PCB technology targets automotive radar, high-bandwidth data

July 11, 2017 // By Christoph Hammerschmidt
Demanding applications such as high-bandwidth 5G communications or radar sensors for autonomous driving require specially developed printed circuit board (PCB) and interconnection technologies. They not only serve as interconnecting platform for the electronic components, but also provide functions such as antennas and filters. PCB company Austria Technologie & Systemtechnik AG (AT&S) has developed printed circuit boards that deliver the performance required for robust high-bandwidth communications at frequencies up to 80 GHz.

These technologies form the basis for high-performance radar components (long-range radar at 77/79 GHz) in driver assistance systems – an essential building block for autonomous driving.

High-frequency (RF) laminates are expected to see accelerating growth in the next few years, especially in vehicle radar applications and micro base stations. AT&S has evaluated materials and processes that are suited to these high-speed applications, primarily with the goal of minimizing performance losses. RF signals reflect off the PCB depending on various parameters, which means that the signal impedance changes. To prevent capacitive effects of this kind, all parameters have to be defined precisely and implemented with maximum process reliability. Critical factors for the signal impedance of high-frequency PCBs include the conductor path (trace) geometry, but particularly the layer structure and material used.

To achieve frequencies of up to 90 GHz, the dielectric constants (Dk) need to be brought below 3.0, and the loss factor (Df) to less than 0.001. For comparison, the corresponding values for standard FR4-grade quality are > 4 and > 0.015. Hence materials such as LCP, PTFE, polyamide or organic materials with special fiberglass and resin mixes are required. Losses at high frequencies can be further minimized during the manufacturing process by applying very thin copper foils with low roughness to the PCBs. AT&S sass it is able to offer asymmetric hybrid and sandwich structures (FR4 for the digital layer and PTFE for the high-speed layer) for PCB technologies up to frequencies of 80 GHz, for all kinds of different applications.