THE EFFECT OF MATERIAL PROPERTIES AND LENS CHARACTERISTICS ON UHF SAM INSPECTIONSAuthor: James C. P. McKeon
Company: Sonix, Inc.
Date Published: 2/10/2004 Conference: Pan Pacific Symposium
When UHF transducers are used, attenuation effects further complicate the situation. Since water attenuation effects increase exponentially with frequency, it is necessary to minimize the amount of water between the transducer and the sample surface (i.e. the water path) when doing UHF inspections. This means that the water path cannot always be adjusted to account for changes in material thickness, and a transducer with an appropriate focal length must be selected. In previous work it has been shown how Geometric Refraction Theory can be used to determine the appropriate transducer focal length and water path to inspect a particular interface within a package.
However, this work focused on transducer frequencies below the UHF level. When UHF frequencies are used, there is a discrepancy between the theoretically predicted and experimentally obtained values. In this paper, this issue is examined in detail for flip chip samples.
Keywords: SAM, microelectronics, transducers.
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