A Scanning Acoustic Microscope Study of the Small Caries Lesion in Human Enamel

1986 ◽  
Vol 20 (4) ◽  
pp. 356-360 ◽  
Author(s):  
S.D. Peck ◽  
G.A.D. Briggs
1987 ◽  
Vol 1 (1) ◽  
pp. 50-63 ◽  
Author(s):  
S.D. Peck ◽  
G.A.D. Briggs

The scanning acoustic microscope can be used to obtain images of caries lesions in longitudinal sections of human enamel. The contrast in the acoustic images is unique in that it arises from changes in the elastic properties across the surface of a specimen. The contrast depends sensitively on the distance between the specimen and the focal plane of the lens, and this can be exploited to reveal features of interest. Comparison of an acoustic micrograph, a polarized light micrograph, and a microradiograph of a caries lesion reveals that the elastic properties of enamel are strongly dependent on the level of mineralization within the tissue. Acoustic micrographs show regions similar to those seen with the other techniques, but with greater sensitivity to small changes in mineralization.


1989 ◽  
Vol 68 (2) ◽  
pp. 107-112 ◽  
Author(s):  
S.D. Peck ◽  
J.M. Rowe ◽  
G.A.D. Briggs

The scanning acoustic microscope gives strong contrast from small caries lesions in sections of human enamel. The uniqueness of the acoustic microscope lies in its ability to image elastic properties. In addition to revealing the extent and the shape of lesions, the microscope may also be used to measure the elastic properties point by point across an area of interest. Since enamel is anisotropic, measurements of the Rayleigh velocity and attenuation were made as a function of direction on a section of sound enamel. The velocity was greatest parallel to the prism axis, and the attenuation was least in this direction. Measurements of V(z) across a section through a lesion are presented. The variation of attenuation can be interpreted in terms of the development of demineralization, initially along prism boundaries and then along cross-striations. The variation of velocity indicates a substantial reduction of elastic stiffness in the lesion.


Author(s):  
S.X. Li ◽  
K. Lee ◽  
J. Hulog ◽  
R. Gannamani ◽  
S. Yin

Abstract Package delaminations are often associated with electrical and package reliability problems in IC devices. Delaminations caused by electrical-over-stress (EOS) and moisture expansion during reflow soldering have shown different delamination patterns. A Scanning Acoustic Microscope (SAM) can be used to detect package delaminations. Understanding these delamination signatures can help us quickly identify the failure cause at an early stage of the failure analysis.


Author(s):  
O. Diaz de Leon ◽  
M. Nassirian ◽  
C. Todd ◽  
R. Chowdhury

Abstract Integration of circuits on semiconductor devices with resulting increase in pin counts is driving the need for improvements in packaging for functionality and reliability. One solution to this demand is the Flip- Chip concept in Ultra Large Scale Integration (ULSI) applications [1]. The flip-chip technology is based on the direct attach principle of die to substrate interconnection.. The absence of bondwires clearly enables packages to become more slim and compact, and also provides higher pin counts and higher-speeds [2]. However, due to its construction, with inherent hidden structures the Flip-Chip technology presents a challenge for non-destructive Failure Analysis (F/A). The scanning acoustic microscope (SAM) has recently emerged as a valuable evaluation tool for this purpose [3]. C-mode scanning acoustic microscope (C-SAM), has the ability to demonstrate non-destructive package analysis while imaging the internal features of this package. Ultrasonic waves are very sensitive, particularly when they encounter density variations at surfaces, e.g. variations such as voids or delaminations similar to air gaps. These two anomalies are common to flip-chips. The primary issue with this package technology is the non-uniformity of the die attach through solder ball joints and epoxy underfill. The ball joints also present defects as open contacts, voids or cracks. In our acoustic microscopy study packages with known defects are considered. It includes C-SCAN analysis giving top views at a particular package interface and a B-SCAN analysis that provides cross-sectional views at a desired point of interest. The cross-section analysis capability gives confidence to the failure analyst in obtaining information from a failing area without physically sectioning the sample and destroying its electrical integrity. Our results presented here prove that appropriate selection of acoustic scanning modes and frequency parameters leads to good reliable correlation between the physical defects in the devices and the information given by the acoustic microscope.


Author(s):  
Li Na ◽  
Jawed Khan ◽  
Lonnie Adams

Abstract For stacked die package delamination inspection using C-mode acoustic microscope, traditional interface and thorough scan techniques cannot give enough of information when the delamination occurs in multi-interfaces, and echoes from adjacent interfaces are not sufficiently separated from each other. A thinner thickness in the stacked-die package could complicate C-mode scanning acoustic microscopy (CSAM) analysis and sometimes may lead to false interpretations. The first objective of this paper is to briefly explain the CSAM mechanism. Based on that, some of the drawbacks of current settings in detecting the delamination for stacked-die packages are presented. The last objective is to introduce quantitative B-scan analysis mode (Q-BAM) and Zip-Slice technologies in order to better understand and improve the reliability of detecting the delamination in stacked-die packages. Therefore, a large portion of this paper focuses on the Q-BAM and Zip-Slice data acquisition and image interpretation.


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