Free convective heat transfer for a tilted electronic assembly equipped with qfn64 device

Abstract

The Quad Flat No-lead 64 type device (QFN64) is increasingly used in electronics giving its well known advantages. Its correct operation is nevertheless associated to adequate thermoregulation in accordance with the manufacturers' recommendations. The printed circuit board (PCB) containing this active component is installed in cavities with different form and dimensions according to the intended application. The heat transfer by natural convection phenomenon with air is often favoured in applications. The thermal design of these electronic assemblies then requires the full control of the natural convective heat transfer exchanges that occur on all the assembly's areas. It does not exist in the specialized literature correlations to determine accurately the convective heat transfer coefficients concerning the treated QFN64 whose high generated volumetric power can reach several GWm-3. The objective of the present work is to characterize the natural thermal phenomena concerning these arrangements and quantify through easy to use correlations these convective heat transfer coefficients according to the power generated by the QFN64 and the inclination angle of the PCB with respect to the horizontal. These data are useful for the thermal control and design of this interesting electronic assembly. The work is based on a 3D numerical approach by means of the control volume method.