Qed Technologies International, Inc.

Cabot Microelectronics Corporation

Qed Technologies, Inc.

Sergei Gorodkin

William Kordonski

Arpad Sekeres

Eric Oswald

Keith Beadle

Michael Natkin

A magnetorheological fluid for use in magnetorheological ultrasmooth polishing of a substrate surface, comprising an aqueous carrier vehicle; a first amount of magnetic particles having a average diameter between about 1 micrometer and about 2 micrometers; and a second amount of abrasive particles having an average diameter between about &#x3c;1 nanometer and about 15 nanometers. The fluid may further comprise a chemical stabilizer. Preferably the size of the magnetic particles is 2 to 3 orders of magnitude greater than the size of the abrasive particles. Preferably, the magnetic particles are spherical and include carbonyl iron, and preferably, the abrasive particles are selected from the group consisting of aluminum oxide, zirconium oxide, cerium oxide, silica, boron carbide, silicon carbide, natural diamond, synthetic diamond, and combinations thereof.

Magnetorheological fluid for ultrasmooth polishing

A system for sensing and controlling concentration of magnetic particles in magnetorheological fluid comprising a wire coil and an AC voltage generator that, when energized, creates a magnetic flux field including a fringing field. When the fringing field extends through the magnetorheological fluid, the impedance in the circuit is proportional to the concentration of magnetic particles. A reference wire coil identical to the sensing wire coil is connected therewith. A demodulator is connected to each of the coils sends an impedance difference signal to a feedback controller connected to controllable dispensing apparatus for adding a calculated amount of replenishing fluid to the magnetorheological fluid. The system may be incorporated into an integrated fluid management module having apparatus for receiving and replenishing spent magnetorheological fluid and a sensor system in accordance with the present invention for use in a magnetorheological finishing system having a carrier wheel.

Method and apparatus for measurement and control of magnetic particle concentration in a magnetorheological fluid

A system for magnetorheological finishing of a substrate. An integrated fluid management module (IFMM) provides dynamic control of the rheological fluid properties of the MR fluid on a conventional MR finishing apparatus, and dispensing of the fluid to the wheel. A magnetically shielded chamber charged with MR fluid is in contact with the carrier wheel. A transverse line removes the spent MR fluid from the wheel as the ribbon leaves the work zone. Replenishment fluid is added to the chamber via a dripper, and preferably an electric mixer agitates MR fluid in the chamber. A grooved magnetically-shielded insert at the exit of the chamber forms a polishing ribbon on the carrier wheel as the wheel is turned. A sensor sensitive to concentration of magnetic particles provides a signal for control of MR fluid properties, particularly, water content in the MR fluid. Means is provided for cooling fluid within the chamber.

System for magnetorheological finishing of substrates

A system for dispensing magnetorheological fluid to an MR finishing machine includes a pump for pressurizing the system; a first magnetic valve for regulating MR fluid flow by magnetically varying the structure and apparent viscosity of the fluid through a first flow passage; a similar second magnetic valve magnetically controlling a second flow passage in line with the first valve and flow passage; a pressure sensor disposed between the first and second valves; and an electronic control means. MR fluid flow through the system is controlled to a predetermined flow rate solely by the first valve. When the second valve is deactivated, a reference pressure is determined and saved. When the second valve is activated, a second pressure is determined and saved. From the pressure difference, the solids concentration of the fluid is determined, and a computer algorithm adds a calculated amount of water to the fluid reservoir as needed. The second valve is deactivated, and the measurement cycle is repeated, as may be desired.

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Rochester, NY, United States of America

Sergei Gorodkin