JPH09321427A - Manufacture of injection-molded printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the reliability of continuity of the electrical connection between a through hole and a layer by a method wherein an injected molten resin is made to flow in the through hole to press a conductive material to upper and lower circuits and the wall of the through hole. SOLUTION: First, more than one-layer conductive circuits are respectively formed on both surfaces of a plastic film which can stand a molding temperature. Moreover, a land part and a through hole are punched in such a way as to penetrate the land part and the through hole part. After that, a conductive paste 5 is injected in the punched land and through hole parts. A bonding agent is applied on the surface, which comes into contact with a base material resin, of the film and a conductive sheet is formed. The sheet is inserted in a die cavity 8 and a molten resin 6 is injected in the cavity 8 through an injection port 7 to mold the sheet. A conductive material consisting of the paste 5 at that time removes bubbles and cavity parts, which are formed in the through hole part by the pressure of the molten resin flowed in the through hole, and is pressed firmly also to the upper and lower circuits and the wall of the through hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection-molded printed wiring board having a circuit pattern on the surface of a molded product by injection molding, and in particular, conductive paste is applied to lands and through holes to electrically connect layers. The present invention relates to a method for manufacturing a printed wiring board.

[0002]

2. Description of the Related Art A sheet having a conductive circuit formed on the surface of a plastic film is set in an injection molding die, and a molten base resin is injected to obtain an injection molded product, and at the same time a conductive circuit is formed on the surface of the molded product. In the method of manufacturing an injection-molded printed wiring board that integrates sheets, through-hole plating is generally used for electrical connection between the land portion and the through-hole layer. There is also a method in which a circuit sheet and an injection-molded product are integrated, and then a conductive paste is filled and conductive bonding is performed.

[0003]

The through-hole plating of the above-mentioned conventional manufacturing method requires complicated steps and is a factor of high cost. In addition, in the method of filling the conductive paste after the circuit sheet and the injection-molded product are integrated, since sufficient filling pressure is not applied to the paste, bubbles and cavities are generated in the through holes, and the upper and lower circuit conductors are formed. There is a risk of incomplete contact with. INDUSTRIAL APPLICABILITY The present invention eliminates the drawbacks of the prior art and eliminates complicated steps such as through-hole plating, makes electrical connection between through-hole layers inexpensive, and increases reliability. The purpose is to propose a method for manufacturing a wiring board.

[0004]

In order to solve the problems, first, one or more conductive circuits are formed on both surfaces of a plastic film that can withstand the molding temperature by screen printing, plating, etching or the like. Further, punching is performed so as to penetrate the land portion and the through hole portion. Then, a conductive paste is injected into the punched land and the through hole by screen printing, a quantitative supply device such as a dispenser, or the like. Then, an adhesive is applied to the surface in contact with the base resin, and if necessary, a circuit protection solder resist is applied to prepare a conductive circuit sheet. The conductive circuit sheet is inserted into the mold cavity, after positioning, the mold is clamped, and molten resin is injected into the cavity for molding. The conductive material made of the conductive paste at that time removes the air bubbles and the cavity formed in the through hole by the molten resin pressure flowing into the land and the through hole, and the upper and lower circuits and the through hole wall are removed. A method of manufacturing an injection-molded printed wiring board that is pressed firmly is also proposed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The plastic film used for the conductive circuit sheet in the present invention is not particularly limited, but because of injection of high temperature molten resin in injection molding, welding of electronic parts with solder, etc., Those having heat resistance and further excellent flexibility are preferable, and polyethylene terephthalate (PET), polyether sulfone (PES),
Polyetheretherketone (PEEK), aromatic polyamide, polyimide, polyetherimide (PEI),
Films such as polyphenylene sulfide (PPS) can be used. The thickness of this plastic film is usually about 5 to 100 μm, preferably 25 to
It is about 75 μm. In the present invention, the circuit pattern is
Although not particularly limited, it can be formed by conductive paste printing or a method of etching a metal foil, and a circuit pattern is formed on both surfaces of the film. Then, a punched hole is formed so as to penetrate the land portion and the through hole portion.

A conductive paste is injected into the through-holes by a quantitative supply device such as screen printing or a dispenser on the conductive circuit sheet in which the punching holes for the through-holes are formed. The conductive paste injected into the through holes in the present invention is not particularly limited, but silver paste,
Gold paste, copper paste, carbon paste and the like are preferable. Furthermore, an adhesive for bonding the conductive circuit sheet and the base resin is applied to the surface of the conductive circuit sheet on the side in contact with the base resin. The injection-molding base resin used in the present invention is not particularly limited as long as it can be injection-molded, but a resin having a certain degree of heat resistance for soldering electronic parts is preferable, and polycarbonate (P
C), polyethylene terephthalate (PET), aromatic polyamide, polyphenylene sulfide (PPS),
Resins such as polyether sulfone (PES) and polybutylene terephthalate (PBT) can be used.

Further, the adhesive for adhering the base resin and the conductive circuit sheet has compatibility with the base resin and varies depending on the base resin, but they can obtain a strong adhesive force to each other. As in the case of the base resin, it is desirable to have some heat resistance. Specifically, polyester type,
Adhesives such as epoxy type and polyvinyl acetal type can be used. If necessary, the conductive circuit sheet can be coated with a solder resist on the surface opposite to the adhesive application surface. The conductive circuit sheet thus obtained is inserted into the cavity of the mold so that the adhesive application surface is in contact with the molten resin, and the conductive circuit sheet is positioned at a fixed position. The positioning method may be a suction method or a method using a positioning pin. When the positioning is completed, the mold is clamped and the molten resin is injected from the gate. The injected molten resin fills the inside of the cavity to form a molded body. At that time, the molten resin also flows into the through-hole portion and presses the conductive paste having air bubbles or cavities so that the conductive paste is adhered to the through-hole wall surface and the circuit portions on both front and back surfaces.

The molten resin that has flowed into the through-hole portion flows into almost the central portion because the diameter of the through-hole is small, and the conductive paste pressed by the molten resin causes the circuit portion and the wall surface of the through-hole to be almost even. Pressure will be applied, crushing air bubbles and cavities, and making close contact with the through-hole wall surface and the circuit section. The conductive paste is cured by the temperature of the molten resin, but if the curing is insufficient, the conductive paste can be removed from the mold and then cured by heat treatment. According to the present invention, the conductive material composed of the conductive paste injected into the land and the through hole removes the bubbles and the cavity formed in the through hole by the molten resin pressure injected during the injection molding. It As a result, the upper and lower circuits and the through-hole wall are firmly pressed. Therefore, even when heated in the reflow or solder dip step when mounting electronic components after the conductive paste is applied, the bubbles and cavities in the through holes do not become high pressure or expand, and
It is possible to improve the continuity reliability of the electrical connection without causing defects such as cracks in the through holes.

[0009]

EXAMPLE As shown in FIG. 1, a plastic film 1 (PET; thickness 50 μm) has a thickness of 50 μm and a thickness of 35 μm.
A circuit is patterned with an etching resist on both sides of a double-sided copper foil sheet made of a thick copper foil, and a copper foil circuit 2 is formed by etching. After that, a through hole having a hole diameter of 0.8 mm is punched out so as to penetrate with a sharp blade. Then, the conductive paste 5 is injected into the punched through holes by screen printing. The injected conductive paste is brought into a semi-cured state by heating. Then, the adhesive 4 is applied to the surface in contact with the base resin, and the solder resist 3 is formed on the upper circuit protection portion by screen printing to form a conductive circuit sheet. After that, as shown in FIG. 2, the conductive circuit sheet is inserted into the mold cavity 8, and after positioning and mold clamping, the molten base resin 6 is injected from the injection port 7 into the cavity 8 as shown in FIG. 2 (a). Then, molding was performed. As a result, in the through hole as shown in Fig. 2 (b), bubbles and cavities formed in the through hole are removed by the inflowing molten resin pressure, and the conductive paste passes through the upper and lower circuits and the through hole wall. It was also firmly pressed against, and it was possible to obtain an injection-molded printed wiring board without bubbles or voids in the through holes. The types of resins and conductive pastes used in this example and molding conditions are shown below. Resin: PET resin [Dyanite GF-PETMD89301 Mitsubishi Rayon Co., Ltd.] Molding conditions: Mold temperature 100 ° C Molding temperature 270-280 ° C Conductive paste: Polymer conductive paste [Silver conductive paste LS-series Co., Ltd.] Asahi Chemical Research Institute] Adhesives: Polyester adhesives [Pethresin S-110G Takamatsu Yushi Co., Ltd.]

[0010]

According to the method for manufacturing an injection-molded printed wiring board of the present invention, the conductive material made of the conductive paste applied to the through-holes is stored in the through-holes due to the pressure of the molten resin injected during the injection molding. The bubbles and the cavity formed in the are removed. As a result, the conductive paste is pressed firmly against the upper and lower circuits and through-hole walls, so even if the conductive paste is heated during reflow soldering or solder dipping after mounting the conductive paste, bubbles in the through holes The inside of the through hole is free from defects such as cracks and the like, and the voids do not become high in pressure or expand, and conduction defects due to these can be prevented. You can improve. Further, there are great economic effects such as reduction of complicated steps such as through-hole plating for electrical connection between layers.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a conductive circuit sheet used in a process of manufacturing an injection-molded printed wiring board according to an example of the present invention.

FIG. 2 is a cross-sectional view showing the outline of the injection molding process of the method for manufacturing an injection molded printed wiring board according to the example of the present invention.

[Explanation of symbols]

 1. Plastic film 2. Copper foil circuit 3. Solder resist 4. Adhesive 5. Conductive paste 6. Molten base resin 7. Ejection port 8. Cavity

Claims (1)

[Claims] 1. A sheet having a conductive circuit formed on the surface of a plastic film is set in an injection molding die, and a molten base resin is injected to obtain an injection-molded product, and at the same time a conductive circuit is formed on the surface of the molded product. In a method for manufacturing an injection-molded printed wiring board that integrates a sheet, as a conductive circuit sheet,
A sheet having circuits of at least one layer on both sides of a plastic film, forming a through-hole hole penetrating the land portion, and then applying a conductive material made of a conductive paste to form a conductive paste through-hole. Injecting the injected molten resin into the through hole during injection molding allows the conductive material consisting of conductive paste to be pressed firmly against the upper and lower circuits and through hole walls. Manufacturing method of molded printed wiring board.