Flexible Printed Circuit Board Reinforcement Thickness Gradient
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Solution Overview
Problem
Flexible printed circuit boards reinforced with a reinforcement member are prone to fractures due to stress concentration at the boundary between laminated and non-laminated areas, exacerbated by size reduction and smaller bending radii in electronic devices.
Innovation Solution
A flexible printed circuit board design where the reinforcement member's thickness increases stepwise or gradually toward the terminal connecting area, dispersing stress and preventing fractures, with the reinforcement member composed of multiple laminated layers and a coverlay that does not overlap with the reinforcement layers' edges, enhancing stress dispersion and reducing the risk of peeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a reinforcement member is laminated on the base film to prevent bending or warpage, then the structural stability is improved, but stress concentration occurs at the boundary between laminated and non-laminated areas causing fracture
Solution Approach 1:
The reinforcement member's thickness is varied locally: it is thicker at the terminal connecting area where stress concentration occurs, and thinner at other areas. This local variation in thickness provides targeted reinforcement at the fracture-prone boundary while maintaining overall flexibility, directly resolving the contradiction between structural stability and fracture resistance.
Solution Approach 2:
The thickness parameter of the reinforcement member is changed to resolve the contradiction. By increasing the thickness at the terminal connecting area, the reinforcement member provides greater structural support and stress distribution capability where needed, preventing fracture while maintaining stability throughout the circuit board.
2Volume of moving object
If the size of electronic devices is reduced, then the compactness is improved, but the bending radius becomes smaller increasing the risk of fracture
Solution Approach 1:
The reinforcement member provides localized reinforcement at the terminal connecting area, allowing the overall device size to be reduced while maintaining fracture resistance at critical locations. The non-uniform thickness distribution ensures that strength is concentrated where needed rather than uniformly distributed throughout the entire circuit board.
Solution Approach 2:
The reinforcement member is segmented into different thickness zones: a thicker portion at the terminal connecting area and a thinner portion at other areas. This segmentation allows the circuit board to achieve compact dimensions while maintaining adequate strength at the fracture-prone terminal area through the thicker reinforcement section.
3Strength
If the thickness of the reinforcement member is increased to prevent fracture, then the fracture resistance is improved, but the flexibility of the circuit board is reduced
Solution Approach 1:
The reinforcement member's thickness is optimized locally rather than uniformly throughout. The thicker portion is positioned only at the terminal connecting area where fracture resistance is critical, while other areas maintain thinner reinforcement to preserve flexibility. This local differentiation resolves the contradiction between strength and flexibility.
Solution Approach 2:
The thickness parameter of the reinforcement member is varied to balance fracture resistance and flexibility. By changing the thickness from a uniform value to a gradient distribution (thicker at terminals, thinner elsewhere), the circuit board achieves adequate fracture protection at critical points while maintaining overall flexibility for bending and routing.
Data Source
AI summary
A flexible printed circuit board according to one aspect of the present invention includes a base film having an insulating property and a conductive pattern laminated on one surface of the base film, and has a terminal connecting area toward one end edge of the conductive pattern, the flexible printed circuit board including a reinforcement member laminated on another surface of the base film and situated opposite at least the terminal connecting area, wherein a thickness of the reinforcement member increases toward the one end edge in a stepwise or gradual manner.