Sn/Pb共晶はんだの熱サイクル負荷による相成長過程の評価

概要

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Thermal fatigue damage of solder joint is considered to be closely related to microstructural coarsening. In the present study, phase growth model is devised in order to express the microstructural evolution of Sn/Pb eutectic sobder. The model is based on results of systematic microstructural abservation using lap joint type shear specimen proposed by the authors. And the model is also derived from the vacancy diffusion theory in phase boundary. The phase growth is characterized by parameter S which is defined as average phase size to the 4 th power d^4 and increases approximately proportional to time and total equivalent creep strain. Furthermore, the model is applied to evaluation of phase growth process in the solder joint of the specimen under thermal cyclic loading which realizes approximately thermal deformation state of printed circuit board (PCB). Consequently, it is clarified that phase growth proceeds at any temperature to which PCB is subjected and is mainly induced by strain rather than thermal equilibrium. And parameter S increases corresponding to total equivalent creep strain. This suggests that S would be evaluation parameter for thermal fatigue damage of actual solder joint.
一般社団法人日本機械学会の論文
1999-12-25