Shear Wave Acoustic Imaging of Microelectronic Ceramics

Abstract

Annular lenses, used in the practical shear wave imaging of ceramics, are developed in this paper. The theoretical analysis of the distribution of the focused acoustic field in Al₂O₃ shows that the longitudinal wave reflective signal can be suppressed to 2OdB below the shear wave signal reflected from the shear wave focus point, if an 8° aperture absorbing disk is placed at the centre of the lens, but the shear wave field are only changed a litter bit. Therefore the shear wave reflective pulse can be esily extracted from reflective pulse train. Several experiment, such as internal voids detection in A1₂O₃ and Al₂O₃-glass sealing interface imaging etc. , are also shown in this paper, which further demonstrates that the annular lens is very useful for realisation and exploitation of shear wave imaging.