JPH08316630A - Manufacture of double-sided flexible printed wiring board - Google Patents

Abstract

PURPOSE: To provide a method for manufacturing a double-sided flexible printed wiring board which is flexible and can be manufactured with improved yield. CONSTITUTION: In a double-sided flexible printed wiring board which has two conductor layers 2 which selectively continue by through hole plating and where an area between the conductor layers 2 is formed only by a base insulation layer 1 made of polyimide resin film, one-side conductor layers 2 are eliminated by etching after a circuit constitution process for a refraction part performing repetitive move, thus manufacturing a double-sided flexible printed wiring board with the conductor layers 2 as one layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a double-sided flexible printed wiring board used as a wiring material in electronic equipment that requires high-density mounting.

[0002]

2. Description of the Related Art In general, a conventional double-sided flexible printed wiring board has a thickness because an insulating base layer and conductor layers arranged on both sides of the base insulating layer are adhered using an adhesive. There was a problem in thickness and flexibility. Therefore, in order to improve flexibility in the conventional product, it is necessary to make the conductor layer base insulating layer and the adhesive layer as thin as possible, but in reality, the yield in the bonding step is poor and it has not been put to practical use.

Further, in the bent portion, a structure in which the conductor layer and the adhesive layer on one side are previously removed is used. FIG. 2 is a cross-sectional view of a double-sided flexible printed wiring board having such a structure. In the drawing, reference numeral 11 is a base insulating layer such as a polyimide film, and a conductor layer 13 is bonded and integrated on both surfaces thereof with an adhesive layer 12 such as an epoxy thermosetting adhesive agent interposed. The adhesive layer 12 and the conductor layer 13 have a bent portion A.
In advance, these layers have been removed. Reference numeral 14 is a through-hole plating layer that electrically connects the conductor layers 13 formed on both surfaces. An insulating coating layer 16 made of polyimide film or the like is formed on the outer side of the conductor layer 13 via the adhesive layer 15 similar to the above.

However, in the structure in which the adhesive layer 12 and the conductor layer 13 are previously removed in the bent portion A as described above,
There is a problem in that the yield in the circuit forming process is poor because there is a difference in thickness between this portion and other portions.

[0005]

The present invention solves the above-mentioned problems and provides a method for manufacturing a double-sided flexible printed wiring board which is excellent in flexibility and can be manufactured with a high yield. In a double-sided flexible printed wiring board having two conductor layers that are selectively conducted by hole plating, and between the conductor layers are formed only by a base insulating layer of a polyimide resin film,
Regarding the bent portion that is repeatedly movable, the conductor layer on one side is removed by etching after the circuit configuration process, and the conductor layer is reduced to 1
It is in layers. .

[0006]

1 is a sectional view of a specific example of a double-sided flexible printed wiring board manufactured according to the present invention. In the drawing, reference numeral 1 is a base insulating layer of a polyimide resin film, and conductor layers 2 are arranged on both surfaces thereof.
The conductor layer 2 on one side is not removed in advance at the bent portion A, but is formed by a normal manufacturing process and then removed by etching, and the insulating base layer 1 is exposed at this portion. Reference numeral 3 is a through-hole plating layer for electrically connecting the upper and lower conductor layers 2, and an insulating coating layer 5 made of a polyimide resin film or the like is formed on the outer side of the conductor layer 2 via an adhesive layer 4 such as an epoxy thermosetting adhesive. Is the same as the conventional one.

In the above-mentioned double-sided flexible printed wiring board of the present invention, since there is no adhesive layer between the insulating base layer and the conductor layer, the overall thickness is thinner and the flexibility is improved as compared with the conventional product. . Also, unlike the conventional product, the conductor layer and the adhesive layer at the bent portion are not removed in advance, but
Since the conductor layer is formed by a normal manufacturing process, the conductor layer at the bent portion is removed by etching, and the insulating base layer is exposed, there is no difference in thickness in the circuit forming process and the yield is not deteriorated.

[0008]

EXAMPLE In FIG. 1, a polyimide film 25 μm of an insulating base layer 1, a rolled copper foil 35 μm of a conductor layer 2, a copper plating 15 μm of a through-hole plating layer 3, an epoxy thermosetting adhesive layer 4 of 30 μm, an insulating coating A double-sided flexible printed wiring board according to the method of the present invention having a layer 5 polyimide film of 25 .mu.m was prepared. On the other hand, referring to FIG. 2, the insulating polyimide layer 25 μm for the base insulating layer 11, the epoxy thermosetting adhesive layer 12 for 20 μm, the rolled copper foil 35 μm for the conductor layer 13, the copper plating 15 μm for the through-hole plating layer 14, the epoxy thermosetting A conventional double-sided flexible printed wiring board having a mold adhesive layer 15 of 30 μm and an insulating coating layer 16 of polyimide film 25 μm was prepared. Then, for both, the thickness and flexibility of the bent portion were compared.

The thickness of the present invention is as thin as 105 μm, compared to 125 μm of the conventional product. Regarding the flexibility, the Gurley-type flexibility measurement method shows that the conventional product is 465 mgf, while the product of the present invention is
An improvement effect of 348 mgf and 25% was obtained.

[0010]

As described above, according to the method for manufacturing a double-sided flexible printed wiring board of the present invention, a double-sided flexible printed wiring board having excellent flexibility can be realized with a high yield in a normal manufacturing process. Therefore, it is extremely effective when used for a wiring material such as a hard disk drive or an optical disk drive, which requires high-density wiring and high bending performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a specific example of a double-sided flexible printed wiring board manufactured according to the present invention.

FIG. 2 is a cross-sectional view of an example of a conventional double-sided flexible printed wiring board.

[Explanation of symbols]

 1 Base Insulation Layer 2 Conductor Layer 3 Through Hole Plating Layer 4 Adhesive Layer 5 Insulation Coating Layer

Claims (1)

[Claims] 1. A double-sided flexible printed wiring board having two conductor layers selectively conducted by through-hole plating, wherein a space between these conductor layers is formed only by a base insulating layer of a polyimide resin film. A method for manufacturing a double-sided flexible printed wiring board, characterized in that a conductor layer on one side is removed by etching after the circuit forming step in the movable bent portion so that the conductor layer becomes one layer.