A Scanning Acoustic Microscope (SAM) is a device which uses focused sound to investigate, measure, or image an object (a process called Scanning Acoustic Tomography). It is commonly used in failure analysis

Failure analysis

Failure analysis is the process of collecting and analyzing data to determine the cause of a failure. It is an important discipline in many branches of manufacturing industry, such as the electronics industry, where it is a vital tool used in the development of new products and for the improvement...

 and non-destructive evaluation. It also has applications in biological and medical research. The semiconductor industry has found the Scanning Acoustic Microscope useful in detecting voids, cracks, and delaminations within microelectronic packages.

History

The first scanning acoustic microscope was developed in 1974 by R. A. Lemons and C. F. Quate at the Microwave Laboratory of Stanford University

Stanford University

The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

. Many improvements to such systems have been made since in order to enhance resolution and accuracy.

Principles of operation

Scanning Acoustic Microscopy works by directing focused sound from a transducer at a small point on a target object. Sound hitting the object is either scattered, absorbed, reflected (scattered at 180°) or transmitted (scattered at 0°). It is possible to detect the scattered pulses travelling in a particular direction. A detected pulse informs of the presence of a boundary or object. The `time of flight' of the pulse is defined as the time taken for it to be emitted by an acoustic source, scattered by an object and received by the detector, which is usually coincident with the source. The time of flight can be used to determine the distance of the inhomogeneity from the source given knowledge of the speed through the medium.

Based on the measurement, a value is assigned to the location investigated. The transducer (or object) is moved slightly and then insonified again. This process is repeated in a systematic pattern until the entire region of interest has been investigated. Often the values for each point are assembled into an image of the object. The contrast seen in the image is based either on the object's geometry or material composition. The resolution of the image is limited either by the physical scanning resolution or the width of the sound beam (which in turn is determined by the frequency of the sound).

Medicine and Biology

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

Cytoskeleton

The cytoskeleton is a cellular "scaffolding" or "skeleton" contained within a cell's cytoplasm and is made out of protein. The cytoskeleton is present in all cells; it was once thought to be unique to eukaryotes, but recent research has identified the prokaryotic cytoskeleton...

. These studies are particularly valuable in investigating processes such as cell motility

Motility

Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...

.

• Flaw Detection

• Internal stress investigation

• Elastic property characterization

Some work has also been performed to assess penetration depth of particles injected into skin using needle-free injection

Ultrasonic Direct Microscopy

Ultrasonic Direct Microscope (UDM) base on measuring the ultrasonic signal directly. The conventional sensor include a level sensor that means that the measurement instrument attitude of the signal. ADM technique deal with ultrasonic signal as is . That make possible to produce modulate ultrasonic signal and to check not only the main frequency, and enable wide range in order to examine little chances in to material in test.

External links

• Applied Physics Letters. Early Lemons and Quate SAM paper
• Sonix. Manufacturer of SAM systems
• Sonoscan. Manufacturer of SAM systems,introduced the worlds first commercially available Acoustic Microscope (SLAM) in 1975
• KSI - Kraemer Sonic Industries GmbH. Manufacturer of SAM systems in Germnany.
• SAM TEC. Manufacturer of SAM systems in Germany, a subsidiary of KSI.
• Kibero. Manufacturer of a SAM system for biomedical applications.