JPH07230840A - Connecting member and electrode connecting structure using the same - Google Patents

Abstract

PURPOSE:To improve workability, and enhance resolution by forming an insulating adhesive layer having low connecting time melting viscosity on a sheet which is composed of a conductive material and a binder and has electric conductivity in the pressurizing direction. CONSTITUTION:A sheet 1 having electric conductivity in the pressurizing direction is composed of a binder 5 containing a conductive material 6, and a particle-shaped material having a particle diameter smaller than a thickness of the binder 5 is used as the material 6. This is pressurized, and the thickness of the binder 5 is reduced, and electric conductivity is applied. In a connecting member, an adhesive layer 3 whose at least connecting time melting viscosity is lower than the sheet 1 is formed on a single surface or both surfaces of the sheet 1 having electric conductivity in the pressurizing direction. The thickness is set so that a space part except the electrode volume can be filled after it is connected. Then, since the binder 5 is relatively high in viscosity at flowing time of adhesive layers 2 and 3, the material 6 becomes hard to be mixed with the adhesive layers 2 and 3. In the space part in an adjacent electrode row, heat pressure is reduced, and since the material 6 is covered with an insulating layer 8 as it is, insulating performance also becomes excellent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electronic parts and circuit boards,
The present invention relates to a connecting member for adhering and fixing circuit boards to each other and electrically connecting both electrodes to each other, and an electrode connecting structure using the connecting member.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and thinning of electronic parts, the circuits used for them have become higher in density and higher definition, and such electronic parts and fine electrodes are connected by conventional solder or rubber connectors. Since it is difficult to deal with this, an anisotropic conductive adhesive or a film-like material (hereinafter referred to as a connecting member), which has excellent resolution, has been widely used recently. The connecting member is made of an adhesive containing a predetermined amount of conductive particles, 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 to bond and fix the electronic component and the circuit. The basic idea for increasing the resolution of the connecting member is to secure the insulating property between the adjacent electrodes by making the particle diameter of the conductive particles smaller than that between the adjacent electrodes,
At the same time, the content of the conductive particles is set to such an extent that the particles do not come into contact with each other, and the conductive particles are surely present on the electrode to obtain the conductivity in the connecting portion.

[0003]

In the above-mentioned conventional method, when the particle size of the conductive particles is reduced, the particles agglomerate with each other and become large, and the insulating property between the adjacent electrodes cannot be maintained. When the content of particles is reduced, the number of conductive particles on the electrodes to be connected also decreases, so that the number of contact points is insufficient and sufficient conduction cannot be obtained between the connecting electrodes.
It was extremely difficult to improve the resolution of the connecting member while maintaining the long-term connection reliability. That is, in recent years, the resolution has been remarkably improved, that is, the electrode area and the gap between adjacent electrodes (space).
Due to the miniaturization of electrodes or the increase in the ratio of the height to the width of the electrodes, the conductive particles on the electrodes flow out into the gap between adjacent electrodes together with the adhesive due to the pressure applied at the time of connection or heating and pressurization, which improves the resolution of the connection member Was hindering At this time, in order to suppress the outflow of the adhesive, the contact between the electrode having a high viscosity of the adhesive and the conductive particles becomes insufficient, and it becomes impossible to connect the electrodes facing each other. On the other hand, when the viscosity of the adhesive is lowered, there is a drawback that the space is apt to contain bubbles in addition to the outflow of the conductive particles, and the connection reliability, particularly the moisture resistance is lowered.

Further, as a connection member which enables connection of such fine electrodes and circuits and is excellent in connection reliability, a connection member is proposed in which a dense region of conductive particles is formed only in a necessary portion in the plane direction. There is also. 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 deteriorated because accurate alignment of the dense region of conductive particles and the electrode is required.

The present invention has been made in view of the above-mentioned drawbacks. The conductive particles are less likely to flow out from the electrodes, bubbles are not easily contained in the connection portion, and long-term connection reliability is excellent. It is an object of the present invention to provide a high-resolution connection member that does not require alignment and is excellent in workability, and an electrode connection structure using the same.

[0006]

Means for Solving the Problems That is, according to the present invention, an insulating material having a melt viscosity at the time of connection at least lower than that of the above-mentioned sheet is provided on one side or both sides of a sheet made of a conductive material and a binder and having conductivity in the pressing direction. A connecting member having an adhesive layer formed thereon, and the conductive sheet using the conductive sheet are present between electrode rows facing each other, and the opposing connecting electrodes and the conductive material are in contact with each other, and the adhesive layer is at least a protrusion of the electrode. The present invention relates to an electrode connection structure characterized by covering the periphery of an electrode.

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 has an adhesive layer 2, which has a lower melt viscosity at the time of connection than that of the sheet, on one or both sides of a conductive sheet 1 having conductivity only in the pressing direction,
And 3 are formed, and a separator 4 that can be peeled from the adhesive layer is provided on one side or both sides of the adhesive layer as needed for the purpose of preventing contamination and improving handleability.

The sheet 1 having conductivity in the pressing direction is shown in FIG.
As shown in FIG. 3, the binder 5 contains a conductive material 6. Here, as the conductive material 6, as shown in FIGS.
Even if it is projected from the surface of the binder 5 from the beginning as shown in (g), or the thickness of the binder 5 is reduced by constructing a pressurizing or heating pressurizing means as shown in FIGS. 2 (b) to (e). It may be in the form of particles having a particle size smaller than the thickness of the binder 5 that imparts conductivity. The ratio of the conductive material 6 to the binder 5 is about 0.1 to 20% by volume. Further, in order to easily obtain conductivity, the thickness of the binder 5 is preferably as thin as possible in the film formation range, and is preferably 30 μm or less, more preferably 15 μm or less.

The conductive material 6 is, for example, as shown in FIG.
It is preferable to form the conductive particles as illustrated in (e) to (e). In addition, the conductive material 6 is provided with through holes in the binder 5 as shown in FIG.
It may be in a conductive fiber shape as shown in (g). As the conductive particles, there are metal particles such as Au, Ag, Ni, Cu, W, Sb, Sn and solder, and carbon, and these conductive particles are used as a core material, or non-conductive glass, ceramics, A core material made of plastic or the like and a conductive layer made of the above-mentioned material is formed by coating or the like as shown in FIG.
It may be something like. Further, the insulating coated particles as shown in FIG. 3C, which are obtained by coating the conductive material 6 with the insulating layer 8 as described above, and the combined use of conductive particles and insulating particles are also applicable. In order to secure one or more, preferably a large number of particles on a minute electrode, small particle size is suitable, and it is 10 μm or less, more preferably 5 μm or less. Among these conductive particles, the one in which a conductive layer is formed on a hot melt metal such as solder or a polymer core material such as plastic has heat pressurization or deformability by pressurization, and the contact area with the circuit at the time of stacking Is increased and improved, which is preferable. In particular, when a polymer is used as a core, it does not exhibit a melting point like solder, so that the softened state can be widely controlled at the connection temperature, and a connection member that easily copes with variations in the thickness and flatness of the electrode can be obtained, which is preferable. Further, for example, in the case of hard metal particles such as Ni and W, or particles having a large number of protrusions on the surface as shown in FIG. 3B, the conductive particles dig into the electrodes and wiring patterns, so that an oxide film or a contamination layer is formed. Even in the presence of, low connection resistance is obtained and reliability is improved.

The binder 5 can be widely applied with a thermoplastic material or a material curable by heat or light, 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 resin 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, epoxies modified with urethane, polyester, acrylic rubber, NBR, nylon and the like as main components, and hardeners, catalysts, coupling agents, It is common to add a filler or the like.

The connecting member of the present invention comprises, on one or both sides of the sheet 1 having conductivity in the pressing direction, an adhesive layer 2 having a melt viscosity lower than that of the sheet at the time of connection, and an adhesive if necessary. Form layer 3. The thickness of the adhesive layers 2 and 3 is preferably formed so that the space portion other than the volume of the electrodes can be filled after the connection. Adhesive layers 2, 3
An insulating material similar to the binder 5 described above can be applied, and may contain a small amount of conductive particles as long as the insulating property is not affected.

The melt viscosity at the time of connection will be described with reference to FIG. By changing the viscosity at the connection temperature to that of the binder 5 and the adhesive layer 2, the binder 5 can flow when the adhesive layer 2 flows.
Is relatively high in viscosity, it is difficult for the conductive material 6 to mix with the adhesive layer 2 or 3, and the outflow from the electrodes is suppressed. It is preferable that the adhesive layers 2 and 3 have a viscosity of 100 poise or less for connection. The difference in melt viscosity between the adhesive layers 2 and 3 and the binder 5 is 10 poise or more, preferably 1
It is at least 00 poise. If the binder 5 at this time has at least some fluidity, conductivity in the pressing direction is easily obtained. In particular, when the conductive material 6 is buried in the binder 5 or when the adhesive layer is present on one side, the binder 5 needs to have fluidity at the time of connection. The adhesive layers 2 and 3 may have the same material, thickness, viscosity, etc.,
Alternatively, the combination can be arbitrarily changed, such as a combination suitable for the material of the electrode substrate. Also, adhesive layers 2 and 3
May be formed in two or more layers.

As the method for producing the connecting member of the present invention, for example, a method of laminating the conductive sheet 1 and the adhesive layer 2 or a method of sequentially applying and laminating them can be adopted.

An electrode connection structure using the connection member of the present invention will be described with reference to FIGS. FIG. 5 shows the protruding electrode 12 formed on the substrate 11 and the planar electrode 13 on the substrate 11 ′.
And are structures connected in the pressing direction via the conductive sheet 1. That is, when the adhesive layer 3 does not exist on the flat electrode 13 side, the conductive sheet 1 exists between the opposing upper and lower substrates 11-11 ′ and between the electrode rows facing each other.
Opposing electrodes 12 and 13 are in contact with the conductive material 6 in the conductive sheet 1. Further, the adhesive layer 2 covers at least the periphery of the protruding electrode of the protruding electrode 12. Here, the planar electrode 13 has no unevenness from the surface of the substrate 11,
Even if there is a few μm or less, it means a few cases. Typical of these are electrodes formed by an additive method or a thin film method.

FIG. 6 shows a structure in which the electrodes formed on the substrate 11 are the protruding electrodes 12 and 12 ′, and the conductive sheet 1 is connected to both surfaces via connecting members having adhesive layers 2 and 3. is there. The adhesive layers 2 and 3 are the protruding electrodes 12 respectively.
And 12 'cover the periphery of the protruding electrodes and are in contact with the respective substrate surfaces 11 and 11'.

FIG. 7 is similar to FIG. 6, but with one electrode 1
4 has a top. The conductive sheet 1 is present between the electrode 14 and the top 15 despite the presence of the top. In the space 12-14 between the electrodes, the degree of deformation of the conductive material 6 changes according to the distance. Examples of the electrode 15 having a top portion include a circuit electrode formed by printing a conductive paint or a green sheet method, or bumps of a semiconductor chip (IC).

FIG. 8 shows an example of connecting the protruding electrodes 12 and 12 'to each other, but does not have a substrate on the electrode 12 side. As the electrode having no substrate, there is a so-called QFP or other package type IC lead frame. 6 to 8
In the case of such protruding electrodes as described above, in the prior art, one of the electrodes is displaced due to the heat and pressure at the time of connection and cannot be connected, or the outflow of particles from the electrode is particularly remarkable, which is a problem. .

It is also possible to overfill the space with the adhesive layer 2 as shown in FIG. 9 and to allow it to stick out around the connection portion to impart the function of a sealing material or a moistureproof material. In this case, the structure in which the end portion of the conductive sheet 1 is covered with the adhesive layers 2 and / or 3 can be obtained by a single connecting operation.

5 to 9, 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. The various electrodes shown in FIGS. 5 to 8 can be applied in an arbitrary combination.

[0021]

According to the present invention, an adhesive layer having a low melt viscosity at the time of connection is formed on one or both sides of a sheet having conductivity in the pressing direction. Therefore, even if the adhesive layer has a low viscosity due to heat and pressure at the time of connection, since the conductive sheet has a higher viscosity than the adhesive layer, the conductive particles are less likely to flow out from the electrode, and the conductive sheet has a high density. Connection is possible while existing. Since the viscosity of the adhesive layer can be arbitrarily adjusted, it is possible to make it 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. Depending on the purpose, the adhesive layer can be combined, 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 making them have different heat resistance, it is possible to give a so-called repair property in which they can be preferentially separated from one substrate surface and reconnected. Further, the adhesive layer can be extended to the outside of the connection portion to act as a sealing material, so that reinforcement and moistureproof effects can be obtained.

[0022]

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

Example 1 (1) Preparation of Conductive Sheet Acrylic rubber (glass transition point −10) was used as a matrix.
The ratio of liquid epoxy resin (epoxy equivalent: 185) containing a microcapsule type latent curing agent at 40 ° C. is 40/6.
It was set to 0 to obtain a 30% solution of ethyl acetate. In this solution,
Ni / Au on polystyrene particles with 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 mixed and dispersed. This dispersion liquid was applied to a separator (polyethylene terephthalate film with silicone treatment, thickness 40 μm) by a roll coater, and 1
It was dried at 10 ° C. for 20 minutes to obtain a sheet having a matrix thickness of 5 μm. This sheet corresponds to FIG. 2 (b). (2) Formation of Adhesive Layer A sheet having a thickness of 15 μm containing no conductive particles and having a ratio of acrylic rubber to liquid epoxy resin containing a microcapsule type latent curing agent of 10/90 was prepared in the same manner as in (1) above. did. First, the conductive sheet surface of (1) and the adhesive layer surface of (2) are laminated while being rolled by a rubber roll, and then the separator of the conductive sheet surface is peeled off, and this surface is further laminated with an adhesive layer surface in the same manner. Then, a connection member was obtained. The melt viscosities of these matrices and adhesive layers were the characteristics of FIG. The melt viscosity is obtained by heating and melting the composition excluding the curing agent and slowly cooling it. (3) Connection Two-layer FPC circuit boards (circuit electrodes having a circuit pitch of 100 μm and an electrode width of 50 μm) having a copper circuit having a height of 18 μm on a polyimide film were connected to each other. First, connect the connecting member to the end electrode of one circuit board by 1.5 mm.
It was placed in the width, and after the separator was peeled off, it was attached. After that, the separator is peeled off, the other circuit board and the upper and lower circuits are aligned, and the temperature is 150 ° C. and 20 kgf / mm ² It was connected in 15 seconds. (4) Evaluation When a cross section of this connection body was polished and observed under a microscope, FIG.
It was a considerable connection structure. The space was free of bubbles and the particles were spherical, but the particles were compressed and deformed on the electrode and held in contact with the upper and lower electrodes. When the evaluation was made between the electrodes facing each other as the connection resistance and between the adjacent electrodes as the insulation resistance,
Connection resistance is less than 1Ω, insulation resistance is 10 ⁸ Ω or more,
These showed almost no change even after treatment at 85 ° C. and 85% RH for 1000 hours and showed good long-term reliability.

Example 2 The same as Example 1, except that the adhesive layer was formed on only one side, and one of the circuit boards had 1.1 mm of glass on which indium oxide had a thickness of 0.2 μm (ITO, surface resistance of 20 Ω / □). The flat electrode having the thin film circuit of No. 1 was used, and the conductive sheet was placed on the flat electrode side. This configuration corresponds to FIG. Also in this case, as in the case of Example 1, good connection characteristics were shown.
In this example, since the adhesive strength 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 cleanly 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 3 The same as Example 2, except that the FPC was replaced by an IC chip (2 × 10 mm, height 0.5 mm, four gold electrodes of 50 μm square and 20 μm height called bumps around the four sides). Individual 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.
In addition, the conductive material of the conductive sheet 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.
m sheet, and the configuration of FIG. The connection body had a structure corresponding to that shown in FIG. 7, but showed good connection characteristics.
In this example, the bump was mushroom-shaped and had a top portion, but the particles were deformed by compression and held in contact with the upper and lower electrodes. There was no air bubble mixing between adjacent bumps, showing good long-term reliability. It was also observed that the conductive particles differ in the degree of deformation of the particles depending on the relative distance between the electrodes and partially penetrate into the bumps.

Example 4 Similar to the connecting member of Example 3, the thickness of the adhesive layer was 25 μm on one side and 50 μm on the other side. The electrode is Q
FP type IC lead (thickness 100μm, pitch 300μ
m), which was connected to a terminal of copper having a thickness of 35 μm on the glass epoxy substrate. This configuration is a configuration in which there is no substrate on one side corresponding to FIG. In this example, electrodes having a large height were connected to each other, but good connection characteristics were exhibited without any electrode displacement. Although the conductive material in the conductive sheet is not shown, the particles were compressed and deformed 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. In this example, the adhesive layer was formed along the lead height even in the portion without the substrate, and the lead could be fixed.

Example 5 Similar to the connecting member of Example 3, the surface of the conductive particles was subjected to an insulating coating treatment as shown in FIG. 3 (c). That is, the surface of the conductive particles having an average particle diameter of 3 μm is
The coating amount was increased to 10% by volume by coating with a nylon resin of 0.2 ° C. at a thickness of about 0.2 μm. The connection structure of this embodiment is shown in FIG.
Shown in. Evaluation was made in the same manner as in Example 3, but good connection characteristics were shown. In this example, the number of particles on the electrode 12 was significantly increased. The electrode connecting portions 12-12 ′ can be conducted by softening the insulating layer 8 and the binder 5 due to the thermal pressure at the time of connection, but the space portion of the adjacent electrode row has a small thermal pressure and the conductive material 6 is used.
Since the surface of the above was still covered with the insulating layer 8, the insulating property was also good. With this configuration, the concentration of the conductive material 6 with respect to the binder 5 can be made high.

[0028]

As described in detail above, according to the present invention, the functions of the conductive sheet, which is the conductive region, and the adhesive layer, which is the insulating region, can be formed separately, so that high resolution can be achieved. A connection member having excellent connection reliability and an electrode connection structure using the connection member can be obtained.

[Brief description of drawings]

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

FIG. 2 is a schematic cross-sectional view of a conductive sheet suitable for the present invention.

FIG. 3 is a schematic cross-sectional view of a conductor suitable for the present invention.

FIG. 4 is a diagram showing measurement results of temperature and melt viscosity showing an example of the present invention.

FIG. 5 is a schematic sectional view showing a connection structure of electrodes according to an embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing an electrode connection structure showing another embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing an electrode connection structure showing another embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view showing an electrode connection structure showing another embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view showing an electrode connection structure showing another embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing an electrode connection structure showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive sheet 2 Adhesive layer-1 3 Adhesive layer-2 4 Separator 5 Binder 6 Conductive material 7 Core material 8 Insulating layer 11 Substrate 12 Projective electrode 13 Planar electrode 14 Electrode having top part 15 IC

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Goto 1500 Ogawa, Shimodate, Ibaraki Prefecture Shimodate Laboratory, Hitachi Chemical Co., Ltd. (72) Kyohisa Ota 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co. Company Shimodate Institute (72) Inventor Yoshiyuki Ikezoe 1-1-1, Nishishinjuku, Shinjuku-ku, Tokyo Hitachi Chemical Co., Ltd.

Claims (2)

[Claims] 1. An insulative adhesive layer having a lower melt viscosity at the time of connection than that of the sheet is formed on one side or both sides of a conductive sheet made of a conductive material and a binder and having conductivity in the pressing direction. Connection member. 2. A conductive sheet according to claim 1, which is present between electrode rows facing each other, and is in contact with a connecting electrode facing the conductive material, and an adhesive layer surrounds at least the protruding electrode of the electrode. An electrode connection structure, characterized in that