Monday, September 9, 2019

Carefully look at the rework area after rework...!

Lead dropped on a SMD Capacitor causes short between GND and RESET Signal

One of the chip that I was working has a CAPACITOR on the RESET Signal as shown below


Now, I need to get some rework to be get done on the board. After the rework the Debugger / Programmer is not able to get access to the chip.

I have removed the debugger from the board Debug Connector.

The debug connector has 5 signals VCC, GROUND, XRES, CLOCK and DATA.

When I check the continuity between the XRES, CLOCK and DATA w.r.t. GROUND observed that XRES is shorted to GROUND. I initially thought the CAPACITOR is dead due to rework done.

But, when I checked with Hardware Engineer told me to check if there is any lead dropped on capacitor which might have caused this issue.
The capacitor is literally very small such as 0201 / 0402 package. On top of it there are wires running on the board which are unmovable due to the glue placed on the wires.


When I had a look carefully on the top of capacitor under a magnifying glass there is lead dropped on C1 Capacitor.

When the soldering technician removed the lead the debugger / programmer could get access to the Micro controller.

Thanks for reading the post and let me know your feedback...!

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