| Inspection of solder joint interconnection has been a crucial process in the electronics manufacturing industry to reduce manufacturing cost, improve yield, and ensure product quality and reliability. New inspection techniques are urgently needed to fill in the gap between available inspection capabilities and industry requirement of low-cost, fast-speed, and highly reliable inspection systems. The laser ultrasound inspection system under development aims to provide a solution that can overcome some of the limitations of current inspection techniques. Specifically, the fully developed system will be an automated system that is capable of inspecting hidden solder joints with multiple defect types.;This research work includes the following aspects: (1) Inspection system integration and automation to improve system throughput and capability, system performance characterization by stability study and gage repeatability and reproducibility study, (2) Development and implementation of signal processing methods, including time-domain correlation coefficient analysis, auto-comparison method, and frequency-domain spectral estimation, to allow for fast and accurate interpretation of vibration signals, (3) Development of a finite element modal model followed by experimental validation. The modal analysis results indicate there are unique mode frequencies and mode shapes associated with certain solder joint defects, and (4) Study of the system's unique capability in detecting solder joint fatigue cracks. |
