The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal agin...The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal aging at 150 ℃ was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn-8Zn-3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn-8Zn-3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn-Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound （IMC） layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn-8Zn-3Bi solder/Cu joint.展开更多
Sn-Bi-X solders are widely used in electronic packaging industry.However,thermomigration(TM)behaviors of Sn-BiX solder joints and the orientations change of Bi grains under the temperature gradient are rarely reported...Sn-Bi-X solders are widely used in electronic packaging industry.However,thermomigration(TM)behaviors of Sn-BiX solder joints and the orientations change of Bi grains under the temperature gradient are rarely reported.In this study,Sn-Bi57-Ag0.7/Cu solder joints were used to conduct a TM test under a temperature gradient of 625℃/cm for 400 h,and an isothermal aging test at 85℃was also conducted for comparison.The microstructural evolution of Sn-Bi-X solder joints after reflow,TM and isothermal aging were analyzed by scanning electron microscopy(SEM),transmission electron microscopy(TEM)and electron probe microanalysis(EPMA).The results indicated that the Sn/Bi areal ratio after TM did not change significantly whether at the hot end(from 46.78%/52.12%to 50.90%/48.78%)or at the cold end(from 50.25%/49.64%to 48.71%/51.16%)compared with that of as-reflowed samples due to the insufficient thermal energy.The thickness of intermetallic compound(IMC)after TM at hot end(2.49μm)was very close to that of the IMC at cold end(2.52μm),which was also close to that of the aged samples.In addition,the preferred orientations of Sn and Bi grains in different Sn–Bi–Ag solder joints resulting from different conditions(reflow,TM and isothermal aging)were characterized by electron backscatter diffraction(EBSD).The obtained results demonstrated that both Sn and Bi grains had no preferred orientation whether after reflowor isothermal aging,while the orientation of Bi grains of the sample after TM changed from random direction to c-axis([0001]direction)parallel to the heat flow.Ag 3 Sn could hinder the change of orientation of Bi grains under the temperature gradient,and the corresponding mechanism was also systematically illuminated.This study firstly revealed the orientation change of Bi grains under the temperature gradient,which would have a profound guiding significance for enhancing the reliabilities of Sn–Bi–Ag solder joints.展开更多
基金Project(50675234)supported by the National Natural Science Foundation of China
文摘The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal aging at 150 ℃ was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn-8Zn-3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn-8Zn-3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn-Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound （IMC） layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn-8Zn-3Bi solder/Cu joint.
基金partially supported by the National Key R&D Program of China(No.2017YFB0305700)。
文摘Sn-Bi-X solders are widely used in electronic packaging industry.However,thermomigration(TM)behaviors of Sn-BiX solder joints and the orientations change of Bi grains under the temperature gradient are rarely reported.In this study,Sn-Bi57-Ag0.7/Cu solder joints were used to conduct a TM test under a temperature gradient of 625℃/cm for 400 h,and an isothermal aging test at 85℃was also conducted for comparison.The microstructural evolution of Sn-Bi-X solder joints after reflow,TM and isothermal aging were analyzed by scanning electron microscopy(SEM),transmission electron microscopy(TEM)and electron probe microanalysis(EPMA).The results indicated that the Sn/Bi areal ratio after TM did not change significantly whether at the hot end(from 46.78%/52.12%to 50.90%/48.78%)or at the cold end(from 50.25%/49.64%to 48.71%/51.16%)compared with that of as-reflowed samples due to the insufficient thermal energy.The thickness of intermetallic compound(IMC)after TM at hot end(2.49μm)was very close to that of the IMC at cold end(2.52μm),which was also close to that of the aged samples.In addition,the preferred orientations of Sn and Bi grains in different Sn–Bi–Ag solder joints resulting from different conditions(reflow,TM and isothermal aging)were characterized by electron backscatter diffraction(EBSD).The obtained results demonstrated that both Sn and Bi grains had no preferred orientation whether after reflowor isothermal aging,while the orientation of Bi grains of the sample after TM changed from random direction to c-axis([0001]direction)parallel to the heat flow.Ag 3 Sn could hinder the change of orientation of Bi grains under the temperature gradient,and the corresponding mechanism was also systematically illuminated.This study firstly revealed the orientation change of Bi grains under the temperature gradient,which would have a profound guiding significance for enhancing the reliabilities of Sn–Bi–Ag solder joints.
