Title :
Comparison of thermal fatigue reliability of SnPb and SAC solders under various stress range conditions
Author :
Yang, Chaoran ; Chan, Yuen Sing ; Lee, S. W Ricky ; Ye, Yuming ; Liu, Sang
Author_Institution :
Dept. of Mech. Eng., Hong Kong Univ. of Sci. & Technol., Kowloon, China
Abstract :
Most accelerated temperature cycling (ATC) tests reported the observations that SnAgCu (SAC) solders have better thermal fatigue reliability than SnPb solders due to their lower creep strain rate. But material studies revealed that this is true only when stress level is below a certain level. When the stress level in the solder increases, eventually the creep strain rate of SAC solder may outgrow that of the SnPb solder. Therefore, lead-free soldering under thermal cyclic loading may lead to more reliability concern than people expected. Further investigations on ATC tests with various stress ranges are still in demand. In the present study, by making use of distance-from-the-neutral-point (DNP) effect, a simple but effective custom-designed dummy package with various solder joint spacing is designed and manufactured to evaluate the thermal fatigue reliability of SnPb and SAC solders under different stress levels. It was found that SnPb solder could outperform SAC solder under a higher stress level condition. For the lower stress level condition, although the ATC test is still in progress, based on the present preliminary result, it is reasonable to predict that SAC solder would be better than SnPb solder in this case. The finite element analysis using the same package configuration was also conducted. The computational creep strains in the solders agreed with the ATC test results. Further discussion on the thermal fatigue life prediction is also presented in this paper.
Keywords :
copper alloys; electronics packaging; finite element analysis; lead alloys; life testing; reliability; silver alloys; soldering; solders; stress analysis; thermal stress cracking; tin alloys; SnAgCu; SnPb; accelerated temperature cycling test; creep strain rate; distance-from-the-neutral-point effect; finite element analysis; lead-free soldering; solder joint spacing; solder stress level; thermal cyclic loading; thermal fatigue reliability; Capacitive sensors; Creep; Environmentally friendly manufacturing techniques; Fatigue; Lead; Life estimation; Packaging; Soldering; Testing; Thermal stresses;
Conference_Titel :
Electronic Packaging Technology & High Density Packaging, 2009. ICEPT-HDP '09. International Conference on
Conference_Location :
Beijing
Print_ISBN :
978-1-4244-4658-2
Electronic_ISBN :
978-1-4244-4659-9
DOI :
10.1109/ICEPT.2009.5270596