Non-destructive techniques for internal solder bump inspection of chip scale package-ball grid array package

Non-destructive inspection of Chip Scale Package-Ball Grid Array (CSP-BGA) package for anomalies related to continuity test failures specifically on the internal solder bumps, which connect the die to the Printed Circuit Board (PCB) substrate, is a challenge. Curve trace analysis can trace which internal solder bumps are involved but confirming its physical status needs more reliable and advanced nondestructive techniques. C-mode Scanning Acoustic Microscopy (CSAM) and Micro-Computed Tomography (μCT) scan were evaluated. Results of this paper showed that depending on the physical attribute of the bump anomaly, it could be seen either in μCT scan or CSAM. μCT scan will show those solder bumps with abnormal size or formation and CSAM using a 100 MHz transducer will show those bumps which fractured from its die pad connection. μCT scan can also be utilized for inspecting the metal traces, through hole vias and external solder balls of the PCB substrate. With these two non-destructive techniques, conventional destructive physical analysis techniques like mechanical cross-section, delayering and deprocessing are no longer required saving cycle time and cost. The samples are also saved for further electrical verification, fault isolation and destructive die-level physical analysis, if needed.