PCB Conductor Trace with Low-Magnetism Metal Cover Layer
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Solution Overview
Problem
Conventional printed circuit boards experience high transmission loss of electrical signals in the high frequency band and are prone to corrosion, particularly at the boundary between the terminal and wiring portions of the conductor trace.
Innovation Solution
A printed circuit board design featuring a conductor trace with a metal cover layer having magnetism lower than nickel, where the metal cover layer contacts the wiring portion and extends from the terminal portion, and a second insulating layer that covers part of the metal cover layer, preventing corrosion by eliminating ferromagnetic layers between the wiring and insulating layers, thereby reducing signal loss and enhancing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal film with high magnetism (such as nickel) is formed on the conductor trace to improve adhesion and prevent corrosion, then corrosion resistance is improved, but transmission loss of electrical signals in the high frequency band increases
Solution Approach 1:
The metal cover layer is segmented into two parts: a first metal cover layer with low magnetism (such as copper or aluminum) that contacts the conductor trace, and a second metal cover layer with high magnetism (such as nickel) that covers the first metal cover layer. This segmentation allows the low-magnetism layer to reduce transmission loss while the high-magnetism layer provides corrosion resistance and adhesion, resolving the contradiction between signal transmission quality and corrosion protection.
Solution Approach 2:
The first metal cover layer with low magnetism acts as an intermediary between the conductor trace and the second metal cover layer with high magnetism. This intermediary layer prevents direct contact between the high-magnetism nickel layer and the conductor trace, thereby reducing transmission loss while still providing corrosion resistance through the nickel layer's protection of the underlying structure.
2Reliability
If a metal cover layer is formed to cover the entire conductor trace including terminal portion to prevent corrosion, then corrosion resistance is improved, but manufacturing complexity increases due to additional plating steps
Solution Approach 1:
The metal cover layer is divided into two functional segments: the first metal cover layer formed by electroless nickel plating that covers the conductor trace, and the second metal cover layer formed by electroplating that covers the first metal cover layer and extends to the terminal portion. This segmentation enables different plating methods to be applied to different regions, simplifying the overall manufacturing process while maintaining comprehensive corrosion protection.
Solution Approach 2:
The first metal cover layer with low magnetism is formed in advance by electroless nickel plating before the second metal cover layer with high magnetism is applied. This preliminary action creates a base layer that provides initial corrosion resistance and serves as a foundation for the subsequent high-magnetism layer, reducing the need for complex multi-step plating processes.
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 solution effectively reduces transmission loss in the high frequency band and prevents corrosion at the terminal and wiring portion boundaries, improving signal integrity and durability.
Implementation Method 1
the first metal cover layer has magnetism lower than magnetism of nickel
Implementation Method 2
a layer having the magnetism as high as or higher than the magnetism of nickel is not present between the wiring portion and the second insulating layer
Implementation Method 3
adhesion between the conductor trace and the cover layer is improved by formation of the metal film on the surface of the conductor trace
Data Source
AI summary
A conductor trace is formed on a base insulating layer. The conductor trace includes two terminal portions and one wiring portion. The wiring portion is formed to connect the two terminal portions to each other and extend from each terminal portion. A metal cover layer is formed to cover the terminal portion and the wiring portion of the conductor trace and continuously extend from a surface of the terminal portion to a surface of the wiring portion. The metal cover layer is made of metal having magnetism lower than magnetism of nickel, and is made of gold, for example. A cover insulating layer is formed on the base insulating layer to cover a portion, of the metal cover layer formed on the conductor trace, covering the wiring portion and not to cover a portion of the metal cover layer covering the terminal portion.