Changes

The group of single contacts includes contact rivets, contact tips, and formedparts such as weld buttons. Contact spheres (or balls) are today rarely usedbecause of economical considerations.

For special cases, especially high surrounding temperatures with high thermaland mechanical stresses during switching operations, a full metallurgical bondbetween the contact rivet and the contact carrier may be required to prevent aloosening of the connection and early failures of the device. To accomplish thissuperior bond a thin layer of brazing alloy is added to the underside of the headand the rivet shank. During assembly a thermal treatment is added after themechanical staking.

For certain applications contact rivets with non-ductile or brittle materials suchas tungsten, silver–tungsten, or silver–graphite are required. Rivets with thesecontact materials can only be fabricated by brazing. Small round tips are brazedto pre-fabricated copper or steel bases using special brazing alloys in areducing atmosphere.

Flat or formed contact tips, welded or brazed to contact carriers, are frequently used in switching devices for higher power technology. Depending on thecontact material and specified shapes these tips are produced by various manufacturing processes. The most frequently used ones are: