基于焊点形态的工艺参数对底部引线塑料封装器件焊点可靠性影响分析

选取焊盘长度、焊盘宽度、钢网厚度和间隙高度为四个关键因素,采用水平正交表L25(56)设计25种不同参数水平组合的底部引线塑料封装(bottom leaded plastic,BLP)器件焊点,建立25种焊点的形态预测模型和有限元分析模型;对热循环加载条件下BLP焊点进行非线性有限元分析,计算25种不同焊点形态的BLP焊点热疲劳寿命;基于热疲劳寿命计算结果进行极差分析.结果表明,四个因素对BLP焊点热疲劳寿命影响由大到小的顺序依次是焊盘宽度、焊盘长度、间隙高度和钢网厚度;可靠性最高的BLP焊点工艺参数水平组合为焊盘长度1.1 mm、焊盘宽度0.65 mm、钢网厚度0.15 mm和间隙高度0.09 mm.

STUDY ON THE IMPACT OF PROCESS PARAMETERS ON SOLDER JOINT RELIABILITY OF BOTTOM LEADED PLASTIC COMPONENT BASED ON SOLDER JOINT SHAPE

The pad length,the pad width,the stencil thickness and the stand-off were selected as four control factors.By using an L25(56) orthogonal array the BLP solder joints which have 25 different process parameters' levels combinations were designed.The numerical models of all the 25 BLP(bottom leaded plastic) solder joints were developed using the Surface Evolver.Utilizing the nodes coordinate exported from the 25 BLP solder joints numerical models,the finite element analysis models were set up and then the nonlinear finite element analysis(FEA) of the BLP solder joints under thermal cycles were performed by using ANSYS.The thermal fatigue life of BLP solder joint was calculated using Manson-Coffin equation.Based on the calculated thermal fatigue life results,the range analysis was performed.The results of study show that the impact sequence of the four factors from high to low on the fatigue life of BLP solder joints are the pad width,the pad length,the stand-off and the stencil thickness;the best level combination of process parameters that results in the longest fatigue life is the stand-off of 0.07 mm,the stencil thickness of 0.125 mm,the ball diameter of 0.85 mm and the pad diameter of 0.89 mm.