Thermal mechanics of a contact sensor used in hard disk drives

A typical thermal-contact sensor (TCS) used in hard-disk drives was investigated by the simulation. Analytical solution to solve temperature variation of sensor due to frictional heat was built to estimate the sensor temperature rise under variable heating power and interference height between the head and disk. To accurately and systematically qualify sensor-temperature distribution and resistance variation under certain variable conditions and sensor time constant, head housing a TCS was modeled by ANSYS commercial software, and thermal-mechanics of TCS coupled with air bearing dynamics was simulated. Simulated results indicated that a TCS with a proper size of 1 μm or less had a maximum resistance variation on friction induced heating to generate a maximum TCS signal output. The sensor-heating maximum protrusion was less that 0.1 nm, and time constant of TCS is about 0.125 μs and its response frequency is about 8 MHz. With a highly accurate measurement system, TCS can detect out asperities of tens of nanometers or less. These results will be helpful in developing and designing thermal-contact sensors for use in hard-disk drives.