Wood's Metal (was Re: Open source, stand alone, ASCII terminal project)

On 3 Dec 2008 at 17:46, Dave McGuire wrote: Yes, WM contains some cadmium. Given the very moderate temperatures at which Wood's metal is used (< 100C), I treat it as hazmat in disposal (you don't want it in the landfill), but not in use. (Think of all of the bright cad-plated hardware on your vintage stuff!). My supply comes in the form of Cerrobend, a trade name for several alloys--I use the alloy that melts at 158F (70C). I didn't purchase it for the sole purpose of desoldering, but tried it as a result of reading through the "Chip Quik" literature and knowing what they were using. I use Cerrobend in my other hobby, musical instrument construction, as a filler for bending thinwall brass tubing. Works better than pitch in that respect, but not as well as lead. On the other hand it's less likely to give you severe burns or poisoning. If you have a friend who's a radiologist, it might be worth asking if you can get some at a bargain--normally, WM is about $20-30 per pound in ingots. Radiologists use it to form shields when performing radiation therapy. I make my WM into a coarse powder (with a rasp) which allows me to stuff it into tight spaces, such as under J-leaded SMT parts. A PAR- 38 spotlamp shone at the reverse side of the PCB provides sufficient heat to do the job. No traces get lifted, nor resist disturbed. Clean the excess off the board and part (a toothbrush works fine) and reflux before resoldering. Cheers, Chuck