Lead free solder - Page 1
Forum section: electronics / general

author: akis
author_rank: Frequent Contributor
timestamp: June 06, 2014, 08:19:56 am
content: After what seems to be decades using thin, fully lead+tin solder, it finally ran out and I bought a "modern" lead free solder spool. It is shiny, and slightly thicker in diameter than my old solder which must have been 0.7mm or so.The trouble with the lead free one is, it does not adhere and does not flow as good as the old one. As I was soldering last evening I thought there was something wrong with the iron, with the tip. I then used the old solder and it works perfectly. The lead free one seems to want to avoid the PCB at all costs, you can have a blob of it and it just sits there whereas the old solder would flow over the pad nicely on its own without even needing to move the tip.Could someone tell me if the lead free solders are all crap like this, and do I need to buy proper leaded solder?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 06, 2014, 08:25:44 am
content: There are better and worse LF solders - the ones with some silver in are more tolerable, but there's no reason to use them - just stick to leaded.

author: jancumps
author_rank: Unknown
timestamp: June 06, 2014, 09:00:03 am
content: i've switched when I bought an iron with temperature regulation. I'm using Sn99.3 Cu0.7, 0.6mm.My first joints were bad, but it didn't take me long to get switched over. I use flux on the pads before soldering: Edsyn FL110.

author: nanofrog
author_rank: Super Contributor
timestamp: June 06, 2014, 09:15:55 am
content: What exactly did you buy (alloy, flux type, brand), and where did you get it from?

author: con-f-use
author_rank: Unknown
timestamp: June 06, 2014, 09:47:48 am
content: Flux and higher temperature should help. Lead-free is actually not that bad, you just have to handle it differently.

author: Whales
author_rank: Super Contributor
timestamp: June 06, 2014, 10:17:24 am
content: The behaviour of solder to stick and flow onto surfaces is known as wetting. LF does not wet as well or easily as leaded: you will commonly want to to give the pads a quick brush with some steel wool before soldering. Flux also helps greatly.Quote from: con-f-use on June 06, 2014, 09:47:48 am+1. LF is definitely inferior, but it's not a deal-breaker if you're prepared to be a little more patient. You know it's not going to be the same so expect to need to use different techniques to get a comparable outcome.I've chosen to use LF because I solder in the same room as I sleep and eat.. It took getting used to -- I've found a block of violinist's rosin is extremely handy for even the smallest soldering-job -- but I now know how to approach things and don't have many issues anymore. NB further processed (actual 'soldering') rosin will probably be nicer and less messy; I'm yet to run out of my block, so I have not tried any yet

author: akis
author_rank: Frequent Contributor
timestamp: June 06, 2014, 10:37:30 am
content: I had to raise the temperature of the iron by 40 C. Even so, the solder is very reluctant to flow over pads on the PCB, what you called "wetting". For example it will flow to half the pad, where the soldering iron tip is, and will stop there, leaving the other half of the pad uncovered. It takes longer and higher temperature to make the joint, resulting in increased stress for the components. The PCB has been sprayed with SK10 flux and the copper is perfectly clean before sprayed. The lead free solder is "Sn 99.3% Cu 0.7%" 1mm.Switching to a strand of lead solder shows the differences straight away - immediate joints, solder flowing perfectly over the whole pad even with the tip in almost vertical position.

author: jeremy
author_rank: Super Contributor
timestamp: June 06, 2014, 10:40:57 am
content: I use nihon superior solder from japan, no extra flux needed. SN100C I think it is called. Works better than 60/40, probably as good as 63/37 in my opinion.

author: nctnico
author_rank: Super Contributor
timestamp: June 06, 2014, 11:39:19 am
content: When soldering lead free set the temperature at 330 deg. C and use a big tip so the soldering joint heats up fast enough. I'm using Multicore 99C (5C 502) lead free solder and most of the soldering work I do with it looks just like if I had used leaded solder. OTOH: if this is for a hobby project or prototype I'd use leaded solder (which still can be bought). Soldering lead free is definitely harder than using leaded solder. The temperature is more critical and the flux stops working earlier.

author: con-f-use
author_rank: Unknown
timestamp: June 06, 2014, 03:05:22 pm
content: For me 350 C turned out to be the optimal temperature. I don't use flux for through-hole stuff and it flows just fine on a clean board. Do you use LF tips for your iron? Do you clean your tip right before the soldering? Is your LF solder by any chance a crappy brand? Do you use a fine conical tip? Do you solder to a large (ground) plane that doesn't head up as quickly? There's a million things that could go wrong, but these few are what comes to mind.

author: M4trix
author_rank: Frequent Contributor
timestamp: June 06, 2014, 03:13:35 pm
content: Well, there is another solution for your problems, ditch the lead free crap and get back to good old leaded solder!

author: amwales
author_rank: Regular Contributor
timestamp: June 06, 2014, 03:21:26 pm
content: Go out and get some nice 63/37 (eutectic solder) solder and stop wasting your time.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 06, 2014, 03:30:49 pm
content: Quote from: Whales on June 06, 2014, 10:17:24 amWrong decision.Fumes from the more aggressive fluxes in LF are worse than any risk from metallic lead.

author: akis
author_rank: Frequent Contributor
timestamp: June 06, 2014, 03:33:47 pm
content: Empirically I found out the minimum working temperature is 340C however, it does cool off way quicker than 60/40 solder so even at 340C things are tough. I have already ordered half a kilo of normal solder.

author: AintBigAintClever
author_rank: Regular Contributor
timestamp: June 08, 2014, 12:35:10 pm
content: I bought a roll of lead-free solder from Maplin back when they were still cheap (yes, it was that long ago). Must've only used about 6 inches of it. Awful stuff, like you've picked up a roll of tinned copper wire by mistake. Back on the proper stuff now.

author: akis
author_rank: Frequent Contributor
timestamp: June 08, 2014, 12:43:45 pm
content: Yes mine is from Maplin too. Requires 340C and a lot of work. Will probably alter irrecoverably the characteristics of transistors, diodes etc