Printed Wiring Board Seed Layer Adhesion and Stress Control
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Solution Overview
Problem
Current printed wiring boards face challenges in ensuring reliable electrical connections and data transmission between electronic components due to issues with conductor layer adhesion and surface roughness, which can lead to signal degradation and mechanical stress.
Innovation Solution
A printed wiring board design featuring a connection conductor layer with a seed layer and an electrolytic plating layer, where the seed layer consists of two layers with different widths, and via conductors that connect electrodes to the connection wiring, ensuring smooth inner wall surfaces and reduced stress propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer seed layer is used in the connection conductor layer, then the manufacturing process is simpler, but the adhesion between the conductor layer and resin insulating layer is insufficient and surface roughness is high
Solution Approach 1:
The seed layer is divided into two distinct layers: a first layer in contact with the resin insulating layer and a second layer on top of the first layer. This segmentation allows each layer to perform its specific function - the first layer provides adhesion to the resin while the second layer provides a smooth surface for the electrolytic plating layer, thereby resolving the contradiction between adhesion and surface smoothness without excessive complexity
Solution Approach 2:
The connection conductor layer is constructed as a composite structure with multiple materials: the first layer (Cu-Ni-P alloy), the second layer (Cu-Ni alloy), and the electrolytic plating layer (Cu). This composite structure combines the adhesive properties of the first layer with the surface-smoothing properties of the second layer, achieving both good adhesion and low surface roughness
2Reliability
If the connection conductor layer has uniform width throughout, then the manufacturing process is simpler, but stress propagates easily causing connection reliability issues
Solution Approach 1:
The connection conductor layer is designed with asymmetric width distribution: the first layer has a larger width than the second layer. This asymmetric geometry creates a stress-diffusing structure where the wider first layer can better distribute mechanical stress, preventing stress concentration and improving connection reliability while maintaining manufacturing feasibility
3Reliability
If the inner wall surface of via conductors is rough, then the electrolytic plating fills the via better, but signal degradation occurs due to increased surface area and resistance
Solution Approach 1:
The inner wall surface of the via conductors is designed with local quality variation: the lower portion (in contact with the first layer) has a rougher surface to ensure good electrolytic plating fill and adhesion, while the upper portion (exposed at the surface) has a smoother surface to reduce signal degradation. This localized differentiation resolves the contradiction between plating fill and signal quality
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 enhances adhesion, reduces signal loss, and prevents mechanical stress, allowing for high-speed and reliable data transmission between electronic components.
Implementation Method 1
a connection conductor layer which includes a connection wiring, and comprising a seed layer and an electrolytic plating layer formed on the seed layer
Data Source
AI summary
A printed wiring board includes a first insulating layer, a connection conductor layer including wiring, a second insulating layer covering the connection conductor layer, a conductor layer including first and second electrodes such that the first electrode mounts a first electronic component and the second electrode mounts a second electronic component, and via conductors including first and second via conductors. The first via conductor connects the first electrode and wiring. The second via conductor connects the second electrode and wiring. The conductor layer includes a seed layer and an electrolytic plating layer. The seed layer includes a first layer formed on the first insulating layer and a second layer formed on the first layer, a width of the first layer is larger than a width of the second layer, and a width of the electrolytic plating layer is larger than the width of the first layer of the seed layer.