Forced convection board level thermal design methodology for electronic systems

The case is made for the continued use of single valued thermal resistances for the prediction of component junction temperature, and, hence, reliabil ity. These values are adjusted using empirically determined influence facto rs to account for thermal and aerodynamic interactions at board level. The paper presents measured values of influence factors for arrays of Plastic Q uad Flat Packs (PQFPs) over a range of Reynolds numbers and with a series o f board level obstacles modeling upstream passive components. The results a re formulated into a novel set of design rules.