Stretchable Wiring Layout With Curved Bends to Prevent Cracking

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Solution Overview

Problem

Conventional stretchable devices face issues with wiring damage due to repeated stretching and contracting, leading to cracks and fractures, and there is a need for a stretchable wiring board that minimizes these issues while maintaining conductivity.

Innovation Solution

A stretchable wiring board design featuring a stretchable insulating substrate with stretchable wiring that includes linear portions and bent portions with specific geometric configurations, such as recessed triangular and arcuate shapes, to distribute stress evenly and reduce cracking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional wiring is used on stretchable substrates, then the wiring board can be made stretchable, but the wiring will suffer from cracks and fractures due to repeated stretching and contracting

Engineering Contradiction:

ImprovestretchabilityVSAvoidwiring integrity

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The wiring is designed with bent portions having specific curved geometries (recessed triangular portions and arcuate portions) instead of sharp corners. This curvature distribution allows the wiring to flex and deform elastically during stretching and contracting, preventing stress concentration that would lead to cracks and fractures, thus maintaining wiring integrity while preserving stretchability

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The bent portions are strategically positioned at specific locations where stress concentration would otherwise occur. By localizing the curved geometry at these critical points, the design provides enhanced stress relief exactly where needed, preventing cracking at vulnerable locations while maintaining overall wiring functionality and stretchability

Inventive Principle:

Principle #3Local quality

2Reliability

If horseshoe-shaped or bellows-shaped wiring is used, then wiring damage is reduced, but the board remains vulnerable to repeated stretching and contracting motion

Engineering Contradiction:

Improvewiring damage resistanceVSAvoidresistance to repeated motion

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The bent portions incorporate smooth curved transitions (arcuate portions) that allow progressive deformation during repeated stretching and contracting. This curved geometry enables the wiring to undergo elastic deformation cycles without developing fatigue cracks, significantly improving resistance to repeated motion while maintaining wiring damage resistance

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The wiring geometry is designed to dynamically adapt to stretching and contracting motions. The bent portions with specific curvature ratios can flex and deform in response to applied stress, allowing the wiring to accommodate repeated motion cycles. This dynamic response capability enables the board to withstand repeated stretching and contracting while maintaining wiring integrity

Inventive Principle:

Principle #15Dynamics

3Device complexity

If the wiring has linear portions only, then the structure is simple, but the wiring will crack under tensile and compressive stress during bending

Engineering Contradiction:

Improvewiring structureVSAvoidwiring resistance to stress

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

By introducing bent portions with specific curved geometries (recessed triangular portions and arcuate portions) into the wiring structure, the design provides stress relief capabilities without significantly increasing overall complexity. The curved portions allow the wiring to accommodate tensile and compressive stresses during bending by distributing stress along the curved path, preventing crack formation while maintaining reasonable structural simplicity

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The wiring is divided into linear portions and bent portions with distinct functions. The linear portions provide direct electrical connection paths, while the bent portions provide stress relief. This segmentation allows each portion to be optimized for its specific function, maintaining wiring strength during stress while keeping the overall structure relatively simple and manufacturable

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS20260068040A1Stretchable wiring board and stretchable device using same

Publication Date: 2026.03.05 TDK CORP

AI summary

This stretchable wiring board includes: a stretchable insulating substrate containing a resin; and a stretchable wiring that contains a resin and is formed on a main surface of the stretchable insulating substrate, in which the stretchable wiring has a plurality of linear portions extending linearly in multiple different directions, and bent portions that connect the linear portions extending in the different directions, and the bent portions have a rectangular section and a recessed triangular portion which is positioned on an inner contour side of the inner contour and an outer contour constituting its outer shape and is surrounded by two slanted edges and a recessed arc-shaped bottom edge when viewed in plan view.