Study On Soldering Process And Reliability Of Interconnections Between Photovoltaic Ribbon And Crystallion Silicon Solar Cell

As the most important new energy source in 21 st century, Solar energy is of great significance to solve our energy crisis and environmental issues. Solar module is the key of the solar power technology. Soldering which is the most important step in solar module manufacturing process directly affects the cost of solar module, photoelectric conversion efficiency and service life of the cell. Owing to poor thermal cycling performance of solder joints using civil soldering process which widely used in module manufaction, they can not meet the space requirements. The goal of this project is to study new soldering process which thermal cycling performance and peeling strength of solder joints can meet the space requirements. Moreover, the reliability of solder joints was investigated.Two methods including manual spot welding and thermocompression bonding were developed, and thermocompression bonding method was chosen due to its good thermal cycling performance. Orthogonal experimental method was used to optimize the parameters of thermocompression bonding method, and the optimal parameter group was determined.The influence of parameters on the test results was investigated by range analysis and variance analysis. The thermal cycling test and the peeling test showed that the performance of the optimal parameter group met the standard of aerospace test.The interfacial reaction and failure modes of Sn-37Pb/Ag, Sn-3.5Ag/Ag and Sn-3.0Ag-0.5Cu/Ag interfaces were analyzed. Ag₃Sn layer was found in the interface between the solder and the silver paste. The thickness of Ag₃Sn and the microstructure of solder were characterized after thermal cycling test. With the increase of thermal cycles, the thickness of Ag₃Sn increased gradually, and the thickness of Ag₃Sn at Sn-37Pb/Ag interface growed faster than other two lead-free solders. IMC or phases in the solder coarsened gradually during thermal cycling test.Isothermal aging growth of Ag₃Sn and the kinetics of Sn-37Pb/Ag, Sn-3.5Ag/Ag and Sn-3.0Ag-0.5Cu/Ag were studied. Growth of Ag₃Sn showed a parabola type, and the growth rates of Ag₃Sn at different temperatures were calculated. The growth activation energies for Ag₃Sn at Sn-37Pb/Ag, Sn-3.5Ag/Ag and Sn-3.0Ag-0.5Cu/Ag interfaces were calculated to be 113.3 kJ/mol, 129.9 kJ/mol and 123.1 kJ/mol, respectively.