Further investigation into the use of acoustic micro imaging for analyzing flip chip integrity and failure modes

Acoustic micro imaging is a nondestructive method to evaluate flip chip attach which has shown promising results. Defects such as pre-existing voids in the solder joints, non-wet of the solder to the chip and to the substrate bond pads are examples of what has been observed. Acoustic microscopes utilize high frequency ultrasound to examine the internal features in materials and components. The instrument used in this study was a C-SAM (C-Mode Scanning Acoustic Microscope) operating in the reflection mode at frequencies of 100 to 180 MHz. A previous paper demonstrated results on flip chip test samples which contained known induced defects at the chip/bump and bump/substrate interfaces. Using these samples the optimum techniques for inspection of the flip chip attach were developed. The work presented in this paper is a continuation of the previous study concentrating on developments in using higher frequency analysis (above 150 MHz) in the reflection mode, and using through transmission mode at high frequencies for flip chip evaluation