Trying to bring up the STM32H750 test board.
So far, not so good. 3V3 and ground are shorted.
There's no *obvious* defects other than the backwards test point that I found and removed.
Removed the U.FL outright in case it was melted from the rework or something, no luck.
Can't find anything obviously wrong solder joint wise.
The board only has 77 components on it, it's not particularly complex. Verified orientation of all ICs and the BGA balls I can see look properly soldered.
There's a few possible explanations here:
1) Solder defect under the BGA
2) Solder defect under the MAC EEPROM or oscillator
3) Cracked MLCC
4) Bad pinout that slipped through design review
5) Manufacturing defect on one board of the panel (I checked for shorts on a bare board after, but not on this board before populating)
Number 4 is probably the easiest to double check, just look at every Vdd and Vss ball and make sure they're hooked up right.
@azonenberg Small question related to (1): are dental Xray digital sensor and low cost sources usable (resolution, xray spectrum) to inspect small areas of pcb and see solder defects under typical packages?
Are there better low-cost option to do this kind of inspection?
