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Thread: Tin whisker Disease

  1. #1

    Default Tin whisker Disease

    Although this video monitor is not exactly vintage, I think we are all going to see a lot more of this sort of trouble cropping up in our vintage or soon to be vintage computer equipment, especially with the surface mount IC's with a very fine lead pitch and lead free solder. So at least it pays to be aware of it. This is what I just experienced:

    The 2004 vintage LG LCD video monitor I use with my Athlon 64 computer (running XP) developed an odd fault (which was the real clue). The menu for the screen setting spontaneously appeared and scrolled through randomly like somebody was randomly pushing the menu button. At the same time, half of the picture, split down the vertical mid-line, changed contrast, which cannot normally happen with any button setting. I disconnected the button array, no help.

    The menu control button was still working and I could manually cancel the random selections. The second clue was that these two faults, in two completely different parts of the system were malfunctioning at the same time and randomly. The fault became more persistent over a few days.

    At first I didn't have a clue what could cause it, and no schematic either. So I inspected the pcb under high magnification and noticed the screen printing that said "Pb Free".

    It was then I realized the likely mechanism for the fault; Tin Whiskers. Under high magnification I found them growing between the finely spaced pins of the main processor IC labelled "Flatron Engine". I used some thin shim brass to clear the spaces between the pins and washed the pcb. It is fine now.

    The thing to remember about tin whiskers, they create an entirely new circuit configuration, so the faults when they occur seem weird or impossible and are initially intermittent. Tin whiskers are a real problem as lead free solder circuit boards age. NASA has done some papers on the topic. I first noticed tin whiskers in the late 1980's when they took out the AF11x series transistors in my Eddystone EC-10 communications radios.

    One reason these whiskers are diabolical is that most fault finding techniques involve a knowledge of the circuit design and function and the fault therefore points you to the sub-circuit in question. But with whiskers it is a whole new ball game because they create an entirely new circuit configuration.

    I also had a tin whisker take out one of my 2465B scopes and it took me a week in that case to figure it out and find it. I'm better now I know to pay attention to the oddball effects & faults that whiskers generate. I'd much rather have lead in the solder and no whiskers.

  2. #2

    Default

    Leadless solder makes for a disposable world which is great for people selling things. My son's iphone that was bought 6 weeks ago literally heated up and died Sunday. I took it into the Apple store and I will give them that they take care of their customer, the guy replaced it with one on the stop and worked on the process of restoring everything. He even transferred the screen protector with finesse. He said that despite the phone being new, it had been sitting around for awhile (which is why I got it at a discount), but what is while? 3 years? 5 years? How long does it take before "modern" electronics fail? It seems a magnitude different than leaded solder. Doesn't lead exist in nature anyway?

  3. #3
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    Sure. Cities are even named after it. Mineral Point, Galena, etc...

    Lead is amazing stuff with a myriad of uses. But like everything else these days, because someone can be irresponsible with it, it is utterly demonised.

  4. #4

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    Lead-free solder is utter garbage and belongs in the trashcan.

    Laws that restrict the use of lead also belong in the trashcan, alongside the politicians who author them.

  5. #5
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    Default

    Obviously you don't want leaded stuff in a landfill, but people are so brainwashed by the big corps they literally think that even being in the same room with a molecule of lead will cause their children's brains to fry (yet, every Sunday they have their children sent off to have the science beaten out of them). Similar story with that evil "ray-dee-a-tion" and high voltages produced by CRT's.

    Of course, since it causes electronics to not last as long, the big corps love it as it keeps people coming back for more sooner. What a world.

  6. #6
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    Default

    Very interesting, never hear about this phenomena before.
    I have a monitor that do this same thing the menu appears by itself and is like the buttons randomly are pressed.
    Replaced voltage regulators and checked all the board without avail.
    No i will check the main controller ic for this things maybe they are the culprit.

  7. #7
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    Bridges and battleships were painted with lead-based paint (mostly lead oxide); roofs and windows are still flashed with the stuff--and fishing sinkers are made with it.

    There are two aspects to lead--there's the metallic stuff, which is pretty innocuous and then there are organic lead compounds, which are nasty. One of the nastiest is tetraethyllead, which easily crosses the blood-brain barrier and was used as an anti-knock additive for gasoline for decades; hence, it's buried all along our roads and highways. If you want to read about a scandal, check into the history of the Ethyl corporation, whose founders were well aware of the toxicity of the stuff they were selling.

    Here's a quote from WikiP:

    Tetraethyllead has been recognized as a contributor to soil, air and water lead pollution, and is toxic to humans. While leaded gasoline made engines more efficient, lead pollution has increased by over 625 times previous levels in the past century due partly to pollution by leaded fuel. Ethyl Corporation historically denied that tetraethyllead poses significant public health risks in excess of those associated with gasoline itself.
    So it isn't lead solder that's been the plague of the 20th century.

  8. #8

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    Quote Originally Posted by Chuck(G) View Post
    So it isn't lead solder that's been the plague of the 20th century.
    How is it that lead solder got this bad rap anyway?

    In order to suffer from lead's poisonous effects you need to either ingest it or inhale it.

    Does anyone eat or sniff solder???
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  9. #9
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    I think the impetus was the EU's RoHS initiative, which, I believe, was an over-reaction to a problem.

  10. #10

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    Asbestos is another one. We know that ship worker that worked with the stuff got serious problems. Still, we used to use asbestos in break lining for cars. A friend of mine used to run a Bear Brake shop. When changing brakes he'd take an air hose ( no mask on ) and blow the old brake dust off. All, shops did this as far as I know when I was a kid. Guess what, no similar issue with asbestos for those working in the brake industry. I suspect it was related to the particle size. It was better to completely outlaw the stuff, rather than spend time to figure out how it worked.
    Lead in solder is similar.
    Dwight

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