Scanning acoustic microscope
The first scanning acoustic microscope (SAM), with a 50 MHz ultrasonic lens, was developed in 1974 by R. A. Lemons and C. F. Quate at the Microwave Laboratory of Stanford University.
[2] First commercial SAM ELSAM, with a broad frequency range from 100 MHz up to 1.8 GHz, was built at the Ernst Leitz GmbH by the group led by Martin Hoppe and his consultants Abdullah Atalar (Stanford University), Roman Maev (Russian Academy of Sciences) and Andrew Briggs (Oxford University.
And unlike other non-destructive techniques such as X-Ray, CSAM is highly sensitive to the elastic properties of the materials it travels through.
For example, CSAM is highly sensitive to the presence of delaminations and air-gaps at sub-micron thicknesses, so it is particularly useful for inspection of small, complex devices.
[6] The technique makes use of the high penetration depth of acoustic waves to image the internal structure of the specimen.
Scanning acoustic microscopy works by directing focused sound from a transducer at a small point on a target object.
It can be focused to a specific target layer located in a hard-to-access area by changing the z-position with respect to the sample under testing that is mechanically fixed.
[6] 2D or 3D-dimensional images of the internal structure become available by means of the pulse-reflection method, in which the impedance mismatch between two materials leads to a reflection of the ultrasonic beam.
The reflected signal is monitored and sent to a synchronous display to develop a complete image, as in a scanning electron microscope.
- Fast production control - Standards : IPC A610, Mil-Std883, J-Std-035, Esa, etc - Parts sorting - Inspection of solder pads, flip-chip, underfill, die-attach - Sealing joints - Brazed and welded joints - Qualification and fast selection of glues, adhesive, comparative analyses of aging, etc - Inclusions, heterogeneities, porosities, cracks in material SAM can provide data on the elasticity of cells and tissues, which can give useful information on the physical forces holding structures in a particular shape and the mechanics of structures such as the cytoskeleton.
[9][10] Some work has also been performed to assess penetration depth of particles injected into skin using needle-free injection [11] Another promising direction was initiated by different groups to design and build portable hand-held SAM for subsurface diagnostics of soft and hard tissues [12][5] and this direction currently in the commercialization process in clinical and cosmetology practice.
