. With such trends in semiconductor products, the performance requirements for the constituent materials of semiconductor products have also changed, and the reliability of bonding that has been conventionally required for die-bonding resin paste for bonding semiconductor elements and metal frames In addition to the characteristics, stress relaxation characteristics that absorb and relax thermal stress based on the difference in coefficient of thermal expansion between large chips and copper frames, and solder crack resistance characteristics based on surface mounting in thin packages have been demanded. .

Regarding the stress relaxation characteristic, the linear thermal expansion coefficient of silicon, which is a material for semiconductor elements, is 3 × 10 ^-6 / ° C, whereas the linear thermal expansion coefficient of a copper frame is 20 × 10 ^-6 / ° C. Since it is one digit larger, the copper frame shrinks at a rate larger than that of the silicon chip in the cooling process after heating and curing the die bonding resin paste.
The warp of the chip, which in turn causes chip cracks or peeling of the resin paste for die bonding, causes the IC,
There is a possibility that it may be a cause of defective characteristics of semiconductor products such as LSI. In order to absorb and relax such thermal stress, it is necessary to make the die-bonding resin paste have a low elastic modulus, but the conventional epoxy-based die-bonding resin paste is a thermosetting resin and is three-dimensionally crosslinked and elastic. The rate was high, and strain could not be absorbed due to the difference in thermal expansion coefficient between the large chip and the copper frame. On the other hand, the linear polymer type polyimide die-bonding resin paste has a smaller elastic modulus of the cured product than the epoxy die-bonding resin paste, and the warpage of the chip is improved.
However, when a polyimide resin is used as a resin paste for die bonding, it must be dissolved in a large amount of a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide or the like to adjust the viscosity in terms of coating workability. I won't. The amount of solvent at this time is as much as 30% by weight of the die-bonding resin paste, and when it is used for bonding a semiconductor element and a metal frame, voids are generated in the cured product after the solvent escapes at the time of curing and heating, and the bonding occurs. It causes deterioration of strength, thermal conductivity and conductivity, and is not preferable in terms of reliability.

Further, due to a rapid increase in thermal stress during mounting based on the miniaturization and thinning of the package size for surface mounting or high density mounting, not only the semiconductor sealing material but also the resin paste for die bonding is used. Also, reflow crack resistance is required. The reflow crack resistance of the die-bonding resin paste has a low elastic modulus near the reflow temperature in order to absorb and absorb stress during solder reflow, and has a low water absorption rate at the pretreatment stage of solder reflow Even after that, it is necessary to show sufficient bonding strength, particularly strength in the peeling direction in a heated state, but none of these, including epoxy-based and polyimide-based resin pastes, satisfied these characteristics.

[0005]

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.

[0006]

The present invention provides (A) silver powder,
(B) an epoxy resin which is liquid at room temperature, (C) a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule, and a silicone compound represented by the formula (1) are hydrosilylated. A conductive resin paste containing the obtained reaction product as an essential component,
Moreover, the component (A) is added to the total conductive resin paste at 60 to 85.
A conductive resin paste containing 1% to 20% by weight of the component (C),

[0007]

Embedded image

By using the curing agent of component (C),
Compared to phenol novolac resin, which is a curing agent for epoxy resins that has been used conventionally, the cross-linking density of the cured product is significantly reduced and the elastic modulus is low, so even in the combination of large chips such as IC and LSI and copper frames. It is excellent in stress relaxation characteristics that sufficiently absorb strain due to the difference in coefficient of thermal expansion. Further, by introducing an extremely flexible siloxane bond into the main chain in the component (C), the cured product itself can be made flexible without significantly reducing the cohesive force of the cured product, so that heat resistance is sacrificed. Since the adhesive force in the peeling direction, which is a drawback of epoxy resin paste, which has been a problem from the past, can be significantly improved, peeling of the conductive resin paste layer due to thermal stress during solder reflow is less likely to occur. It has excellent reflow crack resistance.

Since the silver powder used in the present invention is used in electronic and electrical fields, it is desirable that the amount of ionic impurities such as halogen ions and alkali metal ions be 10 ppm or less. As for 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 resin paste is less than 60% by weight, the electrical conductivity of the cured product will be reduced, and if it exceeds 85% by weight, the viscosity of the resin paste will be too high and the coating workability will be reduced. Absent. The epoxy resin used in the present invention is limited to a liquid at room temperature, but a solvent is required for kneading with silver powder unless it is liquid at room temperature. The solvent is not preferable because it causes bubbles and reduces the adhesive strength and thermal conductivity of the cured product. Here, the epoxy resin that is liquid at room temperature is
For example, it includes those that are solid at room temperature but those that are stable at room temperature when mixed with an epoxy resin that is liquid at room temperature.

The epoxy resin used in the present invention includes bisphenol A, bisphenol F, phenol novolac resin, polyglycidyl ether obtained by the reaction of cresol novolac resins with epichlorohydrin,
Aliphatic epoxies such as butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, heterocyclic epoxies such as diglycidyl hydantoin, vinyl cyclohexene dioxide, dicyclopentadiene dioxide, fats such as alicyclic diepoxy adipate Used as a diluent for ordinary epoxy resins such as cyclic epoxy, n-butyl glycidyl ether, versatic acid glycidyl ester, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, and butylphenyl glycidyl ether There are things that are
These may be used alone or in combination.

The curing agent used in the present invention is obtained by reacting a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule with a silicone compound represented by the formula (1) by a hydrosilylation reaction. It is a reaction product of 1 to 2 in the total conductive resin paste.
Contains 0% by weight. In the case of phenol novolac resin, which is a hardener that has been used in the past, the cross-link density of the cured product is high, so the elastic modulus is high and the stress relaxation property is reduced, and the adhesive force especially in the peeling direction is small When used in combination with the copper frame,
It cannot withstand the stress during solder reflow, causing peeling of the silver paste layer and eventually package cracking.
When the number of alkenyl groups in the compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule is 1 or more, 2: 1 to 1.5: 1 is preferable. When the molar ratio exceeds 2: 1, a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule remains as an unreacted component,
If it is less than 1.5: 1, the silicone compound of formula (1) remains as an unreacted component, which is not preferable.

A reaction product obtained by reacting a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in the molecule of the present invention with a silicone compound represented by the formula (1) by a hydrosilylation reaction. Is
1 to 20% by weight is contained in the total conductive resin paste, but if it is less than 1% by weight, the required low stress and high adhesion cannot be expected, and if it exceeds 20% by weight, the amount of curing agent becomes too large to cure. After that, excessive phenolic hydroxyl groups remain in an unreacted state so that the water absorption rate of the cured product increases, or even after curing, a sufficient cross-linked structure cannot be obtained and the adhesive strength during heating becomes extremely low, which is not preferable. . A compound obtained by reacting a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule with a silicone compound represented by the formula (1) by a hydrosilylation reaction may be used alone or in combination. It may be used together with other phenol novolac resins. 1
Examples of the compound having at least one alkenyl group and at least two phenolic hydroxyl groups in the molecule include diallylbisphenol A, tris (O-allylhydroxyphenyl) methane, and di (O-allylhydroxyphenyl) hydroxyphenylmethane. Yes, and preferred is diallyl bisphenol A. R ₁ in the formula (1) is CH ₃ or OCH ₃ , and at least two are CH ₃
And preferred is a disiloxane in which all R ₁ are CH ₃ .

If desired, they may be used in combination with other curing agents such as latent amine curing agents. Generally, epoxy resins such as tertiary amines, imidazoles, triphenylphosphine, tetraphenylphosphine and tetraphenylborate are used. It is also possible to add a compound known as a curing accelerator of a phenol-based curing agent. In the present invention, a flexibility imparting agent, a defoaming agent, a coupling agent and the like can be used if necessary. The production method of the present invention includes, for example, pre-mixing the respective components, followed by kneading using a three-roll mill,
After kneading, defoaming is performed 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. A reaction product obtained by reacting a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule used in Examples and Comparative Examples with a silicone compound represented by the formula (1) by a hydrosilylation reaction. A method for manufacturing a product will be shown as a manufacturing example. Production Example 1 1, 1, 3, 3 was placed in a 4-neck flask with an internal volume of 1 liter equipped with a reflux condenser, a thermometer, and a stirrer.
-67 g of tetramethyldisiloxane, diallyl bisphenol A (manufactured by Mitsui Toatsu Chemicals, Inc., hereinafter BPA-C)
A) 300 g, hexachloroplatinum (IV) acid hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) in isopropyl alcohol (5% by weight) 0.1 g, and azeotropic dehydration in advance using a Linstark trap Toluene (500 g) was added, and the mixture was stirred and refluxed for 4 hours. Toluene was distilled off from the obtained content under reduced pressure to obtain a silicone compound A. Production Example 2 Using the same apparatus as in Production Example 1, 70 g of 1,1,3,3-tetramethyldisiloxane and BPA-CA250 were used.
g, hexachloroplatinate (IV) acid hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.1 g of isopropyl alcohol (5% by weight), and 500 g of toluene azeotropically dehydrated in advance using a Linstark trap Was charged and the reaction was carried out with stirring and refluxing for 4 hours. Toluene was distilled off from the obtained contents under reduced pressure to obtain a silicone compound B. Production Example 3 Using the same apparatus as in Production Example 1, 70 g of 1,1,3,3-tetramethyldisiloxane, 140 g of O-allylphenol, hexachloroplatinum (IV) acid hexahydrate (Wako Pure Chemical Industries ( Co., Ltd.) isopropyl alcohol solution (5
0.1% by weight) and 500 g of toluene which had been azeotropically dehydrated in advance using a Linstark trap, and stirred and refluxed for 4 hours. Toluene was distilled off from the obtained contents under reduced pressure to obtain a silicone compound C.

Examples 1 to 5 Flake silver powder having a particle size of 1 to 30 μm and an average particle size of 3 μm, bisphenol F epoxy (epoxy equivalent 170, liquid at room temperature, hereinafter bis F epoxy), cresyl glycidyl ether (epoxy equivalent 185) , Silicone compound A
(Hydroxyl equivalent 189), silicone compound B (hydroxyl equivalent 197), bisphenol F (hydroxyl equivalent 100),
Phenol novolac resin (hydroxyl group equivalent 104), dicyandiamide, and 1,8-diazabicycloundecene were mixed in the proportions shown in Table 1 and kneaded with three rolls to obtain a conductive resin paste.

The conductive resin paste was defoamed in a vacuum chamber at 2 mmHg for 30 minutes, and various performances were evaluated by the following methods. Viscosity: 25 using E-type viscometer (3 ° cone)
Measured at ℃ and 2.5 rpm. Volume resistivity: 4m width paste on slide glass
m, thickness 30 μm, and apply in an oven at 200 ° C for 6
After curing for 0 minutes, the volume resistivity of the cured product is measured. Elastic Modulus: Paste 10m wide on Teflon sheet
m, length about 150 mm, thickness 100 μm, 200
After curing for 60 minutes in an oven at ℃, measured with a tensile tester at a test length of 100 mm and a pulling speed of 1 mm / min,
Elastic modulus was calculated from the initial gradient of the obtained stress-strain curve. Adhesive Strength: A 9 × 9 mm silicon chip was mounted on a copper frame using a paste and cured at 200 ° C. for 60 seconds on a hot plate. After curing, measure the die shear strength during heating at 240 ° C using the mount strength measuring device.

Warp of chip: A silicon chip of 6 × 15 × 0.3 mm was mounted on a copper frame (thickness of 200 μm) with a paste and cured at 200 ° C. for 60 seconds, and then the warp of the chip was measured by a surface roughness meter (measurement). Measured with a length of 13 mm). Package crack resistance: A package molded under the following conditions using a biphenol-type epoxy / phenol novolac resin-based encapsulating material containing about 78% silica filler is treated with water at 85 ° C, 85% for 120 hours, and then IR
Reflow (240 ℃, 10 seconds) treatment,
The number of internal cracks was measured by observing the cross section and used as an index of the package crack resistance. Package: 80 pQFP (14 × 20 × 2.0 mm thickness) Chip size: 9 × 9 mm (only aluminum wiring) Lead frame: Copper material molding: 175 ° C., 2 minutes Post mold cure: 175 ° C., 8 hours Comparative Examples 1 to 1 7 A conductive resin paste was prepared with the compounding ratios shown in Table 2 in exactly the same manner as in the examples. Table 2 shows the evaluation results.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

EFFECT OF THE INVENTION The conductive resin paste of the present invention has a low elastic modulus of a cured product, and a metal frame such as copper or 42 alloy, a ceramic substrate, an IC or LS on an organic substrate such as glass epoxy.
It can be used for bonding semiconductor elements such as I. Especially suitable for bonding large chips to a copper frame, which is based on the difference in the coefficient of thermal expansion between the copper frame and the silicon chip.
It is a conductive resin paste for bonding highly reliable semiconductor elements, which can prevent characteristic defects such as I, does not cause cracks during soldering even when used in a thin package, and has never been used before.

Claims (2)

[Claims] 1. A compound of formula (1) with (A) silver powder, (B) an epoxy resin which is liquid at room temperature, (C) a compound having at least one alkenyl group and at least two phenolic hydroxyl groups in one molecule. A conductive resin paste containing a reaction product obtained by a hydrosilylation reaction of the silicone compound shown as an essential component, wherein 60 to 85% by weight of the component (A) in the total conductive resin paste, (C) 1 to 1
A conductive resin paste containing 20% by weight. Embedded image 2. The reaction molar ratio of diallyl bisphenol A and the silicone compound represented by formula (1) is from 2: 1 to
The reaction product (C) obtained at 1.5: 1.
The conductive resin paste described.