Deoxidation behavior of boron in the production of C10200 oxygen-free copper: Effects on microstructure and material properties

ABSTRACT Oxygen-free copper is widely used in power electronics, high-power modules, aerospace applications, and other advanced technologies. Currently, oxygen-free copper is primarily produced via phosphorus deoxidation, which negatively impacts the electrical and mechanical properties, as well as the adhesion of the high-temperature oxide layer, thereby limiting the broader application of oxygen-free copper. In order to overcome the negative effects of phosphorus deoxidation in preparation of oxygen-free copper, it is proposed to replace phosphorus deoxidation with boron to eliminate the harm of phosphorus deoxidation in preparation of oxygen-free copper.This study investigates the production of oxygen-free copper using boron deoxidation for ceramic copper-chad plates, focusing on the deoxidation behavior of boron in copper melts and the influence of residual boron on the microstructure and properties of copper. The results show that boron can reduce the oxygen content in copper from 643 ppm to below 10 ppm. Boron primarily removes oxygen from [Cu 2 O] in the Cu–B–O melt, and the relationship between oxygen and boron concentrations in copper follows the Boltzmann model. As boron content increases in oxygen-free copper after deoxidation, the average grain size and electrical conductivity decrease. The relationship between average grain size and boron content adheres to the Boltzmann model, while the relationship between conductivity and boron content follows a logistic model. Tensile strength and elongation of copper initially increase and then decrease; the fracture mode of copper shifts from dimple fracture to brittle fracture and, ultimately, to a mixed dimple-brittle fracture. When the oxygen content of copper is 10ppm and the residual boron content is 150ppm, the comprehensive properties of oxygen-free copper are the best, the tensile strength is 156.7MPa, the elongation is 41.58%, and the conductivity is 97.98 IACS%. Boron enhances copper’s strength via solid solution-strengthening as an interstitial element.