PCB Terminal Corrosion Prevention via Layer Projection
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Solution Overview
Problem
Conventional printed circuit boards face challenges in preventing corrosion of terminal portions without increasing the thickness of the terminal cover layer, especially with the trend towards finer pitching and the need to reduce the thickness of the terminal cover layer.
Innovation Solution
A printed circuit board design featuring a conductor trace with a terminal portion thinner than the wiring portion, where the wiring cover layer projects above the terminal portion and the terminal cover layer is formed with specific projections and an insert portion to prevent chemical liquid infiltration, allowing the terminal cover layer to remain thin while preventing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the thickness of the terminal portion is reduced to enable finer pitching, then the productivity and adaptability are improved, but the reliability deteriorates due to increased corrosion risk
Solution Approach 1:
The patent applies local quality by creating a thickness difference between the terminal portion and wiring portion (difference not more than 2 μm), and by providing a terminal cover layer specifically at the terminal portion while maintaining a thin overall profile. This localized differentiation protects the vulnerable terminal area without requiring a uniformly thick cover layer, thus enabling finer pitching while maintaining corrosion resistance.
2Device complexity
If the terminal cover layer is made thinner to reduce device complexity, then the ease of manufacture is improved, but the reliability deteriorates due to chemical liquid infiltration and corrosion
Solution Approach 1:
The patent transitions from a single-dimensional thickness increase to a multi-dimensional protective structure. The terminal cover layer includes a first projection extending in the thickness direction and a second projection extending in the planar direction, creating a stepped configuration. This dimensional change allows the cover layer to provide comprehensive protection against chemical liquid infiltration from multiple directions while maintaining a thin overall profile.
Solution Approach 2:
The terminal cover layer is segmented into multiple functional portions: a base layer, a first projection (extending upward), and a second projection (extending laterally). This segmentation allows each portion to address specific protection needs - the base layer provides general coverage, the first projection protects against vertical infiltration, and the second projection protects against lateral infiltration - achieving reliable protection without increasing overall thickness.
3Ease of manufacture
If the terminal cover layer is made thinner to reduce manufacturing costs, then the ease of manufacture is improved, but the object-affected harmful factors increase due to corrosion and foreign matter infiltration
Solution Approach 1:
The patent changes the geometric parameters of the terminal cover layer by introducing projections with specific dimensional relationships. The first projection extends to a height that provides adequate protection, and the second projection extends laterally to seal the interface with the cover insulating layer. These parameter changes create an effective barrier against harmful factors while maintaining cost-effectiveness through a relatively thin overall structure.
Data Source
AI summary
A wiring cover layer is formed on a base insulating layer with a conductor trace sandwiched therebetween. A cover insulating layer is formed on the base insulating layer to cover the wiring cover layer. A terminal cover layer is formed to cover a terminal portion of the conductor trace. A projection of the wiring cover layer projects from an upper surface of the wiring portion to a position above the terminal portion. An end surface of the projection is positioned inward from an end of the cover insulating layer. An insert portion of the terminal cover layer is formed between an upper surface of the terminal portion and a lower surface of the end of the cover insulating layer. A projection of the terminal cover layer is formed between the upper surface of the terminal portion and a lower surface of the projection of the wiring cover layer.