JPS5947405B2 - conductive rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive rubber, and particularly to a conductive rubber having conductivity anisotropy, having conductivity in the thickness direction and insulation in the plane direction.

Conventionally known conductive rubber can be roughly divided into isotropic conductive rubber, which has uniform conductivity in all directions, and conductive rubber, which is formed into a thin sheet and has conductivity in the thickness direction, and conductivity in the surface direction. There are two types of conductive anisotropic rubbers that have insulating properties and conductive anisotropy.

However, although isotropic conductive rubber is easy to manufacture and has high reliability, it is extremely troublesome when connecting a large number of contacts, and conversely, anisotropic conductive rubber is extremely troublesome even when connecting a large number of contacts. However, the manufacturing method is delicate and lacks long-term reliability. The present invention improves these drawbacks and provides an inexpensive conductive rubber that is easy to manufacture and highly reliable over the long term, even though it is an anisotropic conductive rubber.

FIG. 1 shows a cross-sectional view of a conventional conductive rubber sheet. Conductive rubber 1 is generally made by mixing rubber with conductive fine powder such as silver, copper, nickel, etc. The relationship between the mixing ratio and the conductivity of the rubber is as shown in FIG. Therefore, conductivity can be obtained by mixing metal powder at a mixing ratio above a certain level, and in such a case, the rubber becomes conductive isotropic rubber. etc. It has conductivity in all directions. Furthermore, when molded into a thin sheet at a mixing ratio at which the conductivity changes rapidly, that is, the mixing ratio shown by A in Figure 2, a conductive anisotropic rubber is obtained, and aΘb,
It has conductivity in the thickness direction such as cΘd, but aΘc, bΘ
It becomes insulating in the d isoplane direction. This property is actually conductive in a minute section and non-conductive beyond that point, and the above-mentioned properties can be obtained by forming the sheet with a thickness equal to or less than this minute section. By the way, isotropic conductive rubber can be made by mixing metal powder in a certain amount or more, and can be manufactured relatively easily.

However, when connecting a large number of contacts, it is necessary to place rubber on each contact, which is extremely troublesome and costly. In addition, the anisotropic conductive rubber
As explained in the figure, the mixing ratio of metal powder must be controlled to a nearly constant value, which is difficult in terms of manufacturing.
When connecting a large number of contacts, it is sufficient to insert a rubber sheet between the contacts, and it has an advantage that isotropic conductive rubber does not have.
In order to actually make the contacts conductive, it is necessary to press the rubber, and if the mixture is slightly uneven, some conductivity may occur in the planar direction, which also poses problems in terms of reliability. The present invention
Taking these drawbacks into consideration, we created an anisotropic conductive rubber with a rough mixing ratio to a certain extent, making it easier to manufacture and reducing leakage in the plane direction and improving long-term stability.
A detailed explanation will be given below based on examples.

FIG. 3 is an external view of an anisotropic conductive rubber showing one embodiment of the present invention.

As is clear from the figure, the major feature of this conductive rubber 2 is that it has a v-convex portion 3 and a concave portion 4, which are different from conventional conductive rubber.
FIG. 4 is a side view of the conductive rubber 2. When the conductive rubber having such a shape is sandwiched between the contacts and pressed, compressive force acts on the convex portions 3, but this hardly acts on the concave portions. It should be obvious. However, the mixing ratio of metal powder in this conductive rubber 2 is slightly lower than the mixing ratio of conventional metal powder. In other words, while conventional conductive rubber has a high mixing ratio so that an electrical connection can be established upon contact with this surface, the conductive rubber of this embodiment can establish an electrical connection only after being pressed and compressed. It is structured like this. In addition, conventional isotropic conductive rubber contains ultrafine metal powder mixed in, but
In this embodiment, a slightly larger powder was used, and when the rubber was compressed, the metal powder moved and came into contact with each other, and electrical continuity was obtained only when the metal powder moved and came into contact with each other. Therefore, when the conductive rubber 2 is compressed as shown by the arrow in FIG.
．． ced has continuity, but a++c as well as b++
d is not conductive. An electrical connection device using this conductive rubber is shown in FIG. FIG. 5a is an assembled view, and FIG. 5b is a sectional view thereof. In the figure, 7 and 11 are circuit boards, and 8 and 10 are wiring patterns applied to the circuit boards 7 and 11.
These wiring patterns 8 and 10 are connected via conductive rubber 9. The convex portions of the conductive rubber are sandwiched between the two substrates 7 and 11 and pressed and fixed in alignment with the wiring patterns 8 and 10. : Therefore, the convex portion 12 is compressed and the wiring patterns 8 and 10 corresponding to this convex portion 12 are connected to each other. By the way, FIG. 6 is a diagram illustrating the conductive mechanism of the conductive rubber of the present invention, where a shows a free state with no pressure applied, and b schematically shows a compressed state 5 with pressure applied to the convex portion. It is something that 5 is a rubber part and 6 is a metal particle.

Actual metal particles are quite small, but they are shown in a larger scale to make them easier to understand. Since this conductive rubber has a low mixing ratio of metal powder as described above, in the A4 state, the rubber 5 is interposed between the metal particles 6. Therefore, electrical continuity cannot be obtained in any direction simply by contacting this rubber. However, in b, the convex portion is in a compressed state, and in this state, the metal particles 6 on the convex portion come into contact with each other because the convex portion is compressed. Therefore, electrical continuity can be established in the thickness direction of this convex part, but no compressive force is applied to the concave part, so the state remains the same as in a.
Since the insulation between the protrusions was maintained, an electrically anisotropic conductive rubber was obtained in which conduction could be obtained only in the protrusions, even though the conductive rubber was continuous. As mentioned above, the conductive rubber of the present invention has a low mixing ratio of metal powder, so its main characteristic is that it has very good rubber properties, that is, it has very good elasticity.Moreover, this property lasts for a long time, so it has a high reliability. A big improvement was made in this respect.

In addition, the tolerance of the mixing ratio due to the manufacturing process is rougher than that of conventional anisotropic conductive rubber, making it suitable for mass production. In addition, manufacturing with unevenness is very simple, as shown in FIGS. 7, 8, and 9, by forming the sheet into a sheet with a die or roller and cutting it appropriately. In the present invention, the convex portion 13 may be rectangular as shown in FIG. 7, circular as the convex portion 14 in FIG. 8, or cylindrical as the convex portion 15 in FIG. It is also possible to take various other shapes.

In addition, FIG. 10 shows another example of the use of the present conductive rubber, in which the wiring pattern 1 of each of the two substrates 16 and 19 is
7 and 20, these wiring patterns 1
A conductive rubber 18 having irregularities with a pitch of 7 and 20 plus a fine pitch is used, and the wiring patterns 1T and 20 are made to correspond to the convex portions 21 of the conductive rubber 18 as in the embodiment shown in FIG. This is not necessary and is advantageous for assembly.

Furthermore, FIG. 11 shows another embodiment of the conductive rubber of the present invention. In the previous embodiment, a convex portion was formed on one side, but in this example, convex portions were formed on both sides as shown in the figure. 22 and 23, and can be said to be a conductive rubber suitable for connection devices that require higher reliability.

The present invention has been described above in detail with reference to its embodiments, but the conductive rubber of the present invention has conductive anisotropy, can be easily mass-produced, and has high stability and long-term reliability. It can be used for connection devices and has high industrial value.

By the way, the present invention is not limited to the above-described embodiments, and various shapes of the protrusions, amount of metal powder, size, material of the rubber, etc. can be considered.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a conventional conductive rubber. FIG. 2 is a diagram showing the mixing ratio and conductivity of conductive rubber.
FIG. 3 shows a conductive rubber showing one embodiment of the present invention. FIG. 4 is an explanatory diagram of a conductive rubber that is an embodiment of the present invention. FIG. 5 shows an electrical connection device using the conductive rubber of the present invention. FIG. 6 is a diagram illustrating the conductive mechanism of the conductive rubber of the present invention. FIG. T to FIG. 9 are diagrams showing other embodiments of the conductive rubber of the present invention. FIG. 10 shows another embodiment of the electrical connection device using the conductive rubber of the present invention. 11th
The figure shows another embodiment of the conductive rubber of the present invention. 1...
...Conductive rubber, 2...Conductive rubber, 3...
...Convex portion, 4...Concave portion, 5...Rubber portion, 6...Metal particle, T...Substrate, 8
...Wiring pattern, 9...Conductive rubber,
10...Wiring pattern, 11...Substrate, 12...Protrusion.

Claims (1)

[Claims] 1. Rubber or a substance with elasticity and insulating properties equivalent to rubber, mixed and dispersed with an appropriate amount of conductive particles such as nickel powder or copper powder, is molded to have unevenness, and the convex parts are electrical connection parts and the concave parts are non-electrical connection parts. A conductive rubber characterized by being used as a connecting part.