无铅封装中镀覆层对PBGA耐湿热可靠性的影响

Reliability analysis of PBGA devices with different finishes under hygrothermal environment in lead-free electronics package

随着电子产业中无铅替代有铅的迫切要求,无铅产品的应用越来越广泛,多种材料在无铅电子封装中的应用,使得界面反应与含铅产品相比更为复杂。通过对PBGA器件与不同表面镀层(OSP,ENIG)的PCB板互连形成的SnAgCu焊点,在高湿和炎热条件下的可靠性进行研究。试验结果表明:焊点的寿命在使用ENIG镀层时比使用OSP镀层时更长,说明焊点的可靠性与界面金属间化合物类型密切相关;试验后期还发现器件本身最易产生裂纹的地方位于芯片(DIE)、粘接层材料(DA)和塑封材料(EMC)交界处的芯片以及芯片和DA材料交界处的芯片上,主要是因为芯片与聚合物材料间不能形成过渡层,芯片应力无法得到松弛。

With the urgent request of the lead-free alternative lead in electronic industry, lead-free products are more and more widely used, and various materials are being used in lead-free electronics packaging application. Compared with the lead-based products, the interfaeial reaction become more complex. The reliability of SnAgCu solder between PBGA and PCB with different finishes（OSP,ENIG） under humidity temperature circulation were investigated. The results showed that： The solder with ENIG finishes presented a better reliability performance than OSP finishes; the results revealed that the reliability of the solder was influenced by the interface intermetallic types; the testing also revealed that the crack was mainly appearance at the interface between the chip, DA and Epoxy Molding Compound （EMC） material, and between the Die-Attach （DA） material and the chip also had a great damage. The main reason was that the transition layers could not form between the chip and polymer materials, so the stress on the chip could not get relaxed.