Step nano-mechanical behavior of SnAgCu solder joints under nano-indentation method

Abstract

With the decrease of the size of lead-free solder joints, the reliability of solder joints is particularly prominent, which is critical to the mechanical behavior of solder joints. While in the actual production process, the stresses for solder joints are often complex. In this paper, the nano-indentation is used to obtain the mechanical behaviors and the step behaviors of Sn3.0Ag0.5Cu and Sn0.3Ag0.7Cu. The effect of different experimental parameters for the two kinds of BGA solder joints on step performance were all investigated through the step load-unload test of nano-indentation. In the results, the indentation depth increased with the increase of the maximum loading force. At the same loading force, the increasing loading step leads to the increase of the damage accumulation and the decrease of CIT value. The plastic deformation rises when the loading rate increases. The damage in BGA solder joints increases cumulatively with the increase of the holding time; compared with the test whose holding time increases from 5s to 60s, the creep depth amplitude in the test that holding time increases from 120s to 180s is much larger.