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 (Al ₂ O ₃ ) substrate which served as a reactant. Sequentially, the Al electrode on Al ₂ O ₃ substrate was immersed into a copper sulfate (CuSO ₄ ) 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 NiSO ₄ 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 Al ₂ O ₃ substrate. To make a thick film Cu-Ni alloy, the Cu-Ni layers on Al ₂ O ₃ substrate were annealed at high temperatures for interdiffusion of Cu and Ni. A thick film Al electrode on an Al ₂ O ₃ substrate is immersed into a CuSO ₄ (aq) solution at 40 °C for 15 min and sequentially immersed in an NiSO ₄ (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).