A study of ESD protection for helical-scan tape heads

A GMR head for a helical-scan tape system is affected by two sorts of electrostatic discharges (ESD): one is from an electrified wire to a terminal of the head and another is from a tape mike to s GMR sensor. A generally available coated wire is electrified on its suface and can induce the charge on the copper core. When the wire is touching the GMR head terminal, the discharge current can damage the sensor of GMR head. Four kind of wires were meafllred with three different lengths, Resin coated wires were electrified fiom 20V to ova 1kV. The peak cmnt dischargng ta the GMR head reached from 100mA to over 1000mA.A resin coated wire as short as 5cm damaged the GMR head. Only enameled wire can be used because of my charge and any discharge current were not observed. When an ionizer is wed for neutralizing the tribocharge on the surface of the wire, the charge remaining on the copper core depends on the effectiveness of the neutralizing process. In order to avoid ESD from a tape suface to a GMR sensor, the resisitive ferrite substrate was developed to bypass the ESD current.