β-Sn晶粒取向及温度对Cu/SAC305/Cu微焊点时效界面反应的影响

Effects ofβ-Sn grain orientation and temperature on the interfacial reaction in Cu/SAC305/Cu micro solder joints during aging

为了探究不同等温时效温度下β-Sn晶粒取向及晶界特征对界面反应的影响,采用准原位观测手段对不同Sn取向的Cu/Sn3.0Ag0.5Cu/Cu(Cu/SAC305/Cu)微焊点进行研究.结果表明,在不同温度下时效时,微焊点两侧界面IMC(Cu_(6)Sn_(5)+Cu_(3)Sn两相)自始至终呈现对称性生长,表明时效过程中β-Sn晶粒取向及晶界的存在不会影响界面反应.但是随着时效温度的升高,界面IMC的形貌和厚度发生明显变化.在100℃时效后,界面处生成扇贝状的Cu_(6)Sn_(5)和较薄的不连续的Cu_(3)Sn层;在125℃时效后,界面处生成扇贝状的Cu_(6)Sn_(5)和较薄的连续的Cu_(3)Sn层;而在150℃时效后,界面IMC由层状Cu_(6)Sn_(5)和层状Cu3Sn双层结构组成.时效温度的升高促使Cu和Sn原子扩散加快,促进了扇贝状Cu_(6)Sn_(5)向层状转变并造成Cu3Sn的快速生长.同时,基于界面IMC厚度随时效时间的演变规律,获得了不同时效温度下微焊点界面IMC生长曲线,可为Sn基微焊点的可靠性评价提供依据.

Quasi-in-situ method was carried out to study the effects ofβ-Sn grain orientation and grain boundary feature on the growth behavior of interfacial intermetallic compounds(IMCs)in Cu/Sn3.0Ag0.5 Cu/Cu(Cu/SAC305/Cu)micro solder joints under different aging temperatures.The results showed that the IMCs containing Cu_(6)Sn_(5)+Cu_(3)Sn phases at both interfaces of the micro solder joints grew symmetrically under all the aging conditions,proving thatβ-Sn grain orientation and grain boundary played no obvious effect on the interfacial IMCs growth either between the two interfaces of a same joint or those from different joints.While with increasing aging temperature,the morphology and thickness of the interfacial IMCs were changing apparently.Scallop-type Cu_(6)Sn_(5)and thin discontinuous Cu_(3)Sn formed at the interfaces after aging at100℃;scallop-type Cu_(6)Sn_(5)and thin continuous Cu_(3)Sn formed at the interfaces after aging at 125℃and bilayer structured IMCs containing Cu_(6)Sn_(5)and Cu_(3)Sn formed at the interfaces after aging at 150℃.The increasing aging temperature accelerated the diffusion of Cu and Sn atoms,which could promote the transition of Cu_(6)Sn_(5)from scallop to layer and the rapid growth of Cu_(3)Sn.Finally,based on the variation of interfacial IMCs thickness with aging time,the growth curves of the interfacial IMCs layers under different aging conditions were obtained which may be helpful for reliability assessment of Snbased micro solder joints.