Today’s manufacturers of automotive fleets and mass transportation systems are motivated to meet fuel efficiency and emission requirements, as well as market demands for reduced costs. e-Mobility (electro mobility or advanced mobility) refers to clean and efficient electric and hybrid vehicles that use electric powertrain technologies, in-vehicle information, communication technologies, and connected infrastructures.
e-Mobility efforts are gaining traction around the world. According to EURACTIV, Europe is making major gains:
Metros and tramways are electric and provide high-capacity, zero-emission public transport systems in many European cities. Likewise, about 80% of Europe’s mainline rail traffic is powered by electricity. Several EU member states are now pushing towards a 100% electrified rail network, with the potential to reduce the CO2 emissions of rail to zero if they achieve it.
And road transport is catching up. Last year, the number of electric vehicles (EVs) purring up and down the world’s roads surpassed two million. This may not seem a lot when set against the total number of cars on the road (which is probably in excess of a billion) but it does represent remarkable and sustained growth. EV sales climbed by nearly 40% in the US last year, while China has become the largest single market in the world for EVs and plug-in hybrids, with sales only expected to grow as government-backed investment presses on.
You can find Rogers’ advanced materials in a wide variety of eMobility platforms: power electronics solutions for electrical oil pumps and battery packs, high-frequency PCB laminates for electrical power steering and antennas, and gaskets and vibration management foams for airbag sensors and sound systems. Let’s take a closer look at the electronics inside these vehicles.
High frequency PCB substrates are found in Adaptive Cruise Control, Antenna Boosters, Automated Tolling Tags, Blind Spot Detection, Collision Avoidance and Mitigation, GPS, Rear Cross Traffic Alert, Telematics, and V2X Antennas.
Ceramic substrates are found in Air Conditioning Compressors, Battery (Fast) Chargers, Converters, Electrical Power Steering, Inverters, Liquid Heater PTC, Oil Pumps, Start-Stop Systems, and Vacuum Pumps.
Power distribution systems are found in AC-DC Converters/DC-DC Converters, Battery Modules, Motors, Power Steering, and Start-Stop Systems.
Active Safety Systems
New cars are increasingly equipped with robust crash avoidance technologies. These active safety technologies are enabled by innovative Advanced Driver Assistance Systems using sensor technologies, such as radar, to detect collisions.
Rogers’ Advanced Connectivity Solutions group provides high performance PCB laminates for 24 GHz and 77 GHz automotive radar sensor applications. The RO4000® and RO3000® series materials enable radar sensors to detect upcoming collisions to prevent road accidents. In addition, RO4000® high frequency circuit materials are successfully used in 24 GHz radar sensors for blind spot detection or rear cross traffic alert.
Forward collision warning, emergency brake assist, adaptive cruise control, and traffic jam pilots require radar sensors that operate in the 76-81 GHz range. RO3000® High Frequency Laminates have an excellent Dk tolerance of ± 0.04 and at this high frequency concerns with insertion loss are paramount. These laminates also offer an extremely low dissipation factor, ensuring the dielectric loss component of insertion loss will be very low.
Vehicle to vehicle (V2V) or vehicle to infrastructure (V2I) communications systems send information via dedicated short range at 5.9GHz (DSRC) or intelligent transportation system G5 (ITS-G5) and 3G/4G cellular network. Rogers’ high frequency materials help antenna´s and modules to achieve high performance and reliable connections between cars and infrastructure even at high speed and under harsh vehicle environments.
Power Connectivity and Distribution
As power from a battery is expensive, the challenge is to use the electric power as efficiently as possible. The primary inverter needs to minimize switching losses and maximize thermal efficiency. Auxiliary inverters are used to power vehicle electrification solutions. The range of the vehicle is directly related to the efficiency of these inverters.
Semiconductor-based power systems are able to optimize overall system cost, minimize power losses, increase power density, maximize power savings, extend mileage, and improve battery efficiency.
RO-LINX® busbars from the Power Electronics Solutions group focus on efficient power distribution and lower energy losses, increasing the range of electric vehicles. These laminated busbars provide a customized liaison between the power source and capacitors, resistors, integrated circuits (ICs), integrated gate bipolar transistors (IGBTs), or complete modules.
Within the circuit board, power substrates provide interconnections and cool components. curamik® ceramic substrates are designed to carry higher currents, provide higher voltage isolation, and operate over a wide temperature range.
Evolution in automotive electronic systems
Evolution of the electronic systems in automobiles and other vehicles is exciting to watch, and many technologies once associated with the military, such as radar systems, are becoming available to average drivers. For example, 24-GHz short-range-radar (SRR) systems are being offered more and more in car models around the world. But vehicle designers and manufacturers are also looking ahead to the greater resolution possible with 77- and 79-GHz automotive radar systems. And for that evolution in automotive electronic systems to truly take place, printed-circuit-board (PCB) materials are important building blocks that will enable the potentially much safer automobiles of the future.
Compared to 24-GHz automotive radars, systems at 77 and 79 GHz with their smaller wavelengths can operate with considerably smaller antennas. Because the Doppler shifts are more significant at millimeter-wave frequencies than at 24 GHz, these higher-frequency systems also more precisely determine distances and relative speeds between vehicles and other objects. The high resolution possible at 77 and 79 GHz also enables radar systems that can detect dangerous road-surface conditions, including the presence of ice.
Circuit Materials for Higher Frequency Automotive Radar Systems
Circuit materials for these higher-frequency automotive radar systems must meet a similar set of requirements as detailed in the previous Blog about 24-GHz automotive radar systems, but perhaps with even tighter tolerances for systems operating at 77 and 79 GHz. The consistency of relative dielectric constant (εr) across a circuit board, for example, is particularly critical at 77 GHz, where variations in dielectric constant (Dk) can translate into changes in the impedance of transmission lines, and changes in frequency. Such variations in frequency can result in wrong readings in an automotive radar system that can compromise the safety of the system. In general, variations in a circuit material’s Dk can cause variations in the impedance of a transmission line, which result in higher reflected energy, higher return loss, and higher insertion loss.
How RO4000 and RO3000 Materials match up
The benefits of our RO4000® PCB materials for 24-GHz automotive radar systems were highlighted in this blog post. For 77- and 79-GHz automotive radar applications, our RO3000® circuit materials bring their own favorable attributes for these millimeter-wave circuits. RO3003™ high-frequency laminate, for example, has been used to fabricate antennas in automotive adaptive cruise control (ACC) circuits at 77 GHz, where its tight Dk tolerance contributes to stable frequency operation even this high in the spectrum. RO3003 laminates exhibit a Dk of 3.00 at 10 GHz with Dk tolerance within ±0.04. Minimizing loss at these millimeter-wave frequencies is also important, due to limited available transmit and receive power at 77 and 79 GHz. Antenna-grade RO3003 laminates are characterized by a very low dissipation factor of 0.0013 at 10 GHz, indicating that dielectric losses will be low even at 77 and 79 GHz.
Any change in a circuit material’s Dk can affect performance
Because any change in a circuit material’s Dk can affect the performance of a millimeter-wave automotive radar system, another important material parameter to consider at these frequencies is the temperature coefficient of dielectric constant, or TCDk. This property describes how much the material’s dielectric constant will change with changes in temperature, when tested over a set range of temperatures in a short time period. And since a typical commercial vehicle may be subject to a wide range of operating temperatures, this is an important parameter for projecting the stability of a 77- or 79-GHz automotive system with changes in temperature. Some laminates, for example, can exhibit TCDk values in excess of +200 ppm/°C at certain temperatures and frequencies, resulting in large swings in the value of relative dielectric constant with temperature. The RO3003 material, which is engineered for higher-frequency antennas and other circuits, has a typical TCDk value of + 11 ppm/°C at 10 GHz and for temperatures from -50 to +150°C. This last part is important to note when comparing materials, since TCDk must be referenced to a range of test temperatures to be meaningful.
Maintaining mechanical stability
Since an automotive radar system must endure a wide range of operating conditions, mechanical stability with temperature is also important for maintaining reliability, especially in high-resolution 77- and 79-GHz systems. The RO3000 PCB materials such as RO3003 laminates are ceramic-filled polytetrafluoroethylene (PTFE) composites engineered for high electrical performance but also excellent mechanical stability over changing environmental conditions. The RO3003 laminates, for example, have a coefficient of thermal expansion (CTE) in the x and y plane of 17 ppm/°C that is closely matched to that of copper for excellent dimensional stability over a wide range of temperatures (-55 to +288°C). Through the material, in the z direction, the CTE is 24 ppm/°C to ensure high reliability of plated through holes (PTHs).
Good Thermal Conductivity
Another material parameter to consider for automotive millimeter-wave electronic applications, including 77- and 79-GHz radar systems, is good thermal conductivity. Although the power levels of higher-frequency circuits tend to be relatively low, any increase in the thermal conductivity of a PCB is to be recommended, since it will mean a reduction in the maximum temperature of a circuit board for a given amount of power handled by the PCB. Good thermal conductivity in the PCB material can also improve the thermal stability of the dielectric constant, since heat will be better distributed across the PCB material while minimizing any hot spots on the circuit board.
Although we have developed other PCB materials that can achieve the electrical performance levels required by 77- and 79-GHz automotive radar electronics, such as RT/duroid® 5880 laminate, the RO3000 materials combine outstanding electrical and mechanical characteristics with low cost, three key parameters needed to expand the emerging market for 77- and 79-GHz millimeter-wave automotive electronic systems. The RO3000 materials can also be processed using standard PCB methods developed for PTFE-based circuit materials, to minimize processing costs even at these high millimeter-wave frequencies.
Do you have a design or fabrication question? John Coonrod and Joe Davis are available to help. Log in to the Rogers Technology Support Hub and “Ask an Engineer” today.