Pretreatment of metallic substrates with the plasmatron

It is expected that ring gap discharges will increasingly gain in importance as a pretreatment technique for metallic substrates prior to vacuum deposition. Such a process not only allows proper gas desorption, sputter cleaning and setting of the substrate temperature but also provides adequate surface activation. An arrangement for the pretreatment of moving strip-type metallic substrates by plasmatron discharges is described. The most important data, i.e. the power density, the time of exposure or strip advance and the substrate temperature, for pretreating steel and aluminium substrates in order to obtain adhesive films of nickel, aluminium and copper are given. The energy efficiency of the arrangement for the cleaning and heating of metallic substrates is compared with that of conventional systems. Our investigations have shown that the efficiency of plasmatron pretreatment exceeds that of other known pretreatment processes for metallic substrates and that the attainable processing speeds meet even the highest demands dictated by the high evaporation rates of electron beam coating.