A heat exchanger is provided having a tube block having a plurality of essentially parallel tubes for carrying a temperature control fluid, wherein at least the ends of the tubes are connected to one another. In addition, the heat exchanger comprises at least one header box that is designed to receive a temperature control fluid from the tubes, wherein the at least one header box has an inside height that corresponds within a tolerance range to the height of the ends of the tubes and wherein the header box is placed over the ends of the tubes and is joined thereto in a material-to-material fashion.