Fig. 3: Simulated wave propagation at focused (Z0) and defocused position (Zn) using 100 MHz, 60° transducer for different time steps.

a Flow chart of the EFIT simulation. b EFIT simulation at the focused transducer position. c EFIT simulation at the defocused transducer position. The excitation and propagation of surface acoustic waves (SAW)s - see time steps 3 and 4 - are shown. The arrow marker in time step 3-4 highlights the generated SAWs at the surface. Time step 5 and 6 show the interaction of the SAWs with the TSV. The latter renders the possibility to detect inhomogeneities within the TSV based on the detected interference patterns. Intensity for the velocity ranges from yellow (high) to black (low).