Effect of surface resistance of metal evaporated tape on discharge current

In the helical-scan tape system, the magnetoresistive (MR) head is used in the MICROMV consumer VCR format. A giant magnetoresistive head for high-recording density is more sensitive to electrostatic discharge (ESD) than an MR head. In order to evaluate the damage caused by ESD, a new charged tape model (CTM) was devised and it was compared with a model using an ESD gun. The surface resistance of metal evaporated tape was investigated with a view to minimizing discharge current through the MR head. As the surface resistance increased from 1.1e+3 to 1.8e+8 Ω/sq, the peak discharge current decreased inversely proportional to the surface resistance and proportional to the applied voltage. The CTM supplied a short pulse (200 ns) but a high peak current. The ESD gun supplied a long pulse (more than 1 μs) and its peak current decreased with the distance from the head. The authors conclude that the discharge current from the tape surface can be controlled by the surface resistance.