Distribution of the heat transfer coefficient in convection reflow oven

Nowadays reflow ovens apply forced convection heating with nozzle-matrix blower system which generates numerous heater gas streams. In these types of ovens the heat transfer coefficients of the gas streams determine mainly the efficiency of heating. In this paper a measurement method is discussed which can determine the heat transfer coefficient distribution under the nozzle-matrix of a convection reflow oven. During the experiments, temperature changes have been measured and the heat transfer coefficient has been calculated using the heat equation of the investigated reflow oven. In the first step, the heat transfer coefficient of the heater gas streams has been studied under the nozzle-matrix in function of height. In the second step, the heating efficiency of the nozzle-lines has been compared and the distribution of the heat transfer coefficient has been calculated. The results are confirmed by a theoretical model. It is also presented that how the contamination of the nozzles affects the heating efficiency of the reflow oven. This measuring method can be useful for monitoring the operation of the reflow oven, soldering failure prediction and measuring input parameters of thermal modeling.