JPS63254790A - Manufacture of electronic circuit structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of manufacturing an electronic circuit structure using injection molding and transfer.

[Prior art and its problems]

Conventionally, there is a known method of manufacturing an injection molded circuit board by setting a circuit transfer foil in a mold and performing injection molding, and then transferring the circuit transfer foil to an injection molded body (Japanese Patent Application Laid-Open No. 60-121
No. 791 1).

The injection molded circuit board obtained by this method can have any shape, for example, a box-shaped circuit that also serves as a case for an electronic circuit, since the injection molded body corresponds to an insulating substrate in a normal circuit board. There is an advantage that the substrate can also be configured.

By the way, when mounting components on such an injection molded circuit board, it is necessary to coat the pads of the transferred circuit with solder, place the components, and solder them by passing them through a reflow oven or the like. become. However, in the case of injection molded circuit boards, the injection molded body is usually three-dimensional, so it is difficult to place components and heat them for soldering compared to conventional flat circuit boards. be. Especially when the transferred circuit is three-dimensional (for example, when the circuit is transferred from the bottom to the side of the inner surface of the case), it is extremely difficult to place and solder components on the circuit surface, and the three-dimensional circuit also becomes difficult to place and solder. As a result, the original feature of being configurable is lost.

Furthermore, since the components are mounted after injection molding, it is necessary to use a resin with extremely high heat resistance that can withstand the heat of soldering as the injection molding material, which also has the disadvantage of increasing costs.

[Means for solving problems and their effects]

The present invention provides a method for manufacturing an electronic circuit structure that solves the problems of the prior art as described above. This method is characterized in that a transfer sheet is set in a mold and injection molding is performed, and the transfer circuit unit is transferred to the injection molded body as a whole.

That is, in the present invention, components are mounted in advance at the stage of making a transfer sheet, and there is no need to mount the components after injection molding.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, a transfer circuit unit 11 as shown in FIG. 1 is created.

This transfer circuit unit) 11 has a conductor layer 13 with a desired circuit pattern formed on one side of an insulating sheet 12, an insulating layer 14 filling the recesses between them, and a pad portion 15 and a solder resist layer 16 formed thereon. , an adhesive layer 17 for an injection molded body, which will be described later, is provided on the opposite surface of the insulating sheet 12. The conductor layer 13 and band portion 15 are formed by printing conductive paste, and the insulating layer 14 and solder resist layer 16 are formed by printing insulating paste and solder resist, respectively.

Next, as shown in FIG.
Components 19 such as an LSI, RC, capacitor, and resistor are placed thereon, and the terminal portions 20 of the components 19 are soldered to the pad portions 15. This component mounting can be easily carried out since the transfer circuit unit 1 is flat.

Note that it is preferable to use a surface-mount type component as the component 19. Next, a pressure receiving layer 21 is formed so as to embed the component 19 therein. This pressure-receiving layer 21 is intended to prevent the transfer circuit unit 11, components 19, or their soldered parts from being damaged by injection pressure, and may be made of silicone rubber or polybutadiene resin. can. A carrier film 23 that grows a release layer 22 on the inner surface is further laminated on top of the pressure-receiving pressure 7121.

The transfer sheet 24 is completed by using a cellulose resin as the release layer 22 and a polyethylene terephthalate film, a polyimide film, or the like as the carrier film 23.

Next, as shown in FIG. 3, this transfer sheet 24 is set on the inner surface of one of the molds 25 and 26, and then the cavities of the molds 25 and 26 are filled with molten resin 27. Since the transfer sheet 24 used for injection molding is flexible, when the inner surface of the mold 25 is bent, the transfer sheet 24 can be bent accordingly. However, it is desirable to avoid bending the part where components are mounted.

After injection molding, when the molds 25 and 26 are removed, the transfer sheet 24 and the injection molded body 28 are integrated with the adhesive layer 17 as shown in FIG. 4, and the carrier film 23 is then peeled off. Then, an electronic circuit structure 29 in which the transfer circuit unit 11, the component 19, and the injection molded body 28 are integrated can be obtained. The pressure-receiving layer 21 may then be removed, or may be left as is if there is no problem with heat dissipation from the component 19. If the pressure-receiving layer 21 is left, it also acts as a moisture barrier layer.

As the injection molded article, a suitable material can be selected from thermoplastic resins, thermosetting resins, and the like. For the former, ABS
(acrylic butadiene styrene) resin, PET (polyethylene terephthalate), PP (polypropylene)
, engineering plastics such as PC (polycarbonate), as well as PEr (polyetherimide), P
Uses heat-resistant engineering plastics such as S (polysulfone), PE5 (polyethersulfone), and PAS (polyallylsulfone), as well as alloys of these polymers and materials mixed with inorganic substances such as glass fiber, talc, and clay. can. As the latter, polyurethane and polyester resins are preferred, and inorganic substances mixed therein can also be used.

Note that when mounting the component 19, depending on the size and shape of the component to be mounted, there is a problem such as the transfer sheet shrinking due to heat during mounting. To deal with this, a rigid protective layer may be provided on the outside of the adhesive layer 17 shown in FIG. 2, and then an adhesive layer may be provided on the outside.As the protective layer, Aj! A metal film such as a Cu film, a composite film in which a metal is deposited on a plastic film, a plastic film having a low coefficient of linear expansion such as a polyimide film, an FRP film, etc. can be appropriately selected and used. In particular, in the case of a metal film, an EMI shielding effect can be expected for the electronic circuit structure produced. Further, the adhesive layer 17 and the adhesive layer provided outside the protective layer may be the same or different.

In the above embodiment, a pressure-receiving layer was provided to protect the transfer circuit unit and components from injection pressure, but this pressure-receiving layer may also be provided on the inner surface of the mold integrally with the mold. In that case, the surface of the pressure-receiving layer will have an uneven shape that matches the shape of the component.

In addition, the pressure-receiving layer is made of different materials: one that fills around the component and one that is interposed between the belly of the component and the transfer circuit unit.The former is made of elastic silicone rubber, and the latter is made of hard epoxy. Soldering of parts is more effective when using resin or the like to protect the parts.

Furthermore, in the above embodiment, the case where the transfer circuit unit is a layered circuit is shown, but this may be a multilayer circuit. Also, the transfer circuit unit is not only printed with conductive paste and insulating paste, but also is made of FPC (flexible). (printed circuit).

〔Effect of the invention〕

As explained above, according to the present invention, the components are mounted at the stage of making the transfer sheet before injection molding, that is, while the transfer circuit unit is in a flat state, so the components can be easily mounted. , it has the advantage of being easily adaptable to three-dimensional shapes. In addition, since the parts are mounted before injection molding, the resin for injection molding does not need to be resistant to soldering heat, and inexpensive resins with low heat resistance can be used, which has a significant cost reduction effect. .

[Brief explanation of drawings]

1 to 4 are cross-sectional views showing a method of manufacturing an electronic circuit structure according to an embodiment of the present invention in order of steps. 11 - Transfer circuit unit, 19 - Components, 24 - Transfer sheet, 25 and 26 - Mold, 28 - Injection molded body, 29 - Electronic circuit structure.

Claims (1)

[Claims] An electronic circuit characterized in that a transfer sheet with components mounted on a transfer circuit unit is created, the transfer sheet is set in a mold and injection molding is performed, and the transfer circuit unit is transferred together with the parts to an injection molded body. Method of manufacturing the structure.