Properties and microstructures of SnAgCu-xEu alloys for concentrator silicon solar cells solder layer

In order to improve the reliability of solar cell solder joints, rare earth Eu was selected as the additive into SnAgCu solders; the properties and microstructure of SnAgCu-xEu were studied systematically. The results indicated that the addition of Eu can improve the solderability, mechanical properties, creep resistance, and thermal fatigue reliability. The optimum content of Eu is 0.04 wt%; the creep rupture life can be increased up to 8.5 times, and the thermal fatigue life is 37.4% higher than original SnAgCu solders. However, excessive content of Eu addition can deteriorate the properties. And the rare earth Eu can refine the microstructure matrix, and reduce the size of β-Sn.