DIGITAL FRINGE PROJECTION SYSTEM FOR MEASURING WARPAGE OF PAINTED AND UNPAINTED PBGAS AND BOARDS AND FEA STUDIES OF PBGA WARPAGE A Dissertation Presented to The Academic Faculty by Sungbum Kang In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the George W. Woodruff School of Mechanical Engineering Georgia Institute of Technology August 2015 Copyright 2015 by Sungbum Kang DIGITAL FRINGE PROJECTION SYSTEM FOR MEASURING WARPAGE OF PAINTED AND UNPAINTED PBGAS AND BOARDS AND FEA STUDIES OF PBGA WARPAGE Approved by: Dr. I. Charles Ume, Advisor Dr. Jianjun Shi School of Mechanical Engineering School of Industrial & Systems Georgia Institute of Technology Engineering Georgia Institute of Technology Dr. Suresh K. Sitaraman Dr. Michael Mello School of Mechanical Engineering School of Mechanical and Civil Georgia Institute of Technology Engineering California Institute of Technology Dr. Thomas E. Michaels School of Electrical and Computer Engineering Georgia Institute of Technology Date Approved: [April 20, 2015] This dissertation is dedicated to my parents for their unconditional love and supports. ACKNOWLEDGEMENTS First and foremost, I would like to give glory to Jesus Christ, my Lord and Savior, for what I have been able to accomplish and to learn. I always thank Him for his faithfulness in keeping the promises in the Bible. During my studies for my Ph.D., I have kept this Bible verse paramount in my thoughts: “But seek first his kingdom and his righteousness, and all these things will be given to you as well (Matthew 6:33).” I wish to give special thanks to my advisor Professor Charles Ume for his guidance and support over the years. I believe what I have accomplished was only possible because of his direction and patience with me. His influence has been greatly appreciated. I also would like to thank the other members of my Ph.D. thesis reading committee: Dr. Suresh Sitaraman, Dr. Thomas Michaels, Dr. Jianjun Shi, and Dr. Michael Mello for serving on my committee and for providing valuable suggestions. My thanks also go to Dr. Jiahui Pan, a former researcher at Aktometrix, for her useful advice. Additionally, I would like to acknowledge my colleagues in Dr. Ume’s group. Dr. Wei Tan and Dr. Reinhard Powell provided valuable suggestions at the early stage of my research, and Dr. Tsun-yen Wu was a good friend and valuable mentor. I thank Jie Gond, Lei Yang, and James Kelly for their help and for making my graduate school experience more valuable. Further, I thank Dr. Bong Choi, the senior pastor at Sugarloaf Korean Baptist Church, and his wife, Tina Choi, for mentoring me with so much love and express my gratitude to my fellow church members for their love and friendship in God. And I could iv not have asked for better friends, Dr. Jinsung Hong and his wife, Dr. Shinae Kim, who have shared part of my life journey. My deepest thanks go to my family, Suejean, Sungduk, Sujung, Youngsook, Wonchul, and my lovely niece and nephew, Jihae and Ian. They have been truly supportive of me during my Ph.D. studies, and even before that. Finally, this work is dedicated to my parents, Dr. Moonmyung Kang and Choonhang Jun. My accomplishments are possible only because of their love and true sacrifice. v TABLE OF CONTENTS Page ACKNOWLEDGEMENTS ............................................................................................... iv LIST OF TABLES .............................................................................................................. x LIST OF FIGURES .......................................................................................................... xii LIST OF SYMBOLS ....................................................................................................... xvi LIST OF ABBREVIATIONS ......................................................................................... xvii SUMMARY ..................................................................................................................... xix 1 INTRODUCTION 1 1.1 Electronic Packaging Technologies .................................................................. 1 1.2 SMT Assembly Process .................................................................................... 5 1.3 Warpage and the Thermomechanical Reliability of Chip Packages ................. 7 1.4 Warpage Measurement and Prediction ............................................................. 8 1.5 Research Objectives .......................................................................................... 9 2 LITERATURE REVIEW 13 2.1 Warpage Measurement Techniques ................................................................ 13 2.1.1 Contact Type .......................................................................................... 13 2.1.2 Non-Contact Type .................................................................................. 15 2.2 Digital Fringe Projection Technique ............................................................... 27 2.3 Application of the FEA to Investigate the Warpage Behavior in Chip Packages and Boards............................................................................................. 31 vi 3 IMPROVEMENT OF THE MEASUREMENT CAPABILITIES OF THE LFP SYSTEM BY REDUCING LASER SPECKLE NOISE AND POST-PROCESSING TIME 33 3.1 LFP System Configuration ............................................................................. 33 3.2 Reduction of the Laser Speckle Noise of the LFP System by Optimizing Its Laser Power, Camera Exposure, and Camera Gain .............................................. 34 3.2.1 Measurement Accuracy and Repeatability of the LFP System ............. 36 3.2.2 Design of Experiments and Experimental Results ................................. 37 3.2.3 Analysis of Experimental Results .......................................................... 40 3.2.4 Determination of the Optimum Values of the Control Parameters ........ 41 3.2.5 Validation of the Optimum Values of the Control Parameters .............. 43 3.3 Region Growing Method for Chip Package Segmentation............................. 44 3.4 Chapter Summary ........................................................................................... 51 4 DEVELOPMENT OF A DFP SYSTEM FOR MEASURING THE WARPAGE OF PAINTED AND UNPAINTED CHIP PACKAGES AND BOARDS 52 4.1 Development of a Digital Fringe Projection System ...................................... 52 4.1.1 DFP System Configuration .................................................................... 53 4.1.2 Customized Software of the DFP System .............................................. 54 4.1.3 Intensity Calibration of the DFP System ............................................... 55 4.1.4 Validation of the DFP System ............................................................... 57 4.2 Experimental Comparison of the LFP and DFP Systems ............................... 58 4.2.1 Quality of the Fringe Images ................................................................. 58 4.2.2 Practical Measurement Resolution, Accuracy, and Repeatability ......... 59 vii 4.2.3 Measurement Speed ............................................................................... 60 4.2.4 Measurement of PWBA Warpage ......................................................... 62 4.3 Dynamic Digital Fringe Projection Technique for Measuring the Warpage of Unpainted Chip Packages and Boards .................................................................. 64 4.3.1 Coordinate Calibration Between Projected and Captured Images ......... 68 4.3.2 Segmentation of the PBGA Package and PWB Regions in Unpainted PWBA Images ................................................................................................ 70 4.3.3 Intensity Calibration Between Projected and Captured Images ............ 77 4.3.4 Generation and Projection of a Dynamic Fringe Pattern ....................... 79 4.3.5 Validation of the DDFP Technique ....................................................... 79 4.4 Chapter Summary ........................................................................................... 85 5 PARAMETRIC STUDIES OF THE EFFECTS OF SOLDER BUMP PITCH, PACKAGE SIZE, AND MOLDING COMPOUND AND SUBSTRATE THICKNESSES ON WARPAGE OF PBGA PACKAGES USING THE FEA 87 5.1 FE Model ........................................................................................................ 88 5.2 Reflow Profile ................................................................................................. 90 5.3 Validation of the FE Model ............................................................................ 91 5.4 Design of Simulations and Simulation Results ............................................... 92 5.5 Analysis of Simulation Results ....................................................................... 95 5.6 Regression Equations of PBGA Warpage ...................................................... 98 5.7 Chapter Summary ........................................................................................... 99 6 DEVELOPMENT OF A SELECTION GUIDELINE OF WARPAGE MEASUREMENT TECHNIQUES 101 viii 6.1 Features of Warpage Measurement Techniques ........................................... 101 6.2 Comparison of Features of Various Warpage Measurement Techniques .... 104 6.2.1 Contact-Type ........................................................................................ 104 6.2.2 Non-Contact Type ................................................................................ 105 6.3 Selection Guideline of Warpage Measurement Techniques ......................... 111 6.4 Chapter Summary ......................................................................................... 117 7 CONCLUSIONS 118 7.1 Conclusions ................................................................................................... 118 7.2 Summary of Contributions ............................................................................ 122 7.3 Recommendations for Future Work.............................................................. 123 APPENDIX A C PROGRAM CODE FOR THE RGM ................................................. 126 APPENDIX B APDL CODE FOR THE PARAMETRIC STUDY ............................... 131 REFERENCES ............................................................................................................... 138 ix LIST OF TABLES Page Table 1.1. Forecast of the relative share of production of the various chip packages ........ 5 Table 3.1. The results of the pre-trial experiments ........................................................... 38 Table 3.2. The three levels of each control parameter (P, E, and G) ................................ 39 Table 3.3. The design of experiments and experimental results ....................................... 39 Table 3.4. The p-values of each control parameter ........................................................... 40 Table 3.5. The experimental results used to obtain the regression equations ................... 42 Table 3.6. Comparison of Ɛ and σ obtained from the experiments and the regression equations ........................................................................................................................... 43 Table 3.7. Comparison of Ɛ and σ before and after optimization ..................................... 44 Table 3.8. Comparison of two automated segmentation methods .................................... 45 Table 3.9. Comparison of the processing times of the mask image model and the RGM 51 Table 4.1. Comparison of the features of the LFP and DFP techniques ........................... 53 Table 4.2. The measurement results obtained using the calibration block ....................... 57 Table 4.3. Comparison of the measurement results obtained using the calibration block 60 Table 4.4. Comparison of the accuracy and repeatability ................................................. 60 Table 4.5. Definition of the data acquisition and processing times of the LFP and DFP systems .............................................................................................................................. 61 Table 4.6. Comparison of the practical data acquisition and processing times of the LFP and DFP systems ............................................................................................................... 61 Table 4.7. Comparison of the warpage measurement results ........................................... 63 x