The wire bonding bible - now revised and expanded! Get the practical know-how you need to design and evaluate wire bonds engineered with the latest - and still-evolving- metallurgies. Extensively revised and updated, the Second Edition of George Harman's classic Wire Bonding in Microelectronics shows you step-by-step how to exploit new higherm density interconnection techniques and engineer reliable gonds at a very high yield. You get the hands-on guidance you need to test wire bonds...clean bond pads to improve bondability and realiability...solve cratering, heel cracks, bond fatigue, so-called purple plague and other mechanical problems....bond wires to multichip modules...and much, much more. You also get up-to-the-minute details on utilizing fine pitch SMT, applying new bonding metallurgies, and exploring wire sweep and the wire bonding mechanism.

Preface

Acknowledgments

Chapter 1.Technical Introduction to the Second Edition

 1.1 Wedge- and Bali-Bonding Machine Operations

 1.2 How to Approach Bonding Problems

1.2.1 Which materials can be ultrasonically bonded?

1.2.2 Assessing the bondability and reliability of proposed new bond systems

1.2.3 Some unusual uses of wire bonds

 1.3 References

Chapter 2. Ultrasonic Bonding Systems and Technologies (Including Ultrasonic Wire Bonding Mechanism)

 2.1 Introduction

 2.2 Ultrasonic Transducer and Tool Vibration Modes

 2.3 How Ultrasonic Bonds Are Made

 2.4 Bonding with High(er) Frequency Ultrasonic Energy

 2.5 In-Process (Real-Time) Bond Monitoring

 2.6 Wire-Bonding Technologies

2.6.1 Thermocompression bonding

2.6.2 Ultrasonic wedge bonding (small- and large-diameter wires)

2.6.3 Thermosonic ball and wedge bonding

  2.6.4 Choosing a wire-bonding technology

 2.7 Variations of Fine Wire-Bonding Technology

2.7.1 Ribbon wire bonding

2.7.2 Parallel gap and tweezer welding

 2.8 Major Chip Interconnection Alternatives to Wire Bonding(Flip Chip and TAB); Limits of Wire Bonding

 2.9 Flip Chip

2.9.1 TAB

2.9.2 Wire-bonding technology: a comparison

Chapter 3. Some Aspects of Bonding Wire Characteristics and Metallurgy that Can Affect Bonding. Reliability. or Testing

 3.1 Introduction

 3.2 Stress-Strain Characteristics of Bonding Wires

 3.3 Shelf-Life Aging of Bonding Wires

 3.4 General Discussion of Gold Bonding Wire

 3.5 Aluminum Wire for Ultrasonic Wedge Bonding

 3.6 Wire and Metallization Hardness

 3.7 Effect of EFO Polarity on Gold Wire and Its Metallurgy

 3.8 Metallurgical Fatigue of Bonding Wires

 3.9 Conductor Burnout

3.9.1 Bonding wires

3.9.2 Maximum allowable current for PCB and MCM conductors

 Appendix WM-1: A Listing of Useful ASTM Standards and

 Specifications on Bonding Wire and Its Testing

Chapter 4. Wire Bond Testing

 4.1 Introduction

 4.2 The Destructive Bond Pull Test

4.2.1 Variables of the bond pull test

4.2.2 Failure predictions that are based on pull test data

4.2.3 Effect of metallurgy and bonding processes on the bond pull force

4.2.4 Effect of wire elongation on bond pull force (large-diameter Al. and Au wire used in ball bonding)

 4.3 Nondestructive Pull Test

4.3.1 introduction

4.3.2 Metallurgical and statistical interpretation of NDP test

4.3.3 Assessment of any NDP test-induced metallurgical defects

4.3.4 Limitations of the NDP test

4.3.5 The current status of the NDPT (1996) for military and space applications

 4.4. Bali-Bond Shear Test

4.4.1 Introduction

4.4.2 Apparatus

4.4.3 A manual shear probe as an aid in setting up a ball bonder

4.4.4 Interferences to making accurate ball-shear testmeasurements

4.4.5 Ball-shear force versus bonded area

4.4.6 Effect of gold-aluminum intermetalUcs on the shear force

4.4.7 Pluck test

4.4.8 Comparison of the ball-shear and bond-pull tests

4.4.9 Applications of the ball-shear test

4.4.10 Shear test for wedge bonds

4.4.11 Ball-shear test standardization

 4.5 Evaluating Both the Ball and the Wedge Bond on a Single Wire

 4.6 Thermal Stress Test for AI-Au Wire Bond Reliability

 4.7 Future Issues in Wire Bond Testing

 4.8 Appendix TA-1: Typical Failure Modes of the Ball Shear Test

Chapter 5. Gold-Aluminum Intermetallic Compounds and Other Metallic Interface Reactions Encountered in Wire Bonding

 5.1 Gold-Aluminum Intermetallic Compound Formation and Classical Wire Bond Failures

5.1.1 Introduction

5.1.2 Intermetallic compound formation

5.1.3 The classical Au-AI compound failure modes

5.1.4 Reversing metallurgical interfaces

5.1.5 The effect of diffusion inhibitors and barriers

 5.2 Impurity-Accelerated Au-AI Bond Failures

5.2.1 The effect of halogens on the Au-AI bond system

5.2.2 Recommendations for removing or avoiding halogen contamination

5.2.3 Nonhalogen epoxy outgassing induced bond failures

 5.3 Nongold-Aluminum Bond Interfaces

5.3.1 Aluminum-copper wire-bond system

5.3.2 Aluminum metallization containing copper

5.3.3 Copper-gold wire bond system

5.3.4 Palladium-Au and -AI bonding system (used for lead framesl

5.3.5 The silver-aluminum wire bond system

5.3.6 Aluminum-nickel wire bond system

5.3.7 Au-Au. AI-AI. Au-Ag. and less-used monometallic bonding systems

 Appendix IA-1 :Rapid Bond Failure in Poorly Welded Au-AI Bonds

 Appendix IA-2:Various Bond-Related Corrosion Reactions

Chapter 6. Bond Failures Resulting from Gold-Plating Impurities and Conditions

 6.1 Introduction

 6.2 Specific Plating Impurities

 6.3 Hydrogen Gas in Plated Films

6.3.1 Hydrogen-induced package problems

6.3.2 Failure symptoms that appear similar to gas entrapments: Resistance drift

 6.4 Failures from Metallic impurities in or on Gold Films that Are Not an Intentional Part of Plating Baths

6.4.1 Introduction

6.4.2 Nickel

6.4.3 Copper

6.4.4 Chromium

6.4.5 Titanium

6.4.6 Tin

 6.5 Gold-Plating Standards

6.5.1 Recommendations for reliable gold-plated films

 6.6 Electroless Autocatalytic Gold

 6.7 Nongold Platings Used in Electronics Packaging

Chapter 7. Cleaning to Improve Bondability and Reliability

 7.1 Introduction

7.1.1 Molecular cleaning methods to enhance bondability and reliability

7.1.2 Ultraviolet-ozone cleaning

7.1.3 Plasma cleaning

7.1.4 Plasma cleaning mechanism

7.1.5 Discussion and evaluation of molecular and solvent cleaning methods

7.1.6 Problems encountered in using molecular cleaning methods

7.1.7 Burnishing

 7.2 The Sensitivity of Different Bonding Technologies to Surface Contamination

  Appendix CL-I: Circuit Damage Caused by Plasma Cleaning

  during Packaging

Chapter 8. Mechanical Problems in Wire Bonding

 8.1 Cratering

8.1.1 Introduction

8.1.2 Bonding machine characteristics and setup parameters

8.1.3 Bonding force

8.1.4 Tool wire-pad impact force

8.1.5 Causes of cratering--materials

8.1.6 Intermetallics

8.1.7 Silicon nodule-induced cratering

8.1.8 Cratering over polysilicon

8.1.9 Gallium arsenide cratering

8.1.10 Conclusions of cratering

 8.2 Cracks in the Heels of Ultrasonic Wedge Bonds

 8.3 The Effect of Acceleration. Vibrations. and Shock

8.3.1 Centrifuge effects on wire bonds

8.3.2 The effect of ultrasonic cleaning on wire bonds

8.3.3 The effect of shock and vibration tests on wire bonds

 8.4 Effects of Power and Temperature Cycling of Wire Bonds

 Appendix M-l: Fracture Toughness Defined

Chapter 9. High-Yield and Fine-Pitch Wire Bonding

 9.1 Introduction

 9.2 The Background Necessary to Achieve High-Yield Bonding

 9.3 The Requirements for High-Yield Bonding

9.3.1 Clean. bondable metallization

9.3.2 The bonding machine and its control

 9.4 Reliability for Small Numbers of Bonds (Small Sample Statistics)

 9.5 Package-Related Bond-Yield Issues

 9.6 Possible 6σ Yield Enhancements and Problems that Need Further Study

 9.7 Other Conclusions that May Affect Device Yield

9.7.1 Wire sweep

9.7.2 Wire looping

 9.8 Fine-Pitch Ball and Wedge Bonding

9.8.1 Introduction

9.8.2 Fine-pitch ball and wedge bonding

 9.9 The Problems of Fine-Pitch Bonding

 9.10 Conclusions

 9.11 Acknowledgments

Chapter 10. Wire Bonding to Multichip Modules and Other Soft Substrates

 10.1 Introduction

 10.2 Bonding to MCM-D Substrates

 10.3 Bonding to MCM-L Substrates

 10.4 The Effect of the Substrate's Material Properties on Wire Bonding

 10.5 Bonding Machine Considerations

 10.6 Additional Considerations when Using Wire Bonds in MCMS Running at High Clock Rates

10.6.1 Inductance of wire bonds

10.6.2 Skin-effect in typical MCM conductor metal structures

 10.7 Conclusions

 10.8 Acknowledgments

Glossary

Index