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.

This paper describes the detection capability of micro delamination in ICs according to the transducer frequency of SAM (Scanning Acoustic Microscopy) equipment through a case study of non-destructive failure analysis. The analysis of scanning acoustic microscopy is non-destructive, but is difficult to define micro de-lamination or micro crack. In this study, two SAM systems and various transducer frequencies were used to detect micro de-lamination on the lead finger area. In the results of non-destructive analysis by utilizing two systems, one SAM detected the micro delamination but the other SAM did not define micro delamination with C-scan mode. To confirm an accurate delamination phenomenon, we analyze the destructive analysis under cross-sectional inspection and the micro de-lamination was observed. The cause of non-detection for micro delamination is not due to the difference between equipments, but due to the transducer frequency. This paper will be concluded with a discussion on what kind of transducer frequency are selected according to distance from package surface to chip surface, package materials, and micro de-lamination thickness.