ADHESION MECHANISMS OF NANO-PARTICLE SILVER TO ELECTRONICS PACKAGING M A T E R I A L S A The sis Presented to The Academic Faculty B y Sung Chul Joo In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in Mechanical Engineering I N S T A • I T I U G T R E O • E O G F • • E T H E T C • H F P R O G R ESS S E R V I C E N O A N D O • L L O A G E Y S • • 1885 Georgia Institute of Technology December, 2009 Copyright © 2009 by Sung Chul Joo ADHESION MECHANISMS OF NANO-PARTICLE SILVER TO ELECTRONICS PACKAGING M A T E R I A L S Approved by: Dr. Daniel F. Baldwin, Advisor Dr. C. P. Wong School of Mechanical Engineering Materials Science and Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Steven Danyluk Dr. Paul A. Kohl School of Mechanical Engineering Chemical and Biomolecular Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Jianmin Qu School of Mechanical Engineering Georgia Institute of Technology Date Approved: June 10 th , 2009 To my families: Sung Yong Lee, Chan Woo Joo, and Sa Rang Joo My parents and parents-in-law ACKNOWLEDGEMENTS I would like to thank my God for leading me to be here today and to write these acknowledgements. I wish to thank Dr. Daniel F. Baldwin, my thesis advisor, for his indispensable guidance on my thesis research and financial support throughout my graduate student period. I would like to thank Sun Yong Lee, my wife, for her patience and love during the entire process. This thesis could not have been written without her endless support and belief. I wish to express my appreciation to my thesis committee members, Dr. Steven Danyluk, Dr. Jianmin Qu, Dr. Paul A. Kohl, and Dr. C. P. Wong for their invaluable comments and advice on my thesis. The help of Dr. Jeffrey Donnell is also greatly appreciated. His English corrections are just like adding two wings on the author’s thoughts to be more clearly conveyed to the world. I would like to thank Dr. Kyoun-Sik Moon, Dr. Chunho Kim, Ms. Lehang La, and Mr. Sangil Lee for their willing to help my research. I wish to acknowledge the praying of my church members, Prof. Jeongsik Jay Lee, Mr. Jin Yoon Cho, Mr. Jung hyuk Park, Mr. Yoon Hyuk Lim, Mr. Seil Lee, Dr. Seong Joon Paik, Mr. Seong Ho Paik, and Mr. Meoung Hoon Jeon. Without their prayers, this work would have taken longer time. Finally, I wish to thank my parents and parents-in-law for their endless belief and love. I always respect their lives as the great sacrifice for their children. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS iii LIST OF TABLES viii LIST OF FIGURES x LIST OF SYMBOLS xiii SUMMARY xvi CHAPTER 1 INTRODUCTION ··················································································1 1.1 Problem statement ···································································································1 1.2 Thesis objectives and structure ···············································································2 CHAPTER 2 MOTIVATION AND BACKGROUND ··················································5 2.1 Chip First Packaging Technology·············································································5 2.1.1 Substrate ·········································································································7 2.1.2 Die Attach·······································································································8 2.1.3 Lamination····································································································12 2.1.4 Micro-Via Formation ····················································································15 2.1.5 Screen Printing······························································································17 2.1.6 Aerosol-jet Printing·······················································································19 2.1.7 Multilayer Packaging ····················································································21 2.1.8 Summary·······································································································22 2.2 Nano-Particle Metals (NPM) ················································································23 2.3 Nano-Particle Silver (NPS) Adhesion·····································································25 iv CHAPTER 3 ADHESION MECHANISMS ·······························································28 3.1 General Adhesion Mechanisms ··············································································28 3.1.1 Physical Adsorption ······················································································28 3.1.2 Electrostatic Force·························································································30 3.1.3 Particle Adhesion ··························································································31 3.1.4 Mechanical Interlocking················································································33 3.1.5 Chemical Bonding·························································································33 3.1.6 Diffusion·······································································································35 3.1.7 Paint Adhesion and Others ············································································40 3.2 Sintering Mechanisms····························································································42 3.3 Relevant Adhesion Mechanism of NPS··································································44 3.4 Plausible Adhesion Factors of NPS ········································································47 CHAPTER 4 ADHESION EXPERIMENTS ······························································49 4.1 Introduction ···········································································································49 4.2 Experimental Procedure·························································································50 4.2.1 Thickness Control ·························································································51 4.2.2. ASTM Tape Test ··························································································52 4.2.3 Test Materials································································································53 4.3. Experimental Results ····························································································56 4.3.1 Substrate Hardness························································································56 4.3.1.1 Organic Substrates················································································56 4.3.1.2 Inorganic Substrates ·············································································62 4.3.2 Surface Energy Change·················································································63 4.3.2.1 Contact Angle Measurement·································································65 v 4.3.2.2 Results and Discussion·········································································65 4.3.3 Chemical Bonding·························································································67 4.3.3.1 Hydrogen Bonding···············································································67 4.3.3.2 Covalent & Ionic Bonding····································································68 4.3.4 Surface Roughness························································································71 4.3.4.1 Surface Roughness Measurement ·························································71 4.3.4.2 Results and Discussion·········································································73 4.3.5 Diffusion & Metallic Bonding ·····································································76 4.4 Summary ···············································································································78 CHAPTER 5 QUANTITATIVE ADHESION STRENGTH MEASUREMENT··········80 5.1 Conventional Adhesion Test Methods ····································································80 5.2 Modified Button Shear Test ···················································································82 5.2.1 Loading Conditions·······················································································84 5.2.2 Test Method Development·············································································84 5.2.3 Fracture Force·······························································································85 5.2.4 Button Dimensions························································································87 5.2.5 FEM Analysis ·······························································································88 5.2.6 Interfacial Fracture Criterion ·········································································90 5.2.7 Kendall Model ······························································································91 5.3 Results and Discussion ·························································································93 5.3.1 Stress Distributions ·······················································································93 5.3.2 Thermal Residual Stress Distributions···························································94 5.3.3 Fracture Initiation Location···········································································95