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Stripping Sn/Pb solder from pins

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Spehro Pefhany

Jan 1, 1970
0
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
shipped.

Thanks for sharing any experience or ideas

Best regards,
Spehro Pefhany
 
T

tm

Jan 1, 1970
0
Spehro Pefhany said:
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
shipped.

Thanks for sharing any experience or ideas

Best regards,
Spehro Pefhany

Acetic acid and hydrogen peroxide will react with the lead to form lead
acetate. That should easily wipe off. Not sure what it will do to the Ni.

tm
 
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Spehro Pefhany

Jan 1, 1970
0
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.

I want to get down to the nickel so I can brush plate gold back onto
the pins wot some cretin soldered to.
 
G

George Herold

Jan 1, 1970
0
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

shipped.



Thanks for sharing any experience or ideas



Best regards,

Spehro Pefhany

Absolutely no experience.
I guess I'd try heating and some mechancial wiping, blowing first.
Do you have to get it all off?
How much money can I spend?
Could you heat it in a vacuum to drive the last bits off?

George H.
 
D

DecadentLinuxUserNumeroUno

Jan 1, 1970
0
Replace tin/lead with gold? Are you nuts? Gold is SO less reliable
especially in light of the corrosion problems.

What is this "cannot be shipped" BS?


The problem with Gold is not corrosion. The problem with Gold is
intermetallic embrittlement.

The 'cannot be shipped' refers to no external job. must be done in
house. Justt a guess.
 
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

shipped.



Thanks for sharing any experience or ideas



Best regards,

Spehro Pefhany

From yahoo answers, looks like solubility is best way:

1) Mechanical removal is usually not practical because of static electricity considerations, and, you can't get to all sides of the device. It should be mentioned, however, the IC leads probably could withstand bending out flat (like gull-wings) so that you could get access to both sides, and use mechanical-abrasive methods to remove the lead (electronic grade baking soda abrasive blasting techniques for example, or residue-free CO2 ice blasting,mechanical sanding, etc.). Depends on the static sensitivity of your device and especially how you 'ground' the device in a custom-built enclosed fixture to eliminate static damage. Is labor-intensive, but doable to salvage an expensive device - suitable for low volumes - can be subcontracted to local shops for 'rework', but you'll have to spend time confirming that the ***very strict*** anti-static measures are implemented and adhered to on theshop floor. I don't think any post-rework electronic testing is really going to catch static damaged parts (some will only be 'wounded' and will failprematurely - short-term testing won't find this), so your only recourse is to avoid damage in the first place. Bead-blast residues are relatively small and inexpensive to capture and dispose of.

2) Chemical methods would take advantage of the solubility of lead in certain liquids at room temperature (i.e, acids). FUNDAMENTAL PROBLEM: aqueous-based solvents WILL be absorbed into the plastic. Further, acidic ions will remain trapped in the crevices by capillary action and migrate over time bydiffusion directly into through plastic to the electronic device where corrosion could occur. So the requirements for dissolution by acid are: Acids that would eventually cause device failure are excluded (this eliminates HCL due to chloride migration to the wirebonds and subsequent corrosion), acids that are difficult to rinse are excluded (sulfuric acid is notoriously difficult to rinse). Further, it would only make sense to encapsulate the epoxy IC package in a protective covering to isolate the acid from the plastic packaging in the first place (thus tooling and extra labor expense is involved). Acetic acid is a weak organic acid that *might* be usable, in that its diffusion through plastic is lower due to the larger molecule size compared to HCl. You'd have to check acetic acid against solubility of lead vs.its compatibility with gold, silicon, aluminum, copper, epoxy used in IC manufacturing. THEN you'd need to 'tin' the leads with some other metal (another expense). After rinsing, the plastic packages would need to be 'baked'to drive off the moisture (and hopefully acetic acid residues if baking temp is above boiling point of acetic acid) - this must be done in a oven specially designed for removing humidity with a rechargable dessicant (an ordinary oven won't get the dew-point low enough; you need -80°F dew point orthereabouts), and you'd need to confirm by laboratory methods the acetic acid was gone. Acetic acid is so slow acting that I don't think you'd want to wait around for it to work (time is money), but whatever the candidate acid, it would be one that you could remove the traces of completely, and wouldn't damage the device. You'll need to work with your plating shop to select the ideal acid if you take this route. To confirm the effectiveness of your rework procedure, the devices really should be tested with '85/85'-typedevice testing to confirm you haven't introduced a problem with the acidicremoval of lead, and you'd need to confirm solderability with a soldering test to ensure the moisture introduced in cleaning was indeed removed from the epoxy and didn't affect solderability. Wet chemical methods seem like the most logical or attractive approach at first glance, but really introduce a host of problems that you'd need to test and confirm to ensure were avoided by your manufacturing procedure. Hard experience shows: you could **REALLY** introduce problems and eventual failures in an otherwise reliable product if you don't carefully consider the impact of wet chemical methods. And remember, if you're not the person doing the work, the reliability is delegated to the person doing the work (you know what that means), so objective testing methods and manufacturing process procedures are fundamental to making sure the parts aren't damaged in handling/treating. Also, the Pb in the dissolved acid is now a waste disposal problem and will need to be precipiated/concentrated before sending to a hazardous waste disposal unit (also at great expense).

3) Solubility: One possible method worth investigating: how was the Pb applied in the first place? Was the Pb electro-plated on the IC leadframe? (in which case acid could not reach inside the encapsulated package to dissolveanyway), or, was it applied through a wave-solder or reflow method? Lead, like most metals, are soluble in other liquid metals (similar to mercury amalgams). Depending on your devices, it might be possible to run them again through a wave-solder bath with the objective of dissolving the Pb in a wave-solder bath that only consists of, say, tin-silver. This has the advantage of not introducing moisture & acids into the plastic which you eventuallywill need to remove later at great expense, and, the packages are 'dried' by the high temperatures, and, any oxide layer that existed on the Pb-tinned leads are now refreshed with new tin-silver tinning. Might be good idea to package in nitrogen bags for storage if you don't anticipate using them up right away to keep the tinned leads 'fresh' and oxide free. Only significant drawback: under the requirements of the law, you'd need to confirm thatwith your 'rework' method that the lead has indeed been dissolved to levels permitted by law; this however is basically a non-recurring expense with process monitoring (it also gets you off the hook if you show due diligence). Further, if anyone tests the lead frames, they would only find tin-silver on the surface of the lead frames (you'd need to dig into the fine print of the law, but traces of Pb that is buried deep in the product might be exempt under certain instances). The only way to find the Pb would be to grind up the IC into a fine powder and look for a Pb signature on a spectrograph, and I don't think that is the intent of this initial RoHS initiative.

It could be some combination of the above would work for you also.
Source(s):
http://www.rohs.gov.uk/content.aspx?id=5
http://www.infoplease.com/ce6/sci/A08291…

http://answers.yahoo.com/question/index?qid=20060628124719AAiDWml
 
S

Spehro Pefhany

Jan 1, 1970
0
Absolutely no experience.
I guess I'd try heating and some mechancial wiping, blowing first.
Do you have to get it all off?
How much money can I spend?

Not much of a constraint. Actually, I lied, it can be shipped.
Miscommunication. Apparently "welded" means something different to
other people.
Could you heat it in a vacuum to drive the last bits off?

George H.

Probably not safe, cracking of the insulation ($$$$$$$$) and lead
fumes.


Best regards,
Spehro Pefhany
 
S

Spehro Pefhany

Jan 1, 1970
0
Not BS. I was originally told it was welded into a big chunk of a
multi-million dollar "thing", but it turns out not. Still better not
shipped.
The problem with Gold is not corrosion. The problem with Gold is
intermetallic embrittlement.

The 'cannot be shipped' refers to no external job. must be done in
house. Justt a guess.

Turns out it doesn't have to be done in-situ, but still I'd hand carry
the d*mn things.


Best regards,
Spehro Pefhany
 
M

Martin Riddle

Jan 1, 1970
0
Not BS. I was originally told it was welded into a big chunk of a
multi-million dollar "thing", but it turns out not. Still better not
shipped.


Turns out it doesn't have to be done in-situ, but still I'd hand carry
the d*mn things.


Best regards,
Spehro Pefhany

Would it be an optionto machine off the sn/pb and Nickel, then
replate?

Cheer
 
R

Robert Baer

Jan 1, 1970
0
Spehro said:
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
shipped.

Thanks for sharing any experience or ideas

Best regards,
Spehro Pefhany
Replace tin/lead with gold? Are you nuts? Gold is SO less reliable
especially in light of the corrosion problems.

What is this "cannot be shipped" BS?
 
D

DoN. Nichols

Jan 1, 1970
0
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
shipped.

Hmm ... you are asking for *total* removal, which probably needs
a chemical attack. And the solder wets the nickel very well, to make it
more complex.

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.

Good Luck,
DoN.
 
T

tm

Jan 1, 1970
0
DoN. Nichols said:
Hmm ... you are asking for *total* removal, which probably needs
a chemical attack. And the solder wets the nickel very well, to make it
more complex.

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.

Good Luck,
DoN.

Hey, how about tumbling in a material softer than Ni but harder than Pb?

Find someone who reloads ammo and try it with corn cob media.

tm
 
L

Lasse Langwadt Christensen

Jan 1, 1970
0
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

shipped.

dependsin why you need to but, how about putting the parts in machined
gold plated sockets and solder from top inside only?

-Lasse
 
T

Tim Williams

Jan 1, 1970
0
David Eather said:
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
some persuading).

Tim
 
S

Syd Rumpo

Jan 1, 1970
0
OK, just watch out, lead acetate is VERY easily absorbed through the
skin, considered HIGHLY toxic.

Jon
'Sugar of Lead' (lead acetate) gives a sweetness to wine which had
oxidised. Just hang some lead in your wine and banish that vinegary taste!

Cheers
 
S

Syd Rumpo

Jan 1, 1970
0
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
shipped.

Thanks for sharing any experience or ideas

Best regards,
Spehro Pefhany


I would try polishing the solder off, first having removed excess with
solder wick and flux. Maybe make a tool for a Dremel comprising that
thick polishing felt but with <1mm axial hole to fit over the pins, and
use with a little metal polish paste.

And keep a swear box nearby, you could make a fortune.

Cheers
 
S

Syd Rumpo

Jan 1, 1970
0
How do you propose he prevent ESD damage?

Connect the pin to ground, I suppose.

If you can't, make sure your polish is a bit conductive, maybe add some
water if necessary and ground the Dremel if it's floating.

I actually grew up near a polish club. It was years before I realised
that it was in fact a Polish club.

Cheers
 
U

Uwe Hercksen

Jan 1, 1970
0
Lloyd said:
'Reverse plating' is another method. Depending upon the electrolyte and
the other electrode, it can be exquisitely selective.

Hello,

I think the applied voltage is more important than the other electrode
material.

Bye
 

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