[sdiy] Transition to Lead-Free Hand Soldering

Tom Bugs admin at bugbrand.co.uk
Thu Aug 19 23:35:32 CEST 2021

F'ing hell - just saw the price has gone up about 50% since I last 
checked! That is definitely not cheap then!

On 19/08/2021 22:33, Tom Bugs wrote:
> I've have always used Lead Free (apart from a small supply of leaded 
> for specific repairs). I guess RoHS was already in place over here & I 
> didn't want any unnecessary dealings with lead. I barely remember any 
> struggles with lead-free so am always a bit perplexed by such 
> discussions!
> I have used a Kester for where I need a water-soluble - no notes on 
> the type at present but likely the same. I have to say that the fumes 
> off this have appeared to present lung sensitivity for my assistant - 
> she always uses fume extraction for any soldering, but now wears a 
> face mask for the occasional times having to use this kester. So 
> somewhat less than ideal.
> Most of the time I/we entirely use Warton Metals SAC3 FastFlow Lead 
> Free (22SWG) because it works so well & the fumes are no issue. It is 
> not 'cheap' but I have been entirely happy using it - unfortunately it 
> is likely hard to find outside UK - not sure whether other SAC305 
> types may be similar or not
> https://www.rapidonline.com/warton-metals-omega-ii-sac3-fast-flow-flux-2-solder-wire-22swg-0-711mm-500g-85-6196 
> The only thing I would perhaps note is that tips maybe seem to wear 
> out relatively quickly & can get gunked up with blackness - I only use 
> brass wire cleaners, not sponges. I use Metcal irons so have a fixed 
> tip temperature.
> It works well for me & I'm happy not to have to continue investigating 
> for now!
> Tom
> On 19/08/2021 20:45, Mike Beauchamp wrote:
>> I've recently started transitioning into Lead-Free solder for all of 
>> my projects. Now that surface-mount assembly is affordable in small 
>> quantities, it's very easy to get boards made using lead-free 
>> finishes and solders but the hand-soldering is a more difficult 
>> transition.
>> After a conversation with Kester on the telephone (it's amazing how 
>> helpful companies can be over the phone), they suggested a few 
>> products for me to try and I've now gone through a few rolls to give 
>> some opinions.
>> For Water-Soluble flux, I am using Kester Part # 24-9574-6403
>> which is a .031" K100LD solder with the Organic 331 Flux.
>> For No-Clean solder, I am using Kester Part # 24-9574-7618
>> which is a .031" K100LD solder with 3.3% Mildly Activated Rosin 275 
>> Flux.
>> K100LD is described as "a eutectic Tin/Copper alloy with controlled 
>> metallic dopants  to control the grainstructure within  the  solder 
>> joint,  and  to  minimize  the  dissolution of  copper  into  the 
>> solder  pot.    K100LD virtually eliminates  the  occurrence  of 
>> common  defects  such  as icicling  and  bridging.    The  improved 
>> grainstructure also results in shinier solder joints than traditional 
>> lead-free alloy alternatives".
>> I'm not sure what all of that means, but it's a cheaper alternative 
>> to SAC305 at less than half the price for a roll and seems to be 
>> designed with hand-soldering thru-hole components in mind.
>> In use, both solders are "OK". I increased my tip temperature to 
>> those recommended by Kester right away, but was still noticing that 
>> the lead-free solder remains "goopier" and doesn't wet and flow into 
>> gaps nearly as fast, or sometimes at all. As I continued to increase 
>> the tip temperature, this did change and the solder started acting 
>> more like the Lead I've used for 20 years.
>> I now have my Hakko 936 set to 800 degrees and things are mostly 
>> working, but not getting great flow on TH components that are being 
>> attached to the ground plane (even with thermal reliefs on the 
>> board). Also at this temperature both solders, especially the 275 
>> Flux is spattering pretty crazy and eye protection is probably 
>> recommended. The flux residue from this solder has also completely 
>> gummed up my fume extraction tube as well, so that is also something 
>> to look out for and to be changing pre-filters often. I'm also 
>> noticing that soldering pins of cheap plastic IDC headers, it's very 
>> easy to melt the plastic with the 800F heat, so I don't dwell on them 
>> for long at all. Maybe better parts have higher heat tolerance?
>> These solders work good enough to get the job done the first time, 
>> but if you try to rework something or correct a mistake, the solders 
>> will suddenly change to sticky goo so I usually just suck the solder 
>> off completely and start with new solder.
>> Kester has a good PDF to troubleshoot lead free hand soldering 
>> issues: 
>> https://www.kester.com/Portals/0/Documents/Knowledge%20Base/Lead-free-Handsoldering.Final_.4.19.06.pdf
>> So there's definitely a compromise, but those two Kester parts are a 
>> good substitute for the leaded versions I was previously using (as 
>> suggested by Paul S. on here years ago). Next time I redesign my 
>> PCBS, I'm going to use a more aggressive thermal relief on ground 
>> plane thru-holes and I think the tip temperature should be adjusted 
>> based on the physical dimensions of the parts being soldered.
>> I'm not sure about the long-term reliability of Lead-Free solder. In 
>> my repair shop, I get a lot of music gear coming in with broken 
>> solders on PCB-mounted jacks, pots, tube sockets, etc and I can't 
>> help thinking that the lead-free solder is more brittle and prone to 
>> failure in these applications.
>> Have you converted to lead-free in your hobby as well? I'm curious to 
>> hear others' suggestions and experiences.
>> Mike
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