纳米压痕法测定BGA焊球性能中的加载曲线研究

Research on loading curve of BGA solder balls by nanoindentation

BGA封装具有高集成、小型化和高可靠性的优点,被大量应用于微电子封装领域。PbSn和SAC305是常用的BGA焊球,其杨氏模量、硬度和屈服应力等力学性能参数对焊点和器件整体可靠性的评估至关重要。首先通过纳米压痕实验获得PbSn和SAC305焊球的载荷-位移曲线,采用Oliver-Pharr方法计算出两种焊球的杨氏模量和硬度;然后结合有限元分析与无量纲函数,反演出焊球的应力-应变曲线从而得到屈服应力;最后,提出衡量参数λ作为评价指标,对比研究了不同拟合方程对纳米压痕加载过程曲线的拟合效果。研究结果表明,方程P=C_(3)+C_(2)h+C_(1)h^(2)更适合用于拟合PbSn和SAC305焊球的加载曲线。

BGA packaging has advantages of high integration,miniaturization and high reliability,which is widely used in microelectronic packaging.PbSn and SAC305 are two commonly used BGA solder balls.Their mechanical properties such as Young's modulus,hardness and yield stress are significant for evaluating the reliability of solder joints and devices.Firstly,loaddisplacement curves of PbSn and SAC305 solder balls were obtained by nanoindentation experiments.Young's modulus and hardness of the two solder balls were calculated by Oliver-Pharr method.By combining finite-element-analysis with dimensionless function,solder balls'stress-strain curve was then inverted to obtain yield stress.Finally,a measurement parameterλwas proposed as an evaluation index,and the different fitting equations on nanoindentation curve loading process was compared.The results show the equation P=C_(3)+C_(2)h+C_(1)h^(2) is more suitable for fitting PbSn and SAC305 solder balls'loading curve.