Wiring Board Resist Pattern Thickness Variation
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Solution Overview
Problem
Conventional build-up wiring boards face defects in peeling due to high aspect ratio resist patterns with narrow pitches, leading to mechanical distortion and increased side surface dimensions, which complicates the removal process.
Innovation Solution
A wiring board design with alternating wide and narrow portions, where the narrow portions are formed thinner than the wide portions, using copper plating with specific electrolyte solutions to reduce mechanical distortion and facilitate easier peeling by adjusting the concentration ratio of copper sulfate and sulfuric acid, and forming insulating layers to cover the wiring layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the thickness of the resist pattern is made uniform across all wiring patterns, then the manufacturing process is simplified, but the aspect ratio becomes high at narrow wiring patterns causing peeling defects
Solution Approach 1:
The patent applies local quality by making the resist pattern thickness vary according to the wiring pattern width. Specifically, the resist pattern thickness is set to be greater at narrow wiring patterns than at wide wiring patterns, creating different local properties where needed. This resolves the contradiction by maintaining uniform manufacturing processes while achieving appropriate aspect ratios at different locations to prevent peeling defects.
2Reliability
If the resist pattern thickness is increased to reduce peeling defects, then peeling reliability improves, but mechanical distortion increases due to volume expansion
Solution Approach 1:
The patent implements local quality by differentiating resist pattern thickness based on location. Narrow wiring patterns receive thicker resist patterns to ensure adequate peeling resistance, while wide wiring patterns have thinner resist patterns to minimize mechanical distortion from volume expansion. This localized approach allows each region to have optimal thickness for its specific requirements.
3Productivity
If the pitch of narrow wiring patterns is reduced to increase circuit density, then productivity improves, but the aspect ratio increases causing peeling defects
Solution Approach 1:
The patent applies local quality by adjusting resist pattern thickness according to the local pitch and width of wiring patterns. In regions with narrow pitch and high circuit density, the resist pattern thickness is increased to compensate for the higher aspect ratio, ensuring adequate peeling resistance is maintained even as circuit density increases.
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 significantly reduces defects in peeling by decreasing the side surface contact dimension of the resist pattern, ensuring reliable peeling even at high aspect ratios, particularly in narrow line/space portions, thereby enhancing the manufacturing process.
Implementation Method 1
depositing copper with a certain thickness in each of the open portions by electroplating
Implementation Method 2
The resist pattern is peeled by having peeling solution containing sodium hydroxide or the like absorbed by the resist pattern to be swollen
Data Source
AI summary
A wiring board includes an insulating layer; and a wiring layer embedded in the insulating layer at one surface side of the insulating layer, one surface of the wiring layer being exposed from one surface of the insulating layer, the wiring layer including a first portion and a second portion whose width is wider than that of the first portion, one surface of the first portion and one surface of the second portion being flush with each other, and the first portion being thinner than the second portion.