Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1999-06-24
2001-04-24
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S728000, C118S730000, C204S298280
Reexamination Certificate
active
06220203
ABSTRACT:
BACKGROUND INFORMATION
The present invention relates to a device for coating bulk material. A device for coating bulk material is described in East German Patent No. 25 75 54, which describes a device that includes a rotating holder for accommodating bulk material to be coated, as well as a plasmatron sputter source arranged within the rotating holder. The plasmatron sputter source is directed downward, such that the bulk material to be coated always stays within its sphere of action during the rotation of the rotating holder. Located on the inner wall of the rotating holder are control devices which ensure good intermixture of the bulk material during the rotation. The device allows the manufacture of single-layer metallic coatings having average adherence. The device does not possess means for producing layers having specific predefined properties. Thus, in particular process steps for increasing the adherence of an applied coating, or the production of multilayer systems, are not shown.
Another vacuum bulk-material coating device, in which the bulk material to be coated is moved in a rotating holder about a coating source, is described by the German Patent No. 42 09 384. Used here as the coating source is an electron-bean vaporizer which—subject to the principle—acts upwards. To produce high-quality coatings, also located in the interior of the rotating holder is a plasma or ion source whose direction of action is rotated by approximately 120 degrees with respect to the electron-beam vaporizer. For the coating process, the rotating holder is set into fast rotation. The centrifugal force occurring in so doing holds the bulk material to be coated against the inner wall of the rotating holder. The bulk material thus fixed against the inner wall of the rotating holder is conveyed in succession through the spheres of action of the electron-beam vaporizer and of the plasma/ion source. A stripping-off device engaging in the upper area of the rotating holder loosens the bulk material from the inner wall, and thereby constantly changes the position of the bulk material to be coated. This device permits coatings to be produced having different properties according to the present invention. However, the necessary rapid rotation of the rotating holder, in conjunction with the stripping process engaging in a correspondingly hard manner, leads easily to damage of the components to be coated. Therefore, particularly in the case of components having many edges, one must be prepared for a high rate of reject material.
To bring about specific physical properties for a coating, it is furthermore known (from German Published Patent Application Nos. 42 39 843 and 43 43 354) to carry out the coating process, while adding reactive gases in variable concentrations. However, known coating devices of this type are restricted to the coating of stationary objects, and do not allow coating of bulk goods.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a coating device which makes it possible to provide small parts, as bulk material, with coatings all-round having physical properties that are specifiable within a wide framework.
With the aid of the device of the present invention, the economic efficiency of coating components improves considerably. This holds true in particular for coating with layers to be applied in several process steps and the production of multilayer coatings. The device according to the present invention makes it possible to produce a multitude of different coatings with a single device. Because of the slow rotational speed of the rotating holder, the risk of damaging the components to be coated while rotating is small. The incorporation into the rotating holder of a device for producing a cleaning plasma is advantageous for achieving a high coating quality. By removing foreign materials before the actual coating, it assures high adherence of the applied coatings.
Advantageously, an ECR (electron-cyclotron-resonance) plasma is used as cleaning plasma. To produce it, a magnet arrangement and a microwave coupling device are located in the interior of the rotating holder. The microwaves emanating therefrom interact resonantly with those electrons in the magnetic field whose gyration frequency matches the microwave frequency. Advantageously located outside of the rotating holder, but within the vacuum device, is furthermore a heating device, by which the components to be coated are outgassed before the start of the coating process. In addition, applied expediently to the rotating holder is a voltage, by which the bulk material to be coated is brought to a negative potential. In this manner, the flow of positive ions in the direction of the bulk material is increased, whereby the quality of the coatings produced, as well as the cleaning and coating speed can be specifically influenced. By suitable restrictors, the coating area can be restricted to the surface of the components to be coated, an undesired coating of the rotating-holder inner surface being prevented.
To achieve particularly hard coatings, it has proven advantageous to deposit the coatings, accompanied by simultaneously burning ECR plasma.
REFERENCES:
patent: 5470388 (1995-11-01), Goedicke et al.
patent: 6090247 (2000-07-01), White et al.
patent: 257 554 (1988-06-01), None
patent: 42 09 384 (1993-04-01), None
patent: 42 39 843 (1994-06-01), None
patent: 43 43 354 (1995-06-01), None
patent: 44 22 688 (1996-01-01), None
patent: 5-271921 (1993-10-01), None
“Sputter Cleaning And Plating Small Parts”, Mattox and Rebarchik, Electrochemical Technology, vol. 6, No. 9-10, pp. 374-375, Sep. 1968*.
“A Simple And Inexpensive Rotating Barrel To Ion Plate Small Components”, Ahmed and Teer, Journal Of Physics and Scientific Instruments, vol. 17, No. 5, pp. 411-416, May 1984*.
Burger Kurt
Reuter Wolfgang
Voigt Johannes
Alejandro Luz
Kenyon & Kenyon
Mills Gregory
Robert & Bosch GmbH
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