Initial Work on Acoustic Simulation using Ansys APDL

Presented byLee Chean Shen

General Engineering Research InstituteElectronic and Ultrasonic Engineering Group

SupervisorsProf. Dave Harvey

Dr. Guangming Zhang

22 January 2010

Introduction – Acoustic MicroscopyWhat is Acoustic? Longitudinal wave which consists of compression and dilation

Human Hearing

20Hz 20kHz 100kHz

Animal Navigation &

Communication

Seismology Medical Diagnostics.

Destructive & Non Destructive tools.

AudibleInfrasound Ultrasound

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

Introduction – Acoustic MicroscopyWhat 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

Introduction – Acoustic MicroscopyResolution characteristics of AMI technique. Increasing frequency largely lowers depth penetration

• Attenuation usually increase with frequency

Lower frequency reduces resolution

230MHz 50MHz

More informationcaptured

Introduction – Acoustic MicroscopyAMI Operational Characteristics - TransducerTransducer 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

Introduction – Acoustic Microscopy

Tranducer lensed to modify beam focus

Ansys Model Construction(results in Review section)

AMI Operational Characteristics - Medium

Introduction – Acoustic MicroscopyAMI Operational Characteristics - MediumEMAT 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 ~ 100,000:1 (near 100% energy reflected)

Pulse Echo

Change in Impedance(Interface)

212

212

ZZ

ZZR

Introduction – Acoustic MicroscopyAMI Operational Characteristics - ConfigurationTwo typical methods

• Pulse Echo – Image derived from reflections (Popular)

• Through Transmission – Image derived from received signal

Through Transmission

Pulse Echo

Gate

IssuesCurrent 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

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

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

Objectives

Methodology - AnsysWhat is Ansys?

Finite Element Multiphysics Simulation Software

Accurate simulation of complex coupled-physics behaviour

Broadly defined into two interface

• Ansys Mechanical APDL• Ansys Workbench

• Structural Mechanics• Explicit Dynamics• Electromagnetics• Fluid Dynamics• Acoustics• ETC

Methodology - AnsysWhat 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

Methodology - AnsysComparison 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

Fine MeshCoarse MeshFine MeshCoarse Mesh

Tetrahedral (triangular) Hexahedral (square)

Also known as; • Ansys Classic• “Old” Ansys

Reliant mostly on command lines and scripts

Primitive GUI

What is Ansys Mechanical APDL ?

Methodology - Ansys

What is Ansys Workbench?

Ansys with user friendly GUI

“Idiot-proof” Ansys

Powerful module based project assembly/management

Methodology - Ansys

ReviewTransducer Simulation – Pressure Magnitude30,000Hz @ 1500m/s (water medium)Ansys APDLMirror Result Mirror Result

Side Lobes

Main Lobes

Review

Node reaction to applied load

PCIRC,0,1,0,90RECTNG,0,0.025,0,0.1 CYL4,0,0.25,0.2(double radius)

pcirc,0,1,0,90RECTNG,0,0.025,0,0.1 CYL4,0,0.15,0.1

Expected shift of focus point

Transducer Simulation – Acoustic Lens30,000Hz @ 1500m/s (water medium)

Triangular mesh @ 15 elements per wave

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

Thank You

Source & CitationsEindhoven University of Technologyhttp://w3.chem.tue.nl/en/the_department/research_groups/process_development/research/ultrasound/

The Principles of Medical Ultrasoundhttp://www.mrcophth.com/commonultrasoundcases/principlesofultrasound.html

HyperPhysics Utrasound Guide – Georgia State Universityhttp://hyperphysics.phy-astr.gsu.edu/Hbase/sound/usound.html

CALCE – University of Marylandhttp://www.calce.umd.edu/general/Facilities/sam.htm

Acoustic Microscopy Guide – University of Hawaiihttp://www.soest.hawaii.edu/~zinin/Zi-SAM.html

Resolution improvement of acoustic microimaging by continuous wavelet transform for semiconductor inspection – LJMU GERIGuang-Ming Zhang, David M. Harvey, Derek R. Braden.

The NDE Analysis of Tension Behaviour in Nicalon/SiC Ceramic Matrix CompositesJeongguk Kim, Peter K. Liaw, Hsin Wanghttp://www.tms.org/pubs/journals/JOM/0301/Kim/Kim-0301.html

Fundamentals of Ultrasonic Imaging and Flaw Detection – National Instrumentshttp://zone.ni.com/devzone/cda/tut/p/id/3368

Phased Array Tutorial - Olympushttp://www.olympus-ims.com/en/ndt-tutorials/transducers/construction/

About HIFU – Maple Leaf HIFUhttp://www.hifu.ca/physician/about_hifu.php

Finite-element method – McGill Universityhttp://audilab.bmed.mcgill.ca/AudiLab/teach/fem/fem.html

Introduction to Finite Element Analysis – Virginia Techhttp://www.sv.vt.edu/classes/MSE2094_NoteBook/97ClassProj/num/widas/history.html

Modeling and Meshing Guide, Chapter 7 – Ansyshttp://www.kxcad.net/ansys/ANSYS/ansyshelp/Hlp_G_MOD7_3.html