Effects of the wire-bonding technique on the QFN16b's thermal performance. New correlations for the free convective heat transfer coefficient

The technique of wire-bonding used in electronics is interesting for thermoregulation of the quad flat non-lead (QFN) packages during operation. To properly size these devices in the assemblies, it is necessary to know the surfacic thermal phenomena represented by the convective heat transfer coefficient. This is the objective of this work examining the thermal effects due to installation of wire-bonding on a QFN16. This particular device is named here QFN16b to differentiate it from the basic model without wire-bondings addressed in a previous study. During its actual operation, it generates a power ranging from 0.1 W to 1.0 W and it is welded on a printed circuit board (PCB) which could be inclined at different angles varying between the horizontal and vertical positions, according to the intended application. Calculations corresponding to 6 different areas of the considered assembly have been done by combining 20 powers generated by the QFN and 7 inclination angles. The distribution of the surface temperature and that of the source itself, as well as the free convective power exchanged by every area, are determined. Natural convective heat transfer is quantified by means of correlations which allow calculation of the average convective heat transfer coefficient in each area of the assembly and for all the treated configurations. They improve design, reliability, durability and performance of these conventional assemblies widely used in electronics in many engineering sectors.