| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 104 === This paper investigates the changes in mechanical properties and IMC layer of Sn-Zn-based lead-free solders after the aging treatment. In the experiments, the Sn-xZn(x=4, 7)wt.% is used as solder base; Cu(2.5wt.%) and Ag (2.5wt.%) are added to Sn-4Zn lead-free solders, and Cu(3wt.%) and Ag (3wt.%) are added to Sn-7Zn lead-free solders. In addition, the effects of different cooling rates via air, water and ice salt water on the microstructure, mechanical properties and wettability are investigated in detail and also compared with the conventional Sn40Pb solder widely used in the industry. As for the solder paste, the mixture of alloy powder and a self-developed scaling powder is used, and also compared with the commercialized Sn3.5Ag, Sn-Ag-Cu based lead-free solder paste.
The experimental results indicate that when welding is done at 250°C, the wetting angle appears to be smaller and it becomes larger when the welding temperature is higher.From the optical microscopy observations, the IMC layer has a significant growth after aging at a constant temperature of 150°C for 250h and 500h, and the shear strength also have significant decreasing trend.The study discovers that under rapid cooling, the microstructure is more refined. With the coarsening of IMC layer and microstructure, the shear strength gradually decreases.The mechanical properties of solder paste are more stable when the alloy powder reaches 88wt.%.
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