Curved Conductor Post for Printed Wiring Board Stress Relief
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Solution Overview
Problem
Conventional printed wiring boards experience stress concentration and reliability issues due to abrupt changes in the cross-sectional shape of conductor posts, leading to potential peeling or cracking when connected to other boards with different thermal expansion coefficients.
Innovation Solution
The printed wiring board features a conductor post with a curved side surface that increases in diameter towards the wiring conductor layer, eliminating acute-angled corners and enhancing the connection reliability by dispersing stress, and is embedded in a resin insulating layer that covers the conductor post's side surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductor post with abrupt cross-sectional changes is used, then manufacturing is simpler, but stress concentration occurs leading to peeling and cracking
Solution Approach 1:
The conductor post is designed with a curved side surface instead of abrupt angular transitions. The curved surface gradually changes the cross-sectional area from the wiring conductor layer toward the end surface, eliminating stress concentration points and preventing peeling or cracking at corners.
2Reliability
If the conductor post has a curved side surface, then stress concentration is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies particular parameter ranges for the curved side surface, including the curvature radius and the gradual change in cross-sectional area. By defining these parameters within specific ranges, the design balances stress reduction with manufacturability, avoiding excessive precision requirements while maintaining reliability.
Data Source
AI summary
A printed wiring board includes a resin insulating layer, a wiring conductor layer embedded in the insulating layer such that the conductor layer has a first surface exposed on a first surface side of the insulating layer, and a conductor post formed on a second surface of the conductor layer on the opposite side with respect to the first surface such that the conductor post has a side surface covered by the insulating layer. The conductor post has an end surface on the opposite with respect to the conductor layer such that the end surface of the conductor post is exposed on a second surface side of the insulating layer, and the conductor post has an end portion on a wiring conductor layer side such that the side surface in the end portion is a curved side surface which is bending outward increasingly toward from the conductor layer.