Copper coatings were deposited on monocrystalline Si substrates using a magnetron discharge with a liquid cathode in the metal vapour plasma. During the deposition, the bias voltage in the range from...

We examined the feasibility of alumina substrate metallization by magnetron deposition of copper coatings with thickness of several tens µm for its prospective applications in production of ceramic PCBs and packaging. The films were prepared in magnetron sputtering systems with cooled and thermally insulated (hot) targets. Substrates with different geometries were used, including those with through-holes. Thickness, adhesive properties, and electrical resistivity of produced coatings were analyzed. If the film thickness exceeded ~20 µm, we observed its systematic delamination, unless the dedicated Cu_xO_y sub-layer of was introduced between the substrate and the main Cu film. Intermediate copper oxide films were investigated separately by SEM, EDS, and XRD methods, and deposition conditions for predominant growth of favorable tenorite CuO were determined. Prepared composite two-layer CuO + Cu coatings with total thickness of ~100 µm demonstrated good adhesion to alumina substrates in scratch-testing and performed much better than Cu-only films both in soldering and thermal cycling tests. We discuss an approach for constructing a reliable metallizing coating by plasma-assisted PVD methods that could be beneficial for complex-shaped ceramic PCBs and packaging.

Tungsten fuzz layers formed on the plasma-facing material surfaces of thermonuclear facilities due to helium ion irradiation are known to promote the initiation of electrical discharges on the first wall. Previous studies have indicated increased arcing probability under helium ion irradiation in steady plasmas with increasing ion energy to several hundred eV. Here, we experimentally consider the growth of nanostructures on tungsten surfaces in an RF He plasma and the spontaneous initiation of arcs when applying the pulsed bias voltage to the sample, up to several keV. The arc current and voltage waveforms were obtained, and the scanning electron images of the arc traces were analyzed. The behavior of the arc at the smooth/fuzzy surface boundary directly demonstrated the beneficial arcing conditions of the nanostructured layer. The proposed approach of pulsed biasing enables controlling the amount and duration of arcs for better analysis of their dimensions and dynamics. From the experimental results, the total arc trace length and arc velocity were calculated and compared with literature data, giving a good agreement both between experiments and theoretical data and between experiments in different arc initiation conditions.