Sorry, I didn't realize he was talking about tin/silver solder. The stuff I use is 62/36/2.
Zinc chloride?
Actually, it isn't an hydrochloric-acid based flux, but a chloride-salt-of-zinc one. In an of itself, this is not a problem. But the "problem" doesn't stop when the solder joint cools off.
The problem is that in the future the chloride may be somewhat hygroscopic (picking up water vapor from atmosphere), and will then become an electrolyte (ionic conductor in liquid solution). You really do not want to have little pools of electrolyte forming in hidden places inside your electronic kit. It is a really bad idea. If it bridges any two exposed conductors having different potential, electrolytic etching and/or plating can occur. Things will fail.
The whole reason why "rosin core" solder was invented was to deliver a kind of flux that would assist in deoxidizing the metals to be soldered, but where the residue would be innocuous, after the joints cool down. And innocuous for years. Under all kind of conditions from below-freezing to swelteringly hot. To humongous humidity, to bone dry. To even being wetted accidentally, and other challenges. The flux ideally wouldn't change in any negative way from all that abuse, and the abuse of being heated to well over 250C. Rosin, derived from pine trees, barely delivers this set of guarantees. It isn't perfect, as heat does degrade (polymerize) it. But the polymer byproducts retain the fundamentally attractive characters for which it was chosen.
GoatGuy
Actually, it isn't an hydrochloric-acid based flux, but a chloride-salt-of-zinc one. In an of itself, this is not a problem. But the "problem" doesn't stop when the solder joint cools off.
The problem is that in the future the chloride may be somewhat hygroscopic (picking up water vapor from atmosphere), and will then become an electrolyte (ionic conductor in liquid solution). You really do not want to have little pools of electrolyte forming in hidden places inside your electronic kit. It is a really bad idea. If it bridges any two exposed conductors having different potential, electrolytic etching and/or plating can occur. Things will fail.
The whole reason why "rosin core" solder was invented was to deliver a kind of flux that would assist in deoxidizing the metals to be soldered, but where the residue would be innocuous, after the joints cool down. And innocuous for years. Under all kind of conditions from below-freezing to swelteringly hot. To humongous humidity, to bone dry. To even being wetted accidentally, and other challenges. The flux ideally wouldn't change in any negative way from all that abuse, and the abuse of being heated to well over 250C. Rosin, derived from pine trees, barely delivers this set of guarantees. It isn't perfect, as heat does degrade (polymerize) it. But the polymer byproducts retain the fundamentally attractive characters for which it was chosen.
GoatGuy
Corrosive flux is beautiful stuff if you are willing to use the dishwasher.
It doesn't respond well to spot cleaning. Corrosive under surface mount
parts cannot be removed by dabbing at it with a Q-tip or alcohol brush.
You really have to be willing to drown it, and shoot hot water at every
capillary where flux could lurk.
Nor if any remains, can it simply be dried away in the oven. As this
type of flux will attract water from the air, and become wet and
corrosive again after the product ships.
In the back, we got three tanks full of sand and other filter media
that keep the board washing water clean. And the washing machine
is like 20 feet or longer. The boards go into cages that keep them
from being blasted off into the drain, and the cages ride through
on an open chainlink belt. Finally through an air knife that knocks
off the big drops. And then there's a whole wall of drying ovens...
Mixing fluxes in rework is a disaster. As the non-soluble residues
can shield the corrosive ones from being properly cleaned away.
Especially that plasticky stuff in the lead free no-clean...
You may not realize you are mixing fluxes until its too late, cause
its not just the obvious corrosive flux from a squeeze bottle, but
also whatever flux is hidden inside the core of the solder as it
comes from the roll. And roll holders make the ends hard to read.
It doesn't respond well to spot cleaning. Corrosive under surface mount
parts cannot be removed by dabbing at it with a Q-tip or alcohol brush.
You really have to be willing to drown it, and shoot hot water at every
capillary where flux could lurk.
Nor if any remains, can it simply be dried away in the oven. As this
type of flux will attract water from the air, and become wet and
corrosive again after the product ships.
In the back, we got three tanks full of sand and other filter media
that keep the board washing water clean. And the washing machine
is like 20 feet or longer. The boards go into cages that keep them
from being blasted off into the drain, and the cages ride through
on an open chainlink belt. Finally through an air knife that knocks
off the big drops. And then there's a whole wall of drying ovens...
Mixing fluxes in rework is a disaster. As the non-soluble residues
can shield the corrosive ones from being properly cleaned away.
Especially that plasticky stuff in the lead free no-clean...
You may not realize you are mixing fluxes until its too late, cause
its not just the obvious corrosive flux from a squeeze bottle, but
also whatever flux is hidden inside the core of the solder as it
comes from the roll. And roll holders make the ends hard to read.
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I have a syringe of solder paste which does exactly that. It is very difficult to clean also and leaves sticky crap everywhere. As a bonus the fumes are pretty noxious too.
Could you guys advise on a solder paste ? I'm looking for leaded, with or without silver, but especially an easy to clean flux, which doesn't leave lots of crap. If it is no-clean or water soluble I'll clean it anyway, so I'd rather use the one which is easiest to clean.
PS : for cleaning water soluble flux, dental water jet is very nice... it is high pressure, goes under the ICs, etc.
If I read the LENOX datasheet correctly, it is 3-6% Hydrochloric acid.
http://www.lenoxtools.com.br/msds document library/flux -sterling.pdf
http://www.lenoxtools.com.br/msds document library/flux -sterling.pdf
OK, I see. Doesn't change the basic point though - remember that HCl (unlike H₂SO₄ or H₃PO₄ or most of the organic acids) is highly volatile, and thus doesn't stick around for more than maybe a day or so. Its purpose in the flux mixture is to act as an oxide-reducer. CuO + 2 HCl → CuCl₂ + H₂O. The zinc chloride is there as a buffer, to keep the HCl around longer, and to increase the pH to something higher than 1.0 (really acidic). And at the end, it (ZnCl2) complexes with CuCl₂ to result in a stable external compound of limited toxicity.
GoatGuy
My understanding is that HCl is evolved during the heating process, and that's what reduces the oxide.
For my work, anything that is hi-rel and cryogenic requires we use halide free flux. So bromine, chlorine, flourine, and iodine are out, as all of those evolve some acid.
Honestly, for solder flux I've only seen zinc chloride.
jn
Well, even sal-ammoniac is ammonium chloride, NH4Cl, so you can't avoid halide residues as long as you even clean bits with it.
You can purchase straight rosin solution or even natural pine rosin in blocks if you wish but certainly, many custom products based on it, also contain ZnCl2. For an experiment, I salvaged about a pint of pine sap from a freshly felled Monterey pine for a few days (yechh) and have been using it for years, diluted as a liquid flux for messing with SMDs.
Here's a straightforward method with tests in a short video for committed DIYs: Magic Smoke: DIY Solder Flux From Pine Resin
You can purchase straight rosin solution or even natural pine rosin in blocks if you wish but certainly, many custom products based on it, also contain ZnCl2. For an experiment, I salvaged about a pint of pine sap from a freshly felled Monterey pine for a few days (yechh) and have been using it for years, diluted as a liquid flux for messing with SMDs.
Here's a straightforward method with tests in a short video for committed DIYs: Magic Smoke: DIY Solder Flux From Pine Resin
I also buy pine rosin by the pound (to be more precise, by the kilo).
Last purchase was around 1995 and still have some 900 grams left
I was buying R type flux from W M Dunton in Rhode Island, usually 2 or 3 cases of the 1 pound tubs at a time, 12 pounds to the case. I enforced a 6 month shelf life for the tubs, and usually ran out of stock before the shelf life expired.
The flux was advertised as simple white water gum rosin with petrolatum jelly as the carrier. It worked quite well for the tin/silver solder joints we made, typically lap joints half inch wide, and anywhere from 6 inches long to 40 feet.
For the small wires (18 gauge) where we only ran 200 or 300 amps, we used another of their fluxes, this one liquid with white water gum rosin suspended in alcohol.
jn
ps. I believe Dunton was bought out by a company called Rectorseal.
My two bits..
I imagine different solders sound different and have for many years..
Its interesting that I imagine that when a joint has been made with lead solder its not the same when re-soldered with a different solder..
(almost like its contaminated)..but that is just imagination.
Its just never the same as a fresh joint..its better but not the same.
Great this imagination thing..but there you go!
I use Cardas with lead/silver which sounds stupid..however I like the (longevity of the joint).
Some solders are great short term and then something happens..I would not go back to multicore..YMMV
NB its not as good as some types but it has a high flow which I like.
In the early seventies all I used was multicore savbit..after trying various solders I now use silver loaded solders.
If you don't use savbit it damages the iron tip very quickly!
Even Antex lead free sounds better but its melting point is a bit high..oups more imagination.
I don't like high melt point solders. (just a comment) its OK on very hot tube sockets. Its a pig to repair or modify after!
Its interesting when you think you can hear a difference..I remember using some silver low melt point solder on a circuit board and it sounded great!
I ran out of this solder never knew what it was and modified the components and used other solder and it sounded rubbish so I put the old components back using what I now had, I couldn't get it to sound the same again! (Imagination)
So I tried a few solders and I got it close but never the same..never found out what the solder type was...it was given to me at an audio show!
It ran like water..never seen anything like it since.
Regards
M. Gregg
I imagine different solders sound different and have for many years..
Its interesting that I imagine that when a joint has been made with lead solder its not the same when re-soldered with a different solder..
(almost like its contaminated)..but that is just imagination.
Its just never the same as a fresh joint..its better but not the same.
Great this imagination thing..but there you go!
I use Cardas with lead/silver which sounds stupid..however I like the (longevity of the joint).
Some solders are great short term and then something happens..I would not go back to multicore..YMMV
NB its not as good as some types but it has a high flow which I like.
In the early seventies all I used was multicore savbit..after trying various solders I now use silver loaded solders.
If you don't use savbit it damages the iron tip very quickly!
Even Antex lead free sounds better but its melting point is a bit high..oups more imagination.
I don't like high melt point solders. (just a comment) its OK on very hot tube sockets. Its a pig to repair or modify after!
Its interesting when you think you can hear a difference..I remember using some silver low melt point solder on a circuit board and it sounded great!
I ran out of this solder never knew what it was and modified the components and used other solder and it sounded rubbish so I put the old components back using what I now had, I couldn't get it to sound the same again! (Imagination)
So I tried a few solders and I got it close but never the same..never found out what the solder type was...it was given to me at an audio show!
It ran like water..never seen anything like it since.
Regards
M. Gregg
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Just for fun,
Empfasis - Intermetallics in Electronic Soldering
NB its for fun because its not about sound!
Regards
M. Gregg
Empfasis - Intermetallics in Electronic Soldering
NB its for fun because its not about sound!
Regards
M. Gregg
Excellent link, thank you.
Note the verbage concerning the solubility of metals in the second paragraph of the discussion.
I constantly see the recommendation to use solder with added copper or silver to prevent leaching of the base metal. Most common is that advice with respect to silver. While it sounds like good advice, note the red hilited sentence. When performing hand soldering, the temperature one uses is totally dependent on the VISUAL feedback during the process, not a temperature feedback. As a result, when you use an alloy which requires a higher temperature as per that advice, you fall into the exponentially increasing aspect of solubility.
The only exception I am aware of with trinary compositions is the tin/lead/silver alloy, the same one John Curl recommended. That alloy is a eutectic at 179 C, where tin/lead eutectic is 183 C.
edit:
I am unhappy however, at the second guideline.
They go into detail regarding gold and gold/tin embrittlement within the main body of the article, but do not do so for silver. So, I'm not so sure about the silver part there within the guideline.
John
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