First, the strain gauges are attached to several different positions on the PCB. When the process or work station is operated, the strain gauges are connected to the measurement instrument system to make the stress quantitatively display the records.
Namely: Strain - Resistance Change - Voltage (or Current) Change - Magnification - Recording - Data Processing
The strain gauge is a kind of sensor that can change the resistance value linearly according to the magnitude of the stress. When the strain gauge is deformed, the resistance value will change accordingly.
Select the PCBA mounting plate according to the procedure to be tested, and select the test points on the PCB to paste the strain gages according to the position of the stress. If there is not enough space on the board to attach the strain gauge, the parts already fixed on the board have to be removed to make room. Note that the specific bonding meter required for strain gauges generally requires at least two or three PCBAs to be tested for installation to demonstrate the correctness and consistency of the test.
Connect the leads of the strain gauge to the data acquisition instrument of the test system, and adjust the sweep frequency (also referred to as sampling rate), sampling resolution, gain setting, excitation voltage, number of channels, etc., and run the test program for the duration of the test. Variable, generally can run 5-10 seconds and record data.
For the PCBA board strain test, the recommended sweep frequency range is 500Hz-2kHz. Generally, a higher frequency is selected as far as possible so that instantaneous stress changes can be captured.
Analyze these acquired strain data, calculate the stress (maximum stress and minimum stress) applied to the PCBA during the test, and record all the data.