Quantitative Imaging Of Disk Lubricant Thickness By Readback Signal Analysis

Abstract

Zn Situ media lubricant thickness in a hard disk drive is measured by analysis of amplitude modulation (AM) in the readback signal. Amplitude modulation is mapped over an area of the disk and the image is scaled into equivalent spacing loss using the Wallace spacing loss equation. The first image is used as a reference for subsequent measurements. Head to disk spacing is modified by the removal of a section of lubricant from a small portion of the imaged region. The area is re-imaged and subtracted from the reference. The new image shows the resulting changes in head/disk spacing. The change in lubricant thickness after either a Freon TF or TF ethanol wash was between 0.6 nm and 0.7 nm.