JPS5922754B2 - Conductive adhesive method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a bonding method and adhesive that absorb differences in thermal expansion coefficients existing between members to be bonded and have good electrical conductivity and adhesive properties.

Conventionally, when the difference in thermal expansion coefficient between the two is extremely large, such as when joining an aluminum alloy product and a fired product of metal oxide, and when electrical continuity is required between the two, non-adhesive bonding has been used. The disadvantage of this method is that conductivity decreases due to oxidation corrosion on the joint surface, foreign matter fitting, etc., and to prevent this, it is necessary to separately provide waterproof and dustproof parts, resulting in high costs.

On the other hand, in the adhesive method, a large amount of powder of a good conductor such as silver, aluminum, copper, carbon, etc. is blended in order to impart electrical conductivity to the adhesive, which results in a lack of flexibility and When a new temperature change or repeated cooling and heating is performed, the adhesive layer cracks and peels due to the difference in thermal expansion coefficient between each material and internal stress, which causes drawbacks.

The present invention is applicable to products that have a significant difference in coefficient of thermal expansion between the two, such as when bonding an aluminum alloy product and a fired product of metal oxide, or that are used in an environment with significant temperature changes. As a result of our research in search of an adhesive method and adhesive that have good electrical conductivity without causing cracks in the adhesive layer even when exposed to heat, we have developed the adhesive method and adhesive of the present invention, and hereby propose them. be.

The bonding method and adhesive of the present invention includes 450 to 550 parts by weight of conductive metal powder and 6 to 21 parts of granular material with an average diameter of 0.1 to 1.0 mm per 100 parts by weight of the epoxy resin adhesive.
By using a conductive adhesive in which the granular material is exposed on the surface of the adhesive, a bonding member and a bonded member having a large difference in coefficient of thermal expansion are bonded to each other with a desired adhesive layer thickness. It is characterized by electrically conductive adhesion.

As the epoxy resin adhesive used in the present invention, for example, the epoxy resin adhesives shown in Table 1 below are appropriately blended and used with the addition of a curing agent.

Incidentally, Araldite is a trade name of Nagashio Ciba Co., Ltd., excluding reinforcing agents, fillers, etc. The conductive metal powder to be added to the epoxy resin can be anything that is normally considered to be a good conductor, such as gold, silver, nickel, iron, copper, or aluminum, or can be of any type that is corrosion resistant and conductive. Even good products may be expensive, and even products that are inexpensive and available in large quantities may have poor corrosion resistance and cannot maintain constant performance over a long period of time.In general, it is important to consider price, conductivity, etc. Therefore, silver is used. In addition, the proportion of conductive metal powder mixed in the epoxy resin adhesive is the same as that of the epoxy resin conventionally used as a conductive adhesive with 80% silver added (hereinafter referred to as conventional conductive adhesive). Based on the electrical resistance, the following test showed that the epoxy resin adhesive 10
The amount was limited to 450 to 550 parts by weight relative to 0 parts by weight. The shape of the conductive metal powder is preferably plate-like or scale-like, and suitably has a particle size of 0.2 to 1.0 μm and an apparent density of 1.4 to 1.8 y/d. The various amounts of silver powder were determined by the weight of Araldite AVl38lOO shown in Table 1 above and the weight of Araldite CY.
In addition to 22l and 25 parts by weight, γlardite H is used as a curing agent.
A plate-shaped conductive adhesive having a thickness of 0.1 to 0.21 nS and a length of 1511 mm was prepared by mixing 99846.5 parts by weight of the epoxy resin adhesive.

As shown in Figure 1, aluminum plates 2 with a thickness of 0.15 mm and a length of 5 mm were connected to both ends of the conductive adhesive plate, and the electrical resistance value of the conductive adhesive plate was measured using an electrical resistance measuring device 3. . An adhesive plate was also prepared using the conventional conductive adhesive according to the preparation method of the present invention, and the electrical resistance value was found to be 4.5 ohm (hereinafter referred to as Ω). FIG. 2 shows the resistance measurement results of the conductive adhesive plate of the present invention. As shown in Figure 2, if the amount of conductive metal powder is less than 450 parts by weight, the electrical resistance will rise rapidly and the conductivity will deteriorate, and if it is more than 550 parts by weight, the amount of conductive metal powder added to the adhesive will be too large. If the adhesive becomes too thick, the electrical resistance will decrease somewhat, but the flexibility will decrease, and it will no longer be useful as an adhesive.
Limited to parts by weight.

Next, the granular member further added to the conductive adhesive is:
The conductive adhesive layer formed between the adhesive member and the adhered member, which have different coefficients of thermal expansion, has a desired thickness, and the flexibility of the conductive adhesive is effectively utilized to increase thermal expansion. It is added to conductive adhesives as a spacer to absorb the difference in rate and prevent cracking and peeling of the adhesive part, but any type of adhesive can be used as long as it satisfies the effect as a spacer. For example, non-metallic particles include glass particles, alumina particles, carbon particles, heat-resistant plastic particles, glass balloons, etc., and metallic particles include copper, iron, aluminum, zinc, tin, nickel, etc. Examples of materials that can be used in the present invention to obtain good performance include electrically conductive metal particles, and materials that can maintain stable performance over a long period of time include copper and aluminum. Using. In addition, if the diameter of the granular material is less than 0.1, it becomes useless as a spacer, and if it exceeds 1.01t11, the thickness of the adhesive layer increases, the electrical resistance increases, and the conductivity decreases. The size of the granular member should be between 0.1 and 130 mm in average diameter.
It was limited to 11. The thickness of the adhesive layer is mainly determined by the size of the granular material blended as a spacer, and is 0.1 to 1 for the reasons mentioned above.

A range of 0 dragons satisfies both electrical conductivity, adhesive performance, and thermal expansion absorption performance.

EXAMPLES The conductive adhesive of the present invention will be specifically explained below with reference to Examples.

Example 1 A conductive adhesive of the present invention was prepared with the following composition.

Composition of Conductive Adhesive of Example 1 The above-mentioned conductive adhesive 1 was made of an aluminum alloy die-cast block (thermal expansion coefficient 23.5 x 10-6) as shown in Fig. 3A.
deg-1) Thickness 0.5m7 on 4! L and coated with aluminum titanate (metal oxide fired product 5).
Al2O3-TiO2 thermal expansion approximately 400 to 0)
was placed and stamped, and the copper particles were bonded to the surface of the conductive adhesive so that they were exposed and created a spacer effect.

FIG. 3B is an enlarged sectional view of the portion indicated by the dashed arc in FIG. 3A. In addition, 1a in FIG. 3B represents a copper particle, and 1b represents a resin. Five test pieces were prepared as described above, and five test pieces were prepared using a conventional conductive adhesive as a control.
A cooling test of heating at 120°C for 30 minutes and then cooling at -30°C for 30 minutes was repeated 100 times.

The results are shown in Figure 4. The solid line x in FIG. 4 represents the average value of the thermal test results for test specimens using the conductive adhesive of the present invention, and the broken line Y represents the average value of the thermal test results for specimens bonded using the conventional conductive adhesive. The upper and lower lines represent the variation in measured values.

When the conductive adhesive of the present invention is used, the strength decreases little because there is no cracking in the adhesive layer.When a conventional conductive adhesive is used, the adhesive strength initially shows a strong value, but the adhesive layer It can be seen that cracks were generated in the bonding layer, and as the cracks progressed, the adhesive strength significantly decreased.

Furthermore, the electrical resistance value of five test specimens using the conductive adhesive of the present invention was 0.01Q, which is extremely superior in both strength and resistance value when compared with conventional conductive adhesives. . Next, the shear adhesive strength of the electrically conductive adhesive of the present invention and the conventional electrically conductive adhesive was measured by the following method.

How to measure shear adhesive strength Between two metal plates with a length of 100 mm, a width of 25 mm, and a thickness of 1 mm, a length of 10 mm and a width of 25 m and 77! , thickness -0.2
The conductive adhesive of the present invention and the conventional conductive adhesive were applied so that the thickness of the conductive adhesive of the present invention and the conventional conductive adhesive were applied, and the adhesive was cured by holding at 110°C for 40 minutes. A tensile force in the opposite direction was applied to the metal plates, and the force when the two metal plates separated was measured.

The measurement results of the shear adhesive force are shown in FIG.

In FIG. 5, the solid line X shows the results using the conductive adhesive of the present invention, and the broken line Y shows the results using the conventional conductive adhesive. As shown in FIG. 5, the conductive adhesive of the present invention also showed better results than the conventional conductive adhesive in the shear adhesion test.

Example 2 A conductive adhesive of the present invention was prepared with the following composition.

Composition of Conductive Adhesive of Example 2 Using the above adhesive, a thermal test and a shear adhesive strength test were conducted, and similar to Example 1, good results were obtained.

As described above, the conductive adhesive according to the present invention firmly adheres members with significantly different coefficients of thermal expansion even under extremely harsh conditions, and does not crack or peel off.
It is an adhesive that can maintain electrical conductivity, and the present invention is of extremely high value industrially.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of an electrical resistance measuring device, Figure 2 is an electrical resistance measurement test with changes in silver content, and Figure 3 A shows the results of the test using the conductive adhesive of the present invention. Figure 3B is an enlarged cross-sectional view of the portion indicated by the broken line arc in Figure 3A, and Figure 4 is a side view of the test product, and Figure 4 is a side view of the test product. FIG. 5 is a graph showing the results of a thermal test of a test piece; FIG. 5 is a graph showing the results of a shear adhesion test of the conductive adhesive of the present invention and a conventional adhesive. In the diagram, 1... Conductive adhesive, 2... Aluminum plate, 3... Electric resistance measuring device, 4...
...Aluminum alloy die-cast block, 5...
・・・・Hail the fired metal oxide products.

Claims (1)

[Claims] 1 450 to 550 parts by weight of conductive metal powder and an average diameter of 01 to 1.0 m to 100 parts by weight of epoxy resin adhesive
Using an adhesive to which 6 to 21 parts by weight of granular material of m is added, an adhesive layer of a desired thickness is formed between an adhesive member and a member to be adhered, and the adhesive layer is bonded, and electrical conductivity is imparted. A method for electrically conductive bonding of two members having different coefficients of thermal expansion.