The invention relates to an illumination device (1) comprising at least one preferably ceramic substrate plate (2), at least one luminous element (3) arranged on a front side (A) of the substrate plate (2) in particular at least one light emitting diode (LED) (3), and at least one preferably metallic heat sink (4) connected, in particular adhesively bonded and/or soldered, to a rear side (B) of the substrate plate (2) over a large area, wherein the coefficients of thermal expansion of substrate plate (2) and heat sink (4) differ at least by the factor 1.5, in particular by a factor greater than 2. The heat sink (4) has at least one preferably linear recess (6) on its side facing the rear side (B) of the substrate plate (2).