Changes

Clad materials consist of two or more layers of different materials, the contactmaterial and the carrier, which are firmly bonded to each other. Depending onthe electrical requirements the contact material is mainly an alloy of gold,palladium, or silver based while the carrier material are mainly copper alloys. Tobond these materials various technologies are utilized, the two most importantones being described in more detail below.

During ''hot cladding'', the classic process, the materials to be clad areassembled into a cladding package in block or plate form, heated to about800°C and clad (or “welded”) together under high pressure <xr id="fig:Hot_cladding_of_pre-materials"/>(Fig. 3.3). At theinterface between the two materials a non-separable bond is formed by eitherdiffusion of the reaction partners or in liquid phase by forming a AgCu eutecticalloy when an additional brazing alloy foil is placed between the two materials.Further processing is done by rolling with required annealing steps betweensubsequent thickness reductions. The disadvantage of this process is theusually limited short length of final material strips.

When specifying the contact material layer thickness it is recommended to use theminimum required thickness.

Strength properties and dimensional tolerances of clad contact bi-metals arederived from the standards DIN EN 1652 and DIN EN 1654 for Cu alloys. Whenspecifying the width of the contact material layer it is recommended to use theminimum required value. All dimensions should be specified originating from onestrip edge.