Flexible Printed Circuit Opening Structure for Upwarp Stress Relief
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Solution Overview
Problem
Flexible printed circuits experience stress during bending, leading to a higher risk of upwarping, which complicates assembly and transportation due to the squeezing of film layers, affecting surface flatness and production yield.
Innovation Solution
Incorporating a bent region with an opening structure between the circuit bonding and flat regions, allowing stress to be released through the openings, reducing the thickness and number of line layers in the bent region, and using ink layers to protect the line layers, thereby minimizing the upwarp risk and improving surface flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible printed circuit is bent to enable flexibility and routing, then the circuit can be adapted to different spatial configurations, but stress accumulates in the bent region causing upwarping and reducing manufacturing precision
Solution Approach 1:
The bent region is segmented into multiple layers with different numbers of line layers, creating a stepped structure that distributes stress across different zones. This segmentation allows the circuit to bend while maintaining overall flatness by controlling where thickness variations occur.
Solution Approach 2:
Different regions of the flexible printed circuit are given different structural qualities - the bent region has reduced line layer quantity and adjusted thickness compared to flat regions. This local differentiation enables the bent area to accommodate stress while the overall circuit maintains manufacturing precision and surface flatness.
2Reliability
If multiple film layers are stacked in the bent region to maintain circuit functionality, then signal transmission is preserved, but the increased thickness exacerbates upwarping due to stress
Solution Approach 1:
The number of line layers is dynamically adjusted based on the functional requirements of different regions. The bent region has fewer line layers than flat regions, creating a thickness gradient that reduces stress-induced upwarping while preserving necessary signal transmission pathways.
Solution Approach 2:
The thickness parameter of the flexible printed circuit is changed in the bent region by reducing the number of line layers. This parameter modification directly addresses the upwarping issue caused by stress accumulation, while circuit functionality is maintained through selective layer retention.
3Reliability
If the line layers are made thicker or more numerous to ensure signal integrity, then electrical performance improves, but the bending process becomes more difficult and success rate decreases
Solution Approach 1:
The line layers are segmented into different quantities across different regions. The bent region contains fewer line layers compared to flat regions, reducing the overall thickness and making the bending process easier while preserving signal transmission integrity through selective layer placement.
4Device complexity
If the flexible printed circuit is designed with uniform thickness throughout, then manufacturing is simplified, but the bent region cannot effectively release stress leading to lower production yield
Solution Approach 1:
The flexible printed circuit employs local quality differentiation where the bent region has a different number of line layers and thus different thickness compared to flat regions. This localized structural variation enables effective stress release during bending, improving production yield while maintaining overall manufacturing simplicity.
Data Source
AI summary
Disclosed are a flexible printed circuit, a flexible apparatus and a display device. The flexible printed circuit includes: a circuit bonding region, a flat and straight region, and a bent region located between the circuit bonding region and the flat and straight region; where the bent region has an opening structure.