although fundamental inventions came from bell labs, the inventions for manufacturing commercially viable tantalum electrolytic capacitors came from researchers at the sprague electric company. preston robinson, sprague's director of research, is considered to be the actual inventor of tantalum capacitors in 1954. his invention was supported by r. j. millard, who introduced the "reform" step in 1955, a significant improvement in which the dielectric of the capacitor was repaired after each dip-and-convert cycle of mno deposition, which dramatically reduced the leakage current of the finished capacitors.