Research on Thermal Meromechanics of Electronic Packaging

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Solder joints provide both electrical interconnection and mnechanical support. Therefore, the structural integrity of solder joints is a very inportant reliability concern. Especially, the fatigue resistance of near eutectic Pb-Sn solders is a major concern in the development of surface mount technology. Solder alloys, such as Pb-Sn solders are commonly used as high temperature. The solder alloys show strongly time dependent deformation, such as creep and strain rate effect in the high temperature regimes. Then, structural analysis and the estimation of strength of isothermal fatigue life demand a detail experimental observation and theoretical research on the viscous deformation of the solder alloy. In this research, the experimental and theoretical observation on fatigue, crack propagation and damage from both the macro and micro point of view. As a result, the following conclusions are obtained :(1) The stress-strain relation and yield sufaces of Pb-Sn solder alloy have strong strain rate effect and temperature effect.(2) The relationship between the number of cycle to fatigue failure and the plastic strain energy density can be expressed by a formula.(3) The constitutive model incorporating the creep effect was constructed in order to consider the change of microstructure of the solder alloy.(4) Using the constitutive model and the formula of the result (2), the method to estimate number of cycle to fatigue failure.(5) The possibility to construct more reliable method for the estimation of fatigue failure was found out, with more accuracy considering of microstructural change of the solder alloy in the constitutive model.