A substrate for mounting electrically-powered light radiation sources, e.g. LED sources, includes a base layer of electrically-insulating material, such as PET, and a contact layer of electrically conductive material, e.g. copper. The contact layer includes a mounting area for a light radiation source having opposed anode and cathode terminals, including two portions with a gap therebetween. Therefore, the light radiation source may be mounted bridge-like across gap, with anode and cathode terminals soldered to respective soldering surfaces provided in the one and the other of said two portions of the mounting area. The latter portions include respective solder flow blocking formations including fork-shaped apertures in contact layer leaving base layer uncovered. The fork-shaped apertures have a web portion and prongs extending from web portion towards said soldering surfaces.