2.5 D LED: A Cost Efficient Solution for 3 D Signaling Lamps

After the first appearance of LED rear lamps, which employed mainly two-dimensional arrays of LEDs, the request of stylists and OEMs to have three-dimensional LED alignment has increased strongly. Development of more powerful LEDs and new packaging and assembly technologies now allows for a three-dimensional assembly of the LEDs, giving an impression of depth and enabling the LEDs to follow even extreme curvatures. This gives great customer satisfaction in terms of styling, but the disadvantage is that the cost for the three-dimensional LED alignment increases significantly. To counteract this development, we have developed a light guide technology approach (so-called 2.5 D) to combine a cost efficient LED assembly process with the flexibility of a 3 D arrangement of the light sources. Thus, we can use standard planar FR4 (Flame Resistant 4) LED printed circuit boards with arbitrary LEDs and do not depend on a certain assembly technology. Nevertheless, with the 2.5 D approach it is possible to follow virtually every 3 D shape. Even in situations, where the packaging density does not allow for today's 3 D solutions, our approach is feasible. In addition, it is possible to shape the light exits, to adjust the percentage of direct light in relation to indirect (reflected) light, or to change the size of the apparent light source. Thus, this technology offers additional possibilities to adapt the style to customer demands.