3D mapping of forced convection efficiency in reflow ovens

In this paper, the investigation of the heating efficiency in forced convection reflow ovens which apply nozzle-matrix blower system is discussed. In these ovens the forced convection heat transfer coefficient (AA) determines manly the efficiency of heating. Therefore we present here a method where the 3D distribution of AA is determined from temperature distribution measurements in each heater zone of the reflow oven. The method has two steps: first, the temperature distribution in the oven is measured as a function of distance from the circuit board under chosen reference nozzle-line; in the second step, the heating efficiency of the neighbouring nozzle-lines is compared - at a dedicated measuring height - to the reference nozzle-line. From these data the distribution of AA is calculated by the heat equation of the measurement system and extrapolated to the whole oven. The result is a 3D distribution map of AA which is very important to the effective thermal modelling of the reflow soldering process and to the calibration of the reflow oven