Non-destructive Inspection of Flip-Chip BGA Solder Ball Defects Using Two Laser Beam Probe Ultrasonic Inspection Technique

The implementation of surface mount ball grid array (BGA) technologies in microelectronics industry has given way to the manufacturing of even more compact systems with reduced size and pitch of solder bumps that are increasingly challenging to inspect for their quality assurance. Current non-destructive inspection methods such as X-ray, and Acoustic Microscopy techniques have limitations in identifying defects. The low cost, non-destructive Laser Beam Probe Ultrasonic Inspection (LBPUI) technique has the potential to overcome these limitations and enable rapid assessment of chip packages on and off the assembly line. In this study, Flip Chip BGA packages subjected to bend testing are inspected using the LBPUI technique. Two optical fiber probes are used to carry pulsed Nd:YAG laser energy to the surface of the FCBGA package to induce ultrasound in the package. The quality of solder balls are assessed by analyzing the out-of-plane displacement responses on the surface of the package as measured by a laser interferometer. The results from LBPUI technique are validated with the results of destructive cross-sectional analysis.