60/40 vs 63/37? If I can get my hands on the latter, why not?

[Djentronio]

What makes 60/40 the standard when 63/37 appears to be far better due to its lower melting point?

[GGBB]

The main difference between the two is that 63/37 is eutectic. Melting point difference isn't a big factor in practice. Eutectic is generally beneficial, especially for the type of work we do.

[R.G.]

+1 on what he said.

The screaming advantage of eutectic alloys is that they go >instantly< from molten to solid, with no intermediate soft pasty stage. So there's no chance to move the parts during the pasty stage and cause a cracked, weak joint.

[Djentronio]

Any downsides? Hell, it sounds like Im buying 63% from now on.

[stallik]

Fascinating.

So, the soft pasty stage occurs because of the different melting points of each component in a non eutectic mix. You also end up with a joint made of those components in intimate proximity but not an even mix.
Given the free availability of non eutectic mixes, my simple mind is wondering what advantages those mixes give

[EBK]

Given the free availability of non eutectic mixes, my simple mind is wondering what advantages those mixes give

Advantage: they make the rest of us using the magical 63/37 stuff look good.   

[Djentronio]

I checked the melting points and its basically 5 degree C or 9 degree F difference.

Another benefit is that since it has less lead, its less contaminating. 3% less is better than 0% less imo.

Yet its much rarer to find on solder lists in online stores.

[R.G.]

Fascinating.

So, the soft pasty stage occurs because of the different melting points of each component in a non eutectic mix. You also end up with a joint made of those components in intimate proximity but not an even mix.

Yes. The pasty stage is from little domains of the higher-melting point part solidifying first into tiny grains of solid mixed into a eutectic surrounding. In this state, any mechanical movement stirs the solidus powder around in the eutectic liquid, and the wetted powder holds to the liquid, letting chunks of this separate much like wet clay breaks on a roughly divided surface. And for the same reasons.

Given the free availability of non eutectic mixes, my simple mind is wondering what advantages those mixes give

My best guess is one fewer decimal places. It can be argued that 60-40 is really close to 63-37, and you don't have to analyze it to such precision.

Another benefit is that since it has less lead, its less contaminating. 3% less is better than 0% less imo.

I sometimes despair of this kind of "thinking". Sorry - this is not a criticism of you personally, but how you've been fed a line of dogma. Somehow, the western world has stopped trying to teach people how to think, and started substituting political correctness for thought.

Yes, the correct amount of lead entering your body is dead nuts zero. No, that is impossible on this planet. Lead is a constituent of the entire planet, and yes, humans have mined and concentrated it, so it's worse. But that ship has sailed. Lead has been used and abused by humans for at least two thousand years. It didn't vanish when we decided it was a bad thing.

The change to unleaded gasoline caused a bigger reduction in lead in the environment than outlawing all lead solders. However, outlawing all leaded solders - which is nearly what happened - for hobbyists would change world lead usage by an undetectably small amount. It does satisfy the craving for controlling the thoughts of others, though, since if it's bad, no one should have it. and some "entitled" group will decide what people can have and not have. What's left out of this entirely is putting the onus on people to think and act responsibly.

You hit a nerve - can you tell?   

[GGBB]

Given the free availability of non eutectic mixes, my simple mind is wondering what advantages those mixes give

60/40 is - or at least was - cheaper than 63/37. Tin is expensive compared to lead. We hobbyists won't care if the price is close, especially because those of use with meager soldering skills should have less poor joints with eutectic. Manufacturers very well may care - especially since eutectic might not be a significant benefit in automated production (guessing).

A related question - is eutectic an advantage or disadvantage for manual desoldering work? I want to think disadvantage but I don't know why.

[Djentronio]

Isn't lead based solder banned in the UK though? I think the commercial requirement is products be lead free, which means no lead in solder, ICs.....

I found this on the subject of the ban and reliability of lead-free. Maybe its gotten better lately though. I didn't mean to spin off like this, 63/37 seems like a winning scenario.

http://www.metafilter.com/138942/Lead-Free-Solder-friend-or-foe

[EBK]

Best analogy I can come up with for what it's like working with lead-free solder is:

It's like working with solder mixed with sand bags that help it to resist flowing as if it is protecting PCB Town from devastating flooding, and it covers even the best joint with a questionable cloudiness that makes judging a finished product like looking through cataracts or the fog of war.

[R.G.]

A related question - is eutectic an advantage or disadvantage for manual desoldering work? I want to think disadvantage but I don't know why.

It is a screaming advantage. You don't have to guess when the joint is cool enough, and there is a clear visual change to solid when it solidifies. The pasty stage of non-eutectic solder is hard to pick out from the solid (for me, anyway).

[PRR]

Old-time solder suppliers were unsophisticated. Half Tin half Lead-- 50:50 for plumbers solder. 6 tons Tin, 4 tons Lead- 60:40, "close enough to eutectic" for low-temp work (like radio/audio electronics).

Of course now the solder makers have digital scales to control the mix (basically to make sure you never get more costly Tin than you paid for). So sure, they will dial-up a batch of 63:37 if you pay for the extra Tin.

I've done thousands of joints in 60:40 (since before 63:37 was readily available) and have a lifetime supply of 60:40 left, so I'm sticking with it. I don't know any reason to not use 63:37; it is indeed "easier".

[stallik]

10 years ago I bought a big reel of 60/40 lead solder which is now running out. I tried and didn't care for lead free so I will now order 2 reels of 63/37 lead in my preferred .8mm guage
The first reel should last me my lifetime, the second is for insurance in case I end up out staying my welcome.

[bluebunny]

Isn't lead based solder banned in the UK though?

No it's not: you can buy it anywhere.  It's not going to "contaminate" anything, unless you throw your finished PCBs or pedals into landfill.  And then it's going to be a negligible amount.  Buy 63/37 by all means, but it's not going to rid the planet of lead (pollution) by any amount that anyone can measure.

[anotherjim]

What I see is that lead-free solder is really just intended to make consumer stuff "safer" to throw into landfills. You decide if that is actually a "green" policy

[EBK]

Lead has to be removed from the environment in order to make leaded solder, right?   

For those of you who love data about the environmental impact of lead-free solder (and who doesn't, right?), here's a 472-page report from an EPA study in 2005:
https://www.epa.gov/sites/production/files/2013-12/documents/lead_free_solder_lca_full.pdf

[PRR]

The vast majority of Lead in your life is your car batteries. These are around 98% recycled today. Yes, I can throw one in the woods, but most people won't, and the last one they credited me $10 for turning in my old battery, so lead batteries generally go home again. They schlepp them back to Pennsylvania, melt-out both the Lead and the plastic, build new batts with "your logo here" (the one factory makes 9/10ths of batts sold in the US), and ship them to stores to sell back to you.

Overall, all products, about half the world's Lead comes from reclaiming scrap Lead; this proportion is increasing. It is cheaper to smelt used Lead than to dig and separate it from dirty ores. Even established Lead mines will buy scrap Lead when it is cheaper than digging, crushing, roasting ore.

However electronic scrap is often bundled and shipped to Africa where children pick it apart with their teeth and open fires to get "mostly copper", "mostly lead", "mostly plastic", which then go back to scrap markets. Not a healthy trade. (This is like a city-full of dead TVs, not your DIY scrap.)

[EBK]

Paul, the only thing I'll add is that the EPA report I linked to says 68% of the Pb in our magical eutectic solder is new, non-reclaimed Pb.

But, that report was paid for by somebody, so.....

[amptramp]

A lot of electronic equipment has gone into water for one reason or another (the boat it was on sinking, for example) and the loss of lead is miniscule.  Pewter (which is basically a harder form of solder) was a bad thing to drink from if any vinegar got on it (creating lead acetate which is soluble and deadly).  Pipes carrying water were made of lead.  Terne plate which is lead-coated steel was used for roofing a century ago.  And of course, leaded paint was a main problem.  Firing ranges expose people to a lot of lead.  But solder?  There is no way enough of it was used and got into contact with humans to make any difference.