Electrical connector

Abstract

To provide an electrical connector from which metal and elastomer shaving generated during use can be easily removed.SOLUTION: An electrical connector including an elastomer base sheet and a plurality of thin metal wires passing through the base sheet in the thickness direction is provided with a DLC layer on at least one surface of the base sheet. The Martens hardness of the DLC layer formed on the base sheet is preferably 1.70 to 2.50 N / mm2. The dynamic friction coefficient of the DLC layer formed on the base sheet is preferably 0.350 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an electrical connector.

Background Art

[0002] When inspecting the connection between a surface-mounted semiconductor device and a circuit board, a press-contact type connector may be used. As an example of a press-contact type connector, an electrical connector having a hollowed conductive wire can be mentioned (Patent Document 1). Since the tip of the conductive wire is hollowed and flexible, the electrodes (electrode terminals) of the device to be press-connected are less likely to be damaged by contact with the conductive wire of the electrical connector. Also, an electrical connector in which the tip of the hollowed conductive wire is filled with an elastomer and the durability is improved has been disclosed (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the press-contact of the electrode terminal of the device is repeated with respect to the conductive wire of the electrical connector, chips derived from the conductive wire or the electrode terminal are generated. These chips become an obstacle to subsequent use. However, if the main body of the press-contact type connector is made of an elastomer, there is a problem that the chips adhere to the surface of the main body and cannot be easily removed. Also, if the main body is made of an elastomer, there is a problem that the main body is rubbed when the electrode terminal of the device is press-connected, generating chips of the elastomer.

[0005] The present invention provides an electrical connector capable of easily removing chips of metal or elastomer generated during use. [Means for solving the problem]

[0006] [1] An electrical connector comprising an elastomer base sheet and a plurality of fine metal wires penetrating the base sheet in the thickness direction, wherein a DLC layer is provided on at least one surface of the base sheet. [2] The Martens hardness of the DLC layer formed on the base sheet is 1.70 to 2.50 N / mm². 2 The electrical connector described in [1]. [3] The electrical connector according to [1], wherein the coefficient of dynamic friction of the DLC layer formed on the base sheet is 0.350 or less. [4] In a plan view of the surface on which the DLC layer is formed on one of the surfaces, the carbon concentration of the DLC layer formed on the elastomer portion constituting the base sheet is higher than the carbon concentration of the DLC layer formed on the end face of the metal nanowire, as described in [1]. [5] The electrical connector according to [4], wherein the end face of the metal wire protrudes from the surface of the DLC layer. [Effects of the Invention]

[0007] In the electrical connector of the present invention, a diamond-like carbon (DLC) layer is provided on the surface of the elastomer base sheet, so that shavings do not adhere to the elastomer surface but remain on the DLC layer. Since the surface of the DLC layer has lower tackiness (adhesion) than the elastomer, the shavings that remain on the DLC layer can be easily removed by air blowing or the like. In addition, since the surface hardness of the DLC layer is higher than that of the elastomer, it is possible to prevent shavings from penetrating the surface of the DLC layer. Furthermore, since the dynamic friction coefficient of the DLC layer is lower than that of the elastomer, the generation of elastomer shavings can be reduced even if the electrode terminals rub against each other during pressure contact. Moreover, by providing the DLC layer on the surface of the elastomer base sheet, even if chemical components derived from the elastomer seep to the surface, the DLC layer covers that surface, preventing the chemical components from adhering to the electrode terminals of the device. [Brief explanation of the drawing]

[0008] [Figure 1] The image shows an SEM image of the end face of a thin metal wire in the electrical connector of Comparative Example 1, and a mapping image of carbon atoms superimposed on the SEM image (the bright areas are carbon atoms). [Figure 2] The image shows an SEM image of the end face of the metal wire of the electrical connector in Example 1, and a mapping image of carbon atoms superimposed on the SEM image (the bright areas are carbon atoms). [Figure 3] The image shows an SEM image of the end face of the metal wire of the electrical connector in Example 2, and a mapping image of carbon atoms superimposed on the SEM image (the bright areas are carbon atoms). [Modes for carrying out the invention]

[0009] A first aspect of the present invention is an anisotropically conductive electrical connector comprising an elastomer base sheet and a plurality of fine metal wires penetrating the base sheet in the thickness direction. A DLC layer is provided on at least one surface of the base sheet.

[0010] An electrical connector is positioned between the connection terminals of a first device and a second device and is used to electrically connect them. In an electrical connector, a metal wire is a linear component that makes an electrical connection between the connection terminals of the first device and the connection terminals of the second device. Both ends of the metal wire, which are exposed on both sides of the base sheet, contact the electrode terminals of each device. Examples of these devices include semiconductor packages, circuit boards, silicon wafers, passive components, liquid crystal modules, and sensors.

[0011] The base sheet has multiple through-holes that penetrate along its thickness. A single metal wire is joined to the inner wall of each through-hole. "Joined" means that at least a portion of the metal wire is in contact with and held by the inner wall of the through-hole.

[0012] The position of the metal wires in the base sheet, that is, the arrangement and number of through holes in the base sheet, is not particularly limited and can be adjusted as appropriate according to the arrangement and number of connection terminals of the two devices electrically connected by the electrical connector, the pressing force required for crimping, etc. From the viewpoint of ensuring uniformity throughout the electrical connector, it is preferable that the metal wires and through holes are provided at equal intervals in the base sheet.

[0013] Each through-hole penetrates the base sheet parallel or oblique to its thickness direction. "Thickness direction of the base sheet" refers to the direction perpendicular to the main surface. "Main surface" refers to the surface with the largest area. When a through-hole penetrates the base sheet obliquely to its thickness direction, the angle of the through-hole relative to the thickness direction of the base sheet with respect to the perpendicular of one main surface is preferably greater than 0° and 60° or less, more preferably between 1° and 60°, and even more preferably between 10° and 30°. Within this angle range, a stable connection can be easily obtained with a small load, and there is less risk of damaging the terminals of the connected devices. The angle of the through-hole relative to the thickness direction of the base sheet is adjusted as appropriate according to the arrangement of the connection terminals of the two devices electrically connected by the electrical connector. Here, the angle of the through-hole relative to the thickness direction of the base sheet is an average value measured based on images obtained by observing the cross-section of the base sheet with a measuring microscope or other magnifying observation means for five or more through-holes equipped with metal wires.

[0014] The shape of the through-hole, that is, the shape of the cross-section perpendicular to the longitudinal direction of the through-hole, is not particularly limited and can be appropriately set according to the shape of the cross-section of the metal wire joined to the through-hole. Examples include circular, elliptical, triangular, square, rectangular, and polygons with five or more sides.

[0015] The diameter of the through-hole is not particularly limited and is set appropriately according to the diameter of the metal wire joined to the through-hole, for example, 5 μm to 300 μm. If the shape of the through-hole is other than circular, the diameter of the through-hole shall be the length of the widest part of the outer edge (edge ​​of the opening) of the through-hole. The pore diameter of the through holes is the average value measured based on the images obtained by observing five or more through holes that open on the main surface of the base sheet with a magnifying observation means such as a measuring microscope.

[0016] The thickness of the base sheet can be, for example, in the range of 20 μm to 5000 μm, 40 μm to 1000 μm, 60 μm to 500 μm, etc. When it is not less than the lower limit value of the above range, the mechanical strength and rigidity of the electrical connector are improved, and handling becomes easy. When it is not more than the upper limit value of the above range, the length of the fine metal wire is likely to be suitable for improving the high-frequency characteristics. The thickness of the base sheet is the average value measured and averaged for five or more randomly selected thicknesses using a magnifying observation means such as a measuring microscope.

[0017] The material of the base sheet can be arbitrarily selected from known elastomers. For example, synthetic rubbers such as acrylonitrile-butadiene rubber, silicone rubber, chloroprene rubber, ethylene-chloroprene rubber, ethylene-propylene-diene rubber, styrene-butadiene rubber, fluorine rubber, butadiene rubber, isoprene rubber, urethane rubber, etc. can be mentioned. Among these, silicone rubber is preferable because of its high elasticity and excellent heat resistance.

[0018] The fine metal wire is joined to the inner wall of the through hole, extends perpendicular or obliquely to the thickness direction of the base sheet, and is a conductive member that electrically connects the electrode terminals of the devices connected to the respective tips of the fine metal wires exposed on each main surface of the electrical connector. The fine metal wire may be a solid metal wire or a hollow metal wire. In the case of being hollow, when viewed in the longitudinal direction of the fine metal wire, the whole may be hollow, or only the end portion may be hollow and the central portion may be solid. When at least one end of the fine metal wire is hollow, the pressing force when the electrode terminal of the device is press-fitted can be relaxed by the flexibility of the hollow end portion.

[0019] The diameter of the fine metal wire is not particularly limited, and examples include ranges such as 5 μm to 300 μm, 5 μm to 100 μm, 5 μm to 50 μm, etc. If the value is above the lower limit of the above range, it prevents the electrical resistance of the metal wire from becoming excessively high. If the value is below the upper limit of the above range, the rigidity of the metal wire becomes appropriate, reducing damage to the electrode terminals of the device. If the shape of the metal wire is not circular, the diameter of the metal wire shall be the length of the widest part of the outer edge in a cross-section perpendicular to the longitudinal direction of the metal wire. The aforementioned diameter is the average value obtained by measuring the diameter at five or more points on five or more metal nanowires randomly selected from a plurality of metal nanowires using a magnifying observation means such as a measuring microscope.

[0020] In a plan view of any main surface of the base sheet, the distance between two adjacent metal nanowires, i.e., the center-to-center distance (pitch) between metal nanowires, is, for example, 6 μm to 1000 μm. Here, the center-to-center distance is the average value obtained by measuring five or more pairs of adjacent metal nanowires randomly selected from a plurality of metal nanowires, while viewing the main surface of the base sheet of the electrical connector in plan view, using observation means such as a measuring microscope.

[0021] One end face (tip) of the metal wire may be located on one main surface of the base sheet, or it may be located above and protruding from one main surface. The other end face of the metal wire may be located on the other main surface of the base sheet, or it may be located above and protruding from the other main surface.

[0022] The material of the metal wire is not particularly limited and can be arbitrarily selected from known metal materials such as copper, silver, gold, and brass. The metal wire may consist of one type of metal or two or more types of metal. For example, it may be a multilayer metal wire in which the core wire is plated with another metal.

[0023] A DLC layer is provided on at least one of the main surfaces of the base sheet, one of the two main surfaces. The DLC layer may be provided on only a portion of the surface or on the entire surface. Even if it is provided on only a portion, it is preferable that it covers the entire area where the tip of the metal wire is exposed.

[0024] The thickness of the DLC layer is preferably, for example, 0.05 μm to 3.0 μm, more preferably 0.1 μm to 2.5 μm, and even more preferably 0.2 μm to 2.0 μm. If the value is above the lower limit of the above range, the hardness of the DLC layer can be increased. If the value is below the upper limit of the above range, the rigidity of the DLC layer will become excessively high, preventing warping of the base sheet and the DLC layer. The thickness of the DLC layer is the average value obtained by measuring the thickness of five or more randomly selected locations using magnification observation methods such as an electron microscope.

[0025] The Martens hardness (HMs) of the DLC layer formed on the surface of the substrate sheet is 1.70 to 2.50 N / mm². 2 Preferably, 1.75~2.20 N / mm 2 More preferably, 1.80~2.00 N / mm 2 That is even more preferable. If the value is above the lower limit of the above range, it is possible to suppress the shavings from the device's electrode terminals (solder balls, etc.) from becoming embedded in the DLC layer. If the value is below the upper limit of the above range, the electrode terminals of the device will be more flexible when pressed together, which can prevent cracking of the DLC layer.

[0026] The Martens hardness of the DLC layer formed on the surface of the base sheet is the average value of measurements taken at two or more locations in the elastomer portion without metal wires, in accordance with ISO 14577-1. The measurement conditions are as follows: a triangular pyramidal indenter with a ridge angle of 115°, a maximum test force of 10 mN, a set indentation depth of 1 μm, a loading speed of 1.4632 mN / sec, and a temperature of 25°C.

[0027] The coefficient of dynamic friction of the DLC layer formed on the surface of the base sheet should be smaller than the coefficient of dynamic friction of the surface of the base sheet. For example, it is preferably 0.350 or less, more preferably 0.300 or less, and even more preferably 0.250 or less. There is no particular lower limit, but a guideline is 0.150 or higher. A low coefficient of dynamic friction makes it easier for the device's electrode terminals to slip when pressed together and rubbed, which can suppress abrasion of the DLC layer surface and the generation of debris.

[0028] The coefficient of dynamic friction of the DLC layer formed on the surface of the base sheet is the average value of measurements taken at two or more locations on the elastomer portion without metal wires, in accordance with JIS K7125:1999 (Plastics - Films and Sheets - Test Method for Coefficient of Friction). The measurement conditions are: test speed: 100 mm / min, vertical load: 20 g, measurement distance: 60 mm, test piece size: 20 mm x 20 mm, test piece thickness (thickness of the base sheet excluding the DLC layer): 0.15 mm, and mating material: SUS.

[0029] In a plan view of the surface on which a DLC layer is formed on one side of the base sheet, it is preferable that the carbon concentration of the DLC layer formed on the elastomer portion constituting the base sheet is higher than the carbon concentration of the DLC layer formed on the end face of the metal wire. In other words, it is preferable that the thickness of the DLC layer on the end face of the metal wire is thinner than the thickness of the DLC layer on the elastomer portion.

[0030] Since the DLC layer has high resistance and can form a substantial insulator, it is preferable that at least a portion of the end face of the metal wire in contact with the device's electrode terminals is exposed without being covered by the DLC layer, or that the DLC layer is thin even if it covers the entire end face of the metal wire. If it is too thin, it will not function well as an insulator, and a portion of the DLC layer may be removed by friction due to contact with the electrode terminals. Whether a portion of the end face of a metal nanowire is exposed, and the carbon concentration present on the end face of the metal nanowire, can be measured by a known elemental mapping method that combines scanning electron microscopy (SEM) images with energy-dispersive X-ray spectroscopy (EDS).

[0031] The end face of the metal wire on the side where the DLC layer is formed preferably protrudes from the surface of the DLC layer. The degree of protrusion is preferably, for example, 0.1 μm to 30.0 μm, more preferably 0.5 μm to 25.0 μm, and even more preferably 1.0 μm to 20.0 μm. If the end face of the metal nanowire protrudes from the surface of the DLC layer, the carbon concentration of the DLC layer on the end face of the metal nanowire can be reduced, as described above. Furthermore, connectivity to the device's electrode terminals is improved. The extent to which the end face of the metal wire protrudes from the surface of the DLC layer can be confirmed by magnification observation methods such as an electron microscope.

[0032] [Manufacturing method for electrical connectors] The electrical connector according to the present invention can be obtained by known methods for manufacturing electrical connectors, except for forming the DLC layer. The method for forming the DLC layer is not particularly limited and may be formed by known physical vapor deposition methods or chemical vapor deposition methods (e.g., PVD, plasma CVD, etc.). The surface on which the DLC layer will be formed may be subjected to a surface treatment such as ion etching in advance to improve the adhesion of the DLC layer to be formed later. When the end face of the end of a metal nanowire is to protrude from the surface of the DLC layer, it is preferable to perform a known treatment (e.g., laser treatment) to make the end of the metal nanowire protrude from the surface of the base sheet before forming the DLC layer. [Examples]

[0033] [Example 1] Multiple metal wires were arranged in parallel at 50 μm intervals on one surface of a 15 μm thick first resin layer made of silicone rubber formed on a polyethylene terephthalate substrate, with their orientations aligned. As the metal wire, a 25 μm diameter metal wire was used, consisting of a cylindrical core wire made of brass, nickel plating (0.1 μm thick) covering the outer surface of the core wire, and gold plating (0.1 μm thick) covering the outer surface of the nickel plating. Next, a second resin layer made of silicone rubber with a thickness of 15 μm was formed on one surface of the first resin layer on which multiple metal wires were arranged. The second resin layer was then integrated with the first resin layer, and the metal wires were fixed between the first and second resin layers to form a conductive wire-containing sheet. Next, 200 sheets containing metal wires were stacked so that the longitudinal direction of the metal wires was aligned with each other and the metal wires overlapped when viewed in the stacking direction, thereby forming a laminate of metal wire-containing sheets. Next, a precursor sheet with a thickness of 150 μm was obtained by cutting at an angle of approximately 60° with respect to the direction in which the metal wires extended. The precursor sheet has a base sheet made of silicone rubber and a plurality of metal wires that penetrate the base sheet in the thickness direction. Each metal wire is joined to a through hole that penetrates the base sheet in the thickness direction. The angle of the direction in which the metal wires extend intersects the main surface of the precursor sheet was approximately 60°.

[0034] Next, using methane as the film-forming raw material, a DLC layer with a thickness of 0.2 μm was formed on both main surfaces of the precursor sheet using high-frequency plasma CDV at a processing temperature of 70°C, thereby obtaining the electrical connector according to the present invention.

[0035] [Example 2] An electrical connector was obtained in the same manner as in Example 1, except that the thickness of the DLC layer formed on both main surfaces of the precursor sheet was changed to 1.0 μm.

[0036] [Example 3] An electrical connector was obtained in the same manner as in Example 1, except that the thickness of the DLC layer formed on both main surfaces of the precursor sheet was changed to 2.0 μm.

[0037] [Comparative Example 1] The precursor sheet, before the DLC layer was formed, was used as a comparative electrical connector in the following tests.

[0038] The Martens hardness and kinetic friction coefficient of each electrical connector were measured according to the test method described above. The results are shown in Table 1.

[0039] [Table 1]

[0040] For each example of the electrical connector, an elemental map image of carbon atoms at the end face of a representative metal nanowire was created using a scanning electron microscope (JEOL Ltd., JSM-IT200) under the conditions of signal BED-C (backscattered electron detector), incident voltage 15.0kV, working distance 9.6mm, magnification ×2300, and vacuum mode: LowVacuum. As a result, as shown in Figures 1 to 3, the DLC layer formed on the end face of the metal nanowire of the electrical connector according to the present invention was thinner and had a lower carbon concentration than the DLC layer formed on the surrounding elastomer portion (Figure 2; Example 1), and a portion of the end face of the metal nanowire was exposed (Figure 3; Example 2).

[0041] For each example of electrical connectors, connection tests were performed on the electrode terminals (solder balls) of semiconductor devices. Although detailed results are not shown, in all examples, proper electrical connection was possible by pressure contact. Furthermore, the removal of metal shavings generated when pressure contact was repeated was significantly easier in Examples 1-3 compared to Comparative Example 1. In addition, the amount of silicone rubber shavings generated when pressure contact was repeated was significantly less in Examples 1-3 compared to Comparative Example 1.

Claims

1. An electrical connector comprising an elastomer base sheet and a plurality of thin metal wires penetrating the base sheet in the thickness direction, A DLC layer is provided on at least one surface of the aforementioned base sheet. An electrical connector wherein, on the surface of the base sheet on which the DLC layer is provided, at least a portion of the end face of the metal fine wire is exposed without being covered by the DLC layer, or the thickness of the DLC layer formed on the end face of the metal fine wire is thinner than the thickness of the DLC layer formed on the elastomer portion constituting the base sheet.

2. The Martens hardness of the DLC layer formed on the base sheet is 1.70 to 2.50 N / mm². ２ The electrical connector according to claim 1.

3. The electrical connector according to claim 1, wherein the coefficient of dynamic friction of the DLC layer formed on the base sheet is 0.350 or less.

4. The electrical connector according to claim 1, wherein the end face of the metal wire protrudes from the surface of the DLC layer.

Images