Pad crater detection using acoustic waveform analysis

Initial studies have shown that acoustic emission detection may prove an effective technique for pad crater monitoring. Implementation concerns include pad crater locating accuracy and the ability to discriminate between different types of events. This study found that the direction of wave propagation in the circuit board laminate has a significant effect on the event locating calculation due to orientation-dependent acoustic velocity, and that adjustment of the acoustic velocity based on the orientation between event location and transducers can improve locating accuracy to approximately 1 mm. In addition, the use of cumulative acoustic energy is demonstrated as a simple and effective metric for determining the onset of pad cratering. An alteration to the present test method is proposed that would improve the precision, decrease the throughput time, and decrease the cost of the test.