Lead-free soldering process development and reliability /
Jasbir Bath.
- 1 online resource.
- Wiley series in quality & reliability engineering .
- Wiley series in quality & reliability engineering .
Includes bibliographical references and index.
List of Contributors xix
Introduction xxi
1 Lead-Free Surface Mount Technology 1 Jennifer Nguyen and Jasbir Bath
1.1 Introduction 1
1.2 Lead-Free Solder Paste Alloys 1
1.3 Solder Paste Printing 2
1.3.1 Introduction 2
1.3.2 Key Paste Printing Elements 2
1.4 Component Placement 5
1.4.1 Introduction 5
1.4.2 Key Placement Parameters 5
1.4.2.1 Nozzle 6
1.4.2.2 Vision System 6
1.4.2.3 PCB Support 6
1.4.2.4 Component Size, Packaging, and Feeder Capacity 6
1.4.2.5 Feeder Capacity 6
1.5 Reflow Process 7
1.5.1 Introduction 7
1.5.2 Key Parameters 7
1.5.2.1 Preheat 7
1.5.2.2 Soak 8
1.5.2.3 Reflow 8
1.5.2.4 Cooling 9
1.5.2.5 Reflow Atmosphere 9
1.6 Vacuum Soldering 9
1.7 Paste in Hole 10
1.8 Robotic Soldering 11
1.9 Advanced Technologies 12
1.9.1 Flip Chip 12
1.9.2 Package on Package 12
1.10 Inspection 13
1.10.1 Solder Paste Inspection (SPI) 13
1.10.2 Solder Joint Inspection 14
1.10.2.1 Automated Optical Inspection (AOI) 14
1.10.2.2 X-ray Inspection 15
1.11 Conclusions 16
References 17
2 Wave/Selective Soldering 19 Gerjan Diepstraten
2.1 Introduction 19
2.2 Flux 19
2.2.1 The Function of a Flux 19
2.2.2 Flux Contents 20
2.3 Amount of Flux Application on a Board 20
2.4 Flux Handling 21
2.5 Flux Application 21
2.5.1 Methods to Apply Flux (Wave Soldering) 21
2.5.2 Methods to Apply Flux (Selective Soldering) 23
9 PCB Laminates (Including High Speed Requirements) 307 Karl Sauter and Silvio Bertling
9.1 Introduction 307
9.2 Manufacturing Background 307
9.3 PCB Fabrication Design and Laminate Manufacturing Factors Affecting Yield and Reliability 308
9.3.1 High Frequency Loss 308
9.3.2 Mixed Dielectric 308
9.3.3 Back-Drilling 309
9.3.4 Aspect Ratio 309
9.3.5 PCB Fabrication 309
9.3.6 Press Lamination 310
9.3.7 Moisture Content 310
9.3.8 Laminate Material 311
9.4 Assembly Factors Affecting Yields and Long-Term Reliability for Laminate Materials 311
9.4.1 Reflow Temperature 311
9.4.2 Assembly Components 312
9.4.3 Thermal Stress 312
9.5 Copper Foil Trends (by Silvio Bertling) 312
9.6 High Frequency/High Speed and Other Trends Affecting Laminate Materials 316
9.6.1 High Speed Standards 316
9.6.2 Adhesion Treatment (Prior to Press Lamination) 317
9.6.3 Laminate Material Filler Content 317
9.6.4 GlassWeave Effect 317
9.6.5 Halogen-Free 318
9.7 Conclusions 318
References 319
10 Underfills and Encapsulants Used in Lead-Free Electronic Assembly 321 Brian J. Toleno
10.1 Introduction 321
10.2 Rheology 322
10.2.1 Rheological Response and Behavior 323
10.2.1.1 Thixotropy 325
10.2.2 Measuring Rheology 327
10.2.2.1 Spindle Type Viscometry 327
10.2.2.2 Cone and Plate Rheometry 328
10.3 Curing of Adhesive Systems 330
10.3.1 Thermal Cure 330
10.3.2 Ultraviolet (UV) Light Curing 335
10.3.3 Moisture Cure 338
10.4 Glass Transition Temperature 339
10.5 Coefficient of Thermal Expansion (CTE) 341
10.6 Young’s Modulus (E) 343
10.7 Applications 344
10.7.1 Underfills 344
10.7.1.1 Capillary Underfill 345
10.7.1.2 Fluxing (No-Flow) Underfill 348
10.7.1.3 Removable/Reworkable Underfill 349
10.7.1.4 Staking or Corner Bond Underfill 349
10.7.2 Encapsulant Materials 350
10.7.2.1 Glob Top 351
10.7.2.2 Component Encapsulation 351
10.7.2.3 Application 353
10.7.2.4 Low-Pressure Molding 355
10.8 Conclusions 355
References 355
11 Thermal Cycling and General Reliability Considerations 359 Maxim Serebreni
11.1 Introduction to Thermal Cycling of Electronics 359
11.1.1 Influence of Solder Alloy Composition and Microstructure on Thermal Cycling Reliability 362
11.2 Influence of Package Type and Thermal Cycling Profile 363
11.2.1 Influence of Board and Pad Design 366
11.3 Fatigue Life Prediction Models 371
11.3.1 Empirical Models and Acceleration Factors 371
11.3.2 Semi-empirical Models 372
11.3.3 Finite Element Analysis (FEA) Based Fatigue Life Predictions 373
11.4 Conclusions 376
References 377
12 Intermetallic Compounds 381 Alyssa Yaeger, Travis Dale, Elizabeth McClamrock, Ganesh Subbarayan, and Carol Handwerker
12.1 Introduction 381
12.1.1 Solders 382
12.1.2 Interaction with Substrates 382
12.2 Setting the Stage 384
12.2.1 Mechanical and Thermomechanical Response of Solder Joints 386
12.3 Common Lead-Free Solder Alloy Systems 392
12.3.1 Solder Joints Formed Between Sn-Cu, Sn-Ag, and Sn-Ag-Cu Solder Alloys and Copper Surface Finishes 396
12.3.1.1 Sn-Cu Solder on Copper 396
12.3.1.2 Sn-Ag and Sn-Ag-Cu Solder Alloys on Copper 399
12.3.2 Solder Joints Formed Between Sn-Cu, Sn-Ag, and Sn-Ag-Cu Alloys and Nickel Surface Finishes 408
12.3.2.1 Ni-Sn 408
12.3.2.2 Sn-Ag Solder Alloys on Nickel 411
12.3.2.3 Spalling 415
12.3.2.4 Effects of Phosphorus Concentration in ENIG on Solder Joint Reliability 416
12.3.3 Au-Sn 417
12.4 High Lead – Exemption 422
12.5 Conclusions 423
References 423
13 Conformal Coatings 429 Jason Keeping
13.1 Introduction 429
13.2 Environmental, Health, and Safety (EHS) Requirements 430
13.3 Overview of Types of Conformal Coatings 430
13.3.1 Types of Conformal Coatings 431
13.3.1.1 Acrylic Resins (Type AR) 432
13.3.1.2 Urethane Resins (Type UR) 433
13.3.1.3 Epoxy Resins (Type ER) 433
13.3.1.4 Silicone Resins (Type SR) 435
13.3.1.5 Para-xylylene (Type XY) 436
13.3.1.6 Synthetic Rubber (Type SC) 437
13.3.1.7 Ultra-Thin (Type UT) 438
13.4 Preparatory Steps Necessary to Ensure a Successful Coating Process 440
13.4.1 Assembly Cleaning 440
13.4.2 Assembly Masking 440
13.4.3 Priming and Other Surface Treatments 441
13.4.3.1 Measuring Surface Energy 441
13.4.3.2 Water Drop Contact Angle 447
13.4.4 Bake-Out 448
13.5 Various Methods of Applying Conformal Coating 449
13.5.1 Manual Coating 449
13.5.2 Dip 449
13.5.3 Hand Spray 450
13.5.4 Automatic Spray 451
13.5.5 Selective Coating 451
13.5.6 Vapor Deposition 451
13.6 Aspects for Cure, Inspection, and Demasking 453
13.6.1 Cure 453
13.6.1.1 Solvent Evaporation 453
13.6.1.2 Room Temperature Vulcanization (RTV) 454
13.6.1.3 Heat Cure 454
13.6.1.4 UV Cure 454
13.6.1.5 Catalyzed 454
13.6.2 UV Inspection 455
13.6.3 Demasking 455
13.7 Repair and Rework Processes 456
13.7.1 Chemical 456
13.7.2 Thermal 456
13.7.3 Mechanical 457
13.7.4 Abrasion (Micro-Abrasion) 457
13.7.5 Plasma Etch 457
13.8 Design Guidance on When and Where Conformal Coating is Required, and Which Physical Characteristics and Properties are Important to Consider 457
13.8.1 Is Conformal Coating Required? 458
13.8.1.1 Why Use It? 458
13.8.1.2 Why Not Use Conformal Coating? 459
13.8.2 Desirable Material Properties 459
13.8.3 Areas to Mask 461
13.9 Long-Term Reliability and Testing 462
13.10 Conclusions 462
13.11 Future Work 463
References 463
Index 467
Lead-free Soldering Process Development and Reliability provides a comprehensive discussion of all modern topics in lead-free soldering. Perfect for process, quality, failure analysis and reliability engineers in production industries, this reference will help practitioners address issues in research, development and production.
Among other topics, the book addresses:
· Developments in process engineering (SMT, Wave, Rework, Paste Technology)
· Low temperature, high temperature and high reliability alloys
· Intermetallic compounds
· PCB surface finishes and laminates
· Underfills, encapsulants and conformal coatings
· Reliability assessments
In a regulatory environment that includes the adoption of mandatory lead-free requirements in a variety of countries, the book’s explanations of high-temperature, low-temperature, and high-reliability lead-free alloys in terms of process and reliability implications are invaluable to working engineers.
Lead-free Soldering takes a forward-looking approach, with an eye towards developments likely to impact the industry in the coming years. These will include the introduction of lead-free requirements in high-reliability electronics products in the medical, automotive, and defense industries. The book provides practitioners in these and other segments of the industry with guidelines and information to help comply with these requirements.