NNT 2016SACLV112 THESE DE DOCTORAT DE L''''UNIVERSITE PARIS SACLAY Préparée a L’Université de Versailles Saint Quentin en Yvelines ÉCOLE DOCTORALE N0580 (STIC) Spécialité de doctorat Automatique Par M Qu[.]
NNT : 2016SACLV112 THESE DE DOCTORAT DE L'UNIVERSITE PARIS-SACLAY Préparée a L’Université de Versailles Saint-Quentin-en-Yvelines ÉCOLE DOCTORALE N0580 (STIC) Spécialité de doctorat: Automatique Par M Quang Bang TAO Titre de la thèse: Nouvelles Brasures Sans Plomb: Conception Des Dispositifs D'essai, Fabrication Des Échantillons et Caractérisation Titre de la thèse en anglais: New Lead-Free Solders: Testing Device Development, Specimen Fabrication, and Characterization Thèse présentée et soutenue Vélizy, le 06 Décembre 2016 : Composition du Jury: M Fabrice Brémand M Abdelkhalak El Hami M Yves Bienvenu M Frédéric Mazaleyrat Mme Florence Le-Strat M Yasser Alayli M Jean-Michel Morelle M Lahouari Benabou M Fethi Ben Ouezdou Professeur, Université de Poitiers, Institut Pprime Professeur, INSA de Rouen Professeur honoraire, ParisTech Professeur, ENS Cachan, Université Paris Saclay Expert, Renault Technocentre Professeur, UVSQ, Université Paris Saclay Expert, Valeo, France MCF-HDR, UVSQ, Université Paris Saclay Professeur, UVSQ, Université Paris Saclay Rapporteur Rapporteur Examinateur Président Examinateur Invité Invité Co-Directeur Directeur ÉCOLE DOCTORALE Sciences et technologies de l'information et de la communication (STIC) Titre: Nouvelles Brasures Sans Plomb: Conception Des Dispositifs D'essai, Fabrication Des Échantillons et Caractérisation Mots clés: Sans-Plomb Brasures, Microstructure, Etude mécanique, Fiabilité Résumé: De nos jours, une des stratégies pour améliorer les propriétés des brasures sans plomb est d'introduire en petites quantités certains éléments d'alliage Dans notre étude, deux nouveaux types de brasures, dénommés Innolot et SAC-Bi et dont l'utilisation dans diverses applications électroniques augmente, sont caractérisées En particulier, l'effet des éléments Ni, Sb et Bi sur les propriétés mécaniques est analysé L'étude vise également évaluer l'influence des facteurs de sollicitation, du vieillissement en température sur la réponse des matériaux et leurs évolutions microstructurales A cet effet, une machine permettant de réaliser des essais de micro-traction sur ộprouvettes miniatures a ộtộ conỗue et fabriquộe Les sollicitations qu'elle permet d'appliquer sont multiples (traction, cisaillement et cyclage) et des conditions en température et en vitesse de déformation peuvent être imposées lors de l'essai La fabrication des éprouvettes nécessaires aux essais a également été entreprise dans cette étude afin d'avoir un matériau similaire celui issu du process industriel et de disposer d'une géométrie adaptée au type de caractérisation souhaitée (éprouvettes massives, simple recouvrement, etc.) Après ces étapes préparatoires, des tests ont été réalisés sous sollicitations de traction, cisaillement, fluage et fatigue en faisant varier les conditions d'essais Le premier objectif a été l'identification du comportement des brasures, y compris en prenant en compte l'effet du vieillissement Ces données ont permis ensuite de réaliser des simulations thermo-mécaniques sur les matériaux utilisés sous forme de joints de brasure dans un module de puissance sous cyclage thermique Les analyses de microstructure (SEM/EDS et EPMA) faites par la suite ont montré le rôle des éléments d'alliage (Ni, Sb et Bi) sur les performances mécaniques des brasures en termes de résistance, limite élastique et rigidité Le rôle des facteurs d'essai, comme la température, la vitesse de sollicitation et la durée de vieillissement, a également été mis en évidence au niveau des propriétés obtenues et des changements dans la microstructure Il a été établi que l'élément Sb permet de favoriser le durcissement par écrouissage des brasures, tandis que l'ajout des éléments Ni et Bi permettent un raffinement de la microstructure Les essais ont aussi permis d'identifier les paramètres de la loi d'Anand par une procédure numérique s'appuyant sur les données de traction et de cisaillement, permettant ainsi de réaliser des simulations par éléments finis Ces dernières suggèrent un meilleur comportement la fatigue pour la brasure Innolot qui bénéficie est effets favorables des additifs Title: New Lead-Free Solders: Testing Device Development, Specimen Fabrication, and Characterization Key words: lead-free solder, minor alloying additions, microstructure, reliability, mechanical study Abstract: thermal cycling The experimental results indicate that, Nowadays, one of the strategies to improve the reliability with addition of Ni, Sb and Bi in to SAC solder, the of lead-free solder joints is to add minor alloying stress levels (UTS, yield stress) are improved elements to solders In this study, new lead-free solders, Moreover, testing conditions, such as temperature, namely InnoLot and SAC387-Bi, which have begun to strain rate, amplitude, aging time, may have substantial come into use in the electronic packaging, were effects on the mechanical behavior and the considered to study the effect of Ni, Sb and Bi, as well as microstructure features of the solder alloys The that of the testing conditions and isothermal aging, on the enhanced strength and life time of the solders is attribute mechanical properties and microstructure evolution A to the solid hardening effects of Sb in the Sn matrix and new micro-tensile machine are designed and fabricated, the refinement of the microstructure with the addition of which can tensile, compressive and cyclic tests with Ni and Bi The nine Anand material parameters are variation of speeds and temperatures, for testing identified by using the data from shear and tensile tests miniature joint and bulk specimens Additionally, the And then, the obtained values were utilized to analyze procedure to fabricate appropriate lap-shear joint and the stress-strain response of an IGBT under thermal bulk specimens are described in this research The tests, cycling The results of simulations represent that the including shear, tensile, creep and fatigue tests, were response to thermal cycling of the new solders is better conducted by micro-tensile and Instron machine at than the reference solder, suggesting that additions of different test conditions The first study is to minor elements can enhance the fatigue life of the solder characterize, experimentally, the mechanical behaviors joints Finally, the SEM/EDS and EPMA analysis of asand life time of solder joints submitted to isothermal cast, as-reflowed as well as fractured specimens were aging and mechanical tests The second goal of the done to observe the effects of these above factors on the project is to perform thermo-mechanical simulations of microstructure of the solder alloys IGBT under i Abstract Due to the RoHS and WEEE legislations for restricting the use of six hazardous materials in the manufacture of various types of electronic and electrical equipment, developing novel Pb-free solders becomes a real challenge for many industrials in recent years Mechanical properties of the lead-free alloys are very important factors in the design and reliability evaluation of the soldered joints One of the strategies to improve the reliability of lead-free solder joints is to add minor alloying elements to solders Indeed, many researchers have demonstrated that the properties of Sn-Ag-Cu (SAC) solders can be enhanced with small additions of elements such as Bi, Ni, Sb, Zn, Ce, Among the newly-developed lead-free solder alloys, SAC387-Bi and SAC-Bi,Ni,Sb (InnoLot) alloys, which contain minor quantities of Sb, Bi and Ni, have been identified as promising candidates for the automotive industry In operation, the microstructure, mechanical response, and failure behaviour of the lead-free solder joints in the electronic assemblies are highly dependent on external factors such as the imposed thermal loads, the mechanical vibrations, the effect of aging, etc Hence, it is essential to understand how the mechanical properties of the newly-developed solder alloys vary with changes in testing conditions (strain rate, temperature), composition, and isothermal aging The first study is to characterize, experimentally, the mechanical behaviors and life time of solder joints using these new lead-free solders submitted to isothermal aging and accelerated thermo-mechanical tests Firstly, a ‘home-made’ micro-tension machine, which can tensile, compressive and cyclic tests with variation of speeds and temperatures, is designed and fabricated for testing miniature solder joint specimens Furthermore, a uniaxial Instron machine is used for testing flat and cylindrical bulk specimens The detailed procedures for fabricating all these types of specimens will be described in the manuscript Shear and creep tests on lapshear solder joint specimens were performed with the micro-tension machine Uniaxial tensile and cyclic fatigue tests for flat and cylindrical bulk specimens were carried out on Instron universal machine under various testing conditions In addition, in order to investigate the effect of aging several joint and bulk samples were kept in thermal oven at 1000C for different aging times (0-12 months) and then used for creep and tensile tests The experimental results indicate that, with addition of Ni, Sb and Bi into referenced SAC solder, the stress levels (UTS, yield stress) are improved Moreover, testing conditions, such as temperature, strain rate, amplitude, aging time, may have substantial ii effects on the mechanical behavior and the microstructure features of the solder alloys The enhanced strength and life time of the solders are attributed to the solid hardening effects of Sb in the Sn matrix and the refinement of the microstructure with the addition of Ni and Bi The second goal of the project is to perform thermo-mechanical simulations of IGBT under thermal cycling Based on the experimental results, the procedure for extracting the nine Anand material parameters was introduced using the data from shear and tensile experiments The findings with regard to the Anand viscoplastic constitutive model predictions are in good agreement with the experimental data and previous studies for other solder alloys And then, the obtained values were utilized to analyze the stress-strain response of an IGBT under thermal cycling The developed Anand constitutive equations have been implemented within the finite element code ABAQUS The results of simulations show that the response to thermal cycling of the new solders are better than the reference solder, suggesting that additions of minor elements can enhance the fatigue life of the solder joints The creep activation energy and stress exponent values were also obtained from creep data by using the Dorn power model Finally, the SEM/EDS and EPMA analysis of as-cast, as-reflowed as well as fractured specimens were done to observe the effects of testing conditions, alloying elements, and aging on the microstructure of the solder alloys iii Acknowledgements I am indebted to many people for the help along the journey Most importantly, I would like to express my sincere gratitude to my supervisor, Professor Lahouari Benabou for introducing me to very exciting research areas, for the continuous guidance, supervision and untiring support for my PhD study, and related research I want to say again a special thank you to Professor Benabou, for his collaborative approach to research and good nature This gave me great opportunities to gain a lot of research experiences, knowledge, and working methodology When I had problems in my research, he was willing to give me many useful advice and suggestions I could not have imagined having a better advisor and mentor for my PhD research In addition, I would like to thank Professor Fethi Ben Ouezdou for his direction and his availability despite his many administrative responsibilitiesin the University of Versailles over the last years, as well as Professor & Director of LISV Luc Chassagne for welcoming and allowing me to my research in his laboratory I would also like to express my gratitude to many Professors in the University Paris-Saclay for their lectures My sincere thanks are to all members of the review committee for taking time to examine my work and for providing valuable advices during my dissertation evaluation I would like to thank the industrial partners and experts from Valeo, special thanks to J.M Morelle, M Vivet, and K.L Tan They have played a critical role in this work through helpful discussions, guidance, and advice Concerning my comrades in the laboratory LISV, whether they are PhD students or technicians, their friendship, and moral support made my life much easier in France I must thank also the Vietnamese Government for providing me with the financial support to carry out this work during three years and to obtain the PhD degree Similarly, I must thank the company Valeo for helping me with a financial complement to my scholarship Last but not the least, I am grateful to my parents, my family, my parents in-law and my siblings for their support and understanding Special thanks to my wife Ngoc Anh and lovely daughter Minh Chau, for their endurance, perseverance, heartfelt consideration Their smile kept my spirit high during all these years TAO Quang Bang iv Table of Contents Abstract i Acknowledgements iv List of Figures ix List of Tables xiii List of Abbreviations xiv List of Publications xv CHAPTER 1: GENERAL INTRODUCTION 1.1 Introduction 1.2 Lead-free Solders 1.3 Sn-Ag-Cu Solder Alloys as Popular Choices 1.4 Novel Lead-free Solder Alloys for Automotive Industry 1.5 Mechanical Properties of Solder Materials 1.5.1 Tensile Stress and Strain 1.5.2 Creep 11 1.5.3 Shear 13 1.5.4 Fatigue 15 1.6 Research Objectives 17 1.7 Organization of the Dissertation 18 CHAPTER 2: 21 LITERATURE REVIEW 21 2.1 Introduction 22 2.2 Effect on Mechanical Properties and Microstructure of Alloying Elements Added to the Sn-Ag-Cu System 23 2.3 Effects of Strain Rate and Temperature on Solder Joints 24 2.4 Effect of Aging Time on Solder Material Properties 24 2.5 Constitutive Modeling for Solder Materials 26 2.5.1 Constitutive Modeling for Stress-Strain Tests 27 2.5.2 Constitutive Modeling for Creep Tests 28 2.6 Digital Image Correlation 29 v 2.7 Summary and Discussion 29 CHAPTER 3: 33 MICRO-TENSION MACHINE AND THE INTERFACE 33 3.1 Introduction 34 3.2 Design of the Micro-tension Machine 34 3.3 The Control Interface 40 3.3.1 LabView Interface for Tensile and Shear Tests 40 3.3.2 LabView Interface for Creep Test 41 3.3.3 Data Acquisition 42 3.4 Summary and Discussion 43 CHAPTER4: 45 SPECIMEN PREPARATION AND EXPERIMENTAL TESTING 45 4.1 Introduction 46 4.2 Lead-Free Solder Materials 47 4.3 Solder Joint Specimen Preparation Procedure 48 4.4 Solder Bulk Specimens Preparation Procedure 54 4.4.1 Solder Bulk Specimens for Tensile Tests 54 4.4.2 Solder Bulk Specimens for Fatigue Tests 56 4.5 Experimental Plan 57 4.5.1 Shear and Creep Tests 57 4.5.2 Tensile and Fatigue Tests 60 4.5.3 Aging Specimens for Creep and Tensile Tests 65 4.6 Microstructure Analysis 66 4.7 Summary and Discussion 66 CHAPTER 5: 69 EXPERIMENTAL RESULTS 69 5.1 Introduction 71 5.2 Microstructure Analysis 71 5.2.1 Microstructure and Distribution of Elements for As-cast Specimens 72 5.2.2 As-fabricated Microstructure Analysis of Solder Joint Specimens 75 5.3 Results of Shear Tests 77 vi 5.3.1 Shear Strain-Stress Curves 77 5.3.2 Effects of Testing Conditions and Alloying Elements on Mechanical Properties 79 5.3.3 Fractured Solder Joints After Shear Tests 82 5.4 Tensile Behavior 85 5.4.1 Tensile Stress-Strain Curves 85 5.4.2 Effects of Testing Conditions and Alloying Elements on UTS and Yield Stress 86 5.4.3 Effects of Testing Conditions and Alloying Elements on Young’s modulus and Elongation 89 5.4.4 Microstructure Analysis of Fractured Solder Bulk Specimens after Tensile Tests 90 5.5 Creep Behavior 94 5.5.1 Creep Curves 94 5.5.2 Effects of Applied Stress and Temperature on Creep Behavior 95 5.5.3 Fractured Solder Joints after Creep Tests 97 5.6 Fatigue Behavior 100 5.6.1 Overview of Cyclic Stress-Strain Behavior 100 5.6.2 Fatigue Test Results 101 5.6.2.1 Cyclic Stress Response Behavior 104 5.6.2.2 Effect of Temperature on Fatigue Life 107 5.6.2.3 Effect of Frequency (Strain Rate) on Fatigue Life 106 5.7 Effect of Isothermal Aging 107 5.7.1 Aging Effect on Tensile Properties 107 5.7.1.1 Effect of day Aging at 1000C 107 5.7.1.2 Effect of days, 30 days and 90 days Aging at 1000C 108 5.7.2 Aging Effect on Creep Behavior 110 5.7.2.1 Creep Behavior after Aging 110 5.7.2.2 Effect of Aging Time on the Microstructure in the case of creep 111 5.8 Summary and Conclusion 114 CHAPTER 6: 117 CONSTITUTIVE MODELS ANDFINITE ELEMENT SIMULATION 117 6.1 Introduction 118 6.2 Anand Viscoplastic Constitutive Model 118 6.2.1 Determination of the Anand Material Parameters for Shear Strain-Shear Stress and Tensile Strain-Stress Data 123 vii 6.2.2 Correlation of the Anand Model Predictions and Experimental Results 124 6.3 Creep Constitutive Model 128 6.4 Finite Element Simulation of the Solder Joint in the IGBT Module Under Thermal Loading 132 6.4.1 Insulated-Gate Bipolar Transistor Configuration 132 6.4.2 The Finite Element Model 133 6.4.3 Loading Conditions 134 6.4.4 FE Results and Discussion 135 6.5 Summary and Conclusion 138 CHAPTER 7: 140 SUMMARY, CONCLUSIONS AND PERSPECTIVES 140 7.1 Literature Review 141 7.2 Testing Device Development, Specimen Preparation and Experimental Setup 142 7.3 Effects of Element Additions, Testing Conditions and Aging on Mechanical Properties and Microstructure of Solder Alloys 142 7.4 The Anand Viscoplastic Constitutive Model and Power Creep Model 144 7.5 Thermal Cycling Reliability Prediction for Lead-Free Solder Joint in IGBT Assemblies 144 7.6 Perspectives 145 Bibliography 147 viii List of Figures Figure 1.1 Lead-free Solder Market Share Figure 1.2 Prevailing Lead-free Solder Choices and Their Applications Figure 1.3 SAC Ternary Phase Diagram Figure 1.4 SEM Micrograph of Typical SAC Solder Figure 1.5 Testing Schematic for Solder Alloys Figure 1.6 Typical Stress-Strain Response for Ductile Materials Figure 1.7 Typical Creep Response for Ductile Materials Figure 1.8 Typical Shear Stress-Strain Response for Ductile Materials Figure1.9 A hysteresis loop for fatigue test of total strain range of 0.3% at room temperature and 0.0033 Hz Figure 1.10 A relationship between tensile stress amplitude with number of cycles for total strain range of 0.3% at room temperature and 0.0033 Hz Figure 3.1 The overall experimental setup Figure 3.2 Schematic of the gripping: (a), (b) dimension of gripping (unit: mm) and (c), (d) the established griping Figure 3.3 LVDT (a) and Load cell (b) sensors used for the micro-tester Figure 3.4 The signal conditioner for LVDT (a) and load cell (b) Figure 3.5 Heating foil (a) and thermocouple (b) Figure 3.6 The DAQ 16-bit National Instrument card Figure 3.7 The micro-tensile machine Figure 3.8.LabView interface used for monotonic tests Figure 3.9.LabView interface used for creep test Figure 3.10 Basic data acquisition Figure 3.11 Configuration of the DAQ assistant Figure 4.1 Schematic for types of specimens and experimental setup Figure 4.2 Electrical Discharge Machining machine Figure 4.3 Solder flux gel Figure 4.4 Solder sheets Figure 4.5 The reflow profiles: SAC-Bi solder joint (a); InnoLot solder joint (b) Figure 4.6 The fixture for the assembled specimen during the reflow process: the drawing (a) and actual fixture (b) (unit: mm) ix Figure 4.7 The procedure for fabricating a lap shear joint specimen (a), its dimension (b) Figure 4.8 Solder material (a), graphite cup (b), and metal mold (c) Figure 4.9.The procedure for fabricating the flat dog-bone bulk specimens and their dimensions (all dimensions are in mm) Figure 4.10 Dimension of the cylindrical specimen and its actual specimen Figure 4.11 Shear and Creep Experimental Setup Figure 4.12 The testing apparatus for the tensile and fatigue tests Figure 4.13 Typical stress-strain curve for InnoLot solder alloy Figure 4.14.Stress-strain curves for different samples subjected to the same testing conditions Figure 5.1 SEM (a) and EPMA (b) machines Figure 5.2 The microstructures of the as-cast: SAC-Bi (a) and InnoLot (b) Figure 5.3 The mapping of several elements in InnoLot solder detected by EPMA Figure The global view of the lap shear joints and the IMCs morphology: (a) SAC-Bi (b) InnoLot Figure 5.5 Shear stress-strain curves at different strain rates under room temperature for: (a) SAC-Bi solder joint and (b) InnoLot solder joint Figure 5.6 Shear stress-strain curves at different testing temperatures under the strain rate of 2.0 x 10-4 s-1 for: (a) SAC-Bi solder joint and (b) InnoLot solder joint Figure 5.7 Dependence of UTS on strain rate at different testing temperatures for: (a) SACBi solder joint and (b) InnoLot solder joint Figure 5.8 Dependence of yield stress on strain rate at different testing temperatures for: (a) SAC-Bi solder joint and (b) InnoLot solder joint Figure 5.9 Cross-sectional SEM images after a shear test at strain rate of 2.0 x 10-4 s-1 and room temperature for SAC-Bi solder joint Figure 5.10 Cross-sectional SEM images after a shear test at strain rate of 2.0 x 10-4 s-1 and room temperature for InnoLot solder joint Figure 5.11 Cross-sectional SEM images after a shear test at strain rate of 2.0 x 10-4 s-1 and 1250C for SAC-Bi solder joint Figure 5.12 Cross-sectional SEM images after a shear test at strain rate of 2.0 x 10-4 s-1 and 1250C for InnoLot solder joint Figure 5.13 The obtained uniaxial tensile curves for the InnoLot solder under all conditions (strain rates, temperatures) considered in the study x Figure 5.14 The effects of strain rate and temperature on the ultimate tensile strength (a) and yield stress (b) of InnoLot solder alloy Figure 5.15 The influence of strain rate and temperature on the Young’s modulus (a) and the elongation to rupture (b) of the InnoLot solder Figure 5.16 The details of fracture surfaces observed by EPMA after tensile testing under different temperatures at the same strain rate of 2.0 x 10-4 s-1 Figure 5.17 The details of fracture surfaces observed by EPMA after tensile testing under different strain rates at the same testing temperature of 250C Figure 5.18 SEM micrographs of fracture surfaces under tensile testing at different strain rates for testing temperature of 250C: (a) 2.0 x 10-3 s-1, (b) 2.0 x 10-4 s-1,(c) 2.0 x 10-5 s-1 Figure 5.19 SEM micrographs of fracture surfaces under tensile testing at different temperatures for strain rate of 2.0 x 10-3 s-1: (a) 250C, (b) 1250C Figure 5.20 A typical creep curve of the InnoLot solder joint at 250C and applied stress of 25.25 MPa Figure 5.21 The typical set of creep curves of the InnoLot solder joints at temperatures of 250C for different applied stress levels Figure 5.22 The typical set of creep curves at various temperatures and the same stress level of 11.875 MPa Figure 5.23 The SEM images of creep tests under 18.75 MPa at 250C: (a) global image, (b) details at different areas Figure 5.24.The SEM images of creep tests under 18.75 MPa at 1250C: (a) global image, (b) details at different areas Figure 5.25 The cyclic strain control for cyclic fatigue test Figure 5.26 Typical cyclic stress-strain testing for InnoLot solder Figure 5.27 The cyclic stress-strain hysteresis loop at the 10th cycle, for 0.4% total strain range, temperature of 250C and frequency of 0.0025 Hz Figure 5.28 Typical hysteresis loop and area calculation Figure 5.29 Relationship between tensile stress amplitude with number of cycles for total strain range of 0.3% at 250C and 0.025 Hz Figure 5.30 The typical cyclic stress behavior of the InnoLot solder: (a) 250C and (b) 1250C and different total strain ranges Figure 5.31.Hysteresis loops for total strain range of 0.1% at 0.025 Hz at 250C and 1250C xi Figure 5.32 Hysteresis loops for total strain range of 0.1% and 250C at: (a) 0.1 Hz and (b) 0.01 Hz Figure 5.33 Influence of aging on stress-strain curves of InnoLot after day at 1000 Figure 5.34 Influence of aging on stress-strain curves of InnoLot Figure 5.35 Influence of aging on creep curves of InnoLot Figure 5.36 The SEM images after the creep test with applied stress of 18.75MPa at 250C and aging at 1000C for month Figure 5.37 The SEM images after the creep test with applied stress of 18.75MPa at 250C and aging at 1000C for month Figure 5.38 The SEM images after the creep test with applied stress of 18.75MPa at 250C and aging at 1000C for month Figure 6.1 Plots of the saturation stress versus steady-state strain rate from shear tests: experimental results and Anand model predictions for (a) SAC-Bi, and (b) InnoLot Figure 6.2 Relations between inelastic strain and stress for (a) SAC-Bi, and (b) InnoLot: comparison between experimental results and Anand model fits at three strain rates for the temperature 250C (extraction from shear tests) Figure 6.3.Experimental and simulated stress-strain responses of InnoLot solder (extraction from tensile tests) Figure 6.4 Creep activation energy values of the InnoLot solder joints at different stress levels Figure 6.5 Stress exponent of the InnoLot solder joints at different temperatures Figure 6.6 Schematic of an IGBT power module Figure 6.7.Configuration of the IGBT module Figure 6.8 Finite element model for one-quarter of the IGBT module Figure 6.9 Thermal cycling profile considered in FE analysis Figure 6.10 Von Mises stress distribution in the bottom solder joint after cycles in the case of: (a) InnoLot and (b) SAC387 Figure 6.11 Evolution of the accumulated equivalent inelastic strain in the two types of solders during thermal cycling Figure 7.1.DIC technique for solder specimens xii List of Tables List of Tables Table 4.1 Chemical compositions of the solder alloys (mass %), and the solidus and liquidus temperatures Table 4.2 (a) The shear test matrix, (b) The creep test matrix Table 4.3 Uniaxial tensile test matrix Table 4.4 Cyclic Fatigue Testing Conditions Table 4.5 Aging Matrix for Tensile and Creep Tests Table 5.1.Cyclic fatigue matrix test Table 5.2.Material Properties for InnoLot, day aging at 1000C for two strain rates Table 5.3 Aging effects on material properties of InnoLot Table 6.1 Anand material parameters for several solder alloys Table 6.2 The discirption and unit of Anand parameters Table 6.3 The Anand model parameters determined for SAC-Bi and InnoLot lead-free solders Table 6.4 Dimensions of the components in the IGBT module Table 6.5 The elastic properties of all materials used in the model xiii List of Abbreviations List of Abbreviations EDM - Electrical Discharge Machining SEM - Scanning Electron Microscope EPMA - Electron Probe Micro-Analyze EDS - Energy-Dispersive Detector EDX - Energy-Dispersive X-ray spectroscopy WEEE - Waste Electrical and Electronic Equipment RoHS - Restriction of Hazardous Substances Directive EU - European Union Pb - Lead Sn - Tin Bi - Bismuth Ni - Nikel Sb - Antimony SAC - Sn-Ag-Cu PCB - Printed Circuit Board DCB - Direct Copper Bon UTS - Ultimate Tensile Stress E - Young’s modulus YS - Yield Stress CTE - Coefficient of Thermal Expansion IMC - Intermetallic Compound DIC - Digital Image Correlation IGBT - Insulated-Gate Bipolar Transistor FEM - Finite Element Method FEA - Finite Element Analysis AFM - Atomic-Force Microscopy LVDT - Linear Variable Differential Transformer DAQ - Data Acquisition ASTM - American Society for Testing and Materials BGA - Ball Grid Array xiv List of Publications List of Publications Q.B Tao, L Benabou, L Vivet, V.N Le and F Ben Ouezdou “Effect of Ni and Sb additions and testing conditions on the mechanical properties and microstructures of leadfree solder joints” Materials Science and Engineering: A, 669, 403-416; 2016 Q.B Tao, L Benabou, K.L Tan, J.M Morelle, V.N Le and F Ben Ouezdou “A design of a new miniature device for solder joints’ mechanical properties evaluation” Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science; 0954406216654728; 2016 Q.B Tao, L Benabou, V.N Le, H Hwang and D.B Luu “Viscoplastic characterization and Post-rupture microanalysis of a novel lead-free solder with small additions of Bi, Sb and Ni” Journal of Alloys and Compounds, 694, 892-904; 2016 Q.B Tao, L Benabou, K.L Tan, J.M Morelle and F Ben Ouezdou “Creep behavior of Innolot solder alloy using small lap-shear specimens” IEEE, 17th Electronics Packaging Technology Conference (EPTC), Singapore, Dec.; 2015 Q.B Tao, L Benabou, K.L Tan, J.M Morelle, L Chassagne and F Ben Ouezdou “Evaluation of the creep behavior of lead-free SnAgCuBiNi solder joints using in-situ micro-tensile testing” 13th International Conference on Creep and Fracture of Engineering Materials and Structures, Toulouse, Apr.; 2015 L Benabou and Q.B Tao “Approche multi-échelle de la rupture d'un alliage d'étain pour le brasage en ộlectronique de puissance AFM, Association Franỗaise de Mécanique; 2015 V.N Le, L Benabou, V Etgens and Q.B Tao “Micromechanical model for describing intergranular fatigue cracking in a lead-free solder alloy” Procedia Structural Intergrity 2, 2614-2622; 2016 V.N Le, L Benabou, V Etgens and Q.B Tao “Finite element analysis of the effect of process-induced voids on the fatigue lifetime of a lead-free solder joint under thermal cycling” Microelectronics Reliability In Press; 2016 V.N Le, L Benabou, V Etgens and Q.B Tao “Modeling of intergranular thermal fatigue cracking of a lead-free” International Journal of Solids and Structures In-Press, Accepted Manuscript; 12/2016 10 L Benabou and Q.B Tao “Development and first assessment of a DIC system for microtensile tester used for solder characterization” Experimental Techniques Under Revision; 11/2016 xv