Effect of Pretreatment on Electroless Ni-P Deposits for Magnetic Hard Disk

Thin-film media for increasing the recording density on magnetic hard disks have been obtained by sputtering or plating, and since these media require a comparatively flat substrate, electroless Ni-P plating is employed to harden the surface and facilitate polishing To be used successfully, the process must be satisfactory in terms of such properties as finished final surface roughness, magnetization, and adhesion The object of the present work is to examine various pretreatments for 5086 Al-alloy, the most common material used for hard disk substrates. Results indicate that the optimum process was one consisting of alkaline non-etch cleaning, hot acid etching and double zincate treatment. This produced a homogeneous and thin zinc film. Though deeper etching improved adhesion, it also increased roughness after plating