A comprehensive experimental and numerical study of solder joints for plastic leaded chip carrier (PLCC) 84-Pin, 1.27 mm pitch was carried out. The reliability of solder joints was assessed through accelerated thermal...A comprehensive experimental and numerical study of solder joints for plastic leaded chip carrier (PLCC) 84-Pin, 1.27 mm pitch was carried out. The reliability of solder joints was assessed through accelerated thermal cycling at the temperature range of - 55℃-125℃. The samples were taken out to observe the evolution in microstructure, such as grain coarsening, initiation and propagation of cracks. It was found that the Pb-rich phases segregated gradually and formed a continuous layer adjacent to the intermetallic compound (IMC) layer with increasing the number of thermal cycles, resulting in cracks near the solder/lead interface. The response of stress and strain was studied using nonlinear finite element method (FEM), and the results agreed well with the experimental data.展开更多
Solder bridge is a serious defect of solder joints in ultrafine pitch electronic device assemblies. Generation of the solder bridge is closely related to forming process of the solder joints. A three-dimensional model...Solder bridge is a serious defect of solder joints in ultrafine pitch electronic device assemblies. Generation of the solder bridge is closely related to forming process of the solder joints. A three-dimensional model to simulate the formation of the solder bridge of QFP256 (quad flat packaging with 256 leads) is established and numerically calculated to predict the formation shape of the solder joints using surface evolver program. Based on the model, influence of structure of pads printed on circuit board on solder bridging is investigated. The results show that there is a critical solder volume Vc for solder joints to avoid solder bridging, and parameters of the pad size influence the critical solder volume.展开更多
文摘A comprehensive experimental and numerical study of solder joints for plastic leaded chip carrier (PLCC) 84-Pin, 1.27 mm pitch was carried out. The reliability of solder joints was assessed through accelerated thermal cycling at the temperature range of - 55℃-125℃. The samples were taken out to observe the evolution in microstructure, such as grain coarsening, initiation and propagation of cracks. It was found that the Pb-rich phases segregated gradually and formed a continuous layer adjacent to the intermetallic compound (IMC) layer with increasing the number of thermal cycles, resulting in cracks near the solder/lead interface. The response of stress and strain was studied using nonlinear finite element method (FEM), and the results agreed well with the experimental data.
文摘Solder bridge is a serious defect of solder joints in ultrafine pitch electronic device assemblies. Generation of the solder bridge is closely related to forming process of the solder joints. A three-dimensional model to simulate the formation of the solder bridge of QFP256 (quad flat packaging with 256 leads) is established and numerically calculated to predict the formation shape of the solder joints using surface evolver program. Based on the model, influence of structure of pads printed on circuit board on solder bridging is investigated. The results show that there is a critical solder volume Vc for solder joints to avoid solder bridging, and parameters of the pad size influence the critical solder volume.
