| Co-Investigator(Kenkyū-buntansha) |
SHIBUTANI Tadahiro Yokohama National University, Faculty of Engineering, Research Associate, 大学院・工学研究院, 助手 (10332644)
YU Qiang Yokohama National University, Faculty of Engineering, Assistant Professor, 大学院・工学研究院, 助教授 (80242379)
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| Research Abstract |
In this report, mechanical reliability problems, which must be solved before lead-free solder can be used in practical applications, are examined using analytical and experimental methods. This report consists of seven chapters. The contents of each chapter are as follows. Chapter 1 describes the current surface mount technology of electron devices, the reliability assessment method of surface mounted components, and the necessity and problems of lead-free solder applications. Chapter 2 shows the relationship between reflow condition and the fatigue strength of a solder joint. In Chapter 3, the difference of fracture modes in each lead-free solder joint is noted. Also, the effect of the growth of the intermetallic compound layer and the material properties of solder on the fracture mode of a solder joint are shown using analytical and experimental methods. In Chapter 4, the interface strength of the Sn-Zn system solder joint, which is attracting attention as a low-temperature lead-free
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solder, is analyzed and a technique to improve reliability is proposed. Chapter 5 shows the relationship between the formation of voids and fatigue strength of solder joints using FEM analysis and mechanical shear fatigue tests of CSP joints.
In Chapter 6, the hardening characteristics of lead-free solder are examined using mechanical shear fatigue testing. Also, the effect of the hardening rule and creep law on the estimation of stress and nonlinear strain for lead-free solder joints is examined and an elastic-plastic-creep analysis method is proposed, which shows good convergence and high precision. Finally, Chapter 7 presents the conclusions gained from the preceding chapters.
Through this study, mechanical reliability problems such as the decrease of interface strength, formation of voids, and the application of a constitutive equation, all of which have become very important in practical applications of lead-free solder, are shown and solutions for these problems are proposed. As the results of this study, it is possible to improve the reliability of lead-free solder joints and the efficiency of reliability evaluations as well as to reduce production costs. Less
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