Development of C-Line plot technique for the characterization of edge effects in acoustic imaging: A case study using flip chip package geometry

•Numerical modelling and simulation of acoustic wave propagation in flip chip packages•Development of C-Line plot technique for the characterization of edge effects in acoustic imaging•Edge effect in acoustic images of flip chip packages is mainly attributed to the UBM structure.•Investigated the impact of the transducer focal point and the spot size on the edge effect

Edge effect is a common phenomenon observed in acoustic micro-imaging of microelectronic packages. In this paper, using flip chip package geometry as a test vehicle, finite element modelling is carried out to study the fundamental mechanism of the edge effect phenomenon. C-Line plot technique is developed for the characterization of edge effects in acoustic C-scan images, in particular solder joint C-scan images. Simulated results are compared to experimental results. Results reveal that edge effect generation is mainly attributed to the under-bump-metallisation structure. In addition, through analysis of the C-Line profile of edge effects, the impact of the transducer focal point and the spot size on the edge effect is investigated. Results show that slight off-focus can reduce the severity of the edge effect in which image sharpness is a trade-off.