JPH06326424A - Multilayer interconnection board - Google Patents

Abstract

PURPOSE:To prevent generation of cracks and breaking by reducing the concentration of stress on the boundary part between a flexible wiring board and a hard board. CONSTITUTION:In the title multilayer interconnection board formed by laminating a flexible wiring board and a hard board 12 through an adhesive material layer 13 in such a manner that a part of the flexible wiring board is exposed, the end part of the adhesive material layer 13 is protruded to the boundary part of the flexible wiring board and the hard board 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite multilayer printed wiring board having a flexible portion in one substrate, or a multilayer flexible printed wiring board.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG. FIG. 5 is a perspective view of a composite multilayer printed wiring board according to a conventional example. In FIG. 5, 10 is a hard substrate and 11 is a flexible substrate.
Often used by bending.

[0003]

By the way, in the composite multilayer printed wiring board of FIG. 5, the boundary portion between the hard substrate 10 and the flexible substrate 11 is repeatedly bent as it is attached to or detached from the equipment. Due to the stress concentration due to, there were cases where breakage and disconnection occurred. This state is shown in FIG. In FIG. 6, 12 is a double-sided hard substrate, 13 is an adhesive layer, 14 is an insulating sheet, 15
Is a pattern. Among these, cracks 16 are generated in the adhesive layer 13 by repeated bending.

In order to prevent the generation of the cracks 16, conventionally, as shown in FIG. 7, a reinforcing tape 17 is provided so as to avoid stress concentration between the hard substrate 10 and the flexible substrate 11.
There is a measure for sticking or a measure for coating a reinforcing material 18 made of resin or rubber as shown in FIG. However, such a method has a problem that the number of steps is increased, the cost is increased, the shape is complicated, and the reliability is lowered. Therefore, an object of the present invention is to provide a highly reliable composite multilayer printed wiring board capable of preventing stress concentration between a hard substrate and a flexible substrate by a simple method and avoiding the occurrence of cracks.

[0005]

In order to achieve the above object, the present invention provides a flexible substrate and a hard plate with an adhesive layer so that a part of the flexible substrate is exposed. In the multi-layer substrate laminated via the substrate, the end portion of the adhesive layer is projected at the boundary portion between the flexible substrate and the hard plate.

[0006]

Since the end of the adhesive layer is projected at the boundary between the flexible board and the hard board, even when the flexible part of the multilayer wiring board is bent, the flexible board and the hard board are hardened. The bending stress applied to the boundary portion of the substrate is dispersed by the protruding portion of the adhesive layer, and the boundary portion is not cracked or broken due to stress concentration.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 is a sectional view of a composite multilayer printed wiring board according to this embodiment, FIG. 2 is a sectional view showing a curved state of FIG. 1, and FIG. 3 is a view for explaining a method of laminating the composite multilayer printed wiring board of FIG. FIG. The same functional parts as those of the conventional example shown in FIG. 5 are designated by the same symbols. Here, differences from the conventional example will be mainly described.

As shown in FIG. 1, the present embodiment is characterized in that a polyimide resin adhesive layer 13 sandwiched between a double-sided hard plate 12 and an insulating sheet 14 is further inward from an inner end surface of the double-sided hard plate 12. It is a point that is slightly projected.

Although the protrusion 1 is harder than the flexible substrate 11 having flexibility, it does not deform at all like the hard substrate 10. Therefore, when the composite multilayer printed wiring board having such a structure is bent and attached to a device, the deformation due to bending is dispersed to the protruding portion 1 as shown in FIG.
It is possible to avoid stress concentration between zero. Therefore, unlike the conventional case, cracks and breaks do not occur, and reliability can be improved.

A method for laminating the composite multilayer printed wiring board will be described below.

As shown in FIG. 3, the double-sided hard plate 1 is lower than the lower layer.
12, adhesive layer 113, insulating sheet 114, adhesive layer 1
13 'and a double-sided hard plate 112' are laminated in this order. Here, the adhesive layer 113 'is provided so as to slightly project inward from the inner end surface of the double-sided hard plate 112'. By laminating these, a composite multilayer printed wiring board as shown in FIG. 1 is obtained.

FIG. 4 is a sectional view of a composite multilayer printed wiring board according to another embodiment of the present invention. In this example, double-sided board
The sheets are stacked to form 6 layers. Double-sided hard plate 21 from the lower layer
2, adhesive layer 213, insulating sheet 214, adhesive layer 21
3 ', a double-sided hard plate 212' are laminated in this order, and the laminated body is further laminated in the opposite direction on the upper surface.

In this embodiment, the protrusions 2 are formed on the front and back sides of the flexible substrate 11 ', and similar to the embodiment of FIG. 1, the effect of stress distribution at the time of bending is obtained, and the rigid substrate 10' and the flexible substrate 10 'are flexible. It is possible to prevent cracks and fractures at the boundary with the substrate 11 ′.

[0014]

As described above, according to the present invention,
In the composite multilayer printed wiring board, it is possible to avoid stress concentration between the flexible board and the hard board due to bending or the like. Therefore, unlike the conventional case, the disconnection of the pattern and the crack of the flexible substrate do not occur, and the reliability can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a composite multilayer printed wiring board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a usage state of the composite multilayer printed wiring board of FIG.

FIG. 3 is a cross-sectional view for explaining a method for laminating the composite multilayer printed wiring board shown in FIG.

FIG. 4 is a cross-sectional view of a composite multilayer printed wiring board according to another embodiment of the present invention.

FIG. 5 is a perspective view of a composite multilayer printed wiring board according to a conventional example.

FIG. 6 is a cross-sectional view illustrating a problem of a composite multilayer printed wiring board according to a conventional example.

FIG. 7 is a perspective view of a composite multilayer printed wiring board according to another conventional example.

FIG. 8 is a perspective view of a composite multilayer printed wiring board according to still another conventional example.

[Explanation of symbols]

 1, 2 Projection part 11 Flexible printed circuit board 12 Double-sided hard board 13 Adhesive layer

Claims (1)

[Claims] 1. A multilayer wiring board in which a flexible substrate and a hard plate are laminated via an adhesive layer so that a part of the flexible substrate is exposed. A multilayer wiring board, characterized in that an end portion of the adhesive layer is projected at a boundary portion between a substrate having elasticity and the hard plate.