JPH11126516A - Anisotropic conductive adhesive and conductive connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesive having low connection resistance and giving high current capacity and stable connection when connected, causing no leakage phenomenon and to provide a conductive connection structure. SOLUTION: This anisotropic conductive adhesive contains conductive fine particles and an insulating particles. The conductive fine particles have an average particle size of 0.3-50 μm and the insulating particles have an average particle size 0.6-1 times of the conductive fine particles and the CV value of the conductive fine particles and the insulating fine particles is 15% or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an anisotropic conductive adhesive used for connection between fine electrodes and a conductive connection structure.

[0002]

2. Description of the Related Art Anisotropic conductive materials include liquid crystal displays,
2. Description of the Related Art In electronic products such as personal computers and portable communication devices, small electronic components such as semiconductor elements are used to electrically connect substrates and to electrically connect substrates.

As such an anisotropic conductive material, a material obtained by mixing conductive fine particles with a binder resin is used. As the conductive fine particles, those obtained by applying metal plating to the surface of organic base particles or inorganic base particles have been used. As the conductive fine particles, for example, Japanese Patent Publication No. 6-96871, Japanese Patent Application Laid-Open No. 4-36902,
JP-A-4-269720, JP-A-3-25771
No. 0 is disclosed.

As an anisotropic conductive adhesive material obtained by mixing such conductive fine particles with a binder resin to form a film or paste, for example, JP-A-63-231
889, JP-A-4-259766, JP-A-3-291807, and JP-A-5-75250.

The conventional anisotropic conductive material has a problem that the current capacity at the time of connection is small since an electrically insulating material is used as a base material of the conductive fine particles.

In particular, in recent years, as electronic devices and electronic components have been reduced in size, wirings on substrates and the like have become finer, and the electrical resistance of connection portions tends to increase. Furthermore, recently developed devices for plasma display applications and the like may be of a large current drive type, and are required to handle large currents. In order to solve the problem of the current capacity, there is a method of increasing the concentration of the conductive particles. However, when the concentration is increased, there is a problem that a leak easily occurs between adjacent electrodes.

As a method for solving this problem, a technique of covering the surface of the conductive fine particles with an insulating material and destroying the insulating material on the contact surface with the electrode at the time of connection, or a method of dense and coarse conductive fine particles. And the like are proposed. However, these techniques are not often used in practice because their production methods are very complicated and their productivity is low.

[0008]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide an anisotropic conductive adhesive having a low connection resistance, a large current capacity at the time of connection, a stable connection, and no leakage phenomenon. It is intended to provide a structure.

[0009]

The present invention relates to an anisotropic conductive adhesive comprising conductive fine particles and insulating particles, wherein the conductive fine particles have an average particle size of 0.3 to 50 μm,
The insulating particles have an average particle size of 0.6 to 1 times the average particle size of the conductive fine particles, and the CV values of the conductive fine particles and the insulating particles are 15% or less. Conductive adhesive.

In this specification, the anisotropic conductive adhesive includes an anisotropic conductive film, an anisotropic conductive paste, and an anisotropic conductive ink. The anisotropic conductive adhesive of the present invention comprises conductive fine particles and insulating particles.

The conductive fine particles used in the present invention are not particularly restricted but include, for example, gold, silver, palladium,
Metal particles such as nickel, copper, tungsten, tin, and solder, simple substances such as carbon, mixtures, composites, alloys, and the like. Further, these conductive fine particles are used as a core material, or a core material made of a polymer such as non-conductive glass, ceramic, plastic or the like is coated with a conductive layer made of the above-mentioned material. You may. Among them, those having polymer microspheres or glass beads as a nucleus are preferable from the viewpoint that a material having a small CV value to be described later is obtained, and those obtained by coating a noble metal with plating or the like from the viewpoint of high reliability are preferable. . More preferably, gold particles are plated on polymer microspheres.

The insulating particles used in the present invention are not particularly limited as long as they are usually used as insulating particles, and include, for example, polymers such as glass, ceramic and plastic. Above all, polymer microspheres and glass beads are preferred in that they have a small CV value, which will be described later, and polymer microspheres are more preferably used, since they have a small K value, which will be described later. Can be

The conductive fine particles have an average particle diameter of 0.3 to 0.3.
50 μm. When the average particle size is less than 0.3 μm,
When the conductive fine particles do not come into contact with the electrode surface to be joined, a gap is formed between the electrodes, and a contact failure occurs.
Since the conductive fine particles are large, the conductive fine particles come into contact with adjacent electrodes and short-circuit occurs between the electrodes. Preferably, it is 1 to 10 μm.

The average particle size of the insulating particles is 0.6 to 1 times the average particle size of the conductive fine particles. If it is less than 0.6 times, the insulating particles are smaller than the conductive fine particles,
The contact between the conductive fine particles cannot be sufficiently prevented, and there is a possibility that a leak may occur between adjacent electrodes. Leakage between the electrodes, which is the target, cannot be prevented. When the average particle size exceeds 1 time, the insulating particles are larger than the conductive fine particles, so that the conductive fine particles cannot contact the electrode, and conduction cannot be achieved. Therefore, it is limited to the above range. Preferably, the average particle size is 0.9 to 1 times the average particle size of the conductive fine particles. The insulating particles preferably have a K value at 20 ° C. smaller than the K value of the conductive fine particles. More preferably, it is 90% or less of the K value of the conductive fine particles.

In the present specification, the K value is defined by the following equation: K = (3 / √2)） ^FS -3 / 2 ・ R- ^{1 / 2} (where F is 10% compression of ^microspheres ) Represents a load value (kgf) in deformation, S represents a compression displacement (mm), and R
Represents the radius (mm) of the microsphere. ). The K value represents the hardness of a sphere universally and quantitatively, and by using the K value, it is possible to quantitatively and uniquely represent a suitable hardness of the conductive fine particles and the insulating particles. Become.

When the K value of the insulating particles is equal to or larger than the K value of the conductive fine particles, the insulating particles prevent the conductive fine particles from sufficiently contacting the electrode during press-fitting, and the conduction resistance tends to increase.

The CV value of the conductive fine particles and the CV value of the insulating particles are 15% or less. In the present specification, the CV value is represented by the following formula: CV = (σ / Dn) × 100 (σ represents the standard deviation of the particle diameter, and Dn represents the number average particle diameter). .

If the conductive fine particles have a CV value of more than 15%, the particle diameters become uneven, so that when the electrodes are brought into contact with each other via the conductive fine particles, particles that do not come into contact are generated.
Leakage between adjacent electrodes is likely to occur, and when the particle size is not uniform, a large particle size prevents the conductive fine particles from sufficiently contacting the electrode, and a small particle size Since the effect is not achieved, it is limited to the above range.

The average particle diameter and CV value of the conductive fine particles and the insulating particles can be obtained by observing 100 arbitrary particles with an electron microscope.

The total occupied volume of the conductive fine particles in the anisotropic conductive adhesive of the present invention is preferably 3 to 30% by volume. When the content of the conductive fine particles is less than 3% by volume, the electric resistance at the time of connection increases, and when it exceeds 30% by volume, the adhesiveness is poor.

In the present invention, the total volume of the insulating particles in the anisotropic conductive adhesive is preferably larger than the total volume of the conductive fine particles. If the total volume occupied by the insulating particles is less than the total volume occupied by the conductive fine particles, a sufficient effect cannot be obtained. More preferably, it is 100% by volume or more.

According to the above-mentioned method for producing an anisotropic conductive adhesive, it is only necessary to mix existing conductive fine particles and insulating particles.
It is easy and has high productivity, and does not require a complicated and low-productivity process of covering the surface of the conductive fine particles with an insulating material or providing a dense portion and a rough portion of the conductive fine particles.

When the conductive fine particles in the anisotropic conductive adhesive of the present invention are suppressed while being sandwiched between a plurality of electrodes, a current flows from one electrode to the other electrode via the conductive fine particles. However, since leakage between adjacent electrodes is prevented by the presence of the insulating particles, the concentration of the conductive fine particles can be increased, thereby reducing the connection resistance,
The problem of the current capacity can be solved.

The method for electrically connecting two electrodes facing each other using the anisotropic conductive adhesive of the present invention is not particularly limited, and the components are previously blended to form an anisotropic conductive adhesive. And a method in which the binder resin and the conductive fine particles and the insulating particles are separately used.

There are two modes in which the respective components are previously blended and used as an anisotropic conductive adhesive, a method of using the anisotropic conductive paste and a method of using the anisotropic conductive film.

The above-mentioned anisotropic conductive paste is used in the form of a paste by mixing conductive fine particles, insulating particles, a binder resin and a solvent. The anisotropic conductive film, conductive fine particles, insulating particles and a binder resin are mixed,
It is used after being formed into a film. In this case, the film thickness is preferably 10 to several hundred μm.

The binder resin is not particularly restricted but includes, for example, thermoplastic resins such as acrylate resins, ethylene-vinyl acetate resins and styrene-butadiene block copolymers; monomers and oligomers having glycidyl groups and curing agents such as isocyanates. And a composition curable by heat or light, such as a curable composition.

The connection object to which the anisotropic conductive adhesive of the present invention is used includes a substrate, a component such as a semiconductor, and the like. Electrodes are formed on these surfaces, respectively. The above substrate is roughly classified into a flexible substrate and a rigid substrate. The flexible substrate is not particularly limited,
A resin sheet having a thickness of 50 to 500 μm is used, and the resin sheet is not particularly limited, and examples thereof include polyimide, polyamide, polyester, and polysulfone.

The rigid substrate is divided into a resin substrate and a ceramic substrate. The resin is not particularly limited, and examples thereof include a glass fiber reinforced epoxy resin, a phenol resin, and a cellulose fiber reinforced phenol resin. The ceramic is not particularly limited, and examples thereof include silicon dioxide and alumina.

As the structure of the substrate, a single-layer structure may be used. In order to increase the number of electrodes per unit area, a plurality of layers are formed by means such as through-hole formation. Alternatively, a multi-layer substrate for making electrical connection with each other may be used.

The above components are not particularly limited, and include, for example, active components such as semiconductors such as transistors, diodes, ICs, and LSIs; and passive components such as resistors, capacitors, and crystal oscillators.

The shape of the electrodes formed on the surface of the substrate and the component is not particularly limited, and examples thereof include stripes, dots, and arbitrary shapes. The material of the electrode is not particularly limited, and examples thereof include gold, silver, copper, nickel, palladium, carbon, aluminum, and ITO. In order to reduce the contact resistance, a material obtained by further coating gold on copper, nickel or the like can be used. The thickness of the electrode is preferably 0.1 to 100 μm, and the width of the electrode is preferably 1 to 500 μm.

As a method for joining the anisotropic conductive adhesive of the present invention to the above-mentioned substrate, the above-mentioned parts, etc., for example, there are the following methods. After an anisotropic conductive film using conductive fine particles is placed on a substrate or component having electrodes formed on the surface, a substrate or component having the other electrode surface is placed, and heated and pressed. Instead of using an anisotropic conductive film, a predetermined amount of conductive paste using conductive fine particles can be used by printing means such as screen printing or a dispenser. For the above-mentioned heating and pressurizing, a crimping machine equipped with a heater, a bonding machine or the like is used.

It is also possible to use a method that does not use the above-mentioned anisotropic conductive film or anisotropic conductive paste. For example, after injecting a liquid binder into a gap between two electrode portions bonded together via conductive fine particles, A curing method or the like can be used.

The joined body of substrates or components obtained as described above is referred to as a conductive connection structure in this specification. Thus, the conductive connection structure using the anisotropic conductive adhesive of the present invention is also one of the present invention.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 Average particle size 8 μm, K value 350 kgf / mm ² , CV value 8
% Of a crosslinked polystyrene polymer having a mean particle size of 0.95 times that of the conductive fine particles, a K value of 2/3, and a CV value of 5%. The polymer was mixed and dispersed in a binder solution obtained by dissolving a mixture of an epoxy resin and an acrylic resin in toluene. Next, a conductive fine particle dispersion solution is applied to a fixed thickness on a release film, and toluene is evaporated,
An anisotropic conductive film was prepared. The film thickness was 30 μm, the conductive fine particles were 7% by volume, and the insulating particles were twice as concentrated.

Glass-epoxy copper-clad substrate (thickness 1.6)
mm, a wiring width of 40 μm, and an electrode pitch of 80 μm). On this, a polyimide film substrate having a thickness of 80 μm (thickness 30 μm, wiring width 40 μm)
m, electrode pitch 80 μm) at 150 ° C, 2
Heating and pressing were performed for a minute to produce a conductive bonding structure.

The connection resistance value of this conductive connection structure is 0.0
At 3Ω, the connection resistance between adjacent electrodes was 1 × 10 ⁹ or more, and the line insulation was sufficiently maintained. In addition, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 20% by volume. The value was sufficiently low at 0.008Ω. The results are shown in Table 1.

Example 2 A conductive connection structure was prepared in the same manner as in Example 1 except that a crosslinked polystyrene polymer having an average particle diameter 0.7 times that of the conductive fine particles was used as the insulating particles. And
The same evaluation was performed. The connection resistance value of this conductive connection structure is 0.03Ω, and the connection resistance between adjacent electrodes is 1 ×
It was 10 ⁹ or more, and the line insulation was sufficiently maintained. In addition, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 17% by volume. The value was sufficiently low at 0.011Ω. The results are shown in Table 1.

Example 3 A conductive connection structure was prepared in the same manner as in Example 1, except that a crosslinked polystyrene polymer having a K value 1.4 times that of the conductive fine particles was used as the insulating particles. The same evaluation was performed. The connection resistance value of this conductive connection structure is
0.037Ω, the connection resistance between adjacent electrodes is 1 × 1
⁰⁹ or more, and the line insulation was sufficiently maintained. In addition, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 20% by volume. The value was sufficiently low at 0.011Ω. The results are shown in Table 1.

Example 4 In Example 1, the conductive fine particles had an average particle size of 4 μm.
m, a K value of 450 kgf / mm ² , a CV value of 5%, a CV value of 10% as insulating particles, and a cross-linked polystyrene polymer having a concentration 1.5 times that of the conductive fine particles. Produced a conductive connection structure in the same manner as in Example 1, and performed the same evaluation. The connection resistance value of this conductive connection structure was 0.03Ω, the connection resistance between adjacent electrodes was 1 × 10 ⁹ or more, and the line insulation was sufficiently maintained. In addition, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 19% by volume.
The connection resistance value at that time was sufficiently low at 0.009Ω.
The results are shown in Table 1.

Comparative Example 1 A conductive connection structure was prepared in the same manner as in Example 1 except that no insulating particles were used, and the same evaluation was performed. The connection resistance value of this conductive connection structure was 0.03Ω, the connection resistance between adjacent electrodes was 1 × 10 ⁹ or more, and the line insulation was sufficiently maintained. However, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, leakage occurred between the electrodes when the concentration of the conductive fine particles was 10% by volume. Was inferior to 0.02Ω. The results are shown in Table 1.

Comparative Example 2 A conductive connection structure was prepared in the same manner as in Example 1, except that a crosslinked polystyrene polymer having an average particle diameter 1.1 times that of the conductive fine particles was used as the insulating particles. And
When the same evaluation was performed, a conduction failure occurred partially in the conductive connection structure. The results are shown in Table 1.

Comparative Example 3 A conductive connection structure was produced in the same manner as in Example 1 except that a crosslinked polystyrene polymer having an average particle diameter 0.2 times that of the conductive fine particles was used as the insulating particles. And
The same evaluation was performed. The connection resistance value of this conductive connection structure is 0.03Ω, and the connection resistance between adjacent electrodes is 1 ×
It was 10 ⁹ or more, and the line insulation was sufficiently maintained. However, when the concentrations of the conductive fine particles and the insulating particles in the anisotropic conductive film were increased at the same ratio, a leak occurred between the electrodes when the concentration of the conductive fine particles was 11% by volume. Was inferior to 0.018Ω. The results are shown in Table 1.

Comparative Example 4 A conductive connection structure was prepared in the same manner as in Example 1 except that conductive fine particles having an average particle diameter of 200 μm were used, and the same evaluation was performed. A short circuit occurred between adjacent electrodes of the structure. Table 1 shows the results
It was shown to.

Comparative Example 5 A conductive connection structure was prepared in the same manner as in Example 1 except that insulating particles having an average particle size of 0.2 μm or less and conductive fine particles obtained by plating the insulating particles with gold were used. It was manufactured and the same evaluation was performed. However, even when the concentration of the conductive fine particles was increased, a portion where a connection failure occurred occurred, and thus the test could not be performed well. The results are shown in Table 1.

Comparative Example 6 A conductive connection structure was produced in the same manner as in Example 1 except that conductive fine particles having a CV value of 20% were used, and the same evaluation was performed. The connection resistance between the electrodes was 1 × 10 ⁹ or more, and although the line insulation was sufficiently maintained, the connection resistance was 0.06Ω, which was higher than that of the present invention. When the concentration of the conductive fine particles and the concentration of the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 18% by volume. The resistance value was 0.02, which was inferior to that of the present invention.

Comparative Example 7 A conductive connection structure was prepared and evaluated in the same manner as in Example 1 except that insulating particles having a CV value of 20% were used. The connection resistance between them was 1 × 10 ⁹ or more, and although the line insulation was sufficiently maintained, the connection resistance was 0.06Ω, which was higher than that of the present invention. When the concentration of the conductive fine particles and the concentration of the insulating particles in the anisotropic conductive film were increased at the same ratio, no leak occurred between the electrodes until the concentration of the conductive fine particles reached 18% by volume. The resistance value was 0.02, which was inferior to that of the present invention.

[0050]

[Table 1]

[0051]

Since the present invention has the above-described structure, the anisotropic conductive adhesive and the conductive connection structure which have a low connection resistance, a large current capacity at the time of connection, a stable connection and do not cause a leak phenomenon. Body can be provided.

Claims (4)

[Claims] 1. An anisotropic conductive adhesive comprising conductive fine particles and insulating particles, wherein said conductive fine particles have an average particle size of 0.3 to 50 μm, and said insulating particles have an average particle size of Is 0.6 to 1 times the average particle size of the conductive fine particles,
CV values of the conductive fine particles and the insulating particles are 15%
Anisotropic conductive adhesive characterized by the following. 2. The insulating particles have an average particle size of 0.9 to 1 times the average particle size of the conductive fine particles, have a K value of 90% or less of the K value of the conductive fine particles, and have an anisotropic conductive particle. 2. The anisotropic conductive adhesive according to claim 1, wherein the total occupied volume in the adhesive is 20% or more of the total occupied volume of the conductive fine particles. 3. The conductive fine particles have an average particle size of 1 to 10 μm.
m, and the total occupied volume in the anisotropic conductive adhesive is 3
The anisotropic conductive adhesive according to claim 1 or 2, wherein the content is less than 30% by volume, and is smaller than the total volume occupied by the insulating particles. 4. A conductive connection structure comprising the anisotropic conductive adhesive according to claim 1, 2 or 3.