Cracking of multilayer ceramic capacitors (MLCCs) typically occurs during or after the solder assembly process, after which the capacitors are interconnected to other components on populated circuit boards. This limits the success of conventional non-destructive methods, such as measurement of insulation resistance or capacitance, or X-ray imaging, to characterize MLCCs and to identify those which are cracked. While electrical measurement techniques can be useful on electrically isolated MLCCs, interference from other interconnected components on the board renders these techniques useless in these cases. The ability of TDR to identify isolated cracked MLCCs was examined. Clear discrimination between healthy and cracked MLCCs of two different sizes was demonstrated. In further experiments, interconnected cracked MLCCs on PCB assemblies were evaluated and compared to healthy specimens on identical PCB assemblies. The results show that TDR holds promise for the identification of cracked interconnected MLCCs on printed circuit boards.
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