A microcontroller IC was failing at apparently random I/O pins.
This is an optical image of the chemically decapsulated device.
This is a BSE SEM image of the decapsulated device.
This image shows a displaced ball bond with an elemental spectrum of the bottom of the crater.
This is a higher magnification image of the bond crater.
Bond cratering can occur at apparently random bond pads likely due to variation & non-perfect planarity of the die attachment.