Next Generation HALT and HASS Robust Design of Electronics and Systems Quality and Reliability Engineering Series

A NEW APPROACH TO DISCOVERING AND CORRECTING SYSTEMS RELIABILITY RISKS

Next Generation HALT and HASS presents a major paradigm shift from reliability prediction-based methods to discovery of electronic systems reliability risks. This is achieved by integrating highly accelerated life test (HALT) and highly accelerated stress screen (HASS) into a physics of failure based robust product and process development methodology. The new methodologies challenge misleading and sometimes costly misapplication of probabilistic failure prediction methods (FPM) and provide a new deterministic map for reliability development. The authors clearly explain the new approach with a logical progression of problem statement and solutions.

The book helps engineers employ HALT and HASS by demonstrating why the misleading assumptions used for FPM are invalid. Next, the application of HALT and HASS empirical discovery methods to quickly find unreliable elements in electronics systems gives readers practical insight into the techniques.

The physics of HALT and HASS methodologies are highlighted, illustrating how they uncover and isolate software failures due to hardware?software interactions in digital systems. The use of empirical operational stress limits for the development of future tools and reliability discriminators is described.

Key features:

• Provides a clear basis for moving from statistical reliability prediction models to practical methods of insuring and improving reliability.
• Challenges existing failure prediction methodologies by highlighting their limitations using real field data.
• Explains a practical approach to why and how HALT and HASS are applied to electronics and electromechanical systems.
• Presents opportunities to develop reliability test discriminators for prognostics using empirical stress limits.
• Guides engineers and managers on the benefits of the deterministic and more efficient methods of HALT and HASS.
• Integrates the empirical limit discovery methods of HALT and HASS into a physics of failure based robust product and process development process.

Series Editor’s Foreword xi

Preface xiv

List of Acronyms xvi

Introduction 1

1 Basis and Limitations of Typical Current Reliability Methods and Metrics 5

1.1 The Life Cycle Bathtub Curve 7

1.1.1 Real Electronics Life Cycle Curves 9

1.2 HALT and HASS Approach 11

1.3 The Future of Electronics: Higher Density and Speed and Lower Power 13

1.3.1 There is a Drain in the Bathtub Curve 14

1.4 Use of MTBF as a Reliability Metric 16

1.5 MTBF: What is it Good For? 17

1.5.1 Introduction 17

1.5.2 Examples 18

1.5.3 Conclusion 24

1.5.4 Alternatives to MTBF for Specifying Reliability 25

1.6 Reliability of Systems is Complex 26

1.7 Reliability Testing 28

1.8 Traditional Reliability Development 33

Bibliography 34

2 The Need for Reliability Assurance Reference Metrics to Change 36

2.1 Wear‐Out and Technology Obsolescence of Electronics 36

2.2 Semiconductor Life Limiting Mechanisms 37

2.2.1 Overly Optimistic and Misleading Estimates 42

2.3 Lack of Root Cause Field Unreliability Data 43

2.4 Predicting Reliability 48

2.5 Reliability Predictions – Continued Reliance on a Misleading Approach 50

2.5.1 Introduction 51

2.5.2 Prediction History 52

2.5.3 Technical Limitations 53

2.5.4 Keeping Handbooks Up‐to‐Date 54

2.5.5 Technical Studies – Past and Present 59

2.5.6 Reliability Assessment 62

2.5.7 Efforts to Improve Tools and Their Limitations 63

2.6 Stress–Strength Diagram and Electronics Capability 63

2.7 Testing to Discover Reliability Risks 68

2.8 Stress–Strength Normal Assumption 69

2.8.1 Notation 70

2.8.2 Three Cases 71

2.8.3 Two Normal Distributions 73

2.8.4 Probability of Failure Calculation 73

2.9 A Major Challenge – Distributions Data 73

2.10 HALT Maximizes the Design’s Mean Strength 75

2.11 What Does the Term HALT Actually Mean? 78

Bibliography 83

3 Challenges to Advancing Electronics Reliability Engineering 86

3.1 Disclosure of Real Failure Data is Rare 86

3.2 Electronics Materials and Manufacturing Evolution 89

Bibliography 91

4 A New Deterministic Reliability Development Paradigm 92

4.1 Introduction 92

4.2 Understanding Customer Needs and Expectations 95

4.3 Anticipating Risks and Potential Failure Modes 98

4.4 Robust Design for Reliability 104

4.5 Diagnostic and Prognostic Considerations and Features 110

4.6 Knowledge Capture for Reuse 110

4.7 Accelerated Test to Failure to Find Empirical Design Limits 112

4.8 Design Confirmation Testing: Quantitative Accelerated Life Test 113

4.9 Limitations of Success Based Compliance Test 114

4.10 Production Validation Testing 115

4.11 Failure Analysis and Design Review Based on Test Results 116

Bibliography 120

5 Common Understanding of HALT Approach is Critical for Success 122

5.1 HALT – Now a Very Common Term 123

5.2 HALT – Change from Failure Prediction to Failure Discovery 124

5.2.1 Education on the HALT Paradigm 125

5.3 Serial Education of HALT May Increase Fear, Uncertainty and Doubt 130

5.3.1 While You Were Busy in the Lab 132

5.3.2 Product Launch Time – Too Late, But Now You May Get the Field Failure Data 132

6 The Fundamentals of HALT 134

6.1 Discovering System Stress Limits 134

6.2 HALT is a Simple Concept – Adaptation is the Challenge 135

6.3 Cost of Reliable vs Unreliable Design 136

6.4 HALT Stress Limits and Estimates of Failure Rates 137

6.4.1 What Level of Assembly Should HALT be

Applied? 137

6.4.2 HALT of Supplier Subsystems 138

6.5 Defining Operational Limit and Destruct Limits 138

6.6 Efficient Cooling and Heating in HALT 139

6.6.1 Stress Monitoring Instrumentation 139

6.6.2 Single and Combined Stresses 140

6.7 Applying HALT 142

6.7.1 Order of HALT Stress Application 143

6.8 Thermal HALT Process 144

6.8.1 Disabling Thermal Overstress Protection Circuits 145

6.8.2 HALT Limit Comparisons 146

6.8.3 Cold Thermal HALT 148

6.8.4 Hot Thermal HALT 150

6.8.5 Post Thermal HALT 151

6.9 Random Vibration HALT 152

6.10 Product Configurations for HALT 155

6.10.1 Other Configuration Considerations for HALT 156

6.11 Lessons Learned from HALT 157

6.12 Failure Analysis after HALT 159

7 Highly Accelerated Stress Screening (HASS) and Audits (HASA) 161

7.1 The Use of Stress Screening on Electronics 161

7.2 ‘Infant Mortality’ Failures are Reliability Issues 163

7.2.1 HASS is a Production Insurance Process 164

7.3 Developing a HASS 167

7.3.1 Precipitation and Detection Screens 168

7.3.2 Stresses Applied in HASS 172

7.3.3 Verification of HASS Safety for Defect Free Products 173

7.3.4 Applying the SOS to Validate the HASS Process 174

7.3.5 HASS and Field Life 177

7.4 Unique Pneumatic Multi‐axis RS Vibration Characteristics 177

7.5 HALT and HASS Case History 179

7.5.1 Background 179

7.5.2 HALT 180

7.5.3 HASS (HASA) 181

7.5.4 Cost avoidance 183

Bibliography 184

7.6 Benefits of HALT and HASS with Prognostics and Health Management (PHM) 184

7.6.1 Stress Testing for Diagnosis and Prognosis 185

7.6.2 HALT, HASS and Relevance to PHM 186

Bibliography 189

8 HALT Benefits for Software/Firmware Performance and Reliability 190

8.1 Software – Hardware Interactions and Operational Reliability 190

8.1.1 Digital Signal Quality and Reliability 193

8.1.2 Temperature and Signal Propagation 194

8.1.3 Temperature Operational Limits and Destruct Limits in Digital Systems 197

8.2 Stimulation of Systematic Parametric Variations 198

8.2.1 Parametric Failures of ICs 199

8.2.2 Stimulation of Systematic Parametric Variations 201

Bibliography 205

9 Design Confirmation Test: Quantitative Accelerated Life Test (ALT) 207

9.1 Introduction to Accelerated Life Test 207

9.2 Accelerated Degradation Testing 211

9.3 Accelerated Life Test Planning 212

9.4 Pitfalls of Accelerated Life Testing 215

9.5 Analysis Considerations 216

Bibliography 217

10 Failure Analysis and Corrective Action 218

10.1 Failure Analysis and Knowledge Capture 218

10.2 Review of Test Results and Failure Analysis 220

10.3 Capture Test and Failure Analysis Results for Access on Follow‐on Projects 221

10.4 Analyzing Production and Field Return Failures 222

Bibliography 222

11 Additional Applications of HALT Methods 223

11.1 Future of Reliability Engineering and HALT Methodology 223

11.2 Winning the Hearts and Minds of the HALT Skeptics 225

11.2.1 Analysis of Field Failures 225

11.3 Test of No Fault Found Units 226

11.4 HALT for Reliable Supplier Selection 226

11.5 Comparisons of Stress Limits for Reliability Assessments 228

11.6 Multiple Stress Limit Boundary Maps 230

11.7 Robustness Indicator Figures 235

11.8 Focusing on Deterministic Weakness Discovery Will Lead to New Tools 235

11.9 Application of Limit Tests, AST and HALT Methodology to Products Other Than Electronics 236

Bibliography 238

Appendix: HALT and Reliability Case Histories 239

A.1 HALT Program at Space Systems Loral 240

A.2 Software Fault Isolation Using HALT and HASS 243

A.3 Watlow HALT and HASS Application 253

A.4 HALT and HASS Application in Electric Motor Control Electronics 256

A.5 A HALT to HASS Case Study – Power Conversion Systems 261

Index 268

Kirk A. Gray,Accelerated Reliability Solutions, LLC, Colorado, USA

John J. Paschkewitz,Product Assurance Engineering, LLC, Missouri, USA