Fabrication and evaluation of LED-embedded ribbons for highly flexible lighting applications in rooms

Abstract

We have developed very flexible and lightweight LED-embedded ribbons in which LED-mounted printed circuit board (PCB) pieces are mounted and soldered to ribbons with the copper wires of power lines to apply them to the complicated three dimensional shapes of ceilings, walls, and furniture in rooms and provide higher levels of safety during earthquakes. Since it has been difficult to integrate LEDs in flexible ribbons and not only mount them on flat substrates but on bendable ribbons, we developed a new structure for LED-embedded ribbons and their fabrication process using a reel to reel mounting machine. A 2-cm wide ribbon with copper power lines on both sides was first constructed for the fabrication process of LED-mounted ribbons and then 5 × 20 mm LED mounted PCB pieces were mounted and soldered to the power lines of the ribbon. The ribbon was pulled under an optimal tension of 3.16 N to flatten the ribbon in the mounting process and the PCB pieces were pushed onto the ribbon with a rib height of 5 mm to strongly connect the pieces to the ribbon. The LED-embedded ribbon we constructed was 1.2 m long and very lightweight because it only weighed 7 g/m. The fabricated device had enough luminance of 96 lx for home and office lighting and could be installed on complicated surfaces such as adhering it to ceilings and the edges between ceilings and walls because our LED ribbon could be bent to a diameter of 5 mm. Our LED-embedded ribbon structure and assembly tool should provide new types of highly bendable and light-weight lighting for complicated three dimensional surfaces and safety during earthquakes.