Investigating heat transfer coefficient differences on printed circuit boards during vapour phase reflow soldering

The paper presents an analysis of measuring and evaluating heat transfer coefficients for Vapour Phase Soldering (VPS) in saturated vapour for electronics assembling. The prepared Printed Circuit Board (PCB) is practically considered as a horizontal plate (rectangular or disc shaped) during the process. The novel measurement setup is optimized to minimize any perturbing effect of the instrumentation. The obtained temperature data is processed to calculate the heat transfer coefficient distribution on the boards, where the inhomogeneity of the heating is presented according to the geometry of the PCB. The differences reveal the need of careful circuit and component placement design, while the heat transfer coefficient values may considerably differ even on a simple board shape and surface during heating according to the central parts and edges-corners of the rectangular board. The effect is more emphasized on rectangle boards, however edge effect it is also observable on disc shaped boards as well. The paper also points to related design and manufacturing recommendations.