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Localized Oxide Clamp Ring

IP.com Disclosure Number: IPCOM000013448D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 38K

Publishing Venue

IBM

Abstract

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.

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Localized Oxide Clamp Ring

    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.

    The attached diagram (Fig. 1) describes the concept. The rings are stacked together to form a tube, clamped tightly and then the hot wash water pumped down the center bore of the tube. In this manner only the inner clamp surfaces away from the drive mechanism are exposed to the hot wash water.

    However there are several problems with this approach. The cross sectional geometry of the rings is such that they do not seal against each other to prevent leakage of the hot water to the outer surfaces. This can be seen for the normal stacking in the upper left hand drawing of Fig 1. If t...