JP3208178B2 - Rigid flex printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid-flex printed circuit board in which a flexible printed circuit board and a rigid printed circuit board are continuously integrated, and a method of manufacturing the same.

[0002]

2. Description of the Related Art A bendable flexible printed wiring board is known in which a circuit is formed by attaching a metal conductor such as copper foil to a base film such as a polyimide resin or polyester resin and a cover film such as polyimide or polyester is adhered to the circuit. It is. Also, a rigid printed wiring board in which a prepreg, which is a sheet in which a resin such as glass cloth or paper is impregnated with a resin, is laminated, and a circuit board is formed by heating and pressurizing, is formed. Further, there is also known a rigid flex printed wiring board in which the flexible part and the rigid part are formed continuously by integrating them.

FIG. 2 is a cross-sectional view of a conventional rigid-flex printed circuit board, FIG. 3 is a plan view of the circuit board, and FIG. 4 is a plan view of a cover film layer. FIG. In this wiring board, for example, as shown in FIG. 3, rigid portions 1 and 2 and a flexible portion 3 connecting them are continuously formed and integrated. As shown in FIG. 2, the flexible portion 3 covers a base film 4 for a flexible printed wiring board, a metal conductor 5 such as a copper foil having excellent flexibility attached to both sides of the base film 4, and covers the metal conductor 5. A cover film 6 which is an insulating material is sequentially laminated, and the cover film 6 and the metal conductor 5 are laminated.
And an adhesive layer 7 is interposed between them. The base film 4 is usually made of a heat-resistant resin such as polyimide or polyester. A circuit pattern is formed on the metal conductor 5, and a conductive through hole may be formed through the base film. As the cover film 6, an insulating film made of the same material as that of the base film 4 such as polyimide or polyester is used, and is bonded by an adhesive layer 7 coated with an acrylic adhesive or the like. As a result, the flexible portion 3 has flexibility and can be bent.

The rigid portions 1 and 2 are formed by laminating a rigid printed wiring board 9 with a prepreg 8 interposed between portions having the same structure as the flexible portion 3. That is, as shown in FIG. 4, the sectional structure of the flexible portion 3 extends not only to the flexible portion 3 but also to the rigid portions 1 and 2, and the prepreg 8 and the rigid printed wiring board 9
Are laminated. Here, the prepreg 8 is obtained by impregnating a base material such as glass cloth or paper with a resin such as epoxy or polyimide, and performing a drying treatment to obtain a semi-cured state. Reference numeral 10 in FIG. 2 is a circuit pattern formed on the rigid printed wiring board 9.

In the conventional rigid-flex printed wiring board configured as described above, there is a problem that when forming the through-hole 11, the throwing power of the through-hole plating is not stabilized, and the product yield is deteriorated. That is, the through hole 11 is formed by forming a through hole hole in the rigid portions 1 and 2 by drilling or the like, performing chemical copper plating on the through hole hole, and then performing electrolytic copper plating. In the conventional rigid flex wiring board, the cover film appears directly on the inner wall of the through-hole, and it is considered that chemical copper plating hardly deposits on this surface. An acrylic adhesive or the like is usually used for the cover lay film 6, which is degraded by a chemical desmear treatment such as permanganic acid or a plating solution, and its end is eluted into a through-hole. It is thought that the phenomenon of reversing or receding occurs, which hinders the throwing power of the plating. As described above, the conventional rigid flex printed wiring board has an unstable plating ability on the cover film and its adhesive layer, and the thickness of the through-hole plating becomes uneven, and the circuit connection reliability is reduced. There was a problem that the product yield deteriorated.

As a means for solving such a problem,
Rigid flex consisting of forming a rigid portion by extending the cover film of the flexible portion into the rigid portion and continuing to the prepreg of the rigid portion, and laminating another prepreg and a rigid printed wiring board so as to include the continuous portion. A printed wiring board has been proposed (JP-A-3-24
6986). FIG. 6 is a cross-sectional view of this proposal, and FIG. 5 is a plan view showing a cover film layer. According to this proposal, a cover film is provided on the rigid portions 1 and 2 of the rigid flex printed wiring board shown in FIG. Is substantially not included, and with this structure, the problem of the throwing power of plating in the through-hole portion has been solved. However, when the cover film covers only the flexible portion 3 and does not cover the portions corresponding to the rigid portions 1 and 2, the dimensional change behavior at the time of bonding the cover film becomes non-uniform and the rigid film is integrated with the rigid portion. It is difficult to maintain consistency. In addition, it is necessary to adopt a structure in which the prepreg 12 is continuous at the terminal end of the cover film. However, it is difficult to position the prepreg 12 and the structure is practically impossible. Is expected to occur. Further, it has been proposed to use another prepreg for integrating the rigid portion and the flexible portion, but there is a major problem that the production cost is significantly increased.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in consideration of the above problems, and has made it possible to perform uniform and stable through-hole plating. It is an object of the present invention to provide a rigid-flex printed wiring board with significantly improved cost, improved product yield, improved interlayer compatibility, and significantly reduced cost, and a method for manufacturing the same.

[0008]

According to the present invention, it is an object of the present invention to provide a rigid-flex printed circuit in which a flexible portion in which a flexible printed circuit board is covered with a cover film and a rigid portion formed of a rigid printed circuit board are integrated. In a board, a portion of the cover film of the flexible portion included in the rigid portion, in which a portion of the cover film corresponding to a through-hole processed portion after lamination and an adhesive layer thereof are removed in advance. This is achieved by a printed wiring board.

Further, according to the present invention, an object of the present invention is to provide a rigid-flex printed wiring board in which a flexible portion in which a flexible printed wiring board is covered with a cover film and a rigid portion made of a rigid printed wiring board are integrated. In the manufacturing method, a step of forming a circuit on a flexible copper-clad laminate to process a flexible printed wiring board, a step of removing a portion corresponding to a through-hole processing portion after lamination of a cover film in advance, and a step of removing the removed cover A step of covering the flexible printed wiring board with a film and forming a flexible part, a step of processing a rigid printed wiring board and forming a rigid part, a step of externally processing a prepreg and removing unnecessary parts, and the step of forming the rigid part and the flexible part Includes the step of integrating using a prepreg from which external processing has been performed and unnecessary parts have been removed It is achieved by the method for producing Gide flex printed circuit board.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of one embodiment of the present invention,
FIG. 7 is a plan view showing the cover film layer. In FIG. 1, the cover film 6 and the adhesive layer 7 have been removed by appropriate distances l and m around the through-hole processed portions in the rigid portions 1 and 2 and the periphery thereof. The removed concave portion is filled with the resin of the prepreg 8 by flowing, which is performed simultaneously with the lamination and integration of the flexible portion and the rigid portion. According to this method, when the through-hole is drilled, the cover film 6 and the adhesive layer 7 are not directly exposed on the inner wall of the through-hole, and the resin component of the prepreg 8 appears instead of the cover film 6 and the adhesive layer 7, which is the same as that of a normal rigid multilayer printed wiring board. Thus, an inexpensive rigid flex-printed wiring board free of molding voids and having excellent consistency can be obtained, and excellent matching can be obtained.

8 to 13 show the steps of the method of the present invention. FIG. 8 shows a circuit in which a circuit is formed on a flexible copper-clad laminate to form a flexible printed wiring board (A
Is a plan view, B is a cross-sectional view, and the same applies hereinafter), FIG. 9 is a view showing a portion corresponding to a through-hole processing portion after laminating a cover film, and FIG. 10 is a processed cover film and a flexible printed wiring board. FIG. 11 shows a circuit formed on a rigid copper-clad laminate to form a rigid printed wiring board, FIG. 12 shows a prepreg having an outer shape processed to remove unnecessary portions, and FIG. 13 shows an outer shape of a rigid portion and a flexible portion. The structure as shown in FIG. 1 can be formed by a method of manufacturing a rigid flex printed wiring board which is integrated by a processed prepreg and includes such steps. According to this method, when the through-hole is drilled, the cover film 6 and the adhesive layer 7 are not directly exposed on the inner wall of the through-hole, and the resin component of the prepreg 8 appears instead of the cover film 6 and the adhesive layer 7. And stabilization of plating throwing power is obtained.
In addition, an inexpensive rigid flex printed wiring board having no molded voids and excellent in matching can be obtained. In these embodiments, the metal conductors 5 are provided on both sides of the base film 4 and the rigid printed wiring boards 9 are laminated on both sides. In the present invention, the metal conductors 5 and the rigid printed wiring boards 9 are provided only on one side. It may be.

[0012]

As described above, according to the present invention, since the cover film covering the flexible printed circuit board is laminated and the portion corresponding to the processed portion of the through-hole including the adhesive layer is removed after the lamination of the cover film. Since the cover film and the adhesive layer are not directly exposed on the inner wall of the through-hole when processing, the throwing power of plating is good, and there is no molding void with excellent matching between the rigid part and the flexible part. Rigid flex printed wiring boards can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of one embodiment of the present invention.

FIG. 2 is a sectional view of a conventional rigid flex printed wiring board.

FIG. 3 is a plan view of an example of a rigid flex printed wiring board.

FIG. 4 is a plan view showing a cover film layer of a conventional rigid flex printed wiring board.

FIG. 5 is a plan view showing a cover film layer of a conventional rigid flex printed wiring board.

FIG. 6 is a cross-sectional view II of a conventional rigid flex printed wiring board.

FIG. 7 is a plan view showing a cover film layer of the rigid flex printed wiring board.

FIG. 8 is a view showing a processing state of each step included in the manufacturing method of the present invention. FIG. 8A is a plan view. FIG. 8B is a sectional view.

FIG. 9 is a diagram showing a processing state of each step included in the manufacturing method of the present invention. FIG. 9A is a plan view. FIG. 9B is a sectional view.

FIG. 10 is a view showing a processing state of each step included in the manufacturing method of the present invention. FIG. 10A is a plan view. FIG. 10B is a sectional view.

FIG. 11 is a view showing a processing state of each step included in the manufacturing method of the present invention. FIG. 11A is a plan view. FIG. 11B is a sectional view.

FIG. 12 is a view showing a processing state of each step included in the manufacturing method of the present invention. FIG. 12A is a plan view. FIG. 12B is a sectional view.

FIG. 13 is a diagram showing a processing state of each step included in the manufacturing method of the present invention. FIG. 13A is a plan view. FIG. 13B is a sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rigid part 2 Rigid part 3 Flexible part 4 Base film 5 Metal conductor 6 Cover film 7 Adhesive layer 8 Prepreg 9 Rigid printed wiring board 10 Circuit pattern 11 Through hole 12 Prepreg

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/46 H05K 3/28

Claims (2)

(57) [Claims] 1. A rigid-flex printed wiring board obtained by integrating a flexible part in which a flexible printed wiring board is covered with a cover film and a rigid part made of a rigid printed wiring board, wherein the rigid part of the cover film of the flexible part is In the part included in the department,
A rigid flex printed wiring board characterized in that a portion of the cover film corresponding to a through-hole processed portion after lamination and an adhesive layer thereof are removed in advance. 2. A method for manufacturing a rigid-flex printed wiring board, comprising: a flexible portion in which a flexible printed wiring board is covered with a cover film; and a rigid portion formed by the rigid printed wiring board. Forming and processing the flexible printed wiring board, removing the portion corresponding to the through-hole processed portion after laminating the cover film in advance, and covering the flexible printed wiring board with the removed cover film to form a flexible portion. Manufacturing, forming a circuit on the rigid copper-clad wiring board, processing the rigid printed wiring board into a rigid portion, processing the outer shape of the prepreg and removing unnecessary portions, and the rigid portion and the flexible portion. Using a prepreg from which the external processing has been performed and unnecessary portions have been removed. Manufacturing method of rigid flex printed wiring boards.