Production method of anisotropic conductive connector

Abstract

The present invention aims at providing a production method capable of efficiently producing an anisotropic conductive connector having a structure wherein the center line of plural conductive paths penetrating in the thickness direction of a film substrate forms an angle with a line perpendicular to the principal plane of the film substrate, which shows high reliability of connection with the target. The present invention is characterized in that an insulating film and a conductive wire are integrated on a core, the resulting roll-like product is removed from the core, which is opened to give a plane-like product, plural films with conductive wires 10A are cut out from the plane-like product, then the plural films with conductive wires are accumulated such that the conductive wires 2 of the adjacent films are in parallel relation with each other, the obtained laminate is heated and pressurized and the obtained block is cut in a predetermined film thickness along the plane forming an angle with the conductive wire 2.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to a production method of an anisotropic conductive connector. More particularly, the present invention relates to a production method of an anisotropic conductive connector having a structure wherein a conductive path penetrating in the thickness direction of a film substrate has an inclination.

BACKGROUND OF THE INVENTION

[0002] For an electrical connection between an electronic component such as a semiconductor element (IC chip) and the like and a circuit board, an anisotropic conductive connector has been widely used in recent years. As an anisotropic conductive connector, one prepared by dispersing conductive fine particles in an insulating film has been conventionally known. This anisotropic conductive connector is associated with problems of structurally difficult connection with a connection target having a fine pitch and the need for forming a terminal of the target, such as electrode of semiconductor element and the like in a protrusion (bump). Thus, as an anisotropic conductive connector capable of resolving such problems, namely, an anisotropic conductive connector capable of dealing with finely pitched and bumpless target, the Applicant of this invention has proposed an anisotropic conductive connector (film) comprising, in the substrate of an insulating film, plural conductive paths penetrating in the thickness direction of the film substrate while being insulated from each other, in international publication WO98/07216 (U.S. Pat. No. 6,245,175).

[0003] Generally, anisotropic conductive connectors are being used for the following two uses. One is use for, what is called, mounting connectors, wherein an anisotropic conductive connector is disposed between an electronic component such as a semiconductor element and the like and a circuit board, which, upon heating and pressurizing, electrically and mechanically connects the electronic component and the circuit board. The other is use as, what is called, a test connector, wherein, in functional tests of electronic components such as semiconductor element and the like, an anisotropic conductive connector is inserted between an electronic component and a circuit board, which, upon press adhesion to the both, achieves a functionally testable conduction between the electronic component and the circuit board.

[0004] The use of an anisotropic conductive connector as a test connector is necessary because a functional test of an electronic component after mounting the electronic component on a circuit board to prove the electronic component to be defective results in disposal of a good circuit board together with the component, thereby lowering the production efficiency of the circuit board and increasing an economical loss.

[0005] In a test of electronic component such as semiconductor element and the like, damage of terminal and deformation of the terminal are prevented only when an anisotropic conductive connector is brought into contact with an electronic component and a circuit board at a lower pressure. The Applicant has proposed, in the above-mentioned international publication WO98/07216, an anisotropic conductive connector having a structure wherein plural conductive paths penetrating a film substrate in the thickness direction thereof are disposed such that the center line thereof form an angle with the line perpendicular to the principal plane of the film substrate. In other words, by imparting an inclination in a given direction to plural conductive paths penetrating in the thickness direction of a film substrate, the conductive path bends and the pressure applied on the electronic component and circuit board is decreased, when an electronic component is placed on the circuit board via an anisotropic conductive connector and the electronic component is pressed from above.

[0006] Such anisotropic conductive connector has been conventionally manufactured according to the method described in the above-mentioned international publication WO98/07216. To be specific, an insulated conductive wire (metal wire coated with insulating resin layer) is wound multiple times around a core, coating layers are bonded to prevent separation from each other to give a winding block, and this block is cut in a desired thickness along the plane forming an angle with each insulated conductive wire (metal wire). However, such conventional production methods require multiple winding of an insulated conductive wire, which makes it difficult to make the winding direction of insulated conductive wires (metal wires) uniform in a given direction in the winding block. This in turn prevents uniform direction of inclination of plural conductive paths in an anisotropic conductive connector obtained by cutting the winding block. Thus, the conductive paths bend in various directions upon pressing the anisotropic conductive connector, which increases difference (less uniformity) in the contact pressure with the target (circuit board, semiconductor element etc.) in the anisotropic conductive connector, which, in some cases, results in lower connection reliability with the target. In addition, when the winding block is to be cut, a cutting plane is set such that an insulated conductive wire (metal wire) forms an angle with the line perpendicular to the cutting plane (or setting the center line of a block at an angle with respect to the cutter) and the block is cut. By cutting the block in this way, plural anisotropic conductive connector films obtained by cutting have various sizes, requiring post-processing to unify the film size. Accordingly, an anisotropic conductive connector having a desired size cannot be produced efficiently, thus posing a problem.

[0007] In view of the above-mentioned situation, the present invention aims at providing a production method for efficiently producing an anisotropic conductive connector having a structure wherein the center line of plural conductive paths that penetrate in the thickness direction of a film substrate form an angle with the line perpendicular to the principal plane of the film substrate, which shows small variation in the direction of inclination (bending direction of conductive paths) among plural conductive paths, and which has high reliability of connection with a target.

[0008] In addition, the present invention aims at providing a production method for efficiently producing an anisotropic conductive connector which shows small variation in the direction of inclination (bending direction of conductive paths) among plural conductive paths, and which has high reliability of connection with a target, in a desired film size.

SUMMARY OF THE INVENTION

[0009] With the aims of achieving the above-mentioned objects, the present invention has the following characteristics. (1) A method of producing an anisotropic conductive connector having a structure wherein the center line of plural conductive paths penetrating in the thickness direction of a film substrate forms an angle with a line perpendicular to the principal plane of the film substrate, which comprises the steps of

[0010] winding an insulating film around the circumference of a core,

[0011] then helically winding a conductive wire around the circumference of the insulating film at a predetermined pitch, or helically winding a conductive wire around the circumference of the core,

[0012] then winding the insulating film to cover the conductive wire,

[0013] heating and pressurizing to integrate the insulating film and the conductive wire on the core to give a roll-like product,

[0014] removing the aforementioned roll-like product from the core,

[0015] incising the product to give a plane-like product,

[0016] cutting out plural films with conductive wires from the plane-like product,

[0017] then laminating the plural films with conductive wires such that the conductive wires on the adjacent films are parallel to each other to give a laminate,

[0018] heating and pressurizing the laminate to form a block integrating the plural films with conductive wires, and

[0019] then cutting the block in a predetermined film thickness along the plane forming an angle with the conductive wire to give an anisotropic conductive connector.

[0020] (2) The production method of the above-mentioned (1), wherein the plural films with conductive wires are cut out in such a manner that the principal plane of the insulating film has a linear side and the center line of the plural conductive wires forms a predetermined inclination angle with a linear side, the plural films with conductive wires are laminated such that the linear sides of the adjacent insulating films are in parallel relation, thereby forming a laminate, and a block obtained from the laminate is cut in a predetermined film thickness along the plane perpendicular to a linear edge side thereof derived from the linear side of the principal plane of the insulating film. (3) The production method of the above-mentioned (1) or (2), wherein the insulating film and the conductive wires wound around the core are set together with the core in a space permitting formation of a decompression or vacuum and, after decompressing or vacuumizing the space, heated and pressurized to integrate the insulating film and the conductive wire on the core.

[0021] (4) The production method of the above-mentioned (3), wherein the aforementioned space permitting formation of a decompression or vacuum is an inner space of a bag made of a flexible film.

[0022] (5) The production method of the above-mentioned (3) or (4), wherein the aforementioned pressing is done by introducing a compressed air into the aforementioned space permitting formation of a decompression or vacuum.

[0023] (6) The production method of any of the above-mentioned (1) to (5), wherein the laminate is set in the space permitting formation of a decompression or vacuum, and after decompressing or vacuumizing the space, heated and pressurized.

[0024] (7) The production method of the above-mentioned (6), wherein the space permitting formation of a decompression or vacuum is an inner space of a bag made of a flexible film.

[0025] (8) The production method of the above-mentioned (6), wherein the laminate is housed in a heat resistant box having a size leaving some clearance between the inside surface of the box and the lateral surface of the laminate upon accommodation of the laminate, set in the space inside the bag made of a flexible film together with the heat resistant box, and after decompressing or vacuumizing the space, heated and pressurized.

[0026] In the present specification, the “principal plane of film substrate” means the surfaces of the both ends in the thickness direction of a film substrate, and the “principal plane of the insulating film” means the surfaces of the both ends in the thickness direction of an insulating film. A reference to “a surface of a film substrate” and “a surface of an insulating film” means “the principal plane of a film substrate” and “the principal plane of an insulating film”, unless particularly specified.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a perspective view (FIG. 1(a)) of winding an insulating film around a core in step 1 of the present invention, and a perspective view (FIG. 1(b)) of a wound product obtained by such step.

[0028] FIG. 2 is a plane view of a plane-like product obtained by developing a roll-like product integrating insulating films and conductive wires.

[0029] FIG. 3(a) and FIG. 3(b) are plane views of plural films with conductive wires obtained by cutting the plane-like product.

[0030] FIG. 4 includes a perspective view (FIG. 4(a)), a sectional view (FIG. 4(b)) and a plane view (FIG. 4(c)) of a film with conductive wires.

[0031] FIG. 5 is a perspective view showing an accumulation work of films with conductive wires (FIG. 4).

[0032] FIG. 6 is a perspective view of a laminate obtained by accumulating films with conductive wires (FIG. 4).

[0033] FIG. 7 is a perspective view of a block integrating laminate (FIG. 6) by heating and pressurizing.

[0034] FIG. 8 is a perspective view of a step of cutting a film from the block (FIG. 7).

[0035] FIG. 9 is a perspective view of a step of placing a laminate (FIG. 6) into a heat resistant box.

[0036] FIG. 10 is a perspective view of a state wherein the laminate (FIG. 6) is housed in the heat resistant box.

[0037] FIG. 11 is a plane view (FIG. 11(a)) and a sectional view (FIG. 11(b)) of the anisotropic conductive connector produced by the present invention.

[0038] In the Figures, the symbol 1 shows an insulating film, the symbol 1a shows the principal plane of the insulating film, the symbol 2 shows a conductive wire, the symbol L1 shows the center line of a conductive wire, the symbol L2 shows the linear side, the symbol &agr;1 shows an inclination angle, and the symbol 10A and the symbol 10B show a film with conductive wires.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The present invention is explained in detail in the following by referring to the drawings.

[0040] The anisotropic conductive connector produced by the present invention is shown in FIG. 11(a) and FIG. 11(b), which is an anisotropic conductive connector 60 having a structure wherein plural conductive paths 51 penetrating in the thickness direction (direction of arrow A in FIG. 11(b)) of a film substrate 50 are set such that the center line L10 thereof forms an angle (&agr;) with the line L20 perpendicular to the principal plane 50a (and 50b) of the film substrate 50. Here, FIG. 11(a) is a plane view and FIG. 11(b) is a sectional view along the line XIb-XIb in FIG. 11(a). In the Figures, D1 and D2 are pitches of the conductive paths 51 in the first and second perpendicular directions (direction of arrow X and the direction of arrow Y of principal plane 50a of film substrate 50) in the anisotropic conductive connector.

[0041] The angle (&agr;) formed by (the center line L10 of) the plural conductive paths 51 with the line L20 perpendicular to the principal plane 50a of the film substrate 50 is preferably not less than 5 degrees so that an effect of reducing the pressure to a target (electronic component, circuit board etc.) due to the bending of the conductive path 51 can be sufficiently afforded. When the angle is too large, positional adjustment (offset) with two targets (e.g., electronic component and circuit board) to be electrically connected is necessary. Thus, the angle is preferably not more than 45 degrees.

[0042] The anisotropic conductive connector produced by the present invention is particularly preferable as a test connector, wherein the thickness of the film substrate 50 is generally about 20-1000 &mgr;m, preferably about 50-500 &mgr;m. The sectional shape of the conductive path (perpendicular to the center line L10) may be circle, polygon or any other shape and is free of any particular limitation. In view of the reliability of connection with the target (terminal), it is preferably a circle. The diameter (width) thereof is preferably about 10-80 &mgr;m, particularly preferably about 12-60 &mgr;m, when the sectional shape is circle, and when the sectional shape is polygon or any other shape, such a diameter (width) as makes the sectional area thereof corresponding to the area of a circle having a diameter within the above-mentioned scope, in view of the reliability of connection with the target (terminal), conductivity (impedance) of the conductive path itself and the like. The pitches in the conductive path 51 (D1 and D2 in the Figures) are each generally preferably 20-200 &mgr;m, particularly preferably 20-150 &mgr;m, from the reliability of connection with a target (terminal) and deformability (flexibility) of the anisotropic conductive connector.

[0043] The present invention relates to a method of producing an anisotropic conductive connector 60 having a structure wherein (the center line L10 of) plural conductive paths 51 is set to form an angle with the line L20 perpendicular to the principal plane 50a of the film substrate 50 (a structure wherein plural conductive paths penetrate in the thickness direction of a film substrate and the plural conductive paths are inclined in a predetermined direction at a predetermined angle). Basically, it includes Step 1 (step for forming plural-films with conductive wires), Step 2 (step for forming a block integrating plural films with conductive wires) and Step 3 (block cutting step) to be explained in the following.

Step 1 (Step for Forming Plural Films with Conductive Wires)

[0044] As shown in FIG. 1(a), an insulating film 1 is wound around the circumference of a core 4, then one conductive wire 2 is helically wound at a predetermined pitch around the circumference of insulating film 1 (or conversely, one conductive wire 2 is helically wound at a predetermined pitch around the circumference of a core 4, and then an insulating film 1 is wound to cover the conductive wire 2) to form a wound product 5 (FIG. 1(b)). The winding here can be done using a known winding machine such as a horizontal type regularly winding machine and the like. Then the wound product 5 (FIG. 1(b)) is heated and pressurized to integrate the insulating film 1 and the conductive wire 2 on the core 4 to give a roll-like product. Then the roll-like product integrating the insulating film 1 and the conductive wire 2 is removed from the core 4, a part of the roll-like product is cut to open into a plane-like product 6 (FIG. 2), which is then cut to give plural films with conductive wires.

[0045] FIG. 3(a) and FIG. 3(b) show embodiment of the plural films with conductive wires. The film with conductive wires 10A shown in FIG. 3(a) is cut out from the plane-like product 6 (FIG. 2) such that the principal plane 1a of the insulating film 1 is rectangular, and the direction of (the center line of) the conductive wire 2 has an inclination toward the predetermined one side (linear side) of the rectangular principal plane 1a of the insulating film 1, and a film with conductive wires 10B of FIG. 3(b) is cut out from the plane-like product 6 (FIG. 2) such that the principal plane la of the insulating film 1 is rectangular and the direction of (the center line of) the conductive wire 2 is parallel and perpendicular to the sides (4 sides) of the rectangular principal plane 1a of the insulating film 1. The double-dotted line in FIG. 2 shows the cutting line of the film with conductive wires 10A of FIG. 3(a).

[0046] The film with conductive wires 10A of the above-mentioned FIG. 3(a) intends to previously set the angle (&agr;) formed by (the center line L10 of) the conductive path 51 with the line L20 perpendicular to the principal plane 50a of the film substrate 50 in the anisotropic conductive connector 60 (FIG. 11) to be finally produced by defining the inclination angle (inclination angle (&agr;1) relative to the predetermined linear side in the principal plane 1a of the insulating film 1) of (the center line of) the conductive wire 2 in the film with conductive wires 10A. By the use of the film with conductive wires 10A, anisotropic conductive connector 60 (FIG. 11) wherein plural conductive paths 51 are inclined at an angle (&agr;), can be obtained by merely cutting the block along the plane perpendicular to the predetermined linear edge side (one side derived from the linear side of the principal plane 1a of the insulating film 1) in a later Step 3 (step for cutting the block integrating plural films with conductive wires).

[0047] In contrast, when a film with conductive wires 10B of FIG. 3(b) is used, an anisotropic conductive connector 60 (FIG. 11), wherein plural conductive paths 51 are inclined at an angle &agr;, can be obtained by setting a cutting plane such that (the center line of) the conductive wire 2 forms the aforementioned angle (&agr;) with the line perpendicular to cutting plane, when cutting the block in a later Step 3.

[0048] FIG. 4 is an enlarged view of the above-mentioned film with conductive wires 10A (FIG. 4(a) is a perspective view, FIG. 4(b) is a sectional view and FIG.4 (c) is a plane view). In the film with conductive wires 10A, plural conductive wires 2 arranged in parallel to each other at a predetermined pitch (d2) are adhered onto the rectangular principal plane 1a of the insulating film 1, and (each center line L1 of) the plural conductive wires 2 form a predetermined inclination angle (&agr;1) with the predetermined linear side L2 of the principal plane 1a of the insulating film 1, and are positioned in parallel to the principal plane 1a. As used herein, by the “form a predetermined inclination angle (&agr;1)” is meant that the center line L1 of the conductive wire and the linear side L2 cross at the predetermined acute angle (&agr;1) as shown in FIG. 4(c) (i.e., not perpendicular intersection or parallel), when the principal plane 1a of the insulating film is seen from the vertical above. The predetermined inclination angle (&agr;1) is, as explained above, corresponds to the angle (&agr;) formed by (the center line L10 of) the conductive path 51 with the line L20 perpendicular to the principal plane 50a (50b) of the film substrate 50 in the anisotropic conductive connector (FIG. 11) to be produced.

[0049] The insulating film 1 constitutes the film substrate 50 of the anisotropic conductive connector 60 (FIG. 11). Accordingly, the material of the insulating film 1 is a known material conventionally used for a film substrate of anisotropic conductive connectors. That is, a material that shows adhesive property as it is, or a material that does not show an adhesive property as it is but is capable of adhesion by at least pressurizing or heating. Examples thereof include thermoplastic or thermosetting resins such as thermoplastic polyimide resin, epoxy resin, polyetherimide resin, polyamide resin, silicone resin, phenoxy resin, acrylic resin, polycarbodiimide resin, fluorocarbon resin, polyester resin, polyurethane resin and the like; thermoplastic elastomers such as thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, thermoplastic polyamide elastomer and the like; and the like. These resins and elastomers may be used alone or in combination of two or more kinds thereof. These resins and elastomers may contain various materials such as filler, plasticizer and rubber material. Examples of the filler include SiO2 and Al2O3, examples of the plasticizer include TCP (tricresyl phosphate) and DOP (dioctyl phthalate), examples of the rubber material include NBS (acrylonitrile-butadiene rubber), SBS (polystyrene-polybutylene-polystyrene) and the like.

[0050] The thickness of the insulating film 1 is a major factor that determines the pitch of one direction (pitch (D1) in the first direction in FIG. 11) in the film substrate of the conductive path of the anisotropic conductive connector, which is generally about 20-200 &mgr;m, preferably about 20-150 &mgr;m.

[0051] The conductive wire 2 constitutes the conductive path 51 of the anisotropic conductive connector 60 (FIG. 11). For the conductive wire 2, a wire-like product made of a conductive 15 material, or a wire-like product made of a conductive material, which is coated with an insulating material and which is what is called an insulated conductive wire, is used. As the wire-like product made of a conductive material, a metal wire made of at least one kind of metal (including alloy) selected from gold, copper, aluminum, stainless steel, nickel and the like is used in view of the electric conductivity, and when an insulated conductive wire is used, the material used for coating is exemplified by those shown as examples of the materials of the above-mentioned insulating film 1.

[0052] The sectional shape of the wire-like product made of a conductive material corresponds to the sectional shape of the aforementioned conductive path and may be circle, polygon or any other shape and is not particularly limited. However, circle is preferable. The diameter (width) of the wire-like product corresponds to the diameter (width) of the aforementioned conductive path. When the sectional shape is circle, the diameter is preferably about 10-80 &mgr;m, particularly preferably about 12-60 &mgr;m. When the sectional shape is polygon or any other shape, the sectional area is preferably the same as the area of the circle having a diameter in the above-mentioned range. The thickness of the insulating coating when an insulated conductive wire is used is generally about 0.5-10 &mgr;m, preferably about 1-5 &mgr;m, in view of the ensured insulation property between conductors (wire-like products), adhesion to an insulating film, handling property of the insulated conductive wire (workability of winding to be mentioned below) and the like.

[0053] The positional intervals (pitch (d2) in FIG. 4(b) and FIG. 4(c)) between conductive wires 2 on the principal plane la of the insulating film 1 of a film with conductive wires corresponds to the pitch between adjacent conductive paths (pitch (D2) in the second direction in FIG. 11) in the film substrate in the conductive path in the anisotropic conductive connector 60 (FIG. 11), and determined as appropriate within the range of the aforementioned D2.

[0054] The heating temperature and applied pressure for heating and pressurizing for integrating the insulating film 1 and the conductive wire 2 on the core 4 in Step 1 vary depending on the material constituting the conductive wire 2 and insulating film 1 (when an insulated conductive wire is used as a conductive wire 2, the conductive wire 2 easily adheres to the insulating film 1). The heating temperature is generally about 50-250° C., preferably about 100-200° C. The applied pressure is generally about 2-30 kgf/cm2, preferably about 3-20 kgf/cm2.

[0055] It is preferable to wind an insulating film 1 and a conductive wire 2 around the core 4 to give a wound product 5 (FIG. 1(b)), which is placed as it is (namely, insulating film 1 and conductive wire 2 together with the core 4) in a space permitting formation of a decompression or vacuum, and after decompressing or vacuumizing the space, heated and pressurized. That is, by placing the wound product 5 (FIG. 1(b)) under decompression or in vacuo before heating and pressurizing, the gap among core 4, insulating film 1 and conductive wire 2 can be effectively decreased, which in turn improves the durability (retention of the conductive paths) of the produced anisotropic conductive connector. As used herein, the decompression means a pressure smaller than the atmospheric pressure and is generally not more than 0.06 MPa, and vacuum means decompression particularly to the pressure of not more than 0.001 MPa. For efficient removal of the gap, the heating and pressurizing is more preferably applied in vacuo. While the method for decompression or vacuumization is not particularly limited, suction using a pump (vacuum pump) is preferable for workability.

[0056] The above-mentioned space permitting formation of a decompression or vacuum is, for example, the space inside a rigid bag (i.e., box having rigidity capable of retaining the shape without deformation when decompressed or vacuumized), the space inside a bag made of a flexible film and the like. The material of the rigid box is, for example, metals such as steel, aluminum, stainless steel, carbon steel, bronze and the like, plastic such as polyethylene, polyurethane, acrylic resin, polyamide, polycarbonate and the like, and the like. As the flexible film, a metal film such as aluminum and the like, plastic film such as nylon film, polyester film, polyethylene film, polyimide film and the like or a laminate film wherein an aluminum film and the like are laminated on a polyethylene film and the like, and the like can be used.

[0057] When a bag made of a flexible film is used and the space inside the bag is vacuumized, the bag closely adheres to the wound product 5, whereby more effectively removing the gap.

[0058] In pressurizing for achieving the heating and pressurizing, a uniform pressure is preferably applied to a core so that the winding state (pitch, winding direction etc.) of the conductive wire may not be disturbed. For this reason, a method including introducing a compressed air into the above-mentioned space (space permitting formation of a decompression or vacuum) is preferably employed. In the case of the method including introduction of compressed air, the use of an inert gas such as nitrogen gas and the like as the compressed air preferably enables suppression of oxidization of the conductive wire.

Step 2 (Step for Forming a Block Integrating Plural Films with Conductive Wires)

[0059] In the Step 2, plural films with conductive wires, which have been prepared in the aforementioned Step 1, are layered such that the conductive wires 2 of the adjacent films are in parallel relation to give a laminate, which is then heated and pressurized to form a block integrating plural films with conductive wires. The heating and pressurizing is a treatment for welding at least an insulating film with a conductive wire between adjacent films with conductive wires. Preferably, the insulating film is welded with the conductive wires and heating and pressurizing are applied to weld-adhering the insulating films.

[0060] In the above-mentioned heating and pressurizing treatment, the heating temperature is generally within the range of from the softening temperature of resin (elastomer) constituting the insulating film to about 300° C. (specifically, 50-300° C.). When a thermosetting resin is used as the insulating film 1, heating at a temperature lower than the setting temperature is preferable. The applied pressure is generally about 0.49-2.94 MPa, preferably about 0.49-1.96 MPa.

[0061] FIG. 5-FIG. 7 show a manner wherein films with conductive wires 10A (FIG. 3(a), FIG. 4), wherein (the center line L1 of) the aforementioned plural conductive wires 2 are inclined at an angle (&agr;1) with the predetermined linear side L2 of the principal plane 1a of the insulating film 1, are accumulated (FIG. 5), such that the linear sides L2 of the adjacent insulating films 1 are in parallel relation, and the thus-obtained laminate 20 (FIG. 6) is subjected to heating and pressurizing to form a block 30 (FIG. 7).

[0062] In the present invention, plural films with conductive wires 10A are integrated in Step 2, and a block 30 having a structure wherein an insulating resin R is disposed between plural conductive wires 2 provided in parallel to each other in the vertical (direction of accumulation) and horizontal direction is formed, as shown in FIG. 7.

[0063] In the block, the interval of the conductive wire 2 (d1 in FIG. 7) with regard to the direction (direction of arrow B2 in FIG. 7) corresponding to the direction of accumulation (direction of arrow B1 in FIG. 6) of the films with conductive wires 10A corresponds to the pitch in one direction (pitch (D1) in first direction in FIG. 11) in the film substrate of the conductive path 51 of the anisotropic conductive connector 60 (FIG. 11). That is, the pitch (D1 in FIG. 11) in one direction (first direction) in the film substrate of the conductive path 51 of the anisotropic conductive connector 60 (FIG. 11) is determined according to the thickness of the insulating film 1 (total of the thickness of the insulating film 1 and the thickness of the coating layer due to the insulating resin of the insulated conductive wire when insulated conductive wire is used as the conductive wire 2) and the conditions of heating and pressurizing treatment in Step 2 (temperature, pressure).

[0064] In Step 2, a laminate comprising plural films with conductive wires is heated and pressurized to give a block integrating plural films with conductive wires. In Step 2, too, in the same manner as in the above-mentioned step 1, prior to heating and pressurizing, a laminate comprising plural films with conductive wires is preferably set in a space permitting formation of a decompression or vacuum and after decompressing or vacuumizing the space, heated and pressurized. In this way, the gap between films with conductive wires vertically laminated can be removed, and when the gap remains in a film with conductive wires, such gap can be preferably removed. As used herein, the decompress and vacuum mean the same as in the aforementioned step 1, and as the space permitting formation of a decompression or vacuum, the space inside the aforementioned rigid box or the space inside a bag made of a flexible film can be used. The method for achieving decompression or vacuum is not particularly limited but the aforementioned suction using a pump is preferable from the workability. In Step 2, a bag made of a flexible film is preferably used to achieve decompression or vacuum, in the same manner as in the aforementioned Step 1. When a bag made of a flexible film is used, the bag closely adheres to the laminate upon vacuumization of the space inside the bag, and the gap between the accumulated films with conductive wires can be more effectively removed.

[0065] More preferable results can be obtained when the heating and pressurizing treatment in Step 2 is conducted in the following manner. That is, as shown in FIGS. 9 and 10, laminate 20 is housed in a box 40, which is a heat resistant box having a size leaving some clearance between the inside surface and the laminate 20 upon accommodation of the laminate 20 and an opening 41 for entry of the laminate 20, and in this state (as shown in FIG. 10), laminate 20 is set in the space inside the aforementioned bag made of a flexible film together with the heat resistant box 40, and after decompressing or vacuumizing the space, heated and pressurized. In this way, the plural films with conductive wires 10A constituting the laminate 20 can be prevented from being out of position during pressing and the direction of inclination and inclination angle of the plural conductive wires (conductive paths) of the anisotropic conductive connector to be produced become more uniform. By the above-mentioned leaving “some clearance” is meant a clearance of about 0.5-20 mm between the lateral surface of the laminate and the inside surface of the box. The “heat resistance” of the heat resistant box means absence of deformation or softening (melting) during the above-mentioned heat treatment, and examples of the above-mentioned heat resistant box include a metal box made of aluminum (hereinafter also to be simply referred to as “alumi”, steel, stainless steel and the like and a ceramic box.

Step 3 (Step for Cutting Block)

[0066] In this Step 3, the block prepared in the aforementioned Step 2 is cut along the plane forming an angle with conductive wire in a predetermined film thickness to give an anisotropic conductive connector. FIG. 8 shows an embodiment in which block 30 (FIG. 7) obtained by accumulating films with conductive wires 10A (FIG. 3(a), FIG. 4) wherein (the center line L1 of) the aforementioned conductive wire 2 is inclined at an angle (&agr;1) with the linear side L2 of the principal plane 1a of the insulating film 1.

[0067] In FIG. 8, the cutting tool 3 is a cutter. However, as long as a film can be cut out from a block in this step, it is not limited to a cutter, but various cutting tools (wire saw, slicer, plane, laser etc.) can be used.

[0068] In the embodiment shown in FIG. 8, block 30 is cut along the plane 30b as the cutting plane, which plane 30b is perpendicular to the predetermined linear edge side L2′ derived from the predetermined linear side L2 (see FIG. 4-FIG. 6) of the principal plane 1a of the insulating film 1 in the film with conductive wires in the block 30. That is, as the film with conductive wires, a film with conductive wires 10A (FIG. 3(a), FIG. 4) wherein (the center line L1 of) the conductive wire 2 is inclined at an angle (&agr;1) to the predetermined linear side L2 of the principal plane 1a of the insulating film 1, is used, and the block 30 is cut along the plane 30b as a cutting plane, which plane 30b is perpendicular to the linear edge side L2′ of the block 30 as the standard, which is derived from the predetermined linear side L2 of the principal plane 1a of the insulating film 1. As a result, the inclination angle (inclination angle (&agr;1) of the center line L1 of the conductive wire 2 relative to the predetermined linear side L2 of the principal plane 1a of the insulating film 1) of the conductive wire 2 set for a film with conductive wires 10A directly becomes an angle (&agr;) formed by (the center line L10 of) the conductive path 51 with the line L20 perpendicular to the principal plane 50a of the film substrate 50 in the anisotropic conductive connector 60 (FIG. 11) to be produced. Accordingly, determination of the cutting plane in the cutting step is easy, and an anisotropic conductive connector, wherein plural conductive paths are inclined at the objective inclination angle and the directions of inclination between plural conductive paths have high uniformity (plural conductive paths are inclined at a constant direction), can be certainly produced. In addition, because the size of the film (product size) obtained by cutting is unified, obliterating the problem of drastic fall in the yield.

[0069] In contrast, when an anisotropic conductive connector is cut out as a film with conductive wires from a block prepared using a film wherein (the center line of) the conductive wire is not inclined relative to the linear side of the principal plane of the insulating film, such as a film with conductive wires 10B (FIG. 3(b)), the cutting plane is determined such that the angle formed by (the center line of) the conductive wire with the line perpendicular to the cutting plane equals the angle (&agr;) formed by (the center line L10) of the conductive path 51 with the line L20 perpendicular to the principal plane 50a of the film substrate 50 in the anisotropic conductive connector 60 (FIG. 11).

[0070] According to the production method of the present invention, an anisotropic conductive connector is cut out from a block accumulating plural films with conductive wires (each being substantially the same films cut out from a large-sized film with conductive wires) comprising (rows of) plural conductive wires arranged in parallel at the same pitch as mentioned above. As a result, a problem of non-uniform direction of inclination of conductive paths in an anisotropic conductive connector due to the non-uniform winding direction of insulated conductive wires (metal wires) in a conventional winding block obtained by winding insulated conductive wires in multiplicity can be prevented, and plural conductive paths inclined at a predetermined inclination angle, and an anisotropic conductive connector having only a small dispersion in the directions of inclination between plural conductive paths can be produced easily. In addition, conventionally-needed cutting while adjusting the positions of the block and a cutter in consideration of the direction of (the center line of) wires in a block and post-processing for unifying the film size (product size) of the anisotropic conductive connector cut out after the cutting are not necessary, thereby obliterating complicated production work. Accordingly, an anisotropic conductive connector having high reliability of connection with a target (circuit board, semiconductor element) and in a desired size (film size (product size)) can be produced in a high yield.

[0071] While the foregoing explains the production method of the present invention by reference to a film with conductive wires having a rectangular outer shape of the insulating film (outer shape of principal plane), the outer shape of the insulating film of a film with conductive wires in the present invention may be other than rectangular. As is understood from the above explanation, it is needless to say that the principal plane of the insulating film of a film with conductive wires has a shape ((outer shape) having a linear side, based on which the inclination angle of the conductive wire can be defined, such as rectangular, is preferable.

[0072] Furthermore, since an anisotropic conductive connector having a rectangular whole shape (outer shape of film substrate) is often used in its general applications (connector for mounting, test connector (particularly test connector)), in the present invention, too, the outer shape of the insulating film of a film with conductive wires is preferably made rectangular, so that a rectangular anisotropic conductive connector can be obtained by merely cutting the block.

[0073] In the foregoing descriptions, the production method of the present invention has been explained by referring to the anisotropic conductive connector 60 wherein the conductive paths 51 are arranged to form a square matrix as shown in FIG. 11. When an anisotropic conductive connector wherein the conductive paths are close packed is to be produced, the films are laminated such that respective conductive wires on the film with conductive wires for odd-numbered accumulation fit into the gaps between conductive wires on a film with conductive wires for even-numbered accumulation, during production of a laminate comprising a film with conductive wires.

[0074] In the present invention, moreover, when an anisotropic conductive connector of the type where the end of the entire conductive paths or particular part of the conductive paths protrude(s) from or cave(s) into the principal plane of the film substrate, or of the type where only one end or both ends of each conductive path protrude from or cave into the principal plane of the film substrate is to be produced, the following treatments are conducted after the aforementioned Steps 1-3.

[0075] When the end of a conductive path is protruded from the principal plane of the film substrate, a method for selectively removing the periphery of the end of the conductive path of the film substrate to be protruded is exemplified. To be specific, wet etching with organic solvent, dry etching by plasma etching, argon ion laser, KrF excimer laser and the like, and the like are used alone or in combination. The above-mentioned organic solvent is appropriately selected from the materials of the coating layer of the film substrate and insulated conductive wire. For example, dimethylacetamide, dioxane, tetrahydrofuran, methylene chloride and the like can be exemplified.

[0076] It is also possible to make protrusion by plating and deposition by precipitating of metal on the end (edge face) of the conductive path from which to protrude. When a metal is precipitated, the metal may be the same or different from the metal constituting the aforementioned conductive path. Preferable examples thereof include an Ni/Au layer by electroless plating. By forming an Ni/Au layer by electroless plating, the contact resistance with the terminal of the target (electronic component, circuit board etc.) can be advantageously suppressed to a low level.

[0077] As a method for forming a recess in the conductive path from the surface of the film substrate, a method for selectively removing only the conductive path exposing from the surface of the film substrate is employed, which is specifically chemical etching with acid or alkaline.

[0078] The amount of protrusion (height from the principal plane of the film substrate to the tip surface of the conductive path) of the conductive path is generally selected from the range of 5-60 &mgr;m.

[0079] The anisotropic conductive connector produced by the method of the present invention is particularly preferable as a test connector, and for this use, the modulus of elasticity of the connector as a whole is preferably 5-100 MPa at 0-50° C., particularly preferably 5-70 MPa. The modulus of elasticity of the connector as a whole is measured using a dynamic viscoelasticity measure apparatus (DMS210, Seiko Instruments Inc.). The measurement conditions are an extension mode relative to one direction from among the directions that the surface of the film substrate of the anisotropic conductive connector expands at a constant frequency (10 Hz) at a temperature raise rate of 5° C./min and the measurement at −30° C.-250° C. The thickness of the sample to be input for measurement is thickness (symbol T in FIG. 11) of the film substrate in the anisotropic conductive connector 60 (FIG. 11).

[0080] The factors determining the modulus of elasticity of the connector as a whole of the anisotropic conductive connector 60 (FIG. 11) are material, width (diameter), sectional shape, inclination angle and pitch of the conductive path 51, as well as material and thickness of the film substrate and the like. According to the production method of the anisotropic conductive connector of the present invention, therefore, these values are controlled and the modulus of elasticity of the connector as a whole of the obtained anisotropic conductive connector for the above-mentioned measurement at −30° C. to 250° C. is preferably set for 5-70 MPa at 0-50° C.

EXAMPLES

[0081] The present invention is explained in detail by referring to Example and Comparative Example.

Example 1

[0082] An aluminum cylindrical core having a diameter of 320 mm and a length of 270 mm is set on a horizontal type regular winding machine (HPW-02, Nittoku Engineering Co., Ltd.), on which a 50 &mgr;m-thick fluorocarbon resin film as a slip film and one layer consisting of a 100 &mgr;m-thick thermoplastic polyurethane elastomer having a hardness of 75 degrees (Esmer URS, Nihon Matai Co., Ltd., softening temperature 60° C.) thereon are wound, and a heat-resistant polyurethane coated wire (copper wire (diameter 25 &mgr;m) coated with heat resistant polyurethane in 2 &mgr;m thickness) having a diameter of 29 &mgr;m was wound 250 mm at a winding intervals (pitch) of 100 &mgr;m. As a slip film, a 50 &mgr;m-thick fluorocarbon resin film was wound to cover the wound wire, and on the outside thereof, a 1 mm thick aluminum plate was set as a support plate along the cylindrical shape of the core.

[0083] A bag permitting formation of a vacuum space was prepared from a 80 &mgr;m-thick heat resistant nylon film (1000 mm×1530 mm, WL 8400-003-60-1000-SHT9, Airtec Co., Ltd., softening temperature: 220° C.) and a seal tape GS213 (Airtec Co., Ltd.), and the above-mentioned wound product consisting of a core, a film and a wire and a support plate in integration was placed in this bag. The film space was hermetically sealed and sucked with a vacuum hose (connected to a vacuum pump) to vacuumize the film space. While maintaining the vacuum, the bag containing the wound product and the support plate was placed in a heat press treatable autoclave (Ashida Co., Ltd.). After setting, the inside of the tube was heated to make the temperature of the core 155° C. (temperature inside the tube: 200° C.), along with which the tube was pressed with a nitrogen gas to make the pressure inside the tube 10 kgf/cm2. After the core temperature and the pressure in the tube reached the objective levels, they were maintained for about 30 min and cooled. When the temperature reached 70° C., the pressure was released.

[0084] Thereafter, the bag containing the wound product consisting of a core, a film and a wire was taken out from the autoclave, the wound product was taken out from the bag to remove the core, whereby a roll-like block integrating the thermoplastic urethane elastomer film and a heat-resistant urethane coated wire was obtained.

[0085] Then one side of the aforementioned roll-like block was cut to give a plane-like product, from which 22 films with wires were cut out using a Thomson cutter, wherein plural heat resistant urethane coated wires were arranged in parallel to each other at a pitch of 100 &mgr;m on a principal plane of a rectangular thermoplastic urethane elastomer film (120 mm×62 mm) in the state shown in FIG. 4(c), namely, the plural heat resistant urethane coated wires were arranged and adhered at an inclination angle (&agr;1) of 15 degrees relative to the linear side L2 of the thermoplastic urethane elastomer film. Then the 22 films with wires were accumulated in the vertical direction, as shown in FIG. 5, and this laminate was placed in an aluminum box, as shown in FIGS. 9 and 10.

[0086] As the above-mentioned aluminum box, a cuboid box as a whole having an opening on the upper surface, permitting entry of the laminate as it is thereinto, a depth completely accommodating the laminate and having a size leaving some clearance of 1.5 mm between the inside surface thereof and the lateral surface of the laminate (side surface of a thermoplastic urethane elastomer film).

[0087] A 10 mm-thick aluminum plate (120×62 mm) was placed into the above-mentioned aluminum box from an opening on the upper surface of the box and on the uppermost surface of the aforementioned laminate. In this state, the aluminum box containing the laminate was placed in the bag made of a nylon film, which permits formation of a vacuum space and was used in the above, and the film space was vacuumized. While maintaining the vacuum, the bag was placed in a heat press treatable autoclave (Ashida Co., Ltd.). The aluminum box was heated to a temperature of 175° C. (temperature inside the tube: 200° C.), along with which the tube was pressed with a nitrogen gas, such that the pressure inside thereof became 15 kgf/cm2. After the temperature and the pressure in the tube reached the objective levels, the inside of the tube was cooled, whereby a block integrating the laminate was formed.

[0088] The block prepared in the above was cut in a predetermined film thickness with a wire saw (F-600, Yasunaga Corporation), such that the cutting plane relative to a predetermined linear edge side (linear edge side derived from the linear side L2 of thermoplastic urethane elastomer film) of the block becomes the perpendicular direction to give 200 sheets (120 mm×60 mm) of anisotropic conductive connectors having a thickness of the film substrate of 100 &mgr;m.

[0089] From the 200 anisotropic conductive connectors obtained above were arbitrarily sampled 5 connectors, each of which was examined for dispersion in the direction of inclination and the inclination angle of conductive paths, from the two sectional directions of the anisotropic conductive connector with a microscope (OLYMPUS OPTICAL CO., LTD.). That is, a first section in the direction perpendicular to the principal plane of the film substrate and a second sectioncut in parallel with the principal plane of the film substrate were observed with a microscope. As a result, the dispersion in the direction of inclination (dispersion in angle in the direction of inclination) of all conductive paths present in the section was found to be 0.15 degree, from the observation of the second section and the dispersion in inclination angle was found to be 0.22 degree, from the observation of the first section.

Comparative Example 1

[0090] An insulated conductive wire, wherein a copper wire having a diameter of 25 &mgr;m is coated with the thermoplastic polyurethane elastomer (2 &mgr;m thick) used in the above-mentioned Example, was regularly wound around a square columnar plastic core (entire length (winding width) 640 mm, sectional shape 160 mm×160 mm square) with a winding machine to make a closely packed winding to give a winding having an average winding number of 3500 turns per one layer, and a number of layers wound of 150 layers (thickness of layer about 12 mm). The obtained roll-like winding was pressed at 10 kgf/cm2 while heating to about 150° C. to weld a thermoplastic polyurethane elastomer, then cooled to room temperature to give a winding block integrating the wound wires. This winding block was cut in a block with a band saw along a plane forming an inclination angle of 15 degrees with the wound wire. As a result, a 120 mm×180 mm, 10 mm-thick block prior to an anisotropic conductive film was obtained. The obtained block was cut with a wire saw, the outer diameter size was finalized to give 2800 anisotropic conductive connectors having a size of 10 mm×120 mm and a thickness of 100 &mgr;m.

[0091] From the 2800 anisotropic conductive connectors obtained above were arbitrarily sampled 5 connectors, each of which was examined for dispersion in the direction of inclination and the inclination angle of conductive paths, from the two sectional directions of the anisotropic conductive connector with a microscope. As a result, the dispersion in the direction of inclination (dispersion in angle in the direction of inclination) was found to be 0.45 degree and the dispersion in inclination angle was found to be 0.35 degree.

[0092] Using the anisotropic conductive connectors prepared in the above-mentioned Example 1 and Comparative Example 1, a connection test (continuity test) between electronic component described in the following and a circuit board was performed.

Specification of Electronic Component for Evaluation

[0093] size of parts: 9.6 mm×7.0 mm×1.65 mm (thickness)

[0094] size of electrode: 1.0 mm×0.8 mm

[0095] number of electrodes: 12

[0096] center pitch at the position of electrode: 1.8 mm

Specification of Circuit Board for Evaluation

[0097] substrate: glass epoxy substrate (FR-4)

[0098] entire thickness including circuit pattern: 1 mm

[0099] ratio of circuit width and interval width of circuit pattern: (1.0 mm: 0.8 mm)

Evaluation Method

[0100] An anisotropic conductive connector was disposed between the above-mentioned electronic component for evaluation and the circuit board for evaluation, a contact load 25N was applied from the electronic component side to see if all the terminals (electrodes) of the electronic component are continued with the circuit board (namely, if all the contact points continue). This test is repeated 10 times.

Results

[0101] When the anisotropic conductive connector of Comparative Example 1 was used, all contact points were continued in 8 times out of 10 times of the test. In contrast, when the anisotropic conductive connector of Example 1 was used, all contact points were continued in 10 times out of 10 times of the test.

[0102] From this result, it is clear that the anisotropic conductive connector obtained by the production method of the present invention shows smaller dispersion in the direction of inclination (bending direction of conductive path) between plural conductive paths, shows fine contactability with the target, and is highly reliable in connection.

[0103] As is clear from the above explanation, the present invention can efficiently produce an anisotropic conductive connector showing smaller dispersion in the direction of inclination (bending direction of conductive path) between plural conductive paths, fine contactability with the target, and high connection reliability. In addition, an anisotropic conductive connector capable of affording high connection reliability with the target can be produced in a desired film size and in a high yield.

Claims

1. A method of producing an anisotropic conductive connector having a structure wherein the center line of plural conductive paths penetrating in the thickness direction of a film substrate forms an angle with a line perpendicular to the principal plane of the film substrate, which comprises the steps of

winding an insulating film around the circumference of a core,

then helically winding a conductive wire around the circumference of the insulating film at a predetermined pitch, or helically winding a conductive wire around the circumference of the core,

then winding the insulating film to cover the conductive wire,

heating and pressurizing to integrate the insulating film and the conductive wire on the core to give a roll-like product,

removing said roll-like product from the core,

incising the product to give a plane-like product,

cutting out plural films with conductive wires from the plane-like product,

then laminating the plural films with conductive wires such that the conductive wires on the adjacent films are parallel to each other to give a laminate,

heating and pressurizing the laminate to form a block integrating the plural films with conductive wires, and

then cutting the block in a predetermined film thickness along the plane forming an angle with the conductive wire to give an anisotropic conductive connector.

2. The production method of claim 1, wherein the plural films with conductive wires are cut out in such a manner that the principal plane of the insulating film has a linear side and the center line of the plural conductive wires forms a predetermined inclination angle with the linear side, the plural films with conductive wires are laminated such that the linear sides of the adjacent insulating films are in parallel relation, thereby forming a laminate, and a block obtained from the laminate is cut in a predetermined film thickness along the plane perpendicular to a linear edge side thereof derived from the linear side of the principal plane of the insulating film.

3. The production method of claim 1, wherein the insulating film and the conductive wires wound around the core are set together with the core in a space permitting formation of a decompression or vacuum and, after decompressing or vacuumizing the space, heated and pressurized to integrate the insulating film and the conductive wire on the core.

4. The production method of claim 3, wherein said space permitting formation of a decompression or vacuum is an inner space of a bag made of a flexible film.

5. The production method of claim 3, wherein said pressing is done by introducing a compressed air into said space permitting formation of a decompression or vacuum.

6. The production method of claim 1, wherein the laminate is set in the space permitting formation of a decompression or vacuum, and after decompressing or vacuumizing the space, heated and pressurized.

7. The production method of claim 6, wherein the space permitting formation of a decompression or vacuum is an inner space of a bag made of a flexible film.

8. The production method of claim 6, wherein the laminate is housed in a heat resistant box having a size leaving some clearance between the inside surface of the box and the lateral surface of the laminate upon accommodation of the laminate, set in the space inside the bag made of a flexible film together with the heat resistant box, and after decompressing or vacuumizing the space, heated and pressurized.