### Effect of Isothermal Aging and Thermal Cycling on Interfacial IMC Growth and Fracture Behavior of SnAgCu/Cu JointsEffect of Isothermal Aging and Thermal Cycling on Interfacial IMC Growth and Fracture Behavior of SnAgCu/Cu Joints

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 Author Li, Xiaoyan ♦ Li, Fenghui ♦ Guo, Fu ♦ Shi, Yaowu Source SpringerLink Content type Text Publisher Springer US File Format PDF Copyright Year ©2010 Language English
 Subject Domain (in DDC) Technology ♦ Engineering & allied operations Subject Keyword Pb-free solder ♦ IMCs ♦ isothermal aging ♦ thermal cycling ♦ Solid State Physics ♦ Electronics and Microelectronics, Instrumentation ♦ Characterization and Evaluation of Materials ♦ Optical and Electronic Materials Abstract The growth behavior of interfacial intermetallic compounds (IMCs) of SnAgCu/Cu soldered joints was investigated during the reflow process, isothermal aging, and thermal cycling with a focus on the influence of these parameters on growth kinetics. The SnAgCu/Cu soldered joints were isothermally aged at 125°C, 150°C, and 175°C while the thermal cycling was performed within the temperature ranges from −25°C to 125°C and −40°C to 125°C. It was observed that a Cu$_{6}$Sn$_{5}$ layer formed, followed by rapid coarsening at the solder/Cu interface during reflowing. The grain size of the interfacial Cu$_{6}$Sn$_{5}$ was found to increase with aging time, and the morphology evolved from scallop-like to needle-like to rod-like and finally to particles. The rod-like Ag$_{3}$Sn phase was formed on the solder side in front of the previously formed Cu$_{6}$Sn$_{5}$ layer. However, when subject to an increase of the aging time, the Cu$_{3}$Sn phase was formed at the interface of the Cu$_{6}$Sn$_{5}$ layer and Cu substrate. The IMC growth rate increased with aging temperature for isothermally aged joints. During thermal cycling, the thickness of the IMC layer was found to increase with the number of thermal cycles, although the growth rate was slower than that for isothermal aging. The dwell time at the high-temperature end of the thermal cycles was found to significantly influence the growth rate of the IMCs. The growth of the IMCs, for both isothermal aging and thermal cycling, was found to be Arrhenius with aging temperature, and the corresponding diffusion factor and activation energy were obtained by data fitting. The tensile strength of the soldered joints decreased with increasing aging time. Consequently, the fracture site of the soldered joints migrated from the solder matrix to the interfacial Cu$_{6}$Sn$_{5}$ layer. Finally, the shear strength of the joints was found to decrease with both an increase in the number of thermal cycles and a decrease in the dwell temperature at the low end of the thermal cycle. ISSN 03615235 Age Range 18 to 22 years ♦ above 22 year Educational Use Research Education Level UG and PG Learning Resource Type Article Publisher Date 2010-11-04 Publisher Place Boston e-ISSN 1543186X Journal Journal of Electronic Materials Volume Number 40 Issue Number 1 Page Count 11 Starting Page 51 Ending Page 61