Modeling of Three-Dimensional Geometry of Solder Joint in Fiber Attachment Soldering

Fiber attachment soldering is low cost and high-precision technology in direct-coupling optoelectronic packaging. The self-alignment of solder joint and the ultimate alignment accuracy depend on the parameters of design and manufacturing process, eventually the solder joint geometry. In this paper, the three-dimensional (3-D) geometry of solder joint in fiber attachment soldering was predicted by using the public domain software called Surface Evolver. Based on the minimum potential energy theorem and data from geometry simulation, the influences of design and material parameters on the stand-off height (SOH) and torque misalignment were analyzed in detail. The results show that the SOH exists only when solder volume reaches to the critical value. If proper pad design is provided, the restoring torque on the fiber during solder joint formation will be magnified. The results can be used to control the solder joint geometry and improve the alignment of optical fiber.