Cold gas spraying of copper and tin onto metallic and non metallic substrates

• Main Author: Calla, Eklavya
• Published: University of Nottingham 2005
• Subjects: 669; TS Manufactures
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485535

Cold gas dynamic spraying (CGDS) is a recent development in the field of thermal spraying in which a powder feedstock can be deposited onto a substrate to form a coating without it being heated significantly. The aim of the present study was to investigate the potential for manufacturing electrical circuits for automobile applications by depositing copper tracks on non-metallic substrates. Powders were sprayed using He gas at room temperature and elevated temperatures onto a number of different polymers, ceramic and metal substrates to understand the factors controlling deposit formation and the development of adequate adhesion between track and substrate. The use of tin as an interlayer to improve adhesion was a novel development in this study. The deposits were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), profilometry, microhardness, tensile testing, adhesion testing and resistivity measurements. Investigations were also performed to study thermal stability since as sprayed deposits are in non-equilibrium state. Copper could be deposited on aluminium for a wide range of deposition parameters. Sprayed copper had nanometre size grains and demonstrated high hardness and tensile strength. Annealing resulted in recrystallization and grain growth and decrease in hardness and tensile strength. Copper could be deposited on polymers like nylon (PA66), glass reinforced nylon (PA6T) and poly (butylene terepthalate) (PBT). Copper could be deposited on a wide range of polymers when a layer of tin was deposited as a bond coat. The use of tin bond coat improved the overall adhesion of tin + copper tracks. Intermetallic compound formation was observed in tin - copper tracks after annealing at 343 K and 443 K. The formation of the intermetallic compound did not increase the resistance of tin - copper couples as the resistance of the couples after annealing were found to be below that of the as - sprayed couples where the intermetallic compound formation had not taken place. This effect is a result of the recovery/recrystallization taking place in copper which reduces the resistance.