Printed Wiring Board Seed Layer Layout for Via Adhesion Reliability
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Solution Overview
Problem
Existing printed wiring boards face challenges in ensuring adequate adhesion between conductor layers and resin insulating layers, particularly due to insufficient thickness and distribution of the seed layer, leading to issues with connection reliability and signal propagation speed variations.
Innovation Solution
The printed wiring board design includes a seed layer with distinct thickness variations across its portions, with a thicker first portion on the resin insulating layer surface, a thinner second portion on the inner wall, and an even thinner third portion on the conductor layer exposure, enhancing adhesion and reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform thickness seed layer is formed on all surfaces, then the manufacturing process is simple, but the adhesion between conductor layers and resin insulating layers is insufficient
Solution Approach 1:
The seed layer is designed with different thicknesses in different regions: a first thickness on the resin insulating layer surface, a second thickness on the inner wall of the opening, and a third thickness on the conductor layer. This local differentiation optimizes adhesion where needed (thicker on resin surface) while maintaining electrical connectivity elsewhere, resolving the contradiction between adhesion reliability and manufacturing simplicity.
2Reliability
If the seed layer is made uniformly thick to ensure adhesion, then connection reliability improves, but stress concentration occurs and signal propagation speed varies
Solution Approach 1:
By making the seed layer thickness location-dependent (thicker on resin surface for adhesion, thinner in opening for stress reduction), the invention achieves both strong connection reliability and consistent signal propagation speed, eliminating the trade-off between these two properties.
Solution Approach 2:
The seed layer thickness parameter is varied across different spatial locations rather than maintained uniformly. This parameter change allows optimization of adhesion strength where contact with resin is needed while reducing stress concentration in the via region, thereby ensuring both connection reliability and signal propagation consistency.
3Reliability
If the seed layer thickness is increased throughout to improve adhesion, then connection reliability improves, but material usage and manufacturing complexity increase
Solution Approach 1:
The seed layer is applied with greater thickness only where adhesion is critical (on the resin insulating layer surface) rather than uniformly throughout. This localized thickening achieves the required connection reliability while minimizing overall material consumption compared to a uniformly thick seed layer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves connection reliability, reduces signal propagation delays, and enhances the overall stability and performance of the printed wiring board by optimizing the seed layer thickness distribution.
Implementation Method 1
an electrolytic plating layer formed on the seed layer
Data Source
AI summary
A printed wiring board includes a first conductor layer, a resin insulating layer formed on the first conductor layer, a second conductor layer formed on a surface of the insulating layer, and a via conductor formed in an opening formed in the insulating layer such that the via conductor is connecting the first and second conductor layers. The second conductor layer and via conductor include a seed layer and an electrolytic plating layer formed on the seed layer such that the seed layer has a first portion formed on the surface of the insulating layer, a second portion formed on an inner wall surface of the insulating layer in the opening, and a third portion formed on the first conductor layer exposed from the opening and that the first portion has a thickness that is greater than a thickness of the second portion and a thickness of the third portion.