Stretchable Circuit Substrate With Bellows Wiring Stress Control
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Solution Overview
Problem
The existing methods for producing stretchable circuit substrates result in uneven changes in the form of metal thin films, leading to localized stress concentration and potential fractures, as well as increased resistance values due to differences in base material extension and metal film distribution density.
Innovation Solution
A stretchable circuit substrate design incorporating a bellows-like member with ridges and recesses, an adjustment layer with a lower Young's modulus than the wiring, and a supporting base material with a higher Young's modulus, which disperses stress and maintains consistent form changes across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the base material is expanded and then relaxed to create bellows-like shape in the metal thin film, then the stretchability of the substrate is improved, but uneven stress distribution occurs leading to localized fractures and increased resistance
Solution Approach 1:
The patent introduces an adjustment layer with specifically controlled Young's modulus (smaller than the wiring but larger than the base material) positioned only in the wiring region. This creates local quality differentiation where the adjustment layer provides targeted stress distribution control in areas needing it, while leaving other regions unaffected. The layer acts as a stress buffer that prevents localized stress concentration at the metal thin film interface during stretching cycles.
2Adaptability or versatility
If the metal thin film is made thin to maintain flexibility, then the stretchability is improved, but the resistance value increases and fracture risk increases due to insufficient stress distribution
Solution Approach 1:
The adjustment layer serves as an intermediary element between the base material and the metal thin film wiring. It mediates the stress transfer by providing a compliant interface that distributes mechanical stress uniformly across the wiring region. This prevents stress concentration that would otherwise occur at the thin metal film, thereby maintaining resistance stability and preventing fractures while preserving the flexibility enabled by the thin film structure.
3Adaptability or versatility
If the base material extension is increased to improve stretchability, then the adaptability is improved, but uneven form changes occur in the metal thin film leading to stress concentration
Solution Approach 1:
The patent controls the Young's modulus parameter of the adjustment layer to be within a specific range (smaller than wiring but larger than base material). This parameter optimization enables the layer to deform in a controlled manner during stretching, ensuring uniform form changes across the wiring region. The adjusted stiffness parameter allows the layer to accommodate base material extension while maintaining uniform stress distribution, preventing localized buckling or excessive deformation of the metal thin film.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design inhibits fractures and resistance value increases by evenly distributing stress, ensuring the substrate maintains functionality and integrity during repeated stretching.
Implementation Method 1
the adjustment layer has a Young's modulus smaller than a Young's modulus of the wiring... the supporting base material has a Young's modulus larger than a Young's modulus of the base material
Implementation Method 2
a bellows-like member with ridges and recesses arranged in a first direction which is one of in-plane directions in the first surface of the base material
Data Source
Figure 1A~1B
Figure 2A~2D
Figure 3A~3D
AI summary
The present disclosure provides a stretchable circuit substrate comprising: a base material being stretchable; a wiring which is on a first surface side of the base material, and which includes a bellows-like member including a plurality of ridges and recesses arranged in a first direction which is one of in-plane directions in the first surface of the base material; and an adjustment layer which includes the bellows-like member and is on the first surface side of the base material so as to at least overlap, in a plan view, a wiring region in which the wiring is positioned; wherein the adjustment layer has a Young's modulus smaller than a Young's modulus of the wiring.