Abstract A small amount of rare earth Ce was added to Sn-Cu-Ni solder alloy, and the solderability of Sn-0. 5Cu-0. 05Ni- xCe solders on Cu and Au/Ni/Cu substrates was determined by the wetting balance method. The effe...Abstract A small amount of rare earth Ce was added to Sn-Cu-Ni solder alloy, and the solderability of Sn-0. 5Cu-0. 05Ni- xCe solders on Cu and Au/Ni/Cu substrates was determined by the wetting balance method. The effects of atmosphere, temperature, substrate, and Ce addition on the solderability of Sn-Cu-Ni-xCe solder were studied, respectively, and Auger electron spectroscopy （ AES） analysis in the depth direction of the alloy was carried out to discuss the effect of Ce addition on the solderability. The results indicate that the greatest improvement on the solderability of Sn-Cu-Ni-xCe is obtai^d with around O. 05wt. % -0. 07wt. % Ce addition, for Ce element keeps high content in a specific area in the depth direction from the surface of Sn-Cu-Ni alloy, which decreases the surface tension of molten solder. It is also found that the solderability of Sn-Cu-Ni-xCe solder on Au/Ni/ Cu substrate is better than that on Cu substrate. In N2 atmosphere, the wetting times of Sn- Ca-Ni-xCe alloys are reduced by 10% - 35% , below 1 s at 260 ℃ on Ca substrate, and about 1s at 250 ℃ on Au/Ni/Ca substrate.展开更多
A materials design tool for developing Pb-free soldering alloys in electronic package was developed based on comprehensive experimental data of phase equilibria and thermodynamic properties data accumulated with the C...A materials design tool for developing Pb-free soldering alloys in electronic package was developed based on comprehensive experimental data of phase equilibria and thermodynamic properties data accumulated with the CALPHAD (calculation of phase diagrams) method and contains 10 elements,namely,Ag,Au,Bi,Cu,In,Ni,Sb,Sn,Zn and Pb.It can handle the calculation of phase diagrams in all combinations of these elements and all composition ranges.In addition,based on this tool,the liquidus,solidus,phase fractions and constitutions,equilibrium and non-equilibrium solidification behavior,surface tension and viscosity of liquid,diffusion reactions and microstructural evolution,etc.can be predicted.Typical examples of the calculation and application of this tool are presented.The design tool is expected to be a powerful tool for the development of Pb-free solders,as well as for promoting the understanding of the interfacial phenomena between Cu substrate and Pb-free solders in electronic packaging technology.展开更多
A small Pb-free solder joint exhibits an extremely strong anisotropy due to the body- centered tetragonal （BCT） lattice structure of β-Sn. Grain orientations can signif- icantly influence the failure mode of Pb-fre...A small Pb-free solder joint exhibits an extremely strong anisotropy due to the body- centered tetragonal （BCT） lattice structure of β-Sn. Grain orientations can signif- icantly influence the failure mode of Pb-free solder joints under thermomechanical fatigue （TMF） due to the coefficient of thermal expansion （CTE） mismatch of β-Sn grains. The research work in this paper focused on the microstructure and damage evolution of Sn3.0Ag0.5Cu BGA packages as well as individual Sn3.5Ag solder joints without constraints introduced by the package structure under TMF tests. The mi- crostructure and damage evolution in cross-sections of solder joints under thermome- chanical shock tests were Characterized using optical microscopy with cross-polarized light and scanning electron microscopy （SEM）, and orientations of Sn grains were determined by orientation imaging microscopy （OIM）. During TMF, obvious recrys- tallization regions were observed with different thermomechanical responses depend- ing on Sn grain orientations. It indicates that substantial stresses can build up at grain boundaries, leading to significant grain boundary sliding. The results show that recrystallized grains prefer to nucleate along pre-existing high-angle grain boundaries and fatigue cracks tend to propagate intergranularly in recrystallized regions, leading to an accelerated damage after recrystallization .展开更多
文摘Abstract A small amount of rare earth Ce was added to Sn-Cu-Ni solder alloy, and the solderability of Sn-0. 5Cu-0. 05Ni- xCe solders on Cu and Au/Ni/Cu substrates was determined by the wetting balance method. The effects of atmosphere, temperature, substrate, and Ce addition on the solderability of Sn-Cu-Ni-xCe solder were studied, respectively, and Auger electron spectroscopy （ AES） analysis in the depth direction of the alloy was carried out to discuss the effect of Ce addition on the solderability. The results indicate that the greatest improvement on the solderability of Sn-Cu-Ni-xCe is obtai^d with around O. 05wt. % -0. 07wt. % Ce addition, for Ce element keeps high content in a specific area in the depth direction from the surface of Sn-Cu-Ni alloy, which decreases the surface tension of molten solder. It is also found that the solderability of Sn-Cu-Ni-xCe solder on Au/Ni/ Cu substrate is better than that on Cu substrate. In N2 atmosphere, the wetting times of Sn- Ca-Ni-xCe alloys are reduced by 10% - 35% , below 1 s at 260 ℃ on Ca substrate, and about 1s at 250 ℃ on Au/Ni/Ca substrate.
基金supported by the National Natural Science Foundation of China (Grant No.50425101)the Ministry of Science and Technology,P.R.China (Grant No.2009DFA52170)+1 种基金the National High-Tech Research and Development Program of China ("863" Project) (Grant No.2009AA03Z101)the Ministry of Education,P.R.China (Grant No.707037)
文摘A materials design tool for developing Pb-free soldering alloys in electronic package was developed based on comprehensive experimental data of phase equilibria and thermodynamic properties data accumulated with the CALPHAD (calculation of phase diagrams) method and contains 10 elements,namely,Ag,Au,Bi,Cu,In,Ni,Sb,Sn,Zn and Pb.It can handle the calculation of phase diagrams in all combinations of these elements and all composition ranges.In addition,based on this tool,the liquidus,solidus,phase fractions and constitutions,equilibrium and non-equilibrium solidification behavior,surface tension and viscosity of liquid,diffusion reactions and microstructural evolution,etc.can be predicted.Typical examples of the calculation and application of this tool are presented.The design tool is expected to be a powerful tool for the development of Pb-free solders,as well as for promoting the understanding of the interfacial phenomena between Cu substrate and Pb-free solders in electronic packaging technology.
基金supported by the National Natural Science Foundation of China(No.50905042)the State Key Lab of Advanced Welding&Joining,Harbin Institute of Technology(AWPT-M12-02)
文摘A small Pb-free solder joint exhibits an extremely strong anisotropy due to the body- centered tetragonal （BCT） lattice structure of β-Sn. Grain orientations can signif- icantly influence the failure mode of Pb-free solder joints under thermomechanical fatigue （TMF） due to the coefficient of thermal expansion （CTE） mismatch of β-Sn grains. The research work in this paper focused on the microstructure and damage evolution of Sn3.0Ag0.5Cu BGA packages as well as individual Sn3.5Ag solder joints without constraints introduced by the package structure under TMF tests. The mi- crostructure and damage evolution in cross-sections of solder joints under thermome- chanical shock tests were Characterized using optical microscopy with cross-polarized light and scanning electron microscopy （SEM）, and orientations of Sn grains were determined by orientation imaging microscopy （OIM）. During TMF, obvious recrys- tallization regions were observed with different thermomechanical responses depend- ing on Sn grain orientations. It indicates that substantial stresses can build up at grain boundaries, leading to significant grain boundary sliding. The results show that recrystallized grains prefer to nucleate along pre-existing high-angle grain boundaries and fatigue cracks tend to propagate intergranularly in recrystallized regions, leading to an accelerated damage after recrystallization .
