The present invention relates to a composite assembly of plastic (1, 3) and metal films (2.1, 2.2) which can be used for the interconnection and connection of light-emitting diodes (LEDs) (5). For this purpose, a flexible printed circuit board is provided, to which at least one radiation source is applied and which consists of a film system. The flexible printed circuit board has a thermal connection (6) to a heat sink (4) and the film system is composed at least of an insulating carrier layer and a metal film. The insulating carrier layer is opened at the locations at which the thermal connection to the heat sink is produced, and the metal film is subdivided into different sections.