A method for curing solder paste on a thermally fragile substrate is disclosed. An optically reflective layer and an optically absorptive layer are printed on a thermally fragile substrate. Multiple conductive traces are selectively deposited on the optically reflective layer and on the optically absorptive layer. Solder paste is then applied on selective locations that are corresponding to locations of the optically absorptive layer. After a component has been placed on the solder paste, the substrate is irradiated from one side with uniform pulsed light. The optically absorptive layer absorbs the pulsed light and becomes heated, and the heat is subsequently transferred to the solder paste and the component via thermal conduction in order to heat and melt the solder paste.