Diagnostic Method
Isolating low-resistance electrical failures within multilayer circuit boards requires diagnostic methods that penetrate the outer insulation layers. Modern subsurface leakage localization employs localized excitation techniques like laser stimulated thermal imaging to map internal current leakage paths. This method identifies the specific conductive filaments or dendrites that cause short circuits between adjacent traces.
It provides high resolution coordinates for the failure without requiring the disassembly of the substrate.
Signal Analysis
Detecting these leakage paths depends on measuring the current variation while scanning a laser across the circuit. This process uses the local temperature rise induced by the laser to alter the resistance of the leakage path. The resulting changes are monitored and processed to map the coordinates of the short circuit.
Failure Identification
Successful fault isolation is critical before undertaking any destructive physical analysis on high density assemblies. By combining this non-destructive thermal mapping with CAD layout files, the diagnostic tool shows whether the leakage originates from a lamination defect or from a solder bridge on an inner layer. This knowledge allows failure analysis labs to target their cross sectioning with high precision, saving both time and component resources.
It is an essential step in verifying the root cause of latent field returns.
