Ultra Clean Technology Systems and Services Inc.

Sowmya Krishnan

Tadahiro Ohmi

An improved method for welding and passivation forms a chromium oxide passivated film over the welded portion during the welding process. In a shielding step, a backshield gas, preferably argon, is flowed around the welding site. In a welding step, an arc gas, preferably argon with approximately 10% hydrogen and less than 1 ppm moisture content, is flowed through the welding head and a welded joint is formed, for example by high speed tungsten-inert gas (TIG) orbital welding. In the passivation step, a process gas, preferably argon with approximately 30-100 ppm of oxygen and less than 1 ppm moisture content, and preferably less than 1 ppb moisture content, is flowed over the welded portion to form a chromium oxide passivated film on the welded portion. The process gas is passed through a gas purifier prior to being flowed over the welded portion to maintain its moisture level at less than 1 ppb. A welding and passivation apparatus for carrying out the improved method is also described having a welding system, such as a high speed tungsten-inert gas (TIG) orbital tube welding system or the like, and a gas supply system equipped to deliver the backshield gas, arc gas and process gas with the required compositions and with the proper timing during the welding and passivation process. An electronic timing unit controls the gas supply system to release the gases into the welding head at the proper time during the process.

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Sunnyvale, CA, United States of America

Sowmya Krishnan