3 Dec
2008
3 Dec
'08
2:43 p.m.
On Thu, Dec 4, 2008 at 8:19 AM, Chuck Guzis <cclist at sydex.com> wrote:
I use adapters for things such as uCs and CPLDs and
can do those
right most of the time, but occasionally, I mess up and have to start
all over again. Thank heavens for my Wood's metal desoldering trick
or I would have made garbagge out of the adapter boards.
I have a "ChipQuik" kit of some flux and a slug of something like
Wood's Metal, presumably the trick you are talking about. I have yet
to use it (it's just a free sample). The documentation seems
straightorward, though.
Does anyone on the list know where to get moderate quantities of
Wood's or Field's Metal at reasonable cost? By moderate, I'm
thinking of a small number of pounds (kgs). I don't have an immediate
use for it, but in the next year or two, I'm considering building a
RepRap or a Fab at Home and one of the things on the horizon is printing
circuits with low-temp metal on top of printed plastic substrates.
I'd like to see how much the metal is going to cost before I go down
that route.
-ethan
3 Dec
3 Dec
2:46 p.m.
On Dec 3, 2008, at 5:43 PM, Ethan Dicks wrote:
If memory serves, Wood's Metal is highly toxic. Please be careful.
-Dave
--
Dave McGuire
Port Charlotte, FL
I use adapters
for things such as uCs and CPLDs and can do those
right most of the time, but occasionally, I mess up and have to start
all over again. Thank heavens for my Wood's metal desoldering trick
or I would have made garbagge out of the adapter boards.
I have a "ChipQuik" kit of some flux and a slug of something like
Wood's Metal, presumably the trick you are talking about. I have yet
to use it (it's just a free sample). The documentation seems
straightorward, though.
Does anyone on the list know where to get moderate quantities of
Wood's or Field's Metal at reasonable cost? By moderate, I'm
thinking of a small number of pounds (kgs). I don't have an immediate
use for it, but in the next year or two, I'm considering building a
RepRap or a Fab at Home and one of the things on the horizon is printing
circuits with low-temp metal on top of printed plastic substrates.
I'd like to see how much the metal is going to cost before I go down
that route. 
3:28 p.m.
On 3 Dec 2008 at 17:46, Dave McGuire wrote:
If memory serves, Wood's Metal is highly toxic.
Please be careful.
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
5:56 p.m.
...
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...
That reminds me of another low melting point alloy with interesting
properties: Cerrosafe. I don't know if there are other suppliers, but
one is Brownells (Montezuma, Iowa, a famous supplier of gunsmithing
tools and supplies). If I remember right, it has the property of
essentially zero change in volume at the transition from solid to
molten, which means you can use it to take an accurately sized measure
of some hollow object (like a barrel).
paul
9:47 p.m.
On 3 Dec 2008 at 20:56, Paul Koning wrote:
That reminds me of another low melting point alloy
with interesting
properties: Cerrosafe. I don't know if there are other suppliers, but
one is Brownells (Montezuma, Iowa, a famous supplier of gunsmithing
tools and supplies). If I remember right, it has the property of
essentially zero change in volume at the transition from solid to
molten, which means you can use it to take an accurately sized measure
of some hollow object (like a barrel).
The way Cerro metals describes the stuff is that it shrinks as it
hardens and then expands to the original molding size as it cools
further. So you can pour it into a chamber, let it solidify a bit,
then remove it and let it cool to room temperature and have a perfect
model of the chamber.
Sounds like very handy stuff.
If cadmium scares you, there are two low-temp alloys without it--
Cerrolow 136 and Cerrolow 174.
Low temp alloys appear to be available in the UK from Bendalloy:
http://www.bendalloy.co.uk/
Cheers,
Chuck
3:15 p.m.
New subject: Wood's Metal (was Re: Open source, stand alone, ASCII terminal project)
Ethan Dicks wrote:
Does anyone on the list know where to get moderate
quantities of
Wood's or Field's Metal at reasonable cost? By moderate, I'm
thinking of a small number of pounds (kgs).
In the UK, at least, you can get Field's Metal from MUTR:
http://www.mutr.co.uk/index.php
It's under "Modern Materials", then "Special Alloys &
Ingots":
http://www.mutr.co.uk/index.php?cPath=6_473
I've purchased stuff from them a few years ago (robot motors,
I think it was), and been pleased with the service. Other than
that, I have no commercial connection to the company.
--
John Honniball
coredump at gifford.co.uk
3:52 p.m.
On Thu, Dec 4, 2008 at 12:15 PM, John Honniball <coredump at gifford.co.uk> wrote:
In the UK, at least, you can get Field's Metal
from MUTR:
http://www.mutr.co.uk/index.php
It's under "Modern Materials", then "Special Alloys &
Ingots":
http://www.mutr.co.uk/index.php?cPath=6_473
Hmm... seems that Indium has gotten quite dear lately. :-/
-ethan
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cclist＠sydex.com -
coredump＠gifford.co.uk -
ethan.dicks＠gmail.com -
mcguire＠neurotica.com -
Paul_Koning＠Dell.com -
ploopster＠gmail.com