CORROSION STUDY OF HARD DISKS BY OSA AND XPS

Abstract

Perfluoropolyethers (PFPE) are most commonly employed as lubricants at head-disk interface in hard disk drives (HDD) to reduce friction and wear. Corrosion behavior is an important issue in high density magnetic recording disk-drives. The magnetic materials used in the magnetic storage layers as well as those used for making read–write transducers are not very corrosion resistant. In the presence of humidity and at elevated temperatures, corrosion occurs and materials from the magnetic layers and the NiP plating layers of the recording rigid media can migrate to the disk surfaces and form protrusions that are easily much larger than the head-disk clearances. As PFPE is sensitive to temperature, especially its mobile fraction, movement of the PFPE molecules will allow the magnetic media to be exposed to the environment through the micro pores existing in DLC overcoat, which will cause occurring of corrosion. In this paper, the corrosion characteristics of the magnetic media of the hard disks were analyzed using optical surface analyzer (OSA). X-ray photoelectron spectroscopy (XPS) was also used to characterize the distribution of the elements on the surfaces of hard disks. A relationship between heating time, lubricant layer thickness, number of corrosion spots and distribution of elements was attempted. It was found that the corrosion spots for the disks are related to the heating time. A small change in the thickness of lubricant layer can cause a drastic change in corrosion rate.