How does one use a solder pot?

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Rich Beaudry

Jan 8, 2001, 5:21:24 PM1/8/01
Hello all,

I'm a bit curious about this, as I have seen these from time to time.... How
exactly does one use a "solder pot" ? I know you have to buy special "Bar"
solder, which I assume is some thick solid bar of the proper alloy, but once
it is melted in the pot, then what?

I've heard the term "dipping" boards, but I can't visualize it. How do you
"dip" the board? Is the board parallel to the opening of the pot, or
perpendicular (in other words, do you sort of float the board on top, and
just lower it enough so only the board goes under, or do you dunk the whole
thing in, like dunking a donut in coffee)? How does one prevent solder from
getting over everything else on the board?

Sorry for the stupidity...

Rich B.

Lord Garth

Jan 8, 2001, 6:54:57 PM1/8/01
The solder pot is used to REMOVE components from SCRAP
boards. A wave solder machine uses a tank of molten solder
too but an off center roller in the solder tank produces a wave
or bulge in the solder so that just the bottom side of the circuit
board comes into contact. Rosin bars are also added and slag
is removed.

The solder pot usually has a way to raise the pot to the board
and a tray to catch the solder that will inevitably spill.

"Rich Beaudry" <> wrote in message

Joseph Legris

Jan 8, 2001, 10:20:14 PM1/8/01
Lord Garth wrote:
> The solder pot is used to REMOVE components from SCRAP
> board...

Solder pots are also used for soldering. Esico makes a nice
solder pot that will handle boards up to 4 x 4 inches. You
can buy 1 Kg bars of 63-37 high-purity alloy from Kester
Solder for under US$10 each. Melt the solder in the pot and
set the temperature to 250 degrees C. The board is dipped or
sprayed with liquid flux and then gently preheated over an
electric heater to evaporate the flux solvent. When the
board reaches a temperature of roughly 150 degrees C it is
gently dipped (not dunked) onto the surface of the molten
solder for 3-4 seconds. Kester also makes the flux. The
surface of the solder must be skimmed regularly to prevent
the accumulation of dross (scum on the surface). We used
type 951 no-clean flux and type 110 thinner, which has
rather low activity and works well on solder-plated boards.
For bare copper you'll need a more active flux. Use a fume
hood and dispose of the solder dross properly.

change the x to s to reply

Rich Grise

Jan 9, 2001, 1:52:33 AM1/9/01
To dip a board, you'd need a very wide-mouthed solder pot. Wide
enough to put the board in horizontally. You'd pre-flux the
board, drop it onto the solder, and lift it out. Solder
mask keeps it off the traces, and solder doesn't stick to
epoxy or phenolic anyway.

The only solder pots I've seen in use were about 2" diameter,
and they were used for tinning leads (you'd strip the wire,
dip it in liquid flux, and dip it in the solder) and for
soldering crimp-type terminals onto the end of wires.
(presumably it reinforces the connection.)


Jan 9, 2001, 7:33:31 AM1/9/01

I've had one of these Esico pots and never really used it.
Thanks Joseph! Now I know how! I printed out your info for future

Bob Myers

Jan 9, 2001, 11:58:49 AM1/9/01

"Joseph Legris" <> wrote in message

> Lord Garth wrote:
> >
> > The solder pot is used to REMOVE components from SCRAP
> > board...
> Solder pots are also used for soldering.

Just because no one's mentioned it yet (at least
as far as I've seen) - doesn't anyone use these things
to tin leads anymore? :-)

Bob M.

Lynn Richardson

Jan 10, 2001, 9:13:36 PM1/10/01
Hi Rich! Solder pots are simple things and can be used to solder PCBs with
through-hole/leaded components quickly and cheaply. Be sure to get one with
setable temperature. It costs more, but is worth it. A simple solder pot and a
600W lamp dimmer works well as a power controller if you want to save money, but
the temperature regulator is you.

The 'pot' at the top should be rectangular or square, large as you can afford.
Turn the heat on to max, then add the bar solder, 63/37% tin/lead is best, to
the pot. Keep adding solder until the molten metal mounds up above the lip,
brimming. You want it to be just on the verge of spilling over. Now it's time to
set the temperature, get a strip of newspaper and touch one end to the solder.
Perfect temp is when the paper just turns a light tan. (Remember Ray Bradbury's
Fahrenheit 451? Same temp!) Black or flaming is bad, so is no change. Keep at
it, until you get it right, it's really, really important to set the temp right.

By this time the solder has probably got a dull or corroded surface, this is
'dross'. Lightly scrape it off with the newspaper strip, leaving a bright shiny
surface that looks like a pool of mercury. Add more solder if the surface is
below or even with the pot lip... you want it brimming.

In a separate glass tray, pour some liquid rosin flux, Kester makes a good one.
It's a reddish color and very fluid. About a 1/4" depth is fine. Put the tray
next to the solder pot.

Ok, now it's time to solder the PCB. Make sure the leads of all the parts on the
PCB are trimmed to less than 3/16 of an inch, but more than 1/16". The copper
PCB pads should be shiny and clear of any tarnish or corrosion.

Pick the PCB by the sides up with a pair of steel tongs or very long nose
pliers. Lightly 'skim' the bottom of the PCB flat onto the surface of the flux,
don't drown it! You just want to wet the all the bottom of the board. Spilling
it over on the top won't hurt anything, just wastes flux and makes the PCB look
ugly later.

Then skim the PCB, flat, across the brimming solder surface, slow enough that it
takes three to five seconds to make a complete pass. If the board is wider than
your solder pot, make several passes in strips. Try not to overlap too much.

Once you've made a pass, hold the PCB in air, still, over a piece of tin foil
for a few more seconds. (The tin foil will catch any drips.) This stillness is
important, any parts moving about will increase the odds of bad solder joints.
After 20 or 30 seconds, carefully inspect the bottom of the PCB for solder joint
quality. If you have a lot of bad joints, check the rosin level in the tray and
the solder temp again. Then run the PCB through the same steps again.

After a few boards, you'll likely need to add more solder and flux. If you have
to add a lot of solder wait a few minutes afterwards before soldering more
boards. This allows the solder temp to come back up. Scrape the dross off too.
(Check the temp again! It's worth it!)

Ok, after you've done all your boards, time to shut down. Turn off the solder
pot, clean off any dross that's accumulated with a scrap of newspaper, then
leave the solder in the pot. It won't go anywhere once it cools. Pour the unused
flux back into it's bottle then seal tightly. It'll all be ready for your next

Done right, this works great and doesn't cost an arm and a leg. I did this for
small PCBs years ago and never had a problem, once I was told how to set the
temp right by a kindly old timer. I would have never thought to use newspaper as
a temp indicator, but it does work.

Good luck, Rich.

John Popelish

Jan 10, 2001, 10:50:38 PM1/10/01
This one is going in the archive. Thanks. :)

John Popelish

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