Card-Edge PCB Abrasion Layer for Insulation Breakdown Prevention
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Solution Overview
Problem
In card edge type printed wiring boards based on metal plates, insulation breakdown and conduction failure occur due to the scraping of the electric insulation layer by connector terminals, leading to potential insulation and conduction failures.
Innovation Solution
A card edge type printed wiring board design that includes an abrasion resistance layer made of metal, spaced from the terminal portion's end and extending to the board edge, and a protection layer covering the insulation layer, preventing direct contact and mechanical damage from connector terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the terminal portion is provided to reach the edge of the board, then the electrical connectivity is improved, but insulation breakdown due to creeping discharge is likely to occur between the terminal portion and the base layer
Solution Approach 1:
An intermediary insulating layer is introduced between the terminal portion and the base layer edge. This insulating layer extends from the edge of the base layer to the terminal portion, preventing direct electrical contact and avoiding insulation breakdown while maintaining electrical connectivity functionality
Solution Approach 2:
The space between the terminal portion and base layer edge is segmented into distinct functional zones: the insulating layer occupies this space, creating clear separation between conductive elements and preventing creeping discharge paths
2Object-affected harmful factors
If the terminal portion terminates in the vicinity of the edge of the board, then insulation breakdown is avoided, but the electric insulation layer is exposed and likely to be scraped by connector terminal sliding contact
Solution Approach 1:
The insulating layer is pre-positioned to cover the exposed electric insulation layer between the terminal portion and base layer edge before connector installation. This preliminary protective action prevents scraping damage during subsequent connector sliding operations
Solution Approach 2:
The insulating layer acts as a cushioning protective layer that absorbs and distributes the mechanical stress from connector terminal sliding contact, preventing direct contact between the connector and the underlying electric insulation layer
3Stability of the object's composition
If a soft electric insulation layer is used, then stress from thermal expansion and contraction is alleviated, but the electric insulation layer is more susceptible to scraping by connector terminals
Solution Approach 1:
A composite protective structure is created by combining the soft electric insulation layer (for thermal stress resistance) with the insulating layer (for abrasion resistance). This composite arrangement allows each layer to perform its specialized function: the soft layer handles thermal expansion while the insulating layer provides mechanical protection against scraping
Data Source
AI summary
In a card edge type printed wiring board including a terminal portion provided to reach a vicinity of an edge of a base layer, an abrasion resistance layer made of metal is provided on a portion of an electric insulation layer between a board edge and an end portion of the terminal portion on a side of the board edge, and the abrasion resistance layer is spaced at an interval from the end portion of the terminal portion.