Localized Oxide Clamp Ring
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-18
In order for the thermal clamp ring to tightly grip the disk stack, there must be sufficient friction between the clamp ring and the motor. Typically this has been a problem area. Different batches of rings and motors will have different frictional properties. When the friction of either ring or motor was too low, micro-slippage would occur causing the "deflection" measurement to go out-of-spec. In order to minimize these variations, a process change was made several years ago wherein the temperature of the clamp ring wash water was increased so that a thin layer of aluminum oxide was produced on the outside of the clamp ring. The oxide increased the friction of the ring and reduced microscopic slippage between the ring and motor. Out-of-spec deflection measurements were eliminated. At the time, studies were done to verify that the oxide was sufficiently thin and sufficiently adhered to that it would not fall off and cause contamination problems. The oxide proved to be a robust solution to minor frictional variations in the clamp ring and motor. However with increased areal density of the disk drives, previously acceptable contamination from the oxide began giving problems. The oxide is only required on the inner surface of the ring where it contacts the motor. Any oxide which should come loose from the inner surface will be safely entrapped between the ring and the motor. However the oxide on the remaining surfaces is exposed to the drive mechanism itself, and any oxide particles falling off will distribute around the interior of the drive as contamination. It is proposed to apply the oxide only to the inner ring surfaces which shielding the outer surfaces from oxidation.