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tinning a pcb

Discussion in 'Electronic Repair' started by Johan Wagener, Apr 28, 2004.

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  1. I finally received my 4 pcb's which the university manufactured
    directly from the pcb layout dr. Leach has on his website.

    I noticed that they already tinned the pcb with a thin layer of solder
    or lead (silver stuff). I would like to tin it even more because I
    want the tracks to conduct maximum current when running it on lower
    loads.

    How would I go about to neatly tin the tracks? A solder iron and
    solder just doesn't do a neat job.

    I has thinking using a heat gun and solder?

    Any ideas?

    Also, Is the tracks on the leach amp pcb layout of dr. leach big
    enough to run 4-ohm loads? I noticed that they are quite narrow. I
    realise the the higher voltage makes for less current but I am still a
    bit concerned.
     
  2. Tim Wescott

    Tim Wescott Guest

    The coating is most likely real live tin -- it's fairly easy to plate on
    to copper.

    Solder doesn't conduct nearly as well as copper, so if you want to
    increase the conductivity you should choose the tracks that you feel are
    marginal and solder some bare copper wire along the track. Not only
    will the wire determine the shape of the solder for a neater job, but
    you'll get oodles less resistance than blobbing on solder.
     
  3. Active8

    Active8 Guest

    I ran into a site today that gave up on hot air solder leveling long
    ago to get ready for the lead free PCB world. The use immersion tin
    and optionally silver or nickel berrilium gold. They charge $0.50
    USD per sq in for the gold but it's $500 min because they have to
    use a whole ounce of gold and the solution only lasts 3 days.
     
  4. budgie

    budgie Guest

    sounds like CustomPCB
     
  5. Active8

    Active8 Guest

    Hey, it was! Actually there was no mention of immersion tin now that
    I look again. Probably because silver will be more compatible with
    lead free solder.
     
  6. Bob Masta

    Bob Masta Guest

    I tin all the boards I make by hand. I do this to prevent
    corrosion... and because they are so beautiful afterwards!
    It's not hard when you get the hang of it. The most important thing
    is to get some liquid resin flux and paint a thin layer over the
    copper. Then, use the side of the iron tip and apply normal
    resin-core solder from a roll. You will quickly learn how to "paint"
    the solder over the foil, and you can get a nice shiny surface with
    just a little practice.

    I tried the "electroless tin" solutions many years ago and gave
    up in disgust. The surface was dull gray and porous, and just
    about impossible to solder to.

    However, I suspect that your concerns in this case are
    unfounded. The resistance of the traces is going to be
    totally insignificant compared to circuit resistances.
    If the boards are already tinned they are protected
    from corrosion. Just go enjoy the sound!


    Bob Masta
    dqatechATdaqartaDOTcom

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
     
  7. Ian Stirling

    Ian Stirling Guest

    ..2mm thickness of solder equals the resistance of 1oz copper.
     
  8. Active8

    Active8 Guest

    I've wicked off the excess. Works good.
    Mine are always nice and relatively shiny. You have to start with
    immaculately clean copper and you can't contaminate the solution.
    Then you neutralize with ammonia and rinse in HOH.
     
  9. JeffM

    JeffM Guest

    Then you neutralize with ammonia and rinse in HOH.
    Watch out with that Hydrogen Hydroxide!
    Isn't that what they use to make Lutefisk?
     
  10. budgie

    budgie Guest

    Interestingly, I got a batch of 32 boards from them less than 2 weeks back. I'm
    still using conventional tin/lead solder, and I observed what I would call
    "poisoning" of the iron - while working on these boards, the solder seemed VERY
    reluctant to wipe off the iron. Can't think of what else to call it or how
    wlese to describe it. I'll certainly monitor this on future work on the
    immersion silver plated boards.
     
  11. budgie

    budgie Guest

    On Thu, 29 Apr 2004 13:21:17 GMT, (Bob Masta) wrote:

    (snip)
    One supplier once sent me a batch with that finish, with the same experience.
    It took inordinate amounts of time/heat to get decent solder adhesion, and that
    resulted in some board damage. He never got any more work from me.
     
  12. You can solder quite well to this finish, if you use a solder designed to
    give good wetting on an oxidised surface (such as Multicore Crystal 511).
    However I can't say that the finish has much 'advantage' over leaving the
    boards bare...

    Best Wishes
     
  13. Active8

    Active8 Guest

    Never heard of it. Ammonia is some of the worst smelling crap I've
    ever had the displeasure to work with. Peaople actually scrub floors
    with a dilute solution of the crap.
     
  14. JeffM

    JeffM Guest

    Never heard of it.
    Lutefisk is Cod marinated in--wait for it--Draino.
    It's something the Vikings came up with.
    I really like the guy who thought up using ammonia as a solvent for RTV
    instead of vinegar. Ever got a hold of that stuff?
     
  15. Active8

    Active8 Guest

    They had Draino?

    Draino has NaOH. Are you saying it has ammonia, also?
    No. Always the acetic acid stuff, IIRC.
     
  16. JeffM

    JeffM Guest

    Lutefisk
    Nope. Just Cod, lye, and lots of hydrogen hydroxide afterwards.
     
  17. Active8

    Active8 Guest

    So the Viking would have used wood ash lye like the colonials did.

    That sounds foul. I remember as a kid smelling some salmon cakes
    left in the fridge. I swear it smelled like ammonia. What a bitch. I
    was looking forward to chewing up those bones. That's always been a
    kind of novelty food for me.
     
  18. Rich Grise

    Rich Grise Guest

    D'ya know the difference between Lutefisk and snot?

    Little kids will eat snot.

    ;-}
     
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