Anyone tried to do this? I'm interested in stripping solder from a
nickel layer on small (say 1mm diameter) pins, without removing the
nickel barrier, so they can be replated with gold. Got a couple
hundred pins to do. The parts are very expensive and cannot be
Thanks for sharing any experience or ideas
On a sunny day (Mon, 22 Jul 2013 13:15:32 -0400) it happened Spehro Pefhany
I do not know if that works for you,
but I use a paper napkin folded over many times to clean solder of parts,
expecially my expensive solder iron tips.
It is amazing how good paper cleans (pins have to be hot of course).
For solder irons it is 100000 better than the 'wet sponge',
as the moisture causes he tips to rot aways,
and the sponges do not clean at all.
Paper is a mysterious thing, you can even cook water in a paper cup.
On Mon, 22 Jul 2013 13:15:32 -0400, Spehro Pefhany
I found this:
I've never tried it. That leaves what it will do to nickel:
Acetic acid: 5% acetic acid is too dilute to dissolve nickel
metal. Even the addition of hydrogen peroxide did not dissolve
the nickel to any appreciable extent after 36 hours.
It just might work...
Jeff Liebermann email@example.com
150 Felker St #D http://www.LearnByDestroying.com
Its not the dilution of the acid - that relates to the speed it works. The
strength (ability to donate or accept electrons or some such) of the acid
controls what it will eat away eg. Hydrochloric acid will eat away nickel
at any concentration
Although, HCl and H2SO4 are astonishingly slow when it comes to nickel.
The stuff is pretty much noble (hence its popularity!).
Acidity alone doesn't determine corrosivity: if a complex is formed, metal
will dissolve much faster. Copper dissolves faster in HCl + H2O2 than
H2SO4 + H2O2, because it forms a green chloride complex (there is also a
reduced form with a deep brown color, which is probably familiar to anyone
who's used this brew to etch PCBs), while sulfuric basically does nothing
special with copper.
Hydrofluoric acid isn't actually very strong, but because it forms a
complex with silicon (hexafluorosilicate), it's one of the few chemicals
which dissolves glass.
Oxidation potential is, of course, a big force. Electrolysis can beat the
pants off any chemical, for obvious reasons. (There's literally nothing
more "acidic" on Earth than the LHC -- one definition of acidity is
"proton donator", and a naked proton beam at ~light speed can't really be
stopped from "donating" to anything!) Among chemicals, this means zinc
dissolves faster than iron faster than nickel, while copper pretty much
doesn't at all (in acidic water alone). If you add an oxidizer (nitric
acid, H2O2, hypochlorite, etc.), less energy is spent generating hydrogen
and more doing the reaction. (Bubbling decreases or stops when an
oxidizer is used, unless another gas is produced -- nitric usually gives
off NO and NO2 fumes, nasty things.)
There is, of course, no chemical which is a stronger oxidizer than
fluorine, which will literally burn through anything on the periodic table
besides pure oxygen and the noble gasses (which, except for helium and
neon, are all known to form compounds with fluorine anyway, they just take
I had my share of that fun with Lithium Aluminum Hydride. I was a
novice chemical researcher, the only undergrad in the summer research
program, so a wise and kindly grad student offered to chisel off a
chunk of the concrete-like mass for me, and set it all on fire with
the second blow. We just closed the fume hood door and enjoyed the
bright red fireworks display.
I always hated it when my professors would refer to a hydrogen ion as a
"proton". Sure that's all it is, a naked proton, but there is a world
of difference in terms of how it is considered. The LHC isn't trying to
etch glass or any other chemically mediated reaction. Likewise etching
circuit boards doesn't really demand the calculations performed when
setting up a particle accelerator. Very different worlds... so why make
it sound like they are merged significantly by using the nuclear term
"proton" instead of calling it a hydrogen ion. All the other atoms are
just clumps of protons and neutrons too, but we refer to their ions
as... well, ions.
Hmm ... you are asking for *total* removal, which probably needs
a chemical attack. And the solder wets the nickel very well, to make it
For a first pass (perhaps to make the chemical pass whatever it
is more efficient) there are various mechanical and tricky ways to do it.
Are these used pins with solder and wire fragments in them?
Onews with the wire fragments removed but lots of solder, or ones which
were solder-tinned from the factory. I'll assume below that it is the
middle ground above, and what I am offering will leave you somewhat
close to the factory-tinned level.
For just a few, without a solder cup for wire ends, I would grip
them in a solder-free area with needle nose pliers or the like, dip in
rosin flux and then in a solder pot to get it up to the melting point,
and then strike the hinge part of the pliers against a wood block, thus
flicking off *most* of the solder (but not all).
With solder cups, what I would do is grip it in some kind of pin
vise, and then heat with a soldering iron and either use a vacuum solder
removal iron or use small braid soaked in rosin flux to wick up as much
solder as possible.
For quantities greater than your couple of hundred, the
mechanical method could be a vibratory feeder to an automated pin vise
Perhaps load a half dozen or more in arms fixed to a common hub, hit
with a hot air flow and while hot, spin the hub so the solder at the
outer ends is flipped off and collects as a film on the inside of the
splash shield, and then hit with a blast of cold air before dropping
them into a hopper.
And probably OSHA will consider it a hazmat zone by the time you
have all that oh so deadly lead mixed with tin scattered all over. :-)
But -- this still leaves you with needing a chemical method.
For the quantities you are talking about, it may still be less expensive
to simply buy new ones with the desired gold plating.
The cleaning methods I listed above would not be commercially
cost-effective. they are what a hobby user would do to clean terminals
stripped from old equipment for re-use.
As an electronic lab tech I second all of that. If the assembly is too
large or delicate to knock off the liquid solder, wiping it with a
wadded-up dry paper towel works well too.
If you hold the pin vertical and heat it from the bottom with an iron,
most of the solder will flow down onto the hot tip. Hit the pin with a
vacuum solder sucker as you pull the iron away. The tip of the sucker
will recoil into the pin when the plunger springs back so whatever
supports the work should be fairly substantial.
I can get the pins relatively clean pretty easily. The goal is to have
nice shiny gold plated pins again, like new, so they can be used as
Right now I'm thinking mechanical abrasion to get down to the bare
metal (which is relatively hard) then nickel plate, then gold plate.
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