An Engineer in Wonderland – My uncle, motorbikes, and lead-free solder

26mar08solder.jpg It was a wistful day in the home workshop yesterday when I got down to the last bit of solder on the only reel I have ever owned. I have always enjoyed making things, and this particular reel was given to me by my uncle years and years ago when I was a young teenager itching to try electronics. The last few centimetres went soldering a diode into the wiring loom of my motorbike, which is fitting because on motorbikes is how I remember my uncle. Now I have a dilemma.

Will the new reel be 40/60 tin/lead, or lead-free? The easy answer is 40/60, because: a, I can, this is not for commercial use b, I don’t have to learn the new skills necessary to get a neat joint out of the lead-free stuff. But what is actually going to happen is that I am going to go out and get myself a small reel of lead-free solder and try it out because: a, I don’t want lead poisoning to be the thing I give to the next generation. b, There doesn’t need to be a b. So this leaves me with the thorny question of which alloy, with what flux activity? And will I have to get a different temperature element for my ancient Weller soldering iron? If you have mastered good joints with lead-free hand soldering, what alloy and what temperature bit are you using. You can reply via the Comments field below. ‘Alice’

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  1. January 05, 2010 13:23

    If i were you i would not have used Lead to do the soldering,as since it really affects and thus its better to use a lead free soldering to protect the next generation.

  2. Rob
    May 02, 2008 13:58

    Pssst! I would keep a reel of 60/40 handy if I were you. Can’t beat it for reworking stubborn lead free joints. The other unfortunate aspect of lead free is the flux. Despite trying any number of bits, temperatures and solders I find that the flux gradually coats the tip and makes it less wettable. It helps a lot to keep a flux pen and a little tin of tip cleaner (Farnell) handy.

  3. 'Alice'
    April 02, 2008 13:34

    Thanks for the reply Mad Hatter.
    You are right, I could easily have mixed up the 60 and 40 in my description of my venerable reel.
    Is your solder the Multicore 99.7% tin, 0.3% copper stuff from Farnell? Or the type with 3ish% silver?
    And has anyone compared these two?
    I don’t even want to think about removing a 144 pin QFP.
    Years ago, I had to push a fair-sized fragile-looking ceramic tile with an awful lot of pins into a bunch of socket strips.
    Bearing in mind it cost the best part of a thousand quid, it needed so much force that I gave up attempt one and it was three days before I built up enough courage to finally push it home – thankfully without breaking it.
    I take the point about waste, but my simple view is that almost no one repairs anything, with many working items being thrown away in domestic waste, so there might as well be no lead in them.
    And lead-inclusive repair is fine within RoHS legislation if the broken thing originally used lead solder.

  4. John Shaw
    March 27, 2008 10:54

    Hi Alice,
    Two things sprung immediately to mind here, the first being that 40/60 tin/lead was actually plumbers solder and not quite as good as 60/40 for electrical work.
    The second is that I have been using lead free solder for some time. Mine is the common or garden (i.e. cheapest in the catalogue) variety supplied by Farnell with a halide-free no-clean flux. Given a soldering iron temperature of about 340C and a bit of practice this works well for me on most things.
    The worst aspect of lead-free solders is re-working. Removing components without cremating the circuit board is tricky and I find I have to use an iron at 380C plus solder sucker plus solder wick plus a liberal dose of bad language to get some components to part company with the copper. One particularly difficult 144 pin QFP package simply wouldn’t let go and I had to junk the board after frying most of the remaining components and lifting various tracks (None attached to the chip in question!). Yes I know I should have surgically removed the device by cutting the pins before removing them from the pads but I was being a bit stubborn that day. I still maintain that re-work was certainly easier with good old-fashioned tin/lead.
    But wait a minute, just think of the safer, cleaner world we will leave to our grandchildren. Or maybe think of the amount of waste we will generate by inability to repair some of the new things we are making because I, and possibly others with a stubborn streak, keep destroying boards.
    Is technological advance really creating a better cleaner world or will it turn out to be dirty in a different way?
    Mad Hatter.

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