Thermal asperities sensitivity to particles: Methodology and test results

Thermal asperities (TA's) are tribological events that muse repercussions f or giant magnetoresistance (GMR) and MR heads in the hard disk drive indust ry. A TA is a read signal spike caused by sensor temperature rise due to co ntact with disk asperities or contaminant particles. TA events ma?, cause G MR and MR heads to temporarily lose their reading capability, and may poten tially damage the transducer. It is difficult to completely avoid particle contamination in hard drive applications. Hence it is necessary to design h eads/ media with a minimum TA sensitivity to particles. A test method for T A sensitivity to particles is needed. This work developed a test method for TA sensitivities to particles. The test system includes a CSS tester with TA detection capability, a chamber to contain the head/disk interface, a pa rticle atomizer and a particle counter. Aluminum silicate particles used in the test have sizes ranging from 0.2 to 1.0 mum. Particles are injected in to the chamber during head scan for TA's from ID to OD with adjustable air- borne concentrations in the chamber from 10X10(6) to 30X10(6) particles/m(3 ). TA counts of 30 scans are averaged to obtain reliable TA sensitivity dat a. Media with different lubricant thickness, difference carbon overcoats, a nd different lubricant types are rested with this method. The results indic ated that this methodology can effectively differentiate TA sensitivity to particles for the media studied.