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Adding an Electrical Contact and Connection to the MR Shield(s) Disclosure Number: IPCOM000015251D
Original Publication Date: 2002-Feb-15
Included in the Prior Art Database: 2003-Jun-20

Publishing Venue



This is part of the Potential Matching AE system solution disclosure. To eliminate Electrostatic Discharges (ESD) from occurring among closely spaced elements (heads and media) inside a Hard Disk Drive (HDD), a solution is to prevent any potential differences from developing among the elements. To achieve that, this invention adds a potential matching output to the Arm Electronics (AE). The potential matching circuitry in the AE will connect to a contact on the MR head via a line in the interconnect. The potential matching contact on the MR transducer is connected to the MR shield or shields. As MR element to media spacing continues to decrease to support ever higher areal density HDD designs, even relatively low potential differences between the MR head and the media can cause discharge events to occur with disastrous consequences leading to drive failures. Unfortunately demands for ever faster drive performance often dictates putting common mode potentials that differ from the preferred equipotential such as Ground onto the MR sensor contacts. For example, to speed up write-to-read recovery time, a significantly high common mode potential maybe applied to the MR sensor. This potential difference can then capacitively couple to the adjacent MR shields. In the event of a contact with an asperity or momentary low head to disk spacing, discharge between the MR sensor and the media can occur and this can trigger subsequent discharges from the MR shields to the MR lead(s) and/or media surface causing catastrophic drive failures. In transducers with NiFe shields, the discharge event may occur equally between the two shields, S1 and S2, and/or simultaneously to both. In transducers with NiFe S2 and Sendust S1, for example, the much higher conductivity of the NiFe S2 makes it the preferential discharging surface. By adding a single contact to the high conductivity S1 and S2 shields or possibly just the S2 shield in transducers with low conductivity (e.g. Sendust) S1, the potential differences between the MR leads and the shields can be eliminated. A side benefit of the shield contact is that one can then measure any MR to shield shorts directly. This invention is part of a system level approach to eliminate ESD damages on the shields and MR sensor and leads. The invention solves the ESD problem independent of the head to media spacing without sacrificing the drive performance (e.g. write-to-read recovery time). The invention also will prolong MR sensor life by allowing the sensor bias to be turned off during write without causing catastrophic discharge events that destroy the MR head's ability to sense magnetic flux. 1