Brazing is the primary method of joining parts in high-power electronic devices.
Brazing is not immediately associated with electronics applications, but it is, in fact, the major means of joining parts in high-power, free-electron devices, such as traveling wave tubes, magnetrons and klystrons. The range of special materials, braze alloys and brazing techniques used to manufacture a single device is larger than what most brazing engineers would encounter in their entire careers.
Free-electron devices are used in such products as marine radars, industrial cookers, television transmitters and cancer treatment equipment. These devices are so complex that most assemblies are brazed in multiple steps. Although four or five steps are typical, some assemblies need as many as nine, with brazing temperatures ranging from 2,000 C for molybdenum-ruthenium assemblies to 780 C for eutectic copper-silver assemblies. Braze alloys with low melting points are not used, because they usually contain elements that would vaporize in the vacuum and temperature conditions inside the devices. This could contaminate sensitive components. The same problem limits the form of the braze alloy to preforms cut from wire or thin sheet.
For high-volume production, a mesh-belt furnace with a nitrogen-hydrogen atmosphere is a good technique. Other brazing methods include pusher and bell furnaces with atmospheres ranging from 5 percent hydrogen to 100 percent hydrogen; vacuum furnaces with argon backfilling for improved cooling times; and induction brazing in a controlled nitrogen-hydrogen atmosphere. Which process to use depends on the materials and whether other joints in the assembly have already been brazed.