A method of soldering electronic components to a heat sensitive flexible substrate with cooling for a vector transient reflow process is disclosed. The method comprises applying solder paste to the substrate and placing electronic components to the substrate to form a substrate assembly. The method further includes locating the substrate assembly on a pallet having a heat conductive layer for heat sinking means from the substrate. The method further includes rapid localized heating to a melting temperature sufficient to melt the solder paste using a supplemental heat source. While exposing the deposited solder paste to further rapid localized heating, the method further comprises cooling the pallet at the second surface to diffuse the heat from the substrate defining a temperature gradient across the substrate.