Head–disk contact detection in the hard-disk drives

The increasing capacity of current hard-disk drives places a great importance on reliability, as tens of gigabytes of data can be lost in an instant due to a single tribological failure event. To improve the reliability of the head–disk interface there is a need to predict, measure and monitor any interactions during manufacture. This paper discusses some different techniques that can be used for head–disk contact detection. These techniques range from a traditional acoustic emission method to some drive specific tests, such as thermal asperity (TA) detection and variable gain amplifier (VGA) signal measurements. The paper also discusses the merits of these techniques and ways to theoretically predict contact.