http://www.google.com/custom?q=cold+hea...00FF%3BGIMP%3A0000FF%3BFORID%3A1&hl=en
Answer:
Apparently, it works.
The claims for the Cold Heat irons are plausible, if the tip's tiny and has very little thermal inertia. That means the heating element has to react very quickly to stop the tip temperature from diving every time you apply solder to it, but that's not a technical impossibility either, for light duty work. You're not going to be making any stained glass windows or sweating any copper pipes with it, but most modern electronic soldering work can be done with a very low power iron. It's tip temperature maintenance that matters, not brute power. My big Portasol Superpro has to be handled very carefully if I want to avoid lifting tracks off circuit boards.
(A reader's now pointed out to me, though, that it's perfectly possible to scorch circuit boards with a Cold Heat. Another couple of readers have contributed their opinion that it's pretty hard to get any real work done with one of these things, if you're working on circuit boards at least. One reader e-mailed me at the end of 2004 to say that he likes his, though; he says you have to keep it in contact with heavier gauge wire for a little while to get it to work. He didn't mention trying to solder small components.)
I guess I'll never know, though, because the Cold Heat people twice promised to send me an iron for review last year, but never did.
Cold Heat continued
In your last Lettuce column, you mentioned the Cold Heat soldering tool.
I thought you knew 99% of Everything, but, from the sounds of it, you don't know the secret of the tool.
The tip is made from a graphite-like electrically conductive material, built in two halves, electrically isolated from each other.
Current is passed into the joint, almost instantly making it hot enough for conventional-alloy solders. As you know, graphite (unlike certain other carbon allotropes) has relatively poor thermal conductivity, so the tip stays cool.
It is more of a pain to use than a real iron.
The iron itself is just battery compartment, switch, LEDs, tip retention mechanism and little else.
It's also got the coolest case of any soldering tool I've ever seen. And you can use it as a torch, with the white LED in the tip.
Luke
Answer:
You, and the several other people who sent me similar e-mails, are quite right; the Cold Heat is indeed a resistance soldering iron.
Resistance soldering's been around for a long time, though nobody made a small mass market version before the Cold Heat, as far as I know. Simple resistance soldering outfits are popular with model train people and related hobby metalworkers, and there are big commercial models that can handle all sorts of jobs if you get the right "iron" and the right transformer to power it - AA-battery products need not apply.
Resistance soldering for electronic components can be a bad idea. Apart from the fact that it's impossible for simple resistance irons to control the temperature of the joint (hence the track-lifting problems some people experience), it's also possible to fry components if you accidentally bridge two board contacts or IC pins with the iron tip, without any solder, and thus apply the soldering voltage to the component(s). If there's little enough resistance between the points you've bridged, pop. That said, though, you apparently can use it effectively for electronic work, if you know what you're doing.
To do quite heavy duty resistance soldering without a special iron, you can use a soldering gun without a tip.
