JPH0216792A - Manufacture of composite substrate - Google Patents

Abstract

PURPOSE:To bond a printed board and a hard board and to eliminate burr, and fold by providing a necessary hole for soldering before laminating adhesive sheets to a printed board and by forming other holes through another process to bond the printed board and a hard board. CONSTITUTION:A cover leg is heat-pressed and fixed temporarily at the edge alone, and then applied to a copper foil 1 through baking process. It is laminated in 4 to 5 layers and a hole 8 is shaped at a position of solder joint. Then 4 to 5 adhesive sheets 6 are laminated and a hole 9 is shaped at a position which requires solder joint later. Several printed boards with sheet 6 are laminated and held between hard boards 11, 11', and then fixed. A fixing hole 12 is shaped with a drill 10. A mold releasing paper 5' under the sheet 6 is removed and the printed board and the hard board 11, 11' are bonded and fixed so that the solder joint hole 8 agrees with an exposed section 3 of the copper foil 11. According to this constitution, production of burr, and fold can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a composite board that integrates a flexible printed board and a rigid board.

<Prior Art> A conventional method for manufacturing a composite substrate will be described with reference to FIGS. 13 to 25.

First, flexible printed circuit board (hereinafter referred to as FPC)
Explain.

An FPC (FPC) in which a polyimide film with a thickness of about 50 μm and a copper foil 1 are bonded together using an epoxy adhesive (not shown).
(Fig. 13), a pattern is formed by an etching method (Fig. 14), and a coverlay (also known as haohlay) 7 is pasted on the necessary parts of the copper foil 1 to prevent solder wetting (Fig. 15). figure). Next, prepare an epoxy adhesive sheet 6 with release paper 5, 5 on both sides (Fig. 16).
Four or five adhesive sheets 6 are stacked one on top of the other, and the adhesive sheets 6 are pasted on the underside of the relief holes 9 (FIG. 18).

In this way, as shown in FIG. 18, an FPC consisting of the cover layer, copper foil 1, polyimide film 2, adhesive sheet 6, and release paper 5 is produced.

Next, the FPCs are stacked and holes are drilled by drilling 10.10 (FIG. 19). For drilling holes, use bakelite plates (hereinafter referred to as bake plates) on the top and bottom of the stacked FPCs11. Sandwich the FPC with +1, and in order to prevent misalignment between the FPCs, make holes in advance in the ends of the FPC (parts that are unnecessary as a wiring board) and the bake boards +1 and I1', and insert reference pins (not shown). ) before drilling.

There are two uses for drilling holes: one is for normal mounting holes such as screws, and the other is for molten solder to pass through when soldering to the PWB, and then the cooled and hardened solder connects the PWB. This is to enable solder joints. There is no need to provide an adhesive escape, which will be described later, in the normal mounting holes for screws and the like. There is no possibility that the mounting hole will become a passage for molten solder, and it is necessary to provide an "escape" for the adhesive in the hole for soldering. It should be noted here that the drilling process is performed by continuously changing the type of drill during the process to drill ordinary mounting holes and holes for solder bonding once.

Next, a portion of the hard substrate (hereinafter referred to as PWB) will be explained.

The material used for the PWB is paper phenol, paper epoxy, composite material, glass epoxy, etc. 4 with copper foil 3 pasted on one side (Fig. 20), and the thickness of the copper foil is 18 μm.
35 μm is normal, and the plate thickness is 0.8 to 1.6 depending on the application.
are used.

The copper foil 3 is left only in the part to be soldered to the FPC, and the remaining part of the copper foil is removed by etching (FIG. 21). The shape of the portion where the copper foil 3 is left is a circle with a slightly larger hole diameter of the FPC.

Next, the FPC and PWB are soldered together by peeling off the release paper 5 from the bottom of the FPC after drilling 8 (
22, 23), the FPC is glued and fixed on the top of the PWB (Fig. 24), and the FPC is fixed by hand soldering and solder reflow.
The PC and PWB are electrically bonded (FIG. 25).

<Problem that the invention seeks to solve> However, the need for the adhesive to "break" is due to the following reason.

When joining the FPC and PWB with solder, if the adhesive sheet 6 is on the vertical plane that connects the copper foil I of the FPC and the polyimide film 2, then the joining part is on the same vertical line as the copper foil I of the FPC. High heat during solder melting (240℃~350℃)
℃), the adhesive sheet 6 melts due to this heat, and P
Wet the WBO copper foil 3 to inhibit solder wettability and bond the FPC and P.
This reduces the reliability of the connection with the WB.

%, when PWB copper foil is used for the purpose of grounding (earthing) on a composite board and used as a shield wiring board, there is a risk that the shielding effect will be weakened.

The above-mentioned "escaping" of the adhesive prevents such a thing, and usually the drilling hole 8 for molten solder is spaced 1 to 2 rrm inward from the hole 9 of the adhesive sheet 6, based on experience. It's dawn.

However, in the conventional manufacturing method, there are the following problems when drilling holes, which is the last step of FPC creation.

Because the object to be drilled has a gap called ``escape'', it is difficult to secure it completely when drilling.
As shown in FIGS. 22 to 25, burrs, burrs, wrinkles 14, etc. are concentrated on the hole edges of the "relief" portions.

This hardly comes out of the hole in the part where there is no "escape".

It is clear that the cause of cracks, burrs, and wrinkles is the creation of "relief", and this means that as the number of stacked sheets increases when drilling holes in flexible sheet with adhesive sheet, the edge of the hole at the part with the relief increases. Increased incidence of wrinkles, burrs, and wrinkles;
It has also been proven that there are fewer problems with the hole edges in areas where there is no relief.

Therefore, in order to reduce the burrs, burrs, and wrinkles on the hole edges that have "run-off", it is recommended to drill two flexible sheets with adhesive sheets at a time, or to drill several sheets at the same time. In order to remove the holes, burrs, and wrinkles in the holes where there is a "relief", the only option is to polish the green color of the holes with sandpaper, etc.

In either case, the occurrence of burrs, burrs, and wrinkles is a problem because the efficiency of the kongming decreases or the process of removing burrs, burrs, and wrinkles has to be added by one step. Because Paris
This is because burrs and wrinkles impair the reliability of the solder joint between the FPC and the PWB.

In view of the above-mentioned points, the present invention does not reduce the number of holes to be drilled due to the defects caused by the occurrence of burrs, burrs, and wrinkles on the hole edges when drilling holes in FPC, and also removes the green of the holes by sandpaper. This provides a manufacturing method that does not require polishing.

<Means for Solving the Problems> In the present invention, the necessary holes for soldering the FPC and the hard substrate are formed in the FPC before bonding the adhesive sheet, and the holes are re-drilled in a separate process. Go and FPC and P
It is characterized by adhering to the WB.

<Effects> According to the above, by following the steps of drilling holes in the FPC and then creating gaps, and avoiding the step of drilling multiple holes in areas with gaps, it is possible to avoid the occurrence of cracks, burrs, wrinkles, etc. It is difficult to process, and it is possible to stack a large number of sheets, improving work efficiency.

<Example> Hereinafter, an example of the present invention will be described in detail using FIGS. 1 to 12.

First, the materials of the flexible substrate, rigid substrate, and adhesive sheet that constitute the composite substrate will be explained based on FIGS. 2(a) to 2(c).

Figure 2 (a) shows a polyimide film 2 with a thickness of about 50 μm.
This is a material for a flexible board made by adhering a copper foil of approximately 18 μm to one side of the board using an epoxy adhesive. Second
In Figure (b), adhesive (when the substrate is paper phenol, composite, etc.) and prepreg (when the substrate is paper epoxy, glass epoxy, etc.) is applied to one side of a substrate 4 made of paper phenol, paper epoxy, composite glass epoxy, etc. 1
A hard substrate (
It is a material with a plate thickness of 0.8 to L6t). Figure 2 (C) is
This is an adhesive sheet formed by providing release papers 5, 5 (materials are paper on the upper surface and polypropylene on the lower surface, both having a thickness of about 100 μm) on both sides of the adhesive sheet 6.

Next, a method for manufacturing a flexible substrate will be described with reference to FIGS. 3 to 5.

A part of the copper foil 1 provided on one side of the flexible board is removed by etching (Fig. 3), and a coverlay (also called overlay) 7 is placed on the copper foil 1 to improve soldering properties. After heat-pressing and temporarily fixing the parts, they are baked and pasted (Fig. 4). After that, stack 4 to 5 sheets and drill a hole 8 in the part to be soldered (FIG. 5).

Next, the adhesive sheet with release paper will be described based on FIG. This is made by stacking 4 to 5 adhesive sheets shown in FIG. 2(C) and punching holes 9 in the parts that will be soldered in the future. The hole 9 is made to have a diameter 1 to 2rrs larger than the hole 8 of the FPC.

Next, the FPC and adhesive sheet are bonded together as shown in FIGS. 7 to 9. The release paper 5 on the top of the adhesive sheet 6 is peeled off, and an FPC is pasted so that the holes 9 of the adhesive sheet and the holes 8 of the FPC face each other (FIG. 7). Stack several FPCs with adhesive sheets 6 on top of each other, sandwich them between Bakelite plates +1-11', and use a bottle (not shown).
Fix it by. After that, use the drill 10 to install the hole 1.
Open 2 (Figures 8 and 9).

FIG. 10 shows a copper foil 3 provided on one side of a PWB base material 4.
is etched to expose only the soldered parts.

After such preparation, the release paper 5 at the bottom of the adhesive sheet 6 provided at the bottom of the FPC shown in FIG. 9 is peeled off.
), the adhesive sheet 6 at the bottom of the FPC allows the FP to
The FPC and PWB are bonded and fixed so that the solder joint hole 8 of C and the exposed copper foil part 3 of the soldered part of the PWB are aligned (FIG. 12). Finally, as shown in FIG.
FPC via solder 13 by hand soldering or solder reflow
and PWB are electrically connected to form a composite board.

In this way, for example, when used as a shield wiring board, etc., a composite board in which an FPC and a PWB are soldered together can be used without compromising the shielding effect of the joint, making work smoother and easier than with conventional technology. It can be manufactured using a good process.

This is because, in the present invention, by avoiding the process of drilling holes in places with gaps, it is possible to press the object to be drilled with sufficient force compared to the conventional technology.
This is because the edges of the holes are less likely to develop burrs, burrs, and wrinkles. Therefore, the number of stacked sheets can be increased, for example, to 3 to 4 sheets at a time, instead of 1 or 2 sheets at the same time in the prior art, thereby improving work efficiency. In the conventional technology, even when working with one or two stacked sheets, the press is weak due to the nature of drilling holes in gaps, and there is a risk of cracking, peeling, and wrinkles.

<Effects of the Invention> According to the present invention, a useful manufacturing method with high reliability and good work efficiency can be provided for a composite board consisting of a flexible printed board and a hard board.

[Brief explanation of the drawing]

FIG. 1 shows a completed product according to an embodiment of the present invention.
Hard board, 6... Adhesive sheet, 7... Coverlay,
8...Solder joint hole, 12...Mounting hole, 13...
·solder.

Claims (1)

[Claims] 1. In a method for manufacturing a composite board in which an adhesive sheet is interposed between a flexible printed circuit board and a hard substrate, and the two are bonded by the adhesive sheet, the flexible printed circuit board and the rigid substrate are bonded together before bonding the adhesive sheet. 1. A method for manufacturing a composite board, characterized in that holes necessary for soldering are formed in a flexible printed circuit board, and then other holes are formed in a separate process to bond the two together.