JP2008153208A - Connecting member, and electrode-connecting construction using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-resolution connecting member, and an electrode-connecting construction that uses the same, capable of diminishing the emission of conductive particles from an electrode, preventing the connecting member from containing bubbles to improve the long-term connection reliability, and eliminating the need for aligning the conductive particles with the electrode for providing superior working efficiency. <P>SOLUTION: The connecting member has insulating adhesive layers 2, 3 on one face or both faces of a conductive sheet 1 comprising a conductive material 6 and a binder 5 and having conductive properties in the direction of the pressure; the insulating adhesive layers are lower in melt viscosity than the sheet, at least when being connected with the sheet; and the binder 5 contains epoxide-based adhesive denaturalized from polyeser, acrylic rubber, nitril butadiene rubber (NBR), or nylon, and a curing agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic component and a circuit board, a connection member that bonds and fixes circuit boards, and electrically connects both electrodes, and an electrode connection structure using the connection member.

  In recent years, with the miniaturization and thinning of electronic components, the circuits used for these have become dense and high definition, and it is difficult to connect such electronic components and fine electrodes with conventional solders, rubber connectors, and the like. Therefore, recently, anisotropic conductive adhesives and film-like materials (hereinafter referred to as connection members) having excellent resolution have been frequently used. This connecting member is made of an adhesive containing a predetermined amount of conductive particles. Both the connecting member is provided between an electronic component and an electrode or circuit, and a pressurizing or heating / pressurizing means is provided. The electrodes are electrically connected to each other, and the electrodes formed adjacent to the electrodes are provided with insulation so that the electronic component and the circuit are bonded and fixed. The basic idea for increasing the resolution of the connecting member is to ensure the insulation between the adjacent electrodes by making the particle size of the conductive particles smaller than between the adjacent electrodes, and also to reduce the content of the conductive particles. It is to obtain the conductivity at the connection portion by making it so that they do not contact each other and reliably existing on the electrode.

Japanese Patent Laid-Open No. 03-107888 Japanese Patent Laid-Open No. 04-366630 JP-A-61-195179

  In the above conventional method, when the particle size of the conductive particles is reduced, the particles cause secondary agglomeration and become larger, so that insulation between adjacent electrodes cannot be maintained, and when the content of the conductive particles is reduced, the conductive particles should be connected. Since the number of conductive particles on the electrode also decreases, the number of contact points is insufficient and sufficient continuity between connection electrodes cannot be obtained, so it is extremely difficult to increase the resolution of the connection member while maintaining long-term connection reliability. there were. In other words, due to the recent remarkable increase in resolution, that is, the electrode area and the gap between adjacent electrodes (spaces), or the increase in the ratio of the height to the width of the electrode, the conductive particles on the electrode are pressurized or heated at the time of connection. The pressure flows out together with the adhesive into the gap between adjacent electrodes, which hinders the high resolution of the connecting member. At this time, in order to suppress the outflow of the adhesive, the contact between the electrode having a high viscosity and the conductive particles is insufficient, and the electrodes facing each other cannot be connected. On the other hand, when the viscosity of the adhesive is lowered, in addition to the outflow of the conductive particles, there is a drawback in that bubbles are likely to be included in the space portion and connection reliability, particularly moisture resistance is lowered.

  In addition, as a connection member that enables connection of such fine electrodes and circuits and is excellent in connection reliability, there is a proposal of a connection member that forms a dense region of conductive particles only in necessary portions in the plane direction. According to this, although a dot-like fine electrode such as a semiconductor chip can be connected, there is a disadvantage that workability is inferior because accurate alignment of the conductive particle dense region and the electrode is necessary.

  The present invention has been made in view of the above-described drawbacks, and there is little outflow of conductive particles from the electrode, and it is difficult to contain bubbles in the connection portion, and it has excellent long-term connection reliability, and accurate alignment between the conductive particles and the electrode is not necessary An object of the present invention is to provide a high-resolution connecting member excellent in workability and an electrode connecting structure using the same.

According to the first aspect of the present invention, there is provided an insulating adhesive layer having a low melt viscosity at the time of connection, at least when connected to one or both sides of a conductive sheet having conductivity in a pressurizing direction composed of a conductive material and a binder. A connection member formed by forming a binder, wherein the binder is an epoxy adhesive containing an epoxy resin modified with polyester, acrylic rubber, nitrile butadiene rubber (NBR) or nylon, and a curing agent. It relates to members.
The invention according to claim 2 relates to the connection member according to claim 1, wherein the epoxy resin is modified with acrylic rubber.
The invention according to claim 3 relates to the connection member according to claim 1 or 2, wherein the adhesive layer material is an epoxy adhesive containing an epoxy resin modified with acrylic rubber.
Invention of Claim 4 is related with the connection member as described in any one of Claims 1-3 in which the said adhesive bond layer is formed in both surfaces of an electroconductive sheet.
According to a fifth aspect of the present invention, the conductive sheet in the connecting member according to any one of the first to fourth aspects exists between the electrode rows facing each other, and the opposing electrode and the conductive material are in contact with each other. And an adhesive layer covering at least the periphery of the protruding electrode of the electrode.
The invention according to claim 6 relates to the electrode connection structure according to claim 5, wherein at least one of the opposing connection electrodes is an electrode of a lead frame having no substrate.

  According to the present invention, the function of the conductive sheet, which is a conductive region composed of a conductive material that is an insulating coating particle coated with an insulating layer and a binder, and the adhesive layer, which is an insulating region, is separated. Therefore, a connection member having high resolution and excellent connection reliability and an electrode connection structure using the connection member can be obtained. Since the conductive material is a conductive material that is an insulating coated particle coated with an insulating layer, the conductive material has good insulation, can form a high concentration of the conductive material with respect to the binder, and contributes to conduction on the electrode. Many can be present, and the reliability can be improved with low resistance.

  The present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a connecting member for explaining an embodiment of the present invention. The connection member of the present invention is formed by forming adhesive layers 2 and 3 having a lower melt viscosity at the time of connection than the sheet on one side or both sides of the conductive sheet 1 having conductivity only in the pressing direction, Further, a separator 4 that can be peeled off from the adhesive layer is provided on one or both sides of the adhesive layer as necessary for the purpose of preventing contamination and improving the handleability.

  As shown in FIG. 2, the sheet 1 having conductivity in the pressurizing direction is made of a binder 5 containing a conductive material 6 which is insulating coating particles coated with an insulating layer. Here, the conductive material 6 may be protruded from the surface of the binder 5 from the beginning as shown in FIGS. 2 (a), 2 (f) and 2 (g), or may be pressurized or as shown in FIGS. 2 (b) to 2 (e). It may be in the form of particles having a particle diameter smaller than the thickness of the binder 5 that provides conductivity by reducing the thickness of the binder 5 by providing a heating and pressing means. The ratio of the conductive material 6 to the binder 5 is about 0.1 to 20% by volume. Further, in order to make it easy to obtain conductivity, the thickness of the binder 5 is preferably as thin as possible within the range in which film formation is obtained, and is 30 μm or less, more preferably 15 μm or less.

  As the conductive material 6, insulating coating particles as shown in FIG. 3C formed by coating the conductive material 6 with an insulating layer 8, or a combination of conductive particles and insulating particles can be applied. The conductive material 6 is preferably formed of conductive particles, for example, as illustrated in FIGS. 2A to 2E. Further, the conductive material 6 may have a through-hole in the binder 5 as shown in FIG. 2 (f) to form a conductor by plating or the like, or may be in the form of conductive fibers as shown in FIG. 2 (g). Examples of the conductive particles include metal particles such as Au, Ag, Ni, Cu, W, Sb, Sn, and solder, and carbon. These conductive particles are used as a core material, or non-conductive glass, ceramics, 3 (a) may be used in which a conductive layer made of the above-described material is formed on a core material made of plastic or the like by covering or the like. In order to secure one or more particles, preferably a large number of particles, on a minute electrode, small particles are suitable, and are 10 μm or less, more preferably 5 μm or less. Among these conductive particles, those in which a conductive layer is formed on a polymer core material such as a hot-melt metal such as solder or plastic, are deformable when heated or pressurized, and the contact area with the circuit during lamination Is preferable because it increases and improves. In particular, when a polymer is used as a nucleus, it does not show a melting point like solder, so that the softening state can be widely controlled by the connection temperature, and a connection member that can easily cope with variations in electrode thickness and flatness is obtained. 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 bite into the electrode or wiring pattern, so that an oxide film or a contamination layer Even in the presence of this, a low connection resistance is obtained and the reliability is improved.

  As the binder 5, it is preferable that a thermoplastic material or a material exhibiting curability by heat or light can be widely applied and has adhesiveness. Since these are excellent in heat resistance and moisture resistance after connection, application of a curable material is preferable. Among them, the epoxy resin adhesive can be preferably applied from the characteristics that it can be cured for a short time, has good connection workability, and has excellent adhesion in terms of molecular structure.

  Epoxy adhesives include, for example, high molecular weight epoxy, solid epoxy and liquid epoxy, urethane, polyester, acrylic rubber, NBR, nylon, etc. modified epoxy as the main component, curing agent, catalyst, coupling agent, filler, etc. What is added is generally.

  The connecting member of the present invention has an adhesive layer 2 having a melt viscosity lower than that of the sheet at least on the one or both sides of the sheet 1 having conductivity in the pressurizing direction, and further an adhesive layer 3 as necessary. Form. The thickness of the adhesive layers 2 and 3 is preferably formed so that the space portion excluding the volume of the electrode can be filled after connection. The adhesive layers 2 and 3 can be made of an insulating material similar to that of the binder 5 described above, and may contain a small amount of conductive particles within a range that does not affect the insulating properties.

  The melt viscosity at the time of connection will be described with reference to FIG. By changing the viscosity at the connection temperature like the binder 5 and the adhesive layer 2, the conductive material 6 is mixed with the adhesive layer 2 or 3 because the binder 5 has a relatively high viscosity when the adhesive layer 2 flows. It is difficult to suppress the outflow from the electrode. It is preferable to connect the adhesive layers 2 and 3 with a viscosity of 100 poise or less. The difference in melt viscosity when connecting the adhesive layers 2 and 3 and the binder 5 is 10 poise or more, preferably 100 poise or more. Further, if the binder 5 at this time has at least some fluidity, it is easy to obtain conductivity in the pressing direction. 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 when connected. The adhesive layers 2 and 3 may have the same material, thickness, viscosity, or the like, or may be arbitrarily changed, for example, a combination suitable for the material of the electrode substrate. Moreover, you may form the adhesive bond layers 2 and 3 in two or more layers, respectively.

  As a method for producing the connection member of the present invention, for example, a method of laminating the conductive sheet 1 and the adhesive layer 2 or sequentially coating and laminating can be employed.

  An electrode connection structure using the connection member of the present invention will be described with reference to FIGS. FIG. 5 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 conductive sheet 1 in the pressing direction. That is, although the adhesive layer 3 does not exist on the plane electrode 13 side, the conductive sheet 1 exists between the opposing upper and lower substrates 11-11 ′ and between the opposing electrode rows, and the opposing electrode 12 and 13 is in contact with the conductive material 6 in the conductive sheet 1. The adhesive layer 2 covers at least the protruding electrode 12 of the protruding electrode 12. Here, the planar electrode 13 refers to a case where there is no unevenness from the surface of the substrate 11 ′ or even a few μm or less. Examples of these are representative electrodes formed by the additive method or thin film method.

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

  FIG. 7 is similar to FIG. 6, but with one electrode 14 having a top. Despite the top, the conductive sheet 1 is present between the electrode 12 and the top 14. The degree of deformation of the conductive material 6 is changed in accordance with the distance between the electrodes 12-14. Examples of the electrode 14 having the top include a conductive paint printing, a circuit electrode by a green sheet method, and bumps of a semiconductor chip (IC).

  FIG. 8 shows an example of connection between the protruding electrodes 12 and 12 ′, but is a case where no substrate is provided on the electrode 12 side. As an electrode having no substrate, there is a lead frame of a package type IC such as a so-called QFP. In the case of protruding electrodes as shown in FIGS. 6 to 8, in the conventional technique, one electrode is shifted to a space due to the thermal pressure at the time of connection, and connection is impossible, or the outflow of particles from the electrode is particularly remarkable. There was a problem.

  As shown in FIG. 9, the adhesive layer 2 can be overfilled with respect to the space so as to protrude from the periphery of the connecting portion, and a function of a sealing material or a moisture-proof material can be imparted. In this case, a 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 connection 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, inorganic substances such as glass and ceramics, and the like. The protruding electrode 12 can include various circuits and terminals in addition to the above. The various electrodes shown in FIGS. 5 to 8 can be applied in any combination.

  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, the conductive sheet has a higher viscosity than the adhesive layer, so there is less outflow of conductive particles from the electrode, and the conductive sheet has a high density on the electrode. Connection is possible while existing. Since the viscosity of the adhesive layer can be adjusted arbitrarily, it is possible to take a configuration in which bubbles are hardly included in the connection portion. Moreover, since the sheet | seat which has electroconductivity in a pressurization direction exists in every part of the thickness direction of a connection member, exact alignment with a conductive particle and an electrode is unnecessary. Depending on the purpose of the adhesive layer, for example, a combination suitable for the material of the electrode substrate is possible, so 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 a difference in heat resistance, it is possible to preferentially peel from one substrate surface and to provide so-called repair property for reconnection. Further, it is possible to obtain a reinforcing or moisture-proof effect by causing the adhesive layer to protrude outside the connecting portion and acting as a sealing material.

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

Example 1
(1) Production of conductive sheet Liquid epoxy resin (epoxy equivalent) containing acrylic rubber (glass transition point-10 ° C, molecular weight 500,000, containing 1% carboxyl group as functional group) and microcapsule type latent curing agent as matrix The ratio of 185) was 40/60, and a 30% solution of ethyl acetate was obtained. To this solution, 5% by volume of conductive particles in which a Ni / Au 0.2 / 0.02 μm thick metal coating was formed on polystyrene-based particles having a particle size of 5 ± 0.2 μm was added and mixed and dispersed. This dispersion was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 110 ° C. for 20 minutes to obtain a sheet having a matrix thickness of 5 μm. This sheet corresponds to FIG.
(2) Formation of Adhesive Layer A 15 μm thick sheet containing no conductive particles was prepared in the same manner as in (1) above, with the ratio of acrylic rubber and liquid epoxy resin containing a microcapsule type latent curing agent being 10/90. did. First, the conductive sheet surface of (1) and the adhesive layer surface of (2) are laminated while being rolled with a rubber roll, and then the adhesive layer surface is similarly laminated to this surface while peeling the separator on the conductive sheet surface. A connecting member was obtained. The melt viscosity of these matrices and adhesive layers were the characteristics of FIG. Here, the melt viscosity is determined while heating and melting the composition excluding the curing agent and gradually cooling it.
(3) Connection Two-layer FPC circuit boards (circuit pitch is 100 μm, electrode of a parallel circuit with an electrode width of 50 μm) having a copper circuit with a height of 18 μm on a polyimide film were connected to each other. First, the connecting member was placed on the end electrode of one circuit board with a width of 1.5 mm, and the separator was peeled off and then attached. Thereafter, the separator was peeled off, the other circuit board and the upper and lower circuits were aligned, and connected at 150 ° C., 20 kgf / mm ² for 15 seconds.
(4) Evaluation When the cross section of this connection body was polished and observed with a microscope, it was a connection structure corresponding to FIG. The space was free of bubbles and the particles were spherical, but the particles were compressed and deformed on the electrodes and held in contact with the upper and lower electrodes. When the resistance between the electrodes facing each other was evaluated as the connection resistance, and between the adjacent electrodes as the insulation resistance, the connection resistance was 1Ω or less and the insulation resistance was 10 ⁸ Ω or more, which changed even after treatment at 85 ° C. and 85% RH for 1000 hours. No long-term reliability was observed.

Example 2
Similar to Example 1, except that the adhesive layer is formed on only one side, and one of the circuit boards has a thin film circuit with an indium oxide thickness of 0.2 μm (ITO, surface resistance 20Ω / □) on glass 1.1 mm. An electrode was used, and a conductive sheet was placed on the planar electrode side. This configuration corresponds to FIG. Also in this case, good connection characteristics were exhibited as in Example 1. In this example, since the adhesive force on the glass side of the flat electrode was relatively lower than that on the FPC side, the interface peeled cleanly when forcibly peeling from the glass side, and subsequent cleaning was easy. This is suitable for providing repairability in the connection of liquid crystal panels that are frequently used in the same configuration at present.

Example 3
Similar to Example 2, but instead of FPC, an IC chip (2 × 10 mm, height 0.5 mm, 200 gold electrodes of 50 μm square and 20 μm height called bumps formed around 4 sides) was used. . The ITO electrode on the glass side was changed to correspond to the size of the bump electrode of the IC chip. Further, the conductive material of the conductive sheet is conductive particles having an average particle diameter of 3 μm, the addition amount is 1% by volume, and the matrix has a thickness of 10 μm, and the configuration shown in FIG. Although the connection body has a configuration corresponding to FIG. 7, it showed good connection characteristics. In this example, the bump was mushroom-shaped and had a top, but the particles were compressed and deformed and held in contact with the upper and lower electrodes. Air bubbles were not mixed between adjacent bumps, and good long-term reliability was demonstrated. Some of the conductive particles have a different degree of deformation depending on the distance between the electrodes facing each other, and some of the conductive particles bite into the bumps.

Example 4
Although it was the same as that of the connection member of Example 3, the thickness of the adhesive layer was formed at 25 μm on one side and 50 μm on the other surface. The electrodes were QFP-type IC leads (thickness: 100 μm, pitch: 300 μm), and were connected to terminals of copper on a glass epoxy substrate having a thickness of 35 μm. This configuration has no substrate on one side corresponding to FIG. In this example, the electrodes were connected to each other with a large height, but there was no electrode displacement and good connection characteristics were shown. 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. Air bubbles were not mixed between adjacent electrodes, and good long-term reliability was demonstrated. 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
Although it is the same as that of the connection member of Example 3, the surface of the conductive particles was subjected to an insulation coating treatment as shown in FIG. That is, the surface of the conductive particles having an average particle diameter of 3 μm was coated with a nylon resin having a glass transition point of 127 ° C. to a thickness of about 0.2 μm, and the addition amount was increased to 10% by volume. The connection structure of this example is shown in FIG. Evaluation was made in the same manner as in Example 3, but good connection characteristics were exhibited. In this example, the number of particles on the electrode 12 increased remarkably. The electrode connecting portion 12-12 ′ can be conducted by the softening of the insulating layer 8 and the binder 5 due to the heat pressure at the time of connection, but the space portion of the adjacent electrode row has a small heat pressure and the surface of the conductive material 6 is the insulating layer 8. As it was still covered with, the insulation was good. In this configuration, the concentration of the conductive material 6 with respect to the binder 5 can be configured with a high density.
When the insulating coating particles in which the conductive material is coated with the insulating layer are used, it can be applied to the electrode connection structure shown in the first to fourth embodiments, and the insulating property of the space portion is improved as in the first embodiment, so that the conductive material 6 It is possible to configure the concentration of the binder 5 at a high density, increase the number of particles on the electrode, and reduce the connection resistance.

The cross-sectional schematic diagram of the connection member which shows one Example of this invention. The cross-sectional schematic diagram of the electroconductive sheet suitable for this invention. The cross-sectional schematic diagram of the conductor suitable for invention. The diagram which shows the measurement result of temperature and melt viscosity which shows one Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows one Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows the other Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows the other Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows the other Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows the other Example of this invention. The cross-sectional schematic diagram which shows the connection structure of the electrode which shows one Example of this invention.

Explanation 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 Projecting Electrode 13 Planar Electrode 14 Electrode with Top 15 IC.

Claims (6)

It is a connecting member formed by forming an insulating adhesive layer having a melt viscosity at least lower than that of the sheet on one or both sides of a conductive sheet having conductivity in a pressing direction composed of a conductive material and a binder. And
A connecting member, wherein the binder is an epoxy adhesive containing an epoxy resin modified with polyester, acrylic rubber, nitrile butadiene rubber (NBR) or nylon, and a curing agent.   The connection member according to claim 1, wherein the epoxy resin is modified with acrylic rubber.   The connection member according to claim 1 or 2, wherein the material of the adhesive layer is an epoxy adhesive containing an epoxy resin modified with acrylic rubber.   The connection member according to any one of claims 1 to 3, wherein the adhesive layer is formed on both surfaces of the conductive sheet.   The conductive sheet in the connection member according to any one of claims 1 to 4 exists between the electrode rows facing each other, and the opposing electrode and the conductive material are in contact with each other, and an adhesive layer is formed on the electrode. An electrode connection structure characterized by covering at least the periphery of the protruding electrode. 6. The electrode connection structure according to claim 5, wherein at least one of the opposing connection electrodes is an electrode of a lead frame having no substrate.

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