Process to manufacture a brazed heat exchanger comprising a tubular tank and at least one tube inserted in a corresponding slot operated in the tubular tank, the at least one tube being in fluid communication with the tubular tank, the process being characterized in that it comprises the steps of: - providing a rectangular metal sheet having longitudinal edges (22, 24) of length equal to the length of the tubular tank, and transversal widths equal to the circumference of the tubular tank, the metal sheet being provided with notches operated on one longitudinal edge (22, 24) of the metal sheet, the notches being in the same number as the number of tubes to be connected to the tank, - providing a metallic flat separator having a main body with substantially the same dimensions as the internal section of the tubular tank (12, 14) and a tab extending from said body, and at two lateral arms (48, 50) symmetrically extending from the body and following the body so an indentation (52, 54) is being formed between the body and each lateral arm (48, 50), - forming in the metal sheet an elongated slot for the separator, - forming in the metal sheet an opening for the tab, - forming the metal sheet in a tubular shape so the longitudinal edges (22, 24) join and the notches close thus forming slots, and creating an edges-joining-line that is discontinued as being interrupted by the slots, and by the elongated slot, the opening for the tab being diametrically positioned from the elongated slot, - inserting the separator through the elongated slot and engaging the tab in the opening and engaging the wall of the tubular tank (12, 14) in the indentations (52, 54), the lateral arms (48, 50) staying outside the tubular tank (12, 14) thus maintaining the metal sheet in the tubular shape and further securing the positioning of the separator in the tubular tank (12, 14), - providing the at least one tube with brazing clad on at least one end of the tube, - engaging the end of the tube that is provided with brazing clad into the slot formed in the tubular tank, - brazing the assembly. - providing a rectangular metal sheet having longitudinal edges (22, 24) of length equal to the length of the tubular tank, and transversal widths equal to the circumference of the tubular tank, the metal sheet being provided with notches operated on one longitudinal edge (22, 24) of the metal sheet, the notches being in the same number as the number of tubes to be connected to the tank, - providing a metallic flat separator having a main body with substantially the same dimensions as the internal section of the tubular tank (12, 14) and a tab extending from said body, and at two lateral arms (48, 50) symmetrically extending from the body and following the body so an indentation (52, 54) is being formed between the body and each lateral arm (48, 50), - forming in the metal sheet an elongated slot for the separator, - forming in the metal sheet an opening for the tab, - forming the metal sheet in a tubular shape so the longitudinal edges (22, 24) join and the notches close thus forming slots, and creating an edges-joining-line that is discontinued as being interrupted by the slots, and by the elongated slot, the opening for the tab being diametrically positioned from the elongated slot, - inserting the separator through the elongated slot and engaging the tab in the opening and engaging the wall of the tubular tank (12, 14) in the indentations (52, 54), the lateral arms (48, 50) staying outside the tubular tank (12, 14) thus maintaining the metal sheet in the tubular shape and further securing the positioning of the separator in the tubular tank (12, 14), - providing the at least one tube with brazing clad on at least one end of the tube, - engaging the end of the tube that is provided with brazing clad into the slot formed in the tubular tank, - brazing the assembly.