JPS6052187B2 - conductive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive adhesive, and more particularly to a conductive anisotropic conductive adhesive that exhibits conductivity only in a specific direction.

2. Description of the Related Art Conductive adhesives have been known in which conductive particles such as silver or carbon black are mixed into an insulating adhesive such as epoxy.

It has been experimentally shown that by extremely reducing the mixing ratio of conductive particles in such conductive adhesives, conductive anisotropy, which is conductive only in the vertical direction and insulating in the horizontal direction, can be obtained. It recognized. In this conventional method, there is only one conductive particle in the thickness direction (opposing direction) between the terminals to be connected, and in the lateral direction, conductive particles are arranged so that the chain contact of the conductive particles is broken. The diameter and mixing ratio were determined. However, this has the drawback that its uses are limited and it is difficult to satisfy both good electrical conductivity in the vertical direction and high insulation properties in the horizontal direction. The present invention aims to improve the drawbacks of the above-mentioned prior art, and one embodiment thereof will be described below.

In FIG. 1, reference numerals 1 and 2 are terminal plates, and connection electrodes 3 and 4 are formed on opposing surfaces thereof by a well-known printed wiring technique or the like. The connecting electrodes 3 and 4 are arranged at minute pitches as shown in FIG. In Figure 1, terminal plates 1 and 2
A conductive adhesive 5 according to the present invention exists between them, and the opposing connection electrodes 3 and 4 are electrically connected to each other via this conductive adhesive 5, and there is no electrical connection between adjacent electrodes. is insulated. Here, the conductive adhesive 5 includes conductive particles 7 such as silver and alumina J in an epoxy-based insulating adhesive 6.
The insulating spacer particles 8 are mixed in an appropriate ratio (see Figures 3 and 4), but the mixing ratio of the conductive particles 7 varies in all directions when hardened without being pressed (hardened by leaving to stand). It exhibits insulating properties and exhibits conductivity only in the pressing direction when pressed and hardened, i.e., 3% by volume or less, preferably about 10±5% by volume, and the proportion of spacer particles 8 mixed is very small. It is.

Further, the spacer particles 8 used have a size several times or more larger than the diameter of the conductive particles 7.

For example, when the conductive particles 7 have a diameter of 1 to 2 μm, the spacer particles 8 have a diameter of about 10 μm. For example, apply this conductive adhesive 5 all over one of the terminal plates 1 and 2 in a strip shape across the connecting electrode as shown by the dashed line in FIG. Turn them inside and align and stack them (Figure 3).

At this time, the conductive adhesive 5 exhibits insulation in all directions. Then, when both terminal plates 1 and 2 are pressed, the conductive adhesive 5
spreads as shown by the two-dot chain line in FIG. 2, and finally this pressure is limited by the spacer particles 8 (FIG. 4). Due to this pressing, several chains are formed in the conductive particles 7 in the vertical direction, and several places where the chains are interrupted in the horizontal direction are formed.

The reason why the conductive particles 6 exhibit such an arrangement is that when the adhesive 5 spreads as shown in the second figure, the epoxy adhesive 6 tends to spread out due to its fluidity, but the conductive particles 7 and This is thought to be due to the fact that the spacer particles 8 are difficult to flow laterally. By arranging the conductive particles 6 as shown in the fourth figure, the opposing connection electrodes 3 and 4 are electrically connected to each other. However, the adjacent connection electrode 3 or 4
Comrades remain electrically isolated. Assuming that the spacer particles 8 were not mixed, the compression of the conductive adhesive due to the above-mentioned pressing would progress to a level greater than that shown in FIG. It also shows electrical conductivity.

In other words, the spacer particles 8 control the pressing force within a range where the conductive adhesive 5 can maintain insulation in the lateral direction. As described above, according to the present invention, among the connection electrodes formed at minute pitches on the opposing surfaces of two terminal boards, the electrical connection between the opposing electrodes is made via a conductive anisotropic adhesive. When pressing, the spacer particles limit the facing distance between both terminal plates, so the conductive adhesive does not exhibit conductivity in the direction perpendicular to the pressing direction (lateral direction). It can reliably prevent short circuits between matching connection electrodes,
High reliability is guaranteed.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of two terminal boards connected using the conductive adhesive of the present invention, Figure 2 is a plan view of the main parts of the terminal plate, and Figure 3 is the conductivity before pressing. FIG. 4 is an enlarged sectional view showing the state of the conductive adhesive when pressed. 1, 2... Terminal board, 3, 4... Connection electrode, 5... Conductive adhesive, 6... Insulating adhesive, 7.・・・・・・Conductive/Electrical particles, 8・・・・・・
・Spacer particles.

Claims (1)

[Claims] 1. Conductive particles mixed in the insulating adhesive at a rate that exhibits insulation in all directions when cured without being pressed, and exhibit conductivity only in the direction of pressure when cured with pressure, and the above-mentioned insulating adhesive. It is dispersed and contained in a mixture consisting of a conductive adhesive and the above-mentioned conductive particles, and has a larger diameter than the above-mentioned conductive particles, and is used when the above-mentioned mixture is sandwiched and pressed between terminals to be connected. A conductive adhesive comprising insulating spacer particles that limit the amount of compression of the mixture interposed between terminals.