JPH0451406A - Electric conductive paste - Google Patents

Abstract

PURPOSE:To obtain excellent adhesive property, to eliminate generation of voids and to enhance productivity as well as long term reliability because of low temperature high speed cure by adopting modified resin composed of poly-p- hydroxystyrene resin and low viscous liquid epoxy resin, an imidazole catalyst and electric conductive powder as essential components. CONSTITUTION:Modified resin composed of poly-p-hydroxystyrene resin and low viscous liquid epoxy resin, an imidazole catalyst and electric conductive powder are the essential components of this electric conductive paste. These components are blended and kneaded homogeneously by means of triple rolls and the like for production. Several seconds to scores of hours after this conduc tive paste is applied to a specified position by means of a dispenser, screen printing, pin transfer method and the like, various kinds of semiconductive pellets are placed thereon and the paste is heated for curing on a heater block for scores of seconds to several minutes at comparatively low degrees such as 100-200 deg.C to be used. Several minutes of curing at 150-200 deg.C in an oven is also employed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a conductive paste that has excellent adhesive properties, can be bonded at high speed, and contributes to improved productivity and cost reduction. In particular, the conductive paste of the present invention is suitable for die bonding ink for semiconductor devices.

(Prior art) IC and LS are placed on a predetermined portion of a thin metal plate (lead frame).
The process of connecting semiconductor elements such as I is one of the important processes that affects the long-term reliability of the element. Conventionally, the mainstream connection method has been the Au-3i eutectic method, in which the silicon surface of the element is heat-pressed to the gold-plated surface of the lead frame. However, in recent years, in resin-sealed semiconductor devices, there has been a rapid shift from the Au-3i eutectic method to methods using solder, conductive paste, etc.

(Problem to be solved by the invention) However, although some methods using solder have been put into practical use, it has been pointed out that solder and solder balls scatter and adhere to electrodes, etc., causing corrosion and disconnection. has been done. On the other hand, in the method using conductive base 1~, an epoxy resin mixed with silver powder is usually used, and it has been put into practical use for about 10 years, or the eutectic resin of A11-s* is It was not possible to obtain satisfactory results compared to alloys. When using a conductive paste, it has the advantage of being heat resistant (prevents wrinkles, etc.) compared to the soldering method, but on the other hand, it is prone to void generation, poor moisture resistance, hydrolysis resistance, and corrosion of aluminum electrodes. This often causes defects in the @ line, and the reliability of the device was inferior to that of the AIJ-8i eutectic method.
In addition, when using conductive paste, soldering method or Au-
Compared to the 5R eutectic method, the bonding time is longer,
It was a batch method in which the licking was removed from the heat curing production line and put into the oven, which resulted in poor productivity.

The present invention has been made to eliminate the above-mentioned drawbacks, and has excellent adhesion and no void generation even when curing on a bed block in an assembly in-line, high productivity due to low temperature and high speed curing, and CD The purpose is to provide a highly reliable conductive paste for a long period of time, which contributes to the above-mentioned problems and also maintains general characteristics.

[Structure of the Invention] (Means for Solving the Problem) As a result of intensive research aimed at achieving the above object, the present inventors have achieved the above object by creating the composition described below. This has led to the completion of the present invention.

That is, the present invention comprises (A) a modified resin consisting of (a) a poly-p-hydroxystyrene resin and <b) a low-viscosity liquid epoxy resin, (B) an imidazole-based catalyst, and (C) a conductive powder as essential components. This is a conductive paste that is characterized by:

The present invention will be explained in detail below.

The modified resin (A) used in the present invention is a modified resin obtained by dissolving or heat-reacting (a) a poly-p-hydroxystyrene resin and (b) a low-viscosity liquid epoxy resin. The poly p-hydroxystyrene resin (a) used here is represented by the following formula.

(However, in the formula, n represents an integer of 25 to 90.) Examples of such resins include Marukalinyoku-M (manufactured by Marukubi Petrochemical Co., Ltd., trade name), which have a molecular weight of 3000 to 80.
00 and the hydroxyl equivalent is about 120. Examples of the low viscosity liquid epoxy resin (b) which is another component of the modified resin include β(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-crisitoxypropyltrimethoxysilane, γ-glycidoxypropyl Examples include silane monomers such as methyljetoxysilane, bisphenol type low viscosity liquid epoxy resin, alicyclic low viscosity liquid epoxy resin, glycidyl ether type epoxy resin, glycidyl ester type epoxy resin, etc., and these can be used alone or in combination of two or more. Mix and use. The blending ratio of (a) poly-ρ-hydroxystyrene resin and (b) low-viscosity liquid epoxy resin is 5:95 to 40:
It is desirable that the content is in the range of 60.6 If the blending amount of poly-p-hydroxystyrene resin is 5% by weight, sufficient curing speed and mechanical strength will not be obtained, and if it exceeds 40% by weight, the mechanical strength will be poor. This is not desirable.

Examples of the imidazole catalyst (B) used in the present invention include 2MZ, 2E4MZ, C,, Z, C,, Z.

2PZ, 2P4MZ, 2M1-CN, 2E4MZCN,
C,,Z-CN,I B2MZ,2MZ-CNS,
2P4BH2, 2MA, 2MA-OK (
(manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name), etc., and these can be used alone or in a mixture of two or more. The blending ratio of the imidazole catalyst can be 0.1 to 8% by weight based on (b) the low viscosity liquid epoxy resin. When the blending amount is 0.1% by weight, the catalytic effect is low;
If it exceeds % by weight, it is undesirable because it tends to cause changes in bot life etc. over time. When producing a modified resin by dissolving or heating a poly-p-hydroxystyrene resin and a low-viscosity liquid epoxy resin, workability can be improved by dissolving it in a solvent. Solvents used here include dioxane, hexanone, benzene, toluene, turben I to naphtha, industrial kalin, acetic cellosolve, ethyl cellosolve, butyl cellosolve,
Examples include butyl cellosolve acetate-1~, butyl carpitol acetate-1~, dimethylpolamide, dimethylacetamide, N-methylpyrrolidone, etc., and these can be used alone or in a mixture of two or more.

The conductive powder (C) used in the present invention includes metal powders such as silver powder, copper powder, and nickel powder, and these can be used alone or in a mixture of two or more.
Further, there is no restriction as long as it is a conductive powder, and it may have a metal plating layer on its surface. Furthermore, there are no particular restrictions on the shape of the conductive powder. Among these conductive powders, spherical ones are preferably used, and those with a particle size of 50 μm or less are preferred. The reason for this is that if the particle size exceeds the 50 μ mark, the conductivity becomes unstable, which is not preferable.
Further, the blending ratio of the modified resin serving as the binder and the conductive powder is preferably within the range of 30:0 to 10:90 by weight. If the amount of the conductive powder is less than 70 parts by weight, satisfactory conductivity cannot be obtained, and if it exceeds 90 parts by weight, workability and adhesion will deteriorate, which is not preferable. Therefore, it is preferable to limit it within the above range.

The conductive paste of the present invention has the above-mentioned components as essential components, that is, a modified resin consisting of a poly-p-droxystyrene resin and a low-viscosity liquid epoxy resin, an imidazole-based catalyst, and a conductive powder. Other components such as a coupling agent, an antifoaming agent, a dispersing agent, etc. may be added and blended as necessary within the limits not contrary to the purpose of the invention.

The conductive paste I of the present invention can be easily produced by blending these components and uniformly kneading them using a three roll or the like. After applying this conductive paste to a predetermined location using a dispenser, screen printing, pin transfer method, etc., after several seconds to several tens of hours, various semiconductor pellets are placed on it and heated at a relatively low temperature of 100 to 200°C for several tens of seconds. Use by heating and curing with a heater block for a few seconds to several minutes. It can also be used after being cured in an oven at 150 to 200°C for several minutes.

(Function) The conductive paste of the present invention increases the curing speed and obtains strength such as sufficient adhesive strength by using a specific amount of a low-viscosity liquid epoxy resin modified with poly-p-hydroxystyrene resin. In addition, the conventional general characteristics are also maintained.

(Examples) Next, the present invention will be specifically explained by examples, but the present invention is not limited by these examples. In Examples and Comparative Examples, "r parts" means "parts by weight" unless otherwise specified.

Example 1 - 15.8 parts of YL980 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name), a low viscosity liquid epoxy resin, and Marcarin Power-M (manufactured by Marukubi Petrochemical Co., Ltd., trade name) of poly-[droxystyrene] resin. ) was dissolved and reacted with 15 parts of butyl cellosolve acetate at 100°C for 11 hours to obtain a viscous brown modified resin. To 20 parts of this modified resin, 2 parts of imidazole catalyst 0.2 parts of 4MZ (manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name) and 77 parts of silver powder were mixed, and the mixture was further kneaded with three rolls to produce a conductive paste. did.

Example 2 17 parts of Epikote 828 (manufactured by Yuka Shell Epoxy Co., Ltd., trade name), a low viscosity liquid epoxy resin, and 10 parts of Marcarin Power-M (mentioned above), a poly p-hydroxystyrene resin,
Butylcarpitol acetate-1 to 18 parts at 100°C,
A dissolution reaction was carried out for 1 hour to obtain a viscous brown modified resin.
C17Z, an imidazole catalyst, was added to 20 parts of this modified resin.
(manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name) and 78 parts of silver powder were mixed and further kneaded with three rolls to produce conductive pastes 1 to 1.

Example 3 20 parts of YL980 (mentioned above), a low viscosity liquid epoxy resin, and 15 parts of Marukalinker M (mentioned above), a poly-p-hydroxystyrene resin, were dissolved in 19 parts of diethylene glycol diethyl ether at 60°C for 1 hour. React to obtain a viscous brown modified resin. Add 2E of imidazole catalyst to 18 parts of this resin 4. 0.3 parts of M Z -CN (manufactured by Shikoku Kasei Kogyo Co., Ltd., trade name) and 82 parts of silver powder were mixed and further kneaded with three rolls to produce a conductive paste.

Comparative Example Commercially available epoxy resin-based fast-curing conductive pastes for semiconductors 1-1 were obtained.

The conductive pastes of Examples 1 to 3 and Comparative Example were applied and adhered to the semiconductor chip and the lead frame, and the semiconductor chip and the lead frame were bonded by heating and curing at 200° C. for 50 seconds using a heat block. These were tested for adhesion, presence of voids, and conductivity.
The results are shown in Table 1, and in all cases the remarkable effects of the present invention were confirmed.

In addition, the adhesion test was performed by bonding a 2.0 x 2.01111n silicon chip onto a frame (copper-based) or by silver plating, and measuring the adhesion strength at 25°C and 200°C using a push-pull gauge. It was measured using The presence or absence of voids was determined by peeling off the silicon chip from the lead frame and visually observing the occurrence of voids on the back surface of the chip. Further, conductivity was measured using a volume resistivity meter.

Table 1 (Units) *1: ○ mark: void is rolled over, × mark: void occurs "Effect of the invention" As is clear from the explanation in 1- and Table 1, The conductive paste of the present invention has excellent adhesive properties, and even when cured at low temperature and high speed, it can be firmly bonded without generating voids, and has particularly excellent adhesive strength when heated.

Further, since it can be cured at low temperature and at high speed, productivity is high, it contributes to CD, and it is possible to manufacture semiconductor devices and the like with high long-term reliability.

Claims (1)

[Scope of Claims] 1 (A) Modified resin consisting of (a) poly-p-hydroxystyrene resin and (b) low-viscosity liquid epoxy resin, (B) imidazole-based catalyst, and (C) conductive powder as essential components. A conductive paste characterized by the following characteristics: