Stretchable Substrate Flap Design for Electronic Component Protection
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Solution Overview
Problem
Stretchable electronics with rigid or non-stretchable components face high stress and strain when stretched, leading to increased risk of interconnect failure, especially on highly stretchable substrates like TPU, where existing protection methods like globtops and underfill only shift stress concentration and do not adequately protect integrated circuitry or chips.
Innovation Solution
Creating a flap on the stretchable substrate by cutting it, allowing electronic components to be isolated on the flap with conductive tracks extending through a connected section, and surrounding the flap with lamination layers to form a pocket, which minimizes strain on the components and improves overall substrate flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid electronic components are placed directly on the stretchable substrate, then the device can achieve simple structure and ease of manufacture, but the interconnects experience high stress and strain leading to increased failure risk
Solution Approach 1:
The substrate is segmented into a main section and a flap section through strategic cutting. The flap is disconnected from the surrounding main section except on one side, creating an isolated region for placing rigid electronic components. This segmentation allows the flap to move independently during stretching, reducing stress transmission to the components and their interconnects.
Solution Approach 2:
The rigid electronic components are extracted from the stretchable substrate environment by placing them on the flap, which is mostly disconnected from the main substrate. This extraction isolates the components from the stretching forces, allowing the substrate to be stretched without subjecting the rigid components to high stress and strain.
2Reliability
If protection measures like globtops and underfill are applied to rigid components, then bonding may be improved, but stress concentration is only shifted rather than eliminated
Solution Approach 1:
Instead of applying protection measures that merely shift stress concentration, the invention extracts the rigid components from the stretchable substrate environment by placing them on the isolated flap. This fundamentally removes the stress concentration problem rather than just relocating it, as the flap's disconnected structure prevents stress transmission to the components.
3Reliability
If smaller components are used to improve reliability during stretching, then interconnect failure risk is reduced, but advanced functionality is limited
Solution Approach 1:
The substrate segmentation into main section and flap enables the placement of larger, more functional components on the isolated flap. The flap's disconnected structure protects these larger components from stretching stresses, allowing advanced functionality to be achieved without compromising reliability during stretching and bending.
4Reliability
If meander patterns are used for electronic circuitry on PEN/PET substrates, then stress on interconnects is reduced, but the solution is insufficient for highly stretchable substrates like TPU
Solution Approach 1:
The invention extends the segmentation concept by creating a physically disconnected flap structure, which is more effective than meander patterns alone. This segmentation isolates rigid components on the flap from the stretching forces in highly stretchable substrates like TPU, providing superior protection compared to circuit pattern modifications.
Solution Approach 2:
The solution moves from modifying the circuit pattern in two dimensions to creating a three-dimensional structural separation with the flap. The flap can be lifted or displaced in the vertical dimension during stretching, providing an additional degree of freedom that protects components on highly stretchable substrates beyond what planar meander patterns can achieve.
Data Source
AI summary
An electronic device (100) comprises a stretchable substrate (30) with a flap (30f) formed by a cut (40) in the substrate (30). The flap (30f) is disconnected by the cut (40) from a surrounding main section (30m) of the substrate (30) except on one side. The flap (30f) is exclusively connected to the main section (30m) via a connected section (30c) of the substrate (30) between two ends (40a, 40b) of the cut (40). An electronic component (10) is disposed on the flap (30f) with electrical contacts (11,12) connected to conductive tracks (21,22) disposed on the substrate (30). The conductive tracks (21,22) extend between the component (10) disposed on the flap (30f), and other parts (10r) of the electronic device (100) outside the flap (30f) via the connected section (30c). The flap (30f) with the component (10) is disposed in a pocket formed by surrounding lamination layers (31,32).