I recommend that you view some of Sorin’s repair videos where he uses a thermal camera to identify shorted components…. There are many such videos on his channel !
https://youtube.com/@electronicsrepairschool?si=NLJ-2PS4l8qY4MtDNorthridgeFIX also uses thermal imaging for finding shorted components.
https://youtube.com/@northridgefix?si=LJjuOpvxMleZ3YUsBasically a thermal imaging camera can easily identify the areas of a PCB that become hot due to a shorted component. You need to apply a low stimulation voltage of around 1V with a constant current limit of around 1A to 3A, depending upon the situation. Be warned that some lab power supplies do not like working into a short and disconnect their output so little to no current flows in the PCB. Sorin talks about this in one of his videos on buying a power supply. The original power adapter of a laptop will often go into protection mode if a short is present so do not use that to power the laptop. With a constant current of 1A present on a PCB, any shorted component on that power rail will normally reveal itself on the thermal camera. Make sure that you apply the stimulation voltage to the power rail of interest after any LDO or DC-DC converter if they are not part of the investigation. Some heavy duty components, such as large MOSFETs can dissipate a lot of heat to the PCB ground plane so more current may be needed to reveal shorts within these components.
You have not stated which thermal imaging device you are using. If it is one of the very inexpensive very low resolution types from China you may find it more challenging to locate the failed component. Anything of decent quality with a true physical resolution of more than 80x60 pixels will work for PCB inspection but 256x192 physical pixels, or more, is a better tool for the job.
Thermal imaging cameras have revolutionised the laptop and mobile phone repair industries with respect to quickly tracking down shorted components on PCB’s. It is the time that they save the tech that makes them so desirable in a commercial setting. In terms of cost for a thermal camera…. We have never had it so good ! Well done for wanting to learn about this technology in the PCB repair environment. You may wish to research add-on inexpensive ZnSe close-up lenses, both DIY and commercial, on this forum.
If you watch a good few of the videos that Sorin has produced, you will learn a lot about common faults on laptops and the use of the thermal camera where a short or very low impedance is present on a power supply rail.
The dedicated thermal imaging area of this forum is a good place to ask any thermal imaging related questions that you may have and for information on making a close-up lens etc.
Fraser