JPH11339558A - Anisotropic conductive adhesive and conductive connection structure - Google Patents

Abstract

(57) Abstract: Anisotropic conductive adhesive capable of satisfactorily conductively joining a substrate or an electric component or the like on which these electrodes are formed, regardless of the type of electrodes such as soft electrodes and hard electrodes. I will provide a. An anisotropic conductive adhesive comprising hard conductive fine particles having an average particle diameter of 0.3 to 50 µm and soft conductive fine particles larger than the hard conductive fine particles, wherein the hard conductive fine particles Wherein the average particle diameter of the anisotropic conductive adhesive is 0.2 to 0.95 times the average particle diameter of the soft conductive fine particles.

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 used for connecting a substrate or an electric component on which electrodes are formed, and a conductive connection structure using the anisotropic conductive adhesive. .

[0002]

2. Description of the Related Art In electronic products such as a liquid crystal display, a personal computer, and a portable communication device, a so-called anisotropic device is used to electrically connect small electric components such as semiconductor elements to a substrate or to electrically connect the substrates to each other. What is called an electrically conductive material is used. Also,
Among the anisotropic conductive materials, anisotropic conductive adhesives in which conductive fine particles are mixed with a binder resin are widely used.

[0003] As the conductive fine particles used in the anisotropic conductive adhesive, those obtained by plating metal surfaces on organic base particles or inorganic base particles or metal particles have been used. Such conductive fine particles are described in, for example, Japanese Patent Publication No. 6-9677.
No. 1, JP-A-4-36902, JP-A-4-4-2
No. 69720, JP-A-3-257710 and the like.

An anisotropic conductive adhesive formed by mixing such conductive fine particles with a binder resin to form a film or paste is disclosed in, for example, JP-A-63-23188.
9, JP-A-4-259766, JP-A-3-259766
No. 291807 and Japanese Patent Application Laid-Open No. 5-75250.

In the conventional anisotropic conductive adhesive, only one of a soft base and a hard base has been used as a base constituting the conductive fine particles. This is because, when the electrode is a soft electrode such as a gold bump, the conductive fine particles can be made to penetrate the electrode by using a hard base material, thereby ensuring reliability. When a soft material is used for the electrode, if a soft base material is used, the base material is easily broken at the time of pressure bonding, and sufficient reliability may not be obtained in some cases.

On the other hand, ITO (Indium Tin O)
In the case where a hard electrode such as xide) is used, if a soft base material is used, since it is elastically deformed at the time of pressure bonding, a sufficient contact area can be secured without damaging the electrode,
Reliability can be ensured. When a hard base material is used for the hard electrode, the electrode may be damaged at the time of pressure bonding, and conduction failure may occur.

[0007] In recent years, as electronic devices and electronic components have become smaller, wirings on substrates and the like have become finer, and hard electrodes and soft electrodes have often become adjacent to each other. In this case, when the conductive bonding is performed using the conventional anisotropic conductive adhesive, the conductive adhesive to be used for the soft electrode may protrude into the hard electrode, causing a problem such as damaging the electrode.

[0008]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to satisfactorily conductively join a substrate or an electric component or the like on which these electrodes are formed irrespective of the types of electrodes such as soft electrodes and hard electrodes. It is an object of the present invention to provide an anisotropic conductive adhesive capable of forming a conductive film, and a conductive connection structure using the anisotropic conductive adhesive.

[0009]

According to the present invention, there is provided an anisotropic conductive adhesive comprising: hard conductive fine particles having an average particle diameter of 0.3 to 50 μm; and soft conductive fine particles larger than the hard conductive fine particles. Wherein the average particle diameter of the hard conductive fine particles is 0.2 to 0.1 times the average particle diameter of the soft conductive fine particles.
This is an anisotropic conductive adhesive characterized by having a ratio of 95 times. Hereinafter, the present invention will be described in detail.

In the present invention, the average particle size is 0.3 to 50 μm
Is an anisotropic conductive adhesive containing the hard conductive fine particles of the above and soft conductive fine particles larger than the hard conductive fine particles. The hard conductive fine particles and the soft conductive fine particles larger than the hard conductive fine particles are used in the anisotropic conductive adhesive of the present invention for the following reasons. That is, when joining a soft electrode using the anisotropic conductive adhesive, sufficient reliability can be ensured for hard conductive fine particles to bite into the soft electrode, while joining the hard electrode. In this case, the soft conductive fine particles are deformed and can have a sufficient contact area with the hard electrode, so that sufficient reliability can be ensured. Furthermore, because the soft conductive fine particles are larger than the hard conductive fine particles,
Even when a hard electrode is bonded, the hard conductive fine particles do not damage the electrode.

The hard conductive fine particles have an average particle size of 0.3 to 50 μm. When it is less than 0.3 μm,
It becomes difficult for conductive fine particles to contact the electrode surface to be joined,
In some cases, a gap may be formed between the electrodes to cause a contact failure. When the thickness exceeds 50 μm, the electrode is easily brought into contact with an adjacent electrode, and a short circuit easily occurs between the electrodes. More preferably, it is 1 to 7 μm.

The average particle diameter of the hard conductive fine particles is 0.2 to 0.95 times the average particle diameter of the soft conductive fine particles. When the ratio is less than 0.2 times, when the electrodes are joined, the crushed soft conductive fine particles hinder, so that the hard conductive fine particles are less likely to bite into the soft electrode, and 0.95 times.
When the ratio is more than twice, when the hard electrode is joined, the hard electrode is easily damaged by the hard conductive fine particles, so that it is limited to the above range. Preferably, it is 0.3 to 0.9 times, more preferably 0.4 to 0.8 times, and still more preferably 0.5 to 0.7 times.

The material of the hard conductive fine particles is not particularly limited, and examples thereof include metals such as gold, silver, palladium, nickel, copper, tungsten and tin, alloys such as solder, and mixtures of metals. A composite of a ceramic and a metal is exemplified. Examples of the composite of metals include those obtained by plating metal particles, and examples of the composite of ceramic and metal include, for example, those in which a conductive layer is formed by coating the surfaces of ceramic particles. No.

Among these, metals are preferred, and from the viewpoint that the reliability at the time of joining can be improved, those in which noble metal plating is applied to metal particles, particularly those in which gold plating is applied, are more preferable. From the viewpoint of high hardness, it is preferable that nickel particles are used as nuclei and plated with the nickel particles.

The hard conductive fine particles have a CV value of 40%.
The following are preferred. Here, the CV value is the following formula (1); CV value (%) = (σ / Dn) × 100 (1) (where σ represents the standard deviation of the particle diameter, Dn is a number average particle diameter). The standard deviation and the number average particle diameter are numerical values obtained by observing 100 conductive fine particles with an electron microscope. If the CV value exceeds 40%, a large number of hard conductive fine particles larger than the soft conductive fine particles are generated, and the hard electrode may be damaged. More preferably, it is 20% or less.

The hard conductive fine particles preferably have an aspect ratio of 1.3 or less. In the present specification, the aspect ratio is a value obtained by dividing the average major axis of the conductive fine particles obtained by observing 100 conductive fine particles with an electron microscope by the average minor axis. When the aspect ratio exceeds 1.3, when the electrodes are brought into contact with each other through the conductive fine particles, a large number of particles that do not come into contact with the electrodes are generated, and the conductive resistance increases, or a leak phenomenon occurs between adjacent electrodes. It will be easier. More preferably, it is 1.1 or less.

The material of the soft conductive fine particles is not particularly limited, and examples thereof include those having particles made of carbon or a polymer material as nuclei and having a surface covered with a conductive layer. The soft conductive fine particles have a K value of 200 to 80.
It is preferably 0 kgf / mm ² .

Here, the K value is defined by the following equation (2): K value (kgf / mm ² ) = (3 / √2) × F × S ^−3/2 × R ^−1/2. (2) (where F is the load value (kgf) at 20 ° C. and 10% compressive deformation, and S is the 10% compressive displacement (m
m) and R are values represented by a radius (mm).

[0019] When the K value is less than 200 kgf / mm ^2, there is a possibility that the electrode is damaged by the hard conductive particles exceeds 800 kgf / mm ^2, the above conductive fine particles at the time of crimping the electrode to each other In some cases, the electrode cannot be fully contacted.

The soft conductive fine particles have a CV value of 10%.
The following are preferred. If the CV value exceeds 10%, the particle diameters become uneven, so that when the electrodes are brought into contact with each other via the conductive fine particles, the ratio of the particles that do not come into contact with the electrodes becomes large, and the leakage phenomenon between the adjacent electrodes is reduced. More likely to occur. More preferably, it is 5% or less.

The soft conductive fine particles preferably have an aspect ratio of 1.1 or less. When the above aspect ratio is 1.
When the ratio exceeds 1, when the electrodes are brought into contact with each other via the conductive fine particles, a large number of particles that do not come into contact with the electrodes are generated, and the conductive resistance is increased, and a leak phenomenon between adjacent electrodes is likely to occur. More preferably, it is 1.05 or less.

In the present invention, the weight ratio of the soft conductive fine particles to the hard conductive fine particles (soft conductive fine particles / hard conductive fine particles) is preferably 1/3 to 3/1. If the weight ratio is less than 1/3 or exceeds 3/1, sufficient electrical capacity may not be ensured when connecting the electrodes.

The anisotropic conductive adhesive is usually one in which the hard conductive fine particles and the soft conductive fine particles are dispersed in an insulating resin. In the present specification, the anisotropic conductive adhesive refers to a material containing an anisotropic conductive film, an anisotropic conductive paste, and an anisotropic conductive ink.

The binder resin constituting the anisotropic conductive adhesive is not particularly limited. For example, a thermoplastic resin such as an acrylate resin, an ethylene-vinyl acetate resin, a styrene-butadiene block copolymer; a monomer having a glycidyl group And a composition curable by heat or light, such as a curable resin composition obtained by the reaction of a polymer or oligomer with a curing agent such as isocyanate.

The content of the hard conductive fine particles in the anisotropic conductive adhesive is preferably 2 to 50% by weight, and the content of the soft conductive fine particles is preferably 1 to 40% by weight.

The object to be connected by the anisotropic conductive adhesive includes, for example, a substrate having an electrode formed on the surface thereof, and an electric component such as a semiconductor. The substrate is
It is roughly divided into a flexible substrate and a rigid substrate. As the flexible substrate, for example, 50 to 500 μm
Resin sheet having a thickness of Examples of the material of the resin sheet include polyimide, polyamide, polyester, and polysulfone.

The rigid substrates are roughly classified into those made of resin and those made of ceramic. Examples of the above-mentioned resin include glass fiber reinforced epoxy resin, phenol resin, cellulose fiber reinforced phenol resin and the like. Examples of the ceramic material include silicon dioxide, alumina, and glass.

The structure of the substrate is not particularly limited, and may be a single layer. In order to increase the number of electrodes per unit area, for example, a plurality of layers are formed, Accordingly, a multilayer substrate in which these layers are electrically connected to each other may be used.

The electric 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 electrode formed on the surface of the substrate or the electric component is not particularly limited, and examples thereof include a stripe shape, a dot shape, and an arbitrary shape.

As the material of the electrode, for example, gold,
Silver, copper, nickel, palladium, carbon, aluminum, ITO and the like can be mentioned. In order to reduce the contact resistance, an electrode in which gold is further coated on copper, nickel, or the like can be used. The thickness of the electrode is 0.1 to 100.
μm, and the width of the electrode is 1 to 50 μm.
It is preferably 0 μm.

As the bonding method using the anisotropic conductive adhesive, for example, an anisotropic conductive adhesive comprising the anisotropic conductive film is provided on a substrate or an electric component having electrodes formed on the surface. There is a method of arranging, placing an electrode of another substrate or an electric component thereon, heating and pressing. By using a predetermined amount of an anisotropic conductive paste in place of the anisotropic conductive film, a layer of an anisotropic conductive adhesive made of an anisotropic conductive paste can be formed 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. The coating film thickness of the anisotropic conductive adhesive is preferably from 10 to several hundred μm.

The anisotropic conductive adhesive of the present invention has soft conductive fine particles and an average particle diameter of 0.3 to 50 μm, and is 0.2 to 0.2 μm based on the average particle diameter of the soft conductive fine particles. 9
Since it contains hard conductive fine particles having an average particle diameter of 5 times, when bonding a soft electrode, the hard conductive fine particles bite into the soft electrode, and sufficient reliability can be secured. When the hard electrode is joined, the soft conductive fine particles are deformed and come into sufficient contact with the hard electrode, so that sufficient reliability can be ensured. Further, since the soft conductive fine particles are larger than the hard conductive fine particles, the hard conductive fine particles do not damage the electrodes even when bonding the hard electrodes.

Therefore, the anisotropic conductive adhesive of the present invention satisfactorily joins various substrates having electrodes formed on its surface, electric parts such as semiconductors, etc., regardless of the hardness of the formed electrodes. And a leak phenomenon between adjacent electrodes hardly occurs. Further, the current capacity at the time of joining can be increased. The present invention also includes a conductive connection structure in which the electrodes of the substrate or the electric component are connected to each other by using the anisotropic conductive adhesive or the like.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 Soft conductive fine particles obtained by subjecting a crosslinked polystyrene polymer having an average particle diameter of 8 μm, a K value of 350 kgf / mm ² , an aspect ratio of 1.05, and a CV value of 5% to a gold plating of 0.05 μm in thickness were prepared. , Average particle diameter 4 μm, aspect ratio 1.1, CV
Hard conductive fine particles plated with gold on nickel having a value of 20%, so that the content thereof is 5% by weight,
A mixture of an epoxy resin and an acrylic resin was mixed and dispersed in a binder solution dissolved in toluene.

Next, the conductive fine particle dispersion obtained in the above step was applied on a release film to a constant thickness, and toluene was evaporated to prepare an anisotropic conductive film. The film thickness is 15
μm. Next, a glass substrate (ITO electrode: thickness 0.3 μm, wiring width 50 μm, electrode pitch 100 μm,
Gold bump electrode: thickness 3 μm, wiring width 50 μm, electrode pitch 100 μm, width 10 between ITO electrode and gold bump electrode
(0 μm), the same anisotropic conductive film was laminated thereon, and the same glass substrate was overlaid thereon, and heated and pressed to form a conductive connection structure, and the connection resistance value was measured.

As a result, the connection resistance value of this conductive connection structure was sufficiently low, and the line insulation between adjacent electrodes was sufficiently maintained. The cooling / heating cycle at -20 to 100 ° C. was performed 1,000 times, but no particular problem occurred.

Example 2 Average particle size 4 μm, aspect ratio 1.1, CV value 20%
In place of the hard conductive fine particles obtained by plating gold on nickel, the average particle size is 3 μm, the aspect ratio is 1.3, and the CV
A conductive connection structure was prepared in the same manner as in Example 1 except that hard conductive fine particles obtained by applying gold plating to nickel having a value of 20% were used, and the connection state was examined.

As a result, the connection resistance value of the conductive connection structure is higher than that of the conductive connection structure of the first embodiment, although the connection resistance at the soft electrode (gold bump electrode) is higher than that of the conductive connection structure of the first embodiment. And the insulation between lines between adjacent electrodes was sufficiently maintained. The cooling / heating cycle at -20 to 100 ° C. was performed 1,000 times, but no particular problem occurred.

Example 3 Average particle diameter 4 μm, aspect ratio 1.1, CV value 20%
Example 1 was replaced by gold-plated hard conductive fine particles having an average particle size of 7 μm, an aspect ratio of 1.1, and a CV value of 30% instead of the gold-plated hard conductive fine particles of Example 1. A conductive connection structure was prepared in the same manner as described above, and the connection state was examined.

As a result, the connection resistance value of the conductive connection structure is higher than that of the conductive connection structure of the first embodiment, although the connection resistance at the hard electrode (ITO electrode) is higher than that of the conductive connection structure of Example 1. It was low, and the line insulation between adjacent electrodes was sufficiently maintained. The cooling / heating cycle at -20 to 100 ° C. was performed 1,000 times, but no particular problem occurred.

Example 4 Soft conductive fine particles obtained by plating a crosslinked polystyrene polymer having an average particle diameter of 8 μm, a K value of 350 kgf / mm ² , an aspect ratio of 1.05 and a CV value of 5% with a gold plating of 0.05 μm in thickness. Instead, average particle size 8μm, K value 1000kg
Conductive connection in the same manner as in Example 1 except that soft conductive fine particles having a thickness of 0.05 μm applied to a crosslinked acrylonitrile polymer having an f / mm ² , an aspect ratio of 1.1, and a CV value of 10% were used. A structure was manufactured and the connection state was investigated.

As a result, the connection resistance value of this conductive connection structure was higher than that of the conductive connection structure of the first embodiment, although the connection resistance at the hard electrode (ITO electrode) was higher than that of the conductive connection structure of Example 1. It was low, and the line insulation between adjacent electrodes was sufficiently maintained. The cooling / heating cycle at -20 to 100 ° C. was performed 1,000 times, but no particular problem occurred.

Comparative Example 1 The average particle diameter was 4 μm, the aspect ratio was 1.1, and the CV value was 20.
% Of nickel, gold-plated hard conductive fine particles, average particle diameter is 1 μm, aspect ratio 1.5, C
A conductive connection structure was prepared in the same manner as in Example 1, except that hard conductive fine particles obtained by plating gold on nickel having a V value of 20% were used, and the connection state was examined. As a result, the line insulation between the adjacent electrodes was sufficiently maintained, but poor conduction was partially observed in the soft electrodes.

Comparative Example 2 The average particle diameter was 4 μm, the aspect ratio was 1.1, and the CV value was 20.
% Nickel instead of gold-plated hard conductive fine particles, the average particle diameter is 8 μm, the aspect ratio is 1.1, C
A conductive connection structure was prepared and the connection state was examined in the same manner as in Example 1, except that hard conductive fine particles obtained by plating gold on nickel having a V value of 45% were used. As a result, the insulation between lines between adjacent electrodes was sufficiently maintained.
After 1000 cycles of cooling and heating at ~ 100 ° C,
Some conduction failure was observed in the hard electrode.

[0046]

As described above, the anisotropic conductive adhesive of the present invention has the above-mentioned structure, so that a substrate or an electrical component or the like on which these electrodes are formed can be used regardless of the kind of electrodes such as soft electrodes and hard electrodes. Good conductive bonding can be achieved. Further, since the conductive connection structure of the present invention has the above-described configuration, the present invention provides a conductive connection structure having low connection resistance, large current capacity at the time of connection, stable connection, and free from a leak phenomenon. be able to.

Claims (10)

[Claims] 1. An anisotropic conductive adhesive comprising hard conductive fine particles having an average particle diameter of 0.3 to 50 μm and soft conductive fine particles larger than the hard conductive fine particles, wherein the hard conductive fine particles An anisotropic conductive adhesive, wherein the average particle size of the fine particles is 0.2 to 0.95 times the average particle size of the soft conductive fine particles. 2. The hard conductive fine particles have an average particle diameter of 1 to 2.
7 μm, and the average particle size of the hard conductive fine particles is 0.3 to 0.9 of the average particle size of the soft conductive fine particles.
2. The anisotropic conductive adhesive according to claim 1, wherein said adhesive is doubled. 3. The anisotropic conductive material according to claim 1, wherein the hard conductive fine particles have an average particle size of 0.4 to 0.8 times the average particle size of the soft conductive fine particles. adhesive. 4. The anisotropic material according to claim 1, wherein the average particle diameter of the hard conductive fine particles is 0.5 to 0.7 times the average particle diameter of the soft conductive fine particles. Conductive adhesive. 5. The hard conductive fine particles are made of metal, and the soft conductive fine particles have a K value of 200 to 800 kgf / mm.
The anisotropic conductive adhesive according to claim 1, 2, 3 or 4, wherein it is made of ^second material. 6. The hard conductive fine particles have a CV value of 40% or less and an aspect ratio of 1.3 or less, and the soft conductive fine particles have a CV value of 10% or less and an aspect ratio of 1.1 or less. The anisotropic conductive adhesive according to 1, 2, 3, 4, or 5, wherein: 7. The anisotropic conductive adhesive according to claim 1, wherein the hard conductive fine particles and / or the soft conductive fine particles are plated with gold. . 8. The hard conductive fine particles having nickel particles as nuclei.
The anisotropic conductive adhesive according to 5, 6, or 7. 9. The weight ratio of soft conductive fine particles to hard conductive fine particles (soft conductive fine particles / hard conductive fine particles).
Is 1/3 to 3/1, wherein
The anisotropic conductive adhesive according to 2, 3, 4, 5, 6, 7, or 8. 10. An electrode part constituting a substrate or an electric component is connected to each other by the anisotropic conductive adhesive according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9. A conductive connection structure characterized by the above-mentioned.