Non-destructive Failure Analysis of Various Chip to Package Interaction Anomalies in FCBGA Packages Subjected to Temperature Cycle Reliability Testing

Failure analysis and root cause investigation of various package anomalies are key criteria to predict the failures, and thus the life of a device after reliability testing. Currently, quality assurance teams depend on less reliable electrical resistance probe testing and destructive methods such as cross-sectioning and microscopy, for the failure analysis. However, a reliable non-destructive test is preferred for failure analysis to provide more accurate and efficient data. Laser Ultrasonic and Laser Interferometer (LULI) Inspection System is a non-contact and non-destructive system that can be used for failure analysis of package anomalies. This system uses pulsed laser to generate ultrasound within the sample and a laser interferometer to sense the surface displacement response. To predict an anomaly at a location on the test sample, the surface displacement response at that location on the test sample will be compared against the response at the same location on the reference sample. For this research, original Flip-Chip Ball Grid Array (FCBGA) samples were used to evaluate various chip-to-package anomalies including inner and outer layer substrate discontinuities, second level joint imperfections (like voiding), and pad cratering in the printed circuit board. This paper presents promising results that can circumvent time consuming cross sectioning of substrate layers and laborious sample preparation consistent with general failure analysis tactics to facilitate root cause investigation of various package anomalies using the nondestructive LULI inspection technique.