JPH1125760A - Anisotropic conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive film for surely and easily connecting electrodes to be connected one with the other on a substrate surface by breaking oxide films on surfaces of the electrodes to be connected. SOLUTION: Two kinds of particles, metal particles 2 having a particle diameter of 2 to 15 μm and fine metal particles 3 having a particle diameter of 0.01 to 0.05 μm are used as conductive particles in this film, and these are mixed together and dispersed in an adhesive agent 4. When the film is interposed between electrodes to be connected on a substrate and put to pressure- attachment, the fine metal particles 3 break on oxide film on surfaces of the electrodes, and electrical connection between the upper and lower electrode to be connected is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive film, and more particularly, to an anisotropic conductive film, which exhibits electrical conductivity between two substrates facing each other, while showing electrical conductivity between circuits and electrodes on the same substrate. The present invention relates to an anisotropic conductive film having an insulating property.

[0002]

2. Description of the Related Art An anisotropic conductive film (hereinafter, referred to as ACF) is a device in which a circuit or an electrode is formed on the surface of a thin plate such as a printed wiring board. It is a material developed for the purpose of electrical connection. As shown in the cross-sectional view of FIG. 5, the adhesive 4 containing the conductive particles 11 is applied on the releasable substrate 1 and disclosed in, for example, JP-A-61-55809. .

FIG. 6 is a sectional view showing a case where substrates are connected to each other using an ACF. Referring to FIG. 6, first, the ACF is placed on one of the substrates (the glass substrate 9 in the example of this figure).
Is applied so that the adhesive layer faces the electrode 8 formed on the substrate surface, and the peelable substrate is peeled off. Next, the other substrate (same as above, film 6) is
Is positioned on the electrode 8 on the glass substrate side, placed on the ACF after removing the base material, pressurized and heated and pressed, the adhesive 4 is cured, and the substrates 9 and 6 are bonded together. . At this time, the conductive particles 11 enter between the electrodes 7 and 8 of both substrates, and electrical connection between the substrates 9 and 6 is made. On the other hand, in the horizontal direction in the same substrate, the adjacent electrodes 8 and
Since the gap between the electrodes 8 or between the electrodes 7 is filled with the adhesive layer 4, the insulation is maintained. By using an ACF having conductivity in a direction perpendicular to the paper surface (a direction perpendicular to the substrates 9 and 6) and having an insulating property in a direction horizontal to the substrate surface, a liquid crystal display element or the like can be used. It is possible to connect electrodes with a narrow pitch.

[0004] The conductive particles contained in the ACF have a suitable range of particle diameter and compounding amount depending on the thickness of the ACF itself, the fineness of the electrode or circuit to be connected, and the like. In JP-A-61-55809,
The average particle diameter of the conductive particles in the adhesive 0.01 ~ 50μ
m, and the blending amount is 0.1 to 10% by volume. or,
Japanese Patent Application Laid-Open No. 61-74205 discloses a method of forming a thin film by coating as a paint in order to ensure that vertical conductivity and horizontal insulation are obtained.
Disclosed is an ACF in which two types of conductive particles having a particle size of 0.2 μm or less and a compounding amount of 0.2 to 20% by weight and a conductive particle having a diameter of 1 μm or more and a compounding amount of 10 to 75% by weight are mixed. Is

[0005]

By using the above-mentioned ACF according to the prior art, for example, a substrate having electrodes formed between electrodes (distance between adjacent electrodes in the same substrate) of 30 μm and width of 40 μm is formed. If connected, the particle size is 5
If the thickness is 0 μm, short-circuit failure, in which conductive particles are straddled between adjacent electrodes after compression, is likely to occur. When the blending amount of the conductive particles is 75% by weight as disclosed in JP-A-61-74205, beads of the conductive particles are connected as shown in FIG. Short circuit is likely to occur. Therefore, it is necessary to design the particle size and the amount of the conductive particles to be optimal according to the application.

By the way, ACF is applied to a metal whose surface of the electrode to be connected is easily oxidized, for example, a chromium (Cr) electrode 8 formed on a glass substrate 9 as shown in FIG.
Is applied, the oxide film 10 of several nm on the surface of the Cr electrode is interposed as an insulating film, resulting in poor connection.
The insulating Cr oxide film can be broken by applying a large load during thermocompression bonding. But,
This method does not always provide a sufficient effect when the material of the electrode to be connected is soft.
For example, as shown in FIG. 7B, when the electrode 7 to be connected is an electrode 7 made of Sn or Cu, the conductive particles 11
Bites into the electrode 7 on that side, so that the Cr oxide film 10 cannot be sufficiently broken.

Japanese Patent Laid-Open Publication No. Hei 5-47428 discloses a method of obtaining conduction by breaking an oxide film on an electrode surface by using an anisotropic conductive film in which a conductive portion having a protruding electrode structure is formed in a through-hole portion of a porous insulating film. The technology used is disclosed. The conductive portion of the bump electrode structure is made of an oxidation-resistant metal such as Au or Ni containing high-hardness fine particles such as alumina or silicon carbide. When the conductive part of the anisotropic conductive film having such a structure is interposed between the electrodes of the two substrates to be connected, and pressed by applying ultrasonic waves, the fine particles of high hardness break the natural oxide film on the surface of the electrode, resulting in good contact. Is obtained. However, in this method, since the electrodes are bonded only to the conductive portions of the protruding electrode structure, there are problems that they are weak against stress due to vibration or the like and that the production of the protruding electrode portion is costly.

Accordingly, the present invention provides an ACF for connecting an electronic component, which breaks an oxide film on the surface of an electrode to be connected and connects the electronic component electrodes reliably and easily.
F is provided.

[0009]

According to the present invention, there is provided an anisotropic conductive film comprising a releasable substrate, an adhesive insulating resin film formed on the releasable substrate, and In the anisotropic conductive film comprising conductive particles dispersed in the conductive particles, the conductive particles, the metal particles having a large diameter of 2 to 15 μm, the particle size of 0.01 to 0.05 μm The two types of metal particles are dispersed and mixed in the insulating resin film using small-diameter metal particles.

Alternatively, the conductive particles have a particle size of 2 to 15
Using large-diameter resin particles having a metal surface plated with μm and small-diameter metal particles having a particle size of 0.01 to 0.05 μm,
The large-diameter resin particles and the small-diameter metal particles are dispersed and mixed in the insulating resin film.

Alternatively, the conductive particles may have a particle size of 2 to 15
Using large-diameter ceramic particles having a metal surface plated with μm and small-diameter metal particles having a particle size of 0.01 to 0.05 μm, the insulating between the large-diameter ceramic particles and the small-diameter metal particles is performed. Characterized by being dispersed and mixed in a conductive resin film.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings using examples. FIG. 1 is an ACF sectional view according to a first embodiment of the present invention. Referring to FIG. 1, an ACF according to the present embodiment includes a releasable substrate 1, an epoxy-based adhesive 4 contributing to adhesion, metal particles 2 serving to make an electrical connection, and particles of the metal particles. And metal fine particles 3 having a small diameter. The method of producing the particles is the same as that generally used in the production of powder. The metal particles 2 are produced by a spray hydrothermal method or the like, and the metal fine particles 3 are produced by a plasma jet heating method or the like.

FIG. 2 shows a Cr film formed on a glass substrate 9.
FIG. 3 is a cross-sectional view when an electrode 8 and a Cu electrode 7 formed on a film 6 are connected using the ACF of the present embodiment.
The thickness of the film 6 is 75 μm, and the thickness of the Cu electrode 7 is 18
μm, the Sn plating thickness is 0.2 μm, and the electrode width is 40 μm.
μm. On the other hand, the Cr electrode 8 on the glass substrate has a thickness of 0.2 μm, and has a 5 nm oxide film 10 formed by naturally oxidizing Cr as an electrode base material on the surface thereof. Next, an enlarged view of the portion A circled in FIG. 2 is shown in FIG.
FIG. 3A shows an enlarged view of the portion B shown in FIG. FIG.
Referring to FIG. 3 and FIG. 3, larger metal particles 2 penetrate into Cu electrode 7 formed on film 6. On the other hand, the smaller metal fine particles 3 penetrate into the Cr oxide film 10 on the glass substrate 9 and are in direct contact with the surface of Cr as the electrode base material. As a result, electrical connection between the electrodes is ensured. Such small-diameter metal fine particles 3
It acts to concentrate stress during crimping and break the Cr oxide film. On the other hand, the bonding between the upper and lower substrates is performed using the glass substrate 9-.
The adhesive 4 filled between the films 6 plays the role.

In the present embodiment, first, an epoxy resin and a curing agent, which are the basis of the adhesive, a solvent, metal particles and metal fine particles are mixed at a predetermined ratio, and the mixture is agitated. Dispersed uniformly. Next, this resin is applied on a peelable substrate to a thickness of 10 to 30 μm,
After drying at a temperature of ° C. for several minutes to obtain a sheet-like ACF, it was cut into a width of about 1 mm to 10 mm depending on the use.

Next, ACF is adhered to the surface of the glass substrate 9 on which the Cr electrode is formed, the peelable substrate 1 is peeled off, and the Cu electrode 7 formed on the film 6 is replaced with the electrode 8 on the glass substrate 9 side.
And pressurized and heated and pressed from the film 6 side. At this time, the fine metal particles 3 having a small diameter are
And the metal particles 2.

In the ACF according to the present embodiment, the thickness of the peelable substrate 1 is 50 μm, and the thickness of the adhesive 4 is 15 μm. The average diameter of the conductive particles is 5 μm for the larger metal particles.
m, the smaller metal fine particles have a diameter of 0.03 μm. The mixing ratio is such that the large-diameter metal particles 2 are 1% by weight and the small-diameter metal fine particles 3 are 0.02% by weight, based on the total weight excluding the peelable substrate.

The reason for this mixing ratio is that the metal fine particles 3 are reliably sandwiched between the metal particles 2 and the electrodes 7 and 8 within a range in which short circuit does not occur between the adjacent electrodes 7, 7 or 8, 8 after the pressure bonding. That's why. The reason why the size of the metal particles 2 is set in the range of 2 to 15 μm is to prevent an open between the connected electrodes 7 and 8 and a short circuit failure between adjacent electrodes. If the particle size is smaller than 2 μm, irregularities of about 1 μm on the surface of the Cu electrode 7 cannot be sufficiently absorbed, and the connection becomes unstable, and an open failure occurs. Conversely, if the particle size is 1
If it exceeds 5 μm, depending on the electrode pitch, short-circuit failure occurs between adjacent electrodes when only two or three conductive particles are connected in a daisy chain. Since the fine metal particles 3 having a small diameter are used to concentrate stress, the larger metal particles 2 are used.
Is preferably 1/100 or less. On the other hand, it is necessary to have a size that can break the Cr oxide film 10 having a thickness of several nm, so that the diameter is suitably in the range of 0.01 to 0.05 μm.
Ni, which is a hard material, was used for the metal particles 2 and the metal fine particles 3. The particles may be made of a hard material having conductivity and may be Co, Ti, W or the like.

Next, a second embodiment of the present invention will be described. FIG. 4 is a sectional view of an ACF according to a second embodiment of the present invention. This embodiment is different from the first embodiment in that plastic particles 5 whose surface is metal-plated are used for the conductive particles having a larger diameter. The material of the plating is Ni. The plastic particles are made of polystyrene and have a particle size of 5 μm. The thickness of the plating may be larger than the particle size of the fine metal particles 3,
And

Instead of plastic particles, ceramic particles such as alumina, which are metal-plated, can be used equally. Also in this case, it is appropriate that the particle size is 5 μm and the plating thickness is 0.1 to 0.5 μm. As described above, the large-diameter conductive particles do not necessarily have to be pure metal, and therefore, it is preferable to select one having a low particle manufacturing cost.

[0020]

As described above, the anisotropic conductive film of the present invention uses two kinds of particles, large and small, as the conductive particles.
Each particle size is limited to a specific range.

Thus, according to the present invention, the stress can be concentrated on the small-diameter conductive particles, and the ability to destroy the natural oxide film on the electrodes can be increased. Instead, the electrodes can be reliably connected between the substrates to be connected, and the reliability of the connection can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of an ACF according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view when an electrode on a glass substrate and an electrode on a film are connected in the first embodiment.

FIG. 3 is an enlarged sectional view of a portion A and a portion B shown by circles in FIG. 2;

FIG. 4 is a cross-sectional view of an ACF according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of an example of a conventional ACF.

6 is a cross-sectional view when an electrode on a glass substrate and an electrode on a film are connected using the ACF shown in FIG.

FIG. 7 is a cross-sectional view showing a state in which a short circuit has occurred between adjacent electrodes on the same substrate in an ACF connection structure according to a conventional technique, and a view showing a state in which an open has occurred due to a natural oxide film on the electrode surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Peelable base material 2 Metal particle 3 Metal particle 4 Adhesive 5 Plastic particle 6 Film 7 Cu terminal 8 Cr terminal 9 Glass substrate 10 Oxide film 11 Conductive particle

Claims (3)

[Claims] 1. An anisotropic composition comprising a releasable substrate, an adhesive insulating resin film formed on the releasable substrate, and conductive particles dispersed in the insulating resin film. In the conductive conductive film, the conductive particles, using a large-diameter metal particles having a particle size of 2 to 15 μm and a small-diameter metal particles having a particle size of 0.01 to 0.05 μm, the two types of metal particles Is dispersed and mixed in the insulating resin film. 2. An anisotropic composition comprising a releasable substrate, an adhesive insulating resin film formed on the releasable substrate, and conductive particles dispersed in the insulating resin film. In the conductive film, the conductive particles have a particle diameter of 2 to 15 μm, a large-diameter resin particle having a metal-plated surface, and a particle diameter of 0.01 to 0.0
An anisotropic conductive film, wherein metal particles having a small diameter of 5 μm are used, and the resin particles having a large diameter and the metal particles having a small diameter are dispersed and mixed in the insulating resin film. 3. An anisotropic composition comprising a releasable substrate, an adhesive insulating resin film formed on the releasable substrate, and conductive particles dispersed in the insulating resin film. In the conductive film, the conductive particles have a diameter of 2 to 15 μm, a large-diameter ceramic particle whose surface is metal-plated, and a particle size of 0.01 to
An anisotropic conductive film, wherein said large-diameter ceramic particles and said small-diameter metal particles are dispersed and mixed in said insulating resin film using small-diameter metal particles of 0.05 μm.