Flexible PCB Boundary Reinforcement for Crack Resistance
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Solution Overview
Problem
Flexible printed circuit boards with thin and light conductive wires face pattern cracks when subjected to repeated external forces, particularly at boundaries between conductive wire patterns, covering members, and external terminal pads, making them unsuitable for bendable or foldable electronic devices.
Innovation Solution
Incorporating a boundary reinforcing pattern that expands the first circuit pattern in the width direction based on virtual boundaries where the first and second circuit patterns meet, forming a combined structure with increased width to prevent cracks, and using a flexible copper clad laminate film with rigid areas for added durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If thin and light conductive wires are used in the flexible printed circuit board, then the board becomes thinner and lighter, but pattern cracks occur when repeated external forces are applied
Solution Approach 1:
The patent applies different properties to different parts of the circuit board by introducing a boundary reinforcing pattern specifically at the boundaries between conductive wire patterns and covering members or external terminal pads. This local reinforcement strategy strengthens only the vulnerable boundary regions while maintaining the overall thin and light structure of the flexible printed circuit board.
Solution Approach 2:
The boundary reinforcing pattern is formed in advance during the manufacturing process, before the flexible printed circuit board is assembled into the electronic device. This preliminary reinforcement structure is pre-established to prevent cracks from forming at critical boundaries when repeated external forces are applied during the device's usage lifecycle.
2Length of moving object
If thin and light conductive wires are used in the flexible printed circuit board, then the board becomes thinner and lighter, but the board requires greater durability to withstand repeated bending and folding
Solution Approach 1:
Instead of uniformly increasing the thickness or strength of the entire flexible printed circuit board, the patent applies local reinforcement only at the boundary regions between conductive wire patterns and covering members or external terminal pads. This approach maintains the overall thinness of the board while providing targeted strength enhancement where cracks are most likely to occur.
3Reliability
If a boundary reinforcing pattern is added to prevent cracks, then crack resistance is improved, but the device complexity increases
Solution Approach 1:
The boundary reinforcing pattern is strategically placed only at specific boundary regions where cracks are most likely to occur, rather than being applied uniformly across the entire circuit board. This localized approach minimizes the additional structural complexity while effectively addressing the crack resistance issue at critical locations.
Solution Approach 2:
The boundary reinforcing pattern is integrated into the existing manufacturing process and structure of the flexible printed circuit board. The reinforcing pattern is formed as part of the circuit board structure itself, merging the reinforcement function with the existing conductive wire pattern and covering member structure, thereby avoiding the need for separate additional components.
Data Source
AI summary
A flexible printed circuit board includes: a base film; a first circuit pattern disposed on an upper surface of the base film; a second circuit pattern disposed on a lower surface of the base film; and a boundary reinforcing pattern expanding the first circuit pattern in a width direction of the first circuit pattern based on a virtual boundary along which the first circuit pattern and the second circuit pattern meet each other in an overlay of the first circuit pattern and the second circuit pattern.