Acoustic microscopy

Ultrasonic microscopes consist of a spherically focused transducer submerged in an incompressible medium (water, for example) and attached to precision positioners. Resolution is limited by spherical aberration caused by diffraction at the medium/ sample interface and by the precision of the positioners. Standard resolution is on the order of 100 ftm. Finer focus enhances resolution, but drastically increases the time required to get data. Fine-focus acoustic microscopy may be used to find critical flaws in high-stress portions of a device, but even reducing the volume of 

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Briggs A., Kolosov O. Acoustic Microscopy for Imaging and Characterization // Materials Research Society Bulletin - 1996. - 21, 10. - P. 30-35. 

AM Acoustic microscopy [100] High-frequency acoustic waves are rastered across sample Surface and below-surface structure... 

B1.19.4.2 SCANNING NEAR-FIELD ACOUSTIC MICROSCOPY (SNAM)... 

Guenther P, Fischer U Ch and Dransfeld K 1989 Scanning near-field acoustic microscopy Appl. Phys. B 48 89 Williams C C and Wickramasinghe FI K 1986 Scanning thermal profiler App/. Phys. Lett. 49 1587... 

Acoustic emission tests Acoustic insulation Acoustic measurements Acoustic microscopy Acoustic spectroscopy Acoustic waves... 

The brief history, operation principle, and applications of the above-mentioned techniques are described in this chapter. There are several other measuring techniques, such as the fluorometry technique. Scanning Acoustic Microscopy, Laser Doppler Vibrometer, and Time-of-flight Secondary Ion Mass Spectroscopy, which are successfully applied in micro/nanotribology, are introduced in this chapter, too. 

Scanning acoustic microscopy (SAM) is a relatively new technique which broke through in the mid-seventies and was commercialized recently. The SAM uses sound to create visual images of variations in the mechanical properties of samples. The ability of acoustic waves to penetrate optically opaque materials makes it possible to provide surface or subsurface stmctural images nondestmctively, which might... 

The acoustic microscopy s primary application to date has been for failure analysis in the multibillion-dollar microelectronics industry. The technique is especially sensitive to variations in the elastic properties of semiconductor materials, such as air gaps. SAM enables nondestructive internal inspection of plastic integrated-circuit (IC) packages, and, more recently, it has provided a tool for characterizing packaging processes such as die attachment and encapsulation. Even as ICs continue to shrink, their die size becomes larger because of added functionality in fact, devices measuring as much as 1 cm across are now common. And as die sizes increase, cracks and delaminations become more likely at the various interfaces. 

Rugar, D., Cryogenic Acoustic Microscopy, Ph.D. thesis, Stanford University, 1981. 

Atalar, A., "An Angular Spectrum Approach to Contrast in Reflection Acoustic Microscopy, /. Appl. Phys., Vol. 49, 1978, pp. 5130-5139. 

Blau, P. J., and Simpson, W. A., Applications of Scanning Acoustic Microscopy in Analyzing Wear and Single-Point Abrasion Damage, Wear, Vol. 181-183,1995, pp. 405 12. 

Karnaukhov V.N, Yashin V.A. and Krivenko V.G. (1985). Microspectrofluorimeters. Proceedings of First Soviet -Germany International Symposum. Microscopy, Fluorimetry and Acoustic Microscopy. Moscow, p.160-164. Reigosa Roger, M.J. and Weiss, O. (2001). Fluorescence technique. In Handbook of Plant Ecophysiology Technique, (Ed., M.J. Reigosa Roger) Pp. 155-171. Kluwer Academic Publishers, Dordrecht. 

The Li-Loos intimate contact model was verified for compression molded unidirectional graphite-polysulfone and graphite-PEEK (APC-2) laminae and graphite-PEEK (APC-2) cross-ply laminates. The degrees of intimate contact of the unidirectional and cross-ply specimens were measured by optical microscopy and scanning acoustic microscopy, respectively. The predicted degrees of intimate contact agreed well with the measured values for both the unidirectional and cross-ply specimens processed at different temperature and pressures. 

In the following example, scanning acoustic microscopy is combined with optical microscopy to measure intimate contact at the ply interfaces of a [0o/90o/0°]r graphite-PEEK laminate. First, eight holes, 1.5 mm (0.059 in.) in diameter, were drilled into the composite specimen. These holes, shown in Figure 7.12, were used to locate where on the composite specimen the scanning acoustic microscope images were taken. 

The intimate contact data shown in Figure 7.16 were obtained from three-ply, APC-2, [0°/90o/0o]7- cross-ply laminates that were compression molded in a 76.2 mm (3 in.) square steel mold. The degree of intimate contact of the ply interfaces was measured using scanning acoustic microscopy and image analysis software (Section 7.4). The surface characterization parameters for APC-2 Batch II prepreg in Table 7.2 and the zero-shear-rate viscosity for PEEK resin were input into the intimate contact model for the cross-ply interface. Additional details of the experimental procedures and the viscosity data for PEEK resin are given in Reference 22. 

Fig. 2.1. A lens for high-resolution acoustic microscopy in reflection. The central transparent part is a single crystal of sapphire, with its c-axis accurately parallel to the axis of the cylinder. The sandwich structure at the top is the transducer, with the yellow representing an epitaxially grown layer of zinc oxide between two gold electrodes. The pink shaded areas within the sapphire represent the plane-wavefronts of an acoustic pulse they are refracted at the lens cavity so that they become spherical in the coupling fluid. A lens for use at 2 GHz would have a cavity of radius 40f[Pg.8]

Fig. 8.9. Stress fields at the end of a trench etched in a 15f

The significance of acoustic micrographs like this one does not come solely, or even primarily, from the fact that the cells are living. It comes also from the fact that what you are seeing in Fig. 1.5 is contrast from the mechanical structure of the specimen. In cases where this is the property of primary interest, acoustic microscopy offers the possibility of seeing it directly with submicron resolution. 

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