Lead-Free vs. 63/37 tin/lead solder

[Jeff Liebermann]

Just as a matter of interest, I always remove rosin flux residues from
boards, using a proprietory flux remover from Electrolube. IMHO, post
soldering residues left on boards make the job look scrappy and
unprofessional.

http://en.wikipedia.org/wiki/Soldering
http://www.finishing.com/Library/flux.html
http://www.worldwideflood.com/ark/pitch/pitch.htm

Ignoring acid flux, the rosin fluxes come in two flavors. Water based
and those that require some solvent to remove. Water based fluxes can
allegedly be left on the board and will not eat the copper traces. The
inspiration for this was not to reduce cleanup costs, but because of
environmental and workplace regulations which proscribed the use of
chlorinated hydrocarbon solvents for board cleaning.

The problem is that water soluble fluxes require rather hot water to
remove properly. They're mostly used wave solder machines and not
hand soldering. However, we were using them on the production in
rework stations and of course, I ended up with a few rolls of the
stuff. That's when I discovered that if you leave the flux on the
board for more than a few days, it turns rock hard and no amount of
hot water will get rid of it. The residue is water soluable, but the
big lumps left in rework are not. I experimented with some household
cleaners and found the ammonia cleaner sorta works. It's often easier
to scrape the ossified flux off the board than to wash it as it's
quite brittle.

Another fun experiment was to make my own flux. I managed to
accidentally purchase a roll of solid core 63/37. No flux inside. I
could purchase a tub of Kester rosin solder paste, but that's too easy
and no fun. Rosin is just tree sap and I live in a forest with pine
trees and lots of sticky gooey sap. I just walk outside, scrape off
some pine sap, and I have instant rosin. I melted a big lump of the
stuff to clean it and boil off the volatiles, and voila, instant
sticky rosin flux.

When testing it, I found that the soldering iron was insufficient to
set the flux on fire, but did an adquate job of converting it into
noxious fumes. Rosin works by vaporizing into a cloud of inert smog,
which protects the tin and lead from oxidation. The soldered
connections were successful, but difficult to see under the carbonized
sticky mess. Removal required trichlorethane (auto brake cleaner) and
some elbow grease. Once cleaned, the connections looked quite shiny
and bright. Obviously, I missed a step in the production process, but
in general, it worked.

 

[Arfa Daily]

http://en.wikipedia.org/wiki/Soldering
http://www.finishing.com/Library/flux.html
http://www.worldwideflood.com/ark/pitch/pitch.htm

Ignoring acid flux, the rosin fluxes come in two flavors. Water based
and those that require some solvent to remove. Water based fluxes can
allegedly be left on the board and will not eat the copper traces. The
inspiration for this was not to reduce cleanup costs, but because of
environmental and workplace regulations which proscribed the use of
chlorinated hydrocarbon solvents for board cleaning.

The problem is that water soluble fluxes require rather hot water to
remove properly. They're mostly used wave solder machines and not
hand soldering. However, we were using them on the production in
rework stations and of course, I ended up with a few rolls of the
stuff. That's when I discovered that if you leave the flux on the
board for more than a few days, it turns rock hard and no amount of
hot water will get rid of it. The residue is water soluable, but the
big lumps left in rework are not. I experimented with some household
cleaners and found the ammonia cleaner sorta works. It's often easier
to scrape the ossified flux off the board than to wash it as it's
quite brittle.

Another fun experiment was to make my own flux. I managed to
accidentally purchase a roll of solid core 63/37. No flux inside. I
could purchase a tub of Kester rosin solder paste, but that's too easy
and no fun. Rosin is just tree sap and I live in a forest with pine
trees and lots of sticky gooey sap. I just walk outside, scrape off
some pine sap, and I have instant rosin. I melted a big lump of the
stuff to clean it and boil off the volatiles, and voila, instant
sticky rosin flux.

When testing it, I found that the soldering iron was insufficient to
set the flux on fire, but did an adquate job of converting it into
noxious fumes. Rosin works by vaporizing into a cloud of inert smog,
which protects the tin and lead from oxidation. The soldered
connections were successful, but difficult to see under the carbonized
sticky mess. Removal required trichlorethane (auto brake cleaner) and
some elbow grease. Once cleaned, the connections looked quite shiny
and bright. Obviously, I missed a step in the production process, but
in general, it worked.


--
Jeff Liebermann [email protected]-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Ah ! See ... I knew there'd be someone out there that knew about the
chemistry of fluxes. Thanks for the info. Most interesting.

Arfa

 

[g. beat]

I'm a bit confused about the talk of not using acid fluxed solders in electronics. Just about all conventional solder wires formulated for electronic work, contain one or more cores of rosin based flux. As far as I am aware, this is a fundamentally acidic material when in its activated state, and in fact its being acidic is how it removes the tarnish and oxidation on the surfaces to be joined.

Afra -

In the United States, acid core (and not rosin core) was readily available for the plumbing trades (soldering copper water pipes)
When I started in 1970, it was easier for a newcomer to walk into a hardware store and purchase this formulation instead of rosin core (referred to as Radio-TV solder it that era).

While the problem has been greatly reduced, I still find a few amateurs commenting that they are using the same roll of solder they purchase many years ago -- for the copper water pipes in the house.

gb

 

[g. beat]

Good thing I found this group and asked before I bought anything, the
guy at the store counter told me acid core is mainly used for
electronic work and at the other store, the salesperson said to use
rosin core. Thats what confused me; I bought the 63/37 tin/ lead rosin
yesterday and the soldering work turned out OK. Thanks for the help!
Phillip

Go back to store and tell manager to fire him (or shut him up)

gb

 

[Jeff Liebermann]

I'm a bit confused about the talk of not using acid fluxed solders in electronics.
Just about all conventional solder wires formulated for electronic work,
contain one or more cores of rosin based flux. As far as I am aware, this
is a fundamentally acidic material when in its activated state, and in
fact its being acidic is how it removes the tarnish and oxidation on the
surfaces to be joined.

It's a question of quantity.

Both acid core and activated rosin flux contains ammonium or zinc
chloride. When heated, these produce hydrogen chloride gas (not
liquid) which disolves the copper, lead, and tin oxides and keeps the
solder joint clean. The metallic oxide is converted to zinc, metal,
and a salt. A detailed explanation can be found at:
http://yarchive.net/metal/soldering_flux.html

The difference is that the typical mildly activated rosin flux
generates hydrochloric acid vapor, not liquid. There's very little
acid in the flux and none in the residue. The bulk of the oxidation
protection is from the abietic acid in the rosin.
http://en.wikipedia.org/wiki/Abietic_acid
This effectively protects the copper from oxidation, but not the lead
or tin. That's what the hydrochloric acid smog from the activated
flux produces.

On the other hand, plumbers acid core flux contains the same ammonium
or zinc chloride, but in much larger quantities. There's plenty of
corrosive hydrochloric acid in the residue. That's the problem. Left
on the board, the acid will corrode everything. Just using such flux
around circuit boards will evaporate the acid, which will condense on
nearby components, and eventually corrode them.

 

[Arfa Daily]

It's a question of quantity.

Both acid core and activated rosin flux contains ammonium or zinc
chloride. When heated, these produce hydrogen chloride gas (not
liquid) which disolves the copper, lead, and tin oxides and keeps the
solder joint clean. The metallic oxide is converted to zinc, metal,
and a salt. A detailed explanation can be found at:
http://yarchive.net/metal/soldering_flux.html

The difference is that the typical mildly activated rosin flux
generates hydrochloric acid vapor, not liquid. There's very little
acid in the flux and none in the residue. The bulk of the oxidation
protection is from the abietic acid in the rosin.
http://en.wikipedia.org/wiki/Abietic_acid
This effectively protects the copper from oxidation, but not the lead
or tin. That's what the hydrochloric acid smog from the activated
flux produces.

On the other hand, plumbers acid core flux contains the same ammonium
or zinc chloride, but in much larger quantities. There's plenty of
corrosive hydrochloric acid in the residue. That's the problem. Left
on the board, the acid will corrode everything. Just using such flux
around circuit boards will evaporate the acid, which will condense on
nearby components, and eventually corrode them.



--
Jeff Liebermann [email protected]-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Thank you both - more good stuff on the subject !

Arfa

 

[Franc Zabkar]

Lead free solder is specially formulated to fail after not more than 1 year
because the landfill sites aren't filling up with scrap electronic equipment
fast enough!!!

I find that metho leaves a white stain on some PCBs.

- Franc Zabkar

 

[Lionel]

[cleaning flux from PCBs]

I find that metho leaves a white stain on some PCBs.

Get out the meth's again & vigorously scrub the stained areas with an
old toothbrush. That usually does the trick for me.

Isopropyl alchohol is less likely to leave residue, but it costs a lot
more.

 

[mc]

[cleaning flux from PCBs]

Get out the meth's again & vigorously scrub the stained areas with an
old toothbrush. That usually does the trick for me.

Isopropyl alchohol is less likely to leave residue, but it costs a lot
more.

Not in the USA. 70% isopropyl alcohol (mixed with water, perfectly good for
defluxing) is 40 cents for 500 mL at the corner pharmacy.

How is isopropyl alcohol made and why is it so cheap and abundant in the USA
compared to other countries?

 

[Arfa Daily]

[cleaning flux from PCBs]

I find that metho leaves a white stain on some PCBs.

Get out the meth's again & vigorously scrub the stained areas with an
old toothbrush. That usually does the trick for me.

Isopropyl alchohol is less likely to leave residue, but it costs a lot
more.

Not in the USA. 70% isopropyl alcohol (mixed with water, perfectly good
for defluxing) is 40 cents for 500 mL at the corner pharmacy.

How is isopropyl alcohol made and why is it so cheap and abundant in the
USA compared to other countries?

The IPA normally sold for electronic purposes is very pure at 99.7% or
better. Lower grade rubbing alcohol is also abundant and cheap over here.
However, I have to say that the high grade stuff is not especially
expensive, and lasts a long time. I buy it in a 1 ltr tin, and one of those
lasts about a year in my shop. I don't use it for defluxing though. For
this, I buy an aerosol product from Servisol called "De-Flux 160". It comes
in a 200ml can and lasts me for a good six months. Only a tiny spray is
required, and with a stiff toothbrush, flux and other nasty deposits
disappear like magic.

Arfa