SAM is a non-invasive & non-destructive failure analysis technique that inspects for voids, cracks, delaminations in a sample.  SAM sends a focused sound wave through the package and interprets the change of the sound wave with the package. 

The following are the most common modes used in failure analysis of an IC.

• A-Scan Mode (Amplitude Scan) : is a real time oscilloscope waveform of the sound waves collected at a single X-Y section or point.
• C-Scan Mode (Confocal Scan) : is an image of acoustic reflection collected at the focused plane (X-Y plane) of interest at a particular depth (Z). The image plane is parallel to the surface of devic
• Through-Scan Mode : two separate transducers are used to send and receive acoustic waves. These transducers are positioned on opposite sides of the specimen.