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What makes 0603 LEDs stick to probe?

  1. Oct 4, 2014 #1
    Hi!

    I had an interesting chat with a physisist collegue of mine this week.

    Working with modern small electronic components I began to wonder why my extremely pointy probes, measureing the direction of the light emission diode, stuck so irritating hard to it that it could not break loose after I had established anode/cathode.

    I also had trouble releasing it from the nippers with the purpose of soldering it to the tiny PCB pads.

    So I asked my collegue why.

    The too obvious reply was sticky dirt but neither him nor me really believed that.

    Remember that these tiny LEDs weighs almost nothing.

    We further speculated that there might be some magnetism in the probes like it is possible to magnetize something iron-like just by moving a magnet back and forth (which also is a strange phenomena because do you really have to move the magnet?).

    I said that I don't believe that is the reason either and that is because the metal part of the LED is made of non-magnetic copper and tin so it doesn't matter if the probe or nippers is magnetic or not, I said.

    Then he had an idea that perhaps things just stick to each other if they are really close to each other.

    I did however refere to a scientific program I saw not so long ago that taught me that nothing really touches anything and this is due to the electromagnetic forces of the outermost electrons.

    So what is the correct answer?

    Best regards, Roger
     
  2. jcsd
  3. Oct 6, 2014 #2

    CWatters

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    Bit of googling...

    http://www.freetronics.com/pages/surface-mount-soldering-with-a-toaster-oven#.VDJmoGctDmQ
    http://forums.adafruit.com/viewtopic.php?f=42&t=13258&start=15
    http://www.hobbyelectronics.net/tec_smd-soldering.html
     
  4. Oct 8, 2014 #3
    I now agree that they seem ferrous but what is it whith that copper/tin/lead/gold alloy that is ferrous?

    Is there perhaps some iron involed also or what is it?

    And if it's iron or some other ferrous material, why?

    To me tinned copper should suffice.

    Best regards, Roger
     
  5. Oct 9, 2014 #4

    CWatters

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  6. Oct 9, 2014 #5

    f95toli

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    One candidate is nickel which is a very common "sticking layer" in electronics, a thin layer is deposited before the other metals to achieve better adhesion.
    And nickel is of course ferromagnetic.
     
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