ColdHeat Infomercial - Early 2000's
Infomercial for the Cold Heat soldering iron - broadcast in the early 2000s
ColdHeat was an American company founded to develop and market products using the proprietary graphite-like compound Athalite. The composite material is claimed by the manufacturer to have the unusual ability to conduct large amounts of heat and return to room temperature in a short amount of time.
The first two products were soldering irons powered by alkaline batteries. The manufacturer claims this soldering iron is unique in that its Athalite tip undergoes a temperature change from ambient temperature to approximately 800 °F (427 °C) and back to ambient within three seconds when the tip is removed from the work.
The tip of this apparatus is split into two sections that complete an electrical circuit when a low electrical resistance is placed across the tip; e.g. metallic contacts, or solder. With a current flowing, the resistance of both the solder and the tip produces enough heat to increase the temperature beyond the melting point of the solder. For the light-duty work it was designed for, the Athalite tip heats just enough and can cool very rapidly; however, if applied to something with a large thermal capacity such as a metal chassis, the tip can become extremely hot and can take over a minute to cool in an extreme case.
It is thought that the irons cannot be used indiscriminately for all work; the voltage across and current through the tip can damage electronic circuits being soldered. When not in contact with a joint, the split-tip has 6 or more volts across it, enough to destroy semiconductor p-n junctions on contact if the iron accidentally touches multiple closely spaced pads. This is not static-electricity damage; any voltage over about 0.7V capable of delivering a high current can destroy a semiconductor junction.
It's a common misunderstanding that a high current in the joint causes heat. The heat is generated by resistance within the tip. Heat is then conducted to the joint just as in traditional solder tools. Also, the current in the joint is limited to the small region between the two tip halves and doesn't pass through the part being soldered. There is a tiny transient voltage when the tool is applied or removed, but it is orders of magnitude below the levels that cause static-electricity damage.