JPS6193505A - Conductive paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrically conductive pastes, particularly electrically conductive pastes with fail-safe properties.

Conventional technology 3 and conventional conductive pastes, especially carbon paste, are used in various components such as keyboard switch contacts and printed circuit board conductors of electronic and electrical equipment, which may be subject to high voltage or high temperature due to incorrect operation or some external factor. When this voltage is applied, dielectric breakdown due to current heat generation and discharge of the resin portion of the adhered substrate progresses, and a carbonized conductive path is formed, leading to current heat generation combustion, which may pose a safety problem.

The present invention was made in order to provide a conductive paste that solves the above problems without sacrificing the excellent conductivity and good adhesion to an adherend substrate that conventional conductive pastes have.

That is, the present invention uses about 10 to 65 parts of conductive powder per 100 parts by weight of the binder resin and an inorganic filler whose capacity changes when dehydrated at high temperatures (hereinafter referred to as inorganic filler).
The present invention relates to a conductive paste containing 1 part by weight of about 40 to 70 parts.

The binder resin used in the present invention may be appropriately selected from those conventionally used as binders for conductive pastes, and is not particularly limited. Examples include polymers and acrylic resins.

The conductive paste used in the present invention is not particularly limited, and may be carbon powder or metal powder, such as Ketjen black or fine copper powder, but tracking breakdown may occur due to high voltage application.

The composition of the conductive powder is about 10 to 65 parts by weight, preferably about 15 to 3 parts by weight, per 100 parts by weight of the above binder resin.
If the amount of 0 parts is less than xoM@ part, sufficient conductivity cannot be obtained, and if the part of 65 parts is more than 1 part, the adhesion or adhesion of the paste to the substrate to be adhered will be impaired.

For example, in the case of carbon powder, the particle size of the conductive powder is on the order of mμ, and conductive carbon powder having such a particle size is preferable.

The inorganic filler used in the present invention can be used at high temperatures, e.g.
It is a filler that undergoes a change in capacity when dehydrated at a temperature of 600°C to 600°C, and if an abnormal heating accident occurs as described above, it will cause "cracks" or "swelling" in the conductive layer, causing abnormal heating parts. It has a fail-safe effect by converting it into an insulator.

Such inorganic fillers include metal hydroxides, such as magnesium hydroxide, aluminum hydroxide, nickel hydroxide, calcium hydroxide, etc., or hydrated clay minerals, such as vermiculite, but the dehydrated product may be heated to even higher temperatures. Magnesium hydroxide, which sublimes and results in cracking, and vermiculite, which causes swelling, are preferred.

The particle size of the inorganic filler is usually 0.1 to 100 microns, preferably about 0.1 to 10 microns.

Blend I of the inorganic filler is preferably about 40 to 70 parts by weight based on 100 parts by weight of the binder resin.
If the amount is 1 part by weight or less than 40 parts by weight, the desired effect of the present invention will not be achieved reliably, and if it exceeds 70 parts by weight, the adhesiveness as a conductive paste will decrease.

The conductive paste according to the present invention is prepared by kneading predetermined amounts of the binder resin, conductive powder, and inorganic filler using a suitable solvent in a conventional manner.

The use of solvents should be kept to the minimum necessary. Examples of such solvents include a mixture of methyl ethyl ketone and ethyl alcohol, but a mixture of methyl ethyl ketone and ethyl alcohol? g agent is common.

As a diluent for the conductive paste, for example, butyl calpitol or the like is used.

The substrate to which the conductive paste prepared as described above is applied is not particularly limited, but includes various synthetic resin molded bodies, such as polyester films, ceramic substrates, phenolic resin laminates, and the like.

Hereinafter, the present invention will be explained by examples.

Example 1 Polybutyral resin 60% methyl ethyl ketone solution 1
00g and phenol [l1u50% ethanol solution 75y were mixed, and 30g of conductive carbon powder (Ketjenblack EC) was thoroughly kneaded while being crushed. Then, magnesium hydroxide 601 was blended, and butyl was added as a diluent. A carbon paste was prepared by adding 200 g of calpitol.

The obtained carbon paste was applied to the recesses (4 blades ×
A carbon paste embedded resistor was created by heat-treating at 150''C for 1 hour.The electrode was connected to the outlet terminal of a tracking tester, and the applied voltage was increased. , when a minute discharge begins to occur,
The voltage was rapidly increased until the current was 0.4 A, and thereafter the voltage was kept constant to observe the state of heat generation and combustion of the resistor to evaluate fail-safe characteristics. The results are shown in Table-1.

Apply the above carbon paste onto the insulator. Application thickness: 1
00 μ] and 150° C. for 1 hour to form a cured carbon film (thickness: approximately 30 μ), and the adhesion was evaluated. The results are shown in Table-1.

Also, apply the above carbon paste on the Tetron film. Application thickness: 100μ; Application area: 16XIQ, ff
shoulder), heat treated at 150°C for 1 hour to form a hardened carbon film (thickness: 30μ), and 3ffNXI on the edge.
Place a QiWN brass plate (thickness: l, Qm+w) and
A pressure of 0 g was applied, and the electrical resistance value between the brass plates was measured. The results are shown in Table-1.

Example 2 The fail-safe properties, adhesion, and electrical resistance of a cured carbon film prepared in the same manner as in Example 1 except that 60 Da of vermiculite powder (particle size 25 μm) was used instead of magnesium hydroxide were evaluated in Example 1. I investigated in the same way. The results are shown in Table-1.

Reference example: Commercially available carbon paste containing phenolic resin binder (other components and component ratios are unknown) 4009
In the same manner as in Example 1, using a paste containing 60 g of magnesium hydroxide, the fail-safe characteristics, adhesion g, and electrical resistance of the cured carbon film were investigated. The results are shown in Table 1. 〇 Ratio 1 Bite Example 1 Fail-safe characteristics of the cured carbon film prepared in the same manner as in Example 1 except that magnesium hydroxide was not added.
Adhesion and electrical resistance values were examined in the same manner as in Example 1,
The results are shown in Table-1.

Comparative Example 2 Comparative Example 2 was the same as Comparative Example 1 except that the amount of carbon powder was 15 g. The measurement results are shown in Table-1.

Comparative Example 3 Same as the above reference example except that magnesium hydroxide was not blended. The measurement results are shown in Table-1.

Table 1 1) At the same time as overcurrent occurs due to discharge, cracks or swelling occur in the cured carbon film, the ammeter reading becomes zero, and heat generation stops.

2] After the start of discharge, lower the voltage and set the current to 0.4A to continue the discharge or complete combustion.

3) When the specimen was scraped with a knife, there was no chipping or peeling, and it was scraped like planer shavings.Also, 11 pieces were perpendicular to each other vertically and horizontally at 1-square intervals on the carbon paste film that had been heated and hardened on the adherend. Even if 10 (L) squares were made and cellophane tape was crimped on top of the squares and then rapidly peeled off, no change was observed.

Effects of the Invention The conductive paste according to the present invention is completely comparable to conventional conductive pastes in terms of conductivity and adhesion, and effectively eliminates safety problems caused by overheating and abnormal heat generation. The electrically conductive paste according to the invention can therefore easily replace the conventional electrically conductive pastes used in particular in the electrical and electronic industry.

Claims (1)

[Claims] 1. A conductive material containing, per 100 parts by weight of binder resin, about 10 to 65 parts by weight of a conductive powder and about 40 to 70 parts by weight of an inorganic filler whose capacity changes when dehydrated at high temperatures. sex paste. 2. The conductive paste according to item 1, wherein the inorganic filler is magnesium hydroxide or vermiculite.