Preparation and Characterization of Fibrous Copper Powder Used for Conductive Filler

A novel two-stage process is investigated for preparing the fibrous copper powder used for conductive filler in conductive paste. Based on thermodynamic simulation of Cu(II) — C2O42- -NH3 — NH4+ — H2O system, the rod-shape copper oxalate salt is synthesized firstly with coordination precipitation method, using ammonium oxalate and a purified copper salt solution which could be from either primary or secondary copper-bearing resources. According to the results of XRD, element analysis and X-ray single crystal diffraction, it can be inferred that the composition of the copper oxalate salt is [Cu(NH3)3]C2O4 • xH2O, and the NH3 plays a significant role in the formation of rod-shape crystal. Secondly, the copper oxalate salt is decomposed to fibrous copper powder at 350°C in inert atmosphere. The thermo-decomposition procedure is characterized by TG-DSC-FTIR, XRD and SEM. It is found that the phase of copper oxalate salt transforms as following: [Cu(NH3)3]C2O4 • xH2O→ [Cu(NH3)3]C2O4→ CuC2O4→Cu.