Changes

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

For stamping sufficiently ductile semi-finished materials are needed. These aremainly silver, silver–alloys, silver–nickel, silver–metal oxide, and silver–graphite(with graphite particle orientation parallel to the switching surface). silver–metalSilver–metal oxides and silver–graphite need an additional well brazable or weldable silverlayer on the underside which can be bonded to the bulk of the contact materialby various processes. To further facilitate the final attachment process strips andprofiles are often coated on the brazing underside with an additional thin layer ofbrazing alloy such as L-Ag 15P (CP 102 or BCuP-5).For Ag/C with the graphite orientation perpendicular to the switching surface thebrazable underside is produced by cutting tips from extruded rods and burningout graphite in a defined thickness.

The press-sinter-infiltrate process (PSI) is used mainly for Ag/W and Cu/Wmaterial tips with tungsten contents of > 50 wt%. A silver or copper surplus onthe underside of the tip later facilitates the brazing or welding during finalassembly.

The press–sinter–re-press method (PSR) allows the economic manufacturing ofshaped contact parts with silver or copper contents > 70 wt%. This process alsoalloys parts pressed in two layers, with the upper being the contact material andthe bottom side consisting of pure Ag or Cu to support easy attachment.

Press–sinter processes are limited to smaller Ag/W contact tips with a Agcontent of approximately 65 wt%.

*Typical contact shapes of tips and formed contact parts (s. Picture <xr id="Typical contact shapes of tips and formed contact partsfig:Typical_contact_shapes_of_tips_and_formed_contact_parts"/>)<figure id="fig:Cold_bonding_of_bimetall_rivets">[[File:<figure id="fig:Typical_contact_shapes_of_tips_and_formed_contact_parts.jpg|right|thumb|Typical contact shapes of tips and formed contact parts]]</figure>

Because of the wide variety of shapes of contact tips and formed contact partsthe user and manufacturer usually develop special parts specific agreementson quality and tolerances.