Abstract: Semiconductor chips are core functional components of all semiconductor packages. The failure analysis of chips is a complex and precise job, and there is large difference between chips of different specified functions. Based on the failure analysis methods for general chips, this paper introduces the failure analysis method for laser distance measuring sensors with abnormal function. In this paper, electrical and PCB testing was the first step for narrowing the analysis of function failure area, and then fault localization was performed by I-U curve and OBIRCH. At last, after the chip delaying and the plasma FIB cross section, the position and appearance of the failure point was observed by SEM. It is found that the failure mode is through-hole melting of metal layers, consistent with the failure mechanism. The results provide useful information for chip design, production process improvement and even client applications.