| Exploring new types of Lead-free solders have become one of the main contents on studying the electronic packaging materials. In order to decrease the high cost and improve the combination property of the existing lead-free solder, the study on low-Ag lead-free solder becomes extremely significant. This paper studied the effect of rare earth element Ce(0~0.25wt.%) on solder melting point, wettability, microstructure, IMC and creep resistance property of SAC0307-based solder.The results show that melting points of SAC0307-xCe are all between 215°C and 218°C with small change. The spreading areas of SAC0307 solder increase obviously with the increasing of Ce content. The spreading area is the biggest and brightness is the best of all when adding 0.05wt.% Ce.The microstructure of SAC0307-xCe is similar to SAC0307 solder. The grains of microstructure have been refined with the increasing of Ce content, when it is 0.25wt.%Ce, lots of new small granular in local microstructure begin to gather and grow up, it can be seen that a lot of black rare earth phases are massive distribution.After aging 576 hours at 150°C, because Ce is a very active element, so an appropriate amount of Ce element can make the IMC grain be refined, and the growth rate be smaller. While the Ce content exceeds a certain value, Ce does not exist as solid solution, but the black Ce compounds, the inhibitory effect of reduced grain growth has been decreased simultaneously. The IMC of SAC0307-0.05Ce/Cu show the smallest growth rate, it further illustrates 0.05wt.%Ce inhibit the growth of the best.Hit and E of the SAC0307-xCe/Cu BGA solder joint can be measured by using nano-indentation load and displacement curve. It can be seen that Hit and E increase with the increasing of Ce content, and the creep resistance property of SAC0307-xCe solder has changed much, m decrease and n increase. Adding Ce significantly increases creep stress exponent n of solder joint, the solder has a higher creep resistance. |
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