BGA焊点剪切性能的评价

Evaluation on the Shear Properties of BGA Solder Joint

设计了用单个微焊球和两块带焊盘的FR4板焊接而成的搭接接头,研究了不同稀土含量及不同加载速率对接头强度及塑性的影响。结果表明,微量稀土(质量分数<0.25%)不但能提高焊点的剪切强度,而且可以改善焊点的塑性。而当稀土含量进一步增加时,焊点的强度及塑性均下降。焊点的剪切强度及伸长量随应变速率的增加而增加。通过对焊点显微组织的分析可知,微量稀土可显著细化焊点的显微组织,特别是抑制了钎料内部及界面处金属间化合物的生长,从而改善了焊点的力学性能。对断口形貌的分析同样证明了伸长量随剪切速率增加而增加。

In this paper, soldered lap joint specimens were fabricated by a solder reflow process using a Sn-3.8Ag-0.7Cu-xRE （x=0. 0.1wt%, 0.25wt%, 0.5wt%） BGA solder ball on FR4 substrate parts. The effects of rare earth（RE） content and strain rate on the shear properties of soldered lap joint were investigated. The Results show that the addition of minute RE （〈0.25wt%） can improve the shear strength and elongation of the lap joint. However, further increasing of RE content would degrade the shear properties of the lap joint. The shear strength and elongation of the lap joint increase with the increase of strain rate. The analysis of the microstructure and fractograph indicated that through the addition of minute RE, the microstructure of the lap joint was refined, especially the growth of intermetallic compound was inhibited, and thus the shear properties of the lap joint were improved. In addition, the observation of fractographs confirmed that the elongation of the lap joint increase with the increase of strain rate.