Short on PP_VDD_Main but no heat

That happens some times. Heat is a byproduct of power and power is the current times the voltage drop across the component. The voltage drop is determined by the resistance so if you have a very low resistance short, there will be minimal power generated, hence very little heat.

Don’t let the value on the multimeter fool you, there is always some resistance in a dead short, usually in the milliOhm range.

So consider the following:

• If you have a 1 Ohm ( 1000 mOhms) short at 1 A, you have 1W of power being generated. If all that power is being generated through one component, you will definitely see a heat signature.
• At the other extreme, if you have a 1 mOhm short, you now have only 0.001W of power being generated and you will not see that at all, whether you use Rosin Flux or a FLIR camera.

There is a new tool out there called the “Short Killer”. You can find on Aliexpress or eBay. It can send up to 30A into a circuit which is usually sufficient for finding difficult shorts.