Customer Application Presentation ANSYS Solution for … · Customer Application Presentation ANSYS Solution for PCB Reliability ... the best of their knowledge,

1 © 2015 ANSYS, Inc. November 12, 2015 ANSYS Confidential

Customer Application Presentation

ANSYS Solution for PCB Reliability

Ankit Adhiya

Vamsi Krishna

Rohit Patchigolla


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 ….


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


Content

• DC-IR + Thermal Reliability

• Thermo-Mechanical Reliability

• Mechanical Reliability


• DC-IR + Thermal Reliability




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


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


• 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


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


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.


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


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


Value to Customer

Value to Customer

- Ease of coupling multiple physics - Accurate prediction of PCB Temperature - Quick turnaround time

Customer using ANSYS Solution


• Thermal Reliability



(© Alcatel Lucent, Intel, Sanmina)


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,


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


Comparison of Warpage with and without Trace (Z Direction deflection)

Without Trace With Trace


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


Current Procedure

Calculate Strain Energy

Calculate No of Cycles for

Crack Initiation

Calculate Crack Growth Rate

Calculate Fatigue life

based on Joint length


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


Darveaux Method – Cycles to Failure Fatigue Post-processing

Results Table

Equivalent Plastic Strain

Quarter Symmetric Package Model

No of cycles to failure


Value to Customer

Value to Customer

- Accurate prediction of PCB local material properties - Accurate Deformation, stress and Life prediction - Quick turnaround time



• Thermal Reliability



(© expertfea.com)


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


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


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


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


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


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

37 © 2011 ANSYS, Inc. April 27, 2015

3 Sigma Acceleration

Displacement RSPD


Value to Customer

Value to Customer

- Accurate prediction of behavior of an electronic component under random vibrational loadings

- Quick turnaround time



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


• The slides with watermark of “ANSYS Confidential” should be removed before showing/sharing this document externally

• The author (or uploader) and the reviewer of this document have, to the best of their knowledge, identified the source of various images, animations, text, plots etc. and classified them based on “Restrictions for Use” type. Kindly review the section on “Reference” at the end of this document.

• All Customer Application Presentations are marked as “For Internal Use only” by default since it might contain

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References: This slide is “internal” only. Please remove this slide before sharing this document externally

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Comments (Provide Link)

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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http://www.sanmina.com/pdf/resources/effectof_lead_mixing_levels.pdf

http://www.sanmina.com/pdf/resources/effectof_lead_mixing_levels.pdf

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Customer Application Presentation ANSYS Solution for … · Customer Application Presentation ANSYS Solution for PCB Reliability ... the best of their knowledge,