TY - GEN
T1 - Evolution of the mechanical properties of lead free solder joints subjected to mechanical cycling
AU - Hoque, Mohd Aminul
AU - Chowdhury, Md Mahmudur
AU - Hamasha, Sa'd
AU - Suhling, Jeffrey C.
AU - Lall, Pradeep
N1 - Publisher Copyright: © 2019 IEEE
PY - 2019/5
Y1 - 2019/5
N2 - Solder joint failure is one of the primary reasons for the failure of electronic packages. When electronic components are subjected to environments with temperature gradients, the solder joints present in them undergo a fatigue thermo-mechanical state due to differences in the Thermal Expansion Coefficients (CTEs) of the different assembly materials. Understanding the mechanical cyclic properties of these lead-free solder joints has thus become a necessity to improve the reliability of these packages. In this study, we have characterized the mechanical cyclic induced microstructural evolution and consequent changes in mechanical properties of individual solder joints. The testing of individual joints is important because there are significant variations of properties between actual joints and conventional bulk samples (e.g. dog-bone, rectangular, or lap shear samples). The test assemblies in this study were (3x3) BGA packages composed of total nine 0.75 mm diameter lead free solder joints that were formed by reflowing solder spheres soldered onto 0.55 mm diameter Cu pads on FR4 coupons. The solder joints were cycled using a Micromechanical tester along with a newly designed fixture which facilitates the tester to cycle a solder joint individually. The solder joints tested were of different alloys thus also giving an idea of the effect of the addition of various dopants on the mechanical cyclic properties. The joints were cycled for various durations including to failure. Nanoindentation tests were performed on the specimens to study the evolution in mechanical properties (e.g. elastic modulus, hardness and creep strain rate) of the solder joints as a function of duration of cycling. The prime objective of this study was to better understand the damage accumulation and evolution of a specific solder joint due to mechanical cyclic fatigue loading.
AB - Solder joint failure is one of the primary reasons for the failure of electronic packages. When electronic components are subjected to environments with temperature gradients, the solder joints present in them undergo a fatigue thermo-mechanical state due to differences in the Thermal Expansion Coefficients (CTEs) of the different assembly materials. Understanding the mechanical cyclic properties of these lead-free solder joints has thus become a necessity to improve the reliability of these packages. In this study, we have characterized the mechanical cyclic induced microstructural evolution and consequent changes in mechanical properties of individual solder joints. The testing of individual joints is important because there are significant variations of properties between actual joints and conventional bulk samples (e.g. dog-bone, rectangular, or lap shear samples). The test assemblies in this study were (3x3) BGA packages composed of total nine 0.75 mm diameter lead free solder joints that were formed by reflowing solder spheres soldered onto 0.55 mm diameter Cu pads on FR4 coupons. The solder joints were cycled using a Micromechanical tester along with a newly designed fixture which facilitates the tester to cycle a solder joint individually. The solder joints tested were of different alloys thus also giving an idea of the effect of the addition of various dopants on the mechanical cyclic properties. The joints were cycled for various durations including to failure. Nanoindentation tests were performed on the specimens to study the evolution in mechanical properties (e.g. elastic modulus, hardness and creep strain rate) of the solder joints as a function of duration of cycling. The prime objective of this study was to better understand the damage accumulation and evolution of a specific solder joint due to mechanical cyclic fatigue loading.
UR - https://www.scopus.com/pages/publications/85073912390
U2 - 10.1109/ITHERM.2019.8757302
DO - 10.1109/ITHERM.2019.8757302
M3 - Conference contribution
T3 - InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, ITHERM
SP - 295
EP - 302
BT - Proceedings of the 18th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, ITherm 2019
PB - IEEE Computer Society
T2 - 18th InterSociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems, ITherm 2019
Y2 - 28 May 2019 through 31 May 2019
ER -