Electrical Connectors

Abstract

To provide an electric connector in which conductivity of a conductive part is easily maintained even when the electric connector is repeatedly compressed and of which the durability is improved.SOLUTION: The present invention relates to an electric connector which is disposed between a connection terminal of a first electronic device and a connection terminal of a second electronic device and configured to electrically connect them. The electric connector comprises a substrate sheet (1) and a plurality of conductive parts (5). Formed is a plurality of penetration holes (2) penetrating from a first face (1a) to a second face (1b) of the substrate sheet. The conductive part forms a conducting path for conduction from the first face to the second face along the penetration holes. The conductive part includes conductive particles (P) and conductive fillers (F) which are more elongated than the conductive particles.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to electrical connectors for connecting electronic devices together. [Background technology]

[0002] Conventionally, connectors (hereinafter referred to as electrical connectors) that connect fine electrodes by pressure welding have been used to connect electronic devices. Electrical connectors are sheet-shaped and have multiple conductive parts and insulating parts that insulate them from each other. They are placed between the connection terminals of a first device and the connection terminals of a second device, electrically connecting them. Patent Document 1 discloses the following method for manufacturing such electrical connectors. First, a photosensitive resin composition containing conductive particles is applied to the surface of a substrate, and the coating is pre-baked and a magnetic field is applied to orient the conductive particles in the thickness direction of the coating. Next, photolithography is performed according to the arrangement of the terminals of the electronic devices to be connected, forming the conductive parts of the electrical connector, and then an insulating part made of resin is formed around the conductive parts.

[0003] The method of Patent Document 1 requires expensive equipment for performing photolithography, which increases the manufacturing costs of the electrical connector. As a method that does not require photolithography, the inventors have investigated the following method, which uses a set of molds O to hold multiple magnets J in accordance with the arrangement of the terminals of the electronic device to be connected, as shown in Figure 16. Specifically, they attempted to form a resin composition layer G containing conductive particles P between a set of molds O arranged facing each other, and to arrange the conductive particles P only between the opposing magnets J. However, it was difficult to control the arrangement of all the conductive particles P using magnetic force alone. For this reason, there was a concern that, within the resin composition layer G, some of the conductive particles P constituting the first wiring would come into contact with some of the conductive particles P constituting the adjacent second wiring, causing a short circuit between the first wiring and the second wiring. In the figure, the area circled by a dashed line is an example of a location where a short circuit may occur.

[0004] Therefore, the inventor solved the problem of short-circuiting between through-wires by preparing a base sheet 1, forming holes 2 in advance at the locations where through-wires are desired to be formed, applying a resin material containing conductive particles P to the surface of the base sheet 1, injecting part of the resin material into the holes 2, and orienting the conductive particles P in the holes 2 in the thickness direction by magnetic force, as shown in Figure 13 (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-154550 [Patent Document 2] Japanese Patent Publication No. 2020-27724 Summary of the Invention [Problem to be solved by the invention]

[0006] Although electrical connectors manufactured using the method disclosed in Patent Document 2 prevent short circuits between through-wires, repeated compression in the thickness direction of the electrical connector during use can cause cracks to form in the through-wires, resulting in a loss of electrical continuity (Figure 5).

[0007] The present invention provides an electrical connector that is more likely to maintain the conductivity of its conductive parts even when the electrical connector is repeatedly compressed, and that has improved durability. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that durability against the repeated compression described above can be improved by incorporating conductive filler F, which is thinner and has a higher aspect ratio than the conductive particles P, in addition to the conductive particles P that constitute the through wiring, as shown in Figure 6, etc., and have completed the present invention. The present invention has the following aspects.

[0009] [1] An electrical connector disposed between a connection terminal of a first electronic device and a connection terminal of a second electronic device for electrically connecting them, the electrical connector comprising a base sheet and a plurality of conductive portions, wherein a plurality of through holes are formed penetrating from a first surface to a second surface of the base sheet, the conductive portions form conductive paths that run along the through holes from the first surface to the second surface, and the conductive portions include an elastomer, conductive particles, and conductive fillers that are thinner and longer than the conductive particles. [2] The electrical connector according to [1], wherein the center lines of the plurality of through holes are inclined with respect to the first surface and the second surface. [3] The electrical connector according to [1] or [2], wherein the content of the conductive particles is 50 to 94 mass% relative to the total mass of the elastomer, the conductive particles, and the conductive filler. [4] The electrical connector according to [3], wherein the content of the conductive filler is 0.01 to 5 mass % relative to the total mass of the elastomer, the conductive particles, and the conductive filler. [5] The electrical connector according to any one of [1] to [4], wherein the ratio (L1 / R1) of the length L1 (unit: μm) in the longitudinal direction of each conductive filler to the thickness R1 (unit: μm) of each conductive filler represented by a line segment that bisects the length L1 and intersects with it at right angles is calculated for 10 randomly selected conductive fillers included in one conductive part arbitrarily selected from the plurality of conductive parts, and the average value X of the obtained 10 ratios is 10 to 100. [6] The electrical connector described in [5], wherein for the through hole having one arbitrarily selected conductive portion inside, the ratio (R2 / Y) of the thickness R2 (unit: μm) of the through hole represented by a line segment that intersects perpendicularly while bisecting the length L2 along the center line of the through hole to the average value Y of the lengths L1 (unit: μm) of the 10 conductive fillers is 5 to 500. [7] The electrical connector according to [5] or [6], wherein the conductive particles have an average particle size of 0.01 μm to 10 μm. [8] An electrical connector according to any one of [1] to [7], wherein a first end of the conductive portion protrudes from the first surface, or a second end of the conductive portion protrudes from the second surface. [9] An electrical connector according to any one of [1] to [7], wherein a first end of the conductive portion on the first surface side is provided with another conductor protruding from the first surface, or a second end of the conductive portion on the second surface side is provided with another conductor protruding from the second surface.

[10] The electrical connector according to any one of [1] to [9], wherein the base sheet is made of silicone rubber.

[11] The electrical connector according to any one of [1] to

[10] , wherein the elastomer is silicone rubber.

[12] The electrical connector according to any one of [1] to

[11] , wherein the conductive particles are made of silver.

[13] The electrical connector according to any one of [1] to

[12] , wherein the conductive filler is a carbon nanotube, a carbon nanofiber, a metal nanowire, or a metal-plated body. [Effects of the Invention]

[0010] The electrical connector of the present invention has improved durability against repeated compression. The mechanism behind this is thought to be that even if cracks occur where the contact between conductive particles in the conductive portion is broken, the elongated conductive filler fills bridge the broken area, maintaining conductivity. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a plan view of an electrical connector 10 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line A-A in FIG. [Figure 3A] FIG. 2 is a cross-sectional view of an electrical connector 20 according to another embodiment of the present invention. [Figure 3B] 10 is a cross-sectional view showing a state when a first surface 1a of the electrical connector 20 is pressed. FIG. [Figure 4] 2 is an enlarged cross-sectional view of the electrical connector 10 in the thickness direction. FIG. [Figure 5] FIG. 10 is a cross-sectional view showing how a crack C occurs after repeated compression in a conductive part 5 that forms a through-wiring of an electrical connector of a comparative example. [Figure 6] FIG. 10 is a cross-sectional view showing how the conductive portion 5 forming the through wiring of the electrical connector of the embodiment maintains electrical continuity even after repeated compression due to the inclusion of conductive filler F. [Figure 7] A cross-sectional view showing how the conductive part 5 that forms the through wiring of another embodiment of an electrical connector maintains conductivity even after repeated compression due to the inclusion of conductive filler F. [Figure 8] 1 is a plan view showing an example of manufacturing the electrical connector 10. FIG. [Figure 9] FIG. 9 is a cross-sectional view taken along line BB in FIG. 8. [Figure 10] 1A to 1C are cross-sectional views showing an example of manufacturing the electrical connector 10. [Figure 11] 1 is a plan view of a base sheet 1 produced in the manufacturing process of an electrical connector 10. FIG. [Figure 12] 1 is a plan view showing an example of manufacturing the electrical connector 10. FIG. [Figure 13] FIG. 13 is a cross-sectional view taken along line CC in FIG. [Figure 14] 1 is a plan view showing an example of manufacturing the electrical connector 10. FIG. [Figure 15] FIG. 15 is a cross-sectional view taken along line DD in FIG. [Figure 16] FIG. 1 is a cross-sectional view showing an attempt to place conductive particles P dispersed in a resin composition G between opposing magnets J. DETAILED DESCRIPTION OF THE INVENTION

[0012] Electrical Connectors The electrical connector of a first aspect of the present invention is an electrical connector disposed between a connection terminal of a first electronic device and a connection terminal of a second electronic device for electrically connecting them, and includes a base sheet and a plurality of conductive portions. A plurality of through holes are formed through the base sheet from a first surface to a second surface, and the conductive portions form conductive paths that run along the through holes from the first surface to the second surface. The conductive portions include an elastomer, conductive particles, and conductive fillers that are thinner and longer than the conductive particles.

[0013] 1 and 2, an electrical connector 10 according to a first embodiment of the present invention includes a base sheet 1. The base sheet 1 has a first surface 1a and an opposing second surface 1b, and has a plurality of through holes 2 penetrating from the first surface 1a to the second surface 1b. The electrical connector 10 comprises a plurality of conductive portions 5 and insulating portions 6, forming an island-sea structure in which the conductive portions 5 are island portions and the insulating portions 6 are sea portions. Each conductive portion 5 forms a through-wiring that penetrates from the first surface 1a to the second surface 1b. A first end of each conductive portion 5 forms a protruding portion 8 that protrudes from the first surface 1a, and its second end is exposed on the second surface. Each conductive portion 5 is independent from the other, and mutual insulation is maintained by the insulating portions 6.

[0014] The electrical connector 10 is in the form of a rectangular sheet, with its short side direction being the X direction, its long side direction being the Y direction, and the direction perpendicular to the first surface 1a (ie, the thickness direction of the sheet) being the Z direction. The shape of the electrical connector 10 in plan view is not limited to a rectangle, but may be a circle, an ellipse, a polygon, or any other shape. The length x width size of the electrical connector 10 is not particularly limited, and can be, for example, 1 mm x 1 mm to 10 cm x 10 cm. The thickness of the electrical connector 10 can be, for example, 50 μm or more and 500 μm or less. The shape, size, thickness, etc. of the electrical connector 10 are appropriately set according to the shapes and terminal arrangements of the electronic devices to be connected to the first surface 1a and the second surface 1b, respectively.

[0015] <Conductive part 5> The conductive portions 5 of the electrical connector 10 are arranged at a constant pitch along the X and Y directions. The conductive portions 5 are preferably columnar in shape. Examples of the cross-sectional shape of the conductive portion 5 cut in the XY plane include a circle, an ellipse, a rectangle, and other polygons. The shape in plan view of the protrusions 8 protruding toward the first surface 1a of the conductive portion 5 may be the same as or different from the cross-sectional shape.

[0016] The central axis of the columnar conductive portion 5 may be perpendicular to the first surface 1a and the second surface 1b (Figure 2) or inclined (Figure 3), but is preferably inclined from the viewpoint of further increasing durability against repeated compression. 2, when the conductive portion 5 is perpendicular, compression due to a force applied perpendicularly to the conductive portion 5 occurs only in the conductive portion 5. Therefore, the conductive portion 5 must be distorted by the amount of compression. On the other hand, as shown in Figure 3, if the inclination θ° relative to the first surface 1a is, for example, 60°, the sheet thickness is 100 μm, the diameter of the conductive portions is 20 μm, and the pitch of the conductive portions is 40 μm, the deflection margin when the end faces of the conductive portions are pressed is 60 μm for the conductive portions and 40 μm for the insulating portions. In this case, when the base sheet 1 is compressed in the thickness direction, most of the compression amount is absorbed by the deflection margin of the insulating portions, so the impact of compression on the conductive portions is less than when the base sheet is perpendicular. As a result, the inclined orientation provides greater durability against repeated compression.

[0017] See Figure 4. The size S1 of the end portion exposed on the second surface of each conductive portion 5 is the diameter of the smallest circle including the end portion. From the viewpoint of reducing the resistance of the conductive portion 5 and accommodating the narrow pitch of terminals in the connected electronic device, the diameter is, for example, preferably 1 µm to 100 µm, more preferably 3 µm to 50 µm, and even more preferably 5 µm to 25 µm. The size S1 of the end portion of each conductive portion 5 may be the same or different from each other. The diameter can be measured by a known microstructure observation means such as a measuring microscope.

[0018] The aspect ratio of the columnar conductive portion 5, expressed as (size S1: length H in the axial direction excluding height h of the protrusion 8), is preferably 1:5 to 1:30, and more preferably 1:8.5 to 1:25.5. When the thickness is equal to or greater than the lower limit of the above range, the pitch between adjacent conductive parts 5 can be narrowed. When it is equal to or less than the upper limit of the above range, the resistance value of the conductive part 5 can be reduced. The size S1 and axial length H of each conductive portion 5 can be measured using a known microstructure observation means such as a measuring microscope.

[0019] The pitch between adjacent ends of the conductive portions 5 exposed on the second surface 1b is the center-to-center distance between the smallest circles that include each end. This pitch is set arbitrarily depending on the arrangement of the terminals of the electronic device to be connected. The arrangement of the conductive portions 5 corresponds to the arrangement of the holes 2, which can be formed at any position during the manufacture of the electrical connector 10.

[0020] The conductive portions 5 on the second surface 1b of the electrical connector 10 are arranged in a two-dimensional array of X columns and Y rows. The arrangement of the conductive portions 5 is not limited to this example, and any arrangement pattern can be adopted. In the X columns and Y rows, for example, X and Y can each independently be any integer between 10 and 1000. The arrangement pattern is preferably a two-dimensional array.

[0021] <Protrusion 8> The shape in plan view of each of the protrusions 8 constituting the first end of each conductive portion 5 is not particularly limited, and any shape can be used. Examples include a square, a circle, an ellipse, and other polygons. The shapes in plan view of each of the protrusions 8 may be the same or different from one another. The size S2 in a plan view of each protrusion 8 is not particularly limited and can be set appropriately to match the shape of the electrodes of the electronic device to be connected. Here, size S2 is the diameter of the smallest circle that includes the shape of the protrusion 8 in a plan view. From the viewpoint of reducing the resistance of the protrusion 8 and accommodating the narrow pitch of the terminals of the electronic device to be connected, the diameter is preferably 1 μm to 100 μm, more preferably 3 μm to 50 μm, and even more preferably 5 μm to 25 μm. The diameter can be measured by a known microstructure observation means such as a measuring microscope. From the viewpoint of further improving connectivity to electronic devices, it is preferable that the size S2 of the protrusion 8 in a plan view is larger than the size (cross section) of the conductive portion 5 at the base of the protrusion 8 (the portion flush with the first surface 1a).

[0022] The height h of the protrusions 8 is not particularly limited and may be, for example, 1 μm to 50 μm. The height h of each protrusion 8 may be the same as or different from one another. The height h of the protrusions 8 is determined from an image of a cross section of the electrical connector 10 taken by a known method in the thickness direction, as shown in Figure 4. The height h of the protrusions 8 is preferably an average value calculated by, for example, obtaining the heights of 5 or more, preferably 10 or more, protrusions 8 randomly selected from an image of a cross section showing 10 or more, preferably 30 or more, protrusions 8 through image processing.

[0023] In the electrical connector 10 shown in Figures 1 to 4, all first ends of the conductive portions 5 form protrusions 8, but only arbitrarily selected first ends may form protrusions 8, and the other first ends may simply be exposed flush with the first surface 1a, like the second ends. Although not shown, an arbitrarily selected part or all of the second end portion of each conductive portion 5 on the second surface 1b side may form a protrusion. Furthermore, in the example shown, protrusion 8 in electrical connector 10 constitutes the first end of conductive portion 5 and is made of the same material (composition) as conductive portion 5, but protrusions made of a different material may be provided at the first end and / or second end of conductive portion 5. For example, a conductive layer formed by binding carbon particles or metal particles with a resin material or a metal film layer formed by plating or the like may be provided in contact with the first end and / or second end of conductive portion 5 that is exposed flush with second surface 1b of base sheet 1.

[0024] <Insulation part 6> The insulating portion 6 of the electrical connector 10 is the sea portion of the sea-island structure, and is an insulating portion. The length of the insulating portion 6 in the Z direction is the same as the thickness of the base sheet 1, and is preferably 25 μm or more and 750 μm or less, and more preferably 50 μm or more and 500 μm or less. If the length is equal to or greater than the lower limit, the mechanical strength of the electrical connector 10 is increased. If the length is equal to or less than the upper limit, the flexibility of the electrical connector 10 is increased, allowing it to be easily mounted inside electronic devices that require thinness.

[0025] The insulating portion 6 preferably contains an elastomer. The content of the elastomer relative to the total mass of the insulating portion 6 is preferably 60 to 100 mass %, more preferably 75 to 100 mass %, and even more preferably 90 to 100 mass %. When the content is 70% by mass or more, the compressibility and flexibility of the electrical connector 10 are sufficiently increased, and the end (for example, the second end) of the conductive portion 5 other than the protruding portion is improved in connectivity to the electronic device.

[0026] It is preferable that the type of elastomer forming the conductive portion 5 and the type of elastomer forming the insulating portion 6 are the same in order to improve adhesion between them, and it is more preferable that they are silicone rubber in order to improve heat resistance and compression durability.

[0027] [Conductive particles and conductive fillers] Each conductive portion 5 contains conductive particles and a conductive filler. The shape of the conductive particles can be approximated to a sphere, spheroid, or plate. On the other hand, the shape of the conductive filler is clearly more elongated than the conductive particles and can be described as rod-like, fibrous, or wire-like. The aspect ratio (length / thickness) of the length to the thickness of a cross section perpendicular to the longitudinal direction of the conductive filler is at least 3 times the aspect ratio (major axis / minor axis) of the conductive particle, preferably 5 times or more, more preferably 10 times or more, and even more preferably 50 times or more. There is no particular upper limit to this ratio, and a rough guideline is, for example, 100 times or less.

[0028] For 10 randomly selected conductive fillers contained in one conductive portion 5 arbitrarily selected from the plurality of conductive portions 5, the ratio (L1 / R1) of the longitudinal length L1 (unit: μm) of each conductive filler to the thickness R1 (unit: μm) of each conductive filler, represented by a line segment that bisects the length L1 and intersects with it at right angles, is determined, and the average value X of the obtained 10 ratios is preferably 5 to 100, more preferably 10 to 100, and even more preferably 50 to 100. Within the above range, durability against compression when contained together with conductive particles is further improved, and bending or breakage of the conductive filler can be reduced. The length L1 and thickness R1 of the conductive filler can be determined by measurement using a known magnification observation means such as a magnifying microscope or an electron microscope.

[0029] For a through hole 2 having a conductive portion 5 therein containing the ten conductive fillers whose length L1 has been measured, the ratio (R2 / Y) of the thickness R2 (unit: μm) of the through hole 2, which is represented by a line segment intersecting at right angles while bisecting the length L2 along the center line (axis) of the through hole 2, to the average value Y of the lengths L1 (unit: μm) of the ten conductive fillers, is preferably 5 to 500, more preferably 15 to 250, and even more preferably 30 to 150. When the amount is equal to or greater than the lower limit of the above range, the length direction of the conductive filler and the length direction of the center line of the through hole 2 tend to be aligned, and when contained together with the conductive particles, the durability against compression is further improved. When the thickness is equal to or less than the upper limit of the above range, it is possible to reduce bending or breakage of the conductive filler when the conductive portion 5 is compressed. In addition, the conductive filler can easily enter the through holes 2 during the production of the electrical connector 10, facilitating production. The length L2 and width R2 of the through-hole 2 are determined by measuring a cross section of the electrical connector 10 in the thickness direction using a known magnification observation means such as a magnifying microscope or an electron microscope.

[0030] The material of the conductive particles may be, for example, composite conductive particles containing a ferromagnetic material, or a conductive material other than the ferromagnetic material. The ferromagnetic material is preferably one that exhibits ferromagnetism at 10 to 40° C., and more preferably one or more selected from iron, cobalt, nickel, and gadolinium. Examples of the conductive material other than the ferromagnetic material include copper, zinc, chromium, platinum, gold, silver, aluminum, palladium, and carbon materials. Examples of the carbon materials include carbon black, ketjen black, carbon nanotubes, fullerene, graphene, and graphite.

[0031] The surfaces of the conductive particles may be treated with a coupling agent such as a silane coupling agent or a titanium coupling agent, as long as the conductivity of the surfaces of the conductive particles is not lost.

[0032] The conductive particles contained in the conductive portion 5 may be of one type or two or more types.

[0033] The content of the conductive particles relative to the total mass of the elastomer, conductive particles, and conductive filler contained in the conductive part 5 is preferably 50 to 94 mass%, and more preferably 70 to 90 mass%. Within this range, good conductivity of the conductive part 5 is obtained, and when contained together with the conductive particles, durability against the compression is further improved.

[0034] The average particle size of the conductive particles is, for example, 10 nm to 10 μm, and preferably 50 nm to 5 μm. Within this range, conductive particles can easily form conductive paths in the through-holes, making it easier to obtain conductive parts 5 with high conductivity (low resistance). The average particle diameter of the conductive particles is calculated by randomly selecting 100 conductive particles contained in the conductive part 5, measuring their major axis (diameter if spherical) by microscopic observation, and averaging the measured values ​​of the 100 particles.

[0035] When the diameter of the smallest circle containing the cross section of the conductive portion 5 cut at any point in a direction perpendicular to the thickness direction of the base sheet 1 is defined as the thickness of the conductive portion 5, the ratio of the thickness of the conductive portion 5 to the average particle size of the conductive particles (thickness / average particle size) is, for example, preferably 3 to 1000, more preferably 5 to 500, and even more preferably 10 to 200. Within these preferred ranges, it is easy to orient the conductive particles by magnetic force, and a conductive portion 5 with high conductivity is likely to be obtained.

[0036] Examples of the conductive filler material include the same materials as those for the conductive particles described above, and among these, carbon nanotubes, carbon nanofibers, metal nanowires, and metal-plated bodies (conductors having a metal-plated surface layer) are preferred.

[0037] The conductive portion 5 may contain one type of conductive filler or two or more types of conductive fillers.

[0038] The content of the conductive filler relative to the total mass of the elastomer, conductive particles, and conductive filler contained in the conductive part 5 is preferably 0.01 to 5 mass %, more preferably 0.05 to 1 mass %. Within the above range, good conduction of the conductive part 5 is obtained, and when it is contained together with the conductive particles, durability against the compression is further improved.

[0039] <Mechanism of action> As shown in Figure 5, in a conductive portion 5 containing only conductive particles P, when the base sheet 1 is repeatedly compressed in the thickness direction, there is a problem that cracks C occur, which break the contact between the conductive particles P. On the other hand, the electrical connector of the present invention contains conductive filler F in addition to conductive particles P, as shown in Figure 6. Therefore, even if cracks occur as described above, the conductive filler F is present to bridge the cracks, so conduction is not interrupted. As a result, durability against repeated compression is improved. This mechanism also works in the case where the through holes 2 are inclined with respect to the thickness direction of the base sheet 1 (with respect to the first surface 1a or second surface 1b of the base sheet 1), as shown in Figure 7.

[0040] <Manufacturing method for electrical connectors> The electrical connector according to the present invention can be manufactured by, for example, the manufacturing method disclosed in Patent Document 2. For example, the manufacturing method includes the following steps (A1) and (B). Step (A1) is a step of introducing a first resin material containing a resin or a resin precursor into a mold having a plurality of convex portions formed therein, and hardening the first resin material to produce a substrate sheet having through or non-through hole portions on a first surface thereof corresponding to each of the convex portions of the mold. Step (B) is a step of applying a resin material containing conductive particles, a conductive filler, and a resin or a resin precursor to the first surface of the base sheet, injecting a portion of the resin material into each of the holes while leaving the remainder of the resin material on the first surface, and hardening the resin material injected into the holes and the resin material left on the first surface to form a conductive portion in each of the holes and to form a conductive layer on the first surface that is continuous with each of the conductive portions, and further removing a portion of the conductive layer by etching to form a plurality of second conductive portions that are independently partitioned from one another. An example of an embodiment will be described below with reference to the drawings.

[0041] <Mold K> The following describes an example of how to fabricate the electrical connector 10 shown in Figures 1 and 2. First, a molding die K shown in Figures 8 and 9 is prepared. A recess N and a plurality of cylindrical protrusions M arranged within the recess N are formed on the surface of the molding die K. The shape of the recess N roughly corresponds to the outer shape of the electrical connector 10. In the illustrated example, the recess N, which is a flat rectangular parallelepiped space that opens upward, is formed on the surface inside the forming mold K. The recess N is a space that forms the insulating portion 6 of the electrical connector 10, and it is possible to form an electrical connector 10 having a base sheet 1 that reflects the shape of the recess N. The cross-sectional shape and arrangement of each of the protrusions M correspond to the cross-sectional shape and arrangement of each of the conductive parts 5, which are the through-wirings that the electrical connector 10 has. The height of each protrusion M may be the same as or different from the depth of the recess N. In other words, the position of the tip of the protrusion M may be flush with the surface Ka of the forming mold K, or may be lower than the surface Ka (i.e., inside the recess N), or may be higher than the surface Ka (i.e., outside and above the recess N). In the illustrated example, the height position of each protrusion M is flush with the surface Ka of the forming mold K.

[0042] <Process A1> As shown in Figures 8 and 9, a liquid first resin material L1 containing a resin or a resin precursor is applied to the surface of a molding die K having recesses N and protrusions M. The first resin material L1 is an insulating material that forms the insulating portion 6. By applying the first resin material L1, it is introduced into the recesses N. At this time, excess first resin material L1 that does not fit into the recesses N overflows onto the surface Ka of the molding die K. To promote the introduction of the first resin material L1 into the recesses N, vacuum treatment, pressurized degassing, pushing with a squeegee, etc. may be performed.

[0043] 10, the first resin material L1 filled in each recess N of the mold K is cured to form the base sheet 1 in the mold K. At this time, the first resin material L1 that does not enter the recess N and overflows becomes a residual film R that covers one main surface (second surface) of the base sheet 1. Subsequently, the base sheet 1 is released from the mold K. A plurality of holes 2 corresponding to the protrusions M of the mold K are formed on the first surface 1a of the obtained base sheet 1 (FIG. 11).

[0044] <Process B> As shown in Figures 12 and 13, a second resin material L2 containing conductive particles and a conductive filler is applied to the first surface 1a of the base sheet 1. At this time, an excess amount of the second resin material L2 that does not fit into the holes 2 is applied to the first surface 1a. Then, as shown in Figures 14 and 15, a portion of the second resin material L2 is injected into each of the holes 2. The remaining portion of the second resin material L2 that does not fit into the holes 2 overflows and covers the first surface 1a of the base sheet 1. The method for injecting the second resin material L2 into the hole 2 is not particularly limited, and examples include a method in which the second resin material L2 is allowed to flow naturally under vacuum while utilizing capillary action, or a method in which the second resin material L2 is forcibly pushed in using pressure degassing or a squeegee. After the injection is completed, the excess second resin material L2 that has not been injected into the holes 2 and remains on the first surface 1a of the base sheet 1 is left as it is on the first surface 1a. As a method for leaving it, for example, a method of placing a frame (not shown) on the first surface 1a and leaving the second resin material L2 inside this frame can be mentioned.

[0045] 14 and 15, a magnetic field may be applied that is approximately parallel to the depth direction of the hole 2 (thickness direction of the base sheet 1), and the conductive particles and conductive filler contained in the second resin material L2 in the hole 2 may be aligned by magnetic force in the depth direction of the hole 2. The magnetic force causes the conductive particles and conductive filler in the hole 2 to be connected at a high density while in contact with each other, and wiring can be formed in the depth direction of the hole 2.

[0046] With the conductive particles forming wiring, the second resin material L2 in each hole 2 and the second resin material L2 left on the first surface 1a are cured, thereby fixing the conductive particles and conductive filler in the resin. As a result, conductive portions 5 are formed in each hole 2 as through-wiring that penetrates the base sheet 1 in the thickness direction, and a conductive layer 7 that is continuous with each of the conductive portions 5 in each hole 2 can be formed on the first surface 1a. The thickness of the conductive layer 7 can be adjusted as desired by changing the amount of second resin material L2 left on the first surface 1a or by slicing the conductive layer 7. The thickness of the conductive layer 7 can be, for example, 1 μm to 50 μm.

[0047] Next, a portion of the conductive layer 7 covering the first surface 1a is removed by etching to form a plurality of protrusions 8 that are independently partitioned from one another. In the example of Figures 1 and 2, the conductive layer 7 on the lines of the lattice pattern was removed so that a plurality of rectangular protrusions 8 are arranged in a vertical and horizontal lattice pattern in a plan view. As a result, one through-wiring is located directly below each protrusion 8, and each pair of protrusion 8 and conductive portion 5 in the through hole 2 is continuous, with no clear boundary between them, and they are integrated.

[0048] Laser processing is a preferred method for etching a portion of the conductive layer 7. A UV laser has a small laser diameter and is particularly suitable for forming minute protrusions 8. The protrusions 8 at the locations irradiated with the processing laser are removed by heat. At this time, since the protrusions 8 contain conductive particles and conductive fillers, they readily absorb the laser and are easily removed. When the protrusions 8 are removed, the first surface 1a is exposed. Since the exposed first surface 1a does not contain conductive particles or conductive fillers, it is relatively difficult to remove.

[0049] Finally, if necessary, the remaining film R remaining on the second surface 1b of the base sheet 1 is removed by cutting, polishing, or other methods, and the outer shape in plan view is adjusted to obtain the desired electrical connector 10 (Figures 1 and 2).

[0050] A conductive layer (not shown) may be formed directly above the second end of the conductive portion 5 exposed on the second surface 1b of the electrical connector 10, for example, by applying a conductive paste containing a carbon material or a metal material and curing it into any planar shape. Alternatively, the periphery of the second end of the conductive portion 5 exposed on the second surface 1b of the electrical connector 10 may be cut or polished to make the second end protrude, thereby forming a protrusion.

[0051] When forming the protrusions with a metal film layer by plating, there are methods such as forming a metal layer film by electroplating on the second surface 2b while leaving the conductive layer 7, or forming a metal layer film by electroless plating on both the first surface 1a and the second surface 1b after slicing without leaving the conductive layer 7. When forming the protrusions by this method, a metal film layer is formed independently on each end, so etching is not necessary.

[0052] [Resin or resin precursor] The resin or resin precursor contained in the first resin material L1 is the main material that constitutes the insulating portion 6 of the base sheet 1. The resin or resin precursor contained in the second resin material L2 is a material that keeps the conductive particles and the conductive filler in contact with each other. The resin precursor is a compound that forms a resin, and examples thereof include monomers that form a resin through a polymerization reaction. Examples of the resin include known curable resins such as photopolymerizable resins, heat-polymerizable resins, active energy ray-polymerizable resins, and catalytic polymerizable resins.

[0053] From the viewpoint of producing a flexible electrical connector 10, the resin of the first resin material L1 is preferably an elastomer. Examples of the elastomer include urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, styrene butadiene rubber, and silicone rubber. Among these, silicone rubber is preferred because it undergoes little dimensional change after removal from the mold, is less likely to warp after removal from the mold, has little compression set, and has high heat resistance. The silicone rubber may be either a condensation type or an addition type.

[0054] The resins or resin precursors contained in the first resin material L1 and the second resin material L2 may be the same or different, but are preferably the same from the viewpoint of improving the adhesion between the conductive portion 5 and the insulating portion 6. Improved adhesion is preferable because it improves the flexibility of the electrical connector 10, making it easier to install it on the terminals of an electronic device. The resin contained in the second resin material L2 is preferably an elastomer. Specific examples of suitable elastomers are the same as those exemplified for the first resin material L1.

[0055] In addition to the resin or resin precursor described above, the first resin material used in each embodiment may contain any substance added to the base material of a conventional electrical connector, such as a catalyst that promotes polymerization of the resin precursor, a crosslinking agent that promotes crosslinking between resins, an antioxidant, a dye, a pigment, a filler, or a leveling agent. These additives may be contained in an amount of, for example, about 0 to 5% by mass based on the total mass of the first resin material. Furthermore, a diluting solvent may be added to the first resin material to improve the coatability of the first resin material to the molding die.

[0056] In addition to the conductive particles, conductive fillers, and resins or resin precursors described above, the second resin material used in each embodiment may contain, for example, surfactants to improve the dispersibility of the conductive particles and conductive fillers, catalysts to promote polymerization of the resin precursor, crosslinking agents to promote crosslinking between resins, antioxidants, dyes, pigments, fillers, leveling agents, etc. These additives may be contained in an amount of, for example, about 0 to 5 mass % based on the total mass of the second resin material. Furthermore, a diluting solvent may be added to the second resin material to improve the coatability of the second resin material to the substrate sheet.

[0057] [How to use the electrical connector] The electrical connector 10, which is an example of the present invention, can be used in the same applications as known electrical connectors, such as for testing the continuity of the terminals of electronic devices, as well as for so-called mounting applications, such as connecting multiple electronic devices (e.g., circuit boards) provided in an electronic device. [Explanation of symbols]

[0058] 1...base sheet, 2...hole, 5...conductive portion, 6...insulating portion, 7...conductive layer, 8...protrusion, 10...electrical connector, F...conductive filler, G...resin composition layer, J...magnet, K...molding die, M...protrusion, N...recess, L1...first resin material, L2...second resin material, O...mold, P...conductive particle, R...residual film

Claims

1. An electrical connector disposed between a connection terminal of a first electronic device and a connection terminal of a second electronic device for electrically connecting them, A substrate sheet and a plurality of conductive portions (excluding those including conductive particles containing a ferromagnetic material), A plurality of through holes are formed through the base sheet from the first surface to the second surface, the conductive portion forms a conductive path that runs along the through hole from the first surface to the second surface, the conductive portion includes an elastomer, conductive particles, and conductive fillers that are thinner and longer than the conductive particles; An electrical connector, wherein the conductive particles are formed solely from a carbon material.

2. The electrical connector according to claim 1 , wherein centerlines of the plurality of through holes are inclined relative to the first surface and the second surface.

3. 3. The electrical connector according to claim 1, wherein the content of the conductive particles relative to the total mass of the elastomer, the conductive particles, and the conductive filler is 50 to 94 mass %.

4. 4. The electrical connector according to claim 3, wherein the content of the conductive filler is 0.01 to 5 mass % relative to the total mass of the elastomer, the conductive particles, and the conductive filler.

5. For 10 randomly selected conductive fillers included in one conductive portion arbitrarily selected from the plurality of conductive portions, 2. The electrical connector according to claim 1, wherein the ratio (L1 / R1) of the longitudinal length L1 (unit: μm) of each conductive filler to the thickness R1 (unit: μm) of each conductive filler, represented by a line segment that bisects the length L1 and intersects with the length L1 at right angles, is calculated, and the average value X of 10 ratios obtained is 10 to 100.

6. 6. The electrical connector of claim 5, wherein for the through hole having one arbitrarily selected conductive portion inside, the ratio (R2 / Y) of the thickness R2 (unit: μm) of the through hole represented by a line segment that intersects perpendicularly while bisecting the length L2 along the center line of the through hole to the average value Y of the lengths L1 (unit: μm) of the 10 conductive fillers is 5 to 500.

7. 7. The electrical connector according to claim 5, wherein the conductive particles have an average particle size of 0.01 μm to 10 μm.

8. 2. The electrical connector of claim 1, wherein a first end of the conductive portion protrudes from the first surface, or a second end of the conductive portion protrudes from the second surface.

9. 2. The electrical connector of claim 1, wherein a first end of the conductive portion on the first surface side is provided with another conductor protruding from the first surface, or a second end of the conductive portion on the second surface side is provided with another conductor protruding from the second surface.

10. 2. The electrical connector according to claim 1, wherein the base sheet is made of silicone rubber.

11. 2. The electrical connector of claim 1, wherein the elastomer is silicone rubber.

12. 2. The electrical connector according to claim 1, wherein the conductive filler is a carbon nanotube, a carbon nanofiber, a metal nanowire, or a metal-plated body.

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