TQFP Reverse Socket. Atmega 8A 2u.

Discussion in 'Embedded Systems and Microcontrollers' started by mohitjindal, Apr 19, 2013.

  1. mohitjindal

    Thread Starter Active Member

    May 25, 2009
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    Hi,
    Please see the photo i attached. It is 32 pin atmega 8a tqfp ic. I want to access its 4 pins. Is there any reverse socket or pin grab hooks so that i can access pins/legs from top.
    I don't want to remove the IC.
     
  2. kubeek

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    Sep 20, 2005
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    You can use thin magnet wire and solder it to the pins.
     
  3. mohitjindal

    Thread Starter Active Member

    May 25, 2009
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    From where i can get magnet wire ?
    I already tried soldering. Destroyed 2 boards.
     
  4. kubeek

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    Sep 20, 2005
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    Old motors, solenoids, transformers, you name it.
    How did you manage to do that? You need to have the wire tinned, then just add a bit of flux and you should be able to temporarily attach the wire with just one touch of the soldering iron.
    But I can see on the other pads that you are probably using way too much heat an hold it there for too long.
     
  5. ErnieM

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    Apr 24, 2011
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    Could you indicate what 4 pins you need to grab on the pic? Since you already have 2 scrap boards you could use them as templates to make a pogo pin holder.

    That's a board with spring loaded pins you place over your target to pick up some points to probe, drive, whatever you need to do.
     
    Last edited: Apr 19, 2013
  6. mohitjindal

    Thread Starter Active Member

    May 25, 2009
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    I want to access pins 2; 4 ; 13 and 14. But I saw the photo of pogo pins.I think they are used to fit in holes not above the tiny legs of IC.
    Also please tell me how to make magnet wires "tinned" ?
     
  7. ErnieM

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    Apr 24, 2011
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    That's nice and if you indicate which pins these are on your picture I too would know where they are, and may have other suggestions of attachment methods.
    I think not.

    [​IMG]
     
  8. mohitjindal

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    May 25, 2009
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    I attached the photo with pins indicated. The black dot on the IC Is pin 1. And pin 13 is just before 14.
     
  9. ErnieM

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    Apr 24, 2011
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    Looks like...

    pin 1: is common to the top pad of unpopulated R21. Larger target then pin itself.

    pin 6: is common to pin 4 and to via below R21. Uninsulated vias such as that make very good probe points.

    pin 13: shows not trace... dead board may be better to check if you can remove the IC.

    pin 14: trace to some part to the right, can't see any marking on that part but tab may be better probe point then pin itself.

    You have the board to check if this is true.
     
  10. mohitjindal

    Thread Starter Active Member

    May 25, 2009
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    Here is the schematic diagram. Pdf.
    I want to grab pin/legs 2,4,13 and 14.
     
  11. kubeek

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    Sep 20, 2005
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    Then go ahead and do it. Or what is the problem?
     
  12. mohitjindal

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    May 25, 2009
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    Problem is that the legs are very thin. TQFP. I don't want to burn atmega ic. 13 and 14 are very close.
     
  13. kubeek

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    I know the pins are quite close together, but you said you have more boards on which you could practice the soldering.
    Also does the board have some components on the other side? What is that green thing in the schematic?
     
  14. mohitjindal

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    May 25, 2009
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    Yes it has some tiny components on other side. Forget the green thing. Its just an explanation.
     
  15. takao21203

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    Apr 28, 2012
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    Do you need to access the chip inside the circuit?

    Desoldering a TQFP32 is very easy. It takes 2 minutes with a 50W iron.
     
  16. kubeek

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    What kind of soldering iron do you have? Does it have temperature regulation?
     
  17. takao21203

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    Apr 28, 2012
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    Yes it has full regulation, soldering station.

    For desoldering TQFP ICs, I crank it up a bit, and I use lead solder.
    Filling up all 4 sides of the IC with solder, then melting them up in succession until I can lift off the IC.

    Done even with TQFP80.

    The IC won't burn from that.

    Then hold at 90 degree and pull off the solder from all the pins.
     
  18. kubeek

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    Sorry takao, I meant what does OP have ;)
     
  19. mohitjindal

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    May 25, 2009
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    I want to solder wire on 4 legs. Not desoldering.
    I have 8watt micro tip solder iron.
    Yes i want to access the black ic having 32 legs.
     
  20. takao21203

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    Apr 28, 2012
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    OK.

    1. Use a tiny piece of proto PCB + superglue it to the chip upside down.
    2. Solder cut solid wire for instance from LEDs into the proto piece holes.
    3. Bend these wires until they almost touch the IC pin from the top.
    4. Make the solder connection.

    It is much more doable than magnet wire, or any kind of cable.

    SOLID WIRE is the key factor.
    HOLDING IT IN PLACE + BENDING IT.

    You only need a bit superglue, don't attach it permanently.
     
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