Properties of SnAgCu/SnAgCuCe soldered joints for electronic packaging

Abstract

For quad flat packages (QFP256), lead-free soldered joints reliability in service is a critical issue. In this paper, soldering experiments of quad flat package (QFP256) devices were carried out by means of infrared reflow soldering system with Sn-3.8Ag-0.7Cu and Sn-3.8Ag-0.7Cu-0.03Ce lead-free solders, respectively, and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR micro-joints tester. The results indicate that the tensile strength of Sn-Ag-Cu-Ce soldered joints is better than that of Sn-Ag-Cu soldered joints. In particular, the addition of trace Ce to the Sn-Ag-Cu solder can refine the microstructures and decrease the thickness of the intermetallic compound layer of Sn-Ag-Cu solder alloys. In addition, the stress-strain response of Sn-Ag-Cu/Sn-Ag-Cu-Ce soldered joints in quad flat packaging was investigated using finite element method based on Garofalo-Arrhenius model. The simulated results indicate creep distribution of soldered joints is not uniform, the heel and toe of soldered joints, the area between soldered joints and leads are the creep concentrated sites. The creep strain of Sn-Ag-Cu-Ce soldered joints is lower than that of Sn-Ag-Cu soldered joints. © Springer Science+Business Media, LLC 2009.