The present disclosure related to a flexible electronic substrate assembly and a method and system of processing solder paste onto an electrical substrate. The assembly includes a flexible substrate having a solderable medium provided along the flexible substrate. A pattern of solder paste may be cured to a portion of the solderable medium. The solderable medium may be a generally continuous construction or a patterned construction relative to the flexible substrate. The substrate may be unwound from a roll of substrate material before solder paste is deposited thereon. The flexible electric substrate assembly may be formed though a roll to roll process. Infrared heat may be applied to the substrate with the solder paste deposit as the substrate is traveling along the process direction to reflow the solder paste as the substrate is traveling along the process direction at a high rate of speed.