A dead short on a power rail is one of the most maddening faults in electronics. The multimeter reads “0 ohms” between VCC and ground, but it won’t tell you where. The defect could be a solder bridge under a 0.4mm-pitch BGA, a cracked ceramic capacitor that failed short, or a sliver of copper left behind during fabrication. The board looks pristine. The schematic is no help. So how do you find a fault you cannot see? You make it reveal itself with heat. A short is a low-resistance path, often just milliohms. Push current through it and that resistance dissipates power as P = I²R, concentrated almost entirely at the defect. Everywhere else, current spreads across wide copper planes and dissipates next to nothing. The fault becomes a tiny, intense heat source, and heat is something you can chase. The move is to make that heat visible: - Coat the suspect region in freeze spray, typically tetrafluoroethane, flash-cooling the surface to roughly -50°C and leaving a uniform layer of white...