The evolution of load/unload technology

Load/unload (L/UL) has recently replaced contact start-stop (CSS) technology in major segments of the hard disk-drive (HDD) industry. Although L/UL has existed since the earliest HDDs, recent implementations use fixed ramp L/UL systems, which are considerably simpler than earlier versions. L/UL offers multiple advantages over CSS, including practically unlimited start-stop cycles and improved shock robustness. However, disk damage can occur in L/UL drives due to head-disk contacts, and a variety of parameters including vertical L/UL speed and slider corner radius should be optimized to minimize damage. Tight control of key tolerances is essential to maximize available disk real estate and minimize the required disk spacing to accommodate L/UL. Power-off retract systems for L/UL must produce higher retract torque than those for CSS designs, leading to new retract circuit designs.