JPH04328893A - Manufacture of electric circuit molded piece - Google Patents

Abstract

PURPOSE:To enable an electric circuit molded piece to be enhanced in conductivity, free from abnormal heat release, and protected against disconnection caused by abnormal heat release by a method wherein the gate inlet of a mold which molds a conductive resin composition is provided outside an electric circuit effectively distant from it. CONSTITUTION:Synthetic resin is molded into a synthetic resin molded piece 2 provided with a recess where an electric circuit 4 is formed later and another recess located correspondent to the position of a gate. Conductive resin composition is fabricated into the electric circuit 4 in the recess provided to the synthetic resin molded piece 2, and a gate 1 is provided to the recess provided outside the electric circuit 4. A molding process takes place setting metal terminals 5 and 5' as inserts disposed at both the ends of the electric circuit 4. The gate 1 can be provided at an optional position except a part on the electric circuit 4. As the gate 1 is provided outside the electric circuit and distant form it, the electric circuit 4 is not directly affected by the thinness of conductive filler at the gate.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an electrical circuit molded product having excellent conductivity.

0002

[Prior Art] Conventionally, from the viewpoint of productivity and structure, molded products on which electric circuits are formed are made by double-molding a conductive resin composition, for example, in the recesses of synthetic resin moldings, to integrate the electric circuit and the insulating substrate. This method is effective and has been put into practical use.

That is, the conventional electric circuit molded product is as shown in FIG.
As shown in FIG.
Usually, the electric circuit 21 is molded with the gate 22 provided on the electric circuit 21, and current is supplied through metal terminals 23, 23' insert-molded at both ends of the electric circuit.

However, in the conventional electric circuit molded product as described above, the conductive filler such as conductive fibers, metal powder, and carbon black in the conductive resin composition tends to become diluted near the gate 22 due to its orientation. There is. Therefore, when a current is passed through the electric circuit 21, there is a drawback that the thin portion of the conductive filler has poor conductivity compared to other portions. The disadvantage is that the portions with poor conductivity generate a large amount of heat due to electrical resistance, which tends to cause circuit breakage and deformation of the molded product.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and has excellent conductivity, and is free from abnormal heat generation, resulting in disconnection of electrical circuits, and deformation of molded products. The purpose of this invention is to provide a highly productive method for manufacturing electrical circuit molded products.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted extensive research focusing on the relationship between the orientation state of the conductive filler and the conductivity, and have devised an appropriate gate position. It was discovered that by doing so, it was possible to obtain an electrical circuit molded product with excellent conductivity without a thin portion of the conductive filler, and thus completed the present invention.

That is, the present invention provides a method for manufacturing an electric circuit molded article in which an electric circuit is formed by double-molding a conductive resin composition on a synthetic resin molded article, in which a gate for molding the conductive resin composition is formed. This is a method for manufacturing an electric circuit molded product, characterized in that the injection site is molded outside the electric circuit and at an effective interval.

The conductive resin composition used in the present invention is prepared by coating the surface of a conductive filler made of metallic fibers and a low-melting point metal with a thermoplastic resin, and cutting it into pellets. is preferred. By using this composition, when made into a molded product, the metal fibers are fused and bonded by a low melting point metal, exhibiting excellent electrical conductivity, and reducing the decrease in electrical conductivity, especially when changing over time. It is possible.

The following experiment was conducted to confirm the orientation of the conductive filler in the synthetic resin molded article. That is,
1 as shown in FIG.
A 50 x 3 x 4 mm conductive molded product was molded with gate 1 placed in the center in the longitudinal direction, and the molded product was equally divided into 7 blocks on each side with gate 1 at the center (1
Each block (10 mm) was separated and numbered as shown in the figure. When the volume resistivity (Ω·cm) of each block number was measured, it was found that, as shown in FIG. 2, the closer the block number to the gate portion, the higher the volume resistivity.

[0010] That is, it has been found that the conductive filler becomes thinner in the gate portion, and the conductivity deteriorates. Therefore, when obtaining a synthetic resin molded article having an electric circuit using this conductive resin composition, it is important to provide a gate portion outside the electric circuit rather than on the electric circuit. Of course, each electric circuit has a desired resistance value and its tolerance range, so the distance between the electric circuit and the gate position may be determined depending on each electric circuit.

Next, the present invention will be explained with reference to the drawings.

As shown in FIG. 3, a synthetic resin molded body 2 having a recess 3 in which an electric circuit will later be formed and a recess 3a corresponding to a gate position outside the electric circuit is molded using a synthetic resin. The synthetic resins used here include polystyrene resin, A
Thermoplastic resins such as BS resin, polyphenylene oxide resin, and nylon are often used, but they are not particularly limited to thermoplastic resins.

Next, as shown in FIG. 4, an electrical circuit 4 is second-molded using a conductive resin composition in the recess 3 of the synthetic resin molded body 2 shown in FIG. Since the gate 1 is provided facing 3a, the electric circuit 4 is connected from the gate 1
The cecal part 4a is virtually unrelated to the electrical circuit.
is included. During this molding, the electric circuit molded product 6 can be manufactured by placing the metal terminals 5, 5' at both ends of the electric circuit 4 and performing insert molding. The position of the gate 1 may be anywhere as long as it is not on the electric circuit 4, and is not particularly limited.

[0014]

[Function] By the method of manufacturing an electric circuit molded article of the present invention, an electric circuit molded article having excellent conductivity can be manufactured. That is, since the gate portion is separated from and separated from the electric circuit, the electric circuit is not directly affected by the dilution of the conductive filler in the gate portion. Therefore, there is no abnormal heat generation due to non-uniform electrical resistance, and there is no subsequent disconnection or deformation of the molded product.

[0015]

EXAMPLES Next, the present invention will be explained by examples.

EXAMPLE A polystyrene resin molded product having a concave electric circuit forming part was made, and then a gate was formed outside the concave electric circuit forming part using the conductive resin composition Emiclear (manufactured by Toshiba Chemical Co., Ltd., trade name). to form an electrical circuit. Further, at the same time as forming the electric circuit, two metal terminals were placed at both ends of the electric circuit and insert molding was performed to produce the electric circuit molded product shown in FIG. 4. The temperature of the electrical circuit was measured by applying a current of 5 A between the metal terminals of the obtained electrical circuit molded product, and it was the same as the ambient temperature (25° C.), and no abnormal heat generation was observed.

Comparative Example A polystyrene resin molded product having a concave electrical circuit forming part was made, and then a conductive resin composition Emi-Clya (manufactured by Toshiba Chemical Co., Ltd., trade name) was used to form an electrical circuit on the electrical circuit as shown in FIG. At the same time, two metal terminals were placed at both ends of the electric circuit and insert molding was performed to produce an electric circuit molded product. When the temperature of the electric circuit was measured using this molded article in the same manner as in the example, it was found to generate heat to 56°C, an increase of 31°C from the ambient temperature (25°C).

[0018]

[Effects of the Invention] As is clear from the above explanation, according to the method for manufacturing an electric circuit molded product of the present invention, it has excellent conductivity,
An electrical circuit molded product with good productivity can be obtained without abnormal heat generation due to large current, subsequent disconnection, or deformation of the molded product.

[Brief explanation of drawings]

FIG. 1 is a plan view of a test piece molded product for measuring the distribution state of a conductive filler.

2 is a curve diagram showing the volume resistivity of each block in the molded product of FIG. 1. FIG.

FIG. 3 is a perspective view showing an example of a synthetic resin molded article used in the method of the present invention.

FIG. 4 is a perspective view showing an example of an electric circuit molded product obtained by the method of the present invention.

FIG. 5 is a perspective view showing a conventional electric circuit molded product.

[Explanation of symbols]

1,22 Gate 2,20 Synthetic resin molded body 3 Recessed part 4,21 Electric circuit 5, 5', 23, 23' Metal terminal 6 Electric circuit molded products

Claims (1)

[Claims] Claim 1. A method for manufacturing an electric circuit molded article, in which an electric circuit is formed by double-molding a conductive resin composition on a synthetic resin molded article, in which an electrically conductive resin is applied to the injection point of a gate where the conductive resin composition is molded. A method for manufacturing an electric circuit molded product, characterized in that the molded product is molded outside the circuit at an effective interval.