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Acoustic Micro Imaging (AMI) has become an established method to evaluate the quality and reliability of IC packages from the standpoint of package integrity. Ultrasound is sensitive to variations in the elastic properties of materials and is particularly sensitive to locating air gaps (delaminations, cracks and voids). Microscopic feature sizes in flip chip, SOI, and MEMS devices has necessitated imaging at much higher ultrasonic frequencies to improve the axial and spatial resolution. However, sufficient penetration and working distance must be maintained to access the various internal layers of the devices. Higher frequency pulse- echo transducers have recently been developed and are in use. However, factors such as fluid path attenuation and fluid couplant temperature need to b