Heating – Work chamber having heating means – Having means by which work is progressed or moved mechanically
Reexamination Certificate
2000-08-04
2001-12-11
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Having means by which work is progressed or moved mechanically
C432S064000, C432S128000, C432S205000
Reexamination Certificate
active
06328558
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for the control and exchange of the atmosphere surrounding materials to be treated.
2. Background and Prior Art
In the thermal processing of materials, especially various electronic components, by treatment with various reactive gases in high temperature furnaces, it is often necessary to purge the materials and their environment of gases, such as air, that may produce adverse reactions in the high temperature conditions of the furnace. To this end, various exhaust systems, scavenger chambers, and the like, have been designed for the purging of the materials prior to entry into the furnace or within the furnace, generally near the entry section of the furnace.
U.S. Pat. No. 4,992,044 to Phillipossian discloses a furnace for high temperature treatment of semiconductor wafers utilizing a scavenger arrangement for controlling gas flow.
U.S. Pat. No. 5,118,286 to Sarin discloses a method and apparatus for controlling gas flow patterns and avoiding the mixing of spent reactant gases with ambient air in the treatment of semiconductor wafers.
U.S. Pat. No. 5,645,417 to Smith discloses a thermal treatment of silicon wafers in a thermal processing furnace tube wherein the inner surface has a plurality of dimples thereon to promote a more turbulent flow of gases and a more uniform reaction across the surface of the wafers.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a chamber for containing a material to be treated that may be efficiently purged and the contained atmosphere exchanged and replaced by a selected atmosphere.
It is a further object to provide a purge chamber for controlling the atmospheric environment of materials to be subject to thermal processing.
It is a still further object to provide a purge chamber for the gaseous treatment of materials that may be operated as a stationary independent unit or in a cooperative arrangement with a unit for thermal processing.
It is a still further object to provide an open ended purge chamber for the gaseous treatment of a continuously moving product stream, prior to entry into kiln for thermal treatment.
It is a still further object to provide a purge chamber for the gaseous treatment of materials wherein the gases may be recycled.
It is a still further object to provide a purge chamber adapted for attachment to a furnace for the gaseous treatment of a moving product stream, prior to entry into or exit from a furnace for thermal treatment.
The above and other objects are achieved in accordance with the present invention, which comprises a purge chamber for providing a controlled gaseous atmosphere for the treatment of materials. The purge chamber comprises a housing having an entrance end and an exit end, means for conveying materials therethrough, gas inlets and outlets, and internal gas barriers to provide a controlled flow of gases within the housing. Within the housing, a first gas barrier and a second gas barrier may be positioned respectively near the entrance end and the exit end to inhibit the entry of unwanted gases and to define a purge region having a controlled flow of gases therethrough. The gas barriers are flexible physical barriers, preferably extending across the full width of the purge chamber and suspended from the upper portion of thereof. The gas barriers are flexible to allow the passage of material being conveyed through the chamber. Preferably, the gas barriers are in the form of flapper doors, spanning the width of the chamber and hingedly suspended from a supporting rack near the top of the purge chamber. As materials being conveyed through the chamber contact a flapper door, the door may be pushed up by the moving materials allowing the materials to pass. Alternatively, the gas barriers may be in the form of flexible strips, for example, plastic strips, or chains, or thin strips of metal foil, or the like. The strips may be arranged in multiple staggered rows and suspended from the upper region of the chamber, and sufficiently flexible to be pushed aside by the materials passing through and able to return to their original vertical orientation after the materials have passed. The gas barrier at the entry end and the exit end of the purge region aid in the maintenance of a slight positive pressure therein. Optionally, additional gas barriers may be present to further control the flow of purge gases and define additional purge regions within the purge chamber. In a preferred embodiment, the gas barriers, that is, flapper doors, flexible strips, or the like, are suspended from a removable frame mounted at the top of the purge chamber, so that the number and location of the doors, or gas barriers , can be conveniently modified to adjust to various process requirements. The frame may be supported on tracks or on hangers located in the upper portion of the interior of the purge chamber.
Positioned within the purge region, that is between the first and second gas barriers, are at least one purge gas inlet and at least one purge gas outlet to provide a cross-flow of selected gases to purge and replace the gases within the purge region. Additionally, positive pressure gas inlets are preferably positioned adjacent to the first and second gas barriers to provide a positive pressure at each end and act as a barrier to entry of unwanted gases from outside of the purge region.
The purge chamber of this invention may be operated as a batch unit for the gaseous treatment of materials. However, in a preferred mode, the purge chamber is provided with a means for conveying materials being treated through the chamber in a continuous fashion. Various conveyors or transport systems such as rollers, tracks, moving belts, and the like may be used for this purpose. One such transport system that may be employed is disclosed in U.S. Pat. No. 5,848,890 to McCormick. As a load of materials are conveyed through the chamber, the hinged flapper doors are pushed open by the moving load, allowing it to pass through.
The purge chamber may be of various sizes and shapes, the preferred shape being of rectangular cross-section with a height substantially less than the width, to enhance the cross-flow of gas. The length may vary considerably. In general, the longer the chamber, the more complete the gas purging that will take place.
The purge chamber may be operated as a “stand alone” unit for the gaseous treatment of materials or as an appendage or attachment unit for a furnace or other apparatus. For the latter purpose it is preferred that the entrance end and the exit end have means such as flanges for attachment to a furnace either at the entrance of the furnace, for a pre-treatment of the materials to be processed or at the exit end of the furnace for a post-treatment, or both. When the chamber is attached to a furnace, the transport means, e.g. moving belt, etc. may be cooperatively connected to transport mechanism within the furnace for continuous transport of the materials through the chamber and through the furnace.
The purge chamber may be operated at various temperatures. The operating temperature will typically be between about room temperature and about 200° C. Various materials of construction may be employed, including for example, steel, graphite, plastic or the like, depending on the temperature and other process conditions to be applied.
REFERENCES:
patent: 3778221 (1973-12-01), Bloom
patent: 4238122 (1980-12-01), Synder et al.
patent: 4397451 (1983-08-01), Kinoshita et al.
patent: 4627814 (1986-12-01), Hattori et al.
patent: 6074202 (2000-06-01), Yagi et al.
Dover Bruce J.
McCormick Edward V.
Weide Carl Vander
Cookfair Arthur S.
Harper International Corp.
Wilson Gregory
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