HDA-level ESD testing of giant magnetoresistive (GMR) recording heads

The drive-level electrostatic discharge (ESD) behavior of a recent model of a desktop disk drive is discussed. ESD events are simulated up to 30 kV using an ESD gun (IEC-801). The drives were evaluated at the final assembly level. The head disk assemblies (HDAs) were equipped with GMR heads and single ended preamplifiers. In a manner similar to evaluations of head stack assemblies (Wallash, 1999), the head disk assemblies were stressed using an ESD gun at various strategic points of the drive. The printed circuit boards were in place when directing ESD events to the base and removed to address the motor pins. A quasi-static tester (QST) was employed to evaluate the GMR head condition as described by the signal amplitude, resistance and pinned layer orientation. The QST was able to evaluate the GMR condition without any disassembly of the drive. Analyses of the GMR condition before and after ESD stress are discussed.