A new sputter cleaning system for metallic substrates

Abstract

In an experimental set-up for the gas discharge pretreatment of moving metallic substrates the efficiency of sputter cleaning was investigated with respect to planar magnetron discharges (PMDs) and conventional glow discharges (GDs). The substrate temperatures needed to deposit adhesive Ni films (5 μm) on steel in a high vacuum were taken as a measure of efficiency. As far as the substrate temperature, the sputtering of surface material, the processing speed, the specific power demand and the length of cleaning zones are concerned, the PMD pretreatment was shown to be superior to the GD treatment. To obtain films of good adhesion, the PMD treatment requires only 15% of the energy demanded by GD systems. This is attributed to the fact that, in a magnetron discharge, the ions are of low energy content and therefore they generate activated centres of enhanced bonding energy that are most prevalent in the surface region of the substrate. The initial drawbacks with reference to the uniformity of the PMD pretreatment have now been eliminated almost entirely. The results suggest that PMDs may be used to advantage in the pretreatment of metallic strip-type substrates.