JPH0437523B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a so-called anisotropically conductive sheet having conductivity only in the thickness direction of the sheet.
In particular, not only can the pattern spacing be made small, but also by selecting the lattice spacing of the woven fabric and the fine metal powder,
The present invention relates to an anisotropic conductive sheet that can be adapted to any mating pattern spacing. Anisotropically conductive sheets are sheets that have conductivity only in the thickness direction and are electrically insulated in the direction that crosses that direction. It is useful as a material for interconnecting circuit elements housed in a limited space such as, for example, and is widely used.

(Prior art) Conventionally known anisotropically conductive materials include (a) conductive rubber in which conductive powder or conductive fibers are dispersed, and electrically insulating rubber, which are alternately layered. After that, the so-called elastic connector is sliced perpendicularly to the stacking direction, (b) the conductive layer and the insulating layer are coated with paint, and sliced in the same manner as (a) to reduce the pitch. (iii) Pressure-sensitive conductive sheets containing a controlled amount of graphite or metal particles dispersed in a polymeric substance.

(Problem to be solved by the invention) However, in (a), the conductive rubber that is filled with a large amount of various conductive members in order to lower the resistance,
Naturally, it has high hardness and poor rubber elasticity,
In addition, since conduction with the electric circuit is caused by pressurization, a constant pressure load is required, and the strength of the connected object must be considered to be able to withstand the above load. (B)
Although it is possible to reduce the pitch in this case, it also has the disadvantage of requiring constant pressure contact load. In (b) and (c), although conduction occurs in the thickness direction of the sheet during pressure welding, insulation is likely to be lost in the intersecting horizontal direction as well, and there is a limit to increasing the packaging density. It had disadvantages and disadvantages that it could not be used for connection.

(Means for Solving the Problems) The present invention solves various problems when attempting to connect extremely small proximity circuits, so-called low pitch, using such conventional anisotropic conductive sheets. This has a structure in which spherical fine conductive metal is embedded in an empty lattice of a sheet-like insulating fabric, and both ends of the sheet-like insulating fabric in the thickness direction are covered with an insulating resin. It is an anisotropically conductive sheet characterized by the fact that the insulating resin coated melts during pressure welding or thermocompression welding to the adherend, and the spherical fine conductive metal is exposed from the insulating resin, and the spherical fine powder conductive metal is exposed directly to the adherend. Since it comes into contact with the adherend, conductivity is obtained only in the thickness direction, and the fused resin maintains adhesion to the adherend even after pressure contact, so no constant pressing load is required. Furthermore, as a matter of course, since the spherical fine conductive metals are embedded in an orderly manner within the empty lattice of the insulating woven fabric, the electrical insulation between the metals remains maintained. Therefore, even if the pattern spacing is made smaller or the resistance is lowered, the anisotropy of the conductivity is easily lost with conventional technology. could be arranged at regular intervals, and this problem could be solved. Furthermore, since the number of spherical fine conductive metal particles per unit area is constant, there is also an advantage that the actual contact area with the conductor on the adherend and the contact resistance are uniform in each pattern.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an example of an anisotropically conductive sheet according to the present invention. After stacking and integrating the insulating resin 3 on the sheet-like insulating woven fabric 2, the spherical fine conductive metal 1 is applied to the sheet-like insulating woven fabric 2 so that the metal 1 is not present on the woven fabric fibers. The sky of woven cloth 2
They were buried neatly within the grid. Thereafter, the insulating resin 3' held on the protective sheet 4' is stacked and integrated to obtain the sheet of the present invention. FIG. 2 is a front view, and FIG. 3 is a cross-sectional view. Here, the sheet-like insulating woven fabric 2 is formed into a sheet shape by woven from insulating fibers such as synthetic fibers such as nylon and polyester or natural fibers such as silk, and the thickness of the woven fabric is 30 to 30 mm. Approximately 150μm is desirable;
The number of weaves is 100 to 500/inch, and the sky at this time is
One side of the lattice must be woven so that the thickness is equal to or greater than the thickness of the woven fabric. For this purpose, an existing mesh such as a screen printing mesh can be used. The fine conductive metal 1 needs to be spherical. In other words, in the case of fibrous metal, for example, when it is embedded in a woven fabric sheet, it adheres not only within the empty lattice but also through the spaces above and below the woven fabric fibers and between the lattices, causing the insulation of the original empty lattice to deteriorate. This results in a loss of information and significantly impairs manufacturing workability. Therefore, in order to avoid the presence of voids in the lattice, the particle size should be between 0.7 and 0.7 to the thickness of the woven fabric.
2.0 times is desirable, and a range of about 20 to 300 μm exhibits good performance. It is desirable to embed one metal in each empty lattice of the woven fabric, but there is no problem in terms of performance even if several metals are embedded so that the thickness is greater than the thickness of the woven fabric. The materials used include gold, silver, copper,
A conductive material such as a single metal such as aluminum, an alloy such as solder, or a metal such as aluminum whose surface is coated with silver can be used. Next, the edge resins 3 and 3' are adhesives or dots made of various synthetic resins and synthetic rubbers, such as urethane rubber, acrylic adhesives, or polyester hot melt adhesives with release properties. It can be easily formed on a protective sheet by printing, brushing, roll coating, spraying, etc., and has a thickness of approximately 5 to 50 ml.
It is desirable that the thickness be about 50 μm. Furthermore, it is also possible to apply the coating directly to the woven fabric in a similar manner and integrate it, instead of applying it to the protective sheet as shown in FIGS. 4 and 5.

When not using it, peel off the sheet protecting one insulating resin, position it on the adherend, and then press it lightly. Next, peel off the other protective sheet, then apply another adherend and press lightly to avoid shifting the position. After that, connect the conductive connections.
If pressure welding or heat pressure welding is carried out at 1.5 to 4.0 kgf/cm ² , conductivity will be obtained between the two adherends through the fine powder metal, as shown in Figures 6 and 7, and the insulating resin will adhere to the other parts. In order to obtain stable electrical contact resistance, constant pressure contact load is not required.

Example 1 A polyester screen plate mesh with a weave count of 180/inch and a thickness of 75 μm (one side of the empty grid is 95 μm) was coated with an acrylic adhesive with a thickness of 15 μm protected on both sides by a release sheet. The release sheet on one side of the agent was peeled off and pasted together to prevent wrinkles. After turning the mesh side upward, a squeegee is lightly used with a silicone rubber spatula to scatter copper spherical metal particles having an average particle size of 85 μm onto the mesh so that it is buried in the grid. The spherical metal embedded within the grid was fixed within the grid by adhesive applied to the mesh. Excess spherical metal was swept away with a brush. After that, the release sheet on one side of the other acrylic adhesive was peeled off, and the sheet was attached to the mesh sheet to prevent wrinkles, creating an anisotropically conductive sheet.

This was patterned on an epoxy copper foil plate with a conductor width of 1.5 mm at a pitch of 2.5 mm, and one protective sheet of the anisotropic conductive sheet was adjusted in advance so that the contact length was 10 mm with respect to the pattern. After peeling it off and positioning it, I pressed it lightly. Then, I peeled off the other protective sheet. Next, use a copper foil polyester sheet with a conductor width of 1.5 mm at a pitch of 2.5 mm.
The patterned sheet was placed on top of this anisotropic conductive sheet, roughly positioned, and then pressed lightly. Thereafter, they were pressed together at a pressure of 2.5 kgf/cm ² . When the contact electrical resistance of each pattern was measured, it was found to be (1.0±0.02)×10 ⁻² Ω, with little variation and a low resistance value.

Example 2 A polyester hot melt having a softening temperature of 80° C. and being sticky at room temperature was used as the insulating resin. This is used as a pre-treatment to coat the protective sheet with the hot melt melted at 95℃ using the roll coating method.
After coating to a thickness of 12 μm, a protective sheet was temporarily attached to the surface. This protective sheet was peeled off, and an anisotropically conductive sheet was prepared by laminating it on a mesh sheet or the like in the same manner as in Example 1, followed by thermo-pressure welding (2.0 kgf/cm ² ) at 90°C. When the contact electrical resistance of each pattern was measured, a resistance value of (0.8±0.01)×10 ⁻ Ω was obtained.

(Effects of the Invention) As explained above, the anisotropic conductive sheet of the present invention has spherical fine metal powder dispersed within the lattice of the insulating woven fabric sheet so that the thickness is equal to or greater than the thickness of the woven fabric sheet. The anisotropically conductive sheet is characterized in that it is buried and electrically connected to the adherend through the fine powder metal by pressure welding or the like. Because the spherical fine metal powder is buried uniformly inside, the fine metal particles exist at a certain distance and do not come into contact with each other.
The conductive anisotropy of the sheet can be ensured, and low pitch connections, which were previously unstable, have become possible.

(2) Because the spherical fine powder metal is embedded uniformly, the electrical contact resistance per bonding area of each pattern can be maintained constant, unlike sheets of the dispersion type in which the conductive material is unevenly distributed.

(3) Since spherical metal is used as the conductive member, it is easier to embed it uniformly in the empty lattice during manufacturing compared to fibrous metal, and the insulation between the lattices can be ensured, resulting in conductive anisotropy. High reliability.

(4) Since the spherical fine powder metal is buried in the empty grid so that the thickness is equal to or greater than the thickness of the insulating woven fabric sheet, the metal is easily exposed by pressure welding with a low load, and the adherend is The contact area with the material became larger, and the contact resistance value became extremely small.

(5) Because the insulating resin melts and adheres to the adherend in areas other than those where the fine powder metal and the adherend come into contact with each other through pressure welding, etc., there is no need for constant pressure contact load after the mounting process, and there is no conduction resistance. was able to maintain a stable and highly reliable conduction state.

(6) Because conduction occurs through individual spherical fine powder metals, there is no need for precise positioning during mounting, making it possible to improve mounting work efficiency.

It has remarkable effects such as:

[Brief explanation of drawings]

FIG. 1 is a partial perspective sectional view of an anisotropic conductive sheet according to an embodiment of the present invention, FIG. 2 is a front view of the main part of FIG. 1, FIG. 3 is a sectional view of the main part of FIG. The figure is a partial perspective sectional view of an anisotropically conductive sheet when an insulating resin is directly integrated with a woven fabric sheet, FIG. 5 is a sectional view of the main part of FIG. 4, and FIGS. 6 and 7 are according to the invention. FIG. 2 is a cross-sectional view of a main part of the anisotropically conductive sheet in a state where the anisotropic conductive sheet and the adherend are in pressure contact with each other. DESCRIPTION OF SYMBOLS 1... Spherical fine powder metal, 2... Insulating woven fabric sheet, 3, 3'... Insulating resin, 4, 4'... Protective sheet, 5... Wiring board, 6... Conductor.

Claims (1)

[Claims] 1. A structure in which spherical fine conductive metal is embedded in an empty lattice of a sheet-shaped insulating woven fabric, and both ends of the sheet-shaped insulating woven fabric in the thickness direction are covered with an insulating resin. Anisotropic conductive sheet featuring: