摘要
利用SEM,TEM,XRD分析了共晶SnBi/Cu焊点经120℃时效7 d后界面组织结构的变化.焊点界面处金属间化合物厚度由原来初始态的约2 μm增至时效态的10 μm,并且化合物也由原来单一的Cu6Sn5转变为Cu6Sn5和Cu3Sn 相.进一步研究表明,在Cu3Sn与Cu之间界面处偏析了大量尺寸约100 nm的Bi颗粒.双缺口试样的断裂韧性实验表明, 热时效促使焊点断裂韧性快速下降,同时该焊点的断口也由原来初始态的韧性断裂转变为时效后Cu3Sn与Cu界面处的脆性断裂,脆性断裂后一侧断口为鲜亮的Cu表面.在TEM下,通过与220℃/5 d时效态纯Sn/Cu焊点相同界面的比较,可以断定引起该焊点失效的原因是Bi颗粒在此界面处的偏析.含Bi无Pb焊料由于Bi在界面析出而引发的脆断将会是微电子器件长期使用中的一个潜在危害.
The interracial microstructure of eutectic SnBi/Cu interconnect was examined by SEM, TEM and XRD. It was found that after aging at 120 ℃ for 7 d, the intermetallic compound （IMC） at the interface evolved from Cu6Sn5 to Cu6Sn5 plus Cu3Sn and the thickness of IMC layer increased from 2 μm to 10 μm. TEM observation revealed a number of Bi particles with size of about 100 nm distributed along the Cu3Sn/Cu interface in the aged interconnect. Micro-force testing of interconnects indicated that upon aging, the fracture toughness KIC of the interconnect decreased greatly and fracture mode changed from ductile to brittle. While the crack path was along the interface between IMC and solder in the as-reflowed condition, it was shifted to the interface between Cu3Sn and Cu substrate after aging. By comparing with the same interface in the pure Sn/Cu interconnect agedat 220 ℃ for 5 d, it was concluded that the presence of Bi particles is responsible for the embrittlement of the interface. The Bi-induced embrittlement presents a serious concern over the suitability of Bicontaining Pb-free solders for microelectronic packaging.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2005年第8期847-852,共6页
Acta Metallurgica Sinica
基金
国家自然科学基金项目50228101国家重点基础研究规划项目2004CB619306资助
关键词
共晶SnBi/Cu焊点
偏析
界面反应
无铅焊料
eutectic SnBi/Cu solder joint, segregation, interfacial reaction, Pb-free solder
