A demystifying study of trace thickening: How does it affect the current carrying capability

Often, the printed circuit boards (PCB) for power applications are manufactured with some traces thickened by a deposit of soldering alloy. The reason for such a design feature comes from the thermal management requirements: as it is believed that this would significantly increase the current carrying capability of the trace. At a first view, such a statement might seem to make sense: thickening the trace would increase the section area of the conductor, thus decreasing its electrical resistance and also the heat dissipation due to Joule effect. On the other hand though, typical soldering alloys have much smaller electrical conductivity than copper, so much of the current will still flow through the copper section of the conductor. Other effects, such as the thermal insulation of the solder mask or the different convection coefficient of the soldering alloy as compared to copper, also affects the thermal dissipation from the trace to the environment. This paper investigates, using computational fluid dynamics (CFD) simulations and experimental measurements, how much the trace thickening actually influences the current carrying capability.