Electrode Pad Insert Coupling for Strain Gauge Thermal Stress
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Solution Overview
Problem
Strain gauges with high gauge factors, such as Cr—N, are prone to cracking or peeling due to thermal stress when soldered to electrode pads with mismatched thermal expansion coefficients, leading to potential disconnection and reduced coupling reliability.
Innovation Solution
A coupling structure with an insert design where one of the tab and electrode pad is partially or entirely inserted into the other, enhancing the joining strength and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strain gauge made of Cr-N is used to increase the gauge factor, then the output sensitivity is improved, but thermal stress causes cracking or peeling of the tab due to mismatched thermal expansion coefficients
Solution Approach 1:
The patent applies the nesting principle by inserting one component into the other to create an interlocked structure. Specifically, the tab is inserted into the electrode pad or the electrode pad is inserted into the tab, forming a nested configuration that mechanically locks the two components together. This prevents relative movement and eliminates the cracking or peeling caused by thermal expansion mismatch, while maintaining the high gauge factor Cr-N strain gauge material.
Solution Approach 2:
The coupling structure is segmented into distinct insertion and receiving portions. The tab has an insertion portion that fits into a receiving portion of the electrode pad, or vice versa. This segmentation allows for controlled mechanical coupling that accommodates thermal expansion differences while maintaining electrical connection reliability.
2Ease of manufacture
If high-temperature heat is applied during soldering, then the gauge lead can be coupled to the strain gauge, but thermal expansion mismatch applies stress to the tab causing cracking or peeling
Solution Approach 1:
The patent applies beforehand cushioning by pre-establishing a mechanical coupling structure through insertion before the soldering process. The interlocked insertion structure acts as a cushion or buffer that prevents stress concentration during thermal expansion in the soldering process, thereby protecting the tab from cracking or peeling while still allowing successful gauge lead coupling.
3Reliability
If a metal electrode pad is used for electrical coupling, then electrical conductivity is improved, but thermal expansion coefficient mismatch with the strain gauge material causes stress and potential disconnection
Solution Approach 1:
The nesting principle creates a mechanical interlock between the metal electrode pad and the tab that compensates for thermal expansion differences. The inserted portion acts as a stress-absorbing joint that maintains electrical connection reliability while accommodating the harmful thermal stress generated by coefficient mismatch during temperature changes.
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 insert structure prevents cracking and peeling of the tab, improving the coupling reliability between the strain gauge and gauge lead, ensuring stable electrical connection and accurate strain measurement.
Implementation Method 1
the thermal expansion coefficient of the material of the electrode pad and the thermal expansion coefficient of the material of the strain gauge are significantly different from each other, and a tensile stress or a compressive stress is applied to the tab in accordance with expansion of the electrode pad
Data Source
AI summary
A coupling structure for an electrode pad is configured to electrically couple the electrode pad, to which a gauge lead is coupled, to a tab of a strain gauge disposed on an elastic body and including a gauge grid and the tab. The coupling structure has an insert structure in which one of the tab and the electrode pad is partially or entirely inserted into the other.