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Breaking epoxy glue spots before desoldering ICs

Discussion in 'Electronic Repair' started by N_Cook, Dec 20, 2011.

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  1. N_Cook

    N_Cook Guest

    Say 100 plus SMD IC with 8 or so glue spots under
    Anyone have a successful method of using that hole in the pcb, if present. I
    force in 2 of the smallest jeweller's blades but I'm not convinced they do
    much, hoping there is no tracery hidden under. Then 2 wire loops under the
    IC with tension over them to assist pull off. Freezer spray while letting
    the hot air gun heat up - for those like me without the "proper" facilities.
    Anyone make a jig clamp[ed to the board to force a plunger into the hole ?
    if so how much force expressed per pin or whatever to break or at least
    strain the glue bond but without mechanically pushing off IC and traces with
    it
     
  2. Is there any way you can push a thin screwdriver blade under the IC, then
    twist? I'd expect THAT to pop the IC loose.
     
  3. N_Cook

    N_Cook Guest


    There is only about 1/3 mm of free space between rear of IC body and the
    pcb. I may try putting a joggle in the stem of the blades and grind the
    blades to a shallower angle and reduce the width and maybe that will be
    possible.
     
  4. N_Cook

    N_Cook Guest

    I've got inundated with work. I will be , sometime, taking some 1mm diameter
    high carbon steel and grinding to a shallow tapering blade and then tapering
    the edges a bit. Locally heating and trying to put in an elbow. Then a pair
    of these could get in either side with 0.3mm gap and each turned to expand
    to 1mm . I guess, would put in enough force to break some of the glue spots
    at least, and not the traces
     
  5. Charles

    Charles Guest

    "Jon Elson" wrote in message

    I think the component glue is easily softened at high temperatures.
    I think that is by design, so during reflow, when the solder melts the
    glue allows the component to be lowered fully into the solder. So, if you
    were to heat the entire chip to reflow temperatures, the glue would likely
    be quite soft. A hot-air desoldering rig ought to do the job perfectly.

    Jon

    Good post Jon. The glue melts before the solder does.
     
  6. N_Cook

    N_Cook Guest


    I precool the IC body with freezer spray though. When I grind down the glue
    spots it smells like standard epoxy
     
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