JPH0964543A - Production of multilayered flexible printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To interconnect the circuit layers through via holes of a small diameter by producing a multilayer flexible printed wiring board continuously according to a roll-to-roll system. SOLUTION: A photosensitive insulation layer 5 is formed on the circuit face 4 of a flexible printed wiring board on which a circuit 41 is formed. A via hole 6 is then made through the insulation layer by a photo process followed by formation of a circuit 42 on the surface of the insulation layer and the interlayer connection through a via hole. When a multilayered flexible printed wiring board comprising three layers or more is produced, a circuit face 4a including the circuit 42 is formed, as a next circuit face, on the surface of the insulation layer and the process is repeated.

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 multilayer flexible printed wiring board. More specifically, it relates to a method for manufacturing a multilayer flexible printed wiring board that connects different circuit layers by via holes, and to a method for manufacturing a multilayer flexible printed wiring board in which the via holes are formed by a photo process.

[0002]

2. Description of the Related Art Flexible printed wiring boards are manufactured by the steps of copper foil laminating on a base film coated with an adhesive, drying, resist pattern formation, circuit pattern formation by etching, coverlay formation, and terminal and land plating. . The one-sided flexible printed wiring board is manufactured by a so-called roll-to-roll method in which raw materials which are long and wound in a roll shape are continuously processed, wound in a roll shape, and used in the next step.

[0003]

However, when manufacturing a double-sided flexible printed wiring board, there is a step of forming holes for through-hole connection and a step of through-hole plating before forming a resist pattern. Drilling for through hole connection is performed by mechanical drilling because it needs to penetrate the base film. This mechanical drilling needs to be performed by cutting into a predetermined work size, and cannot be continuously processed by the roll-to-roll method. Further, it is difficult to perform small diameter machining with a diameter of 0.2 mm or less by mechanical drilling.

It is an object of the present invention to provide a method for manufacturing a multilayer flexible printed wiring board which enables continuous work by a roll-to-roll method.

[0005]

According to the present invention, a photosensitive insulating layer 5 is formed on a circuit surface 4 of a flexible printed wiring board on which a circuit 41 is formed, and a via hole 6 is formed in this insulating layer by a photo process. The method for producing a multilayer flexible printed wiring board is characterized in that the circuit 42 is formed on the surface of the insulating layer and the interlayer connection is performed by the via hole 6. When manufacturing a multilayer flexible printed wiring board having three or more layers, the circuit surface 4a including the circuit 42 on the insulating layer surface.
The same process is repeated with the next circuit surface.

[0006]

DETAILED DESCRIPTION OF THE INVENTION A description will be given below with reference to the drawings. First, the copper foil 3 is laminated on the base film 1 via the adhesive layer 2 (see FIG. 1A).

Next, an etching resist is formed so as to cover the portion to be the circuit 41, and the circuit 4 is formed by the etching method.
1 is formed (see FIG. 1B).

Next, a photosensitive insulating layer 5 is formed on the entire circuit surface 4 including the circuit 41 (see FIG. 1C). As a method for forming the photosensitive insulating layer 5, there are a roll coating method using a liquid resin, a curtain coating method, and a laminating method using a film-shaped resin. In order to improve the adhesiveness with the insulating layer 5, it is preferable to form fine irregularities on the surface of the circuit 41. Fine irregularities can be formed on the surface of the circuit 41 by oxidizing the surface of the circuit 41 or by oxidizing the surface of the circuit 41 with a reducing agent such as sodium borohydride or dimethylamineborane.

Next, a photomask is formed on the surface of the photosensitive insulating layer 5 so that the light beam does not hit the portion where the via hole 6 is to be formed, exposed, and the unexposed portion is etched with a developing solution. , Via hole 6 is formed (FIG. 1D).
reference).

Next, a circuit 42 is formed on the surface of the photosensitive insulating layer 5.
Are formed and plated on the inner wall of the via hole 6 to electrically connect the interlayer circuit (see FIG. 1E). As a method of forming the circuit 42 on the surface of the photosensitive insulating layer 5, electroless plated copper is deposited on the entire surface of the photosensitive insulating layer 5, and if necessary, the circuit conductor is made to have a predetermined thickness by electrolytic plating. Either a method of removing a portion that does not become a circuit by etching or a method of forming a plating resist on a portion of the surface of the photosensitive insulating layer 5 that does not become a circuit and performing electroless plating at a necessary portion may be used. Prior to electroless plating, the surface of the photosensitive insulating layer 5 is roughened by treating it with an oxidizing roughening solution. In addition, whether by electroless plating on the entire surface or electroless plating at a required place, it is necessary to contain a plating catalyst in the photosensitive insulating layer 5 or to attach the plating catalyst after roughening. is there.

In the case of a two-layer flexible printed wiring board, a cover lay for protecting the circuit surface is formed thereafter except the terminals and lands, and the terminals and lands are solder-plated, nickel-plated or gold-plated. Give.

The circuit 4 formed on the surface of the photosensitive insulating layer 5.
By repeating the process with the circuit surface including 2 as the next circuit surface 4, a flexible printed wiring board having three or more layers can be manufactured.

[0013]

【Example】

Example 1 An electrolytic copper foil having a thickness of 18 μm was superposed on the adhesive layer surface of a polyimide film having a thickness of 25 μm provided with an adhesive layer having a thickness of 35 μm, and heated and pressed at a temperature of 170 ° C. and a pressure of 3 MPa for 30 minutes. . Next, the copper foil surface was etched to form a circuit. Next, phthalic acid-modified novolac type epoxy acrylate (Nippon Kayaku Co., Ltd., trade name R-525
9 parts) 70 parts (parts by weight, the same applies hereinafter), acrylonitrile butadiene rubber (manufactured by Japan Synthetic Rubber Co., Ltd., product name PNR-1H is used) 20 parts, alkylphenol resin (manufactured by Hitachi Chemical Co., Ltd., product name Hitanol 2400)
3 parts, a photopolymerization initiator (made by Ciba Geigy, trade name Irgacure 651) 7 parts, aluminum hydroxide (manufactured by Showa Denko KK, trade name Heidilite H-42)
10 parts by weight of the composition is applied to the circuit surface by roll coating and dried at 80 ° C. for 10 minutes to give a thickness of 50.
A μm insulating layer was formed. Then, through a photomask with a shielding part at the via hole, 400 mJ
/ Cm ² of ultraviolet ray was irradiated, and a 1% sodium carbonate aqueous solution was developed at 30 ° C. for 2 minutes to form a via hole, and for post-exposure, ² J / cm ² of ultraviolet ray was irradiated. next,
Roughening solution heated to 50 ° C. (KMnO ₄ : 60 g / l, N
aOH: 40 g / l aqueous solution) for 3 minutes, SnCl
_The surface of the insulating layer was roughened by immersing it in an aqueous solution of 2:30 g / l and HCl: 300 ml / l for 3 minutes for neutralization. Then P
Immerse in an electroless plating catalyst solution containing dCl ₂ (using Hitachi Chemical Co., Ltd., trade name HS-202B) for 10 minutes at room temperature, wash with water, electroless plating solution (manufactured by Hitachi Chemical Co., Ltd., trade name CUST201) (Use) at room temperature for 25 minutes, rinse with water, and then electrolytically plate copper sulfate to a thickness of 2
A 0 μm conductor layer was formed and annealed at 150 ° C. for 30 minutes. Next, a circuit was formed by processing etching resist formation, etching, and etching resist removal in the order to leave the circuit.

Example 2 An electrolytic copper foil having a thickness of 18 μm was superposed on the adhesive layer surface of a polyimide film having a thickness of 25 μm provided with an adhesive layer having a thickness of 35 μm, and heated at a temperature of 170 ° C. and a pressure of 3 MPa for 30 minutes. Pressurized. Next, the copper foil surface was etched to form a circuit. Next, phthalic acid-modified novolac type epoxy acrylate (Nippon Kayaku Co., Ltd., trade name R-525
9 parts) 70 parts (parts by weight, the same applies hereinafter), acrylonitrile butadiene rubber (manufactured by Japan Synthetic Rubber Co., Ltd., product name PNR-1H is used) 20 parts, alkylphenol resin (manufactured by Hitachi Chemical Co., Ltd., product name Hitanol 2400)
3 parts, a photopolymerization initiator (made by Ciba Geigy, trade name Irgacure 651) 7 parts, aluminum hydroxide (manufactured by Showa Denko KK, trade name Heidilite H-42)
10 parts, catalyst for electroless plating (palladium addition filler, manufactured by Hitachi Chemical Co., Ltd., trade name Cat # 1)
4) is applied to the circuit surface by roll coating and dried at 80 ° C. for 10 minutes to give a thickness of 50 μm.
m insulating layer was formed. Next, pass through a photomask with a shielding part at the via hole to 400 mJ /
Irradiate with cm ² of ultraviolet rays and 3 with 1% sodium carbonate solution
It was developed at 0 ° C. for 2 minutes to form a via hole, and for post-exposure, it was irradiated with ² J / cm ² of ultraviolet rays. Next, 5
The roughening solution heated to 0 ° C. (KMnO ₄ : 60 g / l, Na
OH: 40g / l aqueous solution) for 3 minutes, SnCl
_The surface of the insulating layer was roughened by immersing it in an aqueous solution of 2:30 g / l and HCl: 300 ml / l for 3 minutes for neutralization. Next, an electroless plating solution (made by Hitachi Chemical Co., Ltd., trade name CUS
(T201 is used) at room temperature for 25 minutes, washed with water, and then electrolytically plated with copper sulfate to form a conductor layer having a thickness of 20 μm, and annealed at 150 ° C. for 30 minutes. Next, a circuit was formed by processing etching resist formation, etching, and etching resist removal in the order to leave the circuit.

All the above steps were carried out by a roll-to-roll system. The diameter of the via hole is 0.1m.
Even with m, the circuit layers could be electrically connected to each other. Furthermore, the conductor thickness of the circuit layer can be set to 20 μm, and a circuit of line / space = 0.08 mm / 0.08 mm can be formed accurately.

[0016]

According to the present invention, a photosensitive insulating layer is formed on the circuit surface of a flexible printed wiring board on which a circuit is formed, and a via hole is formed in this insulating layer by a photo process to form a circuit on the surface of the insulating layer. By forming and connecting the layers by via holes, the roll-to-roll method can be continuously performed, and the circuit layers can be electrically connected to each other by the small diameter via holes.

[Brief description of drawings]

FIG. 1 relates to an embodiment of the present invention, (a), (b),
It is the schematic which shows the change by a manufacturing process in order of (c), (d), and (e).

[Explanation of symbols]

 1: Base film 2: Adhesive layer 3: Copper foil 4, 4a: Circuit surface 41, 42: Circuit 5: Insulating layer 6: Via hole

Claims (1)

[Claims] 1. A flexible printed wiring board on which a circuit is formed, a photosensitive insulating layer is formed on a circuit surface, a via hole is formed in the insulating layer by a photo process, and a circuit is formed on the surface of the insulating layer and an interlayer is formed by the via hole. A method for manufacturing a multilayer flexible printed wiring board, which comprises connecting.