Printed Wiring Board Metal Post Unevenness for Thermal Stress
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Solution Overview
Problem
Existing printed wiring boards face challenges in maintaining connection reliability and insulation resistance due to stress-induced peeling and migration issues, particularly with metal posts that protrude from the resin insulating layer, which can lead to cracks and decreased reliability under thermal cycles.
Innovation Solution
A printed wiring board design featuring metal posts with a protruding portion and an embedded portion within the resin insulating layer, where the side surfaces exhibit distinct unevenness, with the embedded portion's unevenness being larger, enhancing connection reliability and reducing stress transmission, and a manufacturing method that forms these features to prevent peeling and migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If metal posts protrude from the resin insulating layer to enable component mounting, then ease of operation is improved, but stress concentration and peeling occur under thermal cycles reducing reliability
Solution Approach 1:
The metal post is divided into three distinct portions: a protruding portion for component mounting, an embedded portion within the resin insulating layer for structural support, and a buried portion for electrical connection. This segmentation allows each portion to be optimized for its specific function, reducing stress concentration at interfaces and preventing peeling under thermal cycles while maintaining ease of component mounting.
2Reliability
If the side surface of the metal post is roughened to prevent peeling, then reliability is improved, but manufacturing complexity increases
Solution Approach 1:
Different surface roughness characteristics are applied to different portions of the metal post: the embedded portion has a roughened side surface to enhance adhesion with the resin insulating layer, while the protruding portion maintains a smoother surface for component mounting. This localized differentiation improves reliability through enhanced adhesion where needed without unnecessarily complicating the overall manufacturing process.
3Ease of operation
If the protruding portion extends onto the resin insulating layer to increase mounting area, then ease of operation is improved, but migration and short circuit risks increase reducing reliability
Solution Approach 1:
The metal post structure employs asymmetric design where the protruding portion is positioned and dimensioned to provide adequate component mounting area while maintaining a clear separation from the resin insulating layer surface. The embedded portion provides lateral support without extending onto the resin surface, creating an asymmetric configuration that balances mounting requirements with insulation reliability, preventing migration and short circuit risks.
Data Source
AI summary
A printed wiring board includes a resin insulating layer, a metal post formed in the insulating layer and protruding from first surface of the insulating layer, a conductor layer formed on second surface of the insulating layer, and a via conductor penetrating through the insulating layer and connecting the metal post and conductor layer. The metal post has a protruding portion protruding from the first surface of the insulating layer and an embedded portion connected to the protruding portion and embedded in the insulating layer such that the protruding portion does not extend onto the insulating layer, and the metal post has upper and side surfaces such that the side surface has unevenness including a first unevenness on side surface of the protruding portion and a second unevenness formed on side surface of the embedded portion and having a size that is larger than a size of the first unevenness.