Study on the process of an ultrasonic assisted soldering applied to fabricate solar cell interconnects on the silicon substrate

• Main Authors: Guan-Heng Pan, 潘冠亨
• Other Authors: 莊正利
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/21728658634566894028

碩士 === 中山醫學大學 === 職業安全衛生學系碩士班 === 104 === To meet the requirements of environmental protection, the development of green energy has became a global issue and the solar energy was a major source due to clean and without pollution. Silicon based solar cell has been widely used in solar industry for high transmission efficiency and the infrastructure was well created. However, the mechanical properties of the silicon substrate was hard and brittle that could not subjected to a high bonding load when the interconnect was made of a metal ribbon bonding on the silicon substrate using the ultrasonic welding. A conductive paste of the polymer based matrix blending conductive particles was therefore replaced the ultrasonic welding, and it was deposited on the silicon substrate to be the interconnect of solar cell. The mechanical and conductive properties of the conductive paste highly depended on the adhesive strength and the content of the conductive particles. A high manufacturing cost and reliability on the conductive paste would be a concern comparing with the metal welding on the silicon base substrates. The Sn-Zn-Sb solder wire was welding on the silicon wafers deposited with an aluminum layer with the ultrasonic assisted in this study. This process was expected to realize a metal welding on the aluminum layer and to improve the mechanical property of interconnects on silicon based solar cell. Based on experimental results, a great weldability and welding strength of the solder joining on silicon substrates with an aluminum layer can be achieved for the ultrasonic aided welding was used. Improving the preheated temperature resulting in a high shear strength was achieved due to the ultrasonic power could propagate to joining interface to remove the containment or the oxide layer formed on the surface of the aluminum layer and then the solder well joined. An exceeding elevated preheated temperature degraded the shear strength for the grain size of the solder coarsening. The microstructure of solder path was sensitive to heated history and a higher shear strength can be achieved for the solder path cooling with water than those in an air atmosphere. The coarsening grain size can be found at the front section for the solder subjected to a high radiation hated from the soldering-iron resulting a coarsening grain size was formed. Neither cracks nor delaminations were found at joining interface between solder and silicon substrates. A sound joint was achieved for both increasing ultrasonic amplitude and preheated temperature to removed the oxide layer on the surface of the aluminum layer and the particle of AlSb was found for the aluminum reacted with the stibium. This study demonstrated a high weldability and welding strength was obtained for solar on the aluminum layer with ultrasonic aided, implying this process has a great potential to be used in fabricating the interconnects of solar cell on silicon based substrate.