A Novel Fabricating a Thick Film Cu-Ni Alloy Resistor by Screen Printing an Al Electrode and Galvanic Replacement Reaction

In this study, a thick film copper-nickel alloy (Cu-Ni alloy) was fabricated by using a novel technique which combines thick film process and galvanic chemical replacement. First, a thick film Al electrode was screen printed and sintered at 600 °C on the aluminum oxide (Al2O3) substrate which served as a reactant. Sequentially, the Al electrode on Al2O3 substrate was immersed into a copper sulfate (CuSO4) solution at 40 °C for 15-30 min to carry out the first galvanic replacement reactions of the partial Al electrode into Cu. After which it was immersed into an NiSO4 solution 80 °C for 15 min to carry out the second galvanic replacement reactions of the remaining Al electrode into Ni to form Cu-Ni layers on the Al2O3 substrate. To make a thick film Cu-Ni alloy, the Cu-Ni layers on Al2O3 substrate were annealed at high temperatures for interdiffusion of Cu and Ni. A thick film Al electrode on an Al2O3 substrate is immersed into a CuSO4(aq) solution at 40 °C for 15 min and sequentially immersed in an NiSO4(aq) solution at 80 °C for 15 min. Then, after further annealing at 800 °C for 30 min in a reducing atmosphere, the Cu and Ni composition ratio in the thick film Cu-Ni alloy is approximately 1:1, reflecting Cu-Ni alloy resistor with a very promising temperature coefficient of resistance (TCR) performance (115 ppm/°C).