A Case Study on Hidden ESD Events of GMR HGA Dynamic Test Fixture

摘要

This paper aims to reveal ESD event that is usually overlooked during HGA dynamic test operation and how a solution to the problem has been established. Experiments were conducted to determine a hidden ESD source by using two different designs of dynamic test shoe. ESD events were captured during unloading and reloading of HGA BFC pad to the old shoe fixture (original design). Tribocharging and field-induced charging are both suspects in the observed failures. These results are consistent with CDM type ESD failure. Results show how this event caused severe magnetic or melting damage to the GMR sensor. We were able to measure of about 155 volts (negative charge) on BFC kapton after unloading from the old shoe DET fixture. Our fast digital oscilloscope captured 131.2 mA (max) at 1 nanosecond current transients during metal contact of MR exposed lead. This causes a great yield loss at HSA level manufacturing for that particular prototype program.