Flex-rigid wiring board and manufacturing method thereof

Abstract

A flex-rigid wiring board having excellent connection reliability and a manufacturing method thereof are provided. A flex-rigid wiring board is provided by connecting a hard rigid board wherein a conductor circuit is provided on an insulating board, and a bendable flexible board wherein a conductor circuit is provided on an insulating board and a coverlay is provided to cover the conductor circuit. As an insulating base material of the flexible board, a bendable base material provided by impregnating a glass cloth with a resin and drying it is employed. On one surface of the flexible board, the conductor circuit is formed, and on the other surface, a dummy pattern is formed close to a bending part. Thus, base material deformation easily generated close to the bending part, conductor circuit disconnection, wave formation and the like can be prevented. The equivalent effects can be obtained by increasing the width of a wiring pattern of the conductor circuit or by curving the wiring pattern in the width direction, at the bending part on the flexible board.

Description

technical field [0001] The present invention relates to a rigid-flex circuit board composed of a flexible flexible part that can be bent and a rigid part formed of a hard material and a manufacturing method thereof. Background technique [0002] In recent years, rigid-flex multilayer circuit boards have been used in portable electronic devices such as foldable mobile phones. Such a circuit board is generally shown in FIG. 22 , and the rigid parts 500 and 520 without flexibility and the flexible part 510 with flexibility are connected through a flexible substrate 544, and the conductor layer of the plated through hole 502 is used to conduct electricity in the rigid part 500. The laminated flexible substrate 544 is connected to the pattern layers 504 and 506 on the surfaces of the rigid substrates 500 and 520 (for example, refer to Japanese Patent Application Laid-Open No. 5-90756). [0003] The rigid-flexible multilayer circuit board of the above-mentioned prior art is forme...

AI Technical Summary

Problems solved by technology

[0009] However, the polyimide film used as an insulating base material for flexible substrates has strong water absorption and large dimensional changes, so it is necessary to form a large diameter of the pad in advance, which is subject to design constraints. , in order to improve the alignment accuracy, the workpiece size needs to be made smaller

Therefore, there is a problem that excellent connection reliability cannot be obtained, and the same problem also exists in reliability tests such as thermal cycles.

[0010] In addition, since the resin film such as polyimide used as the insulating base material of the flexible substrate is formed by a single film, it is not formed by impregnating the resin on the core material, so there are: (1) It is not possible to ensure sufficient (2) The curvature of the bent portion cannot be kept constant, (3) Due to the above (1) and (2), there is deformation of the flexible base material near the bent portion, or disconnection of the conductor circuit. The problem

In particular, when flexible substrates are repeatedly bent or conductor circuits are formed from fine wiring patterns, these problems are significant.

[0011] In addition, undulations (waves) may be formed near the bending portion of the flexible substrate or the region where the rigid portion is formed. When the undulations are formed, cracks may occur in the undulation-formed portion of the base material, or the conductor circuit may be disconnected. damage

[0012] Moreover, in the case where the cover layer for protecting the conductor circuit provided on the flexible substrate is formed by a polyimide film with an adhesive, since the connection reliability and insulation reliability of the through hole may be reduced, Therefore, there is also a problem that special control of opening, desmear, plating conditions, etc. is required, and it is restricted in forming a combined structure with other materials.

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