Quantification of the Natural Convective Heat Transfer for the Tilted and Wire-Bonded QFN32b-PCB Electronic Assembly
Résumé
The version of the basic Quad flat non-lead QFN32 electronic device equipped with wire bondings, denoted as QFN32b, is more efficient thermally. This is due in part to the modification of the heat transfer phenomena occurring in the assembly. Although this interesting device is widely used in electronics, there are no specific correlations leading to determine accurately its associated natural convective heat transfer coefficient. This is the main objective of the present study, which considers a QFN32b generating a power ranging from 0.1 W to 1.0 W by steps of 0.05 W. It is welded in various positions of a printed circuit board (PCB), which could be inclined at different angles varying between 0° and 90° corresponding to the horizontal and vertical positions, respectively, by steps of 15°. These power and inclination angle ranges correspond to the normal operation of the device for the intended application. Calculations done by means of the finite volume method allow the determination of the free convective heat transfer coefficient on the different areas constituting the considered package. The results of the present study, compared with those of the basic QFN32 device quantified in a previous work, clearly show the influence of the wire-bonding technique on the QFN32b's thermal performance. The proposed correlations improve the design of this electronic device widely used in electronics for various applications covering many engineering fields.