The effect of Sb content on the properties of Sn-Bi solders was studied. The nonequilibrium melting behaviors of a series of Sn-Bi-Sb solders were examined by differential scanning calorimetry （DSC）. The spreading t...The effect of Sb content on the properties of Sn-Bi solders was studied. The nonequilibrium melting behaviors of a series of Sn-Bi-Sb solders were examined by differential scanning calorimetry （DSC）. The spreading test was carried out to characterize the wettability of Sn-Bi-Sb solders on Cu substrate. The mechanical properties of the solders/Cu joints were evaluated. The results show that the ternary alloy solders contain eutectic structure resulting from quasi-peritetic reaction. With the increase of Sb content, the amount of the eutectic structure increases. At a heating rate of 5 ℃/min, Sn-Bi-Sb alloys exhibit a higher melting point and a wider melting range. A small amount of Sb has an impact on the wettability of Sn-Bi solders. The reaction layers form during spreading process. Sb is detected in the reaction layer while Bi is not detected. The total thickness of reaction layer between solder and Cu increases with the increase of the Sb content. The shear strength of the Sn-Bi-Sb solders increases as the Sb content increases.展开更多
The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically prac...The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically practical to a certain degree…”,although replacement“…is scientifically and technically still impractical in the majority of applications.”Thus,two decades of sustained research and development may be approaching fruition,at first limited to a minority of applications.Therefore,it is of paramount importance to assess the viability of lead-free piezoceramics over a broad range of application-relevant properties.These are identified and discussed in turn:1.Cost,2.Reproducibility,3.Mechanical and Thermal Properties,4.Electrical Conductivity,and 5.Lifetime.It is suggested that the worldwide efforts into the development of lead-free piezoceramics now require a broader perspective to bring the work to the next stage of development by supporting implementation into real devices.Guidelines about pertinent research requirements into a wide range of secondary properties,measurement techniques,and salient literature are provided.展开更多
Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the ut...Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the utilization,recycling,and disposal of lead-based piezoelectric ceramics have induced a new surge in developing lead-free piezoelectric ceramics.Among all the lead-free ceramics,(K,Na)NbO3(KNN)has drawn increasing attention because of its well-balanced piezoelectric properties and better environmental compatibility.On basis of the author’s work,this review summarizes the progress that has been made in recent years on development of KNN-based piezoelectric ceramics,including crystallographic structure and phase transition analysis,pressurized solid-state sintering as well as liquid-phase-assisted sintering process,and poling treatment for property enhancement.All in all,KNN is a promising lead-free system,but more research is still required both from academic and industrial interests.展开更多
The effects of Ag on the microstructure and corrosion behavior of pre-soldering Sn-xAg lead-free solders,and on the formation of intermetallic layer of the solders with Cu substrate were investigated.The Ag contents(x...The effects of Ag on the microstructure and corrosion behavior of pre-soldering Sn-xAg lead-free solders,and on the formation of intermetallic layer of the solders with Cu substrate were investigated.The Ag contents(x)were 0,3.0,3.5,4.0,and5.0 wt.%.The Ag content played a role in the morphology of Ag3 Sn phase in the solders.The microstructure analysis showed that theβ-Sn phase was surrounded by eutectic networks in the 3.0 Ag and 3.5 Ag solders and large plate-like Ag3 Sn formed in the 4.0 Ag and5.0 Ag solders.Nonetheless,the Ag content slightly impacted the corrosion behavior of the as-cast solders as characterized using potentiodynamic polarization test.After soldering,only a single layer of a Cu6 Sn5 intermetallic compound formed at the Sn-xAg/Cu interface.By comparison,the Cu6 Sn5 intermetallic layer of the Ag-doped solders was thinner than that of the 0Ag solder.The fine Ag3 Sn particles in the eutectic networks precipitating in the 3.0 Ag and 3.5 Ag solders effectively hindered the growth of Cu6 Sn5 grains compared to large plate-like Ag3 Sn in the 4.0 and 5.0Ag solders.展开更多
基金Project(51004039)supported by the National Natural Science Foundation of ChinaProject(2012713)supported by the Cooperation Promoting Foundation in Science and Technology of Shaoxing City,China
文摘The effect of Sb content on the properties of Sn-Bi solders was studied. The nonequilibrium melting behaviors of a series of Sn-Bi-Sb solders were examined by differential scanning calorimetry （DSC）. The spreading test was carried out to characterize the wettability of Sn-Bi-Sb solders on Cu substrate. The mechanical properties of the solders/Cu joints were evaluated. The results show that the ternary alloy solders contain eutectic structure resulting from quasi-peritetic reaction. With the increase of Sb content, the amount of the eutectic structure increases. At a heating rate of 5 ℃/min, Sn-Bi-Sb alloys exhibit a higher melting point and a wider melting range. A small amount of Sb has an impact on the wettability of Sn-Bi solders. The reaction layers form during spreading process. Sb is detected in the reaction layer while Bi is not detected. The total thickness of reaction layer between solder and Cu increases with the increase of the Sb content. The shear strength of the Sn-Bi-Sb solders increases as the Sb content increases.
文摘The recent review for the Restriction of Hazardous Substances Directive(RoHS)by the expert committee,appointed by the European Union,stated that the replacement of PZT“…may be scientifically and technologically practical to a certain degree…”,although replacement“…is scientifically and technically still impractical in the majority of applications.”Thus,two decades of sustained research and development may be approaching fruition,at first limited to a minority of applications.Therefore,it is of paramount importance to assess the viability of lead-free piezoceramics over a broad range of application-relevant properties.These are identified and discussed in turn:1.Cost,2.Reproducibility,3.Mechanical and Thermal Properties,4.Electrical Conductivity,and 5.Lifetime.It is suggested that the worldwide efforts into the development of lead-free piezoceramics now require a broader perspective to bring the work to the next stage of development by supporting implementation into real devices.Guidelines about pertinent research requirements into a wide range of secondary properties,measurement techniques,and salient literature are provided.
基金Tsinghua University Initiative Scientific Research Program and National Nature Science Foundation of China(Grant Nos.50921061 and 51028202).
文摘Most widely used piezoelectric ceramics are based on Pb(Zr,Ti)O3(PZT)composition which has adverse environmental and health effects due to its high lead content.Environmental and safety concerns with respect to the utilization,recycling,and disposal of lead-based piezoelectric ceramics have induced a new surge in developing lead-free piezoelectric ceramics.Among all the lead-free ceramics,(K,Na)NbO3(KNN)has drawn increasing attention because of its well-balanced piezoelectric properties and better environmental compatibility.On basis of the author’s work,this review summarizes the progress that has been made in recent years on development of KNN-based piezoelectric ceramics,including crystallographic structure and phase transition analysis,pressurized solid-state sintering as well as liquid-phase-assisted sintering process,and poling treatment for property enhancement.All in all,KNN is a promising lead-free system,but more research is still required both from academic and industrial interests.
文摘The effects of Ag on the microstructure and corrosion behavior of pre-soldering Sn-xAg lead-free solders,and on the formation of intermetallic layer of the solders with Cu substrate were investigated.The Ag contents(x)were 0,3.0,3.5,4.0,and5.0 wt.%.The Ag content played a role in the morphology of Ag3 Sn phase in the solders.The microstructure analysis showed that theβ-Sn phase was surrounded by eutectic networks in the 3.0 Ag and 3.5 Ag solders and large plate-like Ag3 Sn formed in the 4.0 Ag and5.0 Ag solders.Nonetheless,the Ag content slightly impacted the corrosion behavior of the as-cast solders as characterized using potentiodynamic polarization test.After soldering,only a single layer of a Cu6 Sn5 intermetallic compound formed at the Sn-xAg/Cu interface.By comparison,the Cu6 Sn5 intermetallic layer of the Ag-doped solders was thinner than that of the 0Ag solder.The fine Ag3 Sn particles in the eutectic networks precipitating in the 3.0 Ag and 3.5 Ag solders effectively hindered the growth of Cu6 Sn5 grains compared to large plate-like Ag3 Sn in the 4.0 and 5.0Ag solders.
