Abstract
Sn/ENIG has recently been used in flexible interconnects to form a more stable micron-sized metallurgical joint,due to high power capability which causes solder joints to heat up to 200 ℃.However,Cu6Sn5 which is critical for a microelectronic interconnection,will go through a phase transition at temperatures between 186 and 189 ℃.This research conducted an in-situ TEM study of a micro Cu/ENIG/Sn solder joint under isothermal aging test and proposed a model to illustrate the mechanism of the microstructural evolution.The results showed that part of the Sn solder reacted with Cu diffused from the electrode to form η'-Cu6Sn5 during the ultrasonic bonding process,while the rest of Sn was left and enriched in a region in the solder joint.But the enriched Sn quickly diffused to both sides when the temperature reached 100 ℃,reacting with the ENIG coating and Cu to form(NixCu1-x)3Sn4,AuSn4,and Cu6Sn5 IMCs.After entering the heat preservation process,the diffusion of Cu from the electrode to the joint became more intense,resulting in the formation of Cu3Sn.The scallop-type Cu6Sn5 and the seahorse-type Cu3Sn constituted a typical two-layered structure in the solder joint.Most importantly,the transition between η and η'was captured near the phase transition temperature for Cu6Sn5 during both the heating and cooling process,which was accompanied by a volume shifting,and the transition process was further studied.This research is expected to serve as a reference for the service of micro Cu/ENIG/Sn solder joints in the electronic industry.
基金项目
opening fund of National Key Research and Development Program of China(2020YFE0205300)
Key Laboratory of Science and Technology on Silicon Devices,Chinese Academy of Sciences(KLSDTJJ2022-5)
Chongqing Natural Science Foundation of China(cstc2021jcyjmsxmX1002)
中央高校基本科研业务费专项(AUGA5710051221)
NETL
NSTL
万方数据