EFFECTS OF LEAD WIDTHS AND PITCHES ON RELIABILITY OF QUAD FLAT PACKAGE (QFP) SOLDERED JOINTS

• 作 者: XUE Songbai WU Yuxiu HAN Zongj
• 机 构: College of Materials Science and Technology,Nanjing University of Aeronautics and Astronautics,Nanji
• 出 处: 机械工程学报（英文版）
• 发表日期: 2007年4期
• 关键词: Quad flat package (QFP) Maximum equivalent stress Soldered joints Assembly optim
• 基金项目: Provincial Six Kind Skilied Personnel Project of Jiangsu, China

The finite element method(FEM) is used to analyze the effects of lead widths and pitches on reliability of soldered joints. The optimum Simulation for QFP devices is also researched. The results indicate that when the lead pitches are the same, the maximum equivalent stress of the soldered joints increases with the increasing of lead widths, while the reliability of the soldered joints reduces. When the lead widths are the same, the maximum equivalent stress of the soldered joints doesn’t decrease completely with the increasing of lead pitches, a minimum value of the maximum equivalent stress values exists in all the curves. Under this condition the maximum equivalent stress of the soldered joints is relatively the least, the reliability of soldered joints is high and the assembly is excellent. The simulating results indicate the best parameter: The lead width is 0.2 mm and lead pitch is 0.3 mm (the distance between two leads is 0.1 mm), which are benefited for the micromation of QFP devices now. The minimum value of the maximum equivalent stress of soldered joints exists while lead width is 0.25 mm and lead pitch is 0.35 mm (the distance between two leads is 0.1 mm), the devices can serve for a long time and the reliability is the highest, the assembly is excellent. The simulating results also indicate the fact that the lead width is 0.15 mm and lead pitch is 0.2 mm maybe the limit of QFP, which is significant for the high lead count and micromation of assembly.