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No mixing of solder types

Posted: Mon Dec 12, 2016 6:20 pm
by Ronaldlees
I suppose the RaspberryPi boards are all using lead-free (containing NO lead) solder. Is that accurate? Anyway, a number of other forum posts I've seen recently are pointing to cracking problems that allegedly occur when mixing leaded and unleaded solder:
"Never mix lead-free solder with leaded solder. Solder is eutectic ... cracking on the interface may result."
I don't know if the quote is accurate.

So, of course we should not be using lead solder these days, since it's poisonous. Yet, some people may be building projects using the old leaded stuff, maybe that they've had on-hand for a long time. My reading of a few random comments on the internet gives me the impression that unintentionally open connections may be the eventual result of mixing. If solder cracks are the result of mixing, maybe this is a further encouragement to prompt people to switch to lead-free solder if they haven't already switched.

I'm no expert in this realm - so does anyone else have thoughts about this?

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:30 pm
by Jednorozec
I've been doing electronic soldering for about 65 years and I'm still here. From what I've heard, lead free solder is pretty much of a disaster. The person that you're quoting doesn't know what he's talking about since the only eutectic solder is a 63%/37% mixture which is the only kind that I use. I don't think that the small amount of lead free solder on the pads of a pc board is going to cause a problem if you use solder with lead.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:33 pm
by W. H. Heydt
You can still buy lead solder. the two most common compositions are 60/40 and 63/37, the later be the eutectic lead/tin allow. (A eutectic alloy is the one with the lowest melting pint, so you can see why that would be desirable in solder.)

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:36 pm
by Jednorozec
Eutectic solder is even better than having the lowest melting point. It doesn't have the plastic phase that will destroy a joint if you move it at the wrong time when using 60/40.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:38 pm
by Ronaldlees
Jednorozec wrote:I've been doing electronic soldering for about 65 years and I'm still here. From what I've heard, lead free solder is pretty much of a disaster ...
I've read that too, but it seems all of the new commercial boards (lead-free) I'm using seem to be doing OK. It could be that the en'masse industrial soldering systems they use can make better connections than a hand tool.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:49 pm
by davidcoton
Ronaldlees wrote: It could be that the en'masse industrial soldering systems they use can make better connections than a hand tool.
AIUI, lead free solder works well in a production environment. Hand soldering is not so easy, possibly for two reasons.
1) Lead free solder has a higher melting point, so the soldering iron must be turned up.
2) The flow characteristics of lead free solder are different from the tin-lead alloys.
I think (and I may be wrong) that the difficulties are experienced mainly by those used to tin-lead, who do not (yet) have sufficient experience of lead free.

In Britain at least the legislation requires items placed on the market to be constructed lead free. This does not prevent home construction using tin-lead solder -- although the advice about working in a well-ventilated area should be heeded. Personally I have not yet experienced any problem using older solder for the occasional repair of commercial products, but the sample is small and not conclusive.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 6:57 pm
by mahjongg
Obviously raspberry PI's are soldered with lead free solder, its illegal not to do so, and Sony knows what they are doing.
That lead free solder is a problem is often heard, often by people who only occasionally have to solder and think they have to use it, or by professionals who transitioned from leaded to lead free, and didn't know what they were getting into. The infamous XBOX "red ring of death" was allegedly caused because the company that made them used lead free solder without knowing how to handle it, and handled it as if they were using leaded solder. In the industry lead free solder is now widely accepted, so get used to it staying around, ROHS won't be revoked!.

For non professionals, and for repairs, leaded solder is still legal to use, so its still sold.

If you do solder to a board that has already lead free solder on it, use solder wick to remove the solder, before using leaded solder with it, as mixing the two results in solder mix that doesn't have the Eutectic characteristics, and there is no guarantee that the device does not vibrate while the solder is cooling. Something that doesn't happen in commercial reflow ovens.

finally soldering without good ventilation isn't a problem because of lead in the solder, but because the flux in the solder evaporates, and is bad for your health when inhaled, lead does not evaporate when soldering.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 7:28 pm
by Ronaldlees
mahjongg wrote:
... but because the flux in the solder evaporates, and is bad for your health when inhaled, lead does not evaporate when soldering.
Yes - I read somewhere that (due to vapor pressure?) lead has no significant odor. Rosin surely does have an odor! I always thought the smell of freshly sawn wood closely approximated the rosin in solder. Then I read somewhere that wood contains a lot of rosin (or was that resin?) Obviously there's no chemist here in this household, so the two things are probably not related. Seems like it tho.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 7:50 pm
by rpdom
Ronaldlees wrote:I always thought the smell of freshly sawn wood closely approximated the rosin in solder. Then I read somewhere that wood contains a lot of rosin (or was that resin?) Obviously there's no chemist here in this household, so the two things are probably not related. Seems like it tho.
Actually, they are. Natural rosin is a form of resin obtained from certain trees.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 8:04 pm
by Heater
Anyone who is soldering anything to anything will take care the surfaces are as clean possible before they start. So I cannot imagine this is a problem.

I am skeptical of this whole lead free solder idea.

Back in the day you bought a radio or TV or whatever, connected with lead based solder, and it was expected to last for 10 or 20 or more years.

Today we buy our lead free computers and tablets and phones and whatever and they go in the trash after a year or two.

I might guess that all the other toxins we throw in the land fills are far more significant than the tiny amounts of lead that may be used in the solder.

Then there is the issue of tin "whiskers" that makes lead free devices fail prematurely https://en.wikipedia.org/wiki/Whisker_(metallurgy)

Just say no to lead free solder.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 8:56 pm
by NickT
Trying to solder with lead free solder is a real horror show. It's too hard to melt and while you are trying to do so, you will probably cook the component you are wanting to attach. Just get the good old 60/40 stuff like we used to use.

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 10:47 pm
by HawaiianPi
NickT wrote:Trying to solder with lead free solder is a real horror show. It's too hard to melt and while you are trying to do so, you will probably cook the component you are wanting to attach. Just get the good old 60/40 stuff like we used to use.
I've done it many times. You just need to use a hotter iron and shorter soldering time. Actually, I do that with leaded solder as well. I've always prefered a hotter iron. It flows the solder more quickly so you spend less time on the joint, and that transfers less heat to the component.

If you are going to work with different solder types you really need an adjustable iron. The low wattage irons usually recommended for soldering electronics aren't enough for lead-free solder. The one I use is not expensive but it works well. It does get a little toasty to hold at its highest settings, but I rarely need to go that hot (one of these days I really should invest in a good adjustable soldering station).

Re: No mixing of solder types

Posted: Mon Dec 12, 2016 11:20 pm
by W. H. Heydt
Now that most of the actual soldering issues have been discussed...there is one more point to be made about working with solder the contains Lead. When you finish, wash your hands thoroughly. You've been handling Lead, and while you haven't be breathing it, some very small quantity of it is on your hands and it's best not to ingest it if that can be avoided.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 12:13 am
by stderr
W. H. Heydt wrote: about working with solder the contains Lead. When you finish, wash your hands thoroughly. You've been handling Lead, and while you haven't be breathing it, some very small quantity of it is on your hands and it's best not to ingest it if that can be avoided.
Whatever you do, don't be a grizzled old timer who has a stalk of solder sticking from his mouth to gain a free third hand.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 1:32 am
by HawaiianPi
All the drama over lead and mercury makes me laugh. When I was a kid I handled lead all the time and even played with mercury. I'm not saying they aren't toxic, but they aren't toxic enough to warrant the drama and paranoia of recent times. Someone drops an old thermometer and they evacuate the area and call in a HazMat team for cleanup. It's ridiculous!

Fishing weights, diving weights and lots of other stuff was bare lead back then, and I had a sizable quantity of mercury I handled with my bare hands. I've also done a LOT of soldering with leaded solder over the decades. If that stuff was even a fraction as toxic as modern paranoia suggests, I would have been dead a long time ago. Or maybe I would have developed mutant powers and become a superhero? Either way people seriously need to calm down and relax.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 2:37 am
by scruss
The thing about lead, though, is that while you might be very careful with it, the next guy who gets to deal with your trash might not know it's there. So it might get dumped in the creek to slowly seep through the water supply. The effects of lead poisoning in children is heartbreaking. My wife used to tutor in inner city Baltimore, and some of her adult students had been exposed to lead due to pollution from a local factory. They were basically like four year olds, often very sweet, utterly trusting of anyone. They tended to get horribly exploited as a result, and lived pretty squalid lives. There's a big industry in swindling these folks out of their damage settlements. If you need some levity after reading that, John Oliver had a good bit on Lead.

Medical studies such as Elevated Blood Lead Levels of Children in Guiyu, an Electronic Waste Recycling Town in China show that exposure to lead causes increased blood lead levels. One of the rather grimly strategic parts of RoHS is that China has realised it's going to be the lowest-cost dumping ground for e-waste, it had better get shot of lead, 'cos it's gonna come back and pollute rural China's wells if they don't. So lead-free is good. There are some old curmudgeons like Dr. Howard Johnson who rail against RoHS, but they'll be dead soon and the future doesn't belong to them.

Lead-free soldering is easy, and if you can't do it, you're using the wrong kit. Yeah, it doesn't quite have the buttery flow of leaded solder, but it doesn't have the power to make your grandchildren lead blighted lives. Someone's gonna say in this thread "But military equipment still uses Pb solder!" as if it's okay. Think of a few planes as scrap compared to the billions upon billions of scrap PCs and phones.

I had very few great uncles because I was born in a lead, chrome and cadmium processing town (Rutherglen represent!). I have no time for your excuses. Lead-free, or get lost.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 2:41 am
by Jednorozec
I also played with mercury as a child. My father had a lead melting gadget and made lead soldiers and sinkers. And how about all of the lead solder that's present in copper water pipes?

I'm quite happy with this soldering station http://www.mpja.com/Solder-Station-Proc ... /19032+TL/

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 3:01 am
by scruss
Mercury didn't do Newton much good, nor the folks in Minamata.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 3:16 am
by Douglas6
I played with mercury as a kid, and ate paint chips. It never did... What was I saying? These orange snakes are bothering the hippopotomuses again.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 10:07 am
by lumsdot
Is there such a thing as flux free solder, i get bad asthma from soldering
I have a solder fan extractor which is designed to.remove the fumes, but it only partly stops asthma.
Lead does not bother me.
A lot of tenements in glasgow still have some lead pipes

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 10:23 am
by NickT
lumsdot wrote:Is there such a thing as flux free solder, i get bad asthma from soldering
I have a solder fan extractor which is designed to.remove the fumes, but it only partly stops asthma.
Lead does not bother me.
A lot of tenements in glasgow still have some lead pipes
I'm not sure about small diameter solder wire suitable for electronics but there certainly is larger diameter wire for plumbing. That's why you need to wipe end feed couplings with flux. Given the price of solder reels now, for the tiny amount of personal domestic tasks that I do, it's cheaper just to buy solder-ring Yorkshire fittings.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 1:55 pm
by scruss
lumsdot wrote:Is there such a thing as flux free solder, i get bad asthma from soldering
Unfortunately not. Soldering without flux - especially RoHS - would be like doing the dishes without washing up liquid. Electronic solder smoke is pretty acrid, and unless you have a ducted fume management system, gets everywhere.

Plumbing solder is acidic and would destroy circuit board traces.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 7:43 pm
by davidcoton
scruss wrote:
lumsdot wrote:Plumbing solder flux is acidic and would destroy circuit board traces.
FTFY :o

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 8:35 pm
by rahlquist
mahjongg wrote: The infamous XBOX "red ring of death" was allegedly caused because the company that made them used lead free solder without knowing how to handle it, and handled it as if they were using leaded solder. In the industry lead free solder is now widely accepted, so get used to it staying around, ROHS won't be revoked!.
It was a generational thing, at that time many high temp BGA chips experienced issues. Quite a few laptops using AMD chips sold by IBM/Lenovo had an issue with joint failure. A careful reflow of just that GPU would fix the issue for a while.

Transition between materials always has its mini drama. Though I think the lead free solder is just about over at this point.

Re: No mixing of solder types

Posted: Tue Dec 13, 2016 8:59 pm
by Heater
Lead free soldering suffers from a problem known as "whiskering" which causes devices to fail prematurely as nearby connections get shorted out over time.

There is a nice article describing the problem here:
https://www.maximintegrated.com/en/app- ... vp/id/5250

As the article notes the problem has been mitigated, not solved. Which is why you won't see lead free solder used in important applications, military, space, avionics, etc.

As far as I can tell the "mitigation" in the world of consumer electronics is that nothing is expected to last more than a year anymore. So it's not a problem.

That is to say we are filling up land fills with piles of toxic stuff faster and faster every year anyway.

I find it hard to believe that the vanishingly small amounts of solder used in consumer electronics today would be such a big problem if it were leaded. Especially compared to the fact that as a kid the water pipes to our house were lead, there was lead in the roof, lead in the paint, lead everywhere. Heck I even pulled out electrical cables that were sheathed in lead.

I'm all for keeping the world we live in clean an nice but sometimes I think we are doing more harm than good with such policies.