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研究了倒装芯片中UBM制备和焊球回流工艺流程。通过改变阻挡层Ni和浸润层Cu的厚度,结合推拉力测试实验,探究了SnAgCu焊点剪切强度的变化规律。研究结果表明,UBM中阻挡层Ni对SnAgCu焊点的力学性能影响最大,而浸润层Cu厚度的增加也能提高SnAgCu焊点的力学性能。进一步对推拉力实验后的焊点形貌进行了SEM观察和EDS分析,得到了焊盘剥离、脆性断裂、焊球剥离、韧性断裂四种不同的焊点失效形式,代表着不同的回流质量,而回流质量主要由UBM的成分和厚度决定。研究结果为倒装焊工艺的优化提供了理论指导。
The preparation process of UBM in flip-chip and solder ball reflow process was studied. By changing the thickness of the barrier layer Ni and the wetting layer Cu, the variation of the shear strength of the SnAgCu solder joint was investigated in combination with the push-pull test. The results show that the barrier layer Ni in UBM has the strongest influence on the mechanical properties of SnAgCu solder joints, and the increase of the Cu thickness of the wetting layer can also improve the mechanical properties of SnAgCu solder joints. Furthermore, SEM observation and EDS analysis of solder joint morphology after push pull test were carried out. Four kinds of solder joint failure modes, including peel, brittle fracture, solder ball peel, and ductile fracture, were obtained, which represented different reflow quality, The quality of the reflow is mainly determined by the composition and thickness of the UBM. The results provide theoretical guidance for the optimization of flip-chip technology.