Marten Sikkens

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.

Structured design method for automotive lamp reflectors

The design of critical automotive lamp reflectors, e.g. headlamps and fog lamps, is dominated by trial-and-error methods and rules-of-thumb, supported by optical ray-tracing tools like ASAP etc. In many cases these reflectors are designed by aiming small sections to construct the required illumination distribution, which is a time-consuming task and in which case it is very difficult to maintain a continuous reflector surface. The design method presented here is a more structured approach in which the total available front surface is divided in a few relatively large sections, each section designated to produce a certain part of the required light distribution. An optimizing algorithm is used to optimize the separate polynomial reflector sections in combination with a specific burner. In the final step, the separate sections are put together to form a more-or-less continuous reflector surface. Some iteration afterwards is still required because the intersection lines of the polynomial surfaces will generally change the original section boundaries. The design of a front fog reflector lamp is used as a carrier to demonstrate the approach. Three reflector sections are used to design a high-efficiency fog lamp. The light distribution has an excellent horizontal cut-off that basically meets the SAE requirements.