Binder jetting is a promising route to produce complex copper components for electronic/thermal applications. This paper aims to lay a framework for determining the effects of sintering parameters on the final microstructure of copper parts fabricated through binder jetting.
The knowledge gained from well-established powder metallurgy processes was leveraged to study the densification behaviour of a fine high-purity copper powder (D50 of 3.4 µm) processed via binder jetting, by performing dilatometry and microstructural characterization. The effects of sintering parameters on densification of samples obtained with a commercial water-based binder were also explored.
Sintering started at lower temperature in cold-pressed (∼680 °C) than in binder jetted parts (∼900 °C), because the strain energy introduced by powder compression reduces the sintering activation energy. Vacuum sintering promoted pore closure, resulting in greater and more uniform densification than sintering in argon, as argon pressure stabilizes the residual porosity. About 6.9% residual porosity was obtained with air sintering in the presence of graphite, promoting solid-state diffusion by copper oxide reduction.
This paper reports the first systematic characterization of the thermal events occurring during solid-state sintering of high-purity copper under different atmospheres. The results can be used to optimize the sintering parameters for the manufacturing of complex copper components through binder jetting.
Authors would like to acknowledge the “Functional Sintered Materials (Funtasma)” Interdepartmental Laboratory of Politecnico di Milano, where this research activity was developed. Support by the Italian Ministry for Education, University and Research through the project Department of Excellence LIS4.0 (Integrated Laboratory for Lightweight e Smart structures) is also acknowledged.
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Romano, T., Migliori, E., Mariani, M., Lecis, N. and Vedani, M. (2022), "Densification behaviour of pure copper processed through cold pressing and binder jetting under different atmospheres", Rapid Prototyping Journal, Vol. 28 No. 6, pp. 1023-1039. https://doi.org/10.1108/RPJ-09-2021-0243
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