Thermoplastic high-performance polymer supplier Lanxess has developed a new concept for radar sensors with integrated thermal management that will benefit autonomous driving.
Though there is still some distance to go, driver-assistance systems are increasingly set to become a key feature of future generations of cars, and 360° monitoring of the vehicle’s surroundings is enabled by — among other things — radar waves. The radar sensors are an essential component for distance control, lane change monitoring, collision avoidance, and blind-spot monitoring systems.
The sensors must be dust- and water-proof and consequently are designed as fully enclosed systems. However, this makes it difficult for heat to be effectively dissipated from the inside, which, in turn, can impair the performance of the electronics and durability of the sensors. “This is why we developed a concept that allows heat to be dissipated by means of thermally conductive plastics in combination with metallic cooling elements,” says Gregor Jaschkewitz, application developer in the High Performance Materials (HPM) business unit at Lanxess. “The individual sensor components are assembled using integrated snap fits and hot rivets, a process that is much less costly and time-consuming than using screws.”
Low component count
This new concept from Lanxess involves the following individual components: A front cover (radome); radar absorber; printed circuit board (PCB), including antennas; and a back cover with integrated cooling element. The radome faces away from the vehicle and must be made from a plastic offering a high degree of transmission for the radar waves. Polybutylene terephthalate (PBT) is well-suited for this application because it has a low dielectric constant (Dk) and loss factor (Df).
The back cover is the most complex part of the entire assembly. It is manufactured using a plastic-metal compound (hybrid) technique with polyamide (PA) 6 coupled to a metallic cooling element. This enables engineers to leverage the design freedom of the injection molding process, allowing them to integrate features such as reinforcement and cooling ribs as well as slots for connectors and the strain-relieved attachment of cables.
Most importantly, however, the surface of the metallic cooling element can be overmolded with thin sections of plastic. “The heat generated from the electronic components of the PCB can be efficiently dissipated from the whole assembly through these plastic areas. This effect is supported by a thermally conductive Durethan BTC PA 6 injection-molding grade,” says Jaschkewitz.
PA 6 is also extremely tough and ductile. Another benefit of the hybrid design is that the metallic cooling element shields the electronics inside the radar sensor against electromagnetic radiation, which means that its function is not impaired by external radiation. The assembly can be sealed with O-rings or sealing lips created in a two-component injection molding process.
Tailor-made material mix
With most concepts for plastic radar sensors, the radome and back cover have always traditionally been made from thermoplastics that can be welded to each other to create a fully enclosed assembly. This generally meant that the same plastic had to be used for joining the two components. “Our approach, however, places fewer restrictions on the choice of materials and makes it easier to use tailor-made compounds,” says Jaschkewitz.
Lanxess believes that sensors for driver assistance systems will offer a wealth of opportunities for its Durethan PAs and Pocan polyesters (PBTs). “We want to benefit from the huge growth potential in this application segment and advance technological innovation with our own ideas, like the concept for radar sensors,” said Dr. Christopher Hoefs, a global application development expert in HPM. For example, the business unit also recently unveiled a concept for the modular design of charging connections for electric vehicles.