Contact/Clearance Sensor for HDI Subnanometer Regime

The fundamental performance of contact/clearance sensor, namely embedded contact sensor (ECS), is addressed in this paper. Both simulation and experiment results revealed that ECS is a promising sensor for low clearance and high reliability at subnanometer regime. The ECS dc signal intrinsically comes from multiple sources including TFC heater, air-bearing surface cooling, and friction heating at head/disk contact. Both ECS dc and ac signals detect head/disk contact. The dc signal comes from the sensor resistance change due to friction heating at contact, but the ac signal is dominated by spacing modulation caused by air-bearing vibration, and partially from the pulse-like friction heating. ECS ac signal responds significantly to disk microwaviness at narrow clearance region. Furthermore, ECS could detect asperities, pit, and lube mogul. The mechanism for asperity detection is friction heating. The mechanism for pit detection is worse cooling when sensor flying over the pit. That for mogul detection is better cooling at narrower spacing when the sensor is flying over the mogul.