High frequency instabilities in GMR heads due to metal-to-metal contact ESD transients

Utilizing a D-CDM (Direct Charged Device Model) ESD tester this study evaluates the failure rates of GMR heads by measuring high frequency instability noise events as the discrimination factor vs. ESD voltage. The D-CDM tester replicates the sub-1ns ESD event produced by metal-to-metal contact discharge that occurs as a charged component, in this case the GMR head, discharges to another object at a different electrostatic potential. By generating this ESD event at increasing charge voltages in an in-situ environment with a QuasiStatic (QST) tester, head failure effects were recorded. In addition to the standard parametrics of amplitude and resistance, advanced noise instability measurements were also performed. As is commonly understood with GMR heads amplitude may begin to fail unpredictably prior to detectable resistance failures, but this study analyzes the voltage levels where GMR heads become unstable, and their instability characteristics.