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Conformally Coated MR/GMR Sensor for Improved Corrosion Resistance and Higher Areal Density Recording and Method of Making the Same

IP.com Disclosure Number: IPCOM000014742D
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-20

Publishing Venue



Described is a conformal head coating and method of applying the same which provides improved edge coverage to the sensor, thus improving its resistance to corrosive attack, and allowing the use of thinner coatings that result in closer head/disk spacings for improved areal densities of recorded information. Furthermore, it will be seen by those skilled in the art that the utility of this invention is not limited solely to the sensor, but also finds application to any metallic structures present at the air bearing surface (ABS) such as the write elements or shields which might be susceptible to corrosive attack, and would, therefore, benefit from improved edge coverage. As areal densities increase, the constraints on spacing loss become ever greater. As a consequence, magnetic recording technology is driven to smaller magnetic spacings between the head and the disk, in the direction of contact recording. The total magnetic spacing budget is now 1 to 2 micro-inches or nominally 25 to 50 nm. As a result, layers on the head and disk used to protect the head or disk from corrosion are becoming increasingly thinner, viz. the dual layer carbon (DLC) layer, i.e. laminate, on the head is nominally 7nm. As a result of lapping to the required stripe heights, there is usually between 3 and 5 nm of relief at the edge of the stripe; this creates a problem for edge coverage by a 7 nm DLC layer, or by any protective coating layer. Consequently, if the edge coverage is not complete, this results in a path for attack of the sensor by corrosive constituents in the environment. Once the stripe, i.e. sensor, is attacked by corrosive agents, critical portions of the sensor are lost, and amplitude degradation can occur to the point where error rates become unacceptably high and information can no longer be read from the disk. Similar arguments also apply to the shields and the write elements, or pole tips. This invention solves the problem of inadequate edge coverage by conformally coating the head with the protective layer, or laminate. It is well known that the edges associated with the relief at different material layers act to shadow the region adjacent to the edges from deposition with a nominally unidirectional beam, which results in poor edge coverage. The ideal situation is to coat from all directions, but this cannot be accomplished with a fixed source, unless novel measures such as those described in the following are employed. The key to conformally coating the head is to use a pseudo-planetary motion of the substrate under the flux of depositing coating material. The motion of the substrate is such that it is rotated under the flux of the coating material whilst the substrate is simultaneously rocked back and forth by at least 45 degrees. This results in coating of the edges with nominally the same thickness of the deposit found over flat areas of the head. The problem of voids or inadeqaute thickness of the coating at the edges is thus eliminated, with resulting benefits for corrosion resistance, as well as the possiblity of coating with thinner layers which translates into closer fly heights and higher areal densities. A preferred embodiment of the invention comprises a protectively coated magnetic recording head having: 1) a conformal protective coating with essentially uniform thickness over edges located at the termini of generally metallic head elements, whereby the metallic head elements are rendered less susceptible to corrosive attack; and,