The effects of temperature and solders on the wettability between ribbon and solar cell

Wettability between ribbons of two lead SnAgPb (SAP) and SnPb (SP) solders, and a lead-free SnAgCu (SAC) solder on two Ag paste substrates at temperature ranging from 190 to 280 °C was investigated by the sessile-drop method. The Contact angle (CA) method at high and room temperature was applied to measure the wettability of solder and Ag substrate. For the CA measurement obtained at high temperature, it is generally seen that CA values decreased with increasing soldering temperatures. On the other hand, the CA values of SAP solder were lower than those of SP and SAC solders at 220–240 °C. It is suggested that SAP has a good wettability characteristic, compared to SP and SAC solders, when soldering at 220–240 °C. For the CA measurement obtained at room temperature, the results showed that two lead solders had higher CA values as compared to that of a lead-free SAC solder. Furthermore, the CA values of lead solders were known to increase with increasing soldering temperatures, while SAC solder oppositely decreased with the raising soldering temperatures. In addition, CA values of SAP were detected to be higher at higher temperature than those at RT, suggesting that SAP has dewetting characteristics during the soldering process.