JPH03167715A - Double-sided flexible printed circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a flexible printed circuit board (FPC) having excellent bending resistance by forming a part corresponding to an adhesive agent layer of the position to be a bending part with a non-adhesion part. CONSTITUTION:A part corresponding to an adhesive agent layer 3 of the position to be a bending part is formed with a non-adhesion part 4. A width of the non-adhesion part of the position to be a bending part can be decided at random. Consequently, even if the bending work is repeated to a FPC, each base film basic material 2 can be bent freely because that there is no adhesion part in the intermediate part, and since a play is allowed, degradation and breakdown of the whole of the laminated layer of FPC can be prevented. FPC having excellent bending resistance can be thereby obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a flexible printed wiring circuit (hereinafter referred to as FPC) used as a circuit component of electronic equipment, etc., in which circuit layers are formed on both sides using a two-layer base material. The present invention relates to a formed flexible circuit board and a method of manufacturing the same.

[Conventional technology FPCs were initially used as a substitute for electric wires, cables, etc., and gradually came to replace entire harnesses, and even functioned as high-density wiring boards on which electronic components were mounted. In other words, it functions as a component that has the functions of a printed wiring board, electric wire cable, and connector. Its most important feature is that it is flexible because it uses a film substrate, and by taking advantage of this feature, it can be mounted three-dimensionally and at high density in a sandwiched space.

By the way, conventional FPCs were manufactured in the following manner.

(a) Conventional double-sided flexible circuit boards are made of a double-sided copper-clad base material made by laminating copper foil on both sides of a base film using an adhesive. In this method, since there is an adhesive layer between the copper foil and the base film, the heat resistance of the circuit board is limited by the characteristics of the adhesive. Also, is it possible that a two-layer base material without an adhesive layer between the base film and copper foil has excellent heat resistance?Due to manufacturing process constraints, only one-sided copper foil base material is manufactured, and double-sided copper foil base material There was no.

(b) The two-layer base material is a base material for FPC manufactured by directly coating the surface of copper foil with a resin such as polyimide.

Since the two-layer base material does not have an adhesive layer between the base film and the copper foil, it has higher heat resistance than the conventional three-layer base material that uses an adhesive. However, due to constraints on manufacturing conditions, two-layer base materials are made by bonding base films together using adhesive to form a double-sided copper-clad base material, which is then subjected to drilling, through-hole plating, photo-etching, and coverlay lamination processes. Sequentially, double-sided through-hole FPC
They were manufacturing circuit boards.

[Problems to be Solved by the Invention] However, in the double-sided FPC of the prior art, the entire surface of the base film was bonded using a sheet-like adhesive. When the above-mentioned FPC is used, there is a problem that the bent portion deteriorates and accidents such as wire breakage are likely to occur.

In order to solve the problems of the prior art described above, the present invention aims to provide an FPC with excellent bending resistance by making the part corresponding to the adhesive layer at the position of the bent part a non-adhesive part. .

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following features.

(1) In a double-sided flexible printed wiring circuit board in which a conductive layer is laminated on one side of a base film and the base film sides are bonded together with an adhesive layer, A temporary double-sided flexible printed circuit, characterized in that a portion corresponding to the adhesive layer is a non-adhesive portion.

! 2) In a method for manufacturing a double-sided flexible printed wiring circuit board in which a conductive layer is laminated on one side of a base film and the base film sides are bonded together with an adhesive layer, first, a conductive layer is formed to form a bent part of the double-sided flexible printed wiring circuit board. Remove the adhesive layer or leave it in a non-adhesive state, apply an adhesive layer to other parts, and laminate the base film side with the adhesive layer. Next, perform the drilling process, through-hole plating process, photo-etching process, and coverlay lamination process. A method for manufacturing a double-sided flexible printed circuit board, characterized by sequentially applying the following steps. In the present invention, the width of the non-adhesive portion at the position where the bent portion is to be formed may be arbitrary, but it is preferably provided with a width of 3 mm or more, particularly 5 mm or more. Note that the width of the non-bonded portion herein refers to a portion corresponding to, for example, X in FIG. 3.

In the present invention, any base film can be used such as polyimide film, polyester film polyphenylene sulfide, polyether ether ketone, polyester imide, diallyl phthalate, and the like. The conductive layer may be made of any conductive material such as copper.

The lamination method can be arbitrary, such as directly depositing copper on the base film or laminating it by plating, or laminating the base film directly on the copper foil (casting method, pressure bonding method, polyimide adhesive method, etc.). The following lamination method can be adopted.

In the present invention, the non-adhesive part at the position that will become the bent part may be provided without an adhesive layer (for example, removed by punching), or may be left in a non-adhesive state even if there is an adhesive layer. Other methods may also be used.

[Function] According to the present invention having the above-mentioned structure, since the portion corresponding to the adhesive layer at the position of the bending portion is made into a non-bonding portion, an FPC having excellent bending resistance can be obtained. The reason for this is that even if the FPC is subjected to repeated bending action, since there is no adhesive part in the middle, each base film substrate can be bent freely and play is allowed, so the entire FPC stack will not deteriorate or break. This is because it can prevent this from happening.

[Example code] The present invention will be specifically described below using Examples.

Note that the present invention is not limited to the following examples.

FIG. 1 shows the FPC and manufacturing method of the present invention. In FIGS. 1(a) to (g), 1 is a copper foil, 2 is a base film, 3 is an adhesive, 4 is a non-adhesive part, 5 is a separator, 6 is a hole, 7 is a plating, 8 is an etched part, 9 is a cover lay. Note that FIG. 3 is a schematic perspective view of FIG. 1.

The FPC of the present invention has a conductive layer (on one side of the base film 2), as shown in FIG.
Copper foil) 1 is laminated, and the base film 2 side is coated with adhesive 3.
In a double-sided flexible printed wiring circuit board laminated in layers, a portion corresponding to the adhesive layer at a position that becomes a bent portion of the double-sided flexible printed wiring circuit board is defined as a non-adhesive part 4.

As a result, even if the FPC is subjected to repeated bending action, since there is no adhesive part in the middle, each base film substrate can be bent freely and play is allowed, so the entire FPC stack will not deteriorate or break. can be prevented.

For example, sample size for FPC: 10mm x
1 5 0 rTl m N base film: 12.5
μm, Coverlay film: 25μm 1 Coverlay adhesive = 35μm 1 Conductor thickness = 35μm, Conductor width: 150μm
m1 Conductor spacing: 150 μm 1 The width of the non-bonded part was 10 mm. The bending test was conducted using an MIT bending tester as a bending tester, with the test conditions being 135° one-sided bending and a 500 g load.

As a result, the results shown in Table 1 below were obtained.

As described above, it was confirmed that the FPC of the present invention has extremely excellent bending resistance. Note that in Table 1, the bonded portions are the same as those in the prior art where the entire surface is bonded.

Next, the manufacturing method of the present invention will be explained using FIGS. 1(a) to 1(g).

First, in FIG. 1(a), the adhesive layer at the position that will be the bent part of the FPC is removed or left in a non-adhesive state, and three layers of adhesive are provided on the other parts, and the base film 2 side is covered with three layers of adhesive. The laminate film 5 is removed and another base film 2 side is laminated with three layers of adhesive [FIG. 1(C)]. Therefore, the copper foil 1 should be the outermost layer. However, it is possible to provide a protective film on the outside of the copper foil 1.

Next, a hole 6 is made in a drilling process [FIG. 1(d)]. Next, a plating layer 7 is formed by a through-hole plating process.
Figure (e)]. Next, an etched portion 8 is formed in a photo-etching process [FIG. 1(f)]. Finally, a coverlay film is sequentially applied in the coverlay lamination process [first
Figure (g)].

FIG. 2 shows a continuous process of some of the steps of the method of the present invention, in which two two-layer base materials are prepared using the punched sheet-like adhesive t1 corresponding to the lower part of FIG. 1(a). 13. Shows the process of pasting 13 together.

That is, using the sheet adhesive 11, the base film surfaces of the two-layer base material 13.
4. After laminating in step 14, the double-sided copper-clad base material t5 is wound up on the winding opening roll 16. This results in Figure l (a
) to CC) can be performed in succession.

Utilizing the bending characteristics of the present invention, the film can be used for applications such as an FPC for electrical connection between the main body and display section of a laptop computer.

[Effects of the Invention] As explained above, according to the present invention, since the portion corresponding to the adhesive layer at the position of the bent portion is made into a non-adhesive portion, an FPC with excellent bending durability can be obtained. . The reason for this is that even if the FPC is subjected to repeated bending [1t] action, since there is no adhesive part in the middle, each base film substrate can be bent freely and play is allowed, so the entire FPC stack will not deteriorate. This is because it can prevent damage or damage. The bending resistance was 100 times more excellent in the bending test.

Further, the manufacturing method of the present invention provides the above-mentioned FPC with excellent bending resistance.
We were able to achieve the remarkable effect of being able to manufacture efficiently and inexpensively.

[Brief explanation of the drawing]

The upper figure (g) shows a double-sided flexible printed circuit board according to an embodiment of the present invention, FIGS. 1 (a) to (g) show the manufacturing process of the present invention, and FIG. a)～(
Fig. 3 shows the continuous process of the method of the present invention shown in c).
2 shows a schematic perspective view of FIG. 1; FIG. King: Copper foil 2: Base film 3: Adhesive 4: Non-adhesive area 5: Separator 6: Hole 7: Plating 8: Etching area 9 11 12 ↓ 3 14 15 16 Coverlay punched sea separator winding 2-layer base material roll double-sided copper clad base material winding roll adhesive

Claims (2)

[Claims] (1) In a double-sided flexible printed wiring circuit board in which a conductive layer is laminated on one side of a base film and the base film sides are bonded together with an adhesive layer, the A double-sided flexible printed circuit board characterized in that the portion corresponding to the adhesive layer is a non-adhesive portion. (2) In a method for manufacturing a double-sided flexible printed wiring circuit board in which a conductive layer is laminated on one side of a base film and the base film sides are bonded together with an adhesive layer, first, the bent portion of the double-sided flexible printed wiring circuit board is Remove or leave the adhesive layer in the non-adhesive state at the desired position, provide an adhesive layer in other parts, and laminate the base film side with the adhesive layer. Next, perform the drilling process, through-hole plating process, photo-etching process, and coverlay lamination. A method for manufacturing a double-sided flexible printed circuit board, characterized by performing the steps sequentially.