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Best Practices in Accelerating FEA
in Abaqus, Ansys®,
and NX Nastran
Dr. Gil Sharon
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Speaker Bio: Gil Sharon
o Senior Application Engineer. email:
[email protected]
o Research focus:
o Mechanical reliability of electronic systems and
components
o Multidisciplinary reliability of complex electro mechanical
systems
o Characterization and modeling of material behavior
o Physics of failure of electromechanical and MEMS system
o Mechanical performance of flip chip packages
o Doctoral research
o Solder reliability
o MEMS structures characterization
o Embedded components failure analysis
o Particle beam accelerator mechanical fatigue.
mailto:[email protected]
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Agenda
o Overview
o Board and BGA model creation
o Inserting a board to an enclosure
o Abaqus/ANSYS WB
o Adding a stiffener
o ANSYS classic
o Nastran as the solver
o New feature
o Creating a model for BGA packages
o Via modeling
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Overview
o Finite element analysis of can be used to simulate several
issues in board design
o Vibrationo Random vibration
o Harmonic vibration
o Modal Frequency analysis
o Board bendingo In circuit test (Static structural)
o Mechanical shock (Transient dynamic)
o Thermo-mechanical induced issueso Solder fatigue analysis
o Stresses in vias during reflow
o Warpage
o This webinar concentrates on how Sherlock can accelerate the
analysis capabilities of FEA solvers.
o Faster model creation
o Automated processing of FEA results to reliability
predictionso In some cases
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Board and BGA Model Creation
o A PCB model consists of:
o Components
o Leads/BGA solder balls
o Component body
o Board
o Copper
o Resin
o Laminate
o Stiffeners/mounts
o Enclosure or chassis is not part of the board
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o BGA models consist of:o Solder Balls
o Custom Patterns
o Laminate
o Die
o Overmold/ Bare die
o Passives
o Laminate modelso Uniform properties
o Layer by layer
o Mosaic
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PCB Model in Sherlock
o Import the board from eCAD files
o Verify the component placement
o Location
o Rotation
o Enter the component properties
o Verify the board properties
o Export the board to FEA
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Open a Design File Directly From ODB++ “File.tgz”
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Design Capture - Graphic Verification
o Files Viewable As PCB Layerso Provides Feedback To The
User
o Users can modify, delete and add parts
o Users can modify mount pointso Boards can be stacked up
and
assembled together
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Verify Component Placement
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Verify the Part Properties
o Enter the component properties
o Loaded from part library
o Entered by hand
o Sherlock will calculate the reliability of components even if
they are not exported to the FEA
o Based on component location
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Verify the Board Properties
o From the material properties of each layer Sherlock
calculates:
o Thickness
o Density
o CTE x-y
o CTE z
o Modulus x-y
o Modulus z
o Using the built-in laminate data library
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Exporting the Board from Sherlock
o Right click and select “Export FEA Model”
o Select
option
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o Geometryo Selected components on the board
o Creates mount point, heat sink, wire bond etc.
o PCB geometry including drill holes and cutouts
o Assembly of all the parts in the correct locationo Tied
contacts for everything
o Merged mesh option
o Materialso Materials for each material
defined in Sherlock
o Material for the board
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Inserting a Board to an Enclosure (ANSYS WB)
o Export the model as a step file and import it to ANSYS
workbench
o Import the chassis file
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Inserting a Board to an Enclosure (ANSYS WB)
o Use the Sherlock plugin to read the materials for each
part and the board
o Apply the material of the case
o Mesh the model
o Run the analysis
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Inserting a Board to an Enclosure (ABAQUS)
o Export the model as an ABAQUS file and import it
o Import the enclosure, mesh and run
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Inserting a Board to an Enclosure (ABAQUS)
o Results in ABAQUS:
o After the analysis is completed we
can import the results to Sherlock for
reliability predictions
Board Inside
Case
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Inserting a Board to an Enclosure (ABAQUS)
o Imported results in Sherlock:
o After the analysis is completed Sherlock can export the
results with the usual report
Board In Abaqus Board In Sherlock
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Adding a Stiffener (ANSYS Classic)
o Export model as ANSYS APDL
o Read input from…
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Adding a Stiffener (ANSYS Classic)
o Model the additional bracket
o Apply the loads
o Run the analysis
o Import the results to Sherlock to produce a reliability
prediction
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NX Nastran and Sherlock
o New feature
o Sherlock can now use NX Nastran as an FEA solver
o Natural frequencies
o ICT
o Random vibration
o Harmonic vibration
o Mechanical Shock
o Sherlock can also export native NX Nastran files (*.bdf) that
can be opened and modified in the GUI
o Results from NX Nastran can be imported for analysis in
Sherlock
o The *.pch result files are supported
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Creating a Model for BGA Packages
o Example: overmold BGA with passives
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o Sherlock can export a detailed mesh for all the layers
of the BGA
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Creating a Model for BGA Packages
BGA LayoutBottom Layer
Detailed Mesh
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Creating a Model for BGA Packages
o Option for using the Sherlock calculated material properties
for each layer
o Sherlock can also export the Laminate/PCB as a uniform
material
o If you have material properties from test
o Simplification
PCB TopPCB Layout
BGA Bottom
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Creating a Model for BGA Packages
o Example: PoP BGA
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o Each package has a die, substrate and BGA balls
o The PoP BGA is overmolded
PoP DiePoP Overmold PoP Substrate PoP Solder
BGA Die
PCB
BGA Substrate BGA Solder
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Creating a Model for BGA Packages
o PoP BGA created in Sherlock
Detailed Ball
Sherlock Created Ball
o Sherlock will create all the BGA balls with a simplified
geometry
o It is up to the user to mesh the model in the FEA tool
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Creating a Model for BGA Packages
o Let’s take a closer look at a simpler PoP Package
PoP BGA
PoP BGA
Main BGA
PoP BGA Assembly in AbaqusPoP BGA Assembly in Ansys
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PoP BGA Example
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Via modeling
o Up until recently it was prohibitively expensive to model
plated microvias
o Model creation time
o Solvers
o Current solvers have the power necessary to compute results
for thermo-mechanical issues
o Via modeling is performed in Sherlock and exported to Abaqus
or Ansys
Flange
Buried Via Through Via
Stacked Via
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Via modeling – Scaling the Problem
o Mesh portions of the PCB
o Appropriate for many layers
o Mesh a complete board
o Low layer count
o A 10X10 [mm] area with a 50X50 [µm] mesh size
o Each layer will have 40,000 elements
o 8 layers will have 600,000 elements!!
Stacked Via
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Via Modeling - Model Methodology
o Automate the extraction of accurate three-dimensional
conductor geometry from traditional electronic CAD-to-CAM files
formats
o Gerber, ODB, IPC 2581, GDS II and MCM
o Interfaces between materials
o Identification of either vector data or image
representation.
o Circular features in positive (copper) and negative (laminate)
space are configured for mesh creation through defeaturing and
computation of arc length segments.
Sherlock Traces Original Layout
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Via Modeling – Closer Look
o Curved traces and other features are translated into
poly-lines using an advanced edge-detection algorithm developed by
DfR Solutions
o Segment-generating algorithm
o Users select four variables for Sherlock to smooth out small
features
Finer Features
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Via Modeling – Abaqus Model import
o Sherlock creates a Python script for ABAQUS
o The geometry is organized in selectable geometry sets
Finer Features
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Via Modeling – ANSYS Classic
o Sherlock creates an APDL script for Ansys
o The geometry is organized in selectable components
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Extra: Combine Sherlock FEA Features
Lead modeling
Trace modeling
PCB cutout
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Summary (If you remember nothing else…)
o Shorten model creation times for Abaqus, Ansys
Workbench, Ansys Classic and Nastran.
o Leverage Sherlock’s libraries and easy interface to
automate your analysis
o Import FEA results to Sherlock and produce a reliability
prediction
o Computing power is increasing and with it the model
complexity.
o Solving ~2M elements is not a problem
o Engineer time is more valuable than computer time
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Questions?
o Presenter email: [email protected]
o Sales contact: [email protected]
