基于内聚力模型法PBGA封装焊点/IMC界面的分层开裂研究

塑料球栅阵列封装PBGA的可靠性分析中，考虑封装过程中SnAgCu焊料与铜焊盘界面间产生的金属间化合物（Intermetallic compound，IMC）的影响，并引入内聚力模型（Cohesive zone model, CZM），利用ANSYS对热循环作用下焊点/IMC界面的脱层开裂情况进行研究。结果表明：热循环作用下，在封装器件中焊点承受较大的应力应变，且远离中心的外侧焊点具有比内侧焊点更大的应力应变。IMC的存在极大的降低了焊点的可靠性。界面分层最先发生在最外侧的IMC/焊点界面的两端，随着热循环次数的增加，分层逐渐沿着界面两端向里扩展。在热循环的前几个阶段，各个界面的最大损伤值增大较快，随着热循环的继续加载，界面最大损伤值逐渐趋于稳定。整个过程中四号焊点界面的损伤值始终最大。

STUDY ON SOLDER/IMC INTERFACE DELAMINATION OF PBGA BASED ON CZM METHOD

In the reliability analysis of PBGA, Cohesive zone model (CZM) was introduced to study the interface delamination crack between solder and IMC of PBGA under thermal cycling through ANSYS software. The simulation considered the influence of Intermetallic compounds (IMC) which produced between the interface of SnAgCu solder and copper in the process of encapsulation. The results show that the solders of electronic packages under the higher stress and strain in the thermal cycling, and the outside of solders which far from the center under bigger stress and strain than the inside ones. The existence of IMC greatly reduced the reliability of solder. Interface delamination crack occurred at two ends of the interface between IMC and solder in the outside of the solder joints, and gradually extended to the interior with the increase of cycles. In front phases of the thermal cycles, the maximum damage on each interface increased quickly, and tended to be stable gradually with the increase of cycles. The damage of interface of the NO.4 solder is always the biggest in the whole process.