JP2003258426A - Multilayered rigid flexible substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rigid and flexible substrate, the rigid section of which can be multilayered efficiently and, at the same time, the flexible section of which is excellent in foldability and bendability. <P>SOLUTION: In a multilayered printed wiring board having a rigid section and a flexible section, the rigid and flexible substrate is configured such that a conductor circuit exists only on one side of a flexible layer extended from the rigid section, and in addition, conductor circuits exist on both sides of a flexible layer formed as an internal layer of the rigid section. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid-flex substrate which has a high-multilayer rigid portion and a flexible portion having high bending and bending characteristics, and which can be manufactured inexpensively and easily.

[0002]

2. Description of the Related Art A rigid flex board is a composite board that includes a composite lead between wirings in addition to the function of a general multilayer printed wiring board. Unlike a conventional flexible board, a rigid part and a flexible part are integrated. Things
This is a multi-layer printed wiring board that can realize three-dimensional wiring independently, omits connectors, etc., and is extremely advantageous for cost reduction during assembly by making electronic parts and electronic devices lighter, thinner, smaller, and more functional.

Such a rigid-flex substrate is usually a flexible substrate in which a part of the material corresponding to the inner layer of a multilayer printed wiring board is composed of a flexible substrate to form a predetermined wiring circuit. Laminate through the insulating adhesive layer provided with an opening in the part to be heated, pressurize, form a through hole, after copper plating, form a circuit of the outer layer, and cut the outer shape into an arbitrary shape, Complete.

FIG. 7 shows a conventional rigid flex board 2
0 is a sectional view of the rigid portion 21 and the flexible portion 2
2 and has a connection terminal 23.

In recent years, the flexible part has been drawn out from a plurality of layers having different rigid parts in order to improve the function.

FIG. 8 shows such a rigid flex board 3
FIG. 10 is a cross-sectional view of No. 0, which includes flexible portions 32a and 32b pulled out from the rigid portion 31, and has a connection terminal 33a.
Is equipped with.

Recently, in the fields of notebook type terminals, mobile terminals such as mobile phones, and digital cameras,
Due to the advancement of higher functionality, lighter, thinner, smaller, and smaller devices, the storage space for electronic components will be further reduced, and the rigid part of the rigid / flex board will have a higher number of layers and the flexible part will be more than ever. There has been a growing demand for structures with high bending and bending characteristics.

However, when a flexible substrate having a plurality of conductor layers on one side is laminated for the purpose of increasing the number of layers in the rigid portion, thermal contraction with a hard material different in material is different, and there arises a problem that inter-layer alignment accuracy is particularly difficult. To do. Therefore, it is difficult to reduce the diameter of the through-hole and the diameter of the connection land. Further, the processing of the flexible material with the one-sided copper foil has lower rigidity as compared with the flexible material with the double-sided copper foil, and thus the handling property is poor and the productivity is low in various processing steps. In addition, since the flexible part conductor layer inside the rigid part is present only on one side, the increase in the number of conductor layers causes an increase in the rigid lamination process and an increase in the circuit forming process, which increases the material cost and the processing cost. I have a problem.

On the other hand, when a flexible material with a double-sided copper foil is adopted to form a rigid flex board, the number of laminated layers is reduced and the processing cost can be reduced. Further, since coverlays are respectively placed on the double-sided conductors to protect the conductors, the thickness of the flexible portion itself is increased, the rigidity is increased, and the workability is improved. However, in the case of the flexible board with the double-sided copper foil, the thickness of the flexible portion is increased, and the rigidity is increased, and the flexibility of the flexible portion, which was excellent in the case of the flexible board with the single-sided copper foil, is poor.
There was a problem that the 3D structure originally required for rigid-flex substrates could not be supported.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is capable of efficiently forming a multi-layer structure, is excellent in workability and cost, and has the original characteristics of flexibility. It is an object of the present invention to provide a rigid flex board having high bending resistance.

[0011]

The present invention has been made in order to achieve the above-mentioned object. The first invention is that the flexible layer extending from the rigid portion has a conductor circuit on only one surface thereof. In addition, the flexible layer as the inner layer of the rigid portion is a rigid flex substrate having conductor circuits on both surfaces thereof. A second invention is a rigid flex in which a coverlay layer for protecting a conductor layer of a flexible layer extending from the rigid portion is covered only on the conductor layer side, and a portion on the back side having no conductor layer is removed. The substrate. A third aspect of the invention is a rigid-flex substrate in which a flexible portion extends from a plurality of layers of the rigid portion.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 is a plan view of a substrate as seen from directly above, and FIG. 2 is a sectional view of the substrate. In both figures, the rigid-flex board 10 is provided with a rigid portion 11, a flexible portion 12a and a flexible portion 12b, and a structure in which a connection terminal is provided at each flexible end portion. Also, FIG.
As shown in, the flexible part 1 inside the rigid part 11
2a and 12b have circuits on both sides, and the flexible portions 12a and 12b extending from the rigid portion are formed by completely removing the copper foil on the back surface of the conductor layer and the coverlay layer for protecting the conductor layer. ing.

In this embodiment, the example in which the number of flexible portions extending from the rigid portion is two is taken up, but the function of the present invention can be sufficiently exhibited if there is one or more flexible portions. is there. The structure of the rigid portion is not limited, and for example, a build-up layer including BVH (blind via hole) may be formed.

The rigid flex substrate of the present invention uses, for example, a flexible material with double-sided copper foil, has a double-sided conductor circuit in the flexible layer inside the rigid portion, and
In order to improve the bending and bending characteristics, the conductor layer of the flexible part is completely removed by removing the copper foil on one side by a method such as etching, and the cover layer is removed to make the conductor layer a single layer. Can be manufactured.

Characteristic Evaluation In order to evaluate the bending property and bending property of the flexible portion of the rigid / flex substrate structure of the present invention, a test substrate was prepared and the property evaluation results are shown below.

Characteristic Evaluation Example 1 Test piece width 8 mm shown in FIG. 3 Conductor circuit L / S = 100 μm
A substrate for bending / bending characteristic evaluation of 100 μm / 100 μm was prepared, and a test piece was prepared using the pusher shown in FIG.
Bend at 0 °, apply a load of 3 kg, and hold for 5 seconds. Then, the test piece is returned to the 0 ° position, a load of 3 kg is applied, and the test piece is allowed to stand for 5 seconds. Table 1 shows the results of a test in which 180 ° → 0 ° is set as one cycle and the number of cycles in which electrical connection of the conductor is lost (the conductor is broken) is taken as the characteristic value of bending of the flexible portion.

[0017]

[Table 1]

Characteristic Evaluation Comparative Example 1 The test results shown in FIG. 4 are shown in Table 1 together with the test results obtained by the above evaluation method.

Characteristic evaluation example 2 Test piece width 8 mm conductor circuit L / S = 100 μm shown in FIG.
A substrate for flexural characteristics evaluation of 100 μm / 100 μm was prepared and the test jig shown in FIG. 6 was used. The test piece was rotated once inside the jig with a bending diameter of φ7.0 and the jig was placed at a position of 170 °. Fix it to and bend it to the exact 0 ° position using the power of a motor. One cycle is 170 ° → 0 ° → 170 °, and one cycle is operated for about 2 seconds. The electrical connection of the conductor was checked during this operation, and the number of cycles at which the conductor was broken was used as the characteristic value of the flexible flexibility, and the test results are shown in Table 2.

[0020]

[Table 2]

Characteristic Evaluation Comparative Example 2 The test results shown in FIG. 4 are shown in Table 2 together with the test results obtained by the above evaluation method.

Summary of Characteristic Evaluation Examples In the characteristic evaluation examples 1 and 2 and the characteristic comparison examples 1 and 2, the number of disconnection cycles was measured. From the data shown in Tables 1 and 2, it can be clearly determined that the flexible portion structure of the present invention is superior in bending characteristics and bending characteristics as compared with the characteristic evaluation comparative examples.

[0023]

The rigid flex substrate of the present invention is
A three-dimensional structure can be easily formed by forming the flexible portion as a single-sided conductor having a structure with excellent bending and bending characteristics. Further, by using the flexible material with the double-sided copper foil in the flexible portion, the substrate is excellent in handleability during substrate processing and has high productivity. At the same time, since the flexible layer inside the rigid portion has conductor layers on both sides, it has a structure advantageous for increasing the number of layers of the rigid portion.
Therefore, according to the present invention, it is possible to efficiently provide a rigid portion with a high number of layers, and to provide a rigid flex substrate having excellent bending and bending characteristics of a flexible portion at low cost.

[Brief description of drawings]

FIG. 1 is an explanatory plan view of a rigid-flex substrate of the present invention.

FIG. 2 is an explanatory cross-sectional view of the rigid flex substrate of the present invention.

FIG. 3 is a plan explanatory view of a flexible portion bending / bending characteristic evaluation substrate of the substrate of the present invention and an enlarged sectional explanatory view of a main portion thereof.

FIG. 4 is a plan explanatory view of a flexible portion bending / bending characteristic evaluation substrate of a conventional substrate and an enlarged sectional explanatory view of a relevant portion thereof.

FIG. 5 is a schematic explanatory view showing a bending test method.

6A and 6B are a cross-sectional explanatory view and a plan explanatory view of a bending test jig.

FIG. 7 is a cross-sectional explanatory view of a conventional rigid flex board (one flexible part).

FIG. 8 is an explanatory cross-sectional view of a conventional rigid flex board (two flexible parts).

[Explanation of symbols]

10, 20, 30: Rigid flex substrates 11, 21, 31: Rigid parts 12a, 12b, 22, 32a, 32b: Flexible parts 23, 33a: Connection terminals 40: Bending and bending characteristic evaluation test piece 41: Coverlay 42: conductor 43: flexible base

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5E346 AA06 AA12 AA15 AA22 AA32                       AA51 BB11 CC09 EE44 GG28                       HH11

Claims (3)

[Claims] 1. In a multilayer printed wiring board having a rigid portion and a flexible portion, the flexible layer extending from the rigid portion has conductor circuits on only one side thereof, and the flexible layers inside the rigid portion are on both sides thereof. A rigid flex board characterized by the presence of a conductor circuit. 2. The cover lay layer for protecting the conductor layer of the flexible layer extending from the rigid portion is covered only on the conductor layer side, and is removed on the back side where there is no conductor layer. The rigid flex substrate according to claim 1. 3. The rigid / flex board according to claim 1, wherein the flexible portion extends from a plurality of layers of the rigid portion.