During the process of manufacturing of home-brew PCBs you need to expose the photosensitive film with ultraviolet light. A cheap and low power solution can be found in UV led strips.
Building A UV Exposure Box
UV Exposure Unit for Hot Foil Pad Printing PCB etc, Screen Printing Exposing Machine FAST shipping with good quality
monspace: Single LED UV PCB exposure box
PCB exposure with UV Leds and digital countdown timer DIY – Cristian COPCEA
UV LED Light Box Elektor Magazine
UV Exposure Unit with built in PIC-based timer
LED UV exposure box
How to make a double sided ultraviolet exposure box for making PCB - Liviu Istrate
DIY Digital PCB Exposure Box
PCB UV Exposure Unit by RCWeinstadt, Download free STL model
How to make a double sided ultraviolet exposure box for making PCB - Liviu Istrate
UV Exposure Box Project – Part 2 – A BIT OF MYSTERY
Deluxe UV Exposure Unit With Vacuum Pump
UV LED PCB Lithography Exposure Unit
PCB exposure unit DIY