JPH04222887A - Insulating resin paste - Google Patents

Abstract

PURPOSE:To obtain the subject paste having excellent applicability and stress- relaxation property in the application with a dispenser and useful for the bonding of a semiconductor element such as IC and LSI to a metallic frame by using a specific silica filler, a specific epoxy resin and a curing agent as essential components. CONSTITUTION:The objective paste can be produced by preliminarily mixing (A) 10-30wt.% of a silica filler containing 10-50wt.% of ultrafine silica powder having an average primary particle size of 2-50nm, (B) an epoxy resin exhibiting liquid nature at ordinary temperature (e.g. bisphenol A cresylglycidyl ether), (C) a curing agent (e.g. phenolic resin hardener combined with dicyandiamide) and, as necessary, (D) other additives (e.g. curing agent, cure accelerator and pigment), kneading the mixture with a three-roll mill and defoaming in vacuum.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating paste for bonding semiconductor elements such as ICs and LSIs to metal frames and the like.

0002

[Background Art] With the recent remarkable development of the electronics industry, transistors, ICs, LSIs, and VLSIs have evolved.The degree of circuit integration in these semiconductor devices has rapidly increased, and mass production has become possible. With the spread of semiconductor products using these semiconductors, improving workability and reducing costs in mass production have become important issues. Conventionally, it has been common to bond a semiconductor element to a conductor such as a metal frame by the Au-Si eutectic method, and then seal it with a hermetic seal to produce a semiconductor product. However, from the viewpoint of workability and cost during mass production, a resin sealing method was developed and is now common. Along with this, as an improvement to the Au-Si eutectic method in the mounting process, methods using mounting resins such as solder materials, conductive resin pastes, and insulating pastes have been taken up.

However, the reliability of the soldering method is low;
The drawback is that it tends to contaminate the electrodes of the device, and its use is limited to power transistors and power IC devices that require high thermal conductivity. On the other hand, mounting resins are superior in terms of workability and reliability compared to soldering methods, and the demand for them is rapidly increasing. Among these, insulating pastes using silica powder are inexpensive because they do not use any noble metals, and demand is increasing, especially for applications that do not require electrical conductivity.

[0004]Furthermore, recently, chips have become larger due to the higher integration density of ICs, etc. On the other hand, since the conventionally used 42 alloy frame, which is the lead frame, is expensive, copper frames are being used for cost reduction purposes. has come to be used. Here, if the size of the chip such as IC is larger than about 4 to 5 mm square, the mounting method is A.
When the u-Si eutectic method is used, cracks and warpage of the chip occur due to the difference in thermal expansion coefficient between the chip and the copper frame due to heating during the assembly process, resulting in poor characteristics. .

In other words, while the coefficient of thermal expansion of silicon, etc., which is the chip material, is 3 × 10-6/°C, this is 42
This is because, while it is 8 x 10-6/°C for an alloy frame, it is as large as 20 x 10-6/°C for a copper frame. On the other hand, it is possible to use mounting resin as a mounting method, but since conventional epoxy resin paste is three-dimensionally cured with thermosetting resin, it has a high elastic modulus and absorbs the strain between the chip and the copper frame. I wasn't able to do it. On the other hand, linear polymer type polyimide resins have a lower elastic modulus than epoxy resins, and chip warpage is improved. However, in order to use polyimide resin as a mounting resin, N-methyl-2-pyrrolidone, N-methyl-2-pyrrolidone,
It must be dissolved in a large amount of a polar solvent such as N,N-dimethyl formalde to reduce its viscosity. The amount of solvent at this time is over 30% by weight in the mount resin, and when used to bond the chip and metal frame, voids are generated in the cured product as traces of solvent leakage during curing heating, and the adhesive This is unfavorable from a reliability standpoint since it causes a decrease in strength and poor electrical and thermal conduction.

Furthermore, in an insulating resin paste, if the silica filler content is lower than 30% by weight for the purpose of lowering the elastic modulus, the thixotropy of the paste becomes too small, which is undesirable because paste sag, stringiness, etc. occur. Ta.

[0007]

[Problems to be Solved by the Invention] The present invention has high thixotropy and is excellent in workability during dispenser coating, and even when a large chip such as an IC and a copper frame is combined, there will be no characteristic defects in the IC etc. due to chip cracks or warping of the chip. This provides an insulating paste that does not cause electrical damage.

[0008]

[Means for Solving the Problems] The present invention includes a silica filler (A), an epoxy resin (B) that is liquid at room temperature, and a curing agent (C) as essential components, and contains silica filler (
A) containing 10 to 30% by weight, 1 in the silica filler
An insulating resin paste consisting of 0 to 50% by weight of ultrafine silica powder with an average primary particle diameter of 2 to 50 nm.It has good workability, has a small elastic modulus of the cured product, and has low thermal expansion between the chip and the copper frame. It absorbs the strain caused by the difference in rate and is excellent in stress relaxation.

The epoxy resin used in the present invention is limited to one that is liquid at room temperature, but if it is not liquid at room temperature, a solvent will be required for kneading with the silica filler. Solvents cause bubble generation and reduce the adhesive strength of the cured product.

Epoxy resins used in the present invention include, for example, bisphenol A, bisphenol F, diglycidyl ether obtained by the reaction of phenol novolak and epichlorohydrin, which is liquid at room temperature, vinylcyclohexene dioxide, dicyclopentadiene dioxide, Alicyclic epoxies such as alicyclic diepoxy dipate, as well as conventional epoxies such as n-butyl glycidyl ether, versatic acid glycidyl ester, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, and dicyclopentadiene diepoxide. Some are used as diluents for epoxy resins.

Although the curing agent is not particularly limited, it is preferable to use a phenolic resin curing agent in combination with a latent amine compound such as dicyandiamide or adipic acid hydrazide. Furthermore, in the present invention, additives such as curing accelerators, pigments, dyes, antifoaming agents, etc. can also be used as necessary.

The silica filler used in the present invention includes fused and/or ground silica powder with an average particle size of 1 μm or more and 20 μm or less, and primary particles with an average particle size of 2 to 50 nm.
The amount of ultrafine silica powder in the total silica filler is 10 to 50% by weight. Furthermore, 10 to 30% by weight of silica filler is contained in the composition consisting of silica filler, an epoxy resin that is liquid at room temperature, and a curing agent.

[0013] If the average particle diameter of the ultrafine powder exceeds 50 nm, the thixotropy will not increase, and improvements in workability such as paste sagging and stringiness cannot be expected. If it is less than 2 nm, the bulk density becomes small, which makes it easy to fly in the air, making it difficult to weigh and prepare, and even when kneading the paste, it cannot be uniformly kneaded and tends to remain as a lump, which is not preferable.

If the silica filler content is less than 10% by weight, the adhesive strength after mounting will be insufficient, and if it is more than 30% by weight, a stress-lowering effect cannot be expected. If the amount of ultrafine silica powder in the silica filler is less than 10% by weight, the thixotropy of the paste is too small, causing the paste to sag or become stringy, resulting in very poor workability. Moreover, if it exceeds 50% by weight, the viscosity of the paste increases too much and is not practical. The manufacturing method of the present invention includes, for example, premixing each component, kneading it using three rolls to obtain a paste, and defoaming under vacuum.

[0015] The present invention will be specifically explained below with reference to Examples. The blending ratio is shown in parts by weight.

[Example] Examples 1 to 4 Spherical amorphous silica powder with an average particle size of 3 μm (hereinafter referred to as spherical silica), ultrafine silica powder with an average primary particle size of 12 nm (hereinafter referred to as silica A), bisphenol A, and epichlorohydrin. Diglydyl ether (epoxy equivalent: 180, liquid at room temperature, hereinafter referred to as epoxy resin) obtained by the reaction of phenol novolak resin (OH equivalent: 104,
(softening point: 110° C.), dicyandiamide, and cresyl glycidyl ether as a diluent in the proportions shown in Table 1, and kneaded with a three-roll roll to obtain an insulating resin paste. After degassing this insulating resin paste in a vacuum chamber at 2 mmHg for 30 minutes, each performance was evaluated by the following methods. The results are shown in Table 1.

Viscosity Using an E-type viscometer, the value at 25° C. and 25 rpm was taken as the viscosity. Thixometry The ratio of the viscosity at 0.5 rpm and 25 rpm was defined as the thixotropy according to the following equation. 5 ml of the paste was placed in a syringe equipped with a needle having an inner diameter of 1.0 mm, and placed vertically on a test tube stand with the needle facing down. After 30 minutes, the weight of the paste dripping at the tip of the needle was measured. 1m diameter into stringy insulating paste
Sink the mφ pin to a depth of 5mm, and then add it to a depth of 300mm.
The height when the paste was cut was measured at a speed of /min. Silicon chips (
Size: 6 x 12 x 0.3 mm) mounted and 200
Cure in oven for 1 hour. The height from the line connecting both ends of the chip to the top of the warp of the chip perpendicularly was measured using a surface roughness meter. Comparative Examples 1 to 6 Insulating pastes were obtained in the same manner as in Example 1 using the blending ratios shown in Table 1. Comparative Example 5 used ultrafine silica powder (hereinafter referred to as fine silica B) with an average primary particle diameter of 1 nm, and Comparative Example 6 used ultrafine silica powder (hereinafter referred to as fine silica C) with an average primary particle diameter of 70 nm. there was. The results are shown in Table 1.

[0017]

[Table 1]

[0018]

Effects of the Invention The insulating resin paste of the present invention has excellent workability with very little paste dripping or stringing when applied with a dispenser, and can be applied to metal frames such as copper and 42 alloy, ceramic substrates, and organic substrates such as glass epoxy. It can be used to bond semiconductor elements such as ICs to
Particularly suitable for bonding large chips onto copper frames,
It can prevent characteristic defects in ICs due to chip cracks and chip distortions during heat treatment during the assembly process of ICs due to the difference in thermal expansion coefficient between the copper frame and silicone chip, and has excellent stress relaxation properties that were not found in the past. This is an insulating resin paste for mounting.

Claims (1)

[Claims] Claim 1: The essential components are (A) silica filler, (B) an epoxy resin that is liquid at room temperature, and (C) a curing agent, which contains 10 to 30% by weight of silica filler (A), and contains silica filler (A) in an amount of 10-30% by weight. An insulating resin paste characterized in that 10 to 50% by weight of the filler is ultrafine silica powder having an average primary particle diameter of 2 to 50 nm.