Chosen Solution

I have a 0 ohm resistance short to ground on VDD_main. Because there is no resistance I can’t find the cause of the short with my heat camera. There are only 2 things that come to mind.

A physical short has been caused by some kind of debris or misplacement which I just can’t find even with cleaning and searching thoroughly, or

A surface mount component has failed causing a 0 ohm short to ground. Is this likely and what type of component could cause this?

Usually, the culprit for most shorts is a capacitor as they are placed between VDD and ground. However, there are hundred of capacitors on the PP_VDD_MAIN line so you want to avoid having to remove them all to find the short. Understanding the history of the device and the circumstances leading up to the failure may give you some clues as to where to focus your efforts. You can also try to apply a lower voltage, say 2V directly to the PP_VDD_MAIN line, bypassing the Tristar/Tigris circuitry, as well as most IC’s. That may allow the thermal camera to pick up a heat signature from the offending component. You can also leave the device in this condition for a short while to see if anything “lights up” because with enough time, even a small trickle current will heat up the offending component a bit.