This paper describes the failure analysis methods used to characterize micro cracks that resulted in laser vias of printed circuit boards (PCBs) through case studies of destructive failure analysis. Defects such as cracks in laser vias of PCBs can cause open or low leakage failure mode of module due to improper cleaning during the PCB process, natural oxide films such as brown oxide, or physical forces by use. Therefore, it’s difficult to identify the causes of these phenomena unless proper analytical techniques are used. In this study, multiple analytical techniques are employed to characterize micro cracks in laser vias. The destructive analysis with cross section and ion milling process is used to detect and inspect an accurate micro crack phenomenon of laser via. The characterization analysis using TEM, EDX and SIMS equipment after separating laser vias from a PCB is used to analyze failure cause of micro crack in laser via. This paper will be concluded with a discussion about what physical analysis methods should be used to analyze the causes of micro cracks for laser vias of PCBs.