Ultrasonic guided waves have the potential to inspect integrated circuit (IC) packages using wave based techniquesdue to excellent sub surface penetration through metallic as well as dielectric material. Guided waves in aheterogeneous composite assembly such as an IC package have modes with complex dispersion characteristics due tomultiple layers of material with intricate geometry. No analytical solution exists for predicting dispersion in highlyanisotropic composites. Numerical methods, such as the finite element method, have been used to model dispersion incomposites, however these methods are computationally intensive and not feasible for predicting dispersion in ICpackages. In this paper, the time-frequency characteristics of guided waves propagating through a complex IC arestudied using the synchrosqueezing transform (SST). This is a transform that has been shown to be robust to boundedsignal perturbations, to provide highly localized time and frequency information for highly nonlinear modes, and toreconstruct the signal corresponding to each mode. Reference ultrasonic guided wave signals are collected for the ICpackage in its healthy and damaged states using piezoelectric transducers to characterize the dispersion modes in theexcitation region. Initial results demonstrate that the dispersive mode information from the extracted SST ridgesprovide an effective damage indicator for IC packaging.
展开▼
