The invention relates to a heat exchanger, especially for motor vehicles, comprising a soldered heat exchanger network made of flat pipes (2,3) and corrugated ribs (1). A liquid and/or vaporous-type medium can flow through the flat tubes (2, 3) and air can circulate around the corrugated ribs. One corrugated rib respectively comprises two surfaces (4,5) which are arranged in an essentially parallel manner in relation to each other and which are connected respectively by an arch-shaped piece (6) which is soldered to a flat pipe, said arch-shaped piece comprising three sections (6a,6b,6c) which have different curvatures.