热循环载荷下BGA封装体热应力特性

Thermal stress for BGA products under thermal cycle load

中文关键词: 电子器件  有限元  BGA  热应力

英文关键词: electronic device  finite element  BGA  thermal stress

中文摘要:

      构建了热循环条件下球栅阵列（BGA）封装体传热和应力耦合的非稳态理论模型，通过器件自身发热功率随时间变化来实现循环热载荷，研究工作过程中流场、温度场、应力场的动态变化，并采用有限元方法进行数值求解，分析了热循环载荷对器件所处物理场的影响。研究结果表明，热循环过程中，器件整体温度与方腔内自然对流强度在高温保温时间开始时刻出现峰值，在低温保温时间结束时刻出现谷值；BGA封装体最高温点均位于作为热源的芯片上，承受应力最大点位于阵列最外拐点与上下侧材料的连接部位；随着循环次数的增加，每个热循环周期中关键焊点上端点处的最大等效应力不断增加。

英文摘要:

      An unsteady coupled model of heat transfer and thermal stress for BGA products under thermal cycle load is developed to verify the dynamic performance of flow field, thermal field and stress field. The model is numerically analyzed by finite element method to study how the physical fields affected by thermal load, which takes the time-dependency of power as thermal cycle. The results indicate that, under thermal cycle load, the highest overall temperature of the device and the strongest natural convection intensity in the cavity are reached at the beginning of the high temperature heat preservation period, and the lowest temperature and weakest intensity appears at the end of the low temperature heat preservation period. The point with the highest temperature among thermal load period always locates in the chip, which is considered as the heat source in this model, and the point with the maximum stress lies in the juncture between chip and the outermost solder joint of BGA. As the number of cycles increases, the maximum equivalent stress at the edge of the critical solder joint in each thermal cycle is increasing.