Good lead free solder for hand soldering

[peter-h]

A while ago I evaluated a load of LF solders and found them to be basically crap, except Almit LFM48S - Japanese.

This has gone up to £100 for 0.5kg which is ridiculous. It is about 10x of leaded solder, and all prototyping is done with leaded because it works so much better, but for stuff that goes out of the door we have to use LF, just in case somebody checks.

Can anyone recommend a really well flowing LF solder?

Someone recommended Stannol from Germany but it is the same price as Almit.

[kayvee]

I presume you are talking about wire, we use Kester K100LD 0.8mm wire, which gives us great results.

For lead-free paste we use with Alpha OM-338T (S3).

[peter-h]

WOW that costs even more than Almit: £91 for 1lb (0.45kg) inc VAT.

[bdunham7]

I have a roll of AIM SN100C Glow Core which I use for the occasional lead-free task.  I would rate it as acceptable on new, shiny components and usable on repairs with some supplemental flux-pen cleaning.  I only have it in 1.0mm because I spotted it in surplus dealer (All Electronics).  I suspect if you had to buy it through normal sources at 0.8 or 0.5mm it would also be fairly expensive.   However, I don't see where you get 10X the cost of leaded--here a pound of Kester 44 Sn/Pb eutectic is about $30 or so, the K100LD is $60 or so and the 44 Sn/Pb/Ag is $90-ish. 

https://www.amazon.com/Kester-24-9574-7610-Lead-Free-Solder-020-Diameter-Low/dp/B00FGHTX5A/ref=sr_1_3?crid=2JHLZ790KUMJO&keywords=k100ld&qid=1643040226&sprefix=k100ld%2Caps%2C129&sr=8-3

[jc101]

I've moved to Solderking, UK made, 0.5Kg ~£55 in VAT (https://kaisertech.co.uk/products/soldering/solder-wire-and-flux/solder-king-solder-flux?wire_diameter=0.70mm).  They may even send you a free sample if you drop them a line.

[peter-h]

You are right - prices have gone up a lot lately. It is more like a 5x difference. I can get 500g reels for £20 e.g.
https://www.rapidonline.com/warton-metals-omega-63-37-low-residue-1-flux-solder-wire-20swg-0-914mm-500g-85-6162

Yes indeed most LF solders seem to work ok only under ideal conditions and at quite a high bit temperature.

Thanks for the Solderking tip. I have just emailed them. If they work, they are about half the price of the others.

[jc101]

I tried Warton but I didn't like the result, so far the Solderking SAC305 0.7mm has been good to work with.  Next time I need some paste I'll get a tub of theirs too.

[mazurov]

This  is what I use, likely the same @kayvee recommends but I can't figure the PN.

"Well flowing" depends on operator's skills, if you can't find one you may want to reevaluate your technique.

[peter-h]

Kester is well known but also 100 quid for 500g

Someone mentioned SAC305 is not needed for hand soldering i.e. no need for any silver. Tin and copper is enough and it is the flux that matters most.

Well, I agree re the flux because when I tested a load of SAC305 solder wire samples, most were useless and only the Almit one worked, but that is also SAC305, so it has to be the flux.

[david77]

I don't do much lead free soldering but found this to be quite good:

https://www.felder.de/products/electronic-applications/wave-soldering-selective-soldering/nige-solder-sn100ni-snag-sn100c/loetdraht-iso-core-clear-5552940520.html

[peter-h]

Just tested this



and it works well. I'd say similar to the Almit one. More tests to come.

[tooki]

Try Felder. I like it better than Stannol, and it’s appreciably cheaper.

E.g. https://www.pmtech.co.uk/solder-wire-felder-iso-corear-lead-free-sac387-250g-reel.html

[wraper]

I don't like Stannol at all. They use some crappy fluxes which either produce some dark residues and burned junk on a solder tip, and/or splatter a lot. First of all you should look on what alloy is used. SnCu alloys flow much worse  than SAC305, SAC307 and SN100C and it's clones like K100LD (unless used with active fluxes). SN100 probably produces the nicest solder joints and flows very well. SAC307 is the cheapest of what I mentioned. Regarding the quality of flux, and which is priced reasonably, I like solder produced by Alpha.

[tooki]

I don't like Stannol at all. They use some crappy fluxes which either produce some dark residues and burned junk on a solder tip, and/or splatter a lot.

Exactly my experience. The spitting is really annoying.

[nctnico]

Multicore C 502 99C 5C  works well for me. With the iron set to 330 deg. C.; from my experience lead-free solder is much more cricital where it comes to using the right temperature.

[forrestc]

We use an indium cored wire which works fairly well...  Don't know if that's available

However, what we've found works better is tacky flux such as indium tacflux 020, in a tiny syringe with a microscope.  Put just barely enough on each joint, then solder with non-cored wire.

[KE5FX]

For home use?   Order 63:37 solder from the US and wash your hands after using it.

[IanB]

I didn't see any mention in this thread, but when talking about hand soldering results, is that with or without extra flux?

It may well be that relying on the flux in the solder core alone is limiting, and that application of extra flux is important?

Even with leaded solder, I have been in the habit of using additional flux when I want really nice results. I have also found it critical to clean/polish solder pads with a suitable abrasive to remove any oxide layer before soldering.

[peter-h]

Order 63:37 solder from the US and wash your hands after using it.

You can buy it easily here in the UK - "for industrial use only"

The key to unleaded solder working well is the flux. We have tested different SAC305 hand soldering wire and some is useless and some (Almit) is almost as good as leaded but at a silly price.

The above Solder King stuff is poor, on initial tests, but we need to try different bit temperatures.

[jc101]

I've found the SolderKing CXW to be OK, the data sheet gives 350c-360c as the tip temp.  Running at 350c so far has been good for me.  By all accounts the company is happy to visit potential customers and help with testing and setups etc. to get the best from their products, which I think is free.

I don't do huge amounts though, when I do need to do hand soldering it's normally intensive for a few days depending on the project.

[peter-h]

I can confirm the above Solder King stuff is OK at 340C.

[tepalia02]

You can consider this one : https://www.sparkfun.com/products/9325

[nigelwright7557]

They used lead free solder on satellites for a while.
Then to their horror found it starts to whisker over time causing shorts.

[tooki]

They used lead free solder on satellites for a while.
Then to their horror found it starts to whisker over time causing shorts.

I don’t believe that chain of events for a second, since the aerospace industry investigated tin whiskers long, long before the move to lead free. What has been found are tin whiskers from pure tin plating on component legs.

[peter-h]

I think the whiskers story is more complicated, but I am not sure how it went.

For sure the issue got gradually sidelined by leg pitch not going below 0.55mm (the Japs went down to 0.35mm but it didn't last long) and then the big chips went to BGA which has huge spacing.

The worst whiskers were found where the substrate was stressed after tin plating e.g. extruding the old metal transistor cases from tin plated sheet. Where the plating was done after the substrate forming, the situation was a lot better.

That Sparkfun stuff is in the USA.