JPH05298945A - Manufacture of electric circuit molding - Google Patents

Abstract

PURPOSE:To provide the manufacture for electric circuit moldings usable as physical solid wiring circuit excellent in conductivity, by directly joining plural conductive moldings. CONSTITUTION:Resin compositions, composed by blending concuctive metallic fibers and low-melting point metal with thermoplastic resin, are injection molded by using a mold having a given shape, and straight or curved rodlike conductive molding 2 and 3, having a jointing part 1, like e.g. the combination of conical recessed and protuded parts, in one side end part, are formed respectively. Next, the joining part 1 of these moldings 2 and 3 are locally heated with hot air devices respectively to expose conductive metallic fibers from surfaces. Then the joining parts 1 of both the sides are engaged and pressure-contacted, and also is heated at temperature higher than the melting point of the thermoplastic resin and the low-melting point metal to be welded with an ultrasonic welding device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molded article for an electric circuit having good conductivity.

[0002]

2. Description of the Related Art Conventionally, in order to form an electric circuit on a resin molded body, a method of forming a circuit on the surface of the molded body by transferring a conductive paste or plating a conductive metal, or a processed product of a metal plate. For example, a method of attaching a metal terminal or a method of attaching a metal terminal and connecting between the terminals with a resin-coated electric wire such as vinyl chloride resin is used. Among them, the method using a resin-coated electric wire is generally used because the shape of the wiring can be freely changed and a circuit can be formed by a simple operation.

[0003]

However, in the molded product in which the electric circuit is formed in this way, the resin-coated electric wire is not flexible and does not have the wiring shape from the beginning, so that the productivity is poor. .. That is,
To form an electric circuit with resin-coated electric wires, bend and twist it manually to form a predetermined wiring shape,
Since it is connected and fixed to the surface of the resin molded body through terminals and a band or the like is provided in the middle of the wiring for positioning, there is a problem that automation is difficult and productivity is not improved.

On the other hand, as an alternative to such an electric circuit molded article, a molded article made of a conductive resin has been considered and studied. Here, as the conductive resin, two types can be considered: one in which a conductive metal fiber is mixed with a thermoplastic resin or the like, and one in which a conductive powder such as carbon is mixed.

However, although the former molded article made of a resin material mixed with conductive metal fibers has relatively good conductivity, the contact surface with other parts required for circuit formation is covered with the resin layer. The exposed surface is exposed to a very small amount of conductive metal fibers. Therefore, it has been necessary to attach the metal terminal by a method such as insert molding or insert after molding, and to connect through it. In addition, in order to form a circuit by joining the molded bodies together, it is necessary to increase the amount of the conductive metal fiber compounded, or to remove the resin layer on the surface of the joined portion by cutting with a blast treatment or a cutter. The method of performing blasting not only deteriorates the characteristics of the material, but also has a problem in terms of formability and cost, and the method of cutting and removing with a cutter or the like has processing restrictions, and the conductive metal fibers must be sufficiently removed. There was a problem that it could not be exposed. Further, in the latter case of the molded body made of the resin material mixed with the conductive powder, there is a problem that good conductivity cannot be obtained with a blending amount that maintains sufficient mechanical properties.

The present invention has been made to solve these problems, and provides an electric circuit molded product which can be used as a three-dimensional wiring circuit having excellent conductivity by directly bonding a plurality of conductive molded products. It is intended to provide a method for manufacturing.

[0007]

The method for producing an electric circuit molded article according to the present invention has a conductive resin composition containing a thermoplastic resin as a main component and a conductive metal fiber and a low melting point metal, respectively, and having a joint portion. After molding into a predetermined shape, at least one joint of the obtained plurality of conductive molded bodies is locally heated to expose the conductive metal fibers from the surface, and then these joints are pressed against each other. However, the pressure contact portion is heated to a temperature higher than the melting points of the thermoplastic resin and the low melting point metal to be welded.

In the present invention, as the thermoplastic resin which is the base of the conductive resin composition, polyethylene, polypropylene, ABS (acrylonitrile-butadiene-styrene copolymer) resin, polyphenylene sulfide,
Polyphenylene oxide or the like is used. Further, as the conductive metal fiber blended in such a thermoplastic resin, there is a fiber such as copper or stainless steel, and as the low melting point metal, there are tin, lead, solder and the like. Here, in order to mix the low melting point metal, it is preferable to add and mix it in the form of a masterbatch. Further, it is desirable that the content of the above-mentioned conductive metal fiber is such that the volume resistivity is 10 ⁻³ Ωcm or less, and a molded product having sufficient conductivity for an electric circuit can be obtained. The metal content is preferably 5 to 20% by weight of the total resin composition.

In the present invention, the shape of the joint portion of the conductive molded body made of such a conductive resin composition is such that the positioning is easy in consideration of the workability of pressure welding and heat welding described later, and the bonding is performed. In order to reduce the electric resistance value of the portion, it is desirable to have a shape in which irregularities are combined so that the contact surface area becomes large.

In the present invention, as a method of locally heating the joint portion of such a conductive molded body, for example, a method of directly blowing hot air having a temperature higher than the melting point of the thermoplastic resin using a hot air device is used. is there. Further, in order to heat-weld the joint portion of the conductive molded body thus heated, for example, a method of applying ultrasonic vibration to generate heat by vibration friction can be adopted. And in such heating,
Conditions are set so that the thermoplastic resin and the low melting point metal in the conductive resin of the pressure-bonded joint portion are instantaneously heated to a temperature higher than the melting point. That is, if the heating temperature at the time of welding is too high, the conductive resin around the joint is melted in a wide range and deformation of the molded body occurs. It is heated and welded using a means capable of precise temperature control.

[0011]

In the production method of the present invention, first, a conductive resin composition in which a conductive metal fiber and a low melting point metal are mixed with a thermoplastic resin is molded by a method such as injection molding,
A conductive molded body having a predetermined shape having a joint for bonding the molded bodies together is formed. In the obtained conductive molded article, the conductive metal fibers dispersed in the thermoplastic resin are bonded to each other through the interposition of the low melting point metal and are present in the form of a mesh, and have good conductivity. Shown. Then, the desired joint portion of the obtained plurality of conductive molded bodies,
The resin layer on the surface is melted by locally heating with a hot air device or the like. As a result of such heating and melting of the resin layer, the stress remaining inside the resin layer due to being stretched at the time of molding is relaxed, and in the surface where the conductive metal fiber is present immediately below the resin layer, Since the temperature of the resin tends to rise due to the difference in specific heat, the resin layer covering the conductive metal fibers in the joint is torn, and the conductive metal fibers are exposed from the surface of the joint.
Then, after such a heat treatment is performed on one side or both sides of the conductive molded body to be bonded, the ultrasonic welding device or the like is used to heat the pressure-bonded part while pressure-bonding these bonded parts together. It is heated to a temperature higher than the melting points of the plastic resin and the low melting point metal to be welded. Thus, in the pressure-bonded joint portion of the conductive molded body, the conductive metal fibers are directly contacted to each other without interposing the resin layer, and are heated to a temperature higher than the melting points of the thermoplastic resin and the low melting point metal. As a result, the low-melting-point metal covering each conductive metal fiber is melted, so that the conductive metal fiber is firmly bonded through the melted low-melting-point metal, and good electrical connection can be obtained. Further, at this time, since the resin layers of the pressure-bonded joints are also melted and adhered to each other, a sufficient mechanical connection strength between the molded products can be obtained, and an electric circuit molded product having excellent electromechanical properties can be formed. It

[0012]

Embodiments of the present invention will be described below with reference to the drawings. In the examples, first, a conductive resin prepared by blending a conductive metal fiber with a thermoplastic resin, for example, Emilia (trade name of Toshiba Chemical Co., Ltd.), a low melting point metal such as tin, lead, or solder is added. A conductive resin composition added in a proportion of 10% by weight in the form of a masterbatch is injection-molded using a mold having a predetermined shape, and as shown in FIG. Straight rod-shaped and bent rod-shaped conductive molded bodies 2 and 3 each having a joint portion 1 were molded. That is, the conical recess 4 as shown in FIG. 2A, or the conical recess 4 shown in FIG. 2B or FIG. 2C in the end joint portion 1 of the one straight rod-shaped conductive molded body 2. Such a solid cylindrical convex portion 5 or a hollow cylindrical boss portion 6 is formed,
In the joint portion 1 of the other bent rod-shaped conductive molded body 3, the convex portion 7 or the through hole 8 having a corresponding shape was formed.
Next, the joint portions 1 of the rod-shaped and bent rod-shaped conductive molded bodies 2 and 3 thus molded are locally heated by a hot air device to melt the resin layer on the surface, and the conductive metal fibers are surfaced. Exposed from. After that, FIG.
As shown in (c), the joining portions 1 of both the conductive molded bodies 2 and 3 are fitted, and the thermoplastic resin and low resin are applied by an ultrasonic welding device while pressure-welding using a heating jig 9 or the like. Melting point 1 Joint part 1 heated at a temperature higher than the melting point of metal and pressure-welded
Was welded.

In the joint portion of the conductive molded bodies 2 and 3 thus heat-welded, the exposed conductive metal fibers are in direct contact with each other and cover each conductive metal fiber at the time of heat-welding. Since the low-melting-point metal is melted and the conductive metal fibers are firmly bonded through the melted low-melting-point metal, as is apparent from the measurement examples below, good electrical connection can be obtained. That is, using a test piece having a width of 5 mm and a thickness of 3 mm, the joint was locally heated by hot air treatment and then ultrasonic heating welding was performed in the same manner as in Example, and the ultrasonic wave was immediately applied without performing hot air treatment. The electrical resistance of the welded portion was measured for each of the three cases where welding was performed and when ultrasonic welding was performed after the surface of the joint was blasted. In addition, a metal terminal was press-fitted into the measurement section, and the measurement was performed at a terminal distance of 100 mm. The measurement results are shown in the table below.

[0014] Further, in the electroconductive molded articles obtained in the examples, since the resin layers of the pressure contact portions are also welded to each other, the mechanical connection between the respective molded articles is made firm. Then, in the electrically conductive molded product electrically and mechanically connected in this manner, as shown in FIG. 4, the metal terminals 10 are press-fitted into at least two end portions, and the resin-coated electric wires 11 are inserted into these terminals 10.
An electric circuit can be formed by connecting and connecting the power source 12 and the like. Furthermore, by standardizing the length and cross-sectional area of each conductive molded body and combining these, various three-dimensional circuits can be formed.

[0015]

As described above, according to the present invention, it is possible to obtain an electric circuit molded product having excellent conductivity of individual conductive molded products and joints and high mechanical connection strength. In addition, various three-dimensional electric circuits can be formed, and the productivity is high.

[Brief description of drawings]

FIG. 1 is a perspective view showing a conductive molded body molded in a first step in an embodiment of a method for manufacturing an electric circuit molded product of the present invention.

FIG. 2 is a cross-sectional view showing the shape of a joint portion of a molded conductive molded body in the example of the present invention.

FIG. 3 is a cross-sectional view showing a method of heat welding while pressing the joint portion of the conductive molded body in the embodiment of the present invention.

FIG. 4 is a perspective view showing a conductive molded product obtained in an example.

[Explanation of Codes] 1 ......... Jointed portion 2 ......... Continuous rod-shaped conductive molded body 3 ………… Bent rod-shaped conductive molded body 4 ……… Conical concave portion 5 ……… Solid cylindrical convex portion 6…. …… Hollow cylindrical boss 7 ………… Projection 8 ………… Through hole 9 ………… Heating jig 10 ………… Metal terminal 11 ………… Resin coated electric wire 12 ………… Power supply

Claims (1)

[Claims] 1. A plurality of conductive moldings obtained by molding a conductive resin composition mainly composed of a thermoplastic resin and containing a conductive metal fiber and a low melting point metal into a predetermined shape having a joint. At least one joint part of the body is locally heated to expose the conductive metal fibers from the surface, and then these joint parts are pressed against each other, and the press contact part is more than the melting point of the thermoplastic resin and the low melting point metal. A method for producing an electric circuit molded article, which comprises heating to a high temperature and welding.