Observation of a sub-surface defect in sapphire by Rayleigh wave reflection in the scanning acoustic microscope

An asymptotic description of the acoustic signature of a crack breaking the surface of an otherwise homogeneous, isotropic elastic material for a line focus, scanning acoustic microscope is constructed. The Debye approximation is used to calculate an incident focused beam whose profile falls off continuously at its edges. The wavefields scattered from the surface are constructed as Fourier integrals that are approximated asymptotically. Included in the asymptotic approximations are the leaky Rayleigh waves, which play a crucial part in the acoustic signature. Explicit expressions for the incident and scattered wavefields are given. The acoustic signature is calculated by using an electromechanical reciprocity identity to relate the wavefields in the coupling fluid to the voltage at the terminals of the microscope’s transducer. Several ways of evaluating this identity for an unbroken surface are explored and are shown to be asymptotically equivalent. The acoustic signature of a surface-breaking crack is then calculated by assigning to the crack reflection and transmission coefficients for the leaky Rayleigh wave and then using geometrical elastodynamics to construct the scattered wavefields. Explicit expressions for the acoustic signature of the cracked surface are given. Moreover, an explicit expression for the reflection coefficient of a Rayleigh wave reflected from a surface-breaking crack is given.

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Skin stripping method using proteases to evaluate structural stability by a scanning acoustic microscope

10.26226/morressier.578f37fdd462b8028d88f347 ◽

2016 ◽

Author(s):

Katsutoshi Miura

Keyword(s):

Structural Stability ◽

Acoustic Microscope ◽

Stripping Method ◽

Scanning Acoustic Microscope

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Development of an acoustic microscope to measure residual stress via ultrasonic Rayleigh wave velocity measurements

10.31274/rtd-180813-11915 ◽

1995 ◽

Author(s):

Jane Carol Johnson

Keyword(s):

Residual Stress ◽

Rayleigh Wave ◽

Wave Velocity ◽

Velocity Measurements ◽

Acoustic Microscope ◽

Rayleigh Wave Velocity

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Signature Analysis of Package Delamination Using Scanning Acoustic Microscope

ISTFA 1996: Conference Proceedings from the 22nd International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa1996p0287 ◽

1996 ◽

Author(s):

S.X. Li ◽

K. Lee ◽

J. Hulog ◽

R. Gannamani ◽

S. Yin

Keyword(s):

Failure Analysis ◽

Early Stage ◽

Signature Analysis ◽

Acoustic Microscope ◽

Reflow Soldering ◽

Moisture Expansion ◽

Scanning Acoustic Microscope ◽

Package Reliability

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.

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Failure Analysis of Flip-Chip Interconnections Through Acoustic Microscopy

ISTFA 1996: Conference Proceedings from the 22nd International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa1996p0277 ◽

1996 ◽

Author(s):

O. Diaz de Leon ◽

M. Nassirian ◽

C. Todd ◽

R. Chowdhury

Keyword(s):

Failure Analysis ◽

Large Scale ◽

Flip Chip ◽

Ultrasonic Waves ◽

Acoustic Microscopy ◽

Acoustic Microscope ◽

Chip Technology ◽

Ball Joints ◽

Non Destructive ◽

Scanning Acoustic Microscope

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.

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