JPH0511265A - Anisotropic conductive film - Google Patents

Abstract

PURPOSE:To allow the formation of circuit patterns to a finer pitch by projecting the front ends of acicular metals which are dispersed in paste and are arranged in the same direction as a compression direction from the paste at the time of compressing the paste. CONSTITUTION:Conductive whiskers 2 of the acicular metals added to the paste material 1 which consists of a thermoplastic resin and can be compressed in at least one direction are added at about 15% by weight to the paste material 1. This paste material 1 is screen printed on a substrate 6 to form an anisotropic conductive film 10 and the substrate is placed in a strong magnetic field and is vibrated vertically by using an electromagnet to arrange the conductive whiskers 2 dispersed in a uniform state in the paste material 1 in the direction perpendicular to the substrate 6. Consequently, the conductive whiskers 2 come respectively into contact with the various electrode terminals of a liquid crystal display device when independent external electrodes, for example, the plural electrode terminals of the liquid crystal display device are brought into pressurized contact with the front surface of the anisotropic conductive film. The external electrodes and the circuit patterns 6a of the substrate 6 are thus electrically connected by having anisotropy.

Description

Detailed Description of the Invention

[0001]

This invention relates to an anisotropic conductive film.

[0002]

2. Description of the Related Art Conventionally, for example, an anisotropic conductive film used for joining a substrate and a liquid crystal display device has dispersed metal particles having a diameter of 20 to 40 μm in a thermoplastic resin.

[0003]

For this reason, the pitch of the circuit pattern at the junction is limited by the diameter of the metal particles, so the limit is 200 to 400 μm.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an anisotropic conductive film capable of reducing the pitch of circuit patterns.

[0005]

In order to solve the above problems, the present invention provides a paste compressible in at least one direction and needles dispersed in the paste and aligned in the same direction as the compression direction of the paste. And a needle-shaped metal protruding from the paste when the paste is compressed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
Will be described. FIG. 1 is a diagram showing the composition of the conductive paste. Reference numeral 1 denotes a paste material made of a thermoplastic resin and compressible in at least one direction. Reference numeral 2 is a conductive whisker added to the paste material 1. This conductive whisker 2 has a diameter of 0.2 to 0.5 μm and a length of 10 to 20 μm.
It is a needle-shaped metal, and its weight ratio to paste material 1 is 15
% Is added. 3 is a fine particle made of silica, alumina, or the like. The fine particles 3 are added in an appropriate amount in order to improve the printability and heat resistance of the paste material 1. FIG. 2 is a diagram showing details of the conductive whiskers 2. The conductive whiskers 2 have a ferromagnetic material 4 such as nickel (Ni) as a core material, and a surface thereof is plated with gold (Au) 5.

Next, a method of forming the anisotropic conductive film will be described. FIG. 3 is a diagram illustrating a screen printing method for printing the paste material 1 on the substrate 6. A screen 7 is arranged on the substrate 6. The screen 7 is supported by a frame body 8 and provided with a printing pattern. Then, as shown in FIG. 3, the paste material 1 is printed by moving the squeegee 9 on the screen 7, and the anisotropic conductive film 10 is formed on the circuit pattern 6 a of the substrate 6. FIG. 4 is a diagram showing a state of the anisotropic conductive film 10 immediately after printing. As shown in the figure, the conductive whiskers 2 are dispersed in the paste material 1 in a state in which their directions are non-uniform. In this state,
The conductive whiskers 2 and the circuit pattern 6a are not electrically connected, and the anisotropic conductive film 10 is not yet anisotropic.

Therefore, as shown in FIG. 5, the anisotropic conductive film 10 printed on the substrate 6 by using the electromagnet 11 is placed in a strong magnetic field, and the conductive whiskers dispersed in the paste material 1 in a non-uniform state. Align 2 That is, as shown in FIG.
The electric current is applied to the electromagnet 11 through the lead wire 12 and the substrate 6
A strong magnetic field is generated in the direction perpendicular to
To make the conductive whisker 2 move easily.

As a result, since the conductive whiskers 2 are ferromagnetic, they are aligned in the magnetic field direction, that is, in the direction perpendicular to the substrate 6. Therefore, as shown in FIG. 6, since the conductive whiskers 2 of the anisotropic conductive film 10 are aligned in a uniform state, the anisotropic conductive film 10 is anisotropic in the direction perpendicular to the substrate 6.

As a result, when independent external electrodes, for example, a plurality of electrode terminals in a liquid crystal display device are pressed against the surface of the anisotropic conductive film 10, the conductive whiskers 2 come into contact with various electrode terminals of the liquid crystal display device. , The external electrodes and the circuit pattern 6a of the substrate 6 are electrically connected anisotropically via the conductive whiskers 2. That is, the anisotropic conductive film 10
Conducts in the vertical direction but does not conduct in the horizontal direction, so that the electrode terminals contacting both ends of the conductive whisker 2 are electrically conducted only by the circuit pattern 6a.

In this case, since the diameter of the conductive whiskers 2 is 0.2 to 0.5 μm, the pitch of the circuit patterns 6a can be reduced to 10 to 50 μm.

[0012]

According to the present invention, it is possible to provide an anisotropic conductive film in which the pitch of circuit patterns can be made fine. Therefore,
For example, when conductive whiskers having a diameter of 0.2 to 0.5 μm are used, the circuit pattern pitch can be reduced to 10 to 50 μm.

[Brief description of drawings]

FIG. 1 is a diagram showing a composition of a conductive paste.

FIG. 2 is a diagram showing details of a conductive whisker 2.

FIG. 3 is a diagram showing an operation of printing a paste material 1 on a substrate 6.

FIG. 4 is a diagram showing a state of an anisotropic conductive film 10 immediately after printing.

FIG. 5 is a diagram showing an operation of aligning the conductive whiskers 2.

FIG. 6 is a diagram showing a state of the anisotropic conductive film 10 after being placed in a magnetic field.

[Explanation of reference numerals] 1 ... Paste material 2 ... Conductive whiskers 3 ... Fine particles 4 ... Ferromagnetic material 5 ... Gold plating 6 ... Substrate 10 ... Anisotropic conductive film

Claims (1)

Claim: What is claimed is: 1. A paste comprising: a paste compressible in at least one direction; and needle-like metals dispersed in the paste and aligned in the same direction as the compression direction of the paste. An anisotropic conductive film, characterized in that the tip of the acicular metal protrudes from the paste when compressed.