Nondestructive inspection of packaged microcircuits by aperture-type terahertz near-field imaging

Abstract

A scanning aperture-type terahertz near-field imaging system is developed to perform precise nondestructive testing on packaged aluminum etched antenna arrays, and surface imaging of a flexible gold electrode array, to obtain subsurface imaging and surface imaging. The resolution of subsurface imaging is 110 μm and 500 μm when the packaging (polyethylene terephthalate) thickness is 50 μm and 200 μm respectively, and the surface imaging resolution is 6 μm at 0.11 THz. An adaptive threshold segmentation algorithm of Hilbert scan combined with wavelet transform were employed to successfully suppress the noise of the imaging results due to the change of near-field distance. We also proposed a derivative filtering extremum threshold segmentation algorithm to effectively suppress severely uneven threshold distribution of the packaged aluminum etched antenna arrays.

Curved Synthetic Aperture Radar for Near-Field Terahertz Imaging

“…The radar imaging systems include multiple input multiple output SAR (MIMO SAR), interferometric SAR (InSAR) and tomographic SAR [22]- [26]. In [8], a THz near-field imaging system based on SAR has been developed for precise, high resolution NDT of packaged aluminium etched antenna arrays and for flexible gold electrode array surface imaging. Novel THz-SAR testbeds based on FMCW radar front-end and vector network analyser (VNA) are being investigated for short range applications including NDT, security/defence, material characterization and automotive [27].…”

“…To overcome this challenge, it has been suggested to collect THz signals in the near-field, thus breaking the diffraction limit and provide high spatial resolution [7]. The THz near-field is also classified as: 1) aperture type near-field and 2) aperture-less type near-field [8]. In the aperture type imaging, coherent measurements are implemented on an aperture and the object is focused by propagating the wave backwards to its exact location [1].…”

External bias dependent dynamic terahertz propagation through BiFeO3 film

“…THz domain of the electromagnetic spectrum is relatively less explored compared to the other regions of the electromagnetic spectrum. However, THz waves have extensive applications in several fields which include communications [3], biological sciences [4,5], semiconductor industry [6,7], non-destructive testing (NDT) [8][9][10], basic research [11][12][13], etc Because of the multiple practical applications, technologies related to THz devices have been rapidly developing through several avenues during the last few decades [14][15][16][17]. However, sustained progress in THz technology demands the development of THz components as well as novel materials responsive in this frequency range.…”