Strain Gauge Composite Lines for High-Strain Electrical Continuity
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Solution Overview
Problem
Strain gauges attached to flexure elements face damage during expansion and contraction, limiting their strain detection capability.
Innovation Solution
A strain gauge design with a substrate, resistor, and lines formed on the substrate, where the lines are laminated with a second metal layer of lower volume resistivity than the first metal layer, and the second metal layer protrudes beyond the edge of the first layer to maintain electrical connection during strain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the strain gauge is attached to a flexure element to detect strain, then the strain detection capability is improved, but the strain gauge becomes damaged during expansion and contraction under high strain conditions
Solution Approach 1:
The line is constructed as a composite structure with a first metal layer (e.g., Cr, Ni, or their alloys) and a second metal layer (e.g., Cu, Al, Ag, or their alloys) having different material properties. The first layer provides adhesion to the resistor and substrate, while the second layer provides flexibility and strain tolerance, creating a composite material solution that resolves the contradiction between measurement precision and reliability.
Solution Approach 2:
The line structure transitions from a single-layer configuration to a multi-layer configuration in the vertical dimension. This dimensional change allows the line to accommodate strain through layer deformation while maintaining electrical connectivity, thereby improving reliability without compromising strain detection capability.
2Device complexity
If a single-layer metal line is used, then the structure is simple, but the line disconnects during strain-induced expansion and contraction
Solution Approach 1:
The line is constructed as a composite structure with a first metal layer (e.g., Cr, Ni, or their alloys) and a second metal layer (e.g., Cu, Al, Ag, or their alloys) having different material properties. The first layer provides adhesion to the resistor and substrate, while the second layer provides flexibility and strain tolerance, creating a composite material solution that resolves the contradiction between measurement precision and reliability.
Solution Approach 2:
The line structure transitions from a single-layer configuration to a multi-layer configuration in the vertical dimension. This dimensional change allows the line to accommodate strain through layer deformation while maintaining electrical connectivity, thereby improving reliability without compromising strain detection capability.
3Ease of manufacture
If the second metal layer is confined within the first metal layer boundaries, then the manufacturing process is easier, but the line disconnects when strain causes the first metal layer to crack
Solution Approach 1:
The second metal layer is intentionally extended beyond the first metal layer boundaries in advance, before strain is applied. This preliminary extension ensures that when the first metal layer cracks under strain, the second metal layer maintains electrical connectivity by bridging the gap, thus preventing disconnection while maintaining manufacturing feasibility.
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
The strain limit of the strain gauge is improved, allowing it to function effectively under higher strain conditions without disconnection.
Implementation Method 1
a second metal layer that is laminated on the first metal layer and is formed of a material having lower volume resistivity than the first metal layer
Data Source
AI summary
A strain gauge includes a substrate, a resistor formed on the substrate, and two lines. The resistor includes multiple elongated portions. Each of the lines includes a first metal layer and a second metal layer that is laminated on the first metal layer and is formed of a material having lower volume resistivity than the first metal layer. In plan view, an outer edge of the first metal layer is exposed from the second metal layer. In plan view, an end of the second metal layer on a first end side in a first direction protrudes further toward the first end side in the first direction than an end of a space that is situated between the first metal layer and an elongated portion adjacent to the first metal layer.