Materials for electronics by thermal spraying

In this paper, dielectric and conductive properties of thermally sprayed Al₂O₃- and Cubased coatings on steel and alumina substrates were studied. Alumina powders with nano- and micro-sized additions of Ni, NiO, TiO₂, silica, and commercial glass were used in High Velocity Oxygen Fuel (HVOF) deposition. The conventional commercial copper powder and three Ag, WC and H₂ -modified powders were used in Direct Write Thermal Spray (DWTS) deposition. Mixed phases of α-Al₂O₃ and γ-Al₂O₃ were found to be present in the as-deposited coatings. Sprayed alumina-based composites exhibited dielectric permittivity of 5.3-13.9 and losses of 0.002-0.178 at 1 MHz and 1 GHz while the additions tend to increase the values. Sprayed compositions with glasstype additions were found to retain α-Al₂O₃ crystalline phase after the deposition. Cu depositions, especially modified ones, realised by Direct Write Thermal Spray (DWTS) showed conductivity values as high as 42-56% of IACS values. The results demonstrate that ceramic and conductive coatings fabricated by thermal spray techniques show feasible properties for electrical applications, such as low-frequency components and insulation layers to be utilised in embedded 3D circuitry, in a way that is not possible through traditional manufacturing methods.