Abstract: Under the trend of miniaturization of microelectronic devices, the serving environment of solder joints becomes severer, which requires a higher reliability of materials. To ensure the reliability of micro-size solder joint, materials including Fe-Ni, Fe-Ni-P, and Ni-Co-P alloy which have strong diffusion barrier ability are introduced as novel under bump metallizations (UBMs). On the other hand, the effect of minor element on mechanical properties, wettability and interfacial IMC growth of solder material are widely researched in order to develop novel solder materials. At the same time, the analytical techniques for reliability research develop rapidly. Non-destructive techniques like three dimensional X-ray microscopy (3D-XRM) and Scanning acoustic microscopy (SAM) are widely used to characterize interface and locate the failures. Transmission electron microscopy (TEM), electron probe micro-analysis (EPMA) and electron back-scattered diffraction (EBSD) technology are used in the nano-scale characterization and phase identification. With the development of analytical ability, the failure behaviour and lifetime model under single field of high temperature, thermal cycling, mechanical stress and current are studied thoroughly. Further, since the condition of multi-field is more close to the real working condition, the failure behaviour and failure mechanisms of multi-field reliability are highly concerned.