JPS5858766B2 - Method for manufacturing anisotropic conductive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a sheet having conductivity only in the thickness direction.
The present invention relates to a method of manufacturing any anisotropically conductive sheet.

A thin sheet that is electrically conductive only in the thickness direction and electrically insulated in the direction crossing that direction is called an anisotropically conductive sheet, and is used for example in electronic desk calculators, electronic cameras, electronic It is useful as a material for interconnecting circuit elements housed in extremely limited space, such as in digital wristwatches.

FIG. 1 schematically shows the anisotropic conductive sheet as described above.

In FIG. 1, an anisotropic conductive sheet 1 includes a sheet-like matrix 2 made of a material having electrically insulating properties, and a large number of linear conductors 3 of approximately equal length oriented in the thickness direction of this matrix 2. have.

As is clear, this linear conductor 3 acts to conduct current only in the thickness direction of the matrix 2.

For use as a connecting material between the circuit elements, the second
As shown in the figure, insert this between the circuit elements 4 and 4.
Apply some clamping pressure to secure.

By this clamping and fixing, the opposing terminals 5, 5 between the circuit elements 4, 4 are connected to each other.

Such an anisotropic conductive sheet is generally manufactured by the following steps.

That is, A. Cutting a magnetic filamentary conductor to create short linear conductors of approximately equal length.

B. Dispersing the linear conductor in a matrix liquid having electrically insulating properties.

C6 This mixed liquid is filled between 2,000 sides with an interval equal to the length of the linear conductor, and a uniform magnetic field is applied in the thickness direction to the mixed liquid held in a sheet shape like this. Then, the linear conductor is oriented in the thickness direction of the sheet-like mixed liquid.

D. Solidifying the matrix liquid in a state where the linear conductors are oriented.

However, in anisotropic conductive sheets created using this method, the ends of the linear conductors are often incompletely exposed from the sheet surface, and are often covered with a thin film of the matrix fraction. As a result, (1) contact resistance is high and unstable.

(2) The clamping pressure necessary for continuity is dog.

(3) When the temperature rises, the ends of the linear conductors sink into the matrix by the amount of thermal expansion of the matrix, resulting in disadvantages such as poor connection.

After the orientation is completed (the distance between these two planes is narrower than the length of the linear conductor, and the matrix is solidified with the conductor end completely reaching the sheet surface), it is useful as an improvement method. However, the end portions are still insufficiently exposed, and a new problem arises in that the linear conductors undergo buckling deformation within the sheet.

This invention was obtained as a result of a thorough study from the perspective of how to fundamentally solve the above-mentioned drawbacks, and it has achieved electrical conductivity close to the theoretical value with very light clamping pressure. The present invention provides a method for producing an excellent anisotropically conductive sheet whose conductivity does not decrease even when the temperature is increased.

Next, this invention will be explained using the drawings.

FIG. 3 is a diagram schematically showing a cross-sectional view of the anisotropically conductive sheet of the present invention.

In FIG. 3, an anisotropically conductive sheet 1 has a sheet-like matrix 2 made of a material having electrically insulating properties and a large number of linear conductors 3 arranged in the thickness direction of this matrix 2. There is.

The length of the linear conductor 3 is greater than the thickness of the sheet made of the matrix 2, and both end portions thereof protrude beyond the sheet surface.

The anisotropic conductive sheet as shown in FIG. 3 is manufactured by the following steps.

That is, A. Cutting a magnetic filamentary conductor to create short linear conductors of approximately equal length.

B. Dispersing the linear conductor in a matrix liquid having electrically insulating properties.

C. This mixture is filled between two opposing planes, the surfaces of which are in contact with the mixture of the matrix and the linear body, which are made of an inert soft film, and the mixture is maintained in a sheet-like form. do.

At this time, the thickness of the mixed liquid layer is set to be equal to or greater than the length of the linear body.

D. Effect of magnetic field (this causes the magnetic linear conductors to be oriented in the thickness direction of the sheet.

Thereafter, while maintaining this orientation, the interplanar spacing is gradually narrowed until the interplanar spacing becomes smaller than the length of the linear conductor.

By this operation, the end portion of the linear body is exposed from the Mar-IJ wax layer, and the tip is inserted into the soft coating.

E. Solidify the matrix in this state.

The characteristic feature of the above operations is that the matrix is solidified with the tip of the linear conductor stuck into the wall surface of the container made of soft material.

In the above embodiments, the matrix material must be a material with electrically insulating properties.

Such materials include polyester resins, epoxy resins, urethane resins, polystyrene resins, polyethylene resins, polyamide resins, ABS resins, silicone resins, thermosets and thermoplastics, and virtually any other material. Contains various synthetic resins.

In addition, the matrix material has sufficient fluidity to perform the above-mentioned dispersion and orientation operations of the linear conductor at a temperature below the Curie point of the linear conductor, and can maintain a solidified state at room temperature. It is necessary because it is like that.

"Solidification" here includes chemical reaction hardening and cooling and solidification of materials that were molten at relatively high temperatures.

Furthermore, the matrix material is preferably an elastomer.

This is because elastomers can be used as an anisotropically conductive sheet as explained in Figure 2 above. shall be.

Therefore, connection failure will not occur. Such elastomers are typified by, for example, silicone resins such as silicone rubber, which are obtained as liquid monomers or prepolymers at room temperature, and are polymerized and solidified at relatively low temperatures, and urethane resins.

It is desirable that the linear conductor has both magnetic and conductive properties at the same time, such as iron, nickel, cobalt metals, or alloys containing these metals as main components.

However, the surface of a non-magnetic material such as a copper wire, an aluminum wire, carbon fiber, or glass fiber may be plated with a magnetic metal such as nickel.

Further, the outermost layer of the linear conductor (eg, gold or silver may be plated) to provide chemical stability against oxidation.

One of the features of the conductive sheet according to the present invention is that plating with an expensive metal such as gold can be applied only to the exposed parts.

Since the anisotropically conductive sheet of the present invention is used as an electrical connection material, it is desirable that the electrical resistance of the linear conductor is low.

However, the degree of magnetism need only be sufficient to effect said orientation in the thickness direction of the matrix.

The linear conductor is added to the matrix liquid in an amount of about 0.01 to 5.0% by volume, preferably about 0.05 to 1.0% by volume.

The surface that comes into contact with the mixed liquid (the coating to be applied here should be inert and will not react with or adhere to the matrix).

The required rheological properties and thickness will vary depending on the temperature at which the above operation is performed, the thickness, length, rigidity, etc. of the linear body, but the linear body will not buckle during the operation. It is necessary that the soft body has enough plastic viscoelasticity to penetrate into the film to a depth of at least 1 μm or more.

Particularly suitable are various elastomers such as polybutadiene rubber, nitrile butadiene rubber, styrene butadiene rubber, etc., and polyethylene which softens at relatively low temperatures.

These soft films are usually used by coating or adhering onto a surface made of a hard material, but they can also be used by simply superimposing a film-like film on a surface of a hard material.

As described above, the product of the present invention can provide complete conductivity because the conductor protrudes from the sheet surface.
Because there is a gap between the conductor tip and the sheet surface, even when the sheet is fixed to a circuit electrode or a board using an insulating adhesive, the conductivity is not hindered by the adhesive. There is.

Example 1 A thin steel wire with a diameter of 12μ was cut to have an average length of 0.49
A large number of short linear conductors with a standard deviation of M length of 0.01 mm were obtained.

The surface of this linear conductor was electrolessly plated with nickel to a thickness of 0.6μ, and gold was electrolessly plated thereon to a thickness of O, OSμ.

The thus obtained linear conductor was added to a transparent low-temperature curing silicone rubber stock solution with a specific gravity of 1.05 (1.0% by weight) and stirred under vacuum to obtain a mixed solution.

Two composite films obtained by coating a 100 μm thick polyester film with nitrile butadiene rubber to a thickness of 30 μm were placed facing each other with a donut-shaped aluminum spacer of 0.47 mm thickness in between, with the rubber film on the inside. The above liquid mixture was injected into the space surrounded by the spacer and the film in a determined amount so that the average thickness of the liquid mixture layer was 0.60 mm.

A pair of upper and lower flat molds was placed in the gap of the solenoid coil with a gap to generate a uniform magnetic field perpendicular to the space between the upper and lower molds, and the molds were heated to 60°C. The mixed liquid, which was heated and held in a sheet form by the above-mentioned film, was set on the lower mold surface.

The mold surface spacing is set to 1. Set to Qffllll, 3,000
At the same time as generating a Gaussian magnetic field, 0.08111M
The mold was closed at a speed of /1 mtn.

After the mold was closed by the spacer, this state was maintained for 40 minutes, the mold was opened, and the cured sheet was taken out.

Further, this was heated in an open air at 150° C. for 15 minutes to completely cure it, and then the composite film on the surface was peeled off to obtain an anisotropic conductive sheet 1.

An anisotropically conductive sheet 2 for comparison was created by performing exactly the same operation as above except for using a polyester film without a rubber film.

Table 1 shows the comparison results of the characteristics of the two types of anisotropically conductive sheets thus obtained.

Sheet 1 is clearly superior, and the effect of making the ends of the linear conductors protrude from the sheet surface is remarkable.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway schematic perspective view schematically showing a conventional anisotropically conductive sheet, and FIG. 2 is a partially cutaway schematic perspective view of a conventional anisotropically conductive sheet shown in FIG. This shows how it is used as a connecting material. FIG. 3 is a cross-sectional view of the anisotropically conductive sheet of the present invention, schematically showing how the linear conductors protrude from the surface of the matrix sheet. Explanation of symbols: 1: anisotropic conductive sheet, 2: matrix, 3: linear conductor, 4: electric circuit element, 5: terminal of electric circuit element.

Claims (1)

[Claims] 1. A large number of magnetic linear conductors having approximately equal lengths,
ζ mixture in a matrix liquid with electrically insulating properties,
The mixed liquid is dispersed, the surface is covered with an inactive soft film, and the mixed liquid is filled between two flat surfaces maintained at a distance equal to or greater than the length of the magnetic linear body, and held in a sheet form, and then subjected to the action of a magnetic field. The magnetic wire is oriented in the thickness direction of the sheet, and while maintaining that orientation, the interplanar spacing is narrowed until both ends of the wire are invaginated into the soft film, and then the ζ matrix is solidified. A sheet made of an electrically insulating material has a large number of linear conductors slightly longer than the thickness of the sheet oriented in the thickness direction, and these linear conductors (both ends of which protrude from both sides of the sheet) A method for manufacturing an anisotropically conductive sheet.