Data storage devices may employ thin film magnetic transducers positioned proximate the surface of a magnetic storage medium such as hard disk or tape. Hard disk drive data storage devices typically use thin film magnetic transducers carried on a somewhat conductive ceramic slider. The slider is designed for aerodynamic suspension above a rigid rotating disk so as to position the transducer magnetic core tips as closely as possible to the surface magnetic coating of the disk.
A typical read/write head includes a magnetic core having an air gap to record magnetic transitions in the medium surface during a write operation and to sense such transitions during a read operation. The core is magnetically linked to a coil. Electrical current in the coil during a write operation generates magnetic flux in the core to record transitions in the surface magnetic coating of a disk or other medium. During a read operation a voltage is induced in the coil as recorded transitions pass the air gap. Insulating layers electrically isolate the coil, core and supporting structure, such as a slider, from each other.
The core defines pole tips which are exposed at a surface opposing the storage medium. In a disk drive head, for example, the pole tips are positioned on the air bearing surface of the slider. It is desirable to minimize the distance between the storage medium surface and the pole tips, this distance is typically maintained at or below a few microinches. Coil electrical potential typically differs from that of the recording medium. Pole tip potential must be kept close to that of the medium to prevent electrical discharge across the small air gap separating the medium surface from the pole tips. Such discharge produces electrical noise which interferes with the read operation and damages the pole tips and medium thereby reducing operational reliability. Coil to disk voltage is typically not at or near zero during write/read operations.
The impedance of the insulation separating coil and core must be high to prevent the core pole tips from reaching coil potential. The breakdown voltage of coil to core insulation is typically below 1000 volts. Such insulation is therefore sensitive to overvoltages accidentally applied during fabrication, head installation, and shipping. Core-to-coil insulators are easily damaged during fabrication, installation and use. For example, electrostatic charges can build up on the conductors of the magnetic circuits of the transducer, especially during head fabrication, and arc from coil to core and core to support structure causing pole tip erosion and damaging the core to coil insulating layer thereby lowering coil-to-core impedance. Once such impedance is lowered, the core will assume coil potential, eventually resulting in undesired head to disk contact. State of the art semiconductors are often protected from electrostatic discharge damage by means of voltage limiting diodes.
It is an object of the present invention to provide overvoltage protection of core to coil insulation using discharge means through a small air gap.