Electrodeposition of metallic tungsten films in ZnCl2–NaCl–KCl–KF–WO3 melt at 250 °°C

WO3 hardly dissolved in ZnCl2–NaCl–KCl (0.60:0.20:0.20, in mole fraction) melt at 250 °°C. The solubility of WO3 increased by the addition of KF to the melt, which enabled electrodeposition of metallic tungsten. A smooth and fine film of metallic tungsten was obtained on a nickel substrate by the potentiostatic electrolysis at 0.06 V versus Zn(II)/Zn. The thickness reached ca. 2.5 μm after 6-h electrolysis. The surface of the nickel contact probe pin manufactured by the conventional LIGA (Lithographie-Galvanoformung-Abformung, German abbreviation) process was successfully coated with a smooth and adhesive tungsten film by using this melt.