Electric soldering iron having a PTC heating element

摘要

A soldering iron is heated by electric resistance heating elements comprising barium titanate PTC thermistors. The soldering iron has an elongated copper bit with a cone shaped bit tip and an elongated back body having a generally rectangular cross section coupled to the bit tip. A pair of flat PTC thermistor heater assemblies sandwich the back body of the bit and are in thermal contact therewith. The heater assemblies are pressed against the back body of the bit with spring contact. A hand-grip is coupled with the bit. The total contact area S. sub.1 between the PTC thermistor heater assemblies and the back body is in the range from 1.0 cm.sup.2 to 25 cm.sup.2 and the transverse cross sectional area S.sub.2 of the back body is in the range from 0.1 cm.sup.2 to 3.0 cm.sup.2.