Multilayer Substrate Bending Layout to Prevent Metal Foil Breakage
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Solution Overview
Problem
Conventional multilayer substrates, such as flexible printed circuit boards, suffer from breakage of conductive materials when bent due to the alignment of bending lines and the orientation of metal foil layers.
Innovation Solution
A multilayer substrate design with specific bending regions and metal foil layer orientations that reduce the angles between the foil layers and the bending lines, minimizing tensile stress and surface roughness to prevent breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the flexible printed circuit board is bent along conventional bending lines, then the board can achieve desired flexibility and routing, but the conductive material inside breaks due to tensile stress
Solution Approach 1:
The patent applies local quality by making the insulating layer thicker specifically in the bending regions compared to non-bending regions. This localized structural modification provides enhanced protection to the conductive material only where bending stress occurs, while maintaining the original thin-profile design in areas where flexibility is not required. The different thickness regions create optimal mechanical protection exactly where needed.
Solution Approach 2:
The patent implements beforehand cushioning by pre-positioning the thicker insulating layer portions in the bending regions before any bending occurs. This pre-established protective structure acts as a cushion that absorbs and distributes the tensile stress during bending operations, preventing the conductive material from experiencing direct stress concentration that would cause breakage.
2Ease of manufacture
If the metal foil layer is oriented parallel to the bending line, then the bending process is simpler, but the metal foil layer experiences maximum tensile stress and breaks
Solution Approach 1:
The patent applies asymmetry by intentionally creating an asymmetric orientation relationship between the metal foil layer and the bending line. Instead of aligning them parallel (symmetric configuration), the metal foil layer is positioned at a specific angle that is not parallel to the bending line. This asymmetric arrangement redistributes the stress distribution during bending, preventing concentration of tensile stress along the entire length of the metal foil layer and thereby reducing breakage risk.
3Reliability
If a single thick insulating layer is used throughout, then all regions are protected equally, but the overall device size and weight increase
Solution Approach 1:
The patent applies local quality by making the insulating layer thicker specifically in the bending regions compared to non-bending regions. This localized structural modification provides enhanced protection to the conductive material only where bending stress occurs, while maintaining the original thin-profile design in areas where flexibility is not required. The different thickness regions create optimal mechanical protection exactly where needed.
Solution Approach 2:
The patent implements segmentation by dividing the insulating layer into distinct thickness zones: thicker portions located in bending regions and thinner portions in non-bending regions. This segmented structure allows each region to have the appropriate thickness for its specific functional requirements, optimizing both protection and weight characteristics.
Data Source
AI summary
In a first region, a multilayer body is bent along a first bending line such that a first main surface is located farther on an outer peripheral side than a second main surface. In a second region, the multilayer body is bent along a second bending line such that the first main surface is located farther on an inner peripheral side than the second main surface. In the first region, a first metal foil layer is located farther on an outer peripheral side than a center of the multilayer body. In the second region, a second metal foil layer is located farther on the outer peripheral side than the center of the multilayer body. In the second region, a distance between the second metal foil layer and the second main surface is shorter than a distance between the second metal foil layer and the first main surface.