Printed Wiring Board Non-Uniform Conductor Thickness
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Solution Overview
Problem
Existing printed wiring boards face challenges in maintaining insulation reliability and reducing thickness due to differences in conductor thickness affecting stress distribution and via conductor connectivity, as described in Japanese Patent Laid-Open Publication No. 2004-319994.
Innovation Solution
A printed wiring board design featuring a conductor layer with a first conductor part of greater thickness than a second conductor part, where the second conductor part surrounds the first, and a resin insulating layer with a via opening connecting the two, ensuring high insulation reliability and reduced board thickness through strategic thickness distribution and via conductor placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a via hole is formed from electrolytic plating with uniform conductor thickness, then the manufacturing process is simple, but the stress distribution is uneven and insulation reliability deteriorates
Solution Approach 1:
The patent applies local quality by creating a conductor circuit with non-uniform thickness: a first conductor part with greater thickness and a second conductor part with lesser thickness. The via conductor connects to the thicker first conductor part, which provides better stress distribution and enhanced insulation reliability at the via connection point, while the thinner second conductor part maintains overall circuit functionality.
2Reliability
If the conductor layer thickness is increased to improve connection reliability, then the insulation reliability improves, but the overall board thickness increases
Solution Approach 1:
The patent implements local quality enhancement by concentrating the increased conductor thickness specifically at the first conductor part where the via conductor connects. This localized thickening improves connection reliability and stress distribution only where needed, while the second conductor part maintains a thinner profile, thereby preventing overall board thickness increase.
3Ease of manufacture
If the via opening position is offset from the conductor surface, then laser drilling is easier, but the via conductor connection to the conductor circuit becomes less reliable
Solution Approach 1:
The patent resolves this contradiction by creating a localized thickened first conductor part directly beneath the via opening. This allows the via opening to be positioned optimally for laser drilling while the underlying thicker conductor part ensures reliable via conductor connection and electrical connectivity, effectively decoupling the via opening position from the conductor surface position.
Data Source
AI summary
A printed wiring board includes a conductor layer including a conductor circuit, a resin insulating layer formed on the conductor layer and having a via opening reaching to the conductor circuit of the conductor layer, and a via conductor formed in the via opening of the resin insulating layer such that the via conductor is connecting to the conductor circuit of the conductor layer. The conductor circuit of the conductor layer has a first conductor portion and a second conductor portion integrally formed such that the first conductor portion is connected to the via opening of the resin insulating layer, that the second conductor portion is surrounding the first conductor portion and that the first conductor portion has a thickness which is greater than a thickness of the second conductor portion.