The right materials are essential to achieve the desired sensor electrical performance, especially in many more demanding, high performance applications. Part 1 showed the performance impact of different sensor materials on infrared (IR) optical sensors. Radio frequency (RF) sensors also provide some interesting examples of a material’s impact on sensor performance.
With expanding RF applications in 5G, the radar systems that are an integral part of Advanced Driver Assistance Systems (ADAS) in automobiles and other high frequency systems, sensor and systems designers require materials with:
- Balanced dielectric properties
- Electromagnetic compatibility and/or protection from electromagnetic interference (EMI)
- Excellent dimension stability
In addition to meeting the performance requirements, these materials are also important to achieve regulatory compliance. For demanding automotive applications, RF sensors require superior mechanical properties and resistance to commonly used automotive chemicals and:
- EMI shielding to eliminate crosstalk
- Radar absorption to reduce cavity resonance
- Thermal conductivity for heat management
Sabic, a company that supplies resins for RF sensors, provides a variety of compounds to achieve the performance objectives of different portions of an RF sensor. Figure 1 provides an example of the material requirements in four different sections.
Figure 1. Material requirements for different radar sensor sections.
In this design, the front plate or radome requires a material that is radar transparent at 20-100 GHz. In addition to the company’s LNP™ THERMOCOMP™ compound that is chemical resistance with rigidity and low warpage, it offers ULTEM™ resin that is radar transparent and also provides high temperature resistance, weatherability and dimensional stability.
The middle plates require radar absorbing materials with shielding at 20-100 GHz. This section could use an LNP™ STAT-KON™ compound for radar absorbing, or LNP™ FARADEX™ compound for EMI shielding or LNP™ KONDUIT™ compound for thermal management.
For the antenna, control chip or printed circuit board (PCB), a NORYL™ SA resin provides low dielectric loss.
The back cover requires EMI shielding and mechanical strength. For this portion, an NP™ FARADEX™ compound for EMI shielding or alternatively an LNP™ THERMOCOMP™ compound with chemical resistance, rigidity and low warpage or NORYL™ resin with chemical resistance, low moisture and warpage might be considered.