A novel method for evaluating triaxial strain gages used in printed circuit board assemblies (PCBA) strain monitoring

This paper reports a novel method for evaluating strain gages. In this method, the evaluated gage is attached at a specific location of coupon board, and then deflects 5 known distances by steps by the insertion of shims with different thicknesses. The strain for each bended status is recorded and can be compared against expected variation. If the principle strain values and corresponding angles within the tolerance, the gage passes the test and can be applied in practical strain measurement with increased confidence, otherwise it will be deprived of the qualification to accept. Moreover, this method combines with accredited gages can also be used to find and eliminate many errors due to gage placement, gage attachment, measurement equipment setup, and lead wires. In order to prove the validity of the given method, three types of gages from various suppliers at are evaluated, and the results of test broadly consistent with technical backgrounds of their respective manufacturers.