Experimental and Numerical Study of Natural Convection for High Powered and Wire-Bonded QFN64b Electronic Device

The main objective of this work is to quantify the free convective heat transfer concerning the wire-bonded version of the QFN electronic device equipped with 64 leads. This package denoted as QFN64b generates a high power varying between 0.1 W and 1.0 W by steps of 0.1 W. It is welded on a Printed Circuit Board (PCB) which may be inclined with respect to the horizontal plane by an angle ranging from 0° (horizontal position) to 90° (vertical position) by steps of 15°. These power and inclination angle ranges correspond to the normal operation of the device for the intended application. The electronic assembly is installed into an air-filled parallelepipedic box. Correlations are proposed to calculate the average convective heat transfer coefficient according to the generated power and the inclination angle on five specific assembly areas. The work done by means of a numerical approach using the finite volume method is complemented by an experimental study. The calculations are in good agreement with measurements, confirming the validity of the proposed correlations. These tools allow a better thermal control of the QFN64b increasingly used in electronics. They complement the recent results related to the same assembly considering lower generated power ranging between 0.01 and 0.1 W, corresponding to the partial operation of the electronic equipments.