improve pcb and package reliability with ansys · pdf filepcb and package warpage challenges...

1 © 2015 ANSYS, Inc. October 14, 2016 ANSYS Confidential

Improve PCB and Package reliability with ANSYS

Rajiv Lochan Rath

Korea 2016 UGM


Overview• PCB and Packages are used in almost all electronic products across industries.

Aerospace and Defense Consumer ElectronicsAutomotive

Healthcare Oil and Gas

Controller System Audio System Engine Control Module LCD display module

Drill hole tool

© Baker Hughes

Attendant Controller Panel Engine control module ….


Major Causes of Electronics Failures

Temperature55%

Vibration20%

Humidity19%

Dust6%

Material Properties- Coefficient of Thermal Expansion (CTE)- Coefficient of Moisture Expansion (CME)

Operation Environment- Cyclic Temperature- High Temperature Gradient(Thermal Shock)Operation Environment

- Cyclic Vibration- Shock

Design- Nonuniformity- Thickness (△T)- Thermal Via

Manufacturing Process(Assemblies)- Layering ; Lamination(Delamination)- Bonding- SJR

Material Properties- Conductivity- Moisture Permeability

Manufacturing Process- Void/Groove


• New Design

• Process Design

• Optimization

• Troubleshooting

• Validation

• Reliability

Role of ANSYS in PCB and Package Design

Thermo-Mechanical Stress

Popcorn & DelaminationViscoelastic

Package Warpage

Moisture Diffusion

& Vapor PressureHygro-mechanical

Stress

Solder Joint

Fatigue ModelingMechanical Stress

Mass & Heat Transfer

Fracture Mechanics Drop/Impact


Reliability

DC-IR + ThermalReliability

Thermo-Mechanical Reliability

Hygro-MechanicalReliability

Mechanical Reliability

Large deformation when PCB subjected to random vibration

Cracks formation at interface between solder ball and PCB due to thermal cyclic loading, CTE mismatch

Hot spot on PCB due to trace heating

(© Alcatel Lucent, Intel, Sanmina) (© expertfea.com)

UBM failure induced by Hygroswellling stress due to CME mismatch, moisture sensitivity


• DC-IR + Thermal Reliability

• Thermo-Mechanical Reliability

• Hygro-Mechanical Reliability

• Mechanical Reliability


Background : Joule Heating [𝑄 = 𝐼2𝑅]

• Joule heating effects on copper traces Temperatures increase Reliability issues PCB delamination and failure

• 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


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.

• 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 ComparisonWithout Trace heating

With Trace heating

1st Iteration 2nd Iteration 3rd Iteration

Simulation TypeMaximum

Temperature

Without Joule Heating 40.0 C

SIwave-Icepak Coupling (First Iteration)

69.0 C

SIwave-Icepak Coupling (Last/Third Iteration)

76.6 C


Case Study: Power Supply Board

• Difference between Icepak / SIwave + Icepak coupling

• Difference between Icepak + Mechanical / SIwave + Icepak + Mechanical coupling

Icepak

(no Trace heating)SIwave + Icepak

Icepak + Mechanical

Shift of max stress

quantity and location

Hotspot off by

10.3 C vs

experiments

Hotspot off by

2.3 C vs

experiments

Siwave + Icepak + Mechanical

Courtesy: Toshiba Corporation, ANSYS Advantage


• Thermal Reliability




(© Alcatel Lucent, Intel, Sanmina)


ANSYS Solution

PCB and Package Warpage

ChallengesPredict local warpage accurately during reflow

Understanding effect of belt speed, geometry of package

Accurately calculating the local material properties

Trace in Mechanical

R17 feature in Mechanical and SpaceClaim for Copper and FR4

distribution

Reflow Profile applied for Warpage

Warpage calculation in Mechanical


Comparison of Warpage with and w/o Trace in PCB


Flip-chip package Warpage

• Why important is to consider the warpage- critical to the subsequent package process after post mold cure process (reflow failure, solder-joint reliability failure)

• Standard : JESD22-B112A from JEDEC

ANSYS FEM vs ExperimentBlock Warpage from STMicroelectronics

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

Solder Joint Life Cycle Estimation

ChallengesPredict time to failure

Understanding simulation procedure for life cycle estimation

Prediction using Darveauxmethod

Life cycle estimation

ACT Extension to Automate Simulation Process


Darveaux Method – Cycles to FailureFatigue Post-processing

Results Table

Equivalent Plastic Strain

Quarter Symmetric Package Model

No of cycles to failure


Moisture-induced Failure

• Requires the Following

1. Absorption under Moisture Sensitivity Level

2. Desorption during bake out or Reflow

3. Heat transfer during Reflow

– May not be needed since reflow profile temperature is known

4. Moisture Swelling

5. Thermal Warpage during Reflow

6. Combination of 4. & 5. Above

7. Vapor pressure in the volume

8. Vapor Pressure & Interface delamination prediction


• The moisture-induced failure- Popcorn- Delamination- common phenomena during solder reflow- due to sudden vaporization of moisture absorbed by package at high temperature condition (local moisture concentration at the critical interface)

• Standard: J-STD-020C Moisture/Reflow Sensitivity TestingJESD22-A113 Reflow Preconditioning

Moisture-induced Failure

Temperature distribution during reflow

Transient vapor pressure/moisture distribution during moisture preconditioning & reflow

Integrated Strain Result

UBM Failure Induced by Hygroswellling Stress


Von Mises Stress Distribution of Solder BallAfter board level drop test

Mechanical Reliability

• Drop test simulation- critical to portable telecommunication devices such as mobile phone, PDA,

home appliances- Explicit ANSYS Solver(Autodyn, LSDyna)

• Shock test simulation- critical to vehicle application devices(JESD22-B104)- critical to defence system application devices(MIL-STD-883)- critical to aerospace application devices(MIL-STD-883)- Implicit/Explicit ANSYS Solver

• Vibration test simulation- critical to vehicle application devices(JESD22-B103)- critical to defence system application devices(MIL-STD-883)- critical to aerospace application devices(MIL-STD-883)- ANSYS Mechanical/APDL

• Fatigue Test Simulation- critical to improve the reliability of the product in market(QA unit/Self Std)- ANSYS Mechanical Fatigue & nCODE for EN/SN Fatigue Simulation

Cycles to Failure


ANSYS Solution

Vibration Reliability

ChallengesPredict the response under Random Vibration Loadings

Predicting fatigue life due to Random Vibration Loadings

PSD

Time History

Frequencies& Mode Shapes

Response PSD

Sigma Values


SummaryValue to Customer

- Ease of coupling multiple physics - Accurate prediction of Temperature- Accurate prediction of local material properties- Accurate Deformation, Stress and Life prediction- Accurate prediction of behavior of an electronic component under vibration- Quick turnaround time- Reduced time to market

Customer using ANSYS Solution


Reliability Analysis of Smart Phone

https://youtu.be/8OsJSnutuVk


ANSYS Consulting Services Your partner in Reliability Simulations

• We bring:• The largest team of CAE experts

• The broadest portfolio of simulation software

• Unmatched industry experience

• With the goal of:• Understanding your process

• Smartly integrating simulation

• Measuring impact on your business

• To give you:• Improved workflow

• Customized tools

• Measurable ROI


THANK YOU

improve pcb and package reliability with ansys · pdf filepcb and package warpage challenges...

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