JPH01124290A - Manufacture of composite board - Google Patents

Abstract

PURPOSE:To prevent a plated part on a cover-lay film from being stripped off and to prevent it from adhering to other parts by a method wherein an adhesive agent is coated on the cover-lay film. CONSTITUTION:A double-sided PWP (hard board) 17 contains an outside copper foil part 1 and an inside copper foil part 3 where an unnecessary part has been removed; an unnecessary part at an inside copper foil part 7 of a double- sided FPC 18 is removed; after that, a cover-lay polyimide film 5 is pasted on it by using an adhesive agent 6 for cover-lay use; an adhesive sheet 15 is placed on it and is pressed. An adhesive sheet 4 which has been hollowed out so as to suit a shape of said double-sided PWB 17 is sandwiched between the double-sided PWB 17 and the double-sided FPC 18 and is pressed. Then, a through hole used to connect said PWB 17 to the FPC 18 is made; the through hole is plated and both boards are connected. During this process, because an adhesive agent layer exists on the cover-lay film 5 of the FPC 18, copper is plated uniformly; this assembly is not dropped into a plating bath; a plated part does not adhere to other parts of the substrate.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to printed wiring boards, and particularly to flexible printed wiring boards (hereinafter referred to as FPCs) and rigid printed wiring boards (hereinafter referred to as PWBs) using through-hole plating. The present invention relates to a method for manufacturing a connected composite substrate.

(Summary of the Invention) In a composite board in which an FPC and a PWB are connected by through-hole plating, during through-hole plating, the plating attached to the coverlay film on the surface of the single FPC may fall into the plating bath, or other parts of the board may be It adheres to the parts of the body, making it impossible to achieve uniform plating. To this end, the present invention prevents the plating on the coverlay film from peeling off and eliminates adhesion to other parts by applying an adhesive onto the coverlay film.

(Prior technology) When through-hole plating is performed on a composite board of PWB and FP, the plating is difficult to adhere to the polyimide film for the FPC coverlay, which is the bottom of the hollowed out part of the PWB, so the through-holes are When plating was performed, the copper plating on the polyimide film for the film coverlay would peel off and fall into the plating bath, or other parts of the board could not be plated evenly.To solve this problem, conventional methods were used. are shown in Figure 2 (a), (b
), dry film photoresist 10 is applied to the hollowed out part 16 of PWB 17 before through-hole plating.
By forming this, the surface of the polyimide film 5 for coverlay of the FPC 18 exposed at the lower part of the hollowed out part 16 of the PWB 17 is hidden, and when through-hole plating is performed, the surface of the polyimide film 5 for coverlay of the FPC 18 is covered. I was careful not to get any sticks on it.

Alternatively, if the thickness of the PWB 17 making up the composite board is large or the cutout area of the PWB 17 is large, a groove 13 is cut in the PWB 17 as shown in FIG. 3(a). Dry film photoresist 1 is placed on the surface of PWB 17 to cover it as shown in Figure 3(b).
0 was formed to prevent plating from adhering to the surface of the polyimide film 5 for coverlay of the FPC 18 as described above. In the method, PWB17 and FPC
In order to form the dry film photoresist (10) on the photoresist 18, a lamination-exposure-development-peeling process and an artwork film to be used for exposure were required. Also, P
On the surface of the WB 17, there was a problem in that a pattern could not be formed on the portion covered by the dry film 10.

After partially peeling off the dry film, groove 13 of pWB17 and PW
There was also the problem that cleaning and drying the gap between B17 and FPC18 was difficult and required special equipment.

An object of the present invention is to provide a composite substrate that eliminates the above-described conventional drawbacks.

(Means for solving the problem) In the composite substrate of the present invention in which flFPc and PWB are connected by through-hole plating, an adhesive layer is formed on the polyimide film for coverlay on the FPC surface to improve the adhesion of plating. It is characterized by

(Function) According to the present invention, by forming the adhesive layer on the polyimide film for coverlay on the surface of the FPC as described above, uniform plating can be performed on the adhesive layer.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a four-layer composite board constructed by pressing a double-sided PWB and a double-sided FPC according to an embodiment of the present invention.

The double-sided PWB 17 shown in FIG. 1(a) has an inner-layer copper foil 3 with unnecessary parts removed by pattern etching with the outer-layer copper foil, and the double-sided FPC 18 shown in FIG. 1(c) has the following: After removing unnecessary portions of the inner layer side copper foil 7 by pattern etching, a polyimide film 5 for coverlay is pasted thereon using adhesive 6 for coverlay, and further adhered onto the polyimide film 5 for coverlay. The sheet 15 is placed and pressed.

An adhesive sheet 4 cut out according to the shape of the double-sided PWB 17 is pressed between the double-sided PWB 17 and the double-sided FPC 18 to form a four-layer composite board, and a polyimide film 5 for coverlay on the surface of the FPC 18 is formed. The upper part is covered with an adhesive layer by an adhesive sheet 15.

Next, a through hole 11 is drilled to connect the PWB 17 and the FPC 18, and through hole plating is applied to connect both boards. At this time, since there is an adhesive layer on the coverlay film 15 of the FPC 18, the copper plating adheres uniformly and does not fall into the plating bath or adhere to other parts of the substrate. This makes the conventional second
It becomes unnecessary to use the method shown in FIGS. 3 and 3, and the process can be simplified.

Incidentally, the coverlay of the FPC 18 is made of a polyimide film 5 with adhesive 6 applied to one side, but the adhesive sheet 15 is prepared by applying adhesive to both sides in advance. Polyimide film for coverlay 5, adhesive for coverlay 6
By using an integrated adhesive, there is no need to use adhesive tape 15.

Next, the plating on the adhesive layer is removed at the same time as the outer copper foil of the composite substrate is pattern etched.

After that, P
By cutting out a part of WB17, PWB17 is divided into multiple parts, and the divided PWB17 is divided into FP.
It becomes a composite board connected to C18.

(Effects of the Invention) As described above, according to the present invention, FP
It is possible to provide a method for manufacturing a useful composite substrate in which an adhesive layer can be formed on a polyimide film for coverlay on the C surface.

[Brief explanation of the drawing]

FIGS. 1(a) to (d) are cross-sectional views showing one embodiment of the present invention, FIGS. 2(a) and (b) are top views and cross-sectional views showing a conventional example, and FIGS. 3(a), (b) is a top view and a sectional view showing another conventional example. 5...Polyimide film for coverlay, 16...
Hollowed out part, 17...Hard board ('PWB), 18
...Flexible printed circuit board (FPC). Agent Patent attorney Takeshi Sugiyama (1 other person) (a) Illustration

Claims (1)

[Claims] 1. The flexible substrate is overlaid on a hard substrate having a hollowed portion using an adhesive applied to the coverlay film of the flexible substrate, and after connecting both substrates by through-hole plating, the adhesive in the hollowed portion and plating are applied. A method for manufacturing a composite substrate, characterized in that the hard substrate is divided by removing a part of the hard substrate outside the hollowed portion, and the hard substrate is divided by the flexible substrate.