MECHANICAL PROPERTIES OF FINE PITCH DEVICES SOLDERED JOINTS BASED ON CREEP MODEL

作     者：ZHANG Liang XUE Songbai HAN Zongjie WANG Jianxin GAO Lili SHENG Zhong 

作者机构：College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China 

出 版 物：《Chinese Journal of Mechanical Engineering》 (中国机械工程学报（英文版）)

年 卷 期：2008年第21卷第6期

页      面：82-85页

核心收录：

学科分类：08[工学] 0801[工学-力学（可授工学、理学学位）] 

基　　金：supported by Six Kind Skilled Personnel Project of Jiangsu Province,China (No.06-E-020) Jiangsu General Colleges and Universities Postgraduate Scientific Research Innovative Plan,China (No.CX07B_087z) 

主　　题：Finite element method creep properties tensile strength fracture microstructure 

摘      要：Nonlinear analyses of quad flat package （QFP） on printed circuit board （PCB） assemblies subjected to thermal cycling conditions are presented. Two different solders are considered, namely, Sn37Pb and Sn3.5Ag. The stress and strain response of fine pitch devices soldered joints was investigated by using finite element method based on Garofalo-Arrheninus 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 similar phenomena of stress curves simulated based on Garofalo-Arrheninus model and Anand equations is confirmed, and the creep strain value of Sn3.5Ag soldered joints is lower than that of Sn37Pb soldered joints. Thermal cycling results show that Sn3.5Ag strongly outperforms Sn37Pb for QFP devices under the studied test condition. This is well matched with the experimental outcome analyzed. In addition, the soldered devices were tested by micro-joints tester, the tensile strength of Sn3.5Ag soldered joints is found to be higher than that of Sn37Pb soldered joints. By analyzing the fracture microstructure of soldered joints, it is found that fracture mechanism of Sn3.5Ag soldered joints is toughness fracture, while fracture mechanism of Sn37Pb soldered joints includes brittle fracture and toughness fracture. The results of this study provide an important basis of understanding the mechanical properties of fine pitch devices with traditional Sn37Pb and Sn3.5Ag lead-free soldered joints.