JP2007220839A - Circuit board and electrode connection structure of circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit board A and an electrode connection structure B of circuit excellent in connection reliability in which a sufficiently low connection resistance is attained and stabilized connection of electrode is ensured, even if the electrode pitch becomes narrow due to minute structure. <P>SOLUTION: In the circuit board A, a conductive bump 20 is provided on the electrode surface of a circuit board 10 on which an electrode 11 is provided wherein the conductive bump 20 uses synthetic resin as a nucleus 21, and its surface is covered with a thin conductive metal layer 22 having a melting point of 250°C or below and structured in a molten metal bonding 30 to the electrode surface. In the electrode connection structure B, the surface of the electrode 11 on the circuit board A and the surface of the electrode 41 on other circuit board 40 are arranged oppositely, the conductive bump 20 using synthetic resin as a nucleus 21 and having a surface covered with a thin conductive metal layer 22 having a melting point of 250°C or below is provided between the opposing electrode surfaces. The conductive bump 20 is processed in the molten metal bonding 30 to the electrode surface under a state pressed slightly flatly, and no conductive fine particle exist in the space between respective electrodes. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a connection terminal such as an integrated circuit or a liquid crystal display panel, and other electric members disposed opposite thereto, FPC (flexible printed circuit board), TCP (tape carrier package substrate), COF (chip on film substrate), etc. The present invention relates to a circuit board suitable for so-called face-down mounting (flip chip mounting) and a circuit electrode connection structure.

  When electrically connecting a connection terminal such as an integrated circuit or a liquid crystal display panel with another electrical member disposed opposite thereto, such as an FPC (flexible printed circuit board) or TCP (tape carrier package board), an electrode of the circuit An OLB (Outer Lead Bonding) method is widely employed as a connection method when the (connection terminals) are arranged at a fine pitch.

  In the OLB method, when electrically connecting two circuit electrodes, for example, an electrode of a liquid crystal panel and an electrode of a drive circuit board, an anisotropic conductive material in which conductive fine particles are dispersed between opposing electrodes. The adhesive sheet is sandwiched and heated and pressed to heat and melt the adhesive sheet, so that the liquid crystal panel and the drive circuit board are electrically connected only in the thickness direction. According to this OLB method, a large number of electrodes can be connected together.

  In recent years, such electronic circuits have been increased in pin count and fineness (fine pitch), and circuit connections of 50 lines / 1 mm or more are often implemented. In this case, a COG (Chip on Glass) method in which the bare IC chip electrode and the liquid crystal panel electrode are directly connected by an anisotropic conductive adhesive sheet in which conductive fine particles are dispersed is mainly employed.

  However, if the electrode pitch becomes narrower and the electrode pitch becomes narrower, the conductive fine particles are connected to a space other than the portion sandwiched between the electrodes facing each other, and the adjacent conductive particles or upper and lower electrodes are separated by these continuous conductive fine particles. Will be conducted, and there is a danger of short-circuiting, resulting in connection reliability problems such as energization failure.

  In order to solve the above problem, for example, in Patent Document 1 below, an electrode (including a protruding electrode such as a bump) of a semiconductor element having a connection pad as an input / output terminal (for example, a bare chip electronic circuit of a driver IC) is disclosed. On top of this, a method has been proposed in which a plurality of conductive fine particles are fixed in advance with the resin by applying a thermoplastic resin liquid in which conductive fine particles are dispersed. Further, in Patent Document 2 below, a protruding electrode or an input / output terminal is obtained by immersing a semiconductor element having a protruding electrode or an input / output terminal in a plating solution in which conductive fine particles are dispersed and performing metal plating such as gold plating. On top of this, a method of fixing a plurality of conductive fine particles in advance with a plating metal has been proposed.

  According to each of the proposed methods, a plurality of conductive fine particles are fixed on the circuit electrode in advance, so there is no need to use an anisotropic conductive adhesive sheet in which conductive fine particles are dispersed. It is possible to dispose a plurality of conductive fine particles necessary for conduction only on the circuit electrode. In the electrode connection structure of the circuit thus obtained, the semiconductor element and other electrical elements disposed opposite to the semiconductor element are provided. Adhesion and fixation with the member is performed by an electrically insulating thermosetting resin that does not contain conductive fine particles, so that there is no problem of reliability such as poor conduction.

  However, the method of bonding and fixing a plurality of conductive fine particles on a circuit electrode by a coating method or a plating method using a thermoplastic resin liquid is difficult to accurately place the conductive fine particles on the electrode in a desired number. . Moreover, in the said coating method, since the contact of both electrodes and electroconductive fine particles is only contacting, the electrical connection with an electrode may become unstable.

  In the above plating method, the contact point between one electrode and the conductive fine particles is fixed by the plating metal, but the contact point between the other electrode and the conductive fine particles is merely in contact with each other. The electrical connection may become unstable. Furthermore, since the contact area with the electrode is very small, the plating method has a drawback that the conductive fine particles fixed at the time of mounting are peeled off. As described above, the conventional technique still has a problem to be improved in terms of connection reliability with the electrode.

  In Patent Document 3 below, in the conventional OLB method, the first metal thin layer is formed on the surface of the core material made of the polymer, and the second metal thin layer is formed thereon. A method using an anisotropic conductive adhesive sheet or an anisotropic conductive adhesive in which fine particles are dispersed has been proposed.

In this case, the first metal thin layer and the second metal thin layer are alloyed to a melting point of 250 ° C. or less by diffusion mixing by heating and pressurization, whereby the opposing electrodes and the conductive fine particles are molten metal-bonded. However, as in the conventional OLB method, conductive fine particles exist in the space between adjacent electrodes, and there is a risk of short circuit. Moreover, it is difficult to optimally set the heating and pressing conditions, and depending on the heating and pressing conditions, the alloyed metal thin layer is melted and pushed to the periphery, exposing the core material of conductive fine particles or the metal thin layer being very thin. In some cases, a thin layer of adhesive resin is sandwiched between the contacts between the electrode and the conductive fine particles, which may cause connection reliability problems such as poor conduction.
JP 2004-214375 A JP 2003-59959 A JP-A-63-231889

  The present invention solves the above-described problems, and an object of the present invention is to connect terminals such as an integrated circuit and a liquid crystal display panel, and other electric members disposed opposite thereto, FPC (flexible printed circuit board). Circuit board and circuit electrode connection structure suitable for electrically connecting TCP and tape (tape carrier package substrate), etc., even when the electrode pitch is narrowed with high density, different electrodes are electrically connected to each other. An object of the present invention is to provide a circuit board and a circuit electrode connection structure having excellent connection reliability, in which a sufficiently low connection resistance is obtained without short-circuiting and stable connection with an electrode can be obtained.

  The circuit board according to claim 1 is provided with a plurality of conductive protrusions on an electrode surface of a circuit board in which a plurality of electrodes are provided at intervals, and the plurality of conductive protrusions are made of synthetic resin. The core is covered with a thin conductive metal layer having a melting point of 250 ° C. or lower and is melt-bonded to the electrode surface.

  A circuit board according to a second aspect of the present invention is the circuit board according to the first aspect, wherein the conductive metal thin layer of the conductive protrusion has a three-layer structure of nickel, copper and tin in order from the inner layer, nickel in order from the inner layer, It consists of a four-layer structure of copper, tin, and bismuth, and a five-layer structure of nickel, copper, tin, bismuth, and silver in order from the inner layer.

  A circuit board according to a third aspect of the present invention is the circuit board according to the first or second aspect, characterized in that the conductive protrusions are substantially spherical and have a diameter of 1 to 10 μm.

  According to a fourth aspect of the present invention, there is provided an electrode connection structure for a circuit, wherein circuit boards each having a plurality of electrodes spaced apart from each other are disposed so that the electrode surfaces face each other. There are provided a plurality of conductive protrusions having a synthetic resin as a core and a surface covered with a thin conductive metal layer having a melting point of 250 ° C. or less, and the conductive protrusions are pressed and deformed slightly flatly. The surface is melt-bonded to the surface, and no conductive fine particles are present in the space between adjacent electrodes.

  The electrode connection structure of the circuit according to the invention described in claim 5 is the electrode connection structure according to claim 4, wherein the conductive metal thin layer of the conductive protrusion is a three-layer structure of nickel, copper and tin in order from the inner layer, and the inner layer It is characterized by consisting of a four-layer structure of nickel, copper, tin, and bismuth in order, and a five-layer structure of nickel, copper, tin, bismuth, and silver in order from the inner layer.

  A circuit electrode connection structure according to a sixth aspect of the invention is characterized in that, in the invention according to the fourth or fifth aspect, the conductive protrusions are substantially spherical and have a diameter of 1 to 10 μm. Is.

Hereinafter, the present invention will be described in detail with reference to the drawings.
First, the circuit board of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing an example of a circuit board of the present invention. In FIG. 1, reference numeral 10 denotes a circuit board such as a drive circuit board, and the circuit board 10 is provided with a plurality of electrodes 11 having a constant width and a constant interval on a surface thereof. . In the figure, two electrodes 11 are shown for convenience. The electrode 11 may be a protruding electrode such as a bump.

  The circuit board 10 includes a film substrate having excellent durability such as transparency, heat resistance, and moisture resistance such as a polyester film and a polyimide film, and an electrode 11. The electrode 11 is formed of a precision wiring pattern such as gold, silver, copper, nickel, ITO or the like. The electrode 11 formed with this precision wiring pattern is formed by, for example, a PEP (Photo Engraving Process) method.

  A plurality of conductive protrusions 20 are provided on each electrode 11 of the circuit board 10. In the figure, three conductive protrusions 20 are shown for convenience. The conductive protrusion 20 has a synthetic resin core 21 and a surface covered with a thin conductive metal layer 22 having a melting point of 250 ° C. or lower and is bonded to the electrode 11 by molten metal. 30 is the molten metal joint. Here, as a method of melt-bonding the conductive protrusions 20 to one surface of the electrodes 11, conductive fine particles 20 (the same configuration as the conductive protrusions 20) that form the conductive protrusions 20 are dispersed on each electrode 11. Thereafter, a method of heating and melting the conductive metal thin layer 22 of the conductive fine particles 20 is employed.

  Specifically, a photosensitive dry film resist is laminated on the entire surface including the electrode 11 of the circuit board 10, and the resist is left in a portion other than the electrode pattern exposed as an electrode terminal by UV irradiation using a photographic film. The conductive fine particles 20 are sprayed on the entire surface and heated to melt the conductive metal thin layer 22 of the conductive fine particles 20, and the conductive fine particles 20 are melted and bonded only on the electrodes 11. The conductive fine particles adhering to portions other than the electrodes 11 of the circuit board 10 are removed when the resist is removed. By such a method, a desired number of conductive fine particles 20 can be placed on the electrode 11.

  Further, after the conductive metal thin layer 22 of the conductive fine particles 20 is melted and the conductive fine particles 20 are melted and bonded only on the electrodes 11, the conductive fine particles attached to portions other than the electrodes 11 of the circuit board 10 are removed. The resist may be removed without being removed by washing, blowing with compressed air, or sweeping with a brush. If it is such a method, since a conductive pattern is coat | covered and protected by the remaining resist except the part used as an electrode terminal, it is preferable.

  The synthetic resin serving as the core 21 of the conductive protrusion 20 needs to be able to be compressed slightly flat and to have residual elasticity (elastic recovery) when heated and pressed in face-down mounting described later. Such synthetic resins include divinylbenzene polymer, divinylbenzene-styrene copolymer, divinylbenzene-styrene copolymer, divinylbenzene-acrylate copolymer, styrene-acrylic copolymer, acrylic resin. A melamine resin, a benzoguanamine polymer, or the like is preferably used. The recovery rate after compression deformation of the conductive protrusions 20 (conductive fine particles 20) is preferably 5 to 95% at 20 ° C.

  The conductive metal thin layer 22 of the conductive protrusion 20 is a low melting point conductive metal thin layer that melts at a temperature of 250 ° C. or lower, preferably 250 to 100 ° C. When the melting point is lower than 100 ° C., the connection reliability of the circuit at a high temperature is lowered, and conversely, when the melting point is higher than 250 ° C., a high temperature is required at the time of circuit connection, thereby adversely affecting the components connected to the circuit.

  In this case, if the conductive metal thin layer 22 is composed only of a low melting point conductive metal thin layer that melts at a temperature of 250 ° C. or lower, preferably 250 to 100 ° C., it is heated during face-down mounting. Due to the pressure, the conductive metal thin layer 22 having a low melting point is melted and pushed to the periphery, and the core 21 made of the synthetic resin is exposed at the contact portion with the electrode 11, so that the conduction failure of the connection circuit is likely to occur. .

  In order to improve the above problem, the conductive metal thin layer 22 is formed by forming a high-melting-point conductive metal thin layer that does not melt and diffuse on the inside, and forming a low-melting-point conductive metal film on the outside thereof. A layer structure is preferred. As described above, when the conductive metal thin layer 22 has a multilayer structure, even if the low-melting-point conductive metal thin layer of the outer layer is melted and pushed to the periphery, the high-melting-point conductive metal thin layer that does not melt and diffuse in the inner layer is Since it does not melt, the core 21 made of synthetic resin is prevented from being exposed, and no connection circuit conduction failure occurs.

  In the present invention, in particular, as the conductive metal thin layer 22 having a melting point of 250 ° C. or less that is coated on the surface of the core 21 made of synthetic resin, a three-layer structure of nickel, copper, and tin in order from the inside, nickel in order from the inside, A four-layer structure of copper, tin and bismuth, and a five-layer structure of nickel, copper, tin, bismuth and silver in order from the inside is preferably used.

  That is, a nickel layer (melting point: 1455 ° C.) that is a high melting point conductive metal that does not melt and diffuse is used as an inner layer, and a copper layer (melting point: 1085 ° C.) is interposed as a layer that maintains adhesion, and is a low melting point conductive metal. It is preferable to form a tin layer (melting point: 232 ° C.), a bismuth layer (melting point: 270 ° C.), and a silver layer (melting point: 962 ° C.). With such a laminated structure, the thin metal layer with a low melting point is not peeled off from the thin metal layer with a high melting point that does not melt and diffuse. Further, the metals forming the low melting point metal layer are melted by heat and pressure and mixed by diffusion to form a low melting point alloy having a melting point of 100 to 250 ° C.

  As a method of covering the surface of the core 21 made of synthetic resin with the conductive metal thin layer 22, a conventionally known method is employed. For example, after supporting palladium acting as a catalyst for depositing the conductive metal layer 22 on the surface of the core 21 made of synthetic resin, this is put into various known plating solutions and subjected to electroless plating treatment. Thus, the conductive metal thin layer 22 is coated on the surface of the core 21 made of synthetic resin.

  Note that the core 21 made of the synthetic resin has a surface modified so that the surface thereof has the ability to capture palladium ions or has the ability to capture palladium ions in order to improve the adhesion of palladium ions serving as a catalyst. It is preferred that Here, having the ability to capture palladium ions means that the palladium ions can be captured as a chelate or salt. If there is an amino group, imino group, amide group, imide group, cyano group, hydroxyl group, nitrile group or carboxyl group on the surface of the synthetic resin core, it has the ability to trap noble metal ions. It is preferable to treat with the compound which has.

  Electroless plating solutions include, for example, metal salts (nickel salts, copper salts, tin salts, bismuth salts, silver salts, etc.), reducing agents (sodium hypophosphite, sodium borohydride, aminoborane, formalin, etc.), complex Conventionally known electroless plating solutions containing agents (formic acid, acetic acid, succinic acid, citric acid, tartaric acid, glycine, ethylenediamine, EDTA, triethanolamine, etc.), pH buffering agents (sulfuric acid, caustic soda, etc.) are used. .

  The conductive protrusions 20 are preferably substantially spherical, but may be elliptical or other protrusions or irregularities on the surface. When the conductive protrusion 20 is substantially spherical, a diameter of 1 to 10 μm is preferable, and a diameter of about 3 to 5 μm is more preferable. Moreover, the thickness of the conductive metal thin layer 22 is 0.02 to 5 μm in total thickness, and preferably 0.2 to 1 μm.

  In addition, after providing the some electroconductive protrusion 20 in the electrode 11 surface of the circuit board 10, you may give electroconductive metal plating on it. As this conductive metal plating, a hard metal, for example, conductive metal plating such as tin, bismuth or an alloy thereof is employed. The thickness of the conductive metal plating is preferably 0.1 to 1 μm. By performing such conductive metal plating, the molten metal bond with the counter electrode is further strengthened. Thus, the circuit board A of the present invention is obtained.

  Next, the electrode connection structure of the circuit of the present invention will be described. FIG. 2 is a schematic cross-sectional view showing an example of the electrode connection structure of the circuit of the present invention. As the electrode connection structure of this circuit, a circuit board A such as a drive circuit board shown in FIG. 1 is used, and this circuit board A is applied to a circuit board 40 provided with a wiring pattern to be a driving circuit of a liquid crystal display panel, for example. Obtained by mounting face down. The wiring pattern is provided on the outer overhanging portion of one (lower) glass substrate of the liquid crystal display panel.

  In FIG. 2, below the electrode 11 of the circuit board 10, the electrode 41 of the circuit board 40 of a liquid crystal display panel is arrange | positioned in the position which opposes. Then, between the opposing electrode 11 surface and the electrode 41 surface, the conductive protrusion 20 is formed by using the synthetic resin as a nucleus 21 and the surface thereof covered with a thin conductive metal layer 22 having a melting point of 250 ° C. or less. A plurality of (conductive fine particles 20) are provided.

  Here, the conductive protrusion 20 is molten metal bonded to the surface of each electrode 11 and the surface of the electrode 41 in a state of being pressed and deformed slightly flat. 30 is the molten metal joint. Further, the space between the electrodes is filled with an electrically insulating thermosetting resin 50. By the thermosetting resin 50 and the molten metal bonding portion 30, the conductive protrusion 20 is bonded and fixed to both the electrode 11 surface and the electrode surface 41 surface. Further, no conductive fine particles exist in the space between the adjacent electrode 11 and electrode 41. Further, a thin layer of adhesive resin is not sandwiched between the contact surface between the electrode 11 and the conductive protrusion 20 and the contact surface between the electrode 41 and the conductive protrusion 20.

  The electrode connection structure of the circuit of the present invention is configured as described above, and the electrode connection structure of such a circuit is specifically obtained by the following method. First, the circuit board A such as the drive circuit board shown in FIG. 1 is used, and the circuit board A and the circuit board 40 of the liquid crystal display panel are arranged so that the electrodes 11 and the electrodes 41 of both circuits face each other. Align under the microscope. Since the drive circuit board and the glass substrate of the liquid crystal display panel are transparent, alignment of both circuit boards is easy.

  Thereafter, a thermosetting resin liquid such as epoxy resin is injected into the space formed between the electrodes 11 and 41 of both circuit boards, and the circuit board A and the circuit board 40 of the liquid crystal display panel are pressed from above. The electrode 11 and the electrode 41 of both circuit boards are fixed by the electrically insulative thermosetting resin 50 by heating and pressing the thermosetting resin liquid. In addition, injection | pouring of the said thermosetting resin liquid is abbreviate | omitted and it can also be set as a space.

  In this case, the conductive protrusion 20 is melt-bonded to the surface of the electrode 11 and the surface of the electrode 41 in a state where the conductive protrusion 20 is pressed and deformed slightly flat by heating and pressurization, and in addition, in the space between each electrode 11 and each electrode 41 Only the thermosetting resin 50 is present, and no conductive fine particles are present. Further, a thin layer of adhesive resin is not sandwiched between the contact surface between the electrode 11 and the conductive protrusion 20 and the contact surface between the electrode 41 and the conductive protrusion 20.

A thermosetting adhesive sheet that does not contain conductive fine particles is temporarily attached between the electrodes, or a thermosetting adhesive that does not contain conductive fine particles is applied to the electrode surface, and this is heated and pressed by a press. The adhesive sheet or adhesive may be heat cured.
Alternatively, a thermosetting resin liquid such as an epoxy resin may be injected into a space formed between the electrode 11 and the electrode 41 of both the circuit boards, and the thermosetting resin liquid may be cured by heating. The method of injecting the thermosetting resin liquid is more preferable because there is no fear that a thin layer of the adhesive resin is sandwiched between the contact surfaces of the electrode 41 and the conductive protrusion 20.

  As the heating and pressurizing conditions, conditions such that the conductive protrusions 20 are slightly flattened are adopted, and the pressure is usually 50 to 100 MPa and the temperature is 160 to 250 ° C. As a heating and pressing method, heating and pressing by a press is preferable. After heating and pressing, pressurization is continued until the thermosetting resin liquid 50 is cured. Thus, the electrode connection structure B of the circuit of the present invention is obtained.

  In the circuit board of the present invention, a plurality of conductive protrusions such as conductive fine particles are fixed in advance on the electrodes of the substrate by molten metal bonding, so that the plurality of conductive protrusions necessary for electrical conduction are connected to the circuit. In the electrode connection structure of the circuit of the present invention obtained by using such a circuit board, a thermosetting resin exists in the space between adjacent electrodes. Only the conductive fine particles are not present. Further, a thin layer of adhesive resin is not sandwiched between the contact surfaces of the electrodes and the conductive protrusions. Therefore, there is no danger of short-circuiting of electrodes or poor energization, stable connection with the electrode, and excellent connection reliability with the electrode.

  Moreover, since the conductive protrusions are melted and bonded to the opposing electrode surfaces in a state of being slightly flattened and deformed, a sufficiently low contact resistance is obtained with a sufficiently large contact area, and the conductive protrusions are electrodes. Good conductivity can be obtained without peeling from the surface.

  Specific examples of the present invention will be given below. The present invention is not limited to these examples.

(Nickel plating pretreatment)
Synthetic resin fine particles made of divinylbenzene resin having an average particle diameter of 4 μm were dispersed in an acidic aqueous solution of palladium chloride and treated with a reducing agent, thereby attaching palladium metal. Note that palladium chloride-stannic chloride or palladium sulfate may be used instead of palladium chloride.

(Formation of nickel-plated thin layer)
Synthetic resin fine particles to which the palladium metal is attached are dispersed in a predetermined reaction layer, and a nickel salt, a reducing agent (hypophosphite), a complexing agent, a stabilizer, a pH adjusting agent, and a buffering agent are contained therein. A nickel metal thin layer of 0.1 μm was coated by dropping a plating solution and reacting it.

(Pretreatment of copper plating)
The resulting nickel-plated fine particles were dispersed in an acidic aqueous solution of palladium chloride and treated with a reducing agent, thereby depositing palladium metal. Note that palladium chloride-stannic chloride or palladium sulfate may be used instead of palladium chloride.

(Copper plating thin layer formation)
Synthetic resin fine particles on which the nickel plating thin layer is formed are dispersed in a predetermined reaction layer, and a plating solution containing a copper salt, a reducing agent (formalin), a complexing agent, a stabilizer, a pH adjusting agent, and a buffering agent. Was dropped and reacted to coat a 0.1 μm-thick copper plating thin layer.

(Formation of tin-plated thin layer)
In order to advance the reduction tin plating reaction, the substitution tin plating was coated as an ultra-thin layer and catalyzed. As a method of catalyzing, the synthetic resin fine particles forming the copper plating thin layer are dispersed in a solution containing a tin salt, a reducing agent (thiourea), a complexing agent, a PH adjusting agent, and a crystal adjusting agent. A 0.02 μm tin-plated thin layer was formed. Thereafter, a tin plating thin layer of 0.2 μm was further coated by adding a plating solution comprising a tin salt, titanium chloride, a complexing agent, a stabilizer, and a crystal modifier.

(Formation of thin bismuth plating layer)
Synthetic resin fine particles on which the tin plating thin layer is formed are dispersed in a predetermined reaction layer, and this contains a bismuth salt, a reducing agent (tin chloride), a complexing agent, a crystal adjusting agent, a PH adjusting agent, and a stabilizer. A thin bismuth plating layer of 0.12 μm was coated by dropping the plating solution and reacting it.

(Formation of silver-plated thin layer)
Synthetic resin fine particles forming the bismuth plating thin layer are dispersed in a predetermined reaction layer and dispersed in a plating solution containing a silver salt, a reducing agent (glyoxylic acid, imidazole), a complexing agent, and a crystal modifier. A 0.02 μm silver plating thin layer was coated.

(Preparation of conductive fine particles)
The conductive fine particles having the five conductive metal thin layers thus obtained were heated at 200 ° C. for 2 minutes to diffuse the metal and form a low melting point alloy layer that melted at about 150 ° C. Thus, conductive fine particles having a synthetic resin as a core and a surface covered with a thin conductive metal layer having a melting point of 250 ° C. or less were obtained. The obtained conductive fine particles had a 10% compression modulus (20 ° C.) of 490 N / mm ² .

(Circuit board creation)
Using the obtained conductive fine particles, a photosensitive dry film resist is laminated on a flexible printed wiring board (FPC) having a 10 μm line and space in which electrode patterns are formed at intervals of 5 μm, and a photographic film is used. Then, the portion where the conductive fine particles are to be avoided is cured by UV exposure, and then the resist is peeled off using a sodium carbonate solution to expose only the portion where the conductive fine particles are desired to be disposed. Thereafter, the conductive fine particles were adhered to the exposed part by spraying, and the conductive fine particles were fused and bonded to the electrodes by heating. Thereafter, the resist at the cured portion was also peeled off to obtain the circuit board of the present invention.

(Production of circuit electrode connection structure)
Using a circuit board made of the flexible printed wiring board (FPC) and a transparent conductive glass (indium oxide circuit, glass thickness 1 mm) having electrodes of the same wiring pattern as the electrodes of the circuit board, both circuits under a microscope Was aligned. Thereafter, a thermosetting resin liquid composed of an epoxy resin and a curing agent is injected into the space formed between the electrodes of both circuit boards, and thermosetting is performed by heating and pressing at 180 ° C. and 100 MPa for 30 seconds. The circuit was connected by curing the resin liquid to obtain the electrode connection structure of the circuit of the present invention.

  In this case, the conductive fine particles are melt-bonded to the electrode surface in a state where they are pressed and deformed slightly flat, and the conductive fine particles are present only in the space between the adjacent electrodes. I did not. Moreover, the thin layer of adhesive resin was not pinched | interposed into the contact surface of each electrode and electroconductive fine particles.

(Comparative Example 1)
Example 1 was applied to a rubber-modified flexible epoxy resin, a microcapsule-type latent curing agent (activation temperature: 120 ° C.), and an adhesive (nonvolatile content: 50%) mainly composed of toluene solvent (nonvolatile content: 50%). The adhesive formed by adding 20% by volume of the conductive fine particles obtained in the above was applied onto a separator (tetrafluoroethylene film) and dried to form a thin sheet. This thin sheet was heated to 150 ° C. to prepare an anisotropic conductive adhesive sheet (with a separator) in which conductive fine particles were dispersed.

  Next, the anisotropic conductive adhesive sheet (with a separator) is placed at 130 ° C. on the electrode surface of a flexible printed wiring board (FPC) having a 10 μm line and space in which electrode patterns are formed at intervals of 5 μm as in Example 1. After temporarily pressing in 10 seconds, the separator is peeled off, and the electrode surface of transparent conductive glass is overlapped with this to align with the counter electrode, and this is heated and pressurized at 180 ° C. and 100 MPa for 30 seconds to anisotropically conductive bond The sheet was cured. Thus, an electrode connection structure of a circuit was obtained in which the flexible printed wiring board (FPC) and the transparent conductive glass were connected so as to be electrically conductive.

(Comparative Example 2)
Based on the plating method described in Patent Document 1 and Patent Document 2 (Japanese Patent Laid-Open Nos. 2003-59959 and 2004-214375), a flexible printed wiring board on which electrodes are formed is immersed in a plating solution in which particles are dispersed. At the same time as plating on the electrode, the particles were deposited on the electrode and the particles were placed only on the electrode, and then a thermosetting resin was pasted to align the upper and lower electrodes. This was heated and pressurized at 180 ° C. and 100 MPa for 30 seconds to lower the anisotropic conductive adhesive sheet. Thus, an electrode connection structure of a circuit was obtained in which the flexible printed wiring board (FPC) and the transparent conductive glass were connected so as to be electrically conductive.

(Evaluation)
The electrode connection structure of the circuit obtained in Example 1 and Comparative Examples 1 and 2 was left in a high temperature and high humidity of 180 ° C. and 85% for 1000 hours and alternately immersed in −40 ° C. and + 120 ° C. at regular intervals. When the connection resistance value and the insulation resistance value before and after this reliability test were measured, there was no increase in the resistance value between the opposing electrodes, and no deterioration in the insulation resistance value between adjacent electrodes was observed. From this result, in Example 1, it can be seen that different electrodes are not connected to each other and short-circuited, a sufficiently low connection resistance is obtained, a stable connection with the electrode can be obtained, and the connection reliability is extremely excellent. It was.

  On the other hand, in Comparative Example 1, a short circuit due to a leakage current was observed between adjacent electrodes. In Comparative Example 2, both the upper and lower electrodes are not metal-bonded, but are metal-bonded only on one side, so that the connection reliability is inferior to that of Example 1 in all cases.

It is a cross-sectional schematic diagram which shows an example of the circuit board of this invention. It is a cross-sectional schematic diagram which shows an example of the electrode connection structure of the circuit of this invention.

Explanation of symbols

A Circuit board of the present invention B Electrode connection structure of circuit of the present invention 10 Drive circuit board 11 Electrode of drive circuit board 20 Conductive protrusion (conductive fine particles)
21 Core made of synthetic resin 22 Conductive metal thin layer 30 Molten metal bonding part 40 Circuit board of liquid crystal display panel 41 Electrode of circuit board of liquid crystal display panel 50 Electrical insulating thermosetting resin

Claims (6)

  A plurality of conductive protrusions are provided on the electrode surface of the circuit board on which a plurality of electrodes are provided at intervals, and the plurality of conductive protrusions have a synthetic resin as a core and the surface has a melting point of 250 ° C. or lower. A circuit board which is covered with a thin metal layer and is bonded to a molten metal on the electrode surface.   The conductive metal thin layer of the conductive protrusion has a three-layer structure of nickel, copper and tin in order from the inner layer, a four-layer structure of nickel, copper, tin and bismuth in order from the inner layer, nickel, copper, tin, bismuth in order from the inner layer, The circuit board according to claim 1, wherein the circuit board is made of any one of five layers of silver.   The circuit board according to claim 1, wherein the conductive protrusion has a substantially spherical shape and a diameter of 1 to 10 μm.   Circuit boards provided with a plurality of electrodes spaced apart are arranged with the electrode surfaces facing each other, and a conductive metal having a synthetic resin as a core between the facing electrode surfaces and a melting point of 250 ° C. or lower. A plurality of conductive protrusions covered with a thin layer are provided, and the conductive protrusions are melt-bonded to the electrode surface in a state where they are pressed and deformed slightly flatly. Circuit electrode connection structure, characterized in that no conductive fine particles are present.   The conductive metal thin layer of the conductive protrusion has a three-layer structure of nickel, copper and tin in order from the inner layer side, a four-layer structure of nickel, copper, tin and bismuth in order from the inner layer, and nickel, copper, tin and bismuth in order from the inner layer. 5. The electrode connection structure for a circuit according to claim 4, wherein the electrode connection structure is made of any one of five layers of silver. 6. The electrode connection structure for a circuit according to claim 4, wherein the conductive protrusion is substantially spherical and has a diameter of 1 to 10 [mu] m.

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