Customer Application Presentation ANSYS Solution for … · Customer Application Presentation ANSYS...
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1 © 2015 ANSYS, Inc. November 12, 2015 ANSYS Confidential
Customer Application Presentation
ANSYS Solution for PCB Reliability
Ankit Adhiya
Vamsi Krishna
Rohit Patchigolla
2 © 2015 ANSYS, Inc. November 12, 2015 ANSYS Confidential
PCB Overview
• A printed circuit board (PCB) mechanically supports and electrically connects electronic components.
• Printed circuit boards are used in almost all electronic products across industries.
Aerospace and Defense Consumer Electronics Automotive
Healthcare Oil and Gas
PCB in Controller System Audio System Engine Control Module LCD display module
PCB in Drill hole tool
© Baker Hughes
PCB in Attendant Controller Panel Engine control module ….
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DC-IR + Thermal Reliability Thermo-Mechanical Reliability
Mechanical Reliability
PCB Reliability
Large deformation when PCB subjected to random vibration
Cracks formation at interface between solder ball and PCB due to thermal cyclic loading
Hot spot on PCB due to trace heating
(© Alcatel Lucent, Intel, Sanmina) (© expertfea.com)
• A reliable PCB can ensure long lasting service and efficient operation of electronic components
• During manufacturing and operation, PCB is subjected to extreme environmental and operational conditions, which causes reliability issues
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Content
• DC-IR + Thermal Reliability
• Thermo-Mechanical Reliability
• Mechanical Reliability
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• DC-IR + Thermal Reliability
• Thermo-Mechanical Reliability
• Mechanical Reliability
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Background : Joule Heating
• What is Joule Heating?
• Joule heating / resistive heating is the process by which the passage of
electric current ( 𝐼 ) through a conductor of electrical resistance ( 𝑅 )
releases heat ( 𝑄 )
𝑄 = 𝐼2𝑅
• Why do we need to perform thermal reliability analysis on printed circuit / wiring boards?
• High current PCB’s are densely populated with components
• Reduction of trace and via dimensions
• Current densities increase
• Joule heating effects on copper traces Temperatures increase Reliability issues
PCB delamination and failure
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ANSYS Solution
PCB Thermal Reliability
Challenges Predict accurate temperature of PCB
Understanding both Thermal and Electrical physics and applications
Transfer data between different physics for accurate analysis
Accurate loss calculation with inclusion of Thermal effects
Automatic looping until DC losses & Thermal map are constant
SIwave transfers local Joule heating losses into Icepak
Icepak returns temperatures back to SIwave
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• Spatial Power Loss information from the DC-IR analysis (SIwave) is transferred to Icepak as a spatial Joule Heating map (modeled using 2D sources).
• Spatial Temperature information from the Thermal analysis (Icepak) is transferred to SIwave and interpreted as spatial thermal modifiers for electrical conductivity.
SIwave-DC – Icepak Bi-direction Coupling Overview
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Siwave DC Solutions
WorkFlow Wizard, making the Simulation setup more convenient and user-friendly.
Import Settings
Verify / Modify Geometry, Materials, and Circuit Elements
Setup Simulation
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Siwave DC Solutions
Quickly Identify:
• High Currents in Vias
• Current Crowding in Copper
• High Power Loss Regions
• Automated report generation with user defined pass/fail criteria.
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SIwave – Icepak Coupling : Accurate PCB Thermal Analysis
Coupled DC-IR Simulation Wizard • Imports Power map to Icepak and Export Temperature modifiers
back to SIwave • Minimal inputs from Electrical engineer • Automated coupling till convergence
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Icepak Results : Temperature Comparison
Without Trace heating With Trace heating
Simulation Type Maximum
Temperature
Without Joule Heating 40.0 C
SIwave-Icepak Coupling (First Iteration)
69.0 C
SIwave-Icepak Coupling (Last/Third Iteration)
76.6C
1st Iteration 2nd Iteration 3rd Iteration
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Value to Customer
Value to Customer
- Ease of coupling multiple physics - Accurate prediction of PCB Temperature - Quick turnaround time
Customer using ANSYS Solution
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• Thermal Reliability
• Thermo-Mechanical Reliability
• Mechanical Reliability
(© Alcatel Lucent, Intel, Sanmina)
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Background : Warpage and Solder Joint Reliability
• Why do we need to perform thermal reliability analysis on printed circuit / wiring boards?
• Electronic components are made up of different materials
• Mismatch of CTE results in thermo-mechanical stress in PCB and Solder joint
interconnect
• Excessive warpage on PCB can lead to weaker joints there by result in product failure
Step I: Silicon, solder bump and substrate bond at reflow temperature (>180 C)
Step II: Cool down from 180 C to room temperature
Step III: Underfilling, cure at 150 C, Cool to room temperature
Step IV: Lid attach/encapsulation at ~120C, cool down to room temp
Step V: Ball attach & reflow at > 180C,
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ANSYS Solution
PCB Warpage
Challenges Predict local warpage accurately during reflow
Understanding effect of belt speed, geometry of package
Accurately calculating the local material properties
Trace in Mechanical
ACT Extension for Copper and FR4 distribution
Reflow Profile applied for Warpage
Warpage calculation in Mechanical
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Comparison of Warpage with and without Trace (Z Direction deflection)
Without Trace With Trace
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ANSYS Solution
Solder Joint Life Cycle Estimation
Challenges Predict time to failure
Understanding simulation procedure for life cycle estimation
Prediction using Darveaux method
Life cycle estimation
ACT Extension to Automate Simulation Process
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Current Procedure
Calculate Strain Energy
Calculate No of Cycles for
Crack Initiation
Calculate Crack Growth Rate
Calculate Fatigue life
based on Joint length
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Darveaux Method – Cycles to Failure Fatigue Post-processing via ACT
Scope Geometry /Named Selection
Command Snippet formerly used
Advantages: • APDL commands understanding not required • Multiple Unit system for entering Fatigue Input parameters
Crack growth correlation constants
Cycle time and Diameter of solder Joint
ACT Extension
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Darveaux Method – Cycles to Failure Fatigue Post-processing
Results Table
Equivalent Plastic Strain
Quarter Symmetric Package Model
No of cycles to failure
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Value to Customer
Value to Customer
- Accurate prediction of PCB local material properties - Accurate Deformation, stress and Life prediction - Quick turnaround time
Customer using ANSYS Solution
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• Thermal Reliability
• Thermo-Mechanical Reliability
• Mechanical Reliability
(© expertfea.com)
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Background : Random Vibration
Many common processes result in random vibration • Parts on a manufacturing line
• Vehicles travelling on a roadway
• Airplanes flying or taxiing
• Spacecraft during launch
Courtesy: NASA
The amplitudes at these frequencies vary randomly with time. • We need some way of describing and quantifying this excitation.
April 27, 2015
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Background : Random Vibration
• Transient analysis is not an option since time history is not deterministic
• Instead using statistics the sample time histories are converted to Power Spectral Density (PSD)
function, a statistical representation of load time history
Image from "Random Vibrations Theory and Practice" by Wirsching, Paez and Ortiz
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ANSYS Solution
PCB Mechanical Reliability
Challenges Predict the response of a PCB under Random Vibration Loadings
Predicting fatigue life due to Random Vibration Loadings
PSD
Time History
Frequencies & Mode Shapes
Response PSD
Sigma Values
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Assumptions & Restrictions
The structure has • No random properties
• No time varying stiffness, damping, or mass
• No time varying forces, displacement, pressures, temperatures, etc applied
• Light damping
• Damping forces are much smaller than inertial and elastic forces
The random process is
• Stationary (does not change with time)
• The response will also be a stationary random process
35 © 2011 ANSYS, Inc. April 27, 2015
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General Procedure Overview
Inputs:
• Structure's natural frequencies and Mode shapes
• Input PSD Curve
Outputs:
• 1σ ( 2σ & 3σ) displacements and stresses (all quantities assume Gaussian i.e. Normal
distribution with zero mean)
• Response PSD (RPSD) curves
For ex: Maximum displacement, Umax = 0.15 indicates 68% (1σ) probability that Umax will be 0.15 or less.
• 95% probability (2σ) that Umax will be 0.15 x 2 or less
• 98% probability (3σ) that Umax will be 0.15 x 3 or less
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Random Vibration For real models with multiple DOFs • RPSDs are calculated for every node in every free direction at each frequency
• RPSDs can be plotted for each node in a specific direction versus frequency
• A RMS value (sigma value) for the entire frequency range is calculated for every node in
every free direction
• sigma values (i.e. 1σ, 2σ & 3σ) can be plotted as a contour for the entire model
for a specific direction.
Z direction
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3 Sigma Acceleration
Displacement RSPD
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Value to Customer
Value to Customer
- Accurate prediction of behavior of an electronic component under random vibrational loadings
- Quick turnaround time
Customer using ANSYS Solution
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Summary
• ANSYS Solution helps to predict reliability for different analysis in a PCB lifecycle
• Automation scripts and customization makes it easy to simulate all the interconnected analysis
• Simulation driven product development allows
• Quick turn around time and
• Reduced time to market
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Acknowledgement Required:
Slide 2 images are from ANSYS Advantage. Need to acknowledge Baker Hughes.
Copyright Restricted: No Download
Slide 3 and 14 the Solder join reliability if from a paper in Google so should not be shared. Random Vibration image on Slide 3 and 23 is from Youtube it should not be shared.
http://www.sanmina.com/pdf/resources/effectof_lead_mixing_levels.pdf https://www.youtube.com/watch?v=gAnhZTAZlDs
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