1. A soldering iron system with automatic variable temperature control comprising:a hand piece or robot arm including a soldering cartridge having a soldering tip, a coil that generates a magnetic field, and a temperature sensor for sensing a temperature of the soldering tip;
a variable power supply for delivering variable power to the coil to heat the soldering tip;
a processor including associated circuits for accepting a set temperature input and the sensed temperature of the soldering tip, and providing a control signal to control the variable power supply to deliver a suitable power to the coil to keep the temperature of the soldering tip at a substantially constant level of the set temperature input,
wherein the set temperature input is automatically adjustable by the processor based on one or more of a cartridge type, a tip type, a tip size, a tip shape, a thermal load type or size, and a quality of a soldering joint being formed by the solder tip and determined by the processor.