The paper presents new results in the simplified modelling of Vapour Phase Soldering (VPS) heat transfer process, where the prepared Printed Circuit Board (PCB) is assumed as a horizontal plate during the process. The paper focuses on previously not investigated round-shaped PCB plates. An explicit modelling method (based on Nusselt theory) was modified and used to investigate the heat transfer on the different sized PCBs. For verification, measurements were performed in an experimental VPS oven. Different models and introduced corrections were used for the calculations, where the final results showed acceptable error values compared to measurement data. The results point out that a specific modelling case provides the best result, without any dependence on the size of the PCB plates. It was also found that in special cases, rounded PCB corners can be neglected during calculations with rectangular PCBs. (C) 2015 Published by Elsevier Ltd.