Brazing Chamber - November 2008

Brazing is defined by Wikipedia as:

"a metal-joining process whereby a filler metal is heated above and distributed between two or more close fitting parts by capillary action. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux. It then flows over the base metal (known as wetting) and is then cooled to join the two workpieces together. It is similar to soldering, except the temperatures used to melt the filler metal is above 450C, or, as traditionally defined in the United States, above 800F."

This application required brazing because the use of SST tube heaters in a vacuum could easily cause the heaters to burn themselves out at the operating temperatures required by this particular customer. In order to prevent this from happening, the heaters were brazed to a thick plate of copper in order to dissipate heat evenly over the surface. A powdered nickel alloy was used as the brazing material.