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Introdution to POF reliability methods


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Physics of Failure (also known as Reliability Physics) is a science-based approach for achieving Reliability by Design.  The approach is based on research to identify and understand the processes that initiate and propagate mechanisms that ultimately results in failure.  This knowledge when used in Computer Aided Engineering (CAE) durability simulations and reliability assessment can evaluate if a new design, under actual operating is susceptible to the root causes of failure such as fatigue, fracture, wear, and corrosion during the intended service life of the product.
The objective is to identify and eliminate potential failure mechanisms in order to prevent operational failures through stress-strength analysis to produce a robust design and aid in the selection of capable manufacturing practices.  This is accomplished by modeling the material strength and architecture of the components and technologies a product is based upon to evaluating their ability to endure the life-cycle usage and environmental stress conditions the product is expected to encounter over its service life in the field or during durability or reliability qualification tests.
The ability to identify and quantify the specific hazard risks timeline of specifics failure risks in a new product while it is still on the drawing board (or CAD screen) enables a product team to design reliability into a product by revising the design to eliminate or mitigate failure risks.  This capability results in a form of Virtual Validation and Virtual Reliability Growth during the a product’s design phase that can be implemented faster and at lower costs than the traditional Design-Build-Test-Fixed approach to Reliability Growth during a product’s development and test phase. 
This webinar compares classical reliability concepts and relates them to the PoF approach as applied to Electrical/Electronic (E/E) System and technologies.  This webinar is intended for E/E Product Engineers, Validation/Test Engineers, Quality, Reliability and Product Assurance Personnel, CAE Modeling Analysts, R&D Staff and their supervisor.

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Introdution to POF reliability methods

  1. 1. Introduction to  Introduction to Physics of Failure  Physics of Failure y Reliability Methods James McLeish ©2011 ASQ & Presentation James Presented live on Feb 09th, 2012 Calendar/Webinars ‐_English/Webinars_‐_English.html
  2. 2. ASQ Reliability Division  ASQ Reliability Division English Webinar Series English Webinar Series One of the monthly webinars  One of the monthly webinars on topics of interest to  reliability engineers. To view recorded webinar (available to ASQ Reliability  Division members only) visit ) / To sign up for the free and available to anyone live  webinars visit and select English  Webinars to find links to register for upcoming events Calendar/Webinars ‐_English/Webinars_‐_English.html
  3. 3. Webinar Series• Next Sessions English series Thursday, March 8, 2012, Noon - 1:00 pm EDT TOPIC: Field Failure Analysis Using Root Cause
 Pattern Diagrams BY: Bob Lloyd Thursday, Apr 12, 2012, Noon - 1:00 pm EDT TOPIC: The Proper Analysis Approach
 for Life Data BY: Dr. Huairui Guo Chinese series Beijing Time: Feb 15, 2012; 11:00AM – 12:00PM TOPIC: Rapid Reliability Demonstration Tests 
(快速可靠性验证试验) BY:Guangbin Yang (杨广斌)
Reliability and Quality Supervisor 
(可靠性与质量主管)• under webinars and short courses• for full schedule• Recordings at under webinars or short courses
  4. 4. Announcements We are looking volunteers to support the following programs: Webinars Newsletter The Reliability Calendar Websites New Member Welcome And other programs Discussion groups (ASQ forums & Linkedin) We invite you to join our ranks as a member visit www.ASQ.ORG/membership Questions, comments, suggestions, or desire to volunteer or presenter, please contact:
  5. 5. Brought to you in part by…
  6. 6. Today’s SpeakerJames McLeishBio: James McLeish is a senior technical staff consultantand manager of the Michigan office of DfR (Design forReliability) Solutions, a Failure Analysis, LaboratoryServices and Reliability Physics Engineering ConsultingFirm headquartered in College Park Maryland.Mr. McLeish is a senior member of the ASQ Reliability Division and a coremember of the SAE’s Reliability Standard Committee with over 32 years ofautomotive and military E/E experience in design, development, validationtesting, production quality and field reliability. He has held numerous technicalexpert and management position in automotive electronics product design,development, vehicle electrical system integration, product assurance,validation testing and warranty problem solving as an E/E Reliability Managerand E/E Quality/Reliability/Durability (QRD) technical specialists at GeneralMotors.
  7. 7. Introduction to Physics of Failure Reliability MethodsJames McLeish ASQ Reliability Division Webinar Feb. 9,© 2012 DfR2007© 2011 - 2010 2004 & ASQ
  8. 8. Physics of Failure / Reliability Physics Definitionso Physics of Failure - A Formalized and Structured approach to Root Cause Failure Analysis that focuses on total learning and not only fixing a current problem. o To achieve an understanding of “CAUSE & EFFECT” Failure Mechanisms AND the variable factors that makes them “APPEAR” to be Irregular Events. o Combines Material Science, Physics & Chemistry with Statistics, Variation Theory & Probabilistic Mechanics. o A Marriage of Deterministic Science with Probabilistic Variation Theory for achieving comprehensive Product Integrity and Reliability by Design Capabilities. o Failure of a physical device or structure (i.e. hardware) can be attributed to the gradual or rapid degradation of the material(s) in the device in response to the stress or combination of stresses the device is exposed to, such as: o Thermal, Electrical, Chemical, Moisture, Vibration, Shock, Mechanical Loads . . . o Failures May Occur: o Prematurely because device is weaken by a variable fabrication or assemble defect. o Gradually due to a wear out issue. o Erratically based on a chance encounter with an Excessive stress that exceeds the capabilities/strength of a device,© 2012 DfR2007© 2011 - 2010 2004 & ASQ 7
  9. 9. Physics of Failure / Reliability Physics Definitionso Reliability Physics (a.k.a. the PoF Engineering Approach) - A Proactive, Science Based Engineering Philosophy for applying PoF knowledge for the Development and Applied Science of Product Assurance Technology based on: o Knowing how & why things fail is equally important to understand how & why things work. o Knowledge of how thing fail and the root causes of failures enables engineers to identify and avoid unknowingly creating inherent potential failure mechanisms in new product designs and solve problems faster. o Provides scientific basis for evaluating usage life and hazard risks of new materials, structures, and technologies, under actual operating conditions. o Provides Tools for achieving Reliability by Design o Applicable to the entire product life cycle o Design, Development, Validation, Manufacturing, Usage, Service.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 8
  10. 10. The Traditional View of Quality, Reliability & Durability (QRD) - Product Life Cycle Failure Rate “Bath Tub” Curve Focuses on 3 Separate & Individual Life Cycle Phases End of Useful Life each with Separate Control & Improvement Strategies /Typ. Replacement Decision Pt. The Bath Tub CurveProblem or Failure Rate (Sum of 3 Independent Phenomena) But “True” Root Causes Can Be Disguised by Actuarial Assumptions to Make QRD Easy to Administer This is an Inaccurate & Misleading Point of View Durability = Wear Out Quality = Infant Mortality (End of Useful Life) Reliability = Random or Chance Problems (Constant Unavoidable) Time 0 1 Year 2 Years 3 Years 4 Years 5 Years© 2012 DfR2007© 2011 - 2010 2004 & ASQ 9 9
  11. 11. A “PoF FAILURE MECHANISM” Based “REALISTIC” View Reveals the True Interactive Relationships Between Q, R & D - Real failure rate curves are irregular, dynamic and full of valuable information, not clean smooth curves to simplify the data plots. Manuf. Variation & Error Weak Designs ThatProblem or Failure Rate and Service Errors Start to Wear Out That Cause Latent Prematurely Problems Throughout Life “Cause & Effect” Root Causes Can Be Disguised by Actuarial Statistics Once Problems Are Accurately Categorized You Have Realistic Picture of “True Root Causes” TRUE Random Problems Are Rare Once Correlated to “ACTS OF GOD & WAR”Time 0 1 Year 2 Years 3 Years 4 Years 5 Years© 2012 DfR2007© 2011 - 2010 2004 & ASQ 10 10
  12. 12. Traditional Reliability Growth in Product Development Empirical “TRIAL & ERROR” Method to Demonstrate Statistical Confidence 4) Faults No 1) Design 2) Build 3) Test DetectedDESIGN - BUILD - TEST - FIX ? (D-B-T-F) Yes 5) Fix Whatever Breaks. 6) REPEAT 3-5 Until Nothing Else Today, This Is Not Enough! Breaks Or You Run 1) All design issues often not well defined. Out Of 2) Early build methods do not match final processes. Time/Money. 3) Testing doesn’t equal actual customer’s usage. 4) Improving fault detection catches more problems, but causes more rework. 5) Problems found too late for effective corrective action, fixes often used. 6) Testing more parts & more/longer tests “seen as only way” to increase reliability. 7) Can not afford the time or money to test to high reliability. 8) Incremental improvements from faster more, capable tests still not enough. It Is Time for a Change© 2012 DfR2007© 2011 - 2010 2004 & ASQ 11
  13. 13. QRD in Product Development - Reliability Growth Verses the QRD Challengeo Challenges: o Increasing Electrical/Electronic Content & Complexity o Increasing % of System Cost o Increasing Device Complexity 90 o Increasing Power consumption (Heat) o Increasing Functionality & Software Complexity 80 1st MY 70 o Rapid & Constant Technology Growth 2nd MY 3rd MY o Lesson Learned Constantly Changing 60 4th MY o Rapidly Outdated 50 DPTV 5th MY o Lack of Understanding & Confusion 40 6th MY o Design Issues That Effect QRD 30 o Manufacturing Issues Effect QRD 20 o Outdated Paradigms 10 o MIL HDBK 217 for Reliability Assessment 0 and tracking 0 6 12 18 24 30 36 42 48 54 60 o “Test & Fix” Dev./Val. Growth Months After Sale o Lack of Reliability by Design o Annual Reappearance of Problems o Fire Fighting o Hardy Perennials o Uneven Supply Chain Learning Curve© 2012 DfR2007© 2011 - 2010 2004 & ASQ 12
  14. 14. The Traditional Product Development Process (PDP) Approach is A Series of Design - Build - Test - Fix Growth Events Emphasis Emphasis EmphasisSketchy/ Design QRD+P Costly Watch &Loosely then Growth by Redesign Start StudyDefined Build Rounds of /Retool Production WarrantyReq’mts Product Test Dev/Val Fixes Process Part 1: Part 2: Formal Lab & Track Dev/Val Trial Customers Become the Unwitting & Error Approach to Test Subjects in Continued Trial Finding & Fixing Problems. & Error Tests in the Real World Essentially Formalized Trial & Error That Starts With Product Test – To Be Good Enough To Start Production Then Evolves Into Continuous Improvement Activates In Responses to Warranty Claims© 2012 DfR2007© 2011 - 2010 2004 & ASQ 13
  15. 15. Reliability/Capability Growth with Traditional D-B-T-F ProductDevelopment Processes Takes Years to Achieve Maturity 1.00 D Initial Prod. 94% R / 6% Fr. E Dev. Emphasis S on Performance I .90 & Functional w/ G Non-Production N Intend HW .80 C Duane Model A Simplification of P Reliability Growth A .70 B Capability / Reliability I Growth Actually Occurs in L Incremental Steps I .60 Mid Prod. Dev. T Emphasis on Y / .50 Packaging & Final Prod. Dev. R HW Durability Emphasis on E w/Prod. intent Manufacturing Process & Continuous Production L HW & Non- I .40 Prod. Intent Quality A Manuf. w/Prod. Intend B HW & Manuf. I .30 L Design Alpha HW Beta HW Proto Production Production Production Production I Proj. Team (Funct. Dev.) (DV) Pilot Prod. (PV) & Ramp up 1st Yr. 2nd Yr. 3rdt Yr. 4th Yr. T Concept Start B-T-F1 B-T-F2 B-T-F3 B-T-F4 P-W-F1 P-W-F2 P-W-F3 P-W-F4 Y 14© 2011 - 2010© 2012 DfR2007 2004 & ASQ 14
  16. 16. If Parts Past Qualification Testing , Why Do Field failures Still Occur Statistically Confident - Probability of Detection X Sized Issues out of # of Y Parts Not Very Effective for Issues Below 5% of Population D-B-T-F is Probability of Detecting a Problems of Size “X” with “N” Parts on Test Effective For Finding a Few Big-Medium Sized Problems 10% 5% 2% 1% 0.5% 0.2% 0.1% 0.05% But D-B-T-F is Ineffective For Finding Many Small Problems© 2012 DfR2007© 2011 - 2010 2004 & ASQ 15
  17. 17. Is the Solution Better Faster Reliability Growth Tests like HALT: Better Tests Do Find/Fix Field Some Problems Faster, But is this Enough? 1.00D But Best in Class 98-99R @SOPESIG .90N More Capable .97R => 3% Failures Accelerated Tests by 2nd Model YearCA .80 Enables FasterP Reliability Growth BETTER QRDA (Evolutionary ACHIEVED FASTERB Improvement)I .70L Implement Over Traditional ReliabilityIT 6 Years GrowthY .60/REL .50IA 10-15% FASTER PRODUCTB DEVELOPMENTI .40LITY .30 Production Production Production Production Proj. . Alpha HW Beta Proto 1st Yr. 2nd Yr. 3rdt Yr. 4th Yr. Launch Concept (Funct. Dev.) (DV) (PV) Pilot & P-W-F1 P-W-F2 P-W-F3 P-W-F4 Dsgn B-T-F1 B-T-F3 Ramp up Team B-T-F2© 2012 DfR2007© 2011 - 2010 2004 & ASQ B-T-F4 16
  18. 18. Key PoF Terms and Definitionso Failure Mode: o The EFFECT by which a failure is OBSERVED, PERCEIVED or SENSED.o Failure Mechanism : o The PROCESS (elect., mech., phy., chem. ... etc.) that causes failures. o FAILURE MODE & MECHANISM are NOT Interchangeable Terms in PoF.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 17
  19. 19. Key PoF Terms and Definitionso Failure Site : o The location of potential failures, typically the site of a designed in: o stress concentrator , o design weakness or o material variation or defect. o Knowledge Used to Identify and Prioritized Potential Failure Sites and Risks in New Designs During PoF Design Reviews.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 18
  20. 20. 3 Generic PoF Failure Categories and Their Evaluation/Detection Methods GENERIC FAILURE CATEGORY TYP. FAILURE DETECTIONo Errors - Incorrect Operations & Quality Variation Defects/Weaknesses. o Missing parts, incorrect assembly or process. Assurance o Process control errors (Torque, Heat treat). Immediate or o Design errors Latent defects o Missing functions, o Inadequate performance. o Inadequate strength.o Overstress. Performance Overheating. o o Voltage/Current Capability o Electro static discharge. Assessments o Immediate yield, buckling, crack.o Wearout/Changes, via Damage Accumulation. Stress-Life o Friction wear. Durability o Fatigue. o Corrosion. Assessments o Performance changes/parameter drift© 2012 DfR2007© 2011 - 2010 2004 & ASQ 19
  21. 21. Generic Failure Categories Errors and Variation Issues are Everywhere Errors Broadest Category  Variation  Errors in Design, Manufacturing, Usage & Service.  Fine line between excessive variation & out  Missing knowledge right errors.  Human factor Issues.  Both related to various quality issues.  Manufacturing equipment wear out & failure could be related to maintenance errors.  Weak material could be raw material variation or insufficient heat treat processing errors. Interface Equipment  Equipment process capabilities limitation or operator set up error. Design & Process People Performance Usage Material Environment Noise Factors© 2012 DfR2007© 2011 - 2010 2004 & ASQ 20
  22. 22. Generic Failure Categories Overstress - When Loading Stress Exceed Material Strength STRESS/ STRENGTH Variation of Design’s Material Strengths Typical - Related to Process Capabilities Deterministic(Nominal) Analysis DESIGN MARGIN 4 How well  3 2 SAFETY FACTOR  do you |  Understand 9 | UNRELIABILITY = Probability 9 | & Design 9 3 6 that Load Exceed Strength For % 9 % Strengths t t % t Stress Variation of Usage & & Stresses? i i l i Environments Loads & l l e e Their Interactions e FREQUENCY OF OCCURRENCE© 2012 DfR2007© 2011 - 2010 2004 & ASQ 21
  23. 23. Overview of How Things Age & Wear Out - Stress Driven Damage Accumulation in Materials 3. Strain : Instantaneous changes (materialsstructural) due 2. Stress to loading, different loads The distribution/ interact to contribute to a transmission of single type of strain. loading forces Knowledge of how/ which throughout “Key Loads” act & interact the device. is essential for “efficiently” developing good products, 6. Time to Mean Failure: processes & evaluations. (Damage Accumulation verses Yield Strength 1. Loads A Function of: Stress Intensity, Material Elect. Chem. Properties, & Stress Exposure Cycles/Duration].Thermal, Mech... 4. Damage 7. Project the Distribution About the Mean Accumulation Individual orcombined, from i.e. Rate of Failure (Fall out) (or Stress Aging): A function of variation in; Usage, Device Strength Permanent change environment & & Process Quality Control (i.e. latent defects). degradation retained usage act on materials & 5. Failure Site & Type: after loads are removed. structure. Typically due to a designed in: stress concentrator , From small incremental design weakness, material/process variation or defect. damage, accumulated during periods/cycles of stress exposure.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 22
  24. 24. Generic Failure Categories - Wearout (Damage Accumulation) - Over Time of Stress Exposure STRESS INDUCED STRESS/ DAMAGE STRENGTH ACCUMULATION Design’s Strength Decay/Spreads Over Time / Usage Material Decay Increases UNRELIABILITY OVER TIME 4 How well 3 STRESS   2 EXPOSURE TIME do you | |  or USAGE CYC’S Understand 9 9 | & Design 9 3 6 INITIAL For % 9 UNRELIABILITY Strengths % t t % & Stresses? i i t l i l l e e e FREQUENCY OF OCCURRENCE© 2012 DfR2007© 2011 - 2010 2004 & ASQ 23
  25. 25. Generic Failure Categories Examples of Wear Out Failure Mechanismo Mechanical  Chemical / Contaminate o Fatigue  Moisture Penetration o Creep  Electro-Chemical-Migration Driven o Wear Dendritic Growth.o Electrical  Conductive Filament Format (CFF) o Electro-Migration Driven  Corrosion Molecular Diffusion & Inter Diffusion  Radiation Damage o Thermal Degradationo When Over Stress Issue are Detected. o Verify supplier’s are meeting material strength specs & purity expectation. o Re-evaluate field loading / stress expectation used to design the part. o Sort out stresses, o Combined stress issues are often involved. o Re-evaluate effectiveness of product durability testing© 2012 DfR2007© 2011 - 2010 2004 & ASQ 24
  26. 26. Two Types of Circuit Board Related Vibration Durability Issueso Board in Resonance o Components In Resonance. o Components. Shaken Off/Fatigued o Components Shake/Fatigue themselves apart or by Board Motion. off the Board. o By Flexing Attachment Features o Especially Large, Tall Cantilever Devices 3 Med. Sized Alum CAPS Lead Motion 1 Small Long Leaded Snsr Bending Lead Wires - Flexed Down 1 Hall Effect Sensor. Stressed - Normal Solder 1 Large Coil Assembly Gull Wing I.C. - Flexed up Joint Displacement PC Board Time to Failure Determine by Intensity/Frequency of Stress Verses Solder Fatigue Life Strength of Material Log (Peak Strain)Steinberg’s Criterion: For a 10 million cycle life, Z < 0.0008995·B/(C·h·r (L1/2)). Ref: Vibration Analysis for Electronic Equipment, by David S. Steinberg Log (Number of Cycles to Failure)© 2012 DfR2007© 2011 - 2010 2004 & ASQ 25
  27. 27. PCB Vibration - 1st, 2nd & 3rd Harmonic Modals 1st Harmonic 2nd Harmonic 3rd Harmonic© 2012 DfR2007© 2011 - 2010 2004 & ASQ 26
  28. 28. PoF Example – E/E Module Vibration AnalysisConnector Provides Primary PCB Support CAE Modal Simulation of Circuit Board Flexure Original CAE Guided Redesign Transformer A Large Mass, Adds Back Edge Supportwill drive a Large Board Displacement (mils) 13.95 1.15Vibration Modal Natural Frequency (Hz) 89 489 Response Vib. Durability Calculation 25 Days > 50 Years© 2012 DfR2007© 2011 - 2010 2004 & ASQ 27
  29. 29. Module Vibration Durability Simulation Results - For Alternative Board Support & Transformer Locations DAYS TO FAILURE ORIGINAL TRANSFORMER LOCATION TRANSFORMER RELOCATED @ 2 Hrs Vib / Day || R101 + R1021000M || R825 + R824100 M10 M1M100,000 3650 Days10,000 (10 Years)1000100101 Edge1 Edge1 & Edge1 & Edge1, Edge1 & All Edges Edge1 Edge1 & Edge1 & Edge1, Edge1 & All Edges (Connector) Corners Middle Corners Edge2 (Connector) Corners Middle Corners Edge2 & Middle, & Middle, || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + || + © 2012 DfR2007 © 2011 - 2010 2004 & ASQ 28
  30. 30. Generic Failure Categories - Shocko Animated Simulation Visualizes Transition of the Shock Wave Through the Structure of the Module.o Peak Stresses, Material Strain, Motions & Displacements Can be Identified.o Potential Failure Sites Where Local Stresses Exceed Material Strength Can Be Identified & Prioritized.o Zoom In On Surface Such as Potential for Snap Lock Fastener Releaseo Wire Frame View Allows Xray Vision of Internal Features. © 2012 DfR2007 © 2011 - 2010 2004 & ASQ 29
  31. 31. Solder Thermo-Mechanical Shearing Fatigue Driven by:Coefficient of Thermal Expansion/Contraction (CTE) Mismatch During Thermal Cyclingo As a circuit board and its components expand and contract at different rates the differential strain between them is absorbed by the attachment system leads and solder joints which drives metal fatigue. Coef. Of Thermal Exp. (PPM/°C) • Chip Resistor Body: 4-5 ppm/°C • PCB - FR4 x-y axis: 14-17 ppm/°C FR4 z axis: 120-160 ppm/°C© 2012 DfR2007© 2011 - 2010 2004 & ASQ 30
  32. 32. Correlation Between: Stress Driven Damage Accumulation in Materials and Life Consumption Rateso Material N-S Curve (Number of Life Cycle at a Stress Level) (Transposed S-N) . High Useful Acceleration Range (log) Number of Foolish Failure Region Cycles INVALID TEST REGION Low Stress ~ Near “Infinite” Low Life Region Low Stress (log) Higho Stress - Strain Yield Curve. Plastic Region Excessive Plastic High Deformation STRESS (psi) Instantaneous or Near Instantaneous Low Ultimate Strength or Elastic Region Fracture Point Low STRAIN in/in High o Lowering the Stress in Material & Members Increases Life &Reliability© 2012 DfR2007© 2011 - 2010 2004 & ASQ 31
  33. 33. Solder Fatigue Life is Directly Related to Component Packaging & Solder Attachment Scheme Generally the IC Package Influences QRD more than the IC itself. Single Sided Then Thru-hole 1st Generation Quad Surface Mount 2nd Generation Quad Surface Mount DIP Integrated Circuits J Lead PLCC, 1982 - Today Fine Pitch Gull Wing I.C, 1993 - Today 1970 ‘s- Today ~6 Up to 160 I/O, 1.5 in sq., ~54 Up to 450 I/O, 1.75 in sq ~4 up to 68 I/O, 1” x 3.5” Up to 100 Meg Hz Speeds Up to 250 Meg Hz Speeds Up to 10 Meg Hz Speeds. Source of Many Reliability Problems. >10 Time the Life of J Lead in Auto ECMs. Bump & Ball Grid Arrays No Lead Chip Scale Packaging (NLCSP) Leadless Attachments (LCCC, QFN, DFN, SON, LGA) 1996 - Today 2002 - Today ~24 - 1000 I/O 1.2 in. sq ~8 - 480 I/O, .75 in SQ 500+ 1000 Meg Hz Speeds. Gigi Hz Speeds Life Varies Greatly w/Size & Conf. Can have significantly reduces life© 2012 DfR2007© 2011 - 2010 2004 & ASQ 32
  34. 34. Comparison of Through Hole Component Attachment Schemes - Impact of Structural Configuration & Size on Fatigue Durability Package I.C. Die & Die Attachment Wire Bond Lead Frame Lead @ Cold Lead @ Cold Single Sided Solder Joint Lead @ Hot Double Sided (PTH) Joints Allow Leads to Wiggle are 35- 55 TIMES Stronger Under Vib., Shock & Lead is constrained Thermal Exp/Contraction So the Rate of Fatigue the Joint Fatigues Faster DIP - Thru-hole Stress Aging is Much Slower Automotive Fatigue Life Automotive Fatigue Life Single Sided 2-5 Yrs Single Sided >10 Yrso Since Electrical Engineers Design Most Circuit Boards, o The motivation to accepted the added costs of Plated Through Hole (PTHs) was when increasing component required placing component and traces on both sides of the circuits board. o THE RELIABILITY OF EE MODULES SKY ROCKETED with the use of more complex Double Sides PCB. o Thus More Complexity DOES NOT ALWAYS HAVE TO RESULT IN LESS RELIABILITY. A More Capable or Smarter Design Approach Can Overcome the Inherent QRD Risks of Increased Complexity © 2012 DfR2007 © 2011 - 2010 2004 & ASQ 33
  35. 35. Comparison of Leaded Surface Mount Attachment Schemes - Impact of Structural Configuration & Size on Fatigue Durability S. M. Pad & Solder Joint Surface Mount Devices with Gull Wing Fine Pitch Leads J lead - Surface Mount Devices Are Designed as an Articulated Spring, - Thermal Exp/Contraction Their Leads Flex at Two Bend PointsCause Rapid Fatigue Due To Lead Rocking Instead of Transmitting Stress to the Weaker Solder Similar Sized GWFP Devices Avg. 10x the Durability Life of J Leaded Parts in the Same Thermal Cycling Tests. The Cost – GLFP Devices Take Up More Board Areas So Larger Boards May Be Require to Hold the Same Number of Components© 2012 DfR2007© 2011 - 2010 2004 & ASQ 34
  36. 36. PoF Thermal Cycling Solder Fatigue Model (Modified Engelmaier – Leadless Device)o Modified Engelmaier LD o Semi-empirical analytical approach Dg  C DaDT o Energy based fatigue hso Determine the strain range (Dg)o Where: C is a function of activation energy, temperature and dwell time, LD is diagonal distance, a is CTE, DT of temperature cycle & h is solder joint height Determine the shear  LD LD hc  2    a 2  a1  DT  LD  F        hso   force applied at the  9G a   solder joint  E1 A1 E2 A2 AsGs AcGc  b   o Where: F is shear force, LD is length, E is elastic modulus, A is the area, h is thickness, G is shear modulus, and a is edge length of bond pad. o Subscripts: 1 is component, 2 is board, s is solder joint, c is bond pad, and b is board o Takes into consideration foundation stiffness and both shear and axial loads (Models of Leaded Components factor in lead stiffness / compliancy) Determine the strain energy Fo DW  0.5  Dg  dissipated in the solder joint As Calculate N50 cycles-to-failure using: N f  0.0019  DW o 1 o An Energy Based model for SnPb N f  0.0006061  DW  1 o The Syed-Amkor model for SAC© 2012 DfR2007© 2011 - 2010 2004 & ASQ 35
  37. 37. Originally Stress Analysis and PoF Modeling was a Time Consuming ProcessRequiring an Expert to Create a Custom Finite Element Analysis of Individual Issues© 2012 DfR2007© 2011 - 2010 2004 & ASQ 36
  38. 38. PoF CAE Thermal Cycling Simulation - Reveals Issues That Could Never Be Seen or Measured in a Physical Test BGA IC CTE = 10 PPM/°C Sheering Simulated Strain in Thermal Solder Balls Cycle of 0 to +100°C Circuit Board CTE = 15 PPM/°C View of the outer edge balls with motion originating from the neutral center of the Quad BGA IC.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 37
  39. 39. PoF Durability/Reliability Risk Assessments PCB Plated Through Hole (PTH) Via Fatigue Analysis o When a PCB experiences thermal cycling the expansion/ contraction in the z-direction is much higher than that in the x-y plane. o The glass fibers constrain the board in the x-y plane but not through the thickness. o As a result, a great deal of stress can be built up in the copper via barrels resulting in eventual cracking near the center of the barrel as shown in the cross section photos.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 38
  40. 40. Plated Through Hole Via Barrel Cracking Fatigue Life Based On IPC TR-579 o Determine applied stress applied (σ) o Determine strain range (∆ε) o Apply calibration constants o Strain distribution factor, Kd(2.5 –5.0) o PTH & Cu quality factor KQ(0 –10) o Iteratively calculate cycles-to-failure (Nf50)© 2012 DfR2007© 2011 - 2010 2004 & ASQ 39
  41. 41. Through PoF Research Durability/Reliability Simulations for Virtual Reliability Growth of Electronics are Now Possible Start Build & Program Model(s) Integrated with PoF/PoS Validate into Standalone Simple for Into a Mechanism PoF / PoS Complex FEA Sophisticated Knowledge Math Models Math Data Tools CAE Tool. Add in Statistical Account for Operational Tools for Variation Loading Drift© 2012 DfR2007© 2011 - 2010 2004 & ASQ 40
  42. 42. PoF Knowledge Enables A New Product Development Process Math to Hardware MATH TO HARDWAREA) Durability / Reliability Simulations – “A” Analysis o Evaluate Durability Capability and o Identify Specific Reliability Risks o While Still on the CAD ScreenB) First Article Evaluation via Direct Quality Assessments – “D” Development o Verify PCB Fabrication and Assembly Quality Meets Design Requirement o Before Starting Stress Life TestingC) Refocused Physical Durability Testing – “V” Validation w/Simulation Aided Accelerated Testing o Refocused from a Discover Process to a Final Conformation Procedure© 2012 DfR2007© 2011 - 2010 2004 & ASQ 41
  43. 43. The Auto Industry Has Reaped Significant PDP & QRD Benefits Through Math Based, Virtual, Computer Aided Engineering Tools Safety Vehicle Structure EnergyA Result ofInitiatives to:MigrateEvaluations Performance Integrationfrom Road Thermal Vehicle Dynamicsto Labto Computer,at theVehicle, Aerodynamics Noise & VibrationSubsystem &Component DurabilityLevel© 2012 DfR2007© 2011 - 2010 2004 & ASQ 42
  44. 44. A CAE Software Programs are now Commercially Available toAutomate CAE PoF Model Creation and Analysis1) Design Capture – Utilize standard CAD/CAM Circuit Board design files to create a virtual model2) Life-Cycle Characterization - define the reliability/durability objectives and expected environmental & usage conditions (Field or Test) under which the device is required to operate3) Load Transformation – automated FEA creation and calculations that translates and distributes the environmental and operational loads into the stresses across a circuit board to each individual parts4) PoF Durability Simulation/Reliability Analysis & Risk Assessment – Performs a design and application specific durability simulation to calculates detail life expectations, reliability distributions over a life tine line & prioritizes risks by applying PoF algorithms.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 43
  45. 45. 1) Semi Automated Design Capture From CAD/CAM files to create a CAE Virtual Model of a Product Design.o Creates CAE virtual model from standard circuit board CAD/CAM design files (Gerber or ODB Format)© 2012 DfR2007© 2011 - 2010 2004 & ASQ 44
  46. 46. 2) Define Test or Field Environment and Usage Profileso Define simple or complex environmental or test stress profiles© 2012 DfR2007© 2011 - 2010 2004 & ASQ 45
  47. 47. 3) Load Transformation in to Stresses - Automated FEA Mesh Creation andCalculation of Stress/Strain Distribution Across the Device and at Each Component o Days of FEA modeling and calculations, executed in minutes o Without a FEA modeling expert. Finite Element Mesh 1st Natural Frequency 3rd Natural Frequency 2nd Natural Frequency© 2012 DfR2007© 2011 - 2010 2004 & ASQ 46
  48. 48. 4) Stress/Strain Results Become Inputs to PoF Durability/ Reliability Damage Models ToCalculate and Tally Durability Life Curve for Each Component & Each Failure Mechanism Parts With Low Fatigue Endurance Found In Initial Design ~84% Failure Projection Within Service Life, Starting at ~3.8 years.o N50 fatigue life calculated for each of 705 components (68 part types), of a Safety Critical Avionics Module with risk color coding, prioritized risk listing and life distribution plots based on known part type failure distributions (analysis performed in <30 secs after model created). o Red - Significant portion of failure distribution within service life or test duration. o Yellow - lesser portion of failure distribution within service life or test duration. o Green - Failure distribution well beyond service life or test duration.(Note: N50 (i.e. Mean) life - # of thermal cycles where fatigue of 50% of the parts are expected to fail)© 2012 DfR2007© 2011 - 2010 2004 & ASQ 47
  49. 49. 5) PoF Durability Simulations/Reliability Risk Assessment Enables Virtual Reliability Growtho Identification of specific reliability/durability limits or deficiencies, of specific parts in, specific applications, enables the module design to be revised with more suitable/more robust parts capable of meeting reliability/durability objectives.o Reliability plot of the same project after fatigue susceptible parts replaced with electrically equivalent parts in component packages suitable for the application.o Life time failure risks reduced from ~84% to ~1.5%© 2012 DfR2007© 2011 - 2010 2004 & ASQ 48
  50. 50. 5) PoF Durability Simulations/Reliability Risk Life Curves for Each FailureMechanism Tallied to Produce a Combined Life Curve for the Entire Module. Over All Module Combined Failure Rate Thermal Vibration Cycling Fatigue Solder Wear Out Fatigue Wear Out PTH Thermal Cycling Fatigue Wear Out Constant Failure Rate Generic Actuarial MTBF Databaseo Detailed Design and Application Specific PoF Life Curves are Far More Useful that a simple single point MTBF (Mean Time Between Failure) estimate.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 49
  51. 51. The Efficiency Improvements of a PoF Knowledge & Analysis Based ProductDevelopment ProcessD .99R => 1% FailuresE 1.00 Simulation Based PDPS Enables DramaticI “Revolutionary” ImprovementG in Growth RateN .90 BETTER QRDC ACHIEVED FASTERAP .80A Traditional ReliabilityB GrowthIL .70I More Capable Accelerated TestsT Enables Faster Reliability GrowthY (Evolutionary Improvement)/ .60RELI .50A FASTER PRODUCTB DEVELOPMENTIL = LOWER COSTS .40ITY .30 Alpha HW Production Production Production Production Proj. . Proto Launch (Funct. Dev.) 1st Yr. 2nd Yr. 3rdt Yr. 4th Yr. Concept (PV) Dsgn B-T-F1 Beta B-T-F3 Pilot & P-W-F1 P-W-F2 P-W-F3 P-W-F4 Team (DV) Ramp© 2012 DfR2007© 2011 - 2010 2004 & ASQ Start B-T-F2 up 50 50
  52. 52. Summary - Physics of Failure/Reliability Physics is Reliability Science for the Next Generationo PoF Science based Virtual Validation Durability Simulation/ Reliability Assessments Tools Enable Virtual Reliability Growth that is: o Faster and Cheaper than Traditional Physical Design, Build, Test and Fix Testing.o Determines if a Specific Design is Theoretically Capable of Enduring Intended Environmental and Usage Conditions. o “Stress Analysis” Followed by “Material Degradation/Damage Modeling”o Compatible with the way modern products are designed and engineered (i.e CAD/CAE/CAM).o Semi Automated PoF CAE Tools Enables Rapid, Low Cost Analysis Without a Highly Trained CAE/PoF expert.o Produces Significant Improvement In Accelerated Fielding of High QRD Products© 2012 DfR2007© 2011 - 2010 2004 & ASQ 51
  53. 53. Want to Know More – Suggested Reading© 2012 DfR2007© 2011 - 2010 2004 & ASQ 52
  54. 54. Questions & Discussion© 2012 DfR2007© 2011 - 2010 2004 & ASQ 53
  55. 55. Follow Upo To Learn More about Physics of Failure Durability Simulation / Reliability Assessment Tools,o To Request a PDF Copy of the Presentation Slides o Contact: , or 301-474-0607 o Thank You for Attending.© 2012 DfR2007© 2011 - 2010 2004 & ASQ 54