Benno Spinger

High power LED subassemblies for automotive front light application

A high power LED platform for automotive front lighting is described. Based on small footprint ceramic LED packages customized designs can be realized in a highly flexible way. The diverse automotive applications have different requirements in terms of optical performance, i.e. assembly tolerance and package density, but also regarding the thermal performance of the boards, which are used as substrates for the LEDs. For a future design of a low beam function with a distributed multi cavity reflector concept the optical tolerances are evaluated which are required to form a beam which provides the sharp cut-off line needed to illuminate the road without glaring the oncoming traffic. For such optical concept an overall positioning tolerance below 100μm is required. The tolerances of the LED assembly process on advanced PCB solutions, including reflow soldering, are investigated and compared with alternative assembly solutions. Additionally, the thermal performance of the LED subassemblies is investigated by T3Ster measurements and finite element simulations. The advantage of special Cu-IMS is demonstrated compared to Fr4 based and Al-IMS solutions.

LED Matrix light source for adaptive driving beam applications

An adaptive driving beam consists out of many LED segments which are switched on and off or dimmed to adjust the beam to the specific driving situation, e.g. in case of oncoming traffic to avoid glaring. LED Matrix light sources have a great advantage for automotive adaptive front lighting application: No mechanical parts are required to shape the beam. They have the potential to spread from high end car platforms to the high volume cars within the next years but compact and cost saving solutions are prerequisite to make this development happen. In the paper we evaluate different architectures of LED light engines for adaptive driving beams. We discuss optical concepts to realize the required angular resolutions for the matrix segments. We present the beam performance of a solution using a matrix of 3×11 ceramic LED packages assembled on one board with one near die collimator as primary optic and a projection lens as secondary optic. An angular resolution of 1.5° is achieved for the individual addressable segments of the high beam on the street. Due to the dense LED array the electrical routing is performed on two layers to realize individual addressability of the LEDs. The potential board technologies, i.e. double layer IMS boards or advanced Fr4 boards with copper inlay, are discussed for this kind of LED matrix application. The thermal performance is evaluated by FE simulation. The solution realized in our application is a special IMS with two electrical layers and vias through the metal core. In dependence of the required beam up to 50W thermal load is dissipated.