Homebrew PCBs

On Sunday 11 February 2007 09:19, Tony Smith wrote:
> > Woods metal is an alloy of tin-lead-bismuth-cadmium. Hmm, low
> > temperature solder. I suppose that is one way of tinning your
> > boards :-)
> >
> > Les
>
> Unless you pass too many amps thru it!
>
> A quick rummage around the 'net turned up Wood's metal is 50% bismuth,
> 26.7% lead, 13.3% tin, 10% cadmium by weight.  I don't think that's RoHS
> compatible.  It melts at 70C, not 50C as I thought.  Someone once told me
> that when pointing out it was used in fire sprinkers.  Might have been a
> different alloy.
>
> However, there's Field's metal, 60C melting point and none of the nasty
> stuff, being 32.5% bismuth, 51% indium, 16.5% tin by weight.
>
> There's a bloke on eBay selling a 58% Bismuth, 42% tin alloy, melts at
> 290F. That's a bit high.
>
> Years ago I turned down the chance to buy a large chunk of Field's metal,
> dang.  It comes in handy for casting and weird machining tricks.  To
> machine something thin, funny shaped, delicate or otherwise annoying, you
> cast it into the Field's metal, machine it, then melt it off.  Since it's
> supported by the other metal, the piece you're machining doesn't get
> damaged.
>
> Tony

Tony,
Smallparts.com sells low temperature alloys of that kind.
http://www.smallparts.com/products/descriptions/lma.cfm

My group has been experimenting with printing circuit board traces on plastic, 
if people are really interested.
http://blog.reprap.org/
http://www.reprap.org

Regards,
-Sebastien Bailard
RepRap.org - self-reproducing 3D printer project.