Flush Surface Stretchable Wiring Board Design
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Solution Overview
Problem
The existing stretchable wiring boards for wearable devices and medical devices suffer from surface unevenness due to protruding wiring and terminals, causing discomfort to users.
Innovation Solution
A stretchable wiring board design featuring a conductor portion with a wiring portion covered by an overcoat layer and a connection portion exposed, where the exposed surface of the connection portion is flush with the overcoat layer, and reinforced by reinforcing members buried within or attached to the substrate, ensuring a smooth surface and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wiring portion and external terminal protrude from the main surface of the stretchable substrate, then the electrical connection function is improved, but the surface unevenness increases causing user discomfort
Solution Approach 1:
The patent transitions the connection portion from a protruding three-dimensional structure to a flush two-dimensional surface by having the overcoat layer cover the conductor portion and extend to the same level as the connection portion, eliminating the height difference while maintaining electrical connectivity through the lateral extension of the overcoat layer
Solution Approach 2:
The overcoat layer acts as an intermediary element that bridges the conductor portion and the connection portion, covering the conductor while extending to cover the connection portion's top surface, thereby mediating the transition from protruding to flush structure and eliminating surface unevenness
2Ease of operation
If the connection portion is exposed from the overcoat layer, then the electrical connection accessibility is improved, but the surface unevenness increases
Solution Approach 1:
The overcoat layer extends in the lateral direction to cover the connection portion's top surface, transforming the vertical exposure structure into a horizontal flush structure, maintaining accessibility through the same-plane configuration rather than vertical protrusion
3Reliability
If the wiring portion is covered with the overcoat layer, then the insulation performance is improved, but the manufacturing precision requirement increases
Solution Approach 1:
The overcoat layer is formed to extend beyond the conductor portion boundaries in advance, creating a sufficient lateral overlap region that ensures complete coverage of the conductor portion and automatic formation of the flush surface with the connection portion, eliminating the need for precise post-alignment
Data Source
AI summary
A stretchable wiring board includes: a first stretchable substrate; an overcoat layer; and a conductor layer interposed at least partly between the first stretchable substrate and the overcoat layer. The conductor layer includes a wiring portion covered with the overcoat layer and a connection portion that has a surface exposed from the overcoat layer. The exposed surface of the connection portion is flush with a top surface of the overcoat layer.