JP2641349B2 - Insulating 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 an insulating 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 Recent remarkable developments in the electronics industry have evolved into transistors, ICs, LSIs, and VLSIs, and the degree of integration of circuits in these semiconductor devices has rapidly increased, and mass production has become possible. With the spread of semiconductor products using these, improvement in workability and cost reduction in mass production have become important issues. Conventionally, it has been common practice to bond a semiconductor element to a conductor such as a metal frame by an Au-Si eutectic method, and then to seal it with a hermetic seal to obtain a semiconductor product. However, in view of workability and cost during mass production, a resin encapsulation method has been developed and is now generally used. Along with this, as a modification of the Au-Si eutectic method in the mounting process, a method using a mounting material such as a solder material, a conductive resin paste or a resin paste has come to be taken up.

However, the solder method has low reliability,
The disadvantage is that the electrodes of the element are easily contaminated, and the use thereof is limited to power transistors and power IC elements that require high thermal conductivity. On the other hand, the mounting resin is superior in workability and reliability as compared with the soldering method, and the demand thereof is rapidly increasing. Above all, an insulating paste using silica powder is inexpensive because no precious metal is used at all, and the demand in applications that require insulating properties or do not require conductivity is increasing.

More recently, chips have been increasing in size due to the increase in the degree of integration of ICs and the like. On the other hand, since the 42 alloy frame, which has been conventionally used, is expensive, copper is used for cost reduction purposes. Frames have come to be used. Here, when the size of a chip such as an IC becomes larger than about 4 to 5 mm square, when the Au-Si eutectic method is used as a mounting method, the coefficient of thermal expansion of the chip and the copper frame is increased by heating in the assembling process. Chip cracks and warpages due to the difference between the chips cause characteristic defects.

That is, while the coefficient of thermal expansion of silicon or the like, which is the material of the chip, is 3 × 10 ⁻⁶ / ° C.,
This is because the alloy frame has a temperature of 8 × 10 ⁻⁶ / ° C., ^whereas the copper frame has a temperature of 20 × 10 ⁻⁶ / ° C. On the other hand, mounting resin may be used as the mounting method.However, conventional epoxy resin paste is three-dimensionally cured with thermosetting resin, so it has a large elastic modulus and absorbs the distortion between the chip and the copper frame. I didn't do it. On the other hand, in the linear polymer type polyimide resin, the elastic modulus is smaller than that of the epoxy resin, and the warpage of the chip is improved. However, in order to use a polyimide resin as a mounting resin, from the viewpoint of workability, it must be dissolved in a large amount of a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide and the like to reduce the viscosity. No. At this time, the amount of the solvent is 30% by weight or more in the mount resin.
When used for bonding a chip and a metal frame, voids are formed in the cured product as traces of the solvent during curing and heating, resulting in reduced bonding strength, poor electrical and thermal conductivity, and are not preferred from a reliability standpoint. .

When the content of silica filler in the insulating resin paste is reduced to 30% by weight or less for the purpose of lowering the modulus of elasticity, the degree of swaying of the paste becomes too small, causing dripping of the paste and stringing, which is not preferable. Was. Further, the average particle size of the primary particles in the silica filler is 2 to 50.
When ultra-fine silica powder of nm is used together, the thixotropic degree of the paste increases, dripping of the paste, stringing, etc. are greatly improved, and very good coating workability is exhibited. However, in the case of ordinary silica powder that has not been subjected to any surface treatment, the silanol groups on the surface gradually begin to form hydrogen bonds with the resin component in the resin paste, resulting in a decrease in viscosity and thixotropic degree, leading to a reduction in workability. Was.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a high degree of shaking, has excellent workability in dispenser application, has no change in workability with time, and has a chip crack even in a combination of a large chip such as an IC and a copper frame. And IC due to chip warpage
It is intended to provide an insulating paste which does not cause poor characteristics such as the above.

According to the present invention, the silica filler (A), the epoxy resin (B) and the curing agent (C) which are liquid at room temperature are essential components, and the silica filler (A) is contained in the components in an amount of 10 to 30.
10 to 50% by weight in the silica filler, the average particle size of the primary particles is 2 to 50 nm, and 50% or more of the silanol groups on the surface is the organosilicon halide or alcohol represented by the following formula [I]. s and Ri ultrafine silica powder der hydrophobic reacted, silica filler remaining in
50 to 90% by weight do not undergo treatment with the organosilicon compound.
It is an insulating resin paste made of silica filler . Si (R) m (X) n m + n = 4 [I] (R: methyl, ethyl, butyl, octyl X: Cl, Br, OCH ₃ , OH)

The epoxy resin used in the present invention includes, for example, bisphenol A, bisphenol F, polyglycidyl ether obtained by the reaction of phenol novolak with epichlorohydrin, which is liquid at ordinary temperature, vinylcyclohexene dioxide, dicyclopentadiene dioxide, Alicyclic epoxies, such as alicyclic diepoxy-adipate, and also normal, such as n-butyl glycidyl ether, glycidyl versatate, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, dicyclopentadiene diepoxide Some are used as diluents for epoxy resins.

The curing agent is not particularly limited, but a combination of a phenolic resin-based curing agent and a latent amine compound such as dicyandiamide or adipic hydrazide is preferred.
Further, in the present invention, if necessary, additives such as a curing accelerator, a pigment, a dye, and an antifoaming agent can be used.

The silica filler used in the present invention has an average particle size of 1 μm or more and 20 μm or less, and has an average particle size of 2 to 50 nm of fused and / or crushed silica powder and primary particles and 50% or more of silanol groups on the surface and It consists of hydrophobic ultrafine silica powder reacted with an organosilicon halide or an alcohol represented by the formula (I), and the hydrophobic ultrafine silica powder in the total silica filler is 10 to 10.
50% by weight, and 10 to 3% in a composition comprising a silica filler, an epoxy resin liquid at room temperature and a curing agent.
Contains 0% by weight of silica filler.

If the average particle size of the ultrafine powder exceeds 50 nm, the degree of thixotropicity does not increase, and improvement in workability such as dripping of the paste and stringing cannot be expected. When the thickness is less than 2 nm, the bulk density becomes small, so that it is easy to fly in the air, it is difficult to prepare by weighing or the like, and even when the paste is kneaded, it is not preferable because it cannot be uniformly kneaded and tends to remain as a lump. Also, if the ultrafine silica powder used is ordinary silica powder that has not been subjected to any surface treatment, the silanol groups on the surface will gradually begin to form hydrogen bonds with the resin component in the resin paste,
It is not preferable because the viscosity and the thixotropic degree decrease, leading to a decrease in workability.

When the content of the silica filler is less than 10% by weight, the adhesive strength after mounting is insufficient, and when it is more than 30% by weight, a low stress effect cannot be expected. If the amount of the hydrophobic ultrafine silica powder in the silica filler is less than 10% by weight, the degree of thixotropicity of the paste is too small, so that dripping of the paste and stringing occur, resulting in extremely poor workability. If it is more than 50% by weight, the viscosity of the paste becomes too high, which is not practical. The production method of the present invention includes, for example, premixing each component, kneading using a three-roll mill, obtaining a paste, and defoaming under vacuum.

Hereinafter, the present invention will be described in detail with reference to examples. The mixing ratio is shown in parts by weight.

[0015]

【Example】

Examples 1 to 3 Spherical amorphous silica powder having an average particle size of 3 μm (hereinafter referred to as “spherical silica”) and hydrophobic particles having an average particle size of primary particles of about 12 nm and about 70% of silanol groups on the surface treated with dimethyldichlorosilane. Ultrafine silica powder (hereinafter referred to as hydrophobic silica A), diglycidyl ether obtained by the reaction of bisphenol A with epichlorohydrin (liquid at room temperature with epoxy equivalent of 180, hereinafter epoxy resin) and phenol novolak resin (OH equivalent 104, softening point) 110
C), dicyandiamide, and cresyl glycidyl ether as a diluent in the ratios shown in Table 1 and kneaded with a three-roll mill to obtain an insulating resin paste. After degassing the insulating resin paste in a vacuum chamber at 2 mmHg for 30 minutes, each performance was evaluated by the following methods. Table 1 shows the results.

Viscosity The viscosity at 25 ° C. and 2.5 rpm was measured using an E-type viscometer. Fluctuation degree According to the following formula, the ratio of the viscosity at 0.5 rpm and 2.5 rpm was defined as the whisking degree. Paste dripping 5 ml of the paste was put into a syringe with a needle having an inner diameter of 1.0 mm, placed vertically on a test tube stand with the needle down, and 30 minutes later, the weight of the paste dripped on the tip of the needle was measured. Threadability Pins with a diameter of 1mmφ into insulating resin paste are 5m deep
m, and it was lifted at a speed of 30 mm / min to measure the height when the paste was cut. Chip distortion Apply insulating paste on a copper frame, mount a silicon chip (size: 6 × 12 × 0.3 mm) and
Cured in an oven at 0 ° C. for 1 hour. The height from the line connecting the both ends of the chip to the top of the warpage of the chip was measured by a surface roughness meter.

Example 4 A hydrophobic ultrafine silica powder (hereinafter referred to as hydrophobic silica B) having an average primary particle diameter of 12 nm and a surface treated with octyltrimethoxysilane was used as the ultrafine silica powder to be used. An insulating resin paste was prepared and evaluated in the same manner as in Examples 1 to 3. Table 1 shows the results.

Comparative Examples 1 to 5 Insulating resin pastes were obtained in the same manner as in the examples with the mixing ratios shown in Table 1. In Comparative Example 1, the average primary particle size was about 12
In Comparative Example 5, the average particle size of the primary particles was 70 nm, and about 7% of the silanol groups on the surface were used.
Hydrophobic ultrafine silica powder (hereinafter referred to as hydrophobic silica C) treated with 0% dimethyldichlorosilane was used. Table 1 shows the results.

[0019]

[Table 1]

[0020]

The insulating resin paste of the present invention has very little dripping and stringing of the paste at the time of application by a dispenser, has good workability, does not change with time, and has a metal frame made of copper, 42 alloy, etc. It can be used for bonding semiconductor devices such as ICs to substrates and organic substrates such as glass epoxy, and is particularly suitable for bonding large chips on copper frames, and the difference in thermal expansion coefficient between copper frames and silicone chips This is an insulating resin paste for mounting, which is capable of preventing chip cracks and chip defects at the time of heat treatment in an assembling process of ICs or the like due to chip distortion or the like, and has excellent stress relaxation characteristics which has not existed conventionally.

Claims (1)

(57) [Claims] An essential component is (A) a silica filler, (B) an epoxy resin which is liquid at room temperature, and (C) a curing agent. The component contains 10 to 30% by weight of a silica filler (A). 10 to 50% by weight of the filler has an average primary particle diameter of 2 to 50 nm and 50 of silanol groups on the surface.
% Or more and the following formula Ri hydrophobic ultrafine silica powder der reacted with organosilicon halides or alcohols represented by [I], 50 to 90 in the silica filler remaining
% By weight of silica gel not treated with an organosilicon compound
Insulating resin paste, wherein filler der Rukoto. Si (R) m (X) n m + n = 4 [I] (R: methyl, ethyl, butyl, octyl X: Cl, Br, OCH ₃ , OH)