The Interface Microstructure and Shear Strength of Sn2.5Ag0.7Cu0.1RExNi/Cu Solder Joints under Thermal-Cycle Loading

Metals

Baojin Shi¹  Di Zhao²  Chao Zhang²  Keke Zhang²  Mengmeng Sun²  Congcong Cao²  Huigai Wang² 

[1] Institute of China Shipbuilding 725 Industry, Luoyang 471023, China;School of Materials Science and Engineering, Henan University of Science and Technology, Henan Province Key Laboratory of Nonferrous Metal Material Science and Processing Technology, Luoyang 471023, China;

关键词: Sn2.5Ag0.7Cu0.1RExNi lead-free solder;    solder joint;    thermal-cycle loading;    intermetallic compounds;    shear strength;   

DOI  :  10.3390/met9050518

来源: DOAJ

【 摘 要 】

The interface microstructure and shear strength of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints under thermal-cycle loading were investigated with scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and physical and chemical tests. The results show that an intermetallic compound (IMC) layer of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints evolved gradually from the scalloped into larger wavy forms with increasing number of thermal cycles. The roughness and average thickness of IMC increased with thermal-cycle loading. However, at longer thermal-cycle loading, the shear strength of the joints was reduced by about 40%. The fracture pathway of solder joints was initiated in the solder seam with ductile fracture mechanism and propagated to the solder seam/IMC layer with ductile-brittle mixed-type fracture mechanism, when the number of thermal cycles increased from 100 to 500 cycles. By adding 0.05 wt.% Ni, the growth of the joint interface IMC could be controlled, and the roughness and average thickness of the interfacial IMC layer reduced. As a result, the shear strength of joints is higher than those without Ni. When compared to joint without Ni, the roughness and average thickness of 0.05 wt.% Ni solder joint interface IMC layer reached the minimum after 500 thermal cycles. The shear strength of that joint was reduced to a minimum of 36.4% of the initial state, to a value of 18.2 MPa.

【 授权许可】

Unknown