소성변형률 이론에 기초를 둔 파손확률모델을 이용한 솔더 조인트의 건전성 평가

초록

Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and solder joint’s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. Various plastic-strain rated based models such as Coffin-Manson Fatigue Model, Total Strain Fatigue Model(Coffin-Manson-Basquin), and Solomon Fatigue Model are utilized in this study. The effects of random variables such as CTE, distance of the solder joint from the neutral point(DNP), temperature variation and height of solder on the failure probability of the solder joint are systematically investigated by using a failure probability model with first order reliability method(FORM).