Miniature Strain Gauge Electrode Layout for Reliable ACF Bonding

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Miniaturization of strain gauges complicates the connection of lead wires using solder, necessitating improved join reliability between miniaturized electrodes and flexible substrates.

Innovation Solution

A strain gauge design featuring a flexible substrate with a resistor made of chromium or nickel, and electrodes comprising juxtaposed patterns connected by dummy patterns, ensuring uniform application of heat and pressure via an anisotropic conductive film for reliable joining.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the strain gauge is miniaturized, then the size of the strain gauge is reduced, but the join reliability between the electrode and the flexible substrate deteriorates

Engineering Contradiction:

Improvesize of strain gaugeVSAvoidjoin reliability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The electrode is divided into multiple first patterns juxtaposed at predetermined intervals, with dummy patterns filled between opposing electrodes. This segmentation increases the total bonding area while maintaining a compact overall size, thereby improving join reliability without increasing the strain gauge dimensions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Dummy patterns are strategically positioned between opposing electrodes to locally enhance bonding capacity. These dummy patterns do not affect the electrical function but provide additional bonding surfaces, creating non-uniform bonding density optimized for reliability.

Inventive Principle:

Principle #3Local quality

2Reliability

If solder is used to join the electrode, then the electrical connection is achieved, but the manufacturing difficulty increases when miniaturized

Engineering Contradiction:

Improveelectrical connectionVSAvoidjoining process

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

An anisotropic conductive film is introduced as an intermediary bonding material between the electrode and the flexible substrate. This film provides both electrical conductivity and mechanical bonding, eliminating the need for soldering while enabling reliable connections in miniaturized structures.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The thermal-mechanical soldering process is replaced with a pressure-driven bonding process using the anisotropic conductive film. This substitution eliminates high-temperature processing and complex soldering operations, simplifying manufacturing for miniaturized devices.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If the electrode size is reduced, then the strain gauge is miniaturized, but the bonding area with the flexible substrate is insufficient

Engineering Contradiction:

Improvestrain gauge sizeVSAvoidbonding area

Core Design Contradiction:

Volume of moving objectVSArea of stationary object

Solution Approach 1:

The electrode is segmented into multiple first patterns arranged in parallel, with dummy patterns filling the spaces between opposing electrodes. This segmentation multiplies the bonding interfaces, increasing the total bonding area without increasing the overall electrode footprint.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bonding area is expanded in the vertical dimension by adding dummy patterns between opposing electrodes, rather than only expanding the horizontal electrode dimensions. This creates a three-dimensional bonding architecture that maximizes contact area within a compact planar footprint.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enhances join reliability between miniaturized strain gauges and flexible substrates, maintaining gauge factor and resistance to environmental factors.

Implementation Method 1

uniform application of heat and pressure via an anisotropic conductive film

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

uniform application of heat and pressure via an anisotropic conductive film

Methodology Applied

Scientific EffectPressure: Pressure Increase

Implementation Method 3

a resistor for detecting strain, and as a resistor material, for example, material including Cr (chromium) or Ni (nickel) is used

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS12523556B2Strain gauge

Publication Date: 2026.01.13 MINEBEAMITSUMI INC

AI summary

A strain gauge includes a flexible substrate, a resistor, and electrodes. Each electrode includes first patterns juxtaposed at predetermined intervals and electrically connected to each other. Second patterns of which longitudinal directions are toward a same direction as a longitudinal direction of each of the first patterns are disposed between opposing electrodes. The second patterns are electrically floating dummy patterns. The second patterns of which the longitudinal directions are toward a same direction as the longitudinal direction of each first pattern are disposed, the second patterns being interposed between first patterns opposite each other that are among given first patterns that constitute one of the electrodes and given first patterns that constitute another electrode. The plurality of second patterns are interposed between first patterns opposite each other that are among given first patterns that constitute one of the electrodes and given first patterns that constitute another electrode.