Die stacking package technology continues to become the trend of manufacturing integrated circuits (IC) today. This primary design offers smaller and thinner packages that would optimize board space and assembly cost. Consequently, this packaging technology has posed challenges in conducting failure analysis. Nondestructive techniques like acoustic microscopy are bound for advancement to make them feasible for use in this packaging technology. This paper will present frequency domain imaging in the field of acoustic microscopy as applied in the detection of delamination defect on a stacked die package. Fast Fourier Transform (FFT) was used as an algorithm to reconstruct and reveal the delamination defect which was not clearly detected in time domain imaging of the package. Frequency domain imaging was found to offer a better image contrast of delamination. This gives the failure analyst another approach to characterize the location and extent of delamination defect, a set of information that is substantial in the root cause analysis of adhesion related failures in stacked die packages.