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Magnetic Shield for Disk Drive Enclosure

IP.com Disclosure Number: IPCOM000014286D
Original Publication Date: 2001-Mar-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 3 page(s) / 49K

Publishing Venue

IBM

Abstract

Disclosed is a methodology for shielding the strong stray magnetic field created by the magnets used in the actuator of a hard disk drive. This strong magnetic field sometimes attracts nearby loose ferrous metallic objects towards the surface of the electronic card mounted on the disk drive enclosure, and cause electrical shorts, thereby disabling the disk drive operation. The magnetic shield reduces the stray magnetic field to a level where it does not easily attract nearby ferrous objects.

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Magnetic Shield for Disk Drive Enclosure

   Disclosed is a methodology for shielding the strong stray magnetic field created by the magnets used in the actuator of a hard disk drive. This strong magnetic field sometimes attracts nearby loose ferrous metallic objects towards the surface of the electronic card mounted on the disk drive enclosure, and cause electrical shorts, thereby disabling the disk drive operation. The magnetic shield reduces the stray magnetic field to a level where it does not easily attract nearby ferrous objects.

   With the ever increasing demand for higher performance from hard disk drives, the size and strength of magnets has been steadily increasing. At the same time, the need to keep the cost low has resulted in inadequate shielding of these magnets. A considerable amount of field leaks out of the magnet housing and disk enclosure. The strength of the magnetic field at the surface of disk enclosure can be as high as 400 Gauss. As detailed in the above paragraph, this magnetic field can indirectly cause drive failures. One methodology that has been used before to mitigate strong magnetic fields is to place a plastic cover on the pins of logic modules on the electronic card so as to prevent shorting of module pins in the event of any metallic object falling on the card, that has been attracted by the magnetic field. The main drawback of this methodology is that the shape and size of cover has to change to accommodate any change in module placement on the board. Also, once placed, the cover cannot be easily removed to troubleshoot the module. It also adds to the card assembly cost.

   The concept of using a magnetic shield to cut the magnetic field near the source is developed to overcome the drawbacks of using a plastic cover. When placed between the disk enclosure and the electronic card, the shield reduces the stray magnetic fields to an acceptable level. The magnetic field measured 10 mm above the disk drive form factor is about 66 Gauss. The goal is to reduce this field down to 25 Gauss. Initially, it...