JP2748705B2 - Circuit connection members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting member for a fine circuit, and more particularly, to electrically and mechanically connecting a connecting terminal of an integrated circuit, a liquid crystal panel, etc. to a connecting terminal on a circuit board opposed to the connecting terminal. To a connection member for performing the connection.

[0002]

2. Description of the Related Art As electronic components have become smaller and thinner, circuits used for them have become higher in density and higher in definition. Since connection of these microcircuits is difficult with conventional solders or rubber connectors, recently, anisotropic conductive adhesives and film-like materials (hereinafter referred to as connection members) with excellent resolution are frequently used. It has become. In this method, a connecting member layer made of an adhesive containing a predetermined amount of a conductive material is provided between opposing circuits, and a pressurizing or heating pressurizing means is provided. The insulation is provided between the circuits, and the opposing circuits are bonded and fixed.

[0003] The basic idea for increasing the resolution of the connecting member is to make the particle size of the conductive material smaller than that of the insulating portion between the circuits in order to ensure the insulation from the adjacent circuit, and to make the conductive material accordingly. An object is to surely obtain conductivity at a circuit connecting portion while controlling the amount of addition so as not to contact. However, when the particle size of the conductive material is reduced, the particles are secondary-aggregated due to an increase in the surface area and the number of particles are remarkably increased, so that the insulating property with the adjacent circuit cannot be maintained. Since the number of conductive materials on the circuit is reduced, the number of contact points is insufficient and conduction between the connection circuits cannot be obtained, and it has been extremely difficult to achieve high resolution of the connection member while maintaining long-term connection reliability. .

[0004] As an attempt to obtain a connection member which enables connection of such a fine circuit and has excellent connection reliability, we have previously proposed a method described in Japanese Patent Application Laid-Open No. 63-237372. In this method, the conductive particles are composed of particles whose surfaces are covered with a thermoplastic insulating layer having fluidity due to the heat pressure at the time of circuit connection, and an insulating adhesive. In this method, the insulating layer on the surface is softened and flowed by heating and pressurizing at the time of circuit connection, and the coating is removed at the contact portion of the circuit or the particle, thereby providing conductivity between the connected circuits. On the other hand, in the insulated circuit portion, the insulation is obtained because the coating of the insulating layer is kept as it is because pressure is not applied as much as particles between circuits.

[0005] For the above reasons, the conductive particles can be filled into the adhesive at a high concentration, and conduction in a minute connection area can be reliably obtained, so that a high-resolution connection part can be obtained. In addition, the conductive particles are softened and deformed by heating and pressurizing when connecting the circuit, improving the contact area with the circuit and the particles, and have the ability to follow the temperature change of the connecting part. Long-term connection reliability, such as when a high humidity test or a temperature change is included, can be significantly improved.

[0006]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 63-2373
The method disclosed in Japanese Patent No. 72 is an excellent method capable of achieving both high resolution and connection reliability, but has a problem that the insulation between adjacent circuits cannot be stably obtained. It is considered that the reason for this is that the degree of removal of the coating of the thermoplastic insulating layer slightly varies depending on the conditions at the time of circuit connection and the thickness of the insulating layer.

That is, if the heat and pressure during circuit connection are excessive, the formed thermoplastic insulating layer melts and conductive particles come into contact with each other between adjacent circuits, resulting in insufficient insulation. If the heat pressure is insufficient, the insulating properties are good, but the removal of the insulating layer between the circuit surface and the conductive particles is insufficient, and it is considered that the connection resistance is increased. Therefore, in order to obtain a balance between these characteristics, the connection conditions must be strictly controlled, which is not mass-produced.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a heat-deformable conductive particle comprising a core material made of a high-molecular polymer and a conductive metal thin layer substantially coated on the surface thereof. Smaller particle size, harder and less meltable than adhesive under connection conditions
The present invention relates to a circuit connecting member, characterized in that composite particles formed by attaching insulating particles as described above through a binder are dispersed in an adhesive.

Examples of the composite particles according to the present invention will be described below with reference to the drawings. 1 to 5 are schematic sectional views showing composite particles suitable for the present invention.

FIG. 1 shows heat-deformable conductive particles 5 obtained by substantially coating a surface of a polymer core material 1 with a conductive metal thin layer 2.
Shows the composite particles 6 in which the insulating particles 3 are adhered and fixed on the surface of the composite particles 6.

Even if the insulating particles 3 are formed by the interposition of the binder 4 (FIGS. 1 to 3), van der Waals force or electrostatic force is used without using the binder 4 as shown in FIG. Alternatively, a method for immobilization may be used. The insulating particles 3 are shown in FIGS.
Or a multi-layer as shown in FIG. When it exists in multiple layers, it is easy to obtain insulation more stably.

In the case of FIG. 1, since the insulating particles 3 are exposed from the binder 4, a stable insulating arrangement with the other conductive particles 5 can be easily obtained. FIG. 2 shows a structure in which the insulating particles 3 are buried in the binder 4. However, compared to the case where only the binder 4 is used, the insulating particles 3 are present, and the insulating particles 3 are bonded. Binder 4 at the time of connection because it is harder than binder 4
Even if the fluid flows, stable insulating properties can be obtained by the insulating particles 3.

In the case of FIG. 3, the insulating particles 3 are individually (of course, may be a part of aggregated insulating particles) treated with the binder 4 to prevent deterioration of the insulating particles 3. In this case, stable insulation can be obtained. Further, this embodiment has a feature that the insulating particles 3 can be reliably formed on the conductive particles 5.

The above-described typical composite particles can be used in combination of two or more. Hereinafter, the constituent materials will be described. The polymer core material 1 may be any of a solid body, a foam having internal bubbles, a hollow body having a gas inside, an aggregate forming a core material by a collection of small particles, and the like. Can be used. The shape of the polymer core material 1 is preferably substantially spherical, but the shape is not particularly limited.

Examples of the material of the polymer core material 1 include various plastics such as polystyrene and epoxy resin, various rubbers such as styrene-butadiene rubber and silicone rubber, and natural polymers such as starch and cellulose. Crosslinking agents and curing agents as main components, functional group imparting substances,
Various additives such as a coupling agent and an antioxidant can be used.

The conductive metal thin layer 2 is made of various conductive metals, metal oxides, alloys and the like. Examples of metals include Zn, Al, Sb, Au, Ag, Sn, Fe, Cu, Pb, Ni, Pd,
There are Pt and the like, and these can be used alone or in combination.For further special purposes, for example, adjustment of hardness and surface tension and improvement of adhesion, Mo, Mn, Cd,
Other metals such as Si, Ta and Cr and their compounds can be added. Ni, Ag, Au, from conductivity and corrosion resistance
Sn and Cu are preferably used, and they can also be formed as a single layer or multiple layers.

As a method for forming the conductive metal thin layer 2 on the polymer nucleus material 1 by using these, a dry method such as an evaporation method, a sputtering method, an ion plating method, a thermal spraying method, or a plating method is applied. it can. An electroless plating method capable of obtaining a coating layer having a uniform thickness is preferable because of a wet dispersion system. The thickness of the thin metal layer is usually 0.01 to 5μ.
m, preferably 0.05 to 1.0 μm. Here, the thickness includes the metal base layer, if there is one. If the thickness of the coating layer is small, the conductivity is reduced. If the thickness is increased, deformation of the polymer nucleus material at the time of circuit connection is less likely to occur and the contact area with the circuit is reduced, so that connection reliability is reduced.

The particle diameter of the thermally deformable conductive particles 5 formed as described above is preferably 0.5 to 50 μm. When the particle size is less than 0.5 μm, the number of the filled particles increases, and the contact area with the circuit is substantially reduced, so that the adhesion to the circuit is reduced. It is difficult to improve the resolution because it is lost. The particles can exist independently or aggregated in the connecting member.

It is preferable that the diameter of the insulating particles 3 is smaller than that of the thermally deformable conductive particles 5 from the viewpoint of easy fixation and high resolution of the connecting member. The ratio of the average particle diameter of the conductive particles 5 is preferably 1/3 or less, more preferably 1/5 or less. For this reason, the average particle size of the insulating particles 3 is preferably 2 μm or less, more preferably 0.5 μm or less.

The material of the insulating particles 3 is insulating Ti,
Compounds such as oxides, nitrides, and carbonates such as Mg, Zn, Si, Ba, Ca, Al, and Fe; thermoplastics such as nylon, polyacetal, polymethyl methacrylate, and polystyrene; and other epoxy resins and phenolic resins And a thermosetting substance such as a benzoguanamine resin. Among these, metal compounds such as metal oxides and metal nitrides and thermosetting resins are preferable because they have excellent heat resistance of the insulating layer and are excellent in maintaining insulation because they are non-melting at the time of circuit connection. Applicable.

As a method for immobilizing the insulating particles 3 on the heat-deformable conductive particles 5, for example, a granulation method such as a spraying method or a high-speed stirring method can be applied. , Mechano Mill (Okada Seiko), Ong Mill (Hosokawa Micron), High Predication System (Nara Machine), Coatmizer (Freund Sangyo),
It is commercially available under a trade name such as CLAX SYSTEM (Orient Chemical), and any of them can be preferably applied.

The amount of the insulating particles 3 formed on the heat-deformable conductive particles 5 is only required to ensure insulation between adjacent particles. For this purpose, the projected area of the insulating particles 3 on the conductive particles 5 is larger than the surface area of the insulating particles 3. (That is, the projected area of the particle size of the insulating particles) is 1
/ 2 or more.

The binder 4 is formed by converting the insulating particles 3 into the conductive particles 5.
It used to deposited thereon. As a material of the binder 4, a thermoplastic substance having fluidity by heating and pressurizing at the time of circuit connection can be used.
Examples thereof include polyacetal, polymethyl methacrylate, polystyrene, polypropylene, and polyethylene.

The binder 4 must be insulative when it is formed on the outermost layer as shown in FIGS. 2 and 3, but in other cases (FIGS. 1, 4 and 5), it is conductive. Or insulating.

The above composite particles 6 are mixed with an insulating adhesive 7
By dispersing the inside, the connection member of the circuit of the present invention is obtained.

As the insulative adhesive 7 used in the present invention, compounds used for ordinary adhesive sheets showing insulation properties can be basically applied. In particular, heat, light, electron beam, moisture, anaerobic Each of the curable adhesives due to the properties and the like is preferable because it can stably hold the deformation of the conductive particles at the time of circuit connection.

Examples of the main materials of these adhesives include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, acrylate rubber, polyvinyl acetal, acrylonitrile-butadiene copolymer, and styrene-butadiene copolymer. And modified styrene-ethylene-butylene copolymers, phenoxy resins, epoxy resins, polyesters, polyurethanes, and the like, and these can be used alone or in combination of two or more. Additives such as imparting agents, cross-linking agents, antioxidants and coupling agents can also be included as appropriate. Among the above-mentioned adhesives, for example, a so-called curable adhesive such as a combination of a material having a functional group such as a hydroxyl group and an isocyanate having a reactivity with the material, or a combination of an epoxy resin and a latent curing agent. Is preferable because of its good heat resistance. In particular, an epoxy-based adhesive is more preferably applicable to the present application because it is easy to obtain both storage stability and short-time curability.

The addition amount of the composite particles 6 in the adhesive 7 can be filled at a high density because the surface is covered with the insulating layer. That is, in the connection member of the conventional circuit, the addition amount is generally 5% by volume or less to control the insulation with the adjacent circuit by adding a small amount, but in the present invention, the addition amount is as large as 2 to 35% by volume. It has become possible to add to. If it is less than 2% by volume, the number of conductive particles in the fine circuit portion is too small, so that the reliability of the connection is insufficient. If it exceeds 35% by volume, the adhesiveness of the connection circuit is insufficient. The preferred amount is 5 to 25% by volume.

After dissolving the adhesive in a solvent, dispersing it in a suspension in a medium, or melting it by heat, the composite particles are mixed by an ordinary dispersion method such as a ball mill or a stirrer. Thus, a composition for a connection member is obtained.

The composition for a connection member obtained by mixing the above-mentioned composite particles may be used to form a connection member directly on a circuit using screen printing or a roll coater on one or the other circuit requiring connection, or It may be a film-like connecting member. At this time, the thickness of the connection member is not particularly limited, but is preferably 1 to 100 μm. If it is less than 1 μm, it may be difficult to obtain sufficient adhesiveness to the circuit, and if it exceeds 100 μm, when the connection of the circuit is short, heat transfer at the time of connection is insufficient and the insulating particles cannot flow sufficiently. In some cases, sufficient conductivity cannot be obtained.

As a method of using the connecting member according to the present invention, for example, when a separator is provided in a state where a film-like connecting member is temporarily attached to a circuit, it is necessary to peel off the separator or apply the above composition onto the circuit. After removing the solvent and the dispersion medium according to the above conditions, another circuit to be connected may be positioned on the surface, and heated and pressed by a hot press or a heating roll.

The connection state of the circuit terminals by the connection member according to the present invention will be described with reference to FIGS. FIG. 6 shows the composite particles 6 and the adhesive 7 according to the present invention between the circuit terminals 8-8 '.
2 shows a state in which a connecting member is formed. By heating and pressing in the direction of the circuit terminals 8-8 'in the state of FIG.
As described above, the heat-deformable conductive particles 5 are flattened, the contact area with the circuit is increased, and the distance of 8-8 'is reduced. At this time, the insulating particles 3 are removed from the contact surface with the circuit by pressurization and move in the long axis direction of the deformable conductive particles on the low pressure side. Also,
Even if the binder 4 is present, since the binder 4 is thermoplastic, the viscosity is reduced at the time of connection, so that the movement of the insulating particles 3 is not hindered. Therefore, in order of the lowest viscosity before curing at the time of connection,
It is preferable to have a configuration of adhesive <binding layer <conductive particles <insulating particles.

In the state where the insulating particles are moved to the major axis side of the deformable conductive particles, the cohesive force of the adhesive is increased by cooling or the curing reaction of the adhesive, so that the composite particles are fixed. Circuit connection is completed.

The conditions at the time of connection vary depending on the relationship among temperature, pressure and time, but the following conditions can be exemplified.
The heating conditions are 300 ° C. or less (more preferably 250 ° C.).
C. or lower), the pressure conditions are preferably 1 to 100 kgf / cm2 (more preferably 5 to 50 kgf / cm2), and the time is preferably 60 seconds or less. The reason for this is that if the temperature is higher than 300 ° C., thermal damage is likely to occur in the peripheral portion of the connection. If it is less than 1 kgf / cm 2, the elimination of the insulating particles 3 is insufficient. If the time is 60 seconds or longer, the connection workability is reduced.

According to the present invention, the adhesive or binder used by thermal pressure during circuit connection is low viscosity, the insulating particles are pressurized from the contact surface of the terminals and the conductive particles in the circuit terminal portion to be connected And can be fixed with an adhesive in a state where the conductive particles, which are non-contact portions between the terminal with low pressure and the conductive particles, are moved or rotated in the lateral direction by flow or rotation (see FIG. 7).

Therefore, the insulation between adjacent circuits is
With insulating particles that are not easily thermally deformed, or by increasing the density of insulating particles on the major axis surface of the deformable conductive particles, it is possible to obtain reliable insulation.

Therefore, compared with the case where a conventional thermoplastic insulating layer is formed, it is possible to widely apply conditions such as temperature and pressure at the time of connection. Further, the thickness of the surface insulating layer can be easily controlled even during the production of the connection member, and the quality can be improved.

Further, by making the conductive particles thermally deformable, the conductive particles are softened and deformed by heating and pressurizing at the time of circuit connection, so that the contact area between the circuit surface and the conductive particles is increased. Since the thermal expansion coefficient and the elastic modulus of the agent can be approximated, the agent has a follow-up property to the temperature change of the connecting portion, and therefore, a long-term connection stability can be obtained. Even if the contact area with the circuit increases, insulating properties in the lateral direction can be ensured by the insulating particles, and it is possible to cope with a fine circuit.

Furthermore, by setting the insulating adhesive to a curable composition, high-strength connection between electrodes having excellent heat resistance can be achieved, and the deformation of the conductive particles and the arrangement of the insulating particles can be stably maintained. Connection stability is further improved.

[0040]

According to the present invention, it is possible to provide a connection member which can easily achieve electrical connection between circuits and excellent insulation between adjacent circuits under a wide range of connection conditions.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a composite particle suitable for the present invention.

FIG. 2 is a schematic sectional view showing a composite particle suitable for the present invention.

FIG. 3 is a schematic sectional view showing a composite particle suitable for the present invention.

FIG. 4 is a schematic sectional view showing a composite particle suitable for the present invention.

FIG. 5 is a schematic sectional view showing a composite particle suitable for the present invention.

FIG. 6 is a schematic cross-sectional view showing a connection state of a circuit terminal using the connection member according to the present invention.

FIG. 7 is a schematic cross-sectional view showing a connection state of a circuit terminal using the connection member according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 polymer nucleus material 2 conductive metal thin layer 3, 3 ′ insulating particles 4 binder 5 heat-deformable conductive particles 6 composite particles 7 insulating adhesive 8, 8 ′ circuit terminal

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kyohisa Ota 1500 Oji Ogawa, Shimodate City, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (56) References JP-A-4-149273 (JP, A)

Claims (1)

(57) [Claims] 1. A heat-deformable conductive particle having a conductive metal thin layer substantially coated on a core material made of a high-molecular polymer,
Bonding agent with insulating particles that are smaller in size than heat-deformable conductive particles and harder and more non-melting than adhesive under connection conditions
A connection member for a circuit, characterized by dispersing composite particles formed by adhesion through an adhesive in an adhesive.