An alternative low cost replacement for silver and gold conductive inks is of great interest to the printed electronics industry. Nano particle copper inks and silver coated nano copper inks are some of the alternative materials being tested for use, especially in applications where low temperature flexible substrates are favored. Although the inkjettability of nano copper ink influence on print quality has been reported, information regarding the relationship between ink film thickness and energy required for sintering by intensive pulse light is not yet understood. In this study, an inkjettable nano copper ink was printed on PET (PolyEthyleneTerepthalate) and glass and the samples were sintered using bursts of high intensity pulsed light. The amount of energy applied determined the degree of sintering among particles. The greater the number of sintered nanoparticles, the higher is the conductivity of the printed traces. A comparison of energy levels required for sintering on glass and PET in relationship to ink film thickness is reported and the thermal contribution of the substrate to the processing energy requirements of this ink is revealed.