In slim 2.5″ HDDs with 5mm or 7mm-height, the mechanical structure has to be simplified and all of the axial dimensions have to be miniaturized. It results in too flexible HDDs which is vulnerable to external force Especially, the rotating hub is so thin and flexible to make contact with stationary sleeve by clamping force.
In this paper, we investigated the mechanical contact between the rotating hub and stationary sleeve of a 2.5″ HDD with 5 mm-height at low rotating speed. And we checked upper thrust surface in hub and sleeve after tearing down the FDBs. Circumferential scratch is observed on the upper thrust surface of sleeve and hub due to mechanical contact. Hub deflection due to disc clamping force was identified as a source of mechanical contact between rotating hub and stationary sleeve. To prevent mechanical contact between them, we proposed a robust design of hub and validated the proposed design theoretically and experimentally.