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Recycling of disks by liquid caustics

IP.com Disclosure Number: IPCOM000018952D
Original Publication Date: 2003-Aug-22
Included in the Prior Art Database: 2003-Aug-22
Document File: 1 page(s) / 4K

Publishing Venue

IBM

Abstract

Aggressive caustics like hydrochloric acid affect the composition and the surface of the glass substrate of a hard disk. So it is necessary to do further treatments on the glass substrate before it can be reused in the disk manufacturing (e,g. removal of some micrometers of glass material). This makes the recycling process more expensive and reduces the number of times the glass substrate can be recycled.

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Recycling of disks by liquid caustics

The glass substrates of defective disks are recycled by etching the disks with liquid -caustics containing hypochlorite (ClO ) or chloride (ClO2- ) or chlorate (ClO3- ) or -bromate (BrO3 ) or a mixture of the named ions. After washing with DI water the glass substrates can be reused.

    Aggressive caustics like hydrochloric acid affect the composition and the surface of the glass substrate of a hard disk. So it is necessary to do further treatments on the glass substrate before it can be reused in the disk manufacturing (e,g. removal of some micrometers of glass material). This makes the recycling process more expensive and reduces the number of times the glass substrate can be recycled.

    Some million dollars could be saved if the defective disks weren't simply destroyed.

    The caustics used in this solution are not as aggressive as the hydrochloric acid and the reaction mechanism seems to be different. So the glass surface is less influenced by the milder reaction conditions.

    A former solution solves the problem that aggressive caustics affect the composition and the surface of the glass substrate .by using a mixture of SO 2 / moisture and subsequent treatment in an ultrasonic bath with hot or boiling DI water. The disadvantage of this method is that parts of the sputtered layers (mainly the layer directly on the glass) remain on the substrate. A further polishing step is necessary. Our solution removes all sputtered layers (Tof-S...