JPS63278987A - Two-pack low-temperature curable electroconductive epoxy adhesive - Google Patents

Abstract

PURPOSE:To obtain the title adhesive which does not shrink when cured and can give a cured product of excellent electric conductivity and bonding force in good workability, by mixing a silver-filled bisphenol A epoxy resin obtained by adding a reactive diluent to a binder resin in which a silver filler is dispersed by kneading with an aliphatic polyamine curing agent. CONSTITUTION:10-25pts.wt. silver filler (a) as an electroconductive filler, such as an electrolytic silver filler of a particle diameter of 5-30mu, is added to 90-75pts.wt. epoxy resin (b), as a binder resin, based on a bisphenol A epoxy resin of the formula and dispersed in it by kneading, and a suitable amount of a reactive diluent such as phenyl glycidyl ether to the above obtained dispersion to obtain a silver-filled bisphenol A epoxy resin (A). 100pts.wt. component A is mixed with 2-3pts.wt. aliphatic polyamine curing agent (B) such as triethylenetetramine which is added before use to decrease its viscosity to 10,000-50,000cP. In this way, the title adhesive of a curing temperature of 50-80 deg.C can be obtained.

Description

Detailed Description of the Invention (1) Purpose of the Invention [Field of Industrial Application] The present invention is applicable to lead wire contact adhesion, magnetic/ceramic filling and encapsulation, silk screen printing, circuit board repair, molded carbon and metal The present invention relates to a two-component low-temperature heat-curing conductive epoxy adhesive that can be used for a variety of purposes, such as adhesion of various electronic devices to lead frames and alumina substrates, surface adhesion of PTC and metal, and adhesion between Nesa glass.

[Prior technology] This type of two-component conductive epoxy adhesive can be used for conductive bonding of plastics (epoxy, phenol resin, etc.) that could not be soldered in the past, for bonding Nesa glass used in liquid crystal display tubes, and for micro motors. It is an indispensable material for adhering phosphor bronze and carbon brushes, and for adhering lead wires for crystal resonators, SDC meters, etc.

In particular, recent developments in the semiconductor industry have been remarkable, with ICs and LSIs being developed one after another and being mass-produced. However, in order to reduce costs and improve productivity, conductive adhesives made of epoxy resin mixed with silver powder have come into widespread use, and are now considered the most promising method among die bonding methods. ing.

However, this type of conventional two-component high-temperature heating conductive epoxy adhesive generally has a silver content of 70 to 90% by weight, and the mixing ratio of silver filler epoxy resin and curing agent is 1=1.
Or, SH thinner is used as the dilution solvent as 1:2, the viscosity is 100,000 to 200,000 CPS, and the curing conditions are also 100,000 to 200,000 CPS.
°C to 130°C x 1 hour (hour) or 150°C x 0° for 5 days, the viscosity is high, the kneading properties are poor, and the wettability related to adhesive strength is also poor. In other words, when designing the formulation of epoxy conductive adhesives, the viscosity of the raw material epoxy resin is usually high, so when mixed with silver filler, the viscosity increases further, making application workability with microdispensers, silk screen printing, etc. extremely poor. As a result, when surface adhering the coated object, if a solvent is included, the curing agent will foam when heated and hardened, resulting in property deterioration (conductivity). variation, decrease in adhesive strength)
Solvent-free conductive adhesives are desirable for use in assembling electronic parts, and when used in highly airtight parts, minute amounts of volatile matter can have a negative effect on switch contacts and metal parts. Although I knew that I needed to be careful because it could cause harmful effects, and that products with no outgassing were required especially for die bonding of ICs and LSIs, I had no choice but to use a solvent to reduce the viscosity. When adhering in an oven, such as when adhering lead wires, workability can be improved by adjusting the viscosity by adding a solvent. Since the adhesive is hermetically sealed with a resin or the like, residual solvent may cause defects, so adhesives containing solvents are not preferred.

In addition, since the curing temperature is a high temperature heat curing type and it must be heated for a long time, the adhesive itself deteriorates and changes in quality, resulting in a tensile shear strength of only 29 to 62 KW/7. This is a drawback in that it has an adverse thermal effect on surrounding electronic components and deteriorates their electrical characteristics.

[Problems to be Solved by the Invention] In view of the conventional drawbacks, the present invention lowers the adhesive viscosity to improve kneading properties, improves wettability and spreadability to increase adhesive strength, and achieves a low curing temperature and short heating time. The purpose of the present invention is to provide a two-component low temperature heat-curable conductive epoxy adhesive which has significantly improved curing conditions and suppresses as much as possible adverse thermal effects during adhesion.

(2) Structure of the invention [Means for solving the problems] The two-component low-humidity heat-curable conductive epoxy adhesive of the present invention includes silver filler with a particle size of 5 to 30 μm as a conductive filler and a silver filler dispersed therein. The usage ratio with the kneaded binder resin is 9.
0-75: Bisphenol A-based silver filler epoxy resin with a ratio of 10-25 and an appropriate amount of reactive diluent such as pheniglycidyl ether, and an aliphatic polyamine-based curing agent of triethylenetetraamine caps added during use. M% of the bisphenol Δ-based silver filler epoxy resin 1
The adhesive strength is increased by reducing the viscosity to 10,000 to 50,000 CPS and setting the curing temperature to 50°C to 80°C.

[Example] Examples of the present invention will be described below.

The two-component low-temperature heat-curing conductive epoxy adhesive of the present invention is a silver-filler epoxy resin (hereinafter also referred to as the main ingredient) polyamine-curing type, and is a cream-like paste with a viscosity of 10,000 to 50,000 CPS and is easy to work with. Since it contains no volatile solvents, there is no shrinkage during curing, and the cured model has high conductivity and strong adhesive strength, and is also suitable for filling and encapsulation.

The epoxy resin that serves as the main binder is 1. It is a low viscosity liquid prepared with reactive diluents that adjust the viscosity and add flexibility to the cured resin.

The epoxy resin is based on bisphenol A, and its basic structure is as shown below.

OC City 011 Particle size of 5-30 μm, preferably 5-10 μm, which is precisely kneaded and dispersed with the conductor mixed with the base material, i.e., epoxy resin.
Electrolytic silver powder and reduced silver powder are used for the μm silver powder, and the weight ratio of silver filler to the main ingredient is 10 to 25:9.
0-75. Preferably it is 17:83.

Electrolytic silver powder is produced by re-electrolyzing electrolytic silver to precipitate it in a dendritic form, and is a silver powder with high purity and good moldability.

Further, the reduced silver powder is obtained by adding a reducing agent such as formalin to a silver salt aqueous solution, reducing and precipitating it, and drying this to obtain a powder.

The properties of these silver powders include fine particle size, excellent dispersibility, and no cohesion.

The curing agent is generally selected based on the viscosity of the mixture, pot life, curing conditions, and adhesive strength, etc. Triethylenetetraamine, which is less likely to cause blistering and can carry out the curing reaction in a small amount. An aliphatic polyamine curing agent such as the following is used.

Triethylenetetraamine (TTA-triet
The chemical structural formula of hylene tetramine is as shown below.

TODON (JTO CTObN C) CTODON (JTO CTREN 1-1? The main agent and curing agent that are mixed together are cured by a chemical reaction, but a chemical equivalent is required for the curing reaction. In other words, in order for the epoxy groups of the epoxy resin and the amine groups of the polyamine to bond in just the right amount and form a strong three-dimensional structure, chemical equivalents of each must be used. FIG. 1 shows a correlation characteristic diagram showing the test results of adhesion strength when the amount of .

Based on FIG. 1, 2 parts (by weight) of the curing agent was calculated as the optimum standard value for 100 parts (by weight) of the main agent. Therefore, the first
As shown in the figure, the adhesion strength is affected if the distribution ratio of the base agent and curing agent to be mixed is too much or too little than the standard value.

[Characteristics of the Invention] The basic characteristics required of a conductive adhesive are conductivity due to the shape of the silver filler, such as scale-like shape and particle size, and adhesive strength due to the resin. It is important that these two characteristics do not deteriorate over time and maintain long-term reliability.

Test examples of the characteristics of the present invention will be explained below.

■General properties As shown in Table 1 below.

(2) Curing conditions It is determined by the combination of heating temperature and time. For example, although curing proceeds at room temperature (25° C.), it takes more than 48 hours, and 8I electric power does not give satisfactory results.

Therefore, heating to at least 50°C is required.

The following Table 2 shows the test results when the base resin: curing agent was mixed at a ratio of 100:2.

Table 2 Ru.

Furthermore, Figure 2 shows the relationship between curing temperature and volume resistivity when mixing base resin: curing agent at a blending ratio of 100:2, and the relationship between conductivity when heating time is varied in low humidity heating at 50'C. Each is shown in Figure 3.

(2) Adhesive Strength The following Table 3 shows the test results when the adhesive strength was measured at a ratio of 100:2 of main ingredient: curing agent and curing conditions were 80'C x 15 minutes and 1.41 hours left at room temperature.

Table 3 However, *mark indicates damage inside the adhesive layer.

■Heat resistance In the heat resistance test at 190°C, the adhesive strength hardly changes.

Table 4 below shows the results of a heat resistance test after mixing the base resin: curing agent at a blending ratio of 100:2, curing at 80° C. for 15 minutes, and leaving it at room temperature for 24 hours.

Table 4 However, the sample was steel/steel bonded.

■Relationship between temperature and strength Main ingredient: Curing agent - Mixed at a blending ratio of 100:2, curing conditions were 80℃ x 15 minutes, and strength after being left at room temperature for 24 hours and at each temperature and strength after being left at room temperature for 1 hour and 30 minutes. The test results are shown in Figure 4.

■Relationship between coating thickness/width and volume resistivity Main agent: Curing agent - Mixed at a blending ratio of 100:2, curing conditions were 80℃ x 15 minutes, and measurement test results after being left at room temperature for 24 hours are shown in Table 5 below. show.

Table 5 However, the sample is applied to the substrate PMMA (acrylic board).

[How to use the invention] Examples of use of the adhesive of the present invention will be explained below.

In order to exhibit good performance, it is important to accurately measure the base agent and curing agent and to mix and stir well.

■Mixing ratio Main agent: hardening agent = 100:2 (1-m%) ■ Mixing guideline Main ingredient...1g Hardening agent...1 drop (approx. 0.029> Mix both well.

■Curing conditions (standard [) 50℃×2 hours・1,5 XIO”Ω-crs80℃
x 15 minutes -5 For example, store it in a -20℃ freezer for 120 hours (5
After leaving it for several days), it was taken out and returned to room temperature with stirring, and used according to the normal curing procedure. No abnormality was observed in the performance.

(2) Adjustment of viscosity using a solvent When further adjustment of the viscosity is unavoidably necessary due to dimmervencing, the mixture of the present invention can be diluted to 5% (by weight) with toluene or ethyl acetate.

(3) Effects of the Invention Thus, the adhesive of the present invention is cured at low temperature heating of 50 to 80°C. ■It is a creamy paste that is easy to mix and does not drip. ■ No shrinkage after curing (suitable for filling and encapsulation. ■ Stable and high conductivity is obtained. ■ Strong adhesion and compatible with many new materials. ■ Excellent heat and moisture resistance. ■ Can be used with solvents The viscosity can be adjusted.■Good dispensing properties.■Excellent overlay hiding power.■It has a variety of features compared to conventional products, such as long shelf life and is effective for approximately one year at room temperature.

Since the present invention cures at a low temperature and heats for a short time, it does not cause thermal damage to the adhesive itself, the parts to be bonded, or surrounding parts, maintains quality and reliability, and generally has higher adhesive strength than conventional products. It has an excellent technological innovation impact effect on the electronic industry, such as improving workability by more than 20%, saving energy and cost, and establishing a production system.

[Brief explanation of drawings]

FIG. 1 is an adhesive force correlation characteristic diagram when the amount of curing agent is varied with respect to 100 parts of resin in the example of the present invention, and FIG.
The figure is the same correlation characteristic diagram of curing temperature and volume resistivity, 3rd
The figure is a correlation characteristic diagram of conductivity when heating time is changed at the same low temperature heating at 50℃, and Figure 4 is a correlation characteristic diagram of the same temperature and tensile shear strength after being left at room temperature for 1 hour and 30 minutes. It is. Fig. 1 Fig. 2 Fig. 3 Ho Amechi interval (hrs) Fig. 4 Ka8jiang cliff (6c)

Claims (1)

[Claims] 1. The weight ratio of silver filler with a particle size of 5 to 30 μm as a conductive filler and a binder resin in which this is dispersed and kneaded is 9.
0-75: Bisphenol A-based silver filler epoxy resin with an appropriate amount of reactive diluent added at 10-25, and the weight percentage of the aliphatic polyamine-based curing agent added upon use of the bisphenol A-based silver filler epoxy resin. 2 to 3 parts per 100 parts to lower the viscosity and increase the curing temperature to 50%.
A two-component low-temperature heat-curing conductive epoxy adhesive 2 whose adhesive strength is enhanced by heating the adhesive at a temperature between ℃ and 80℃, and a phenylcidyl ether as a reactive diluent. The two-component low-temperature heat-curable conductive epoxy adhesive 3 according to claim 1, wherein triethylenetetraamine is used as the aliphatic polyamine curing agent. A two-component low-temperature heat-curable conductive epoxy adhesive 4, whose viscosity is reduced to 10,000 to 50,000 CPS, which has high kneading properties and good wettability to increase adhesive strength.Claim 1
Two-component low-temperature heat-curing conductive epoxy adhesive according to item 2, item 2, or item 3.