JP2758099B2 - Multi-layer flexible 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 multilayer flexible printed wiring board in which two adjacent conductor patterns among a plurality of laminated conductor patterns are electrically connected to each other by blind via holes that are not penetrated. It is.

[0002]

2. Description of the Related Art Such a conventional multilayer flexible printed wiring board has a configuration as shown in FIG. That is, the copper foil on both sides of each of the two double-sided copper-clad flexible printed wiring board materials (1) is subjected to pattern etching to form the inner conductor pattern (2) and the outer conductor pattern (3). Via holes are formed at predetermined positions by applying copper plating to the inner and outer conductor patterns (2) and (3) so as to electrically connect to each other. 1) are polymerized with an insulating adhesive (4) such as prepreg resin interposed therebetween, and are pressed together by lamination pressing to be integrated. By this integration, the via hole becomes a blind via hole (5) which is a non-through conductive hole. Also, a through-hole (6) in which a through-hole formed at a predetermined location is plated with copper.
Thus, the conductor patterns (2) and (3) of the four layers are electrically connected.

[0003]

However, the above-mentioned multilayer flexible printed wiring board has the following problems.
That is, since the blind via holes (5) exist on the outer surfaces on both sides which are the mounting surfaces of the electronic components, not only the parts cannot be mounted on the blind via holes (5) but also the outer layer conductor patterns (3). ) Must be routed so as to avoid the blind via hole (5), which is a factor that hinders an increase in circuit density and also impairs the degree of freedom in circuit design. ing.

Although the flexible printed wiring board material (1) is made of a flexible material such as a polyimide film, a plurality of flexible printed wiring board materials are interposed via an insulating adhesive (4). Since (1) is laminated, it cannot be bent or bent when assembling an electronic device or the like. Therefore, in the case of three-dimensional installation, separate members such as connectors and flexible printed wiring cables must be used, and the cost increases with the increase in the number of parts and the number of work steps, and the connection reliability is increased. Of the flexible printed wiring board material (1)
Therefore, the area for forming a circuit is correspondingly reduced, and the component mounting density is further reduced.

Accordingly, the present invention provides a multilayer flexible print which can be mounted at a high density while having a blind via hole, and can be bent or bent so that a three-dimensional mounting can be performed without requiring a separate member. It is a technical object to provide a wiring board.

In the present invention, as a technical means for solving the above-mentioned problem, a multilayer flexible printed wiring board is configured as follows. That is, in the multilayer flexible printed wiring board in which an inner conductive pattern formed on a plurality of flexible printed wiring board materials and an outer conductive pattern for component mounting are laminated with an insulating adhesive interposed therebetween, wherein a plurality of multilayer portions and are stacked outer layer conductor pattern, the each multilayer unit off connection conductors are formed for electrically connecting the mutual Rekishibu <br/> Le portions, in each of the multilayer portion and A non-penetrating blind via hole electrically connecting the adjacent conductor patterns, and the insulating adhesive interposed between the adjacent flexible printed wiring board materials and filled in the blind via hole in a filled state. Material, and the outer layer conductor pattern is attached to the outside opening end of each of the blind by-holes so as to cover it. And a circuit conductor section forming part, the flexible part, the inner side
The flexible printed wiring board is made of only the material .

[0007]

[Function] Since each blind via hole is filled with the insulating adhesive material, the outer layer side opening end portion of each blind via hole is closed with the flat surface insulating adhesive material. A conductor portion can be stably formed on the outer layer side opening end portion of the blind via hole by, for example, copper plating in a through-hole forming step, and the conductor portion can be used as a component connection land or a circuit pattern. And the degree of freedom in circuit design is improved.

[0008] Furthermore, the flexible portion made of only the inner layer side flexible printed wiring board material on which the connecting conductor portions for electrically connecting the respective multilayer portions are formed is extremely excellent in flexibility and can be freely bent or folded. Therefore, at the time of mounting, by bending or bending the flexible part, each multilayer part can be incorporated three-dimensionally as a required form without using another member such as a connector or a flexible printed wiring cable, and the number of parts can be reduced. The cost can be reduced by reducing the number of work steps, and the connection is directly performed without using a separate member, so that the connection reliability is remarkably improved. Furthermore, flexible
Even if the shibble part is bent or bent,
Since the outer conductor pattern is hardly affected,
Flexible by mounting components such as chips on the conductor pattern
Even if the module is bent or bent, the mounted parts may come off
There is no.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention when applied to a four-layer structure. Next, this structure will be described based on its manufacturing steps. First, the copper foil of the single-sided copper-clad flexible printed wiring board material (10) on the inner layer side is pattern-etched to form the inner layer conductor pattern (1
4), a connecting conductor portion (24) at the center and a connecting conductor portion (25) at one end are formed, and then one surface of the base film (26a) is formed on the surface on which the inner layer conductor pattern (14) and the like are formed. A film coverlay (26) formed by applying an adhesive (26b) to the film coverlay (26) is thermocompression-bonded.
6) protects the inner conductor pattern (14) and the like.

[0010] A double-sided copper-clad flexible printed wiring board material on the outer layer side for forming the third and fourth layers (12)
After copper holes are formed in predetermined locations, copper plating is performed to form via holes for electrically connecting the copper foils on both surfaces to each other. The copper foil on one surface of the wiring board material (12) is subjected to pattern etching to form a third layer. An inner conductor pattern (15) is formed. Next, the inner layer side flexible printed wiring board material (1
On both sides of 0), a single-sided copper-clad flexible printed wiring board material (11) and a double-sided copper-clad flexible printed wiring board material (12) on the outer layer side on which no conductor pattern is formed are removed. And facing
Insulating adhesive (2) made of prepreg resin between each
By laminating press with 7) interposed, the layers are integrated into a laminated state. At the time of this laminating press, the insulating adhesive (2
Press conditions and the amount of the insulating adhesive (27) are set so that 7) is filled in each via hole in a filled state. Therefore, the outer layer opening end portion of the via hole is closed flush with the flat surface of the insulating adhesive, and non-penetrating blind via holes (17) and (18) are formed. Subsequently, through holes (2) for conducting through the conductor patterns (13) to (16) are formed by drilling a through hole penetrating the whole by drilling or the like at a predetermined location and then performing copper plating.
8) is formed. When copper plating for forming the through hole (28) is performed, the blind via hole (1
7) and (18), plated copper is also adhered on the flat surface of the insulating adhesive (27) for closing the open end of the outer side and the periphery thereof, and the blind via holes (17) and (1)
8) Circuit conductors (19) and (20) are formed on the outer opening end so as to cover each other.
9) and (20) are used as lands and circuit patterns for component mounting. Finally, the copper foil on the outer side of each of the outer layer side flexible printed wiring board materials (11) and (12) is pattern-etched to form outer layer conductor patterns (13) and 1st layer and 4th layer, respectively. Form (16).

As shown in the figure, the outer conductor patterns (14) and (15) and the outer conductor patterns (13) and (1)
6) and two multilayer parts (21), (22)
And a connecting conductor portion (24) protected by a film coverlay (26) and between the two multilayer portions (21) and (22).
Thus, a flexible portion (23) made of only the inner layer side flexible printed wiring board material (10) to be electrically connected is formed. As the forming means, a part corresponding to the flexible portion (23) in each of the outer layer side flexible printed wiring board materials (11) and (12) may be removed in advance when performing the above-described lamination pressing, or After performing a laminating press without interposing an insulating adhesive (27) on a portion corresponding to the flexible portion (23), each outer layer side flexible printed wiring board material (11), (1)
The portion corresponding to the flexible portion (23) in 2) is removed by a half punch. Since the flexible portion (23) is made of a single flexible printed wiring board material (10), it has extremely high flexibility, and can be freely bent or folded.
Three-dimensional integration is possible without using a separate member such as a connector. In addition, terminal plating is applied to an end of the inner layer side flexible printed wiring board material (10) protruding from one of the multilayer portions (22), or a backing reinforcing plate for inserting a connector is attached. Can be.

In the above embodiment, a four-layer structure has been described. However, the present invention can be similarly applied to a structure having three or more layers. Five layers can be formed by using a copper-clad flexible printed wiring board material. Further, when a double-sided copper-clad flexible printed wiring board material is used as the outer layer side flexible printed wiring board material (11), the number of layers becomes six.

[0013]

As described above, according to the multilayer flexible printed wiring board of the present invention, each blind via hole is filled with an insulative adhesive to fill the outer layer opening end of each blind via hole with a flat surface. The circuit conductor is stably formed at the outer layer side opening end of the blind via hole by closing with the insulating adhesive material. Since it can be used, the circuit density of the outer conductor pattern can be significantly increased, and the degree of freedom in circuit design is improved.

[0014] Further, since a flexible portion made of only the inner-layer-side flexible printed wiring board material on which the connecting conductor portion for electrically connecting the respective multilayer portions is formed is provided, the flexible portion can be bent arbitrarily. By folding, each multilayer part can be three-dimensionally incorporated as a required form without using a separate member such as a connector or a flexible printed wiring cable, and a considerable cost reduction can be achieved by reducing the number of parts and work steps. Also, since it is directly connected without using a separate member,
Connection reliability is greatly improved. Furthermore, the flexible part
Bends or bends, the effects of deformation or movement
Since almost no conductor pattern is received, the outer conductor pattern
Mount the components such as chips on the
Even if bent or bent, there is no possibility that the mounted components are peeled off.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a conventional wiring board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Inner layer side flexible printed wiring board material 11, 12 Outer layer side flexible printed wiring board material 13, 16 Outer layer conductor pattern 14, 15 Inner layer conductor pattern 17, 18 Blind via hole 19, 20 Circuit conductor part 21, 22 Multilayer part 23 Flexible part 24 Connecting conductor 27 Insulating adhesive

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H05K 3/46

Claims (1)

(57) [Claims] An inner conductor pattern formed on a plurality of flexible printed wiring board materials and a component mounting part.
A multi-layer flexible printed wiring board in which the outer conductor pattern is laminated with an insulating adhesive interposed therebetween, wherein a plurality of multilayer portions in which the inner conductor pattern and the outer layer conductor pattern are laminated; a full Rekishiburu portion connecting conductor portion electrically connected is formed between the the non-through blind via holes, wherein electrically connecting the respective conductive patterns adjacent in each multilayer unit, the adjacent flexible printed wiring board The insulating adhesive material interposed between the materials and filled in the blind via holes in a filled state, and the outer opening end of each of the blind via holes is attached to cover the outer side of the blind via holes so as to cover the blind via holes. A circuit conductor portion forming a part of an outer layer conductor pattern, wherein the flexible portion is an inner layer side flexible member.
A multilayer flexible printed wiring board comprising only a printed wiring board material .