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Lead-free Solder ( continued ... )

Discussion in 'Electronic Repair' started by Arfa Daily, Mar 22, 2007.

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  1. Arfa Daily

    Arfa Daily Guest

    Hi all

    Friend of mine also in the electronic service business just called me to
    tell of a conversation he had in the pub last night with one of his friends.
    Turns out this guy is a washing machine service engineer with his own
    business of many years. He told my friend that from a business point of
    view, he is delighted with lead-free solder, because in the last year or so
    it has boosted his profits significantly. This is because of the number of
    bad joints that he now sees on items such as solenoids. He is firmly
    convinced that the lead-free solder, being a harder material that doesn't
    stick well in the first place to items with a large thermal inertia, cannot
    take the vibration that a washing machine subjects it to. This seems
    altogether reasonable to me.

    Just this morning, I have repaired a NAD CD player that would play for
    anything between 5 and 45 minutes, before randomly failing. No amount of
    physical provocation would bring on the fault, nor correct it when it
    occured. It would need to be left off for about a half hour before it would
    play again. Just for sport, I tried a laser, but of course, that wasn't it.
    I then took the board out, and went over it with a headband magnifier. I
    then found two perfect cracked-right-round joints on a connector. The joints
    had that traditional lead-free straight-sided volcano like shape. Once these
    had been attended to, and the original laser put back in, everything was
    fine.

    Is it just me, or does anyone else have concerns for the wider implications
    of this nonsense technology that has replaced a mature and reliable
    technology in the dubious name of that new great ( and some would say false
    .... ) god, "Green" ? If washing machines can vibrate these joints into
    submission, I sincerely hope that the exemptions that the avionics and
    automotive electronics industries currently enjoy, never get rescinded ...

    Arfa
     
  2. I see it as another example of well-meaning people effecting change about
    that which they know not. The consequence is that a few people feel they
    have saved the world, and everyone else suffers. Mr. Common Sense has once
    again died and gone to hell.

    WT
     
  3. I have worked with it and have concluded that it is different, but not
    neccesarrily that big a deal. Some of it is much harder to work with than
    others and I suspect that just like the early days of circuit board
    automated production, we will see the manufacturers go through a learning
    curve with respect to how to use it properly. Lead definitely has its
    advantages, and I think the environmental impact is minimal for now, but
    what about hundreds of years from now? Who knows what those lead containing
    boards will be subjected to in time? It is a change that I suspect will not
    be reversed, so I see no reason to do anything but get used to it and
    happily accept any repairs that it brings me. No different from all those
    hundreds of LA7838s that did not have enough solder deposited on the joints.
    We ain't going back to manual inseertion and soldering in production lines
    either.

    Leonard
     
  4. N Cook

    N Cook Guest

    But you can get that sort of failure with Pb/Sn if the flow soldering is not
    hand redone for the large metalic heatsinky pins etc, combined with a blunt
    post soldering leg/pin-cropper straining the joint before it comes out of
    the factory.
     
  5. ian field

    ian field Guest

    Well meaning nothing! - many of these so called "green" initiatives are led
    by anarchists hoping to destroy capitalism, although they do seem to have
    shot themselves in the foot with this one as washing machines have a much
    shorter life span and the capitalists sell more washing machines.
     
  6. Arfa Daily

    Arfa Daily Guest

    Granted, you can. But this guy saw it as enough of a difference from what he
    has seen over the years with traditional lead-based solder, as to be worth
    commenting about. Where the problem comes about, is with the higher temps
    required to flow this stuff. The manufacturers dare not go up too high for
    fear of damaging both semiconductor components, and the board substrate ( to
    say nothing of their bank account from the higher energy costs associated
    with having to use the stuff - green? - Ha! ). This leads to them going
    *just* high enough to solder those components, which leaves them well short
    of enough temperature to get a really good joint at high thermal inertia
    components like connectors and power devices. Certainly, I see a lot more
    bad joints now than we had become used to with lead-based solder, and by far
    and away, the majority are on connectors and similar that would not have
    been giving the same trouble a few years back. I also see a higher number
    than would be expected, of bad joints on fine pin-pitch LSIs, often along
    one side only, which I'm guessing is the side away from the solder
    wavefront. From the time that the techniques were first developed to
    production-solder these devices, the soldering has been very reliable, but
    not any more ...

    Arfa
     
  7. N Cook

    N Cook Guest

    I'd not realised it was a hiding to nothing play off between
    temperature/wave speed/heat capicity/heat transfer rate. Heatsinky
    components/mechanically streesed ones should still be redone by hand surely.
     
  8. Interesting view of the EU bureaucrats. Anarchists. One who believes in
    the abolishment of law and order and or government. ;-)
     
  9. ian field

    ian field Guest


    Who said anything about EU beaurocrats? - They've simply passes popularist
    legislation on things they know absolutely nothing about!

    You'd have to be blind (or never watch the news) to miss the crowds of kooks
    that riot every time there's a political summit, the EU beaurocrats see
    large crowds rioting and decide that many people must all be right - eat
    shit, 2 000 000 000 000 flies can't be wrong!
     
  10. ian field

    ian field Guest

    As long as the manufacturers can (only just) get the product to out live the
    warranty they're very happy. Most electronic components generate heat so the
    temperature cycles up/down every time its used. The expansion/contraction
    breaks lead free solder pretty quickly so the production lines are busier
    than ever turning out replacement equipment.
     
  11. Arfa Daily

    Arfa Daily Guest

    Trouble with that philosophy, is that the jury is still out on whether you
    can reliably mix leaded and non-leaded solder. Some solder manufacturers say
    that you can, whilst others say that you can't. A number of independant
    metalurgical experts are of the opinion that by mixing the two solders, the
    long term integrity of the joint will be compromised. There is actually no
    requirement in the legislation to repair equipment that was originally
    manufactured with leaded solder, with anything other than leaded solder.
    Somewhere around the shop, I have an old reel of leaded high melting point
    solder that I used to use for that sort of thing, but haven't in a long
    time. It was originally for resoldering those spring-off resistors -
    remember them ?

    Just as an aside, after this morning's NAD, this afternoon I had a Sony home
    cinema - one of the DAV series - I dunno, a 300 or 500 or some such. It had
    the usual problem of thinking that it was in headphone mode, but instead of
    the common bad connector, this time, it was yet more lead-free bad joints on
    the power amp PCB. As well as the ones on the bottom of the connector that
    were causing the headphone problem, it also had cracked-around joints on
    just about all of the six channels' output filter chokes, a problem which
    you've probably all seen more than once on these, and also on the output
    relays. Now these are problems that have developed, as the boards are old
    enough that if they were original production drys, they would have showed
    long ago. I accept that drys also 'develop' with leaded solder on certain
    components that suffer high levels of thermal cycling in use, but the amount
    of drys on this one board, all on components that are either fairly large,
    or subject to mechanical vibration stress ( the relays ) rather than thermal
    issues, leads me to believe that there is a different failure mechanism at
    work here, possibly related to the lack of ductility of lead-free compared
    to leaded solder.

    As far as the suggestion of manufacturers having to hand work bunches of
    components as the boards roll off the line, I can't imagine any way that
    this could be accomplished in a practical or cost-effective way.

    Arfa
     
  12. Jamie

    Jamie Guest

    well, i do use it and i don't like the finish i get from it how ever,
    we do like using it on repairing old electronic boards that have high
    wattage R's on the board that create cracks when hot. I find in those
    cases you can increase the heat on the tip and force it to flow nicely
    which gives a good bond on those hot running components.
     
  13. Who are these experts and where are the links to the info on this? I would
    be curious what testing they have done and on what formulations. The
    vendors that have been willing to comment to me off the record say that
    there is no problem and that they are just political CYAing when they say to
    use lead free to repair lead free boards.

    Leonard
     
  14. N Cook

    N Cook Guest

    Another failure mode I've come across ove rthe years is where the component
    sourcing changes, but the board layout/drilling remains the same and the new
    comps have smaller diameter pins. The solder bridges the gap ok for a few
    years and then cracks, not even heat stressed, just room temp changes
    probably. How would the non Pb/Sn stuff fare with that situation in
    comparison.
     
  15. Arfa Daily

    Arfa Daily Guest

    Hi Leonard

    I came across several on the net saying much the same thing, when I was
    researching an article on the stuff a couple of years back, when everyone in
    the business thought that it was suddenly going to be "illegal" to use
    leaded solder after the RoHS directive came in, and that if you did, the
    solder police in their green uniforms would come rushing round to arrest you
    before beating you up and throwing you in Eurojail for 20 years. I've
    cleaned up the PC since then, but have found the following link to an
    article written by a Dr Paul Goodman, who works for a well respected
    institution who provide help and advice to industry on the technicalities of
    this directive and associated issues. I had a number of direct conversations
    with Paul to make sure that I was correctly understanding comments that he
    had made in his document on the subject, and came to the conclusion that he
    knew what he was talking about. The bit that refers to mixing solder types
    is under the heading "REWORK"

    http://documents.rs-components.com/EITC/UK/generalFiles/soldering_and_RoHS.pdf

    I'm sure with a bit of time spent, other similar comments could be found
    again, unless there has been a serious genuine ( or politically motivated )
    change of opinion by those that agreed with Paul, in the intervening couple
    of years. The document I have referred to is still live - I've just checked.
    In case that long link embedded in a news post gives any trouble, the gap
    either side of the word "and" is filled with an underscore.

    Arfa
     
  16. ian field

    ian field Guest

    Most of the far-eastern manufacturers were years ahead of the RoHS deadline
    and a huge number failed due to faulty soldering, as it was before the
    deadline I used lead/tin solder - most of my monitor customers were regulars
    so if mixing solder types had been any less reliable than the original
    lead-free, I would have soon found out!
     
  17. ian field

    ian field Guest


    ...................after less than a years use you'd be able to pull most of
    the components out without heating the solder!
     
  18. Arfa Daily

    Arfa Daily Guest

  19. N Cook

    N Cook Guest

    Perhaps we should offer the following service. What would it be called ?
    From after day one, after expiry of warranty, while fully working order, go
    inside any kit at owner's request and pre-emptively rework the usual
    suspects.
     
  20. Ron(UK)

    Ron(UK) Guest

    Sounds like a recipe for disaster if you ask me! If it aint broke, fix
    it till it is broke.

    Ron(UK)
     
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