White Goo or Heatsink Removal on Circuit Board

Discussion in 'General Electronics Chat' started by hairykiore, Apr 5, 2012.

  1. hairykiore

    Thread Starter New Member

    Apr 5, 2012
    Hi..I need to identify a transister..Problem is its got this white goo round its leads that prevents my bending it slightly to read its lettering ...This white stuff has been liberally put on various parts all over the circuit board at the point of manufacture...I have tryed scraping it ,filing it but am apprehensive about damage ..I do not know it it reacts to heat ..I presume it doesn't but some expert hopefully will be able to give me a tip on if I can attack it???? Now there is an alternative ?? If I could remove the heatsink which would allow me to see the lettering...You can see the transistor and part of the heatsink in the photo attached....Now the alloy heatsink has two lugs which are soldered to the circuit board ..but this solder (if it is solder ) certainly will not melt with my soldering bolt ...I am really puzzled ..is it a special alloy solder ? Again I would be extremely grateful if anybody could advise me on the white goo removal OR what I see as a safer option ...how to remove the heatsink ..Thankyou ..HK
  2. jtrent

    New Member

    Mar 11, 2012
    The white goo in the picture you provided is simply an adhesive. It can be removed but it will take some patients. You can use a screw driver or something similar to pick at it from the outer edges inward. You just have to be careful and patient so as not to damage your transistor. Maybe you can just pick away enough to bend the transistor over to read the numbers.

    Manufacturers use adhesive in some parts of their product to hold a component in place until it can be soldered. That seems to be the case here. This is not heatsink compound because the transistor is not attached to the heatsink.
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
    That looks like epoxy, not the usual silicone. You may be able to chip or grind away enough with a tool but if the markings aren't obscured by it you can read them with a dental or inspection mirror.

    I wouldn't advise removing the aluminum heat sink unless it's absolutely necessary. If it's soldered, it will take a great deal of heat to unsolder since it sinks away heat from your iron as fast as you apply it.
    Last edited: Apr 6, 2012
  4. hairykiore

    Thread Starter New Member

    Apr 5, 2012
    hi..Thanks for you replies......I had tried to pick at it with a box knife ...I just feel that chances of being successful removing it without causing damage is impossible...If the heatsink is not able to be removed to enable me to get a clear view of the side of the transister it leaves me with the third option which I did think of .. an inspection mirror ....so tomorrow I will go up town and see if I can find a dental inspection or similar mirror ... Thanks HK
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    Ur soldering iron is enuf to slowly scrape away the epoxy.
  6. PackratKing

    Well-Known Member

    Jul 13, 2008
    not to be repetitive.....I run onto this a lot salvaging components.......
    is the goo pliable.....as in you push a knife blade on it, does it give, feel cushy - silicone - or is it rock solid....epoxy......
    If it is pliable, pick up some denatured alcohol [ the anhydrous variety ] in a pair of tweezers , and let capillary action pull it into all cracks / crevices / loose spots..........
    then with a suitable instrument that will engage the dollop without tearing it, gently wiggle or "worry " the stuff 'till it loosens up and will come off, likely in one piece.....

    KJ6EAD is right about unsoldering the sink..........it will drain heat dramatically from anything short of a Weller 350 watt or equiv.
  7. hairykiore

    Thread Starter New Member

    Apr 5, 2012
    Hi..Problem solved..R!f@@ was right ..it came off easily using the soldering bolt...which enabled me to carefully bend the transister to enable me to take a photo ...Thank you very much to all ..HK
  8. jimkeith

    Well-Known Member

    Oct 26, 2011
    I think this is hot melt glue