JPH04174980A - Connecting member for circuit - Google Patents

Abstract

PURPOSE:To achieve highly reliable circuit connection that enables connection of microcircuits by heating both insulative particles and thickness-control particles being harder than the insulative particles, and containing the insulative particles and the thickness-control particles in an insulative adhesive which shows plastic fluidity, the insulative particles comprising conductive particles covered at their surface with a thermoplastic insulative layer. CONSTITUTION:This connecting member comprises insulative particles 1, thickness-control particles 2 and an adhesive 3. The insulative particles 1 have conductive particles 4 substantially covered at their surface with a thermoplastic insulative layer 6. The conductive particles 4 need to show deformation by heating and pressing at the connection of a circuit. As the insulative particles, a macromolecular material such as polystyrene and phenol resin is used as a core 7 and a conductive metal thin layer 5 of Cu, Ni, Au and the like is provided on the surface of the core. A Pb/Sn allay or the like is used as the charged particles 4 showing plastic fluidity by heat. Connection of microcircuits is thus made possible and highly reliable circuit connection is achieved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a connecting member for microcircuits, and more specifically, a connecting member for connecting terminals of integrated circuits, liquid crystal panels, etc. and connecting terminals on a circuit board disposed opposite thereto. The present invention relates to a connecting member for electrically and mechanically connecting.

[Prior Art] As electronic components become smaller and thinner, the circuits used in these components are becoming denser and more precise. The connections of these microcircuits are
Since it is difficult to use conventional solder or rubber connectors, methods using anisotropically conductive adhesives or film-like materials (hereinafter referred to as connection members) have recently come into widespread use.

In this method, for example, a connecting member layer made of an adhesive containing a predetermined amount of a conductive material is provided between opposing circuits, and by applying pressure or heating/pressing means, the electrical connection between the circuits is simultaneously established. Insulation is provided between adjacent circuits, and opposing circuits are bonded and fixed.

The above-mentioned circuit connection members are extremely useful as they are materials for connecting multiple circuits at once, but it is important to improve resolution and long-term connection reliability for connection of fine circuits, which are becoming increasingly high-definition. The demands that come with this are extremely strong. In other words, in the conventional technology, generally 5 wires/mm are used in the circuit (100 wires in the circuit).
μm, 100 μm in insulation), but with the recent miniaturization of circuits, for example, 10 connections/mm (50 μm in insulation) is possible.
In connection with circuits with an insulation width of 50 μm or more, and in bonding applications for IC chips, circuits are becoming increasingly finer, with the connection area of one electrode being 50 μm square and the distance between electrodes being 20 μm, for example.

The basic idea behind making connection members high-resolution so that they can connect such fine circuits is to make the particle size of the conductive material smaller than the insulating part between the circuits in order to ensure insulation from adjacent circuits. The objective is to ensure conductivity at the circuit connection portion by reducing the amount of the conductive material and adjusting the amount added to such an extent that the conductive materials do not come in contact with each other. However, when the particle size of the conductive material is reduced, the surface area increases and the number of particles increases significantly, causing secondary agglomeration of the particles, making it impossible to maintain insulation from adjacent circuits. As the number of conductive materials on the circuit decreases, the number of contact points becomes insufficient and continuity between connected circuits cannot be obtained, making it extremely difficult to increase the resolution of connecting members while maintaining long-term connection reliability. .

As an attempt to enable connection of such fine circuits and improve connection reliability, for example, Japanese Patent Laid-Open No. 63-54
There is a method described in No. 796.

In this method, the surfaces of polymer particles and solder particles are coated with Ni or Cu.
In this method, the electrodes are connected by heating and pressurizing them using microcapsules made of a conductive material such as, the surface of which is further coated with an insulating resin layer.

[Problems to be Solved by the Invention] The method disclosed in Japanese Patent Application Laid-Open No. 68-54796 has good connection reliability because the conductive particles exhibit deformability when heated, increasing the contact area with the connection circuit. However, in order to obtain good reliability, connection conditions must be strictly controlled.

In other words, if the connection conditions such as temperature or pressure are insufficient,
Since the insulating layer on the particle surface is insufficiently removed from the circuit surface, the connection resistance is high, and since the contact between the electrode surface and the particle is incomplete, the connection reliability is also reduced. On the other hand, if the temperature or pressure is excessive, the insulating layer on the particle surface will easily melt over the entire surface, and the effect of forming the insulating layer will no longer be obtained.
Contact with adjacent particles reduces resolution, making it unsuitable for connecting microcircuits. Furthermore, the degree of deformation of the conductive particles varies depending on the connection conditions, resulting in variations in connection reliability, which requires strict management of connection conditions.

Furthermore, since the structural connection between circuits is obtained by melting the insulating layer formed on the surface of the particles, the adhesive strength varies depending on the connection conditions, and since the connection parts are dotted, the adhesive area is insufficient. It had drawbacks such as low adhesive strength and easy deterioration due to stress concentration.

The present invention has been made to solve the above problems,
An object of the present invention is to provide a circuit connecting member that can connect fine circuits and easily and stably connect circuits with excellent long-term connection reliability under a wide range of connection conditions.

[Means for Solving the Problems] The present invention provides insulating particles that are formed by substantially covering the surfaces of conductive particles that exhibit deformability when heated with a thermoplastic insulating layer, and thickness-controlled particles that are harder than the insulating particles. The present invention provides a circuit connecting member characterized in that the above is contained in an insulating adhesive that exhibits plastic fluidity when heated.

The present invention also provides a connection member for a circuit, characterized in that an insulating adhesive contains coated particles in which the surfaces of the thickness control particles are substantially covered with a thermoplastic insulating layer as thickness control particles. It is something to do.

The present invention will be explained in more detail with reference to the drawings.

1 and 2 are schematic cross-sectional views of a film-like connecting member showing an embodiment of the present invention. It is structured as follows.

In the insulating particles 1 according to the present invention, the surfaces of the conductive particles 4 are substantially covered with a thermoplastic insulating layer 6, as shown in FIG. Furthermore, the conductive particles 4 need to exhibit deformability when heated and pressurized during circuit connection. As shown in FIG. 3, insulating particles exhibiting such characteristics include a core material 7 made of a polymer material such as polystyrene, polymethyl methacrylate, phenol resin, or epoxy resin, and conductive Cu, Cu, etc. on the surface thereof. A material having a thin metal layer 5 of Ni, Au, etc. formed thereon is preferably used. The conductive particles 4 that exhibit deformability due to heat (thermal deformable conductive particles) include Pb/S.
Particles made of low melting point metals having a melting point of 250° C. or less, typified by n-alloys, may also be used.

Although the shape of the conductive particles 4 that exhibit deformability upon heating is not particularly limited, spherical particles are preferred because they are easy to handle.

The particle size used is less than that of the insulation of the connection circuit, and is 0.
It is preferable to set it as 1-30 micrometers. Although the particle size distribution may be non-uniform since it is deformed during circuit connection by heating and pressurizing, it is preferable to make the particle size range small since it is easier to obtain a uniform thickness when forming the insulating layer 6.

The conductive particles 4 that exhibit deformability when heated are completely solid bodies,
Any of foams having air bubbles inside, hollow bodies having gas inside, and aggregates having small particles may be used, and these can be used alone or in combination.

For the insulating layer 6, a thermoplastic insulator that exhibits fluidity when heated and pressurized can be used. That is, between the circuits to be connected by heating and pressurizing when connecting the circuit, the insulating layer 6 at the contact area between the conductive particles and the circuit or between the conductive particles flows and is removed from the contact area, so that the connected circuit Conductivity is obtained between the two. A typical material for these insulating layers 6 is a hot melt adhesive. Base polymers for hot melt adhesives that have heat softening properties and melting points are also useful, such as polyethylene, ethylene copolymers, ethylene-vinyl acetate copolymers, polypropylene, ethylene-acrylic acid copolymers, and ethylene-acrylic copolymers. Acid ester copolymer, polyamide, polyester, styrene-isoprene copolymer, styrene-butadiene copolymer, ethylene-propylene copolymer, acrylic ester rubber, polyvinyl acetal, nylon, acrylonitrile-butadiene copolymer, styrene -Butadiene copolymers, phenoxy resins, solid epoxy resins, polyurethanes, etc.

The conditions under which these insulating layers 6 exhibit fluidity by heating and pressurizing are 80 to 250°C and 0.
．． It is preferable that it is 1-100 kg/cm2. 8
If it is less than 0°C, the heat resistance of the circuit connection part will be reduced, which is undesirable, and if it exceeds 250°C, a high temperature will be required during connection, which will cause thermal damage to surrounding connected parts, which is undesirable.

In addition, if the pressure is less than 0.1 kg/cm2, the insulating layer at the contact area between the circuit and the insulating particles or between the insulating particles will not be sufficiently removed, so sufficient conductivity will not be obtained, and if the pressure exceeds 100 kg/cm2 This is not preferable because it causes mechanical damage to connecting parts, etc. For these reasons, the insulation layer should be heated at 90 to 220°C and 1 to 50 kg/cm2.
It is preferable that the material exhibits fluidity at .

Methods for forming these insulating layers 6 on the conductive particles 4 include an electrostatic coating method, a spraying method, a high-speed stirring method, a hot melt coating method, and a solution coating method. These manufacturing methods are described in detail in, for example, ``Fine Particle Design'' by Masumi Koishi, published by Industrial Research Association.

Among the above methods, when the insulating layer 6 is soluble in a general-purpose solvent, the solution coating method is preferred because it can be carried out with simple equipment.

The thickness of the insulating layer 6 is preferably about 0.1 to 5 μm. 0.
If the thickness is less than 1 μm, the insulation properties will be insufficient, and if the thickness exceeds 5 μm, it will be difficult to remove the insulating layer sufficiently, making it difficult to obtain sufficient conductivity.

Next, the thickness control particles 2 will be explained using FIGS. 4 and 5.

The thickness control particles 2 need to be harder than the conductive particles 4 at least under the conditions at the time of circuit connection.

Further, it is preferable that the particles have a narrow particle distribution and a uniform particle size, since this makes it easier to control the connection thickness of the circuit at the connection portion. The thickness control particles control the thickness between the circuits during heating and pressurization.

It is preferable that the particle size of the thickness control particles is smaller than the insulating particles 1 (FIG. 1), but even if the particle size is larger (FIG. 2), it can be applied when the insulating particles are aggregated.

The thickness control particles 2 may be used as they are as shown in FIG. 4, or the surfaces of the thickness control particles 2 may be substantially covered with the thermoplastic insulating layer 6 described above as shown in FIG. Providing an insulating layer is effective for improving insulation when conductive thickness control particles are used, and is also extremely useful for uniformly dispersing the thickness control particles in the adhesive 3.

The thickness control particles 2 are, for example, conductive particles such as nickel or silver, spherical or milled fiber particles such as ceramic, glass, or silica, or insulating particles such as hard resin, either singly or in combination as desired. The amount added is preferably 01 to 15% by volume based on the insulating adhesive, if necessary.

If it is less than 0.1%, the thickness control function will deteriorate, and if it is less than 15% by volume.
If it exceeds this, the adhesive strength to the circuit will decrease.

For the same reason, more preferably 0.5 to 10% by volume
, more preferably 1 to 8% by volume.

In addition, in order to cope with the miniaturization of circuits, it is preferable to use insulating particles having an average particle diameter less than the distance between adjacent circuits.

Here, the average particle diameter used in the present invention is determined by the following formula.

D=Σnd/Σn (1) (In the formula, n indicates the number of particles with a particle size of d. Methods for observing these particle sizes include commonly used electron microscopes, optical microscopes,
Coulter counter, light scattering method, etc. are available, and the present invention uses electron microscopy. Further, in the case of particles having an aspect ratio, d is the major axis. ) A connecting member can be obtained by incorporating the insulating particles 1 and thickness control particles 2 as described above into the insulating adhesive 4.

As the insulating adhesive 3 used in the present invention, it is basically possible to use a formulation that is used for ordinary adhesive sheets exhibiting insulating properties. The composition of adhesives used in ordinary adhesive sheets includes polymers such as synthetic resins and rubbers for imparting cohesive force, as well as tackifiers, tackiness modifiers, crosslinking agents, etc. used as necessary. It consists of anti-aging agents, interfacial strengthening agents, dispersants, etc.

In addition, when a reactive (curing) adhesive such as epoxy resin is used as the basic component of an insulating adhesive, its high cohesive strength at high temperatures provides excellent retention of the bonded area, allowing for highly reliable connections. becomes.

At this time, it is preferable that the adhesive and the insulating layer of the insulating particles 1 be an incompatible combination, and the following can be cited as a guideline for selection for this purpose.

(1) The SP value (solubility parameter: detailed in the Adhesive Handbook, 2nd edition, page 46, edited by the Japan Adhesive Association), which is commonly used as a measure of compatibility, is 1. O
As the above different combinations, polarity differences are provided in the materials. (
2) The thermal melting temperature or thermal softening temperature of the thermoplastic insulating layer of the insulating particles 1 is set to be 10° C. or more higher than that of the adhesive. (3)
For example, the insulating layer may be of a reactive type or a hardening type. These guidelines differ slightly for each material, so individual consideration is required.What is important is that the insulating layer in the insulated circuit portion remains intact (covered) even after the circuit is connected.

Adhesives are ranked in order of flowability when connecting circuits.
Insulating layer> Heat-deformable conductive particles are preferred from the viewpoint of obtaining a highly reliable connection.゛The reason for this is that the adhesive 3 first flows due to heat and pressure applied during circuit connection, and is removed from the surfaces of the insulating particles 1 and the circuit 8 or 9, and then the insulating layer 6 softens and flows. conductive particles 4
This is because contact between each other or the conductive particles and the circuit is obtained, and then the conductive particles 4 are deformed to the particle size of the thickness control particles, so that the conductive particles 4 and the circuit are likely to come into surface contact.

The amount of insulating particles 1 added to the adhesive can be increased because the surface thereof is covered with an insulating layer. In other words, in conventional circuit connection members,
In general, insulation with adjacent circuits has been controlled by adding a small amount of 5% by volume or less, but in the present invention, it is possible to add a large amount, preferably 2 to 50% by volume. Ta.

If the amount added is less than 2% by volume, the number of conductive particles in the microcircuit part is too small, resulting in insufficient connection reliability.
If it exceeds 0% by volume, it will be difficult to mix it into the adhesive. A more preferable addition amount is 5 to 30% by volume.

The composition for the connection member is made into a liquid by dissolving the above-mentioned insulating adhesive in a solvent, dispersing it in a suspension state in a medium, or melting it with heat, and then processing the insulating particles 1 and the thickness control particles in a ball mill or It can be obtained by mixing by conventional dispersion methods, such as by using a stirring device.

Using a composition for a connecting member that is a mixture of the above-mentioned insulating particles and thickness control particles, a connecting member is formed directly on one or both circuits that require connection using means such as screen printing or a roll coater. Alternatively, a film-like connecting member as shown in FIGS. 1 and 2 may be used. At this time, the thickness of the connecting member is either not specified or 1 to 5.
0 μm is preferable. If it is less than 1 μm, it is difficult to obtain sufficient adhesion with the circuit, and if it exceeds 50 μm, heat transfer during connection will be insufficient when the circuit is connected for a short time, and the insulating layer of insulating particles will not be able to flow sufficiently. Therefore, sufficient conductivity cannot be obtained. Therefore, the thickness of the connecting member is 3 to 30 μm.
It is more preferable to set it to m.

The method of using the connecting member of the present invention is, for example, by temporarily attaching a film-like connecting member to a circuit and peeling off the separator if there is one, or by applying the above-mentioned composition for connecting members onto the circuit as necessary. After removing the solvent or dispersion medium according to the requirements, other circuits to be connected may be aligned on that surface and heated and pressed using a hot press, heated rolls, or the like.

FIG. 6 shows a case in which a connection member having the structure shown in FIG. 1 in which the thickness control particles 2 are particles having an insulating layer shown in FIG. FIG. 3 is a schematic cross-sectional view showing a connected state. The adhesive 3 is softened by heat and pressure during circuit connection, and the pressure-deformable conductive particles 4 are deformed to the particle size and thickness of the thickness control particles 2, bringing them into surface contact with the circuit, improving reliability. At this time, if the adhesive 3 softens and flows due to heating and pressure during circuit connection, the insulating layer 6
is also softened and removed from the pressurized area. That is, the circuit section 8-9
This is because the circuit 8 or 9 generally has a certain height compared to the insulating part, and the hardness of the candy is higher and less deformable than the board 10.11 which is the insulating part, etc.
Since it is heated and pressurized preferentially compared to the insulating part, the circuit part 8-
The insulating layer existing between circuits 9 and 9 flows and is removed to the insulating part where the pressure is low, and the conductive particles 4 have no insulating layer between circuits 8 and 9 in the pressurizing direction, and conductivity is obtained. This state is the sixth
As shown in part A of the figure, since lateral contact of the conductive particles is also obtained only within the same circuit area, connection reliability is improved by increasing the number of contact points.

The insulating layer 6 may have only the contact portion with the circuit removed as shown in part B of FIG. 6, and in this case, the insulating layer 6 is adhesively fixed to the circuit surface, resulting in a structure in which individual particles are difficult to move. , which is still effective in improving reliability.

When the above connection structure is achieved, the circuit connection is completed by cooling or hardening reaction of the adhesive 3.

In other words, conductive connection between the circuit connection parts 8 and 9 is possible with the thickness controlled to be equal to the particle size of the thickness control particles 2,
Since the insulating layer 6 is maintained between the insulating parts 8 and 8', a high degree of insulation can be maintained. At this time, circuit 8-
Since the conductive particles are deformed along the line 9, the contact area with the circuit increases and reliability is improved.

[Function] According to the present invention, the amount of deformation of conductive particles that exhibit deformability upon heating can be controlled by the particle size of the thickness control particles, which are harder than the conductive particles at least under the conditions during circuit connection. This makes it possible to control the temperature and pressure at a wider range of time, improving the reliability of the connection.

In other words, the lower limit of the temperature and pressure during connection can be set to the conditions that allow deformation of the conductive particles, and the upper limit of the temperature and pressure of the connection conditions can be set to a high temperature and high pressure within a range that does not adversely affect surrounding members. For example, shortening the curing reaction time of adhesives,
The time required for deforming the conductive particles can be shortened, and as a result, the cost of connection work can be reduced.

Furthermore, since the present invention contains insulating particles and thickness control particles in an insulating adhesive, structural adhesion of circuits can be performed with the adhesive, thereby increasing the effective adhesion area and providing high-strength adhesion. This makes it possible to obtain the desired properties, and there is less stress concentration on the bonded area.

Furthermore, when using thickness-controlled particles whose surface is coated with an insulating layer, the insulating layer flows and is adhesively fixed to the circuit surface, so the thickness-controlled particles and conductive particles are sufficiently fixed to the circuit surface, increasing reliability. further improves. Furthermore, in this case, since the surfaces of the insulating particles and thickness control particles are treated, their dispersibility is improved, and they can be dispersed in the adhesive at a high concentration.

[Effects of the Invention] As detailed above, by using the circuit connecting member of the present invention, it is possible to connect fine circuits and to easily and stably connect circuits with excellent long-term connection reliability under a wide range of connection conditions. Obtainable.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views showing one embodiment of the connecting member according to the present invention, FIG. 3 is a schematic cross-sectional view showing insulating particles according to the present invention, and FIGS. FIG. 6 is a schematic cross-sectional view showing the controlled particles according to the present invention, and FIG. 6 is a schematic cross-sectional view of a circuit connection part using the connecting member according to the present invention. Explanation of symbols 1 Insulating particles 2 Thickness control particles 3 Insulating adhesive 4 Conductive particles 5 Metal thin layer 6.6' Thermoplastic insulating layer 7 Core material 8.8' Upper circuit 9. 9' Lower circuit
10 Upper board 11 Lower board Tsumugi Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. Insulating particles whose surfaces are substantially covered with a thermoplastic insulating layer and which exhibit deformability when heated, and thickness control particles that are harder than the insulating particles are made to plastically flow by heating. 1. A circuit connecting member, characterized in that the circuit connecting member is contained in an insulating adhesive exhibiting properties. 2. Insulating particles that are formed by substantially covering the surfaces of conductive particles that exhibit deformability when heated with a thermoplastic insulating layer; and thicknesses that are formed by substantially covering the surfaces of particles that are harder than the insulating particles with a thermoplastic insulating layer. 1. A circuit connecting member characterized in that control particles are contained in an insulating adhesive that exhibits plastic fluidity when heated.