View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Repository@USM PROPERTIES OF LOW TEMPERATURE INDIUM-BASED TERNARY LEAD FREE SOLDERS SYSTEM MOHAMAD SALIMIN BIN JAHARI Universiti Sains Malaysia 2008 PROPERTIES OF LOW TEMPERATURE INDIUM-BASED TERNARY LEAD FREE SOLDERS SYSTEM by MOHAMAD SALIMIN BIN JAHARI Thesis submitted in fulfilment of the requirements for the degree of Master of Science August 2008 ACKNOWLEDGEMENT In the name of Allah, the most gracious and merciful. I would like to express my sincere appreciation to those who contributed to this research, without their cooperation it not been possible. It is not possible to write this thesis without being in a privileged research environment, which is continuously been provided by the School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia (USM). I would like to express a special gratitude to Intel Technology Sdn. Bhd. for their financial support under grant 2005-2007. First and foremost, I m glad to thank a lot of co-workers which have directly or indirectly contributed to this research. I want to acknowledge my high spirited supervisors En. Ahmad Badri Bin Ismail in the first place of his contributions to the successful of this research, as well as, the late Associate Prof. Dr. Luay Bakir Hussain Rahmatullah, my ex-supervisor for providing the knowledge base for my future. I would also like to thank all the staffs, especially Madam Fong, Mr. Rashid, Mr. Mokhtar, Mr. Azam, Mr. Shahrul Azmi, Mr. Farid, Mr. Helmi, Mr. Suhaimi, Mr. Kemuridan, Mrs. Harlina, Mrs. Mahani, Kak Intan, Kak Ana and Kak Milah for their technical support, as well as my postgraduate friends, Mohd Fadley, Umar Al- Amani, Mohd Syahril, Suriati, Hamisah, Zarina, Farhana, Napisah, Anuar, Mahathir, Erfan and Ervina who always available for discussions. A very special thank and deepest gratefulness to my parents Bonda Bedadari Karim & Ayahanda Jahari Bin Bujang and the whole family for their love and continued support. I express the utmost gratitude to all of them that deserve my thanks which have contributed toward the successful of this research and their name is not mention here. Thank you so much. ii TABLE OF CONTENTS Page Acknowledgement ii Table of Contents iii List of Tables vi List of Figures viii List of Abbreviations xi Abstrak xii Abstract xiii CHAPTER 1- INTRODUCTION 1.1 Overview 1 1.2 Statement of Problems 1 1.3 Objective of the Research 4 1.4 Research Approach 5 1.5 Research Schematic Diagram 6 CHAPTER 2- LITERATURE REVIEW 2.1 Background 7 2.1.1 Solder 8 2.1.2 Soldering Technology 9 2.1.2(a) Wave Soldering 12 2.1.2(b) Reflow Soldering 13 2.2 Lead Solder 14 2.2.1 Alternatives to lead 16 2.3 Lead Free Solder 17 2.3.1 Design for Environment 17 2.3.2 Solder Materials 18 2.4 Binary Alloys 22 2.4.1 Tin-Bismuth (Sn-Bi)Solder Alloy 22 2.4.2 Tin-Indium (Sn-In) Solder Alloy 23 2.4.3 Tin-Zinc (Sn-Zn) Solder Alloy 24 2.5 Ternary Alloys 25 2.5.1 Sn-Bi-Zn Alloy 25 2.5.2 Sn-In-Zn Alloy 26 2.5.3 Sn-Bi-In Alloy 28 2.6 Solder Alloys Properties 30 2.6.1 Melting Point 30 2.6.1(a) Low Melting Alloy 33 2.6.2 Wetting 35 2.6.2(a) Surface Tension 36 2.6.2(b) Wetting Force 37 iii 2.6.3 Tensile Test 38 2.6.4 Shear Test 38 2.7 Solder-Flux-Metal System 43 2.7.1 Solder-Substrate Interactions 43 2.8 Surface Mount Technology (SMT) 45 CHAPTER 3- METHODOLOGY 3.1 Introduction 49 3.2 Raw Materials 49 3.2.1 Copper substrate 49 3.2.2 Solder alloys 50 3.2.3 Flux 50 3.3 Material Characterization 51 3.3.1 X-Ray Diffraction 51 3.3.2 Microstructure Analysis 52 3.3.3 Density Test 53 3.4 Spreading Test Contact Angle Measurement 54 3.5 Wetting Balance Test 55 3.6 Mechanical Tests 56 3.6.1 Sample Preparation for Tensile Test and Shear Test 57 3.7 Differential Scanning Calorimetry (DSC) 58 3.8 Thermogravimetric (TGA) 58 3.9 Thermal Expansion 59 CHAPTER 4- RESULT AND DISCUSSION 4.1 Introduction 61 4.2 Characterization of solder alloys 61 4.2.1 X-Ray Diffraction (XRD) analysis 61 4.2.2 Microstructure Analysis 65 4.2.2(a) Solder Sample of 18.6Sn-57.2Bi-24.8In 65 4.2.2(b) Solder Sample of 17.5Sn-43.2Bi-39.3In 68 4.2.2(c) Solder Sample of 15.6Sn-36.1Bi-48.3In 71 4.2.2(d) Solder Sample of 44.2Sn-53.7Bi-2.1Zn 72 4.2.2(e) Solder Sample of 83.8Sn-10.1In-6.2Zn 74 4.3 Wettability Test 75 iv 4.3.1 Surface Tension 80 4.3.2 Spreading Test 80 4.4 Mechanical Properties 84 4.4.1 Tensile Test 84 4.4.2 Shear Test 89 4.5 Physical Properties 94 4.5.1 Density 94 4.5.2 Differential Scanning Calorimetry (DSC) 95 4.5.3 Thermal Expansion 98 CHAPTER 5- CONCLUSION AND RECOMMENDATION FOR FUTURE RESEARCH 5.1 Conclusion 102 5.2 Recommendation for Future Research 103 References Appendices Appendix 1 Appendix 2 v LIST OF TABLES Page Table 2.1 Available low melting alloys 32 Table 2.2 Calculated and experimentally observed invariant reactions 33 for the systems Sn-Bi-In, Sn-Bi-Zn, and Sn-In-Zn. Table 2.3 Lead-free solder alloys melting below 180°C 34 Table 2.4 Tensile Properties of Lead-Free Solders 39 Table 2.5 Shear Properties of Solder Alloys 42 Table 3.1 Alloys system used in the research 50 Table 3.2 Cold Mounting Parameters 52 Table 4.1 EDX result for sample 57.2Bi-24.8In-18.6Sn 66 Table 4.2 EDX result at area 1 for sample 57.2Bi-24.8In-18.6Sn 67 Table 4.3 EDX result at area 2 for sample 57.2Bi-24.8In-18.6Sn 67 Table 4.4 EDX result at area 3 for sample 57.2Bi-24.8In-18.6Sn 68 Table 4.5 EDX result for sample 43.2Bi-39.3In-17.5Sn 69 Table 4.6 EDX result at area 4 for sample 43.2Bi-39.3In-17.5Sn 70 Table 4.7 EDX result at area 5 for sample 43.2Bi-39.3In-17.5Sn 71 Table 4.8 EDX result at area 6 for sample 48.3In -36.1Bi-15.6Sn 72 Table 4.9 EDX result for sample 53.7Bi-44.2Sn-2.1Zn 73 Table 4.10 EDX result for sample 83.8Sn-10.1In-6.2Zn 75 Table 4.11 Comparison of wettability characteristic among solder alloys 77 for immersion temperature 260oC. Table 4.12 Surface tension for solder alloys 80 Table 4.13 Contact angle for different solder alloys 81 Table 4.14 Spreading Ratio 82 Table 4.15 Contact angle category 82 vi Table 4.16 Tensile strength 84 Table 4.17 Shear strength 89 Table 4.18 Density result for solder alloys 94 Table 4.19 DSC result 95 Table 4.20 Thermal Expansion Coefficient 99 Table 4.21 Coefficient of thermal expansion for Sn-37Pb eutectic solder 99 Table 4.22 Typical CTE-values of materials used in PCBs 100 vii LIST OF FIGURES Page Figure 2.1 Reels of solder 9 Figure 2.2 Tin-lead eutectic diagram 14 Figure 2.3 A coil of lead-free solder wire 18 Figure 2.4 Tin-Bismuth Phase Diagram 23 Figure 2.5 Tin-Zinc Phase Diagram 24 Figure 2.6 Bismuth-Zinc phase diagram 26 Figure 2.7 Calculated liquidus projection of ternary Sn-In-Zn system. PI 27 and P2 are ternary peritectic points and El, a ternary eutectic point. Figure 2.8 Calculated vertical sections of Sn-In-Zn system along 28 constant In contents at 0, 2, 5 and 10 wt%. Figure 2.9 Calculated liquidus of the Sn-Bi-In system 29 Figure 2.10 Liquidus of the Sn-Bi-In system (Kabassis et. al 1984,1986; 30 Stel makh et al 1972; Ruggiero and Rutter 1995) Figure 2.11 Contact angle 35 Figure 2.12 Wetting occurs when molten solder penetrates a copper 36 surface, forming an intermetallic bond. Figure 2.13 Results of shear strength tests 38 Figure 3.1 Microstructure analysis (a) Scanning Electron Microscope 53 (SEM) (VPFESEM) Supra 35VP (b) epoxy and hardener Figure 3.2 Solder Checker machine and spreading test sample. 55 Figure 3.3 Wetting Balance Test 56 Figure 3.4 Instron Machine for mechanical testing 57 Figure 3.5 Sample for mechanical testing(a)Sample for tensile test 58 (b) Sample for shear test Figure 3.6 Dilatometer 59 Figure 4.1 XRD analysis for alloy 57.2Bi-24.8In-18.6Sn (a) 62 intermetallic compound Bismuth-Indium (b) Bismuth (c) Tin viii Figure 4.2 XRD analysis for alloy 43.2Bi-39.3In-17.5Sn - peak match 63 with intermetallic compound Bismuth-Indium. Figure 4.3 XRD patterns for solder alloy 48.3In -36.1Bi-15.6Sn 64 Figure 4.4. XRD patterns for solder alloy 53.7Bi-44.2Sn-2.1Zn (a) 64 Bismuth, (b) Tin Figure 4.5 XRD patterns for solder alloy 83.8Sn-10.1In-6.2Zn. 65 Figure 4.6 SEM micrograph for sample 57.2Bi-24.8In-18.6Sn 66 Figure 4.7 Spectrum of EDX analysis for the whole area of sample 66 57.2Bi-24.8In-18.6Sn Figure 4.8 Spectrum of EDX analysis at area 1 for sample 57.2Bi- 67 24.8In-18.6Sn Figure 4.9 Spectrum of EDX analysis at area 2 for sample 57.2Bi- 67 24.8In-18.6Sn Figure 4.10 Spectrum of EDX analysis at area 3 for sample 57.2Bi- 68 24.8In-18.6Sn Figure 4.11 SEM micrograph for sample 43.2Bi-39.3In-17.5Sn 69 Figure 4.12 Spectrum of EDX analysis for the whole area of sample 69 43.2Bi-39.3In-17.5Sn Figure 4.13 Spectrum of EDX analysis at area 4 for sample 43.2Bi- 70 39.3In- 17.5Sn Figure 4.14 Spectrum of EDX analysis at area 5 for sample 43.2Bi- 70 39.3In- 17.5Sn Figure 4.15 SEM micrograph for sample 48.3In-36.1Bi-15.6Sn 71 Figure 4.16 Spectrum of EDX analysis at area 6 for sample 48.3In- 72 36.1Bi-15.6Sn Figure 4.17 SEM micrograph for sample 53.7Bi-44.2Sn-2.1Zn 73 Figure 4.18 Spectrum of EDX analysis for the whole area of sample 73 53.7Bi-44.2Sn-2.1Zn Figure 4.19 SEM micrograph for sample 83.8Sn-10.1In-6.2Zn 74 Figure 4.20 Spectrum of EDX analysis for the whole area of sample 75 83.8Sn-10.1In-6.2Zn Figure 4.21 Typical wetting curve 76 ix Figure 4.22 EMPA line analysis across solder/Cu interface: (a) Sn-3Zn- 78 6Bi/Cu, (b) Sn-9XZn-6Bi/Cu and (c) Sn-12Zn-6Bi/Cu Figure 4.23 Maximum wetting force for lead free solder from wettability 78 test.