JPH05327211A - Multilayer flexible printed board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a multilayer flexible printed board enabling attainment of high-density wiring and being excellent in electrical and mechanical characteristics. CONSTITUTION:A multilayer flexible printed board of which conductor circuits 6a and 7a in a plurality are laminated with insulative films 1, 2 and 3 provided intermediately. In respect to three layers, upper, middle and lower, being adjacent to each other at least, the part of the insulative film 1 of the upper layer corresponding to the end part 6b of the conductor circuit 6a of the middle layer is removed, so that the end part 6b of the conductor circuit 6a of the middle layer be exposed, while the part of the insulative film 2 of the middle layer corresponding to the end part 7b of the conductor circuit 7a of the lower layer is removed, so that the end part 7b of the conductor circuit 7a of the lower layer be exposed. The exposed end parts 6b and 7b of the conductor circuits 6a and 7a of the middle and lower layers are arranged in the same direction respectively and disposed in the form of two steps, upper and lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer flexible printed board and a method for manufacturing the same.

[0002]

2. Description of the Related Art Flexible printed circuit boards are used in a wide range of fields including office equipment such as word processors. As shown in FIG. 7, a flexible printed circuit board of this type is usually made of a strip-shaped rolled copper film on a base film 20 made of a plastic insulating film such as polyester resin or polyimide resin via an adhesive 21 such as acrylic resin. A foil or an electrolytic copper foil is attached, and thereafter, pattern formation with a photoresist and etching are performed to form a predetermined conductor circuit 22. Then, a cover coat film made of a polyimide film with an adhesive 23 is attached to the conductor circuit 22, or a cover coat ink is applied to form the insulating layer 24. When forming the insulating layer 24, the end portion (connection terminal) 22a of the conductor circuit 22 connected to the connector or the like is not covered with the insulating layer 24 and is exposed to the end portion of the base film 20.

[0003]

However, in the fields of the electric and electronic industries, from the viewpoint of downsizing of equipments, etc., the flexible printed circuit boards used in the above equipments are becoming finer patterns, and in the method of mounting components. Surface mounting is often used. However, as shown in FIG.
In a conventional flexible printed circuit board, connection terminals 22a for mounting components are arranged on the same plane and connected to terminals (not shown) of electronic components by soldering, bonding, connectors or the like. Therefore, when the terminal pitch of the electronic component is narrowed due to the miniaturization of the device as described above and the conductor width of the connection terminals 22a of the flexible printed circuit board and the spacing between the connection terminals 22a are accordingly reduced, the flexible printed circuit board is reduced. There is a problem that the electrical characteristics and mechanical characteristics of the are deteriorated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a multilayer flexible printed circuit board which enables high-density wiring and is excellent in electrical characteristics and mechanical characteristics, and a manufacturing method thereof.

[0005]

In order to achieve the above object, the present invention provides a multilayer flexible printed circuit board in which a plurality of metal circuit parts are laminated in multiple stages with an insulating layer interposed therebetween, and at least one of them is provided. In the upper, middle, and lower three layers adjacent to, the upper insulating layer corresponding to the end of the middle metal circuit part is removed to expose the end of the middle metal circuit part. , The end of the insulating layer of the middle layer corresponding to the end of the lower metal circuit part is removed to expose the end of the lower metal circuit part, and the exposed middle and lower metal circuit parts The first gist is a multi-layer flexible printed circuit board whose ends are aligned in the same direction and arranged in a staircase pattern of two steps above and below, and upper and lower metal circuit parts are provided on the upper and lower surfaces of an insulating layer serving as a central layer, respectively. And the lower metal circuit part A step of preparing a first substrate in which a portion of an insulating layer corresponding to an end portion and a portion of an upper metal circuit portion are removed and a window portion is formed, and a metal conductor layer is formed on an upper surface of the insulating layer to be a central layer. And a portion of the insulating layer and a portion of the metal conductor layer corresponding to the first perforated portion of the first substrate are removed more largely than the first perforated portion and the second perforated portion is formed. On the upper surface of the first substrate, a step of preparing a second substrate formed on the upper part of the first substrate, a step of preparing a third substrate on which a metal conductor layer is formed on the lower surface of an insulating layer which is a center layer, Second above
Laminating and adhering the substrates to each other to expose the end portions of the upper and lower metal circuit portions of the first substrate from the second perforated portion of the second substrate, and the first substrate The steps of laminating and adhering the third substrate to the lower surface, the steps of forming metallic circuit portions on the metal conductor layers of the second and third substrates, and the laminating and adhering the first to third substrates, respectively. A second gist is a method for producing a multilayer flexible printed circuit board including a step of removing an unnecessary portion around the second perforated portion of the obtained laminated plate.

[0006]

That is, in the multilayer flexible printed circuit board of the present invention, a plurality of metal circuit parts are laminated in a multi-step manner with an insulating layer interposed, and at least the upper, middle, and lower three layers adjacent to each other have the middle layer. Of the upper insulating layer corresponding to the end of the metal circuit part of is exposed to expose the end of the middle metal circuit part, and the insulation of the middle layer corresponding to the end of the lower metal circuit part. The layer portion is removed to expose the end portion of the lower metal circuit portion. The exposed end portions of the metal circuit portions of the middle layer and the lower layer are arranged in the same direction, and are arranged in a two-step staircase shape. As described above, in the multilayer flexible printed circuit board of the present invention, at least in the upper, middle, and lower three layers adjacent to each other, the end portion (connection terminal) of the metal circuit portion is divided into two layers of the middle layer and the lower layer. I am trying to provide it. Therefore, even when the same number of connection terminals as the conventional one is provided at the end of one flexible printed circuit board, the number of the connection terminals can be reduced to half in each layer. Therefore, in each layer,
The connection terminal width and the interval between the connection terminals can be widened on the same plane, and the electrical characteristics and mechanical characteristics are not deteriorated. Further, according to the manufacturing method of the present invention, the above-mentioned multilayer flexible printed board can be easily manufactured.

Next, the present invention will be described in detail based on examples.

[0008]

1 is a perspective view of an end portion of a multilayer flexible printed circuit board showing an embodiment of the present invention, and FIG.
It is a -X 'sectional view. In these figures, 1, 2, 3
Is an insulating film made of a polyimide film (Apical, manufactured by Kanebuchi Chemical Co., Ltd.), and among them, the polyimide films 1 and 2 act as substrates (base films) and at the same time an insulating layer covering the lower conductor circuits 6a and 7a. That is, the polyimide film 3 functions as a substrate (base film). Numerals 4 and 5 are adhesive layers made of an epoxy adhesive (manufactured by Nitto Denko Corporation). Reference numerals 6a and 7a denote strip-shaped conductor circuits formed by rolling copper foil (BHY, manufactured by Nippon Mining Co., Ltd.) by photoresist and etching.
6b and 7b are end portions (connection terminals) of the conductor circuits 6a and 7a. Reference numerals 8a and 9a are conductors formed by rolling copper foil (BHY, manufactured by Nippon Mining Co., Ltd.) by photoresist and etching. Reference numeral 10a is through-hole copper plating applied to the inner peripheral wall surface of the through-hole 10 and the conductor portions 8a and 9a.

The multilayer flexible printed board can be manufactured, for example, as follows. That is, first, a film 1 made of a polyimide film 1,
Rolled copper foil on the surface of a few adhesive layers 1a, 2a, 3a
Three single-sided copper-clad substrates, namely, a single-sided copper-clad substrate for the lower layer, a single-sided copper-clad substrate for the middle layer, and a single-sided copper-clad substrate for the upper layer, were respectively prepared by adhering through. On the other hand, a photomask for forming the end portions (connection terminals) 6b, 7b of the conductor circuits 6a, 7a corresponding to the terminals of the electronic component was produced. This photomask has the connection terminals 6b and 7b.
Were produced in a staggered arrangement. Next, as shown in FIG. 3, the area A of the single-sided copper-clad base material 11 for the middle layer (the area corresponding to the end 7a of the lower conductor circuit 7,
The rolled copper foil 6, the film 2 and the adhesive sheet 2a) were used to form an internal hole 16 with a die. Next, as shown in FIG. 4, a rolled copper foil 7 was laminated on the lower surface of the film 2 of the single-sided copper-clad substrate 11 for the intermediate layer via an adhesive sheet 17 to prepare a double-sided copper-clad substrate 12. After that, FIG.
As shown in FIG. 3, the rolled copper foil 6 and 7 of the double-sided copper-clad substrate 12 is coated with a photosensitive resist 18, and the rolled copper foil is exposed, developed, and etched using the photomask. An upper conductor circuit 6a and a lower conductor circuit 7a were formed on the foils 6 and 7, respectively. Then, the photosensitive resist was removed.

Next, B of the single-sided copper-clad base material 13 for the upper layer
A partial region (a region corresponding to the end 6a of the upper conductor circuit 6 and comprising the rolled copper foil 8, the film 1 and the adhesive sheet 1a) was provided with an internal drawing opening 19 with a mold. Then, the back surface of the single-sided copper-clad base material 13 for the upper layer is adhered to the upper surface of the double-sided copper-clad base material 12 on which the circuit is formed via the adhesive sheet 4, and the back surface of the single-sided copper-clad base material 14 for the lower layer is adhered to the lower surface. It adhered through the adhesive sheet 5, and in that state, they were laminated and integrated by a hot pressing method. As shown in FIG. 6, a through hole 10 is bored in the base material laminated in this way to electrically connect the upper and lower conductor circuits 6a and 7a, and the through hole copper plating 10a is formed in the through hole 10. Was applied.
After that, the conductor circuits 8a and 9a were formed on the rolled copper foils 8 and 9. At this time, the connection terminals 6a and 7a are plated with nickel, gold, tin, solder or the like, if necessary. Next, it is processed into a predetermined outer shape by Thomson processing or metal mold processing.
At this time, unnecessary portions around the openings 16 and 19 are removed. Thereby, a desired multilayer flexible printed board can be obtained.

In the above embodiment, the connection terminals 6b and 7b are formed only on the rolled copper foils 6 and 7, but the invention is not limited to this, and the connection terminals 6b and 7 are formed on the rolled copper foil 8.
You may form the connection terminal similar to b.

Further, in the above-described embodiment, the holes 1 are formed in the single-sided copper-clad base materials 11 and 13 for the upper layer and the middle layer by using a die.
Although the holes 6 and 19 are formed, the holes may be formed by a laser method or a melting method. In addition, each of the openings 1
Although 6 and 19 are formed on the entire surface of the portion corresponding to the connection terminals 6b and 7b as in the above embodiment, they may be formed partially.

Further, in the above embodiment, the opening 16 is provided in the area A of the single-sided copper-clad base material 11 for the intermediate layer, and the rolled copper foil 7 is laminated on the lower surface thereof to form the double-sided copper-clad base material 12. Circuits are formed on both surfaces of the double-sided copper-clad base material 12 after that, but instead of this, a double-sided copper-clad base material without openings is prepared, and the circuit is formed on the double-sided copper-clad base material. Openings may be provided in the area A by a laser method or a melting method.

Two insulating plates are used in place of the single-sided copper-clad base materials 13 and 14 for the upper layer and the lower layer in the above embodiment,
The insulating plates may be attached to the upper and lower surfaces of the double-sided copper-clad base material 12 to be laminated and integrated.

In the multilayer flexible circuit board manufactured by such a method, the connection terminals 6b and 7b are arranged in two layers at the end portions thereof, that is, divided into two planes, so that one plane is formed. The number of the connection terminals 6b and 7b arranged can be halved. Therefore, the width of the connection terminals 6b, 7b provided at the end of the multilayer flexible circuit board and the space between the connection terminals 6b, 7b can be designed to be wide, and it is possible to cope with the finer terminal pitch of electronic components which is becoming smaller and smaller in recent years. In addition, it becomes possible to manufacture a multilayer flexible printed circuit board which is excellent in electrical characteristics and mechanical characteristics.

[0016]

As described above, according to the multilayer flexible circuit board of the present invention, at least adjacent to each other,
In the middle and lower three layers, the end portion (connection terminal) of the metal circuit portion is divided and provided in two layers of the middle layer and the lower layer. Therefore, even when the same number of connection terminals as the conventional one is provided at the end of one flexible printed circuit board, the number of the connection terminals can be reduced to half in each layer. Therefore, in each layer, the connection terminal width and the space between the connection terminals can be widened on the same plane, and the electrical characteristics and mechanical characteristics are not deteriorated. Further, according to the manufacturing method of the present invention, the above-mentioned multilayer flexible printed board can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a perspective view showing an end portion of a multilayer flexible printed circuit board according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line XX ′ in FIG.

FIG. 3 is an explanatory diagram of a method for manufacturing the multilayer flexible printed circuit board.

FIG. 4 is an explanatory diagram of a method for manufacturing the multilayer flexible printed circuit board.

FIG. 5 is an explanatory diagram of a method for manufacturing the multilayer flexible printed circuit board.

FIG. 6 is an explanatory diagram of a method for manufacturing the multilayer flexible printed circuit board.

FIG. 7 is a perspective view showing an end portion of a conventional flexible printed circuit board.

[Explanation of symbols]

 1,2,3 film 6a, 7a Conductor circuit

Claims (2)

[Claims] 1. A multi-layered flexible printed circuit board in which a plurality of metal circuit parts are laminated in multiple stages with an insulating layer interposed therebetween, wherein at least the upper, middle and lower three layers which are adjacent to each other, the middle metal layer. The part of the upper insulating layer corresponding to the end of the circuit part made of metal is removed to expose the end of the metal circuit part of the middle layer, and the insulation of the middle layer corresponding to the end of the metal circuit part of the lower layer is exposed. The layer portions are removed to expose the end portions of the lower metal circuit portion, and the exposed end portions of the middle and lower metal circuit portions are aligned in the same direction to form a two-step upper and lower step. A multilayer flexible printed circuit board characterized by being arranged. 2. The upper and lower metal circuit parts are formed on the upper and lower surfaces of the insulating layer serving as the central layer, respectively, and the insulating layer part and the upper metal circuit part corresponding to the ends of the lower metal circuit part. And the step of preparing a first substrate having a window portion removed therefrom and a metal conductor layer is formed on an upper surface of an insulating layer serving as a central layer, and a first hole is formed on the first substrate. A portion of the insulating layer and a portion of the metal conductor layer corresponding to the portion are removed to a greater extent than the first perforated portion to prepare a second substrate formed in the second perforated portion; A step of preparing a third substrate having a metal conductor layer formed on the lower surface of an insulating layer serving as a central layer, and a step of stacking and adhering the second substrate on the upper surface of the first substrate to form the second substrate. From the second perforated portion to the first
Exposing the ends of the upper and lower metal circuit parts of the substrate, laminating and adhering the third substrate to the lower surface of the first substrate, and adhering the second and third substrates to each other. A step of forming a metal circuit part on each of the metal conductor layers, and a step of removing unnecessary parts around the second perforated part of the laminated plate obtained by laminating and bonding the first to third substrates. A method of manufacturing a multilayer flexible printed circuit board, comprising: