A method for bonding a capillary tube and a suction pipe for a regenerative heat exchanger, comprising the following steps: - positioning the capillary tube and the suction pipe in an alignment adjacent to each other; - feeding the capillary tube positioned adjacent to the suction pipe between at least one input pair of rollers that comprises a capillary tube roller and a suction pipe roller, wherein the rollers (30, 40) press the capillary tube and the suction pipe towards each other; - bonding the capillary tube with the suction pipe by means of a fiber laser welding head by directing a laser beam towards a welding position wherein an outer surface of the capillary tube contacts an outer surface of the suction pipe so that the outer surfaces are melted and bonded with each other; characterized by: - securing the capillary tube positioned adjacent to the suction pipe between a holding roller arrangement that comprises one suction pipe roller and two positioning rollers (51, 52) arranged opposite the suction pipe roller at sides of the suction piper roller, and wherein the centers of the positioning rollers (51, 52) are distanced (d) from each other by no more than 150% of a diameter of the positioning rollers (51, 52), wherein the suction pipe roller is biased towards the positioning rollers (51, 52), wherein the positioning rollers (51, 52) have a semicircular circumferential groove of a radius (r) corresponding to the radius (r) of the capillary tube and in which the capillary tube is accommodated, and wherein the suction pipe roller is biased towards the two positioning rollers (51, 52) such as to press the suction pipe towards the capillary tube, and wherein the welding position of the laser beam is located in a central position between the positioning rollers (51, 52); and - wherein the fiber laser welding head is a single mode laser having a spot diameter between 10 and 50 micrometers, wherein the laser beam is directed perpendicularly with respect to a surface passing through longitudinal axes of the capillary tube and the suction pipe. - positioning the capillary tube and the suction pipe in an alignment adjacent to each other; - feeding the capillary tube positioned adjacent to the suction pipe between at least one input pair of rollers that comprises a capillary tube roller and a suction pipe roller, wherein the rollers (30, 40) press the capillary tube and the suction pipe towards each other; - bonding the capillary tube with the suction pipe by means of a fiber laser welding head by directing a laser beam towards a welding position wherein an outer surface of the capillary tube contacts an outer surface of the suction pipe so that the outer surfaces are melted and bonded with each other; - securing the capillary tube positioned adjacent to the suction pipe between a holding roller arrangement that comprises one suction pipe roller and two positioning rollers (51, 52) arranged opposite the suction pipe roller at sides of the suction piper roller, and wherein the centers of the positioning rollers (51, 52) are distanced (d) from each other by no more than 150% of a diameter of the positioning rollers (51, 52), wherein the suction pipe roller is biased towards the positioning rollers (51, 52), wherein the positioning rollers (51, 52) have a semicircular circumferential groove of a radius (r) corresponding to the radius (r) of the capillary tube and in which the capillary tube is accommodated, and wherein the suction pipe roller is biased towards the two positioning rollers (51, 52) such as to press the suction pipe towards the capillary tube, and wherein the welding position of the laser beam is located in a central position between the positioning rollers (51, 52); and - wherein the fiber laser welding head is a single mode laser having a spot diameter between 10 and 50 micrometers, wherein the laser beam is directed perpendicularly with respect to a surface passing through longitudinal axes of the capillary tube and the suction pipe.