There are several lead free solders. The really awful one is pure or=20 99% tin. That has substantial tin whisker problems, it's harder to=20 use... etc. I've used SAC305 (96.5% tin, 3% silver, 0.5% copper) for many years. =20 It's substantially easier to solder with than 99% tin, in my opinion. I=20 haven't used leaded solder in a decade or so, so I don't even remember=20 the comparison at this point. With a proper temperature-controlled=20 soldering station I just don't see the problem. Flux really matters. There are basically two types: water soluble and=20 no-clean. Water soluble is highly reactive and MUST be completely=20 removed from boards. No-clean can theoretically be left on the boards=20 permanently. Kind of ironically, it's usually pretty hard to clean=20 no-clean. I tried a special SOC305 solder with "water-soluble no clean" flux,=20 which was the absolute worst thing I've ever experienced by a factor of=20 100. The manufacturer insisted I just had the temperature wrong, but I=20 tried a whole range. I tried their solder paste as well, and spent two=20 days tinkering with the reflow oven (7 zone Heller unit, not a toaster)=20 and I never came even close to something that worked. (Everything had=20 severe graping) I couldn't get the solder to wet to anything, it was=20 maddening. So, my opinion is it's possible that people with really=20 terrible lead-free experiences just got unlucky with the solder/flux type. I use the no-clean variety... which is really hard to clean. That's my=20 main problem with it... I can't get some assemblers to properly clean a=20 no-clean board. "You can't clean a no-clean board", which is BS. I use=20 d-limonene in an ultrasonic tank, followed by an isopropyl bath... but=20 really all you need is the isopropyl. I use the ultrasonic tank to make=20 sure I'm getting everything under big, low ICs like flat packs (TQ144,=20 VQ100, etc). I know some people use isopropyl in an ultrasonic tank but=20 that's an extreme fire/explosion hazard, don't do it. The problem with water soluble is you're dependent on the assembler to=20 properly clean the boards. I had a quite reputable assembler screw up=20 cleaning part of a batch for some reason, and the highly reactive flux=20 residue literally ate away the pins on a VQ100 IC, causing 4 field=20 failures so far that we've found... at tens of thousands of dollars of=20 damage each time. So, I don't screw around with that stuff any longer. =20 Unfortunately, it's what the vast majority of assemblers use. I believe the SAC305 is much less susceptible to tin whiskers. I've had=20 only one mostly unexplained failure (out of thousands of boards) that=20 might have been a thin whisker under a 0603 capacitor... but the cause=20 was not determined for certain. The capacitor acted shorted, and after=20 touching one end with a soldering iron it was okay again. No visible=20 bridging was apparent on any visible side. The capacitor also had some=20 residue around it (maybe flux, not sure)... which I hear tends to be=20 associated with whiskers some of the time. Keep boards CLEAN is my=20 takeaway from that. The main problem with SAC305 is it makes it MUCH harder to use for=20 selective soldering machines or wave soldering. Apparently the copper=20 (?) in it tends to slowly eat away at stainless or most normal=20 containers at liquid temperatures. So, I have to use hand soldering for=20 through hole parts. I was trying to do some prototyping in China last year, and in a place=20 where you can buy almost anything you'd ever want I found it impossible=20 to find SAC305 solder without ordering it online. I found that really=20 strange. The 3% silver definitely raises the cost a bit, but totally=20 unavailable? Weird. It makes me concerned about the failure rates of=20 anything made there. Darron On 1/28/2017 2:43 AM, Electron wrote: > At 05:48 2017-01-28, peter green wrote: >> On 27/01/17 10:36, alan.b.pearce@stfc.ac.uk wrote: >>> This silver loaded one is normally used for SMD soldering to >> minimise silver leaching from the lead terminations on resistors and >> capacitors as they tend to use a silver based termination. >>> Also my understanding is that a non-lead based solder makes the best >> soldering joints, provided they are properly done. >> From a prototyping/dev/repair lab point of view there are a couple of >> issues with going lead free. >> >> 1. It melts at higher temps, that means you need more powerful irons >> and better fume extraction and you run more risk of doing thermal >> damage to components. >> 2. Lead contamination in lead-free solder leads to poor joints. That >> is bad if you sometimes have to repair stuff that was made with leaded s= older. >> >> Afaict SN/PB/AG solder is pretty much ideal for such environments, >> it's strong, has a low melting point and is compatible with pretty >> much all component surface finishes. > Thank you very much Peter. > > Cheers, > Mario > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .