PCB Laminates for Automotive Radar Antenna Modules Under Different Environmental Conditions

Abstract

Radar systems have become more important in the automotive field, especially for autonomous driving. A crucial part of the hardware is the antenna which is connected by lines to the radar chip. These components are usually built on printed circuit boards (PCBs) that have to fulfill high automotive requests under all environmental conditions. As a consequence, material properties are a critical factor for the functionality and reliability of systems, like-wise new materials are available in the market. Fourteen interesting materials of different classes [polytetrafluorethylene (PTFE), polyphenyl ether (PPE), epoxy-based resin, and liquid crystal polymer (LCP)] were evaluated in this work at their initial state, while heating to 125 °C and after storage with 85% relative humidity (RH) at 85 °C. It is shown that there are new candidates for millimeter wave applications beyond the PTFE materials. Nevertheless, it is necessary to test each material individually for its properties and optimize the parameters in simulation because they differ from the values in the datasheet. In addition, the properties depend on the used line setup, in this work microstrip lines. For the measurements, multiline thru-reflect-line (TRL) calibration and ring resonators were used and give a good overview by loss and effective permittivity depending on the environmental condition.