JP2012216591A - Conduction method between conductive resin and metal component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in electrical contact resistance even if repeatedly exposed to an environment having a large temperature difference when a conductive resin whose whole surface is covered with an insulation layer and a metal component are made electrically conductive through each other.SOLUTION: Disclosed is a conduction method between the metal component 2 and the conductive resin 10 which is molded by mixing a conductive fiber Pb having conductivity and a low melting point metal Pc having a melting point lower than this conductive fiber Pb and excellent wettability with this conductive fiber Pb with each other and whose whole surface is covered with the insulation layer S. The metal component 2 is assembled to this conductive resin 10 so as to penetrate through the insulation layer S and heated so that the low melting point metal Pc in the vicinity thereof is fused while this assembled state remains as it is.

Description

  The present invention relates to a conduction method between a conductive resin and a metal part. Specifically, a conductive fiber having conductivity and a low melting point metal having a melting point lower than that of the conductive fiber and good wettability with the conductive fiber are mixed, and all of the molded surfaces are formed. A conduction method between a conductive resin covered with an insulating layer and a metal part.

  2. Description of the Related Art Conventionally, a conductive resin formed by mixing a conductive fiber with a thermoplastic resin has been used as a material for shielding an electromagnetic wave generated from an electronic device from being released to the outside. Patent Document 1 below discloses a case in which a cover made of such a conductive resin is used as a part of a case for housing an electronic device. Since a large number of conductive fibers in the conductive resin are distributed so as to be in contact with each other, as a whole, it has a network structure having conductivity, and exhibits an electromagnetic shielding property that can be approximated to a conductor plate. . Cases using such conductive resins are widely used because they are lighter than metal cases and can be easily molded by ordinary injection molding.

  Moreover, in order to ensure conduction | electrical_connection between the conductive fibers in the above conductive resins, mixing a low melting metal further in a conductive resin is performed. Patent Document 2 below discloses such a conductive resin. The low melting point metal preferably has a melting point lower than that of the conductive fiber and good wettability with the conductive fiber, and the low melting point metal in the conductive resin melts and adheres to the conductive fiber during molding. As a result, the conductive fibers are bonded to each other through the low melting point metal and the conduction is more reliable, so that the electromagnetic wave shielding property of the conductive resin is improved.

  Here, as shown in FIG. 4, a case 103 of an electronic device is provided by providing a cover 102 made of conductive resin including conductive fibers 102 a and a low melting point metal 102 b so as to cover the metal base member 101. Think of making up. In this case, in order to shield electromagnetic waves, the conductive resin of the cover 102 needs to be electrically connected to the metal of the base member 101 so as to be electrically integrated. However, in general, a molded product of a conductive resin formed by mixing the conductive fibers 102a is covered with a so-called insulating layer that does not include the conductive fibers 102a in the molding process. Due to the presence of the insulating layer, the internal conductive portion and the outside are electrically isolated from each other. Therefore, the cover 102 is simply not in contact with the metal base member 101 simply by contacting the cover 102. For this reason, as shown in FIG. 4, a conductive surface 105 is exposed by opening a fastening hole with a bolt 104 in the cover 102, and a metal collar 106 is brought into contact with the surface 105. Conduction between the cover 102 and the base member 101 via the collar 106 has been performed.

JP 2003-163383 A JP 2005-264097 A

However, according to the above-described technique, the conductive resin cover 102 and the metal collar 106 have different coefficients of thermal expansion, so that contact failure occurs between the two when exposed to an environment with a large temperature difference. There is a problem that the electrical contact resistance gradually increases.
The present invention has been made in view of such a point, and in a case where a conductive resin whose entire surface is covered with an insulating layer and a metal part are electrically connected, an environment with a large temperature difference is created. It is an object to suppress an increase in electrical contact resistance even when repeatedly exposed.

First, the first invention of the present invention is formed by mixing conductive fibers having conductivity and a low melting point metal having a lower melting point than the conductive fibers and good wettability with the conductive fibers, This is a conduction method between a conductive resin and a metal part, in which all of the molded surface is covered with an insulating layer,
Assemble the metal parts to penetrate the insulating layer to this conductive resin,
The metal part is heated so that the low melting point metal in the vicinity is melted in this assembled state.

  According to this configuration, since the molten low melting point metal adheres to the metal part, the low melting point metal and the metal part are firmly bonded after the metal part is cooled. Therefore, when electrically conducting the conductive resin and the metal part, it is possible to suppress an increase in electrical contact resistance even when repeatedly exposed to an environment with a large temperature difference.

According to a second aspect of the present invention, there is provided a conduction method between the conductive resin and the metal part according to the first aspect, wherein the heating is induction heating on the metal part.
According to this structure, it can heat simply by the induction heating using the property of metal parts.

According to a third aspect of the present invention, there is provided a conduction method between the conductive resin according to the first or second aspect and a metal part, wherein the metal part is a screw, and the assembly is performed by connecting the screw to the conductive part. It is carried out by screwing into a functional resin.
According to this configuration, the contact with the inside of the conductive resin can be easily obtained by the screw.

According to the first aspect of the present invention, the electrical contact resistance between the conductive resin and the metal part is reduced even when repeatedly exposed to an environment with a large temperature difference.
According to 2nd invention, it can heat simply by the induction heating using the property of metal parts.
According to the third invention, the contact with the inside of the conductive resin can be easily obtained by the screw.

The perspective view which shows the case which shields electromagnetic waves. Sectional drawing which cut | disconnects and shows the case of FIG. 1 by the plane which passes a tapping screw. The figure which shows the method of obtaining conduction | electrical_connection with a case and a tapping screw. Sectional drawing which shows the case which shields the conventional electromagnetic waves.

A mode for carrying out the present invention will be described with reference to FIGS. 1 to 3. Case 1 of the present embodiment is a case for housing an electronic device. The case 1 is formed of a material having an electromagnetic shielding property, and can shield the electronic device so that the electromagnetic wave generated from the electronic device is not emitted to the outside and the electronic device is not affected by the external electromagnetic wave.
The case 1 includes a metal base member 11 and a cover member 10 made of a conductive resin P provided to cover the base member 11. The cover member 10 has a flange portion, and the flange portion is fastened to the base member 11 by a plurality of bolts 12. As will be described later, in a contact portion between the base member 11 and the cover member 10, a metal tapping screw 2 for continuity between the base member 11 and the cover member 10 is embedded.

FIG. 2 is a cross-sectional view showing the case 1 of FIG. 1 cut along a plane passing through the tapping screw 2. The cover member 10 is made of the conductive resin P as described above. As schematically shown in FIG. 2, the conductive resin P is a material in which conductive fibers Pb as a conductive filler and a low melting point metal Pc are distributed in a thermoplastic resin Pa. As shown in FIG. 2, the conductive fibers Pb distributed in the conductive resin P have a fine network structure having conductivity as a whole, whereby the conductive resin P can be approximated to a conductor plate. Exhibits electromagnetic shielding properties. The conductive resin P is injection-molded by mixing the conductive fiber Pb and the low melting point metal Pc in the thermoplastic resin Pa material. Since the thermoplastic resin Pa preferentially adheres to the mold during this injection molding, the entire surface of the molded product is covered with an insulating layer called a skin layer that does not contain the conductive fibers Pb and the low melting point metal Pc. FIG. 2 shows the insulating layer S formed on the cover member 10 in this way.
The low melting point metal Pc is a metal having a melting point lower than that of the conductive fiber Pb and good wettability with the conductive fiber Pb. Therefore, the low melting point metal Pc is melted at the time of molding and adheres to the conductive fiber Pb. Some conductive fibers Pb distributed in the conductive resin P are electrically connected to each other by direct contact. However, as described above, the low melting point metal Pc adheres to the conductive fibers Pb, so that many conductive fibers Pb. Pb couples to each other through the low melting point metal Pc, and conduction between the conductive fibers Pb is more reliable.

  As shown in the partially enlarged view in FIG. 2, a metal tapping screw 2 is screwed into the flange portion 10 a of the cover member 10 so as to penetrate the insulating layer S covering the cover member 10. The “metal part” in the present invention corresponds to this tapping screw. The tapping screw 2 includes a screw portion 21, a handle portion 22, and a flange portion 23. The screw portion 21 is in direct contact with the inside of the cover member 10, and particularly a low melting point metal Pc in the conductive resin P is fixed to the screw portion 21 as described later. Thereby, the conduction | electrical_connection between the part (conductive fiber Pb and low melting-point metal Pc) which has the electroconductivity in the cover member 10, and the tapping screw 2 is obtained, and these are the same electric potential. Further, the flange portion 23 and the handle portion 22 of the tapping screw 2 are kept in contact with the metal base member 11 by the fastening force of the bolt 12. Thereby, conduction between the tapping screw 2 and the base member 11 is obtained, and these are at the same potential. Therefore, the case 1 generally composed of the metal base member 11 and the conductive cover member 10 has the same potential as a whole and exhibits an electromagnetic wave shielding effect.

  Hereinafter, a method for establishing electrical connection between the cover member 10 (the conductive fibers Pb having conductivity in the cover member 10 and the low melting point metal Pc) and the tapping screw 2 will be described. First, as shown in FIG. 3A, the tapping screw 2 is screwed into the cover member 10 made of conductive resin P so as to penetrate the insulating layer S covering the cover member 10. Thereby, the threaded portion 21 of the tapping screw 2 is in direct contact with the portion where the conductive fiber Pb and the low melting point metal Pc in the cover member 10 are distributed. Next, the tapping screw 2 screwed in this way is heated by the induction heating (IH) principle using the induction heating device 3. As shown in FIG. 3B, the induction heating device 3 includes a coil 31 and an AC power supply 32 that causes an AC current to flow through the coil 31. An eddy current is induced in the tapping screw 2 and the cover member 10 (conductive fiber Pb and low melting point metal Pc) in the vicinity thereof by winding a coil 31 around the handle portion 22 of the tapping screw 2 and causing an alternating current to flow from the AC power supply 32. These tapping screws 2 and the cover member 10 in the vicinity thereof are heated by Joule heat generated by the eddy current. By this heating, the thermoplastic resin Pa and the low melting point metal Pc in the vicinity of the screw part 21 are melted, and in particular, the low melting point metal Pc having good wettability with the metal adheres to the metal screw part 21. Next, by cooling the tapping screw 2, the low melting point metal Pc is firmly fixed to the screw portion 21 as shown in FIG. That is, the low melting point metal Pc and the screw portion 21 show a strong bonding force between metals. The conductive state between the cover member 10 and the tapping screw 2 shown in FIG. 2 is obtained as described above. Since the low melting point metal Pc and the screw portion 21 are firmly bonded, contact failure between the low melting point metal Pc and the screw portion 21 does not occur even when repeatedly exposed to an environment with a large temperature difference. An increase in electrical contact resistance can be suppressed.

The form for implementing this invention is comprised as mentioned above.
According to this configuration, the tapping screw 2 is screwed into the cover member 10 made of the conductive resin P so as to penetrate the insulating layer S covering the cover member 10, and the tapping screw 2 is heated by the principle of induction heating. The low melting point metal Pc in the vicinity of the screw portion 21 melts and adheres to the metal screw portion 21. Thus, when the tapping screw 2 is cooled, the low melting point metal Pc and the tapping screw 2 are firmly bonded. Therefore, an increase in electrical contact resistance can be suppressed even when repeatedly exposed to an environment with a large temperature difference.
Furthermore, it can be easily heated by induction heating utilizing the properties of the tapping screw 2 as a metal part. Further, the tapping screw 2 can easily contact the inside of the cover member 10.

In addition, the conduction | electrical_connection method which concerns on this invention is not limited to said embodiment, It can implement with other various forms. In the above embodiment, the heating is performed by induction heating, but the heating may be performed by a heating method other than this. This heating is sufficient if only the conductive resin in the vicinity of the tapping screw 2 can be heated.
Moreover, in the said embodiment, the part which has the electroconductivity inside the cover member 10, and the tapping screw 2 which is a metal component by the method of screwing the tapping screw 2 so that the insulating layer S which covers the surface of the cover member 10 may be penetrated. However, the cover member 10 may be processed by a method such as cutting to expose a conductive part and contact the metal part therewith.

DESCRIPTION OF SYMBOLS 1 Case 10 Cover member 10a Flange part 11 Base member 12 Bolt 2 Tapping screw 21 Screw part 22 Handle part 23 Claw part 3 Induction heating device 31 Coil 32 AC power supply P Conductive resin Pa Thermoplastic resin Pb Conductive fiber Pc Low melting point metal Pc Low melting point alloy S Insulating layer

Claims (3)

A conductive fiber having conductivity and a low melting point metal having a melting point lower than that of the conductive fiber and good wettability with the conductive fiber are mixed and molded, and all of the molded surfaces are insulating layers. A conductive method between a covered conductive resin and a metal component, in which the metal component is assembled so as to penetrate the insulating layer with respect to the conductive resin, and the nearby low melting point metal melts in this assembled state. A method for conducting a conductive resin and a metal part, wherein the metal part is heated as described above. 2. The conduction method between a conductive resin and a metal part according to claim 1, wherein the heating is induction heating with respect to the metal part. 3. A conduction method between a conductive resin and a metal part according to claim 1 or 2, wherein the metal part is a screw, and the assembly is performed by screwing the screw into the molded product. A conductive method between a conductive resin and a metal part.

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