Resistive Interconnection Localization (RIL) is a new scanning laser microscope analysis technique that directly and rapidly localizes defective IC vias, contacts, and conductors from the front side and backside. RIL uses a scanned laser to produce localized thermal gradients in IC interconnections during functional testing. A change in the pass/fail state with localized heating of the IC identifies the failing site. The technique reduces the time to locate a resistive via from months to minutes. The sources of defective vias, the physics of RIL signal generation, and examples of RIL analysis are presented.