Which type of lead-free solder is the best?

[newbrain]

I haven't see any lead-free that beats 60/40.

And 63/37 shreds both! 

[Psi]

Best lead free solder is mislabeled leaded solder 

[peter-h]

The proof of the pudding (an English idiom) is that 60/40 etc is still widely sold e.g.

https://www.rapidonline.com/rapid-solder-wire-60-40-22swg-0-7mm-500g-reel-85-0595

When ROHS came in, the price rocketed, presumably because everybody was stocking up with it It went from £5 to over £20 / 500g, very fast. Making money out of compliance is the world's second oldest profession.

Unleaded SMT soldering was originally a huge issue for capacitors, due to the higher soldering temperatures. Electrolytics from the biggest quality names e.g. Nichicon would "inflate" from the gases liberated. This would have triggered the scrapping of a lot of component stock. The general quality never reached the perfect wetting one got with leaded solder, but it works well enough for nobody to bother anymore.

[Bassman59]

The whole ROHS thing is pointless because lead from other sources (e.g. car batteries) is vastly bigger than lead getting into the environment from electronics.

It's not pointless.

Car batteries are pretty much always recycled. When you buy a new battery here in the colonies, the seller takes your old battery and deals with the recycling. There's a lot of lead in them and it's valuable. Sure, you have jackasses who don't trade in the batteries, but then the seller adds a "core charge" to the price of a new battery if there is no trade-in.

Consumer electronics are something else entirely. When a gizmo dies, most people just toss it into the trash, and the trash gets hauled off to a landfill. And the problem is that the lead and other heavy metals were leaching into the water supply from landfills.

Think about how many electronic things you have in your house, and then multiply that by all of the homes in your city. That's a LOTTA e-waste.

[tooki]

Except that the numbers used for calculating the lead in electronics was based on the numbers including CRT glass, which contains several kilos of lead per tube! But by the time RoHS took effect, CRTs had already gone the way of the dodo, leaving only a few grams of lead in a device, at most.

And meanwhile, literally TONS of lead continues to go into the environment in lead bullets from hunting and target practice.

So yes, RoHS’s lead restriction is entirely pointless in the context of electronics.

[Kilo Tango]

I use SM100C for lead free applications, OK it needs a hotter temp but its qualities match the filleting effect you got with 60/40, esp if you lowered the temperature a bit.....

Not all in the world of lead free is perfect, a chap here  at 4:08, removed an assembled PCB from its carrier and 4 SMD LED's "fell off". Lead free solder is only there to make a contact, 60/40 adds significant mechanical strength via the joint fillet. I have an old Marshall 10W valve amp, dear knows how old, yet it still works well, and it was built with Lead Solder. Valve amps are fairly hostile environments.

Ken

[peter-h]

Certainly you need a better process for lead free reflow soldering, to get the low defect rate which we took for granted with leaded reflow, or with PTH flow (wave) soldering.

And some components don't solder. Shelf life often becomes critical, when it wasn't with leaded. I have had varistors from Littelfuse which had problems. Even brand new. The mfg must have discovered this was a real issue and they started putting silica gel sachets into the bags...

The stuff about landfills depends very much on the landfill. Modern landfills don't have water running through them - for obvious reasons. So the story about metals leaching out of electronics is not true, via this route.

The EU regulatory apparatus has to introduce regulation all the time - it's its job They will never stop.

[Red Squirrel]

One thing I feel is needed is better electronics recycling and lead would be less an issue.  Not just lead but really the entire circuit boards themselves including components.  As far as I know there is not really any methods to recycle circuit boards right now and that is kind of a big problem as they are just filling landfills.  Lot of the electronics recycling places don't actually recycle, they just send it to china, then who knows what they do with it, probably dump in the ocean.

[pidcon]

In the past, I went through this endless cycle of switching between different lead-free formulations too. Regardless of the formulations for lead-free solder (SAC305, SAC405, Sn99Cu1, etc.) I would focus more on the lead-free offerings from reliable brands, such as Kester, Multicore, Stannol, and so on. If the work is for a hobby, then try whichever you like based on cost and ease of purchasing. If it's for business, then write to the solder manufacturer and ask for their advice.

[nukie]

SN100C by Nihon Superior with their in house flux. This formulation is available from other brands under license. This is by far the best LF solder I tried.

When trying new solder, it's best to 'wash and rinse' the tip with plenty of new solder so the previous solder does not contaminate your new solder. The solder alloy composition is very important and if it's thrown off balance the performance will not be the same.

Use a new cleaning pad after the tip is 'cleaned' because it may pickup another type of solder pieces on the used cleaning sponge.

[SiliconWizard]

Military and medical still have exemptions. In fact I think the whole "control and monitoring equipment" exemption may still be there; if not then it ended quite recently. A huge raft of small manufacturers were operating under that. And if you are using up old component stock then you have to because the pins can be tin/lead plated.

RoHS exemptions for medical equipment ended in 2016,

Active implantable medical devices are still exempted, though.

[SiliconWizard]

For manual SMD assembly, I mostly use Multicore 3C, 0.23mm. I use thicker wire (0.6mm) only for the larger parts/wiring/etc.

[Calambres]

Military and medical still have exemptions...

...and AeroSpace. Otherwise flying airliners would be a no-no for me