Modeling Electrostatic Discharge Affecting GMR Heads

Electrostatic discharge (ESD) damage to giant magnetoresistive (GMR) heads is investigated using a charged device model tester. The sensor of a GMR head is easily affected by ESD during handling in production. Simulation of the picking procedure reveals that elevating such a small-capacitance device above the work surface increases the potential by up to ten times and the discharge current by up to five times. With 20-V initial potential, which could be applied by the picking tool, the elevation of a 5-pF capacitance by just 10 mm increases the potential to 200 V and the peak discharge current to 578 mA. In the case of a 1-pF capacitor, however, the potential and peak current remained low due to the effect of stray capacitance. In the case of a GMR head with 3.7-pF capacitance, a 5-mm lift reduced the initial potential causing ESD damage from 60 V to less than 40 V. Waveforms of discharge reveal that the GMR head can be designed to reduce the ESD risk.