MAKE:TNT Tools 'n' Tips

"Cold Heat" Soldering Iron

by Bob Scott

As seen in MAKE 02 Toolbox


Tool photo.

"As Seen on TV!" When shopping for quality electronics tools, that's the logo I look for. I was both intrigued and skeptical when I saw this marker-sized gadget in an electronics catalog, along with a brief description that indicated it soldered, while remaining cool to the touch, using just four
AA batteries.


Of course, I had to take it apart to see what was inside. About what you'd expect for 20 bucks: some simple battery holders, snap-fit parts, etc. But, interestingly enough, it also contained a small circuit board complete with an IC that had obviously been "sterilized" by having its markings sanded off.


Equally interesting was the removable soldering tip. Apparently composed of a hard carbon compound, the tip is forked into two electrically isolated tines. To solder, the two tines are shorted across the joint. This allows a large current to flow across the "short," electrically heating it until it's hot enough to melt solder.


The combination of the mysterious circuit and the unusual tip do manage to slam a lot of current through the junction, as witnessed by the impressive spark you get when a good connection is made. Making that connection is critical to the process, and the iron has a dedicated LED that illuminates to indicate that you've hit the mark.


Does it work? Yeah, kinda. The Cold Heat iron seems best suited for small- to medium-sized connections that are mechanically solid and well supported. The pressure required to achieve and maintain a good electrical contact is considerably more than I was used to. I found myself chasing my victim components around the bench until I learned to lock them down before trying to solder them with the Cold Heat iron.


Bottom line: A good buy at the price and handy for your portable tool kit. Since it uses alkaline cells, it's always ready to go, unlike NiCad-powered irons I've owned, which seemed to alternate between dead-from-self-discharge and dead-from-overcharging with no stops in between. The Cold Heat iron is ready to solder quicker than a gas-powered iron, and it cools down seconds after use. If you need a portable iron, the Cold Heat is worth a look, but I wouldn't think of replacing my bench iron with it.

Radioshack stores and online sources.