The reactive Sn63Pb37 spreading on patterned film structures was examined in a reducing atmosphere (H2 5%+Ar 95%). Liquid solder spreading was observed to follow the wheel pattern made of Au/Cu thin film. At the ce...The reactive Sn63Pb37 spreading on patterned film structures was examined in a reducing atmosphere (H2 5%+Ar 95%). Liquid solder spreading was observed to follow the wheel pattern made of Au/Cu thin film. At the center, a liquid cap was formed around the hub by viscous spreading of the liquid front. Ahead of the main viscous flow front, a liquid film was found to be extended on thin Au-Cu lines at a fast rate to a great distance by rapid Sn-Au chemical reaction.展开更多
Density functional theory was employed to investigate the bismuth segregation at Cu/Cu3Sn(010) interface. Five initial constructions were introduced by adopting the adhesion energy criterion. Among them, the so-call...Density functional theory was employed to investigate the bismuth segregation at Cu/Cu3Sn(010) interface. Five initial constructions were introduced by adopting the adhesion energy criterion. Among them, the so-called "between-Cu" construction in which the interface Cu atoms of Cu slab locate along Cu-Cu bond direction in Cu3Sn slab was found to be the most energy-favored at an adhesion energy of 1.96 J/m^2. Based on this construction, five possible segregation sites were examined, and the most likely segregation site was determined with adhesion energy as low as 1.06 J/m^2, which was almost half of the initial one. Comparing with other sitest adhesion energies, it was concluded that size effect took a large part in embrittlement. The analyses of atomic structure and electronic density revealed that the slabs shifted away from interfaces due to bismuth segregation, and the atoms around Bi atom were Dressed away. This calculated work agreed aualitativelv with reported experimental results.展开更多
Effects of electromigration on microstructure, shear strength, and fracture behavior of solder joints were investigated by single-ball shear samples of eutectic Sn-3.8Ag-0.7Cu (SAC) joined by Cu plates at two sides....Effects of electromigration on microstructure, shear strength, and fracture behavior of solder joints were investigated by single-ball shear samples of eutectic Sn-3.8Ag-0.7Cu (SAC) joined by Cu plates at two sides. The electromigration tests were conducted at a current density of about 1.1×10^3 A/cm2 and a working temperature of about 83℃. The results showed that the shear strength and flow stress decreased greatly after current stressing. Such a decrease was associated with no significant loss of the fracture strain at short electromigration but a great reduction in the fracture strain after long-term current stressing. The variation of the fracture strain with the electromigration time was shown to result from the shift of the fracture surface from the center of the solder towards the intermetallic compound (IMC) interface at the cathode.展开更多
Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prest...Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prestrain, Bi interfacial segregation to the anode, a clear indication of electromigration damage in SnBi solder inter- connect, was effectively prevented. Such an inhibiting effect is apparently contrary to the common notion that dislocations often act as fast diffusion paths. It is suggested that the dislocations introduced by plastic prestraining acted as sinks for vacancies in the early stage of the electromigration process, but as the vacancies accumulated at the dislocations, climb of those dislocations prompted recovery of the deformed samples under current stressing, greatly decreasing the density of dislocation and vacancy in the solder, leading to slower diffusion of Bi atoms.展开更多
基金supported by the National Nat-ural Science Foundation of China (No.50501022)the National Basic Research Program of China (No.2004CB619306)
文摘The reactive Sn63Pb37 spreading on patterned film structures was examined in a reducing atmosphere (H2 5%+Ar 95%). Liquid solder spreading was observed to follow the wheel pattern made of Au/Cu thin film. At the center, a liquid cap was formed around the hub by viscous spreading of the liquid front. Ahead of the main viscous flow front, a liquid film was found to be extended on thin Au-Cu lines at a fast rate to a great distance by rapid Sn-Au chemical reaction.
基金supports fromthe National Basic Research Program of China (Nos.2006CB605103 and 2010CB631006)the Hundred Talents Program of the Chinese Academy of Sciences,and the Liaoning Natural Science Foundation of China (No.20082015)
文摘Density functional theory was employed to investigate the bismuth segregation at Cu/Cu3Sn(010) interface. Five initial constructions were introduced by adopting the adhesion energy criterion. Among them, the so-called "between-Cu" construction in which the interface Cu atoms of Cu slab locate along Cu-Cu bond direction in Cu3Sn slab was found to be the most energy-favored at an adhesion energy of 1.96 J/m^2. Based on this construction, five possible segregation sites were examined, and the most likely segregation site was determined with adhesion energy as low as 1.06 J/m^2, which was almost half of the initial one. Comparing with other sitest adhesion energies, it was concluded that size effect took a large part in embrittlement. The analyses of atomic structure and electronic density revealed that the slabs shifted away from interfaces due to bismuth segregation, and the atoms around Bi atom were Dressed away. This calculated work agreed aualitativelv with reported experimental results.
基金supported by the National Basic Research Program of China (Grant Nos.2004CB619306 and 2010CB631006)
文摘Effects of electromigration on microstructure, shear strength, and fracture behavior of solder joints were investigated by single-ball shear samples of eutectic Sn-3.8Ag-0.7Cu (SAC) joined by Cu plates at two sides. The electromigration tests were conducted at a current density of about 1.1×10^3 A/cm2 and a working temperature of about 83℃. The results showed that the shear strength and flow stress decreased greatly after current stressing. Such a decrease was associated with no significant loss of the fracture strain at short electromigration but a great reduction in the fracture strain after long-term current stressing. The variation of the fracture strain with the electromigration time was shown to result from the shift of the fracture surface from the center of the solder towards the intermetallic compound (IMC) interface at the cathode.
基金supported by the National Natural Science Foundation of China (Grant No. 51171191)the National Basic Research Program of China (Grant No. 2010CB631006)the Natural Science Foundation of Liaoning Province, China (Grant No. 20092076)
文摘Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prestrain, Bi interfacial segregation to the anode, a clear indication of electromigration damage in SnBi solder inter- connect, was effectively prevented. Such an inhibiting effect is apparently contrary to the common notion that dislocations often act as fast diffusion paths. It is suggested that the dislocations introduced by plastic prestraining acted as sinks for vacancies in the early stage of the electromigration process, but as the vacancies accumulated at the dislocations, climb of those dislocations prompted recovery of the deformed samples under current stressing, greatly decreasing the density of dislocation and vacancy in the solder, leading to slower diffusion of Bi atoms.