Flexible Substrate Protruding Portion Stress Reduction
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Solution Overview
Problem
Existing flexible substrates face stress concentration issues at electrical connecting portions when bent or warped, leading to potential open circuits due to crack formation and complex structural requirements.
Innovation Solution
A flexible substrate design featuring a main portion and protruding portions that can be bent along intersecting directions, reducing stress at the electrical connecting portion by distributing it across the protruding portion's rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the flexible substrate is bent or warped to arrange wirings in three-dimensional spaces, then the wiring arrangement flexibility is improved, but stress concentration occurs at the electrical connecting portion causing open circuit
Solution Approach 1:
The electrical connecting portion is divided into a land portion (conductive layer) and a non-conductive portion (base member only), allowing the conductive path to be segmented and rerouted through multiple land portions connected by wirings, thus distributing stress away from single critical connection points
Solution Approach 2:
The electrical connecting portion is extended in the width direction of the flexible substrate, transforming a linear connection into a two-dimensional distributed structure with multiple land portions, which provides alternative stress paths and prevents stress concentration
2Reliability
If a fixing portion similar to electrical connecting portion is provided to prevent stress, then the electrical path open circuit is prevented, but the structure becomes complex requiring metal pins
Solution Approach 1:
The land portion serves dual functions: it provides electrical connection (conductive path) and structural reinforcement (stress distribution). This multi-functional design eliminates the need for separate fixing portions like metal pins, simplifying the overall structure while maintaining reliability
Solution Approach 2:
The fixing function is achieved using the same conductive layer material and formation process as the electrical connecting portions, creating homogeneous structures throughout the substrate. This avoids introducing heterogeneous elements like metal pins and simplifies manufacturing
3Strength
If through holes with adhesive material are used for connection and fixing, then the flexible substrate and component are adhered, but stress concentration occurs near the through hole causing cracks and open circuits
Solution Approach 1:
The harmful through holes that cause stress concentration are completely removed from the design. Instead, the invention uses surface-level land portions and wirings that distribute stress along the surface, extracting the problematic element while preserving the adhesion function through alternative means
Data Source
AI summary
A flexible substrate has an insulating base member and a conductive layer that is formed on the base member and includes an electrical connecting portion fixed to a component and electrically connected to the component, and the flexible substrate includes: a main portion on which the electrical connecting portion is formed; and a protruding portion provided so as to protrude from a portion of the main portion in which the electrical connecting portion is formed, wherein the main portion is bent along a first bending line extending in a first direction, and wherein the protruding portion can be bent along a second bending line extending in a second direction intersecting the first direction and is adapted to reduce stress occurring at the electrical connecting portion by the protruding portion being bent along the second bending line.