Acoustic Micro Imaging (AMI) has been used for years to evaluate microelectronic packages for the presence of internal defects. The drive in micro electronic packaging is to reduce the size of the components as much as possible to keep pace with the shrinking size of the end products. This leads to smaller/thinner packages with internal features and possibly defects that are approaching the resolution limits for conventional AMI. Recently AMI has been combined with Fourier transforms of the acoustic signal to produce frequency domain images. Previously features that were at or below the accepted resolution limits for a given frequency were not detected in the time domain images, however these features are revealed in the frequency domain images.