Field-induced charging and FIM ESD tests on GMR heads in Hard Disk Assembly

Both field-induced charging and ESD tests on non-input/output locations on uncovered HDA were studied. The lowest failure thresholds for GMR sensors due to fast charging transients and hard discharge were about 1000 V and 150 V respectively. Such threshold for a slow field-induced charging within a fraction of second was about 1500 V. A direct HBM ESD in the absence of field induction on the HDA would have 1300 V threshold. All these results show that protection focused at input/output and at HDA baseplate ground may not be sufficient. This study confirms that for HDA, FIM events are by far the most severe form of ESD.