JPH08148211A - Connection member and structure and method for connecting electrode using the same - Google Patents

Abstract

PURPOSE: To provide connection having high resolution and excellent workability by forming an adhesive layer having electric conductivity in a pressurizing direction in one surface of a thermoplastic film, forming an insulating adhesive layer in the other surface and reducing melting viscosity of both adhesive layers by the thermoplastic film during connecting. CONSTITUTION: An electrically conductive layer 2 constituted of an electrically conductive material and a binder containing electric conductivity in a pressurizing direction is formed in one surface of a thermoplastic film 1. Also, an insulating adhesive layer 3 is formed in the other surface of the film 1 and for both adhesive layers melting viscosity is reduced, at least more than the film 1 during connecting. Thus, the electrically conductive layer and the insulating adhesive layer can separately exist because of the thermoplastic film, the amount of electrically conductive particles flowing out of an electrode is small and connection can be carried out with high resolution and excellent workability.

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 bonding and fixing an electronic component and a circuit board, or circuit boards to each other, and electrically connecting both electrodes, and an electrode connecting structure using the connecting member.・ About connection method.

[0002]

2. Description of the Related Art In recent years, as electronic parts have become smaller and thinner, circuits used therein have become higher in density and higher in definition. Such electronic parts and fine electrodes can be connected by conventional solder or rubber connectors. Since it is difficult to cope with such problems, recently, anisotropic conductive adhesives and film materials (hereinafter,
Connection member) is often used. This connecting member is made of an adhesive containing a conductive material such as conductive particles in a predetermined amount, and the connecting member is provided between the electronic component and the electrode or circuit, and by applying pressure or heating / pressurizing means. The electrodes are electrically connected to each other, and the electrodes formed adjacent to the electrodes are provided with an insulating property so that the electronic component and the circuit are bonded and fixed. The basic idea for increasing the resolution of the above-mentioned connecting member is to make the particle size of the conductive particles smaller than the insulating portion between the adjacent electrodes to ensure the insulating property between the adjacent electrodes, and also to improve the conductive particles. The content of is set to such a degree that the particles do not come into contact with each other, and the particles are surely present on the electrode to obtain conductivity in the connection portion.

[0003]

The above-mentioned conventional method is
If the particle size of the conductive particles is reduced, the particles will undergo secondary aggregation due to the marked increase in the surface area of the particles, and the particles will be connected, making it impossible to maintain the insulation between adjacent electrodes.If the content of the conductive particles is reduced, the particles will be connected. Since the number of conductive particles on the power electrode also decreases, the number of contact points becomes insufficient, and conduction between the connection electrodes cannot be obtained, so it is difficult to improve the resolution of the connection member while maintaining long-term connection reliability. there were. That is, due to the recent remarkable high resolution, that is, the miniaturization of the electrode area and the space between adjacent electrodes (space), the conductive particles on the electrodes flow out between the adjacent electrodes together with the adhesive due to the pressure at the time of connection or the heat and pressure. This has been an obstacle to increasing the resolution of the members.

At this time, if the adhesive has a high viscosity in order to suppress the outflow of the adhesive, the contact between the electrodes and the conductive particles becomes insufficient, making it impossible to connect the electrodes facing each other. On the other hand, when the adhesive has a low viscosity, in addition to the outflow of the conductive particles, bubbles are likely to be included in the space portion, and the connection reliability, particularly the moisture resistance is deteriorated. From this, a conductive particle-containing layer and an insulating adhesive layer are separated into a multi-layered connecting member, and the viscosity at the time of connection is high.
Attempts have been made to retain the conductive particles, but they have not been put into practical use because the contact between the electrodes and the conductive particles is insufficient or the manufacturing method is troublesome.

Further, as a connection member which enables connection of such fine electrodes and circuits and is excellent in connection reliability, there is also a proposal of a connection member having a dense region of conductive particles in a necessary portion in the plane direction. According to this, although it is possible to connect a dot-shaped fine electrode such as a semiconductor chip, there is a drawback that workability is inferior because accurate alignment of the dense region of conductive particles and the dot-shaped electrode is required. The present invention has been made in order to solve the above-mentioned drawbacks, there is little outflow of conductive particles from the electrode, and since it is difficult to include air bubbles in the connection portion, excellent long-term connection reliability, the conductive particles and the electrode (EN) Provided are a high-resolution connecting member excellent in workability because it does not require accurate alignment with the connecting member, and an electrode connecting structure and connecting method using the connecting member.

[0006]

SUMMARY OF THE INVENTION According to the present invention, an adhesive layer made of a conductive material and a binder and having conductivity in the pressing direction is formed on one side of a thermoplastic film, and an insulating layer is formed on the other side of the thermoplastic film. Adhesive layers are formed, and both adhesive layers have a connection member having a melt viscosity lower than that of the thermoplastic film at least at the time of connection, and at least one of the electrode rows facing each other protrudes, and the conductive material of the connection members faces each other. A connection structure of electrodes existing between the electrodes and having a conductive material higher in density than the surroundings of the protruding electrodes, and at least one protruding electrode, and the connecting member is provided between electrode rows facing each other. The method for connecting electrodes, wherein the insulating adhesive layer is arranged so as to be on the protruding electrode side, and is heated and pressed in the vicinity of the thermal transformation point of the thermoplastic film.

The present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a connecting member for explaining an embodiment of the present invention. The connecting member of the present invention is formed of a conductive material and a binder on one surface of a thermoplastic film 1, and a conductive adhesive layer 2 having conductivity in the pressing direction is formed on the thermoplastic film 1.
An insulating adhesive layer 3 is formed on the other side of the above, and both adhesive layers have a melt viscosity lower than that of the thermoplastic film 1 at least at the time of connection. A peelable separator (not shown) may be present on these surfaces in order to prevent unnecessary adhesion and adhesion of dust and the like. 2 and 3 are schematic cross-sectional views of a connecting member for explaining another embodiment of the present invention, in which the thermoplastic film has a multilayer structure (1, 1 '). In FIG. 2, the insulating adhesive layers 3 and 3 ′ are present on the surface, and in FIG. 3, the conductive adhesive layers 2 and 2 ′ are present. As shown in FIGS. 2 and 3, the surface configuration can be arbitrarily selected according to the electrode configuration. Further, the thermoplastic film 1 can also be sequentially formed into two or more layers. FIG. 4 is a schematic cross-sectional view of a connecting member for explaining an embodiment of the present invention, in which the thermoplastic film 1 shares the insulating adhesive layer 3 and is effective in reducing the manufacturing cost.

The thermoplastic film 1 has a thermal transformation point of 50.
Those at ˜350 ° C. are preferred. The thermal transformation point here is
The melting point is used when the melting point is clear, but when the melting point is unclear like a mixture, a temperature with a melt viscosity of 100 poise can be adopted as the transformation point. The reason why the temperature at which the melt viscosity is 100 poise is set as the transformation point is that the viscosity or less is useful as fluidity at the time of connection for contact between the electrode and the conductive material. The reason why the thermal transformation point is preferably 50 to 350 ° C. is to maintain the reliability of the connection body on the low temperature side and to suppress the thermal deterioration of the peripheral materials such as the substrate at the time of electrode connection at the high temperature side. Is. Therefore, the thermal transformation point is preferably 70 to 250 ° C, more preferably 80 to 200 ° C. The thermoplastic film 1 may have adhesiveness with other adhesive layers 2 and 3,
It is preferable because a highly reliable electrode connection structure can be obtained.

Non-limiting examples of thermoplastic films are ethylene vinyl acetate copolymers, polyethylene,
Ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, acrylic ester rubber, polyisobutylene, polyvinyl butyral, acrylonitrile-butadiene copolymer, styrene-butadiene block copolymer, polybutadiene, phenoxy resin, polyester Polymers such as resins, polyurethane resins, silicone rubber, polychloroprene, and rubbers can be used. These may be used alone or in combination of two or more. In these films, tackifier, cross-linking agent,
Various regulators such as an antiaging agent and an interfacial strength improver can also be contained. The thickness of the thermoplastic film may be thin, and considering the usage conditions described later, it is preferable that the height of the protruding electrode or the height of the conductive material, whichever is smaller, is smaller, which means good contact between the electrode and the conductive material. And is preferable.

Conductive adhesive layer 2 having conductivity in the pressing direction
Is a binder 5 containing a conductive material 4 as shown in FIG.
Consists of Here, as the conductive material 4, as shown in FIG.
As in (d), it is preferable that the binder 5 has a small particle diameter equal to or smaller than the thickness of the binder 5. In this case, the thickness of the binder 5 is reduced by applying pressure or heating / pressurizing means to obtain conductivity. Further, as shown in FIGS. 5E to 5G, it may protrude from the surface of the binder 5. When the conductive material 4 has a thickness equal to or smaller than the thickness of the binder 5, the conductive material 4 can be prevented from falling off by the binder 5, and when the conductive material 4 projects from the surface of the binder 5, the conductive material 4 can be electrically connected to the electrode by a simple contact.

The ratio of the conductive material 4 to the binder 5 is
It is preferably about 0.1 to 20% by volume, because conductivity anisotropy is easily obtained. Further, in order to easily obtain conductivity, the thickness of the binder 5 is preferably as thin as possible in the film formation range, preferably 3
It is 0 μm or less, more preferably 20 μm or less. As the conductive material 4, for example, it is preferable to form conductive particles as shown in FIGS. 5E to 5G because it is relatively easy to manufacture. Further, the conductive material 4 may be provided with a through hole in the binder 5 as shown in FIG. 5 (f) and a conductor may be formed by plating, or may be a conductive fiber such as a wire as shown in FIG. 5 (g). .

As the conductive particles, Au, Ag, Pt, N
There are metal particles such as i, Cu, W, Sb, Sn and solder, carbon powder, etc., and these conductive particles are used as a core material, or polymers such as non-conductive glass, ceramics or plastics. It is also possible to cover the core material made of (1) with a conductive layer made of the above material. Further, insulating coated particles obtained by coating a conductive material with an insulating layer, and combined use of conductive particles and insulating particles are also applicable. The particle size is preferably 1 or more, preferably 5 or more on a minute electrode, and small particle size is suitable for securing a large number of particles, 15 μm or less,
It is more preferably 7 μm or less.

Among these conductive particles, those in which a conductive layer is formed on a hot-melt metal such as solder or a polymer core material such as plastic are deformable by heating or pressurization, and are The contact area is increased and the reliability is improved, which is preferable. In particular, when a polymer is used as a core, since it does not exhibit a melting point like solder, it is possible to widely control the softened state at the connection temperature, and it is possible to obtain a connection member that easily copes with variations in thickness and flatness of the electrode. Particularly preferred. Also, for example, Ni,
In the case of hard metal particles such as W or particles having a large number of protrusions on the surface, the conductive particles pierce the electrode or wiring pattern, so that a low connection resistance is obtained even in the presence of an oxide film or a contaminated layer, and the reliability is high. improves.

As the binder 5, a thermoplastic material similar to that described above or a material exhibiting curability by heat or light can be widely applied and preferably has adhesiveness. Since these have excellent heat resistance and moisture resistance after connection, application of a curable material is preferable. Among them, the epoxy adhesive is preferably applicable because it can be cured for a short time, has good workability in connection, and has excellent adhesiveness due to its molecular structure. Epoxy adhesives include, for example, high molecular weight epoxies, solid epoxies and liquid epoxies,
It is general that the main component is epoxy modified with urethane, polyester, acrylic rubber, NBR, nylon or the like, and a curing agent, a catalyst, a coupling agent, a filler and the like are added.

As a method for producing the connecting member of the present invention, for example, a method of laminating the conductive sheet and the adhesive layer 2, or a method of sequentially laminating and coating the sheets can be adopted. Regarding the connection structure of the electrode using the connection member of the present invention and the manufacturing method thereof,
This will be described with reference to FIGS. FIG. 6 shows a structure in which the protruding electrode 12 formed on the substrate 11 and the planar electrode 13 of the substrate 11 'are connected via the connecting member of the present invention. Here, the flat electrode 13 has no unevenness from the surface of the substrate 11 ′, or even if there is unevenness, it is a few μm or less. To exemplify these, the electrodes obtained by the additive method or the thin film method are typical.

FIG. 7 shows the case where the electrodes formed on the substrates 11 and 15 are the protruding electrodes 12 and 12 '. In this case, the structure is such that both surfaces shown in FIG. 2 are connected via the connecting members having the insulating adhesive layers 3 and 3 '. The insulative adhesive layers 3 and 3'cover the surroundings of the protruding electrodes of the protruding electrodes 12 and 12 ', respectively, and are also connected to the respective substrate surfaces 11 and 15. 6 and 7, examples of the substrate 11 include plastic films such as polyimide and polyester, composites such as glass epoxy, semiconductors such as silicone, and inorganic substances such as glass and ceramics. In addition to the above, the protruding electrode 12 can also include various circuits and terminals. 6 and 7
The various electrodes shown by can be applied in any combination.

In FIGS. 6 and 7, the electrodes 1 facing each other are arranged.
2-13, the conductive material 4 exists, and the protruding electrode 12
The conductive material exists in a state in which the density of the conductive material is higher between the electrodes 12 and 13 than the circumference 14, and the electrode rows facing each other are connected to each other. Further, the insulating adhesive layer 3 covers at least the periphery of the protruding electrode 12 of the protruding electrode 12. Electrode 12-1
Between 3 and 3, the thermoplastic film 1 is melted and disappears by heating and pressurizing at the time of connection, but since the pressurization is insufficient between the adjacent electrodes 12-12, the conductive adhesive layer 2 and the insulating adhesive layer It is maintained as a boundary layer with 3. In the electrode connecting method using the connecting member of the present invention, the connecting member is arranged so that the insulating adhesive layer of the connecting member is on the protruding side of the electrode, and is heated and pressed in the vicinity of the thermal transformation point of the thermoplastic film. When the temperature is higher than the vicinity of the thermal transformation point, the conductive adhesive layer 2 and the insulating adhesive layer 3
It becomes difficult to exist as a boundary layer with the electrode 1 when the temperature is low.
It is difficult to melt between 2 and 13 by heating and pressurizing at the time of connection, and it is difficult to obtain conduction. Since the temperature in the vicinity of the thermal transformation point differs depending on the molecular weight and the molecular structure of the adhesive, it is rational to find the optimum point by experiment.

[0018]

The connecting member of the present invention comprises a thermoplastic film, on one side of which a conductive material and a binder are formed, to form an adhesive layer having conductivity in the pressing direction, and an insulating adhesive on the other side of the thermoplastic film. By forming a layer and making both adhesive layers have a melt viscosity at the time of connection lower than that of the thermoplastic film, the conductive adhesive layer and the insulative adhesive layer can be separated by the thermoplastic film. Further, in the electrode connecting method of the present invention, the insulating adhesive layer of the connecting member is arranged between the electrode rows having at least one protruding electrode so that the insulating adhesive layer of the connecting member is on the protruding electrode side. By heating and pressurizing in the vicinity of the thermal transformation point, it becomes possible that the conductive material exists between the electrodes facing each other and the conductive material has a higher density than the surroundings of the protruding electrodes.

Since the viscosity of the adhesive layer can be arbitrarily adjusted,
It is possible to adopt a configuration in which it is difficult for bubbles to be included in the connection portion. Further, since the sheet having conductivity in the pressing direction is present in any portion in the thickness direction of the connecting member, accurate alignment between the conductive particles and the electrode is unnecessary. The adhesive layer can be combined depending on the purpose, for example, in accordance with the material of the electrode substrate, so that the choice of materials is expanded and the connection reliability is also improved. Further, by making one of them soluble or swellable in a solvent, or by giving a difference in heat resistance, it is possible to preferentially separate from one substrate surface, and to provide so-called repairability for reconnection. . In addition, the adhesive layer can be made to stick out of the connection portion to obtain a reinforcing effect and a moistureproof effect by the action of a sealing material.

[0020]

EXAMPLES Next, examples will be described, but the present invention is not limited to these examples. Example 1 (1) Preparation of Thermoplastic Film with Conductive Adhesive Layer Acrylic rubber (glass transition point-10) as matrix
The ratio of the liquid epoxy resin (epoxy equivalent 185) containing a microcapsule type latent curing agent at 20 ° C. is 20 /
80 was obtained to obtain a 30% solution of ethyl acetate. In this solution, Ni / Au was added to polystyrene particles having a particle size of 5 ± 0.2 μm.
5% by volume of conductive particles having a 0.2 / 0.02 μm thick metal coating formed thereon were added and mixed and dispersed. This dispersion is applied to a film (thickness 10 μm) of phenoxy resin (thermoplastic epoxy resin) having a thermal transformation point of 130 ° C. by a roll coater, dried at 110 ° C. for 20 minutes, and matrix thickness 5
A sheet of μm was obtained.

(2) Formation of Insulating Adhesive Layer and Preparation of Connection Member A sheet of acrylic rubber and liquid epoxy resin containing a microcapsule type latent curing agent at a ratio of 10/90, containing no conductive particles and having a thickness of 15 μm Was formed on the back surface of the conductive adhesive layer of (1) in the same manner as in (1) to obtain a connecting member corresponding to FIG. (3) Connection A two-layer FPC circuit board (circuit pitch 100 μm, parallel circuit electrodes with electrode width 50 μm) having a copper circuit 18 μm high on a polyimide film, and 1.1 mm thick on glass Connection was made with a flat electrode having a 0.2 μm (ITO, surface resistance 20 Ω / □) indium oxide thin film circuit. First, the electrode side (FPC
Circuit board), and the connecting member is 1.5mm
Placed in the width. After that, the ITO circuit board and the upper and lower circuits were aligned and connected at 160 ° C., 20 kgf / mm ² and 15 seconds.

(4) Evaluation When a cross section of this connector was polished and observed with a microscope,
The connection structure was equivalent to that in FIG. The space was free of air bubbles and the particles were spherical, but the particles were compression-molded on the electrode and held in contact with the upper and lower electrodes. By applying heat and pressure in the vicinity of the thermal transformation point of the thermoplastic film, the conductive material could exist between the electrodes facing each other, and the conductive material could exist in a higher density than the surroundings of the protruding electrodes. When the electrodes facing each other were evaluated as a connection resistance and the adjacent electrodes were evaluated as an insulation resistance, the connection resistance was 1 Ω or less and the insulation resistance was 10 ⁸ Ω or more, which were 85 ° C. and 85% RH1.
After the treatment for 000 hours, there was almost no change and good long-term reliability was shown. In this example, since the adhesive force of the flat electrode on the glass side was relatively lower than that on the FPC side, when the film was forcibly peeled from the glass side, the interface was peeled off neatly and the subsequent cleaning was easy. . This is suitable for imparting repairability to the connection of liquid crystal panels that are often used in the same configuration at present.

Example 2 The same as Example 1, but the insulating adhesive layer of Example 1 was laminated on the conductive adhesive layer of the connecting member of Example 1 to form a connecting member corresponding to FIG. Then, the FPC circuit boards of Example 1 were connected to each other. This embodiment has a configuration corresponding to FIG.
Although the electrodes had a large height, the electrodes were not displaced and showed good connection characteristics. The particles were deformed by compression and held in contact with the upper and lower electrodes. There were no bubbles mixed between adjacent electrodes, and good long-term reliability was shown.

Example 3 The same as Example 1, except that the FPC was replaced with an IC chip (2 × 10 mm, height 0.5 mm, 200 gold electrodes called bumps around the sides of 50 μm square and 20 μm height). Formation) was used. The ITO electrode on the glass side was changed to correspond to the size of the bump electrode of the IC chip. The conductive material of the conductive adhesive layer is conductive particles having an average particle size of 3 μm, the addition amount is 1% by volume, and the thickness of the matrix is 10 μm.
And the sheet. The connection body had a structure corresponding to that shown in FIG. 6, but showed good connection characteristics. In this example, the bump was mushroom-shaped and had a top portion, but the particles were compressed and deformed and held in contact with the upper and lower electrodes. There was no air bubble mixing between adjacent bumps, showing good long-term reliability. The degree of deformation of the conductive particles was different depending on the relative distance between the electrodes, and some of the conductive particles bite into the bumps.

[0025]

According to the present invention, since the functions of the conductive adhesive layer which is a conductive region and the insulating adhesive layer which is an insulating region are formed separately, a connection with high resolution and excellent connection reliability is obtained. Provided are a member and an electrode connecting structure and connecting method using the connecting member.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a connecting member of the present invention.

FIG. 2 is a schematic sectional view of a connecting member of the present invention.

FIG. 3 is a schematic sectional view of a connecting member of the present invention.

FIG. 4 is a schematic sectional view of a connecting member of the present invention.

FIG. 5 is a schematic sectional view showing a configuration of a conductive adhesive layer in the connection member of the present invention.

FIG. 6 is a schematic sectional view showing an electrode connection structure using the connection member of the present invention.

FIG. 7 is a schematic sectional view showing an electrode connection structure using the connection member of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermoplastic film, 2 ... Conductive adhesive layer, 3 ... Insulating adhesive layer, 4 ... Conductive material, 5 ... Binder, 11, 11 '...
Substrate, 12 ... Projection electrode, 13 ... Planar electrode, 14 ... Surrounding,
15 ... Substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Nakajima 1150 Gozamiya, Shimodate City, Ibaraki Prefecture Inside the Yuki Plant of Hitachi Chemical Co., Ltd. (72) Inventor Hiroshi Matsuoka 1150 Gogomiya, Shimodate City, Ibaraki Hitachi Seiko Co., Ltd. Yuki factory

Claims (3)

[Claims] 1. A thermoplastic film comprising a conductive material and a binder formed on one surface of the thermoplastic film to form an adhesive layer having conductivity in the pressurizing direction, and an thermoplastic adhesive film formed on the other surface of the insulating adhesive layer, A connecting member in which both adhesive layers have a melt viscosity lower than that of the thermoplastic film at least at the time of connection. 2. At least one of the electrode rows facing each other projects, the conductive material of the connecting member according to claim 1 exists between the electrodes facing each other, and the density of the conductive material is higher than that of the surroundings of the projecting electrodes. Connection structure of electrodes that exist in the state. 3. At least one has a protruding electrode,
The insulating adhesive layer of the connecting member according to claim 1 is arranged between the electrode rows facing each other so as to be on the protruding electrode side, and is heated and pressed in the vicinity of the thermal transformation point of the thermoplastic film. How to connect the electrodes.