Flexible Substrate Solder Joint Layout to Prevent Wire Breaking
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Solution Overview
Problem
The manufacture tolerance of coverlay films is large, leading to insufficient shifting of the end portion of solder joint portions from the bending part of flexible substrates, resulting in wire breaking.
Innovation Solution
A through hole is provided through the flexible substrate to connect GND patterns, with the end portion of the solder joint positioned corresponding to the through hole, reducing the manufacture tolerance and stress concentration, thereby preventing wire breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coverlay film is used to shift the end portion of the solder joint, then wire breaking is prevented, but manufacturing precision deteriorates due to large tolerance of the coverlay film
Solution Approach 1:
The patent introduces a coverlay film as an intermediary layer between the flexible substrate and the external environment. This coverlay film includes a recess portion that receives the end portion of the solder joint, allowing the solder joint end to be positioned away from the bending part of the flexible substrate. The coverlay film thus mediates the positioning function, preventing wire breaking while maintaining manufacturing feasibility.
Solution Approach 2:
The coverlay film is prepared in advance with a recess portion formed at the appropriate position before the soldering process. This preliminary preparation ensures that when the solder joint is formed, its end portion can be naturally received and positioned in the recess, shifting it from the bending part without requiring high-precision positioning during the soldering process itself.
2Reliability
If the end portion of the solder joint is positioned away from the bending part, then wire breaking is prevented, but device complexity increases due to additional coverlay structure
Solution Approach 1:
The coverlay film serves multiple functions simultaneously: it provides insulation for the conductive pattern, protects the solder joint, and creates the recess portion for positioning the solder joint end. By combining these functions into a single component, the patent avoids the need for additional separate structures, thus preventing excessive increase in device complexity while still achieving wire breaking prevention.
Data Source
AI summary
Solder (12) joins together a second conductive pattern (4) of a flexible substrate (1) and a third conductive pattern (7) of a print substrate (6) and joins together a second GND pattern (5) of the flexible substrate (1) and a third GND pattern (8) of the print substrate (6). A through hole (11) passes through the flexible substrate (1) and connects the first and second GND patterns (3,5) together. In an extension direction in which the second conductive pattern (4) extends, an end portion of a solder joint portion between the second conductive pattern (4) and the third conductive pattern (7) is in a position corresponding to the through hole (11) and is shifted from an end portion of the through hole (11).