Modelling of Solder Joint Geometry for Quality and Reliability

The final geometry of the solder joints in surface mount technology (SMT) assemblies is dependant upon the design rules, the materials and the manufacturing processes used. An understanding of these dependencies should allow the design of assemblies that have satisfactory thermal fatigue strength, while minimising the probability of process defects such as shorts and opens. This paper presents preliminary results from the use of a computational modelling tool, the Surface Evolver, in the simulation of the formation and geometry of solder joints and in the understanding of solder wetting phenomena. The paper also identifies other application areas for Evolver relevant to SMT.