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I want to get to some pin signals on a mounted MCU, but it's a ball mounted / soldered one ...

Is there way to 'hack' underneath it to get some signals out? Any usual home-lab setup people came up with ?

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  • \$\begingroup\$ I would say it's almost impossible. Just removing it and resoldering it back on successfully is enough of a challenge. \$\endgroup\$
    – DKNguyen
    Feb 8 '20 at 7:53
  • \$\begingroup\$ Do you know if there are some special sockets for BGA's so that, you can un-solder the chip, connect that socket to the board, then drop the chip into the socket. .? Something like that .. \$\endgroup\$
    – v01d
    Feb 8 '20 at 8:12
  • \$\begingroup\$ This is a super ascended master Jedi ... level trick. Why do you want to do it? Is it impossible to achieve fully or in part by inference from available signals elsewhere? || Importantly, why do you want to connect AT the BGA device itself? - do the relevant PCB traces go somewhere else or are the pins unterminated? \$\endgroup\$
    – Russell McMahon
    Feb 8 '20 at 8:24
  • \$\begingroup\$ @v01d W2635A sit down and put down the coffee before you check the price. maybe you could design something like that using a stack of pcb for the column \$\endgroup\$
    – Jasen
    Feb 8 '20 at 8:25
  • \$\begingroup\$ @RussellMcMahon Because wanna get inside inside the MCU, may be connect emulator/debugger, and spy on it's code. Also dump internal flash contents. Wrt to available signals, haven't found yet on the board the routed out signals i want ... Also, is there a "home-made" X-Ray for PCB ?? Or 'cheap' one :P I want to look inside the layers. \$\endgroup\$
    – v01d
    Feb 9 '20 at 10:13
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perhaps fron below with very thin drill bit and lots of care.

it's peobably easier to remove the chip using hot air, and then glue and solder the probe wires in (eg: use #40 enammeled magnet wire) then re-ball and re-solder the BGA. I find that 800 grit sandpaper works well to strip fine magnet wire.

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  • \$\begingroup\$ hey thanks for answering, I will now try parse every point you have given here and do some googling. \$\endgroup\$
    – v01d
    Feb 8 '20 at 5:57
  • \$\begingroup\$ can you recommend a hot air (gun?) good for removing MCU chips like this? one that also can set temp accurate enough not to damage the chip. \$\endgroup\$
    – v01d
    Feb 8 '20 at 5:59
  • \$\begingroup\$ @Jasen You're not implying to solder it back to the PCB with a magnet wire sticking out from under the BGA, are you? Because the planarity of the BGA gets ruined easily enough by a bad reballing or even just bad plating on the PCB, let alone wire and glue being underneath the BGA. \$\endgroup\$
    – DKNguyen
    Feb 8 '20 at 7:55
  • \$\begingroup\$ yeah I am, use thin wire. and use the glue outside of the bga perimeter \$\endgroup\$
    – Jasen
    Feb 8 '20 at 8:04
  • \$\begingroup\$ a custom adaptor made from 2 sided flex pcb could be another option but that's likely to be no easier to apply than a few wires. and hard to get flat, something like W2635A is not an option for most home labs. \$\endgroup\$
    – Jasen
    Feb 8 '20 at 8:23

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