Introduction
Printed circuit boards (PCB) play a pivotal role in the functioning and performance of automotive electronics. From powertrain systems to ADAS, infotainment and lighting, PCBs can be found enabling various functions. The harsh under-the-hood environment along with increasing electronics complexity impose stringent requirements on automotive PCBs. In this article, we will take a look at key PCB applications in vehicles, critical design considerations and specialized PCB types used in the automotive industry.
PCB Applications in Automotive
Some major application areas using PCB technology in modern vehicles:
Powertrain Control
- Engine control unit
- Transmission control module
- Battery management system
- Traction inverter & converter
ADAS Systems
- Camera modules
- Radar PCBs
- LiDAR electronics
- Vision processing units
Infotainment Head-units
- Navigation system
- Audio amplifier
- Telematics gateway
- Display graphics module
Body Control
- Lighting/luminaire PCBs
- Door control module
- HVAC control
- Central gateway ECU
Instrument Clusters
- Odometer
- Driver information display
- Telltales and warning lights
Security Modules
- Immobilizer PCB
- Central locking ECU
- Blind spot detection
PCB Design Challenges in Automotive
Designing PCBs for automotive applications brings unique challenges:
High Vibration/Shock Loads
- Vibration from engine and road noises.
- Shock from bumps and unequal road surfaces.
Wide Temperature Range
- Under-the-hood temperature up to 125°C.
- Cold temperature down to -40°C.
Electromagnetic Interference
- Switching noise from motors and actuators.
- RF interference from transmitters.
High Voltages
- DC bus voltage upto 650V in electric vehicles.
- Fast transients like load dump.
Mixed Signal Circuits
- Combination of sensitive analog and noisy digital circuits.
Safety and Reliability Critical
- Rigorous product validation needed.
- Adherence to ISO26262 functional safety standard.
Key PCB Design Considerations
To meet the demanding automotive environment, certain design practices are followed:
Component Selection
- Automotive grade components rated for extended temperature range.
- Parts qualified based on AEC-Q101 standard testing.
Layout Design
- Minimum clearance and creepage distance as per ISO 6469-3.
- Safety critical layout separation and partitioning.
Power Integrity
- Robust power distribution network design.
- Protection against voltage transients.
- Effective grounding.
Signal Integrity
- Controlled impedance routing for high-speed buses.
- Effective EMI and noise filtering.
Thermal Management
- Suitable dielectric materials like polyimide for higher temperature rating.
- Thermal vias/slots for heat dissipation.
Vibration Resistance
- Component bonding, underfill and encapsulation techniques.
- Board stiffening elements like aluminum baseplate.
Conformal Coating
- Paraxylene, acrylic, polyurethane or epoxy coating.
- Protection against dust, moisture, chemicals.
Safety Standards
- Compliance to ISO 26262 Functional Safety standard.
- Adherence to MISRA coding guidelines.
Reliability Testing
- Industry standard validation as per AEC-Q100, AEC-Q101.
- Accelerated testing – temperature cycling, humidity, HASS etc.
Types of PCBs Used in Automotive
Different types of PCB technologies and constructions are leveraged to meet the demanding automotive application requirements:
Rigid PCBs
- Conventional FR-4 glass epoxy rigid PCBs.
- Higher Tg variants like FR-4 High Temp for thermal reliability.
- Halogen-free and flame retardant materials.
- Metal core boards for thermal management.
Flexible PCBs
- Single, double or multilayer flex circuits.
- Suit applications with space constraints or movement.
- Polyimide material for flexibility at higher temperatures.
Rigid-Flex PCBs
- Combination of rigid and flexible sections.
- Allows three dimensional routing.
- Used to interconnect multiple PCBs.
Metal Backed PCBs
- Insulated metal substrate (IMS) or metal core PCBs.
- Metal baseplate aids heat dissipation and EMI shielding.
High Frequency PCBs
- RF designs with precise impedance control and absorbers.
- Low-loss material substrates like PTFE.
- Synthetic heat sinks for power amplifiers.
New PCB Trends in Automotive
Emerging trends in automotive PCB technologies include:
HDI PCBs
- High density interconnects to integrate more functionality.
- More routing layers, microvias and thinner dielectrics.
High Thermal Conductivity Dielectrics
- Dielectrics with ceramic fillers for improved thermal dissipation.
Low Temperature Co-fired Ceramic (LTCC)
- Multilayer ceramic PCBs for demanding RF and power modules.
Additive Processes
- Additive fabrication to produce high aspect ratio fine features.
- Technologies like aerosol jet printing.
Embedded Passives
- Passives like resistors and capacitors integrated within the PCB.
- Saves space and improves electrical performance.
Panel Level Packaging
- Panel scale manufacturing vs single PCBs.
- Allows integration of PCB, ICs, passives etc.
Quality and Reliability Testing
- Higher reliance on automotive industry standards like AEC-Q100/101, IPC-A-610G Automotive Addendum.
- In-circuit and functional testing.
- Accelerated life testing.
Conclusion
From engine control units to ADAS cameras, PCBs have become indispensable in modern vehicles due to the electronics revolution. Automotive PCB design requires mastering signal integrity, robust power distribution, thermal management and mechanical reliability while meeting stringent industry standards. As automotive electronics complexity grows exponentially, innovations in PCB materials, high density integration, quality/reliability validation and panel scale manufacturing will be critical to realize future mobility visions.
FAQs
- What are some key factors driving increased electronics content in automobiles?
Demand for connectivity, infotainment, electrification, autonomous features is driving rapid growth in automotive electronics content.
- What is the typical temperature rating required for under-the-hood automotive PCBs?
Due to high temperature environment, under-the-hood PCBs must withstand temperatures of 105°C to 125°C.
- How does ISO26262 relate to automotive PCB design?
It provides an automotive functional safety framework with requirements traceability impacting PCB design validation.
- Which construction provides higher thermal conductivity – IMS or MC PCB?
Insulated metal substrate (IMS) has dielectric directly bonded to metal baseplate giving higher thermal conductivity than metal core PCB.
- What are some key board level reliability tests done for automotive PCB qualification?
Common reliability tests include temperature cycling, shock/vibration, humidity/bias, HTOL (high temperature operating life) etc.
The industrial sector has seen a tremendous boom in past decade when the demand in automobile exponentially increased due to rapidly growing automation technology. Today the automobile giants like Toyota, Honda, BMW, Ford and Tesla are producing such a high class automobiles and targeting specific consumer class that can buy such a marvelous piece of art of automation engineering. Besides mechanical engineering miracles we all know that brought the revolution in cars and automobile vehicles, the electronics engineering industry has now got involved extensively in automobile industry. Today’s automobile vehicle is a combination of true art of mechanical and electronics engineering. All of the aesthetics that we see in high class sports car like Lamborghini or Ferrari, or we see power control system in heavy loaded trucks like Caterpillar or Komatsu lifters, cranes etc we see that the control system working behind is based on some sort of Electronic Control System (ECS). And this ECS is founded on Special kind of Automotive PCB.
Applications of Automobile PCBs:
Like Caterpillar 797F mining truck has the electronic clutch pressure control, service break sensor, Engine sensor, ARC switch, service break, secondary break control, axle speed sensor circuit, position and steering sensor circuits. There are lots of other examples of general use consumer cars with impressive dashboard, with LED or LCD display, GPS and radar electronics embedded on dashboard, FM radio, automatic doors and locking systems, electronic relays to control fuel valves/solenoids, timer circuits for engine, Engine Control Unit (ECU) or Engine Control System (ECS) PCB modules, automatic mirror controller, Airbag controller, and front, rear and side LED light control and drive circuits for headlights, back lights and indicator lights respectively, car speed and acceleration sensor and display circuits, Car Battery Management system circuits, wireless key remote door locking system for car safety, air conditioning control etc.
The auto driver system in modern automobile cars is totally PCB based and highly sophisticated electronic circuits are functioning behind the scene. These PCBs are made pre-programmed for sensing the surrounding environment of car to detect obstacle around it in neat vicinity. This is commonly done by IR and Doppler radar system. The auto robot car driving system will take control of car brake, clutch and race and makes decision based on the inputs from surrounding and programming fed in the complicated automotive PCBs.
Although these automobile PCBs are powered by car batteries which is in most cases maintenance free batteries and all the car electronics is operated by this 12VDC battery system. The cabling and wire harness is laid inside the car along with fuses to prevent the electronics from over current or overvoltage surges.
Electric Vehicle:
Nowadays, we see in newspaper, electronic media and people talking about future cars that will run totally on batteries and no fuel or diesel will be required for car now. Yes this is true, scientist and engineers have come-up with a new invention in the battery system that these batteries will charge in the matter of few hours and will give backup to your care for many days. This system is just like our smart-phones that once charged in few hours will give back-up 2-3 days. But there are differences in this novel technology because some electric vehicle will give few days of back and mileage while other can gives battery charging power for weeks. Obviously, the technology of E-Vehicles or Electric Vehicle is not possible without Automotive PCBs. Although our discussion in previous section was just to power up the accessory car electronics and engine control while the fuel was still the diesel and oil, while here in this case the car is totally “electrified” completely eliminating the need of fuel or diesel.
Types of Automotive PCBs:
From our discussion above it is clear that the automotive PCBs should be something that will give the highest performance in terms of power dissipation, efficient heat transfer, long life cycle and robustness. Commonly if we open up the deck or dashboard of our cars we see a complex electronics and wiring inside with relays, fuses and sockets mounted and connecting various modules with each other. These Electronic components are all mounted on Rigid PCBs that are High Density Interconnect (HDI) PCBs, Heavy copper PCBs to allow high amount of current flow from car battery to accessory electronic, ceramic substrate PCBs to bear against harsh, stringent environment of car surrounding like car moving in deserts, forest, mountainous regions or running in hot sunny weather.
The aluminum based Metal Core PCBs (MCPCBs) are commonly seen in automotive electronics that consist of bright LED lights. These bright LED lights draw high current from battery and in turn gives high luminosity white light. Moreover the small motors hidden inside car body to control the cars fins, windows, side mirrors or any part that is moving, draws good enough current from battery. Hence the need of heavy copper PCB is required to provide least resistance path to the flow of current so as to protect/avoid PCB to melt down due to high temperature / heat generated by high currents.
There are flexible PCBs also found in car electronics front dashboard, connecting large LED, LCD display to the processor board, or connecting various electronic modules each other by flexible PCBs. Flexible PCBs are light weight and can be adjusted/flexed inside the small space available in car deck/dashboard. The combination of rigid and flexible PCBs called Rigid-Flex PCBs are also found in Automotive PCBs.
Rayming PCB Services for Automotive PCBs:
At Rayming PCB Our expertise in manufacturing automotive PCBs is vast. We assure high quality and robust PCB manufacturing services. Our PCBs are ISO 9001-2008 and UL certified, so you know they are reliable, durable that will last long. We are the one-stop shop for all your PCB manufacturing and assembly needs. Our proven reputation among our valued clients shows the quality product we deliver. Please send us the design specifications and details about your Automotive PCB at this email sales@raypcb.com
Future of Automotive and PCB Industry Together:
These two gigantic industries can change the shape of the automation industry. As we witness today that cars have been invented totally depending upon electricity and batteries and completely knocking out the need of fuel pumps. Now in future electric charging stations will charge your car like a smart-phone and your will then drive your car more “Energy efficiently” and more environment friendly. Having said that, the electronics PCB manufacturing and assembly industry is the Part and Parcel of automotive industry. It is just the matter of time that world would see these automotive PCBs being used as an integral part of every car’s engine electronics, as car’s accessories electronics and completely replacing mechanical fuel engines with electronic car engines and interface electric motors to drive your car effectively.
