title: Micromachining and validation of the scanning acoustic microscope spatial resolution and sensitivity calibration block for 20-230 MHz frequency range.
abstract: Scanning acoustic microscopy (SAM) is used as a routine non-destructive test tool for different diagnostic examinations: detection of defects such as microcracks, delamination, disbonding, inclusions, subsurface features in materials such as pores and cracks. SAM can be operated in a wide frequency range from Megahertz to Gigahertz. SAM measurement spatial resolution is diffraction limited by the wavelength of the acoustic wave in particular medium and also depends on individual transducers geometry. Actual SAM spatial resolution can be determined by measuring calibrated lithographically formed microstructures in high acoustic impedance materials. Numerical acoustic signal simulation method, based on the diffraction approach, was employed for the selection of the calibration block pattern geometry and linear dimensions of the elements. Universal calibration block for SAM operating in a 20-230 MHz frequency range was micromachined in high acoustic impedance ceramic substrates. Differently spaced (from 18 to 185 µm) lines of the same width and different widths (from 17 to 113 µm) but similar spacing lines were imposed in alumina ceramics employing one step lithography process, i.e. femtosecond laser ablation. Proposed SAM calibration pattern linear dimensions were characterized employing optical and scanning electron microscopy. Finally the samples were measured with SAM employing different frequency transducers and results were compared with the numerical simulations. It was obtained that resolution of SAM operating with 230 MHz transducer is not worse than 40 µm.
authors.affiliation: Institute of Materials Science, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania Department of Physics, Kaunas University of Technology, Studentų Str. 50, Kaunas LT-51368, Lithuania tomas.tamulevicius@ktu.lt regina.rekuviene@ktu.lt.
authors.forename: Tomas
authors.initials: T
authors.lastname: Tamulevičius
authors.affiliation: Institute of Materials Science, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania.
authors.forename: Linas
authors.initials: L
authors.lastname: Šimatonis
authors.affiliation: Institute of Materials Science, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania.
authors.forename: Orestas
authors.initials: O
authors.lastname: Ulčinas
authors.affiliation: Institute of Materials Science, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania Department of Physics, Kaunas University of Technology, Studentų Str. 50, Kaunas LT-51368, Lithuania.
authors.forename: Sigitas
authors.initials: S
authors.lastname: Tamulevičius
authors.affiliation: Ultrasound Research Institute, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania.
authors.forename: Egidijus
authors.initials: E
authors.lastname: Žukauskas
authors.affiliation: Ultrasound Research Institute, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania tomas.tamulevicius@ktu.lt regina.rekuviene@ktu.lt.
authors.forename: Regina
authors.initials: R
authors.lastname: Rekuvienė
authors.affiliation: Ultrasound Research Institute, Kaunas University of Technology, K. Baršausko St. 59, Kaunas LT-51423, Lithuania.
authors.forename: Liudas
authors.initials: L
authors.lastname: Mažeika
keywords: alumina; calibration block; femtosecond laser micromachining; scanning acoustic microscope (SAM); sensitivity; spatial resolution