A simple method is devised for measuring the detection impedance in the acoustic impedance method of detection of unbonds and is based on an equivalent circuit of the detector. On the basis of the measured detection impedance, theoretical exploration is directed toward increasing the detection sensitivity for an unbond by properly choosing some of the detector parameters. The theoretical analysis is found to agree fairly well with the experimental results. In the case of unbond detection the sensitivity is increased by 5 times or more.