Electric soldering iron having a PTC heating element

A soldering iron comprising:

• an elongated bit with a cone shaped bit tip and an elongated back body having a generally rectangular cross-section;
• a pair of heater assemblies sandwiching the back body of the bit so as to be in thermal contact therewith;
• lead wires coupled to said heater assemblies to supply power to the soldering iron;
• and
• a hand-grip coupled with the bit;
• each of said heater assemblies comprising a PTC thermistor having a positive temperature coefficient of resistance as a heater;
• means for pressing said heater assemblies against the back body of the bit with spring contact;
• the total contact area S.sub.1 between said PTC thermistors and said back body being 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 being in the range from 0.1 cm.sup.2 to 3.0 cm.sup.2.