Liquid purification or separation – Processes – Using magnetic force
Reexamination Certificate
2000-03-16
2001-07-24
Reifsnyder, David A. (Department: 1723)
Liquid purification or separation
Processes
Using magnetic force
C210S767000, C210S806000, C210S223000, C451S088000
Reexamination Certificate
active
06264843
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for reclaiming a suspension which is produced during the machining of semiconductor material and contains a liquid, a substance with an abrasive action and abraded semiconductor material, by separating off the substance with an abrasive action and then separating the liquid and the abraded material.
2. The Prior Art
U.S. Pat. No. 5,830,369 describes a process of this type and according to this document, a centrifuge is to be used to separate the abraded material and the liquid.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a simpler, less expensive process.
This object is achieved according to the present invention by means of a process for reclaiming a suspension which is produced during the machining of semiconductor material and contains a liquid, a substance with an abrasive action and abraded semiconductor material, by separating off the substance with an abrasive action and then separating the liquid and the abraded material. The liquid and the abraded material are separated with the aid of a magnetic separator.
The present invention is suitable in particular for reclaiming a suspension which is produced when cutting semiconductor wafers from a hard brittle material using a wire saw or when lapping such semiconductor wafers.
The present invention is surprising since it was impossible to expect that abraded nonmagnetic material such as semiconductor material would be suitable for separation with the aid of a magnetic separator. It has been discovered that abraded nonmetallic material, for example abraded silicon-containing material, forms magnetizable agglomerates with abraded metal-containing material from, for example, the sawing wire of a wire saw or a lapping plate.
The present invention makes it possible to dispense with complex removal of abraded material by centrifuging.
REFERENCES:
patent: 4810368 (1989-03-01), Seider et al.
patent: 5529695 (1996-06-01), Gwozdz
patent: 5772900 (1998-09-01), Yorita et al.
patent: 5830369 (1998-11-01), Toyama
patent: 195 35 397 (1997-03-01), None
patent: 2 704 455 (1994-11-01), None
English Derwent Abstract AN 1997-193730 [18] Corresp. to DE 195 35 397.
Derwent Abstract 1996 27033 1 [28] for FR 2 704 455.
Patent Abstracts of Japan, vol. 1999, No. 02 Feb. 26, 1999 & JP 10309647 A (Tadco Corp., Nov. 24, 1998.
T. J. Drozda, (Wick: “Tool and Manufacturing Handbook, vol. 1, Machining”, 1983 Society of Manufacturing Engines (SME) Deaborne(US), p 4-19), 34-39.
Collard & Roe P.C.
Reifsnyder David A.
Wacker Siltronic Gesellschaft für Halbleitrmaterialien AG
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