Wiring Circuit Board Via Oxide Layout for Low-Resistance Support Contact
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Solution Overview
Problem
Existing wiring circuit boards face challenges in achieving low electrical resistance between the conductive layer and the metal supporting board due to the removal of the first metal layer, which exposes the underlying metal layer to etching, leading to increased resistance.
Innovation Solution
The implementation of a wiring circuit board design where the first metal thin film includes an oxide coating on contact surfaces, with selective removal in the through hole to maintain electrical connection while protecting the underlying metal layer, and the use of additional metal thin films to reduce resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first metal layer is removed by etching to achieve direct contact between the via and metal supporting board, then electrical resistance is reduced, but the metal supporting board becomes exposed to etching damage
Solution Approach 1:
The patent applies local quality by creating a non-uniform oxide coating thickness on the first metal layer. The oxide coating is thicker at the periphery of the through hole to protect the metal supporting board from etching damage, while being thinner or absent at the center to allow direct electrical contact between the via and metal supporting board. This spatial variation in oxide coating thickness resolves the contradiction by providing different functions in different locations.
Solution Approach 2:
The oxide coating is segmented into different thickness regions - a peripheral region with thicker oxide coating for protection and a central region with thinner or no oxide coating for electrical contact. This segmentation allows the first metal layer to simultaneously serve as both a protective barrier and an electrical conductor, resolving the contradiction between protection and conductivity.
2Reliability
If the first metal layer is completely removed to reduce electrical resistance, then conductivity improves, but protection of the underlying metal layer is lost
Solution Approach 1:
The oxide coating thickness is varied locally across the first metal layer surface. At the periphery, the thicker oxide coating provides corrosion and environmental protection to the metal supporting board. At the center, the thinner or absent oxide coating ensures low electrical resistance contact. This local differentiation resolves the contradiction between protection and conductivity.
Solution Approach 2:
The oxide coating acts as an intermediary layer with graded thickness. It mediates between the need for protection (thicker oxide) and the need for conductivity (thinner oxide), allowing both functions to coexist on the same first metal layer surface through spatial variation in thickness.
Data Source
AI summary
A wiring circuit board includes a metal supporting layer, a first metal thin film, an insulating layer including a through hole, a second metal thin film disposed on the first metal thin film in the through hole, and a conductive pattern electrically connected to the metal supporting layer through the first metal thin film and the second metal thin film in the through hole. The first metal thin film includes an oxide coating at least on a contact surface in contact with the insulating layer. In the central part of the through hole, the oxide coating has a thickness of 0 or a thickness smaller than a thickness of the oxide coating on the contact surface.