Characterization of contact discharge between small capacitance devices

The Giant-magnetoresistive (GMR) head suffers magnetic damage from ESD current on the order of 10 mA and thermal damage from ESD energy on the order of 0.5nJ. Contact discharge from an electrified object into a floating device was investigated as the peak current caused magnetic damage and as the energy-loss caused thermal damage. Experiments with discharges between various capacitors clarified that the discharge between 2pF-capacitors at 10V gave a peak current of 34mA and the discharge between 100pF-capacitors at 100V reached 1.5A. A 3D-plot of the peak current simulated by PSPICE indicated that the peak value arose at the order of pF and was approximately maximized at the same value of both capacitors. The current waveform was affected by additional micro-capacitance of 0.5pF. Theoretical energy-loss was estimated by the difference between the potential energies prior to and following the discharges. The energy -loss was 0.05nJ for 2pF-capacitors at 10V and increased in excess of 0.5nJ when both capacitors were greater than 20pF. 3D-plot of the energy-loss indicated a gradual increase as both capacitance-values increased. Comparison of the potential energy-loss and the current energy indicated that the contact resistance decreased from 100ohm to few-ohm as the energy-loss increased.