Effect of Different Soldering Temperatures on the Solder Joints of Flip-Chip LED Chips

Abstract

This paper investigates the effect of different soldering temperatures on the performance of the flip-chip light-emitting diode (FC-LED) filament during direct soldering. The changes in the intermetallic compound (IMC) interface, push–pull force and chip fracture surface of the chip solder joints under direct soldering temperatures of 220°C, 260°C, and 320°C for the flip-chip LED filament were explored by scanning electron microscopy (SEM). Thereby, the optimal soldering temperature of direct joining in actual production is compared. The results show that when the soldering temperature is 260°C, Cu on the substrate begins to diffuse into the solder and react with the solder in the lower layer. The Sn content is relatively uniform, and the average push–pull force of the chip increases. The fracture occurs from inside the solder. With a soldering temperature of 260°C, it is observed that the interface shear stress of the flip-chip LED chip is the largest, and the mechanical stress and residual stress are the lowest.