Plastic Encapsulated Microcircuit (PEM) 3D Acoustic Microscope Image - Application Note 2515
Sample & Method
A 3V image is made by scanning a sample several times at increasing depths, and by assembling all of the resulting planar scans into a 3-dimensional acoustic solid.
Here the acoustic solid has been tilted to achieve a meaningful view. Echoes from the top surface of the package have been retained and appear as the yellow “roof” of the sample. A portion of this area has been removed electronically to view the interior. Surrounding the die are four yellow-red vertical structures that indicate a popcorn crack. Popcorn cracks are the result of the explosive expansion of moisture during reflow, and often originate under the die paddle and extend upward.