Lead-free solder - love the EU, not!

[Eric The Viking]

You may have heard of a case of lead poisoning from exposure to electrical solder, but I haven't.

Last week I mended the fourth item (recently) that has died because of lead-free solder joint failure. I've one more in the queue, I think, too. The stuff not only fails with vibration and flexing, it doesn't wet the surfaces well, and some variants grow conductive whiskers (crystals) that cause short circuits. It needs higher soldering temperatures (+20deg C depending on composition), so my older soldering irons are inadequate, and you'd be wise to use a decent flux too, and not trust anything new called 'multicore'.

It's banned in aerospace applications, and, I think there's an exemption for the motor industry too.

I'm wondering when someone will have the guts to admit the stupidity and cost of all this and allow good old 60:40 again.

Frustrated,

E.

 

[Sheffield Tony]

Indeed. All those soldering irons, solder baths and ovens running 20C higher. All those extra failed parts to landfill. All that extra tin mined by some of the most destructive methods. Great help to the environment, saving that bit of lead, expecially when I can still cover my roof with it.

Nobody will ever admit it was a bad idea, I thought the only exceptions were for military applications ?

If you need to comply, my advice for hand soldering would be to avoid the standard 99C Sn/Cu solder with X39 no clean / low fume / little effect flux, but instead select a Sn/Ag/Cu solder, which has a lower melting point and is a eutectic alloy, so less likely to give a bad joint through move whilst cooling. That combined with a Crystal 505 or 511 flux seems to work best for hand soldering for me, at least.

 

[Eric The Viking]

My advice for hand soldering would be to avoid the standard 99C Sn/Cu solder with X39 no clean / low fume / little effect flux, but instead select a Sn/Ag/Cu solder, which has a lower melting point and is a eutectic alloy, so less likely to give a bad joint through move whilst cooling. That combined with a Crystal 505 or 511 flux seems to work best for hand soldering for me, at least.

I quite agree, but there's a slight Catch #22: the better solder for soldering (the silver alloy) is also the one most prone to dendrite formation (conductive crystals). I've used LaCo plumbing flux wit hreasonable results, but I'll try the ones you suggest.

Generally I find the easiest course is to vacuum-remove as much of the original as possible, re-tin it and resolder with traditional 60:40. You have to use more flux, as the lead-free and leaded seem otherwise incompatible.

Also don't use lead-free on gold-flashed contacts. Apparently it scavenges the gold, leaving a poor joint, and the localized increase in gold concentration in the amalgam also promotes dendrites (lead supposedly inhibits it). Sigh.

I'm sure you're right about the military exemption too - I'd forgotten that. Given the fly-by-wire nature of modern civil aviation, I'd be really nervous if it is lead-free. It's definitely banned in satellites (because zero-gravity promotes the growth of, you guessed it, dendrites!). They had some failures before someone realised the mistake!

Cheers,

E.

 

[AndyT]

Come now Eric, how are we going to get the economy going if you keep mending old stuff?
I've heard a nasty rumour that some people even make things for themselves - how is that supposed to make anyone wealthy?


Seriously though, you're right about solder.
I still use the soldering iron I had for my 11th birthday and although it always used to be fine, I have to put it on half an hour early to get anywhere with the solder Maplin's sell now.

 

[mseries]

Come now Eric, how are we going to get the economy going if you keep mending old stuff?
I've heard a nasty rumour that some people even make things for themselves - how is that supposed to make anyone wealthy?


Seriously though, you're right about solder.
I still use the soldering iron I had for my 11th birthday and although it always used to be fine, I have to put it on half an hour early to get anywhere with the solder Maplin's sell now.

My Dad is a retired electrician and he gave me a soldering iron and roll of solder, I think it is original lead based. I have had it for over 20 years anyway.

 

[t8hants]

I always buy old solder sticks and rolls if I see them at boot fairs, 'ugger the EU!

The most detrimental thing to any environment is a green!

 

[Sheffield Tony]

Good old 60:40 solder is still widely available (CPC/Farnell, eg). And you can use it. The ROSH legislation merely prevents you from introducing a new commercial product using it. I suspect from the ease of availability that the regs are widely ignored. Unfortunately in my day job I have to take some notice, so do as I described above. Incidentally, I routinely hand-solder QFP packages with 0.5mm lead pitch, and I've yet to see one fail either because of a dry joint, or dendrites.

PS: AndyT, you've had better luck than me. I got my first soldering iron for Christmas when I was 12, but it broke long ago ...

 

[monkeybiter]

I routinely hand-solder QFP packages with 0.5mm lead pitch

Big-Head! :mrgreen:

 

[tekno.mage]

I won't use lead free solder at all (possible exception being the one with lots of silver in which is quite good for repairs to silver-plated costume jewellry!) I still have and use a 30 year old Weller soldering iron (the one with the black transformer block) and some stocks of leaded multicore solder. You have to use a number 9 high temperature tip in my Weller iron if you want to melt this horrid modern lead-free stuff - and that burns out the magnetic thermostat thingie inside the soldering iron more quickly - aside from making a much poorer solder joint that grows tin whiskers later on. I really hope the EU beaurocrats that decided on this lead-free solder directive suffer a horrible accident caused by the failure of a lead free soldered joint!

When you think about the tiny amount of lead that was in soldered joints as compared with the vast amount lurking inside an average car battery, I think perhaps the beaurocrats who decided this one have shares in the companies that make lead free solder - or maybe it was just sheer incompetance?

 

[Sheffield Tony]

My point was that you can do even quite tricky hand soldering fairtly reliably with lead free - I have to - though you might need to develop suitable techniques. A hot iron - a Weller #7 (370C) is quite enough, the number 9's are far too hot. Not too small a bit, the really skinny ones cool off too much. A good flux. For the fine SMT stuff, a liquid flux painted on is the way to go.

As for the failures - lead free may increase them. But I'm sure that in consumer electronics, the impact of penny pinching on soldering temperatures, flux, solder, inspection and other quality of manufacture issues are also to blame.