JPH04342902A - Conductive paste - Google Patents

Abstract

PURPOSE:To provide a conductive paste with excellent anti-humidity characteristic, anti-hydrolysis characteristic, and adhesive characteristic, for example, when it is applied to bonding of semiconductor chip, there are no generation of void, wire breaking malfunction due to corrosion of an aluminum electrode and curved distortion, and applicable to a semiconductor chip in a large scale. CONSTITUTION:(A) an urethane polymer blocked by bisphenol, (B) a polyhydric alcohol compound and (C) conductive powder are made to be essential compositions.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste used for assembling semiconductor devices and adhering various parts, and particularly to a conductive paste that can be used for increasing the size of semiconductor chips and for surface mounting.

0002

2. Description of the Related Art The process of connecting a semiconductor chip such as an IC or LSI to a predetermined portion on a lead base, for example a lead frame, is one of the important processes that affects the long-term reliability of the device. Conventionally, the mainstream connection method has been the Au--Si eutectic method, in which the silicon surface of the semiconductor chip is pressure-bonded to the gold-plated surface of the lead frame. However, due to the recent rise in the price of precious metals, especially gold, resin-sealed semiconductor devices are rapidly shifting from the Au--Si eutectic method to methods using solder, semiconductor paste, and the like.

However, although some methods using solder have been put into practical use, it has been pointed out that the solder and solder balls scatter and adhere to electrodes and the like, causing corrosion and disconnection. On the other hand, the method using conductive paste usually uses epoxy resin mixed with silver powder, and has been partially put into practical use for about 10 years, but compared to the Au-Si eutectic method in terms of reliability. I couldn't get anything that I was satisfied with.

That is, the conventional method using conductive paste has advantages such as superior heat resistance compared to the soldering method, but on the other hand, the resin and curing agent are not suitable for bonding semiconductor elements. Since the Au-Si eutectic method is not used, it tends to generate voids and has poor moisture resistance and hydrolysis resistance, which promotes corrosion of the aluminum electrode and often causes disconnection defects. was inferior compared to Furthermore, as semiconductor chips such as ICs, LSIs, and LEDs become larger, problems arise due to the occurrence of chip cracks and a decrease in adhesive strength.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has excellent moisture resistance, hydrolysis resistance, and adhesive properties, and when applied to bonding semiconductor chips, it prevents the occurrence of voids and The aim is to provide a highly reliable conductive paste that is free from disconnection and warpage due to corrosion of aluminum electrodes, and is compatible with larger semiconductor chips.

[0006]

[Means for Solving the Problems] As a result of intensive research aimed at achieving the above object, the present inventor has discovered that a conductive paste having the composition described below has excellent properties as described above, particularly adhesiveness and moisture resistance. The present invention was completed based on the discovery that

That is, the present invention provides (A) a bisphenol block urethane polymer (B)
This is a conductive paste characterized by containing a polyhydric alcohol compound (C) conductive powder as an essential component.

The present invention will be explained in detail below.

The conductive paste of the present invention comprises (A) a bisphenol block urethane polymer, (B) a polyhydric alcohol compound, and (C) a conductive powder as essential components.

The bisphenol-blocked urethane polymer (A) used in the present invention is a blocked isocyanate prepolymer obtained by blocking the terminal active isocyanate groups of the urethane-forming prepolymer and oligomer with a bisphenol-active hydrogen compound. Typical examples include polyester or polybutadiene having a terminally active isocyanate blocked with a blocking agent such as bisphenol A or bisphenol F, and these may be used alone or in combination of two or more. Can be done. These blocked urethane polymers and oligomers are stable at room temperature, but have the property of dissociating isocyanate groups when heated to 120°C or higher.

The polyhydric alcohol compound (B) used in the present invention includes those having a long-chain alkyl group in consideration of flexibility and pliability, and polyester-based, polybutadiene-based, and silicone-based polyhydric alcohols. is available. Specifically, R-45 manufactured by Idemitsu Petrochemical Co., Ltd.
Examples include polyethylene glycol, polypropylene glycol manufactured by Sanyo Chemical Co., Ltd., alcohol-modified silicone BY series manufactured by Toray Silicone Co., Ltd., and these can be used alone or in a mixture of two or more. The hydroxyl groups of these polyhydric alcohols react with the isocyanate groups dissociated from the urethane polymer and oligomer. The blending ratio of urethane polymer or oligomer and polyhydric alcohol is determined by the ratio of dissociated isocyanate groups (NCO) to hydroxyl groups (OH) of the polyhydric alcohol (NCO/OH).
is preferably in the range of 1.0 to 1.2 equivalents. If this blending ratio is less than 1.0 equivalent or more than 1.2 equivalent, the desired characteristics cannot be obtained, which is not preferable. Further, as a catalyst for promoting this reaction system, dialkyltin dilaurate or the like is generally used.

[0012] Examples of the conductive powder (C) used in the present invention include silver powder, copper powder, nickel powder, and silver powder having a metal layer on the surface, and these may be used alone or in combination of two or more. be able to. These conductive powders are
In both cases, it is desirable that the average particle size is 10 μm or less. If the average particle size exceeds 10 μm, the composition will not become pasty and the coating performance will deteriorate, which is not preferable. The mixing ratio of the conductive powder and the resin component is 30/70 to 1 by weight.
It is desirable that it be 0/90. If the amount of conductive powder is less than 70 parts by weight, satisfactory conductivity cannot be obtained;
If it exceeds 1 part by weight, workability and adhesion will deteriorate, which is undesirable.

[0013] In the conductive paste of the present invention, an organic solvent may be used as necessary to adjust the viscosity. Examples of the solvent include dioxane, hexane, cellosolve acetate, ethyl cellosolve, butyl cellosolve, butyl cellosolve acetate, butyl carbitol acetate, isophorone, etc., and these can be used alone or in combination of two or more.

The method for producing the conductive paste of the present invention can be carried out by thoroughly mixing each raw material component according to a conventional method, and then further kneading the paste using, for example, three rolls, followed by degassing under reduced pressure. . When the conductive paste manufactured in this way is applied to a semiconductor device, for example, it is filled into a syringe and discharged onto a lead base, that is, a lead frame using a dispenser, and after bonding a semiconductor element,
A resin-sealed semiconductor device can be manufactured by performing wire bonding and sealing with a resin sealant.

[0015]

[Function] Compared to epoxy resin-based conductive pastes commonly used for die bonding of semiconductor chips, the conductive paste of the present invention is capable of forming large chips even when heated at 280°C (corresponding to wire bonding of elements). It was found that there was very little warpage and deformation, that the adhesive strength was strong enough to bond semiconductor chips, and that moisture absorption was low. In addition, urethane polymers using bisphenol as a blocking agent appear to have advantages over those using other blocking agents in terms of moisture resistance and the like.

[0016]

EXAMPLES Next, the present invention will be explained by examples, but the present invention is not limited by these examples. In the examples, "parts" means "parts by weight" unless otherwise specified.

Examples 1 to 3 The components shown in Table 1 were kneaded three times using three rolls to produce one-component conductive pastes (A), (B), and (C), respectively.

Comparative Example A commercially available epoxy resin-based solvent-based conductive paste (D
) was obtained. Using the paste, Examples 1 to 3
and conductive pastes (A), (B), (
Using C) and (D), a semiconductor chip and a lead frame were bonded and cured to manufacture a semiconductor device. These semiconductor devices were tested for adhesive strength, chip warpage, hydrolyzable ions, and moisture resistance. The results are shown in Table 1, and the effects of the present invention could be confirmed.

[0019] The adhesion strength is as shown in Table 1 when a 4 x 12 mm silicon chip is placed on a 200 μm thick lead frame (copper type).
The semiconductor devices were bonded under the following semiconductor device bonding conditions, and the shear force was measured using a push-pull gauge at a temperature of 350°C. Chip warpage can be determined by measuring the surface of the chip after curing with a surface roughness meter.
It is indicated by the distance between the center of the chip and the edge. Hydrolyzable ions were cured under semiconductor device adhesion conditions, then ground to 100 mesh, extracted by heating at 180° C. for 2 hours, and the amount of Cl ions was measured by ion chromatography. In the moisture resistance test, the amount of moisture absorbed in water vapor at a temperature of 121° C. and a pressure of 2 atmospheres was measured.

[0020]

[Table 1] *1: 50% of blocked isocyanate prepolymer
Butyl carbitol solution *2: Manufactured by Idemitsu Petrochemical Co., Ltd., terminal hydroxyl group compound.

[0021]

Effects of the Invention As is clear from the above explanation and Table 1, the conductive paste of the present invention has moisture resistance, hydrolysis resistance,
It has excellent adhesive properties, and when applied to bond semiconductor chips, for example, it does not cause voids or breakage or warping due to corrosion of aluminum electrodes, making it a highly reliable conductive paste suitable for larger semiconductor chips.

Claims (1)

[Claims] 1. A conductive paste comprising (A) a bisphenol block urethane polymer, (B) a polyhydric alcohol compound, and (C) a conductive powder as essential components.