A broadband model is proposed to describe the nature of ultrasonic pulses in multilayered systems with a sub-wavelength thickness layer. This model, which is targeted towards acoustic microscopy of microelectronic devices, can incorporate measured ultrasonic properties of electronic materials and predict the complete ultrasonic pulse-train for all the interfaces in an electronic device. The model is robust, and incorporates material and geometric variables commonly encountered in microelectronics applications. Results are presented to illustrate how delaminations and cracks with foreign material or moisture ingress can appear to be well-bonded and why acoustic images of interfaces with thin layers can sometimes give erroneous indications of the bond state.

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