Wiring Substrate Surface Layout for Adhesion and High-Frequency Signals
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Solution Overview
Problem
Existing wiring substrates face challenges in achieving both good high-frequency transmission characteristics and reliable adhesion between conductor pads and insulating layers, with surface roughness differences between conductor pads and wiring patterns leading to potential peeling issues and infiltration of liquids.
Innovation Solution
A wiring substrate design where the first conductor layer includes roughened conductor pads with a higher surface roughness than wiring patterns, covered by a coating film that improves adhesion with the insulating layer, while the wiring patterns maintain a lower surface roughness to prevent peeling and ensure high-frequency transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of conductor pads is roughened to improve adhesion with the insulating layer, then adhesion strength is improved, but high-frequency transmission characteristics deteriorate due to increased surface roughness
Solution Approach 1:
The patent applies different surface roughness treatments to different regions of the conductor layer: conductor pads are roughened to improve adhesion, while wiring patterns maintain smooth surfaces for high-frequency transmission. This local differentiation resolves the contradiction by optimizing each region for its specific function.
2Strength
If a coating film is formed on the conductor pad surface to improve adhesion, then bonding with the insulating layer is enhanced, but the conductor pad surface roughness increases which may affect transmission characteristics
Solution Approach 1:
The coating film is selectively formed only on conductor pads through targeted roughening, while wiring patterns remain smooth. This localized approach allows the coating film to enhance adhesion where needed without compromising the transmission characteristics of wiring patterns.
Solution Approach 2:
The coating film acts as an intermediary layer between the conductor pad and insulating layer, providing improved adhesion. The film is strategically placed only where mechanical bonding is critical, rather than uniformly across all conductor surfaces.
3Strength
If the entire conductor layer surface is roughened to maximize adhesion, then adhesion between conductor and insulating layer is improved, but peeling resistance decreases due to uniform roughness across all areas
Solution Approach 1:
The patent implements selective roughening where only conductor pads are roughened and coated, while wiring patterns maintain smooth surfaces. This creates functional zones with different surface properties, improving overall peeling resistance by preventing uniform stress distribution that leads to delamination.
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
The design enhances adhesion between conductor pads and insulating layers, prevents peeling, and maintains high-frequency transmission characteristics by controlling surface roughness and using a coating film to improve contact area and bonding.
Implementation Method 1
a coating film that improves adhesion between the first conductor layer and the insulating layer
Implementation Method 2
the conductor pads have roughened surfaces facing the insulating layer and having a first surface roughness that is higher than a second surface roughness of the surfaces of the wiring patterns
Data Source
AI summary
A wiring substrate includes a first conductor layer, an insulating layer on the first layer such that the insulating layer is covering the first layer, a second conductor layer on the insulating layer such that the insulating layer is formed between the first and second layers, the connection conductors penetrating through the insulating layer and connecting the first and second layers, and a coating film formed at least partially on surface of the first layer such that the film improves adhesion between the first layer and insulating layer. The first layer includes pads and wiring patterns such that the pads are in contact with the connection conductors and that the patterns have surfaces facing the insulating layer and covered by the film, and the pads have roughened surfaces facing the insulating layer and having first surface roughness that is higher than second surface roughness of the surfaces of the patterns.