The elastic properties of IC packaging materials (molding compounds and underfills) are measured nondestructively, over a microscopic area, in this study. The first application involves determining the engineering moduli of molding compounds (MP8000CH, MP190ML, 6300HA and 7320) from a nondestructive measurement of ultrasonic velocities. The second application involves the characterization of processing flaws in flip-chip packages to a) unambiguously identify delaminations (or voids) from resin rich areas, and b) quantitatively estimate the relative change in filler content. Concomitant changes in elastic properties of the underfill are also determined. Regions of filler segregation, exhibiting a lower impedance of about 3.9 MRayl (26% lower) are estimated to have a Young’s modulus of 7 GPa (50% lower) and a CTE of 41 x 10-6/°C (57% higher than the base material). Techniques presented in this paper have potential application in advanced process control, yield management and in analysis of package reliability.