Immediately before starting the S3B process, a mechanism pushes the double-wall container into mating with the lid. The S3B process is started by applying power to the induction-heating coil to melt the rings of brazing material, thereby causing the following events to occur simultaneously:
- The outer wall of the double-wall container becomes brazed to the interface structure, thereby ensuring maintenance of the separation between the clean and dirty environments.
- The inner wall of the double-wall container becomes brazed to the lid, thereby creating an inner container and hermetically sealing the sample into it.
- Once the through-the-thickness rings of brazing material melt, there is nothing left to hold the inner container to the outer container or to hold the lid to the interface structure. Consequently, the springs push the newly created hermetic container away from the outer container/interface structure, into the clean environment (see Figure 2).
The brazing material is chosen to have a sufficiently high melting temperature (typically >500 °C) so that the brazing process sterilizes the outer surface of the lid/wall seam region of the newly created hermetic container. The outer surface of the inner container is covered with a layer of thermal-insulation material to prevent heat damage of the sample during brazing. Alternatively, in an application in which there is no concern about biological contamination, it could be feasible to substitute a lower-melting-temperature solder for the brazing material.
This work was done by Yoseph Bar-Cohen, Tommaso P. Rivellini, James E. Wincentsen, and Robert Gershman of Caltech for NASA’s Jet Propulsion Laboratory. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Manufacturing & Prototyping category. NPO-41024
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Separation and Sealing of a Sample Container Using Brazing (reference NPO-41024) is currently available for download from the TSP library.
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