1. Initial Work on Acoustic Simulation using Ansys APDL
Presented by
Lee Chean Shen
General Engineering Research Institute
Electronic and Ultrasonic Engineering Group
Supervisors
Prof. Dave Harvey
Dr. Guangming Zhang
22 January 2010

2. Destructive & Non Destructive tools.
Introduction – Acoustic Microscopy
What is Acoustic?
Longitudinal wave which consists of compression and dilation
Infrasound
Audible
Ultrasound
Human Hearing
20Hz
20kHz
100kHz
Animal
Navigation &
Communication
Seismology
Medical Diagnostics.
Destructive & Non Destructive tools.
Destructive Ultrasound
(>10 W/cm2)
Sonochemistry
Welding
Cleaning
Cell Disruption
Kidney Stone Removal
Non-Destructive Ultrasound
(0.1 – 0.5 W/cm2)
Flaw detection
Medical Diagnosis
Sonar
Chemical Analysis

3. Introduction – Acoustic Microscopy
What is Acoustic Microscopy Imaging (AMI)?
Non-Destructive technique
Sensitive to voids, delaminations and cracks
Detects flaws down to sub-micron
Image nontransparent solids or biological materials
Study microstructures of specimen
X-Ray
AMI
Unreflowed Solder Bump, AMI presents better contrast of defect

4. Introduction – Acoustic Microscopy
Resolution characteristics of AMI technique.
Increasing frequency largely lowers depth penetration
Attenuation usually increase with frequency
Lower frequency reduces resolution
More information
captured
230MHz
50MHz

5. Introduction – Acoustic Microscopy
AMI Operational Characteristics - Transducer
Transducer is cut/tuned to specific frequency, typically three types;
Piezoelectric
High frequency, low power (MHz region)
Voltage applied to crystal, medium required
Transducer is cut to frequency
Magnetostriction (EMAT)
Metal core responds to magnetic field
Material dependant, no coupling required
Photoacoustic
Pulsed laser applied to specimen
Thermal wave phenomena
Very high frequency
Measures material properties

6. Introduction – Acoustic Microscopy
AMI Operational Characteristics - Medium
Tranducer lensed to modify beam focus
Ansys Model Construction
(results in Review section)

7. Introduction – Acoustic Microscopy
AMI Operational Characteristics - Medium
EMAT only applicable to specific materials
Photoacoustic may require protective layer
Piezoelectric - Couplant required
Usually deionized water
Reflection occurs at the interface between two mediums
Air has low acoustic Impedance (Z)
Z = ρV = density * sound velocity of medium
Water to Steel ratio ~ 20:1
Air to Steel ratio ~ 100,000: (near 100% energy reflected)
Pulse Echo
Change in
Impedance
(Interface)

8. Introduction – Acoustic Microscopy
AMI Operational Characteristics - Configuration
Two typical methods
Pulse Echo – Image derived from reflections (Popular)
Through Transmission – Image derived from received signal
Through Transmission
Pulse Echo
Gate

9. Issues Current issues facing AMI
Electronic packages are shrinking and/or stacking
Technique is approaching resolution limits
Image processing techniques not broadly reliable
Transducers have relatively narrow operational frequencies
Optimal frequency difficult to determine

10. Objectives Nonlinear acoustic Imaging
2nd order harmonic provides higher resolution
Common in medical acoustics
Require single frequency transducer
Penetration depth proportional to fundamental wave
Not all material generate harmonic waves
Generated waves needs to reach receiver
Explore implementation
on stacked (3D) die

11. Objectives Clarify defect detection mechanism
Limited published literature regarding subject
Primary focus on new generation 3D IC packages
Understand acoustic performance within 3D IC packages
Balance optimum resolution vs. penetration
Analyze defect detection mechanism of engineered faults

12. Methodology - Ansys What is Ansys?
Finite Element Multiphysics Simulation Software
Accurate simulation of complex coupled-physics behaviour
Broadly defined into two interface
Structural Mechanics
Explicit Dynamics
Electromagnetics
Fluid Dynamics
Acoustics
ETC
Ansys Mechanical APDL
Ansys Workbench

13. Methodology - Ansys What is Finite Element Method?
Complete system is distributed into a large number of discreet elements
Complex system of nodes which form mesh grids
Mesh grid contain material and structural properties
Area anticipating stress/load tend to have higher density of node
Mesh resolution increases computational time

14. Tetrahedral (triangular)
Methodology - Ansys
Comparison of Mesh Resolution
Models usually tested with multiple mesh resolution/configuration
Ensure circular areas are adequately smooth/circular
Mesh resolution and type fits geometry size
Generally “look right”, results largely determined by mesh quality
Tetrahedral (triangular)
Hexahedral (square)
Fine Mesh
Coarse Mesh
Coarse Mesh
Fine Mesh

15. Methodology - Ansys What is Ansys Mechanical APDL ? Also known as;
Ansys Classic
“Old” Ansys
Reliant mostly on
command lines and scripts
Primitive GUI

16. Methodology - Ansys What is Ansys Workbench?
Ansys with user friendly GUI
“Idiot-proof” Ansys
Powerful module based
project assembly/management

17. Review Transducer Simulation – Pressure Magnitude
1500m/s (water medium)
Ansys APDL
Mirror
Result
Mirror
Result
Main Lobes
Side Lobes

18. Review Transducer Simulation – Acoustic Lens
1500m/s (water medium)
Triangular 15 elements per wave
Expected shift of focus point
Node reaction to applied load
PCIRC,0,1,0,90
RECTNG,0,0.025,0,0.1
CYL4,0,0.25,0.2
(double radius)
pcirc,0,1,0,90
RECTNG,0,0.025,0,0.1
CYL4,0,0.15,0.1

19. Further Work Scale up transducer simulations to MHz region
Validate simulation with measured results
Implement Non-Linear simulation
General simulation cleanup
Introduce materials into focused region
Study acoustic defect detection mechanism

20. Thank You

21. Source & Citations Eindhoven University of Technology
The Principles of Medical Ultrasound
HyperPhysics Utrasound Guide – Georgia State University
CALCE – University of Maryland
Acoustic Microscopy Guide – University of Hawaii
Resolution improvement of acoustic microimaging by continuous wavelet transform for semiconductor inspection – LJMU GERI
Guang-Ming Zhang, David M. Harvey, Derek R. Braden.
The NDE Analysis of Tension Behaviour in Nicalon/SiC Ceramic Matrix Composites
Jeongguk Kim, Peter K. Liaw, Hsin Wang
Fundamentals of Ultrasonic Imaging and Flaw Detection – National Instruments
Phased Array Tutorial - Olympus
About HIFU – Maple Leaf HIFU
Finite-element method – McGill University
Introduction to Finite Element Analysis – Virginia Tech
Modeling and Meshing Guide, Chapter 7 – Ansys