Stretchable Wiring Layout With Local Protection Against Stress Cracking
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Solution Overview
Problem
Conventional stretchable devices are prone to short circuits and damage due to exposure of wiring to water or foreign substances, and experience performance degradation such as increased resistance when expanded and contracted.
Innovation Solution
A stretchable device design featuring a first substrate with stretchability, a first wiring on the substrate, a second substrate facing the first substrate, a second wiring electrically connected to the first wiring, and a first protective layer covering part of the first wiring, with the protective layer overlapping the substrate but separated from the wiring region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective layer covers all exposed wiring regions, then protection against short circuits and corrosion is improved, but stress concentration and damage risk increase during expansion and contraction
Solution Approach 1:
The protective layer is selectively applied only in non-overlapping regions where the first substrate does not overlap with the second substrate, rather than covering the entire wiring area. This localized protection approach provides corrosion and short-circuit prevention in exposed areas while avoiding stress concentration in the overlapping region where the wiring is already protected by the sandwich structure.
Solution Approach 2:
The protective layer is divided into two distinct regions: a first protective layer in the non-overlapping region and a second protective layer in the overlapping region. This segmentation allows different protection strategies to be applied to different areas - the first protective layer prevents exposure to external elements, while the second protective layer provides additional protection where substrates overlap, together preventing short circuits without causing stress concentration.
2Object-affected harmful factors
If the protective layer is provided in all exposed portions, then wiring protection is improved, but breakage risk increases at the boundary between wiring region and protective layer overlapping region
Solution Approach 1:
The protective layer configuration is optimized for local conditions: in non-overlapping regions, the first protective layer prevents water and foreign substance exposure; in overlapping regions, the second protective layer provides additional protection. This localized approach ensures comprehensive protection against harmful factors while avoiding the creation of weak boundaries that could lead to breakage during device expansion and contraction.
Solution Approach 2:
The second protective layer is provided in advance in the overlapping region where the first substrate and second substrate overlap, before any potential damage can occur. This pre-protection measures ensures that the wiring is protected from both external elements and internal stress concentrations, preventing breakage before it can happen during device operation.
3Area of stationary object
If the protective layer overlaps the substrate in the wiring region, then coverage is improved, but stress concentration occurs between the wiring region and protective layer overlapping region
Solution Approach 1:
The protective layer is strategically positioned with different coverage in different regions: the first protective layer covers the non-overlapping region where stress concentration would occur, while the second protective layer covers the overlapping region where the wiring is already protected by the sandwich structure. This local differentiation provides adequate coverage without creating stress concentration at boundaries.
Solution Approach 2:
The second protective layer acts as an intermediary element in the overlapping region, providing a transition zone that mediates between the first substrate and second substrate. This intermediary layer distributes stress evenly and prevents stress concentration at the boundary between the wiring region and protective layer overlapping region, while still providing comprehensive coverage.
Data Source
AI summary
A stretchable device that includes: a first substrate having stretchability; a first wiring on a first main surface of the first substrate; a second substrate facing the first substrate in a first direction that is a thickness direction of the first substrate and connected to the first substrate; a second wiring on a first main surface of the second substrate, facing the first wiring in the first direction, and electrically connected to the first wiring; and a first protective layer on the first main surface of the first substrate so as to cover a part of the first wiring, wherein the first substrate and the first protective layer overlap each other in a first overlapping region, the first wiring and the second wiring are electrically connected in a wiring region, and the first overlapping region is separated from the wiring region when viewed from the first direction.