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 t...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 soldewed 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.展开更多
With the development of lead-free solder alloys, the investiagtion focusing on the relibility of lead-free solders are essential. Since the reliability database of lead-free solder joints needs to be further supplied,...With the development of lead-free solder alloys, the investiagtion focusing on the relibility of lead-free solders are essential. Since the reliability database of lead-free solder joints needs to be further supplied, the creep behavior of SnAgCu soldered joints on Quad Flat Package （QFP） devices under thermo cycling load are studied in this paper, compared to conventional SnPb solder, by finite element simulation based on Garofalo-Arrhenius creep model. Meanwhile, the mechanical properties of SnAgCu and SnPb soldered joints in the pitches of QFP devices are also carried out by means of tensile test. The results indicate that the values of strain and stress of SnAgCu soldered joints were all smaller than those of SnPb under thermal cycling, and the tensile strength of the joints soldered with SnAgCu solder was higher than that of SnPb, which means the reliability of the joints soldered with SnAgCu solder is better than SnPb soldered joints. As the fracture surface morphology of the soldered joints compared, SnAgCu soldered joint presented ductile fracture, while the fracture mechanism of SnPb solder joints displayed both brittle and ductile fracture. Above all, the experimental results is in accord with that of simulation, which will provide guidance for reliability study and application of lead-free solders.展开更多
基金This project is supported by Provincial Six Kind Skilled Personnel Project of Jiangsu,China(No.06-E-020).
文摘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 soldewed 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.
文摘With the development of lead-free solder alloys, the investiagtion focusing on the relibility of lead-free solders are essential. Since the reliability database of lead-free solder joints needs to be further supplied, the creep behavior of SnAgCu soldered joints on Quad Flat Package （QFP） devices under thermo cycling load are studied in this paper, compared to conventional SnPb solder, by finite element simulation based on Garofalo-Arrhenius creep model. Meanwhile, the mechanical properties of SnAgCu and SnPb soldered joints in the pitches of QFP devices are also carried out by means of tensile test. The results indicate that the values of strain and stress of SnAgCu soldered joints were all smaller than those of SnPb under thermal cycling, and the tensile strength of the joints soldered with SnAgCu solder was higher than that of SnPb, which means the reliability of the joints soldered with SnAgCu solder is better than SnPb soldered joints. As the fracture surface morphology of the soldered joints compared, SnAgCu soldered joint presented ductile fracture, while the fracture mechanism of SnPb solder joints displayed both brittle and ductile fracture. Above all, the experimental results is in accord with that of simulation, which will provide guidance for reliability study and application of lead-free solders.
