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Nanocrystals 3835 3.1. Progress in Mn 2 O 3 Nanomaterials 3835 3.2. Synthesis of Mn 2 O 3 Nanocrystals 3836 3.2.1. Method 3836 3.2.2. Instrumental Analysis 3836 3.3. Grain Growth Kinetics of Mn 2 O 3 Nanocrystals 3836 3.3.1. Kinetic Analysis 3836 3.3.2. Microstructure Analysis 3838 3.4. Spectral Properties of Mn 2 O 3 Nanocrystals 3839 3.4.1. Raman Features of Different Grain Sizes 3839 3.4.2. IR Features of Different Grain Sizes 3840 3.4.3. XPS Analysis of Different Grain Sizes 3841 3.4.4. ESR Analysis of Different Grain Sizes 3843 4. Controllable Synthesis and Microstructure Evolution of Mn 3 O 4 Nanocrystals 3844 4.1. Progress in Mn 3 O 4 Nanomaterials 3844 4.2. Shape-Controlled Synthesis of Mn 3 O 4 Nanocrystals 3845 4.2.1. Synthesis Techniques 3845 4.2.2. Instrumental Analysis 3845 4.3. Microstructure Evolution of Single-Crystal Mn 3 O 4 Nanocrystals 3845 4.3.1. Mn 3 O 4 Nanoparticles 3845 4.3.2. Mn 3 O 4 Nanorods 3846 4.3.3. Mn 3 O 4 Nanofractals 3846 4.3.4. HRTEM Investigation of Mn 3 O 4 Nanocrystals 3847 4.3.5. Spectral Characteristics of Mn 3 O 4 Nanocrystals 3847 4.3.6. Formation Mechanism of Mn 3 O 4 Nanocrystals 3849 5. Summary and Outlook 3849 5.1. Summary 3849 5.2. Outlook 3850 5.3. Concluding Remarks 3850 Author Information 3850 Corresponding Author 3850 Notes 3850 Biographies 3850 Acknowledgments 3852 List of Abbreviations 3852 References 3852

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Orthorhombic phase SnO2 is a material with unknown optical, electrical, and gas-sensing properties. It was found previously only at high pressures and temperatures. A facile strategy for the synthesis of orthorhombic SnO2 is of fundamental importance. Using pulsed-laser deposition, the authors report a kind of experimental realization of a pure orthorhombic SnO2 thin film under low pressure and temperature that are much lower than those of traditional methods. The optical properties of an orthorhombic SnO2 thin film were measured by spectrophotometric transmittance. The oxygen exchange reaction mechanism at the grain interfaces was proposed to explain the formation and optical properties of this orthorhombic phase.

The near-eutectic Sn-3.5 wt.% Ag-0.7 wt.% Cu (Sn-3.5Ag-0.7Cu) alloy was doped with rare earth (RE) elements of primarily Ce and La of 0.05-0.25 wt.% to form Sn-3.5Ag-0.7Cu-xRE solder alloys. The aim of this research was to investigate the effect of the addition of RE elements on the microstructure and solderability of this alloy. Sn-3.5Ag-0.7Cu-xRE solders were soldered on copper coupons. The thickness of the intermetallic layer (IML) formed between the solder and Cu substrate just after soldering, as well as after thermal aging at 170°C up to 1000 h, was investigated. It was found that, due to the addition of the RE elements, the size of the Sn grains was reduced. In particular, the addition of 0.1wt.%RE to the Sn-3.5Ag-0.7Cu solder improved the wetting behavior. Besides, the IML growth during thermal aging was inhibited.

The effect of Cu-Sn intermetallic compounds (IMC) on the fatigue failure of solder joint during thermal cycling has been studied. The samples consist of components [leadless ceramic chip carrier (LCCC)] soldered onto FR-4 printed circuit board (PCB), and are prepared by conventional reflow soldering using a 63Sn-37Pb solder paste. The specimens are subjected to thermal cycling between 035 C and 125 C with a frequency of two cycles per hour until failure. The results indicate that the fatigue lifetime of the solder joints depends on the thickness of IMC's layer between Cu-pad and bulk solder, and the relation of the lifetime to the thickness can be described as a monotonically decreasing curve. The lifetime is very sensitive to the thickness of the IMC when the thickness is less than 1.4 m. During thermal cycling, the thickness of the IMC layer increases and then the interface between IMC and solder becomes gradually flatter. The results of X-ray diffraction and scanning electron microscope (SEM) analysis show that cracks propagate along the interface between the IMC layer and the solder joint. The Cu3Sn ("-phase) is also found to form between the Cu-pad and-phase during thermal cycling. On the basis of the above results, the thick and flattened IMC layer is shown to responsible for the fatigue failure of solder joint during thermal cycling. The results of this paper can be used to optimize the reflow soldering process for the fabrication of robust solder joints.

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