Printed Wiring Boards

The printed wiring board achieves fine pitching and reliability under heat cycles by strategically placing a through-hole plating layer on the inner and side surfaces of the wirings, addressing the challenges of existing flexible printed wiring boards.

JP7649703B2Active Publication Date: 2025-03-21SUMITOMO ELECTRIC PRINTED CIRCUITS INC +1
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Patent Information

Application Number
JP2021104159
Authority / Receiving Office
JP · JP
Patent Type
Patents
Current Assignee / Owner
Priority Date
2021-06-10
Filing Date
2021-06-23
Publication Date
2025-03-21
Estimated Expiration
2041-06-23

AI Technical Summary

Technical Problem

Existing flexible printed wiring boards face challenges in achieving fine pitches due to the necessity of forming thick masks, which increases the spacing between conductive patterns, and there are concerns about reliability when subjected to heat cycles if the plating layer is not adequately distributed.

Method used

The printed wiring board design includes a base film with through holes, first and second wirings on opposite surfaces, and a through-hole plating layer that is electrically connected to the wirings. The plating layer is strategically disposed on the inner wall surface of the through holes and on the side surfaces of the wirings, but not on the top surfaces of the second wiring, allowing for fine pitching while maintaining reliability under heat cycles.

Benefits of technology

This configuration enables fine pitching of the second wiring while ensuring reliability when subjected to heat cycles, as the strategic placement of the plating layer enhances electrical connectivity and reduces the likelihood of peeling during thermal stress.

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Abstract

To provide a printed circuit board which can be finely pitched while securing reliability when receiving a heat cycle.SOLUTION: A printed circuit board comprises: a base film; first wiring and second wiring; and a through-hole plating layer electrically connected to the first wiring and second wiring. The base film includes: a first main surface; and a second main surface which is the opposite surface to the first main surface. In the base film, a penetration hole penetrating the base film along a thickness direction is formed. The first wiring is arranged on the first main surface. The second wiring is arranged on the second main surface. The through-hole plating layer is arranged on an inner wall surface of the penetration hole, on an upper surface of the first wiring in the circumference of the penetration hole, on a side surface of the first wiring in the circumference of the penetration hole and a side surface of the second wiring in the circumference of the penetration hole.SELECTED DRAWING: Figure 1A
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