Among heat transfer augmentation techniques, passive cooling technique found more suitable for electronic cooling than active technique. In this paper, natural convection heat transfer analysis through rectangular fins is reviewed. Various experimental studies have been made to investigate effect of fin height, fin spacing, fin length and fin thickness over convective heat transfer. Effects of thermodynamic properties like heat input, base-to-ambient temperature difference are also studied by many researchers. Some investigators make known sets of correlations screening the relation between various parameters of heat sink. Experiments are taken by some researchers for upward and downward facing rectangular fins. Also, trivial investigation has been carried out for different angle of inclination of the heat sink. The sensitivity of inclination over geometric parameters found to be great importance.