JP2995244B2 - Anisotropic conductive adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive adhesive.

[0002]

2. Description of the Related Art For example, when conductive connection is performed in a state where connection terminals of one wiring board and connection terminals of another wiring board are opposed to each other, conductive fine particles made of conductive metal or the like are cured by thermosetting. Alternatively, an anisotropic conductive adhesive dispersed in an insulating adhesive made of a photocurable resin may be used. In this case, an anisotropic conductive adhesive is interposed between the connection part including the connection terminal of one wiring board and the connection part including the connection terminal of another wiring board, and is subjected to thermocompression bonding or light irradiation. When crimping is performed, a part of the insulating adhesive in the anisotropic conductive adhesive flows and escapes, so that a part of the conductive fine particles in the anisotropic conductive adhesive is connected to the connection terminal of one wiring board. The connection terminal and the connection terminal of the other wiring board facing each other are brought into contact with each other, whereby the connection terminal of the one wiring board and the connection terminal of the other wiring board facing each other are conductively connected, and When the insulating adhesive interposed between the conductive fine particles is cured, the connection portion including the connection terminal of one wiring board and the connection portion including the connection terminal of another wiring substrate are bonded. In other words, such an anisotropic conductive adhesive has conductivity in the thickness direction but has insulation in the surface direction in a used state.

[0003]

However, in such a conventional anisotropic conductive adhesive, when the conductive fine particles are dispersed in the insulating adhesive, the conductive fine particles are generally dispersed in the insulating adhesive. Although it is kneaded after mixing, it has a property that the conductive fine particles adhere to each other and easily aggregate, so that it is difficult to uniformly disperse the conductive fine particles in the insulating adhesive, and the conductive fine particles in the insulating adhesive are used. In this case, there is a problem that a difference occurs in the dispersion density of the connection terminals, resulting in a connection failure between the connection terminals facing each other and a short circuit between the connection terminals adjacent to each other. For example, as shown in FIG. 5, a connection terminal 2 of one wiring board 1 and a connection terminal 4 of another wiring board 3 are formed by dispersing conductive fine particles 5 in an insulating adhesive 6. When conducting conductive connection via the adhesive 7,
As shown on the left side of the figure, when the dispersion density of the conductive fine particles 5 in the insulating adhesive 6 is too small and no conductive fine particles 5 exist between the connection terminals 2 and 4 facing each other,
A connection failure occurs between the connection terminals 2 and 4 facing each other.
As shown on the right side of the drawing, when the conductive fine particles 5 in the insulating adhesive 6 have too high a dispersion density and the conductive fine particles 5 adhere and bead together, the adjacent connection terminals 2 and 4 A short circuit will occur between them. An object of the present invention is to provide an anisotropic conductive adhesive capable of making the dispersion density of conductive fine particles in an insulating adhesive uniform.

[0004]

According to the present invention, a large number of particles each having a surface of conductive fine particles coated with an insulating adhesive are arranged in a plane.

[0005]

According to the present invention, a conductive particle formed by arranging a large number of particles, each having a surface coated with an insulating adhesive on a surface, is connected to a connection portion including a connection terminal of one wiring board and another connection portion. When interposed between the connection part including the connection terminal of the wiring board and press-bonding while applying heat or light, a part of the insulating adhesive coated on the surface of the conductive fine particles flows. Even if it escapes, the conductive fine particles are held at almost the same position, and therefore, the dispersion density of the conductive fine particles in the insulating adhesive after pressure bonding can be made uniform.

[0006]

FIG. 1 shows an anisotropic conductive adhesive according to one embodiment of the present invention. This anisotropic conductive adhesive 1
Reference numeral 1 denotes a structure in which a number of particles obtained by coating the surface of conductive fine particles 12 with an insulating adhesive 13 are continuously arranged and adhered to the upper surface of a base film 14 made of resin. Among these, the conductive fine particles 12 are formed of fine particles made of a conductive metal, or those obtained by coating a conductive metal thin film on the surface of resin fine particles by plating or vapor deposition. The insulating adhesive 13 is made of a thermosetting or photocurable epoxy or acrylic resin. As a method of coating the surface of the conductive fine particles 12 with the insulating adhesive 13, a resin for forming the insulating adhesive 13 is atomized, and the conductive fine particles 12 pass through the mist-like resin. There is a method in which the surface is coated with a resin, and when the insulating adhesive 13 is formed of a resin having plating properties, there is also a method in which the film is formed by electroplating or chemical plating. Conductive fine particles 12
As a method of continuously arranging and adhering a number of particles formed by coating the surface of the base film 14 with the insulating adhesive 13 on the long base film 14, the particles are mixed into a liquid, and this is mixed with the base film 14. There is a method in which the liquid is evaporated on the upper surface and then dried to evaporate the liquid. As this liquid,
When the insulating adhesive 13 is made of an epoxy resin, a thinner such as toluene is used. When the insulating adhesive 13 is made of an acrylic resin, normal hexane or tetrahydrofuran is used.

Next, FIG. 2 shows a case where the connection terminals of one wiring board and the connection terminals of another wiring board are conductively connected to each other while using the anisotropic conductive adhesive 11 to face each other.
This will be described with reference to FIG. First, as shown in FIG. 2, the surface of the conductive fine particles 12 in the anisotropic conductive adhesive 11 is coated with the insulating adhesive 13 on the upper surface of the connection portion including the connection terminal 22 of one wiring board 21. The surface on which a large number of particles are exposed is placed, and temporarily press-bonded to temporarily fix the insulating adhesive 13 on the upper surface of the connection terminal 22 of one wiring board 21. Next, the base film 14 is coated with the insulating adhesive 1.
Knife-shaped member (not shown) as required from the surface of 3
It peels off using etc. In this case, the base film 14 after peeling may be wound around a roll.

When the base film 14 is peeled off, as shown in FIG.
3 is temporarily fixed to the upper surface of the connection terminal 22 of one wiring board 21 in a state where only a large number of particles coated with 3 are arranged in a plane. Next, the lower surface of the connection portion including the connection terminal 24 of the other wiring substrate 23 is positioned and placed on the upper surface of the particles which are arranged and temporarily fixed in a plane. Then, when thermocompression bonding or pressure bonding is performed while applying light, as shown in FIG. 4, a part of the insulating adhesive 13 coated on the surface of the conductive fine particles 12 flows and escapes, and A part of the conductive fine particles 12 is one wiring board 21
And the connection terminal 22 of one wiring board 21 and the connection terminal of another wiring board 23 facing each other. 24 are electrically conductively connected to each other, and each of the insulating adhesives 1 coated on the surfaces of the adjacent conductive fine particles 12.
The connection part including the connection terminal 22 of one wiring board 21 and the connection part including the connection terminal 24 of the other wiring board 23 are bonded by curing after the flow 3 is integrated.

By the way, even if a part of the insulating adhesive 13 coated on the surface of the conductive fine particles 12 flows and escapes, the conductive fine particles 12 are held at almost the same position. The dispersion density of the conductive fine particles 12 therein can be made uniform. As a result, at least one conductive fine particle 12 can be interposed between the opposed connection terminals 22 and 24, so that a connection failure can be prevented from occurring between the opposed connection terminals 22 and 24, In addition, the conductive fine particles 12 can be prevented from adhering to the beads in a daisy chain so that the conductive fine particles 12 do not aggregate, and thus a short circuit between the adjacent connection terminals 22 and 24 can be prevented. Is improved. The wiring boards 21 and 23 may be flexible boards made of resin or the like, or may be hard boards made of glass or ceramic.

[0010]

As described above, according to the present invention, since a large number of particles formed by coating the surface of the conductive fine particles with the insulating adhesive are arranged in a plane, the surface of the conductive fine particles is coated. Even if a portion of the insulating adhesive flows and escapes, the conductive fine particles can be held at almost the same position, so that the dispersion density of the conductive fine particles in the insulating adhesive is uniform. Therefore, the reliability of the anisotropic conductive connection can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an anisotropic conductive adhesive according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state where the anisotropic conductive adhesive is placed on the upper surface of a connection portion including a connection terminal of one wiring board.

FIG. 3 is a cross-sectional view showing a state in which only a base film of the anisotropic conductive adhesive is peeled off and a connection portion including a connection terminal of another wiring board is placed on the upper surface thereof.

FIG. 4 is a cross-sectional view showing a state in which connection terminals of one wiring board and connection terminals of another wiring board are conductively connected using the anisotropic conductive adhesive.

FIG. 5 is a cross-sectional view illustrating a problem of a conventional anisotropic conductive adhesive.

[Explanation of symbols]

 Reference Signs List 11 anisotropic conductive adhesive 12 conductive fine particles 13 insulating adhesive 14 base film

Claims (2)

(57) [Claims] 1. An anisotropic conductive adhesive comprising a large number of particles formed by coating a surface of conductive fine particles with an insulating adhesive on a surface. 2. The anisotropic conductive adhesive according to claim 1, wherein said particles are arranged on a base film.