Modeling of contact discharge between floating 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 2D-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. 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 grater than 20pF. The energy-loss reached 250nJ for 100pF-capacitors at 100V. 2D-plot of the energy-loss indicated a gradual increase as both capacitance-values increased. In order to decrease the risk of ESD failure, reducing the capacitance of the device was effective, because the transferred-charge and energy-loss were restricted.