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Yet more on lead-free solder

Discussion in 'Electronic Repair' started by N Cook, Jun 4, 2007.

  1. N Cook

    N Cook Guest

    In the following picture
    http://home.graffiti.net/diverse:graffiti.net/solder.jpg
    without any further treatment after removing from the boards,
    one has been desoldered from a lead-free soldered board and the other from a
    leaded-solder board. Particularly looking at the top pin of each capacitor
    would anyone care to comment?
     
  2. N Cook

    N Cook Guest

    It was awkward getting the illumination angle right.
    The top one has a "silvery" coating to the pin and the bottom one a matt,
    "dusty" ie not metallic, light greyish, coating.
     
  3. Eeyore

    Eeyore Guest

    A silvery finish is associated with 60/40 type solder.

    A dull finish is classic lead free.

    Graham
     
  4. Ken G.

    Ken G. Guest

    Yes Rubycon is good qualty
     
  5. N Cook

    N Cook Guest

    Despite my belief that it was (self-repaired) punch-through of one of these
    Rubycon caps to cause an amp failure. I took each of these 470uF,50V to 55V
    on a ps with no hint of problem and didn't bother to discharge them. 3 days
    later I went to pack them away with lablels and the radial leads touched the
    tin they were temporarily in, a flash and a bang. The same with the other
    one when I tried it.
     
  6. Eeyore

    Eeyore Guest

    You asked before.

    I'm not clear what it's supposed to show. It's not as clear as it could be for
    one thing.

    Graham
     
  7. N Cook

    N Cook Guest

    I tried changing the angle of illumination and trying different colour
    backgrounds behind the pins but it was too difficult to differentiate with
    my camera and "techniques" .
    The bottom one came from a lead free soldered board. Instead of a "slivery"
    sweated film over the pins it was a dusty light grey (tin pest ? ) with just
    the odd small spot of "silvering".
    The top one was "good" overall "silvering" with just the presence of the
    normal lumps of old resin or whatever that is usually present on
    desoldering.
     
  8. N Cook

    N Cook Guest

    I think I'll have to dig out my viewing microscope/camera combo and redo the
    pic, I still have that cap laying around. I just tried finding a pic on the
    net of this dusty tin-pest ? surface but did not find one.

    For those repairing stuff made before 2006 what is the method to best remove
    the tinning from the leads from modern replacements before using ?
    The distinguishing feature is that its much harder to abraid with a nail
    file/sandpaper than tradional Pb/Sn "tinning". It is one of my personal
    quirks to abraid all components ,ICs,trannies,R,Cs etc before soldering, as
    rarely new stock replacements.
     
  9. N Cook

    N Cook Guest

    I went back to the original unscaled image , although 2 cuts, they are from
    the same pic taken at the same time with the same illumination
    http://home.graffiti.net/diverse:graffiti.net/solder2.jpg
    The lower lead free de-soldered cap lead and the upper a control from an
    older board. Proper silvery sheen, mostly, to the old one, brighter than the
    background graph paper, and totally dusty light grey for the lead-free ,
    tin-pest ? desoldered one.
     
  10. Eeyore

    Eeyore Guest

    The Commission naturally expected you to destroy all your old stock.

    Graham
     
  11. Eeyore

    Eeyore Guest

    Yes, I can see the matt finish of the lead-free one now. That's how they're
    supposed to look AIUI.

    Graham
     
  12. Chris Jones

    Chris Jones Guest

    I think if you dip the tin-plated wires in a sufficiently large quantity of
    sufficiently hot SnPb solder, that should mix pretty well with any tin
    plating that is already on the wires. The problem, as highlighted on the
    NASA pages is that you have to dip all the way up to the component body if
    you want to stop the tin whiskers, and that could damage metal-glass seals
    etc. as normally the soldering temperature is not supposed to be applied
    too close to the component body.
    Of course, because that's how we save the environment, by creating extra
    waste and then manufacturing things we didn't need to.

    That's why the WEEE was brought in after the RoHS, so that all of the old
    component stocks could all be landfilled or burned, while the component
    distributors rubbed their hands together with glee in anticipation of the
    new orders.

    Chris
     
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