Shop OBEX P1 Docs P2 Docs Learn Events
Chip Extraction Procedures? — Parallax Forums

Chip Extraction Procedures?

John A. ZoidbergJohn A. Zoidberg Posts: 514
edited 2010-10-11 11:50 in General Discussion
Hello there,

I've just gutted out an old radio-clock, and all it's left now it's a board with a radio circuitry, pushbuttons and a clock chip.

The thing is, the clock chip is the common-used LM8560 DIP in the earlier days of electronics, and I would like to keep it.

Unfortunately, it isn't even soldered with a socket. It is soldered directly onto the board.

Now, a question - should I desolder this casually without ever burning the chip, or must I use a hot-air rework to extract it carefully? Anyone done these before?

Comments

  • Clock LoopClock Loop Posts: 2,069
    edited 2010-10-11 09:10
    I have removed a very large DIP, by first soldering a long copper wire to all the pins using a large amount of solder. But like you mention, this will heat up the DIP like mad. So far, everytime I have done it, I use a fat solder gun head on high heat, making sure to quicky move up and down the long copper wire and solder back and forth many times getting the whole thing liquid, as I pry the DIP up with a flat edge of a flat head screw driver, working from one end to the other slowly.

    Practice using something you don't care about. I have replaced convergence chips for projection TV'S this way. And other IC's.

    It dosen't always work, but using a hot gun can't be much better as far as heating the thing up just as much.
  • LeonLeon Posts: 7,620
    edited 2010-10-11 09:13
    Desoldering braid works quite well. Levering the chip up with a screwdriver can be necessary.
  • Clock LoopClock Loop Posts: 2,069
    edited 2010-10-11 09:18
    Leon wrote: »
    Desoldering braid works quite well. Levering the chip up with a screwdriver can be necessary.

    I forgot about the braid!.

    This combined with a desoldering gun would work also!
    (and heat up the device much less)

    Both desoldering braid and the desoldering gun can be found at radio shack.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-10-11 09:20
    A lot depends on whether the board it's soldered to is single- or two-sided. If it's single-sided, you should be able to free the pins one at a time using solder wick. If it's two-sided with plated through-holes, you can still work one pin at a time, but you will need to heat the pin from the top side and use one of those plunger type solder suckers to get the solder out of the hole. (Sometimes you have to add more solder to "prime the pump".) If a few pins remain stuck, you can insert a thin-bladed knife under the chip and twist it to apply force to the pins as you heat each of the stuck ones in turn. Little by little the chip will come free.

    -Phil
  • John R.John R. Posts: 1,376
    edited 2010-10-11 10:10
    In worse case, one of these can be used to remove the rest of the PCB from the chip: PCB Board Remover You just have to be careful to make sure and leave the chip behind.

    John R.
  • KaosKiddKaosKidd Posts: 296
    edited 2010-10-11 10:18
    John R. wrote: »
    In worse case, one of these can be used to remove the rest of the PCB from the chip: PCB Board Remover You just have to be careful to make sure and leave the chip behind.

    John R.

    LMAO! That's what I call my "Child Quietator" !
  • TonyWaiteTonyWaite Posts: 219
    edited 2010-10-11 10:21
    The first thing I do is to cover the pins in surface-mount flux, then blob genuine *leaded* solder on top to get the melting point down; then when everything's hot, prise lightly with a scalpel.

    I use safety glasses to avoid getting solder splashes in the eye ...

    T o n y
  • kwinnkwinn Posts: 8,697
    edited 2010-10-11 10:21
    If you are not concerned with saving the board a hot air paint stripper can be used to heat the back of the board and melt the solder on all the pins at once. You will need a clip of some kind to pull the chip from the other side. I have removed all the ic's from a lot of boards using this method, and it works very well.
  • John A. ZoidbergJohn A. Zoidberg Posts: 514
    edited 2010-10-11 10:31
    Clock Loop wrote: »
    I forgot about the braid!.

    This combined with a desoldering gun would work also!
    (and heat up the device much less)

    Both desoldering braid and the desoldering gun can be found at radio shack.

    I'll get the braid from Farnell and in the electronics stores kilometers away if I have the time. Thanks. :)
    Phil Pilgrim (PhiPi) wrote: »
    A lot depends on whether the board it's soldered to is single- or two-sided. If it's single-sided, you should be able to free the pins one at a time using solder wick. -Phil

    Thankfully, it's single sided. So I might follow the instructions you have provided.

    Only one thing - they have deliberately bent four pins when the chip is inserted inside during the production. I could see the four pins slanting downwards instead of proudly standing up. I guess I need the wick already. :lol:
  • CannibalRoboticsCannibalRobotics Posts: 535
    edited 2010-10-11 11:01
    If you don't care about the board, a blow torch can work very well too.
    Lay the board on top of a glass of cool water, chip down. Heat the back of all pins simultaneously until the solder starts to flow. Tap the pins with the back of a spoon. Not too hard or you'll bend the pins. If the chip does not fall out, heat a bit more and tap again. The chip will usually just fall into the water after a couple of rounds. <<If it's an old mil spec ceramic body chip, leave the water out of the glass.>>
  • localrogerlocalroger Posts: 3,452
    edited 2010-10-11 11:50
    I second CannibalRobotics' suggestion, though I wouldn't bother with the glass of water. A cheap propane torch works fine, but you will burn the back of the PCB.
Sign In or Register to comment.