Flexible Electronics Using Rigid Substrates and Hinge Regions
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Solution Overview
Problem
Traditional rigid printed circuit boards (PCBs) are not suitable for applications requiring high flexibility, as modifying them for flexibility reduces mechanical strength and can lead to electrical or mechanical degradation due to repeated deflection, limiting their use in industries like aerospace and consumer electronics.
Innovation Solution
A flexible electronics assembly is created by geometrically modifying a single-piece substrate to include a localized region of flexibility with lower rigidity than the surrounding regions, using compliant joints like lamina emergent torsional (LET) joints, which act as hinges to deflect the substrate from a planar to a non-planar configuration without stressing the electronic components, and incorporating electrically conducting traces for connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid printed circuit boards are used for mechanical support, then mechanical strength is maintained, but flexibility and ability to conform to shapes are lost
Solution Approach 1:
The rigid PCB is segmented into multiple rigid regions separated by flexible hinge regions. The rigid regions maintain mechanical strength and support electronic components, while the flexible hinge regions provide flexibility and conformability. This segmentation allows the board to be folded or bent at specific locations without compromising the structural integrity of the component-bearing areas.
Solution Approach 2:
Different regions of the PCB are assigned different mechanical properties: rigid regions with high strength for component mounting, and flexible regions with lower rigidity for bending and folding. This local differentiation of material properties enables the board to simultaneously exhibit both strength and flexibility in appropriate locations.
2Adaptability or versatility
If rigid PCBs are modified to increase flexibility, then adaptability improves, but mechanical strength and reliability deteriorate
Solution Approach 1:
By segmenting the PCB into rigid and flexible regions, the design achieves flexibility only where needed (in the hinge regions) while preserving the mechanical reliability of the rigid regions that support electronic components. This prevents the entire board from being weakened while still providing the necessary adaptability.
Solution Approach 2:
The flexible properties are localized to specific hinge regions rather than being distributed throughout the entire board. This ensures that the rigid regions maintaining component support preserve their mechanical reliability, while only the designated flexible regions exhibit adaptability for folding and conforming.
3Adaptability or versatility
If repeated deflection is applied to flexible PCBs, then shape conformity is achieved, but electrical and mechanical degradation occurs
Solution Approach 1:
The segmentation isolates the repeated deflection stresses to the flexible hinge regions, protecting the rigid regions with mounted electronic components from mechanical and electrical degradation. The hinge regions are designed to accommodate bending while the rigid regions remain stable and reliable for component operation.
Solution Approach 2:
By localizing the flexibility to hinge regions and maintaining rigidity in component-bearing regions, the design allows shape conformity through controlled bending in flexible areas while preserving electrical and mechanical stability in the rigid areas where components are mounted and connected.
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 approach allows for flexible electronics that maintain mechanical strength and electrical connectivity, enabling the assembly to be used in applications requiring shape conformity and repeated deflection without mechanical or electrical failure, as demonstrated by the successful folding of solar panels and other prototypes.
Implementation Method 1
The localized region of flexibility elastically accommodates substantially all stresses and strains in the single-piece substrate caused by angular deflection of the two regions of rigidity
Implementation Method 2
The compliant joint is configured to transfer a bending load associated with angular deflection of the two regions of rigidity and applied to the compliant joint as a torsional load on torsional members of the compliant joint
Data Source
AI summary
A flexible electronics assembly includes a single-piece substrate having two regions of rigidity separated by a localized region of flexibility. The localized region of flexibility has a lower rigidity than the two regions of rigidity. The two regions of rigidity are angularly deflectable from a planar configuration of the single-piece substrate to a non-planar configuration of the single-piece substrate by hinging action of the localized region of flexibility. At least one electronic component is mounted on at least one of the two regions of rigidity.