Automotive PCB: The Ultimate FAQ Guide

This guide answers all your questions on automotive PCB.

Whether you want to learn about specifications, features, classification, or design criteria, you will find all information you need right here.

So keep reading to learn more.

What Is An Automotive PCB?

A printed circuit board serves an electrical and mechanical function in any device.

It mechanically supports components while connecting them electrically via means of conductive traces.

An automotive PCB generally refers to any printed circuit board in a vehicle that controls an electronic function.

You find many electronic functions in a vehicle such as the fuel management system and the antilock brake system.

A vehicle can have over a hundred electronic control units thus employing several automotive PCBs.

The automotive PCB serves to improve the safety and efficiency of modern vehicles.

 automatic PCB

automotive PCB

Why Do You Employ Automotive PCB?

You find employing automotive PCBs in your vehicles essential for the following reasons:

  1. Automotive PCBs enhance efforts geared towards environmental improvements such as fuel conservation, reduction of tail gas and efficient use of gasoline.

Consequently, these efforts have led to the development of electric vehicles in the automobile industry.

  1. Automotive PCBs used in air bags, dashboard cameras, radar and infrared monitoring and even autonomous driving have lowered accident rates.
  • You note the realization of great convenience and comfort in modern vehicles are credit to automotive PCBs.

You can play audio and video in your vehicles as well as navigate, use air conditioning and mobile communication.

What Are Types Of Automotive PCBs?

There are several types of automotive PCBs depending on various factors such as the area of application and the performance needs.

You find the following common types:

Rigid Automotive PCBs

You find these boards furnished from FR4 such that they cannot be bent or twisted.

Rigid automotive boards are a staple in screen displays on the dashboard such as that of the reverse camera.

 rigid automotive PCB

rigid automotive PCB

Flex Automotive PCBs

Flex Automotive PCBs employ plastic substrates that can bend or twist using material such as polyamide or polyester films.

These boards are adaptable to curved devices allowing their use in corners and around bends.

 flex automotive PCB

Flex automotive PCB

Rigid-Flex Automotive PCBs

A rigid-flex automotive PCB combines aspects of both the rigid and flexible board.

Part of the board is rigid with another part flexible allowing use in areas such as a vehicle’s lighting systems.

flex automotive PCB

flex rigid PCB

HDI Automotive PCBs

The type of automotive PCB has finer lines and gaps, and higher wire density per unit area and connection density.

You can furnish more components on an HDI automotive PCB allowing you to effectively employ them in miniaturized devices.

You will find HDI automotive boards in the infotainment systems of vehicles such as media players.

LED Automotive PCBs

These board type consist an aluminum substrate that is useful in heat dissipation.

You find their application in car headlights, indicators and brake lights.

Where Do You Use Automotive PCBs?

An automobile contains various electronic control units which employ automotive PCBs.

Common application areas of the automotive PCB include:

  • Air Conditioner System PCB: Allows you to regulate the temperature inside your car when too hot or cold.
  • Airbag PCB: Deploys airbags as a safety measure via a sensor that releases static power in case of an accident.
  • Anti-theft PCB: Uses a unique circuit to raise an alarm that safeguards the automobile against theft.
  • Antilock Brake System PCB: Useful in emergency situations when steering by preventing the locking of wheels.
  • Audio-Video System PCB: Car audio and video display units utilize this circuit board to connect components.
  • Battery Control System PCB: Allows you to monitor battery health in the vehicle while also offering battery protection.
  • DC/AC Power Converters PCBs: Transform high voltage from the battery into low value voltages for various features including headlights and wipers.
  • Digital Display PCB: provides you different visuals of car parameters including engine temperature, speed and oil pressure.
  • Engine Control Unit (ECU) PCB: Determines the internal mechanisms of the engine while regulating fuel injection and ignition spark.
  • Electronic Mirror Control PCB: Encompasses a pair of DC motors that guide the movement of the vehicle’s mirrors.
  • Engine Timing System PCB: Harmonizes the crankshaft and camshaft movements in a vehicle ensuring efficient engine performance.
  • Global Positioning System PCB: Accurately determines the geographical location of the vehicle allowing tracking and mapping.
  • Ignition System PCB: Enables spark ignition by generating a spark via electrode heating which ignites a mixture of fuel and air.
  • LED Lighting System PCB: Comprises microchips through which electricity passes illuminating the LED such as in headlights.
  • Automotive Power Relay PCB: Automates electrical power enabling you to switch electrical circuits at given intervals.
  • Automotive Radar PCB: Supplements vision-based sensor systems in avoiding collisions and obstacles reducing accident rates.
  • Signals and Lamp Control PCB: Controls all lighting and signal systems of a vehicle allowing visibility and informing other road users.
  • Steering System PCB: Assist in power conversion of steering wheel movement to guide the wheels on the road.
  • Transmission Speed Sensor PCB: Determines the transmission’s gear ratio by employing a pair of sensors in conjunction with the powertrain control.

What Substrate Options Do You Have For Your Automotive PCB?

When fabricating an automotive PCB, you can employ the following substrate options:

Ceramic Substrate Board

The ceramic substrate encompasses co-fired alumina and aluminum nitride at high temperatures.

You employ these boards in the engine area because they can tolerate extreme temperatures.

Heavy Copper PCB

You furnish the exterior and inner layers of automotive PCBs with thick copper finding use in security and signaling systems.

Heavy copper boards display great endurance resisting extremes in temperature, frequency, and current.

Typical boards have a copper thickness ranging between 25 and 50 micrometers.

Alternatively, heavy copper PCBs, have a thickness range of between 150 and 200 micrometers.

figure 5 heavy copper PCB

 Heavy copper PCB

Metal Core PCBs

Metal core PCBs employ an aluminum base layer over which you build up the board.

The base layer serves as a heatsink, making it ideal for applications requiring heat transfer.

You note the improvement of board electrical insulation and thermal conductivity when using the metal core boards.

figure 6 metal core PCB

Metal core PCB

These circuit boards are suitable for the antilock braking system (ABS).

PTFE PCBs

You employ polytetrafluoroethylene (PTFE) PCBs in safety systems and radar applications due to their impressive high frequency performance.

 PTFE PCB

PTFE PCB

What Are The Fundamental Requirements For Automotive PCBs?

When furnishing automotive PCBs, you identify the following fundamental requirements:

High Reliability

You view automotive reliability form two angles.

First is the service life, which refers to how long you expect the control units and electronic components to perform.

Second is environmental resistance, which refers to how well automotive control units and electronic components behave in severe environments.

Automobile PCBs have an average service life of about 12 years, during which time you can replace non-core parts and components.

You note that climate and environmental conditions have an impact on vehicles during the application process.

This includes factors such as extreme cold and heat, as well as extended sunshine and rainfall.

Additionally, automotive PCBs have to contend with environmental changes resulting from thermal dissipation by operating electrical components.

These PCBs also have to overcome, electromagnetic interference, humidity, acid fumes, vibrations and shocks, and current surges.

Light Weight And Miniaturization

Making the automotive PCB and its components lightweight and miniaturized results in fuel savings.

For instance, the electronic control unit size has since shrunk at least four times since the turn of the century.

The aspects you identify in establishing light weight and miniaturization requirement are: area reduction, thinness, layer counts and density improvement.

What Are The Performance Properties Of Automotive PCBs?

Modern car technologies combine conventional approaches with cutting-edge scientific technologies for its mechanical and electronic equipment.

Several parts rely on electronic devices that perform different duties, resulting in the use of automotive PCBs.

You can classify automotive PCBs into two categories based on the substrate material: organic resin-based and inorganic ceramic-based PCBs.

Ceramic-based PCBs have a great heat resistance with exceptional dimensional stability, making them ideal for engine systems in environments with high-temperatures.

However, these ceramic-based PCBs have poor manufacturability, resulting in expensive circuit board fabrication.

Resin-based PCBs find use in modern automobiles, thanks to newly improved resin substrates with enhanced resistance to heat.

Automotive PCBs employing different substrate materials find use in separate areas of a vehicle.

Each circuit board is responsible for implementing different functionalities.

What Tests Can You Perform On Automotive PCB?

Ensuring your automotive PCB is highly reliable is essential and thus requires you to subject the board to tests.

Some of the tests you can perform on an automotive PCB are:

Thermal Cycling Test (TCT)

A thermal cycling test seeks to establish an automotive PCB’s resistance capability when subjected to alternating temperature extremes.

You employ five levels denoted A to E identifying the vehicle section with the low and high temperature values as follows.

  • A – Within the automobile body (-40 oC, 85 oC)
  • B – Vehicle Chassis (-40 oC, 125 oC)
  • C – Above the engine (-40 oC, 145 oC)
  • D – Parts along Transmission (-40 oC, 155 oC)
  • E – Within the engine (-40 oC, 165 oC)

Thermal Shock Test (TST)

Automotive PCBs find use in high-temperature environments, posing extra strain on heavy copper PCBs, due to both external and internal heat.

You therefore need to enhance the heat resistance you’re your automotive PCBs.

A thermal shock test requires you to immerse automotive PCBs, at high temperatures of about 260°C or 288°C, in solder paste.

You do this three times each taking about ten seconds thereafter ensuring the board is free of bumps, lamination, and cracks.

The thermal shock test is especially essential now that you employ lead-free soldering that requires high soldering temperature.

Temperature-Humidity Bias (THB) Test

Automotive PCBs must withstand a variety of challenging conditions, including humid environments and wet conditions.

Consequently, you need a THB test that can also evaluate PCB Conductive Anodic Filament (CAF) mobility.

CAF only happens between adjacent vias and wires, between adjacent vias, and between adjacent wires and layers.

The insulation levels reduce and can result in shortcuts in such instances. Distance between vias, wires, and layers can help you evaluate insulation resistance.

What Features Highlight Automotive PCBs?

You identify the following features for automotive PCBs:

High-Frequency PCBs

Automotive predictive emergency braking systems or anti-collision, relies on PCBs to send high-frequency microwave signals.

As a result, it is better to use low-dielectric-loss substrate materials such as PTFE (polytetrafluoroethylene).

Unlike regular FR-4 as a substrate material, PTFE employs unique manufacturing processes.

 high frequency PCB

High frequency PCB

In the case of via drilling, for instance, you require a specific drilling speed.

Heavy Copper PCBs

Due to their power and high electronic density, vehicles generate more heat.

Growth of hybrid and all-electric vehicles has led to the demand for more advanced power transmission systems.

Consequently, you find the need to furnish systems with larger current carrying capability and higher heat dissipations.

heavy copper PCB

Heavy copper PCB

You enable this by raising the copper thickness or leads for the automotive PCBs and integrating the boards in multi-layer configuration.

Component Embedment

Automotive PCBs with embedded components enhance assembly density and shrink the total size of the device.

There are numerous embedded automotive PCB manufacturing possibilities based on component embedment processes as follows:

  • You employ wave soldering or conductive paste to attach SMDs upon milling the groove.
  • You begin with thin-film SMDs first attaching them to internal circuits.
  • You attach the thick-film components on a ceramic base.
  • Packaging employs resin.

HDI Technology

Vehicles require HDI automotive PCBs in the same way as smart phones do in terms of entertainment and communication.

Using HDI technology requires use of micro-via drilling, electroplating, and intricate connectivity methods as a result.

What Are Some Of The Challenges In Designing Automotive PCBs?

The utmost concern when designing automotive PCBs is safety. You find the following challenges when designing automotive PCBs:

High Voltages And Currents

Vehicle operations must contain boards capable of processing, converting, and distributing electrical parameters at many levels.

You note that this is due to the employment of high voltage and/or current for storage and charging.

Arcing can cause surface tracking concerns on automotive PCBs with high voltage.

Creeping and clearance distances that do not satisfy specified criteria, can contribute to arcing on high current boards.

Thermal Resistance

Automotive PCBs conducting high voltage and/or current frequently employ high-power components that produce excessive heat.

You therefore require good thermal management for your circuit board design.

What Design Guidelines Do You Follow In Designing Automotive PCBs?

A good automotive PCB design encompasses appropriate material, conformity to set standards and performance reliability.

The following guidelines will enable you to develop a good automotive PCB design.

Component Placement And Orientation

Placing and orienting components is critical in defining a board’s performance, dependability, and manufacturability.

You need to arrange identical components in the same orientation on the automotive PCB, making routing and soldering easier during assembly.

You optimize the assembly operation, by positioning all the SMD components on one board side. Alternately, you need to position all through-hole components on the top.

Signal Routing

You require thermal management for components absorbing in excess of 10mW or conducting over 10mA.

This also applies to power management components employing ground or power planes for heat movement.

You need to restrict power and ground planes to the internal layers ensuring they are symmetrical to avoid bending.

You should also shield sensitive signals from noise sources and control impedance.

Use two to four vias per layer for interlayer connections transporting high current.

Multiple vias enhance reliability while reducing resistive and inductive losses, and thus boosting thermal conductivity.

Remember to always employ as short and straight traces as possible.

Order And Separate Components

You first position larger components which are usually the most significant before proceeding to smaller ones.

It is prudent to also separate analog from digital components utilizing different sections of the automotive PCB.

The height of the components is also significant such that you need to avoid placing tall components alongside short ones.

Tis helps to avoid poor solder connections.

Thermal Management

First, you need to pinpoint the components dispersing the most heat.

Factors affecting the operating temperature of a component include trace thickness, layer count, thermal routes continuity, and board surface.

Thermal vias and copper planes help you to enhance thermal conductivity.

You can decrease the operating temperature by using numerous ground and power planes with direct via connections to the heat sources.

Where several components generate lots of heat, spread them uniformly throughout the board to avoid hot spot formation.

Alternatively, if few components are responsible locate them in the board’s center, to facilitate uniform dissipation of heat in all directions.

Apply Design Rule Check (DRC)

Performing a DRC allows you to discover any flaws that may not match manufacturing standards or other application specific needs.

Conducting DRC continuously during the design process is advisable as it helps to capture flaws early.

Follow Automotive Design Standards

Knowing and following applicable automotive PCB standards ensures you come up with a quality board for a specific function.

Follow Good Grounding Rules

Grounding is another key factor when developing automobile printed circuit boards.

You have to build vehicles’ electrical systems to use chassis grounding since they do not come into touch with the earth.

How Do You Orient Inductors In Your Automotive PCB?

Inductance manifests when a pair of inductors or even PCB wires come close together.

Current in one circuit (A) creates a magnetic field which drives current (B) in the other circuit.

Inductance alignment closely associates with mutual inductance distribution.

Thus, changing the direction of circuit B results in a current loop parallel to circuit A’s magnetic lines.

You should orient inductors vertically to do this, as it reduces mutual inductance.

When laying out inductors for automotive PCBs the following guidelines are important:

  • You need to employ sufficient space for inductors.
  • Set the alignment of the inductor at right angles to reduce crosstalk between them.

How Do You Conduct Lead Coupling In Your Automotive PCB?

If you closely pack leads, it alters coupling and creates possibility of mutual inductance.

The input and emitter’s antenna matching networks, and receiver’s resonant channel are the most sensitive components of an RF circuit.

You need to have the return current path very close to the main current path.

Additionally, having a reduced radiation field helps to minimize the current loop area.

When you ground the area under leads, you achieve the best low impedance path.

This restricts the loop area by factoring the thickness of the dielectric times length of the lead.

What Is Through-hole Capacitance In Automotive PCBs?

The major problem you need to address with an RF circuit is circuit characteristic impedance, which encompasses electronic components and connectivity.

Having a very thin copper film is tantamount to having an inductance wire.

Furthermore, the combination of a copper layer and neighboring leads can produce distributed capacitance.

Additionally, you will experience inductance and capacitance characteristics as the leads pass through via holes.

Capacitance between bottom copper and copper at the thru-hole pad edge accounts for the majority of through-hole capacitance.

The cylinder of metallized through holes is also another factor that affects through-hole capacitance.

Since parasitic capacitance usually only contributes to a low signal edge in high-speed digital communications, it has little impact.

The most significant effect of through holes is the parasitic inductance induced by connectivity.

Is Grounding Important In Automotive PCBs?

Grounding is a public reference voltage that provides power to all system components over a low-impedance channel.

You can balance all electric fields using grounding which develops an exceptional shielding scheme.

Direct current travels through a low impedance path at all times. Likewise, high-frequency current flows through the lowest impedance in the first minute.

Return current attempts flow into the grounding region below the leads for conventional PCB with leads above the ground plane.

Following that, the split grounding region causes a slew of noises, which amplifies crosstalk via current accumulation or magnetic field coupling.

Consequently, you need to maintain ground integrity as much as feasible, or the return current will cause crosstalk.

Furthermore, protective wire is common in circuits posing difficulty in the creation of continuous ground or with sensitive circuits requiring shielding.

You can maximize shielding effect, by placing grounding through holes at wire terminals or along the wires.

Do not combine protective wires with return current path leads, as this will result in forward crosstalk.

You have to consider the grounding area near the antenna ensuring it isn’t exactly beneath the monopole antenna.

In summary, you need to follow the grounding and filling design principles mentioned below:

  • Provide a continuous grounding region with low impedance.
  • Applying a through-hole array, connect a pair of terminals of filling to the ground.
  • Connect copper-coated lines to the ground in close proximity to circuits where copper coatings are superfluous.

Use grounding through-holes for multilayer board configurations.

Can You Employ 3D CAD Modelling For Automotive PCBs?

Yes, you can.

The creation of a precise 3D model of an automotive PCB is a critical enabler for accurately forecasting the design mechanics.

However, 3D CAD modeling of PCBs capturing all board layers, components, traces, and vias is expensive and takes time.

You can however use simple 3D models instead, which encompass preliminary simulations of airflow and thermal performance.

You need to understand the defined airflows, temperatures, and mechanical stress of the automotive PCB to thwart failures.

Presently, you can generate a detailed 3D CAD models for your automotive PCB layouts using design automation software.

The automatic production of the CAD model, streamlines and accelerates the design process, cutting the waiting time from days to hours.

Why Is Thermal Analysis Important For Your Automotive PCB?

To ensure functionality and safety, automotive PCBs need to have the highest design robustness possible.

A key aspect in this regard is ensuring that heat will not be a factor in the circuit board’s failure.

Thermal analysis is particularly useful when it comes to analyzing cooling concepts for efficient performance of your automotive PCB.

You identify two key elements that influence the thermal performance of your automotive PCB:

Component Power

You find some components with continuous constant voltage and current applied to them and others whose operation is intermittent.

These duty cycles are specific to the automotive PCB greatly influencing thermal efficiency.

Electronic Module Environment

Until recently, you found automotive PCBs in fairly stable thermal conditions, such as the dashboard. Nonetheless, factors such as space concerns, harness wire length and location have led to placement of automotive PCBs in unfavorable locations.

It may be unclear whether a location is inhospitable e.g. the exhaust manifold, however you need to consider the use-case scenario.

You have to furnish automotive PCBs to higher levels of robustness and reliability to endure the changing car technologies.

How Do You Conduct Structural Analysis Of Your Automotive PCB?

You identify temperature variations and vibrations as the main causes of stress in electronic systems such as automotive PCBs.

Stress affects the structure of an automotive PCB thereby requiring you to factor in during design.

Thermal Stress

Temperature fluctuations and differences in material thermal development cause structural stress.

A microcontroller on powering heats up causing chip expansion, with the automotive PCB heating up at a slower rate.

The fact that the chip and the circuit board expand at different rates from the temperature effect creates thermal stress.

Due to this growing differential, the board’s solder joints strain and can result in crack formation on repetition of the cycle.

Vibration Stress

Vibration testing was previously done by employing harmonic sine sweep approaches.

You positioned the PCB on a vibration table before initiating shake you gradually increased or decreased at a single sinusoidal frequency.

Currently, you test this by employing stress fatigue simulation.

You imitate real-life vibration by employing numerous frequencies acting simultaneously in a more random pattern.

What Standards Do You Employ For Automotive PCBs?

There are many standards put forward by different governing bodies that are applicable to automotive PCBs. Some common standards are as follows:

  1. Standards by the Automotive Electronics Council focusing on component functionality and reliability of automotive PCBs including:
  • AEC-Q100 which provides failure test qualifications for IC chips on automotive PCBs.
  • AEC-Q101 stipulates failure test qualifications for discrete semiconductors on automotive circuit boards.
  • AEC-Q102 specifies failure test qualifications for discrete optoelectronic semiconductors used in vehicle PCBs.
  • AEC-Q104 guides the test qualifications for failure of multichip modules on automotive circuit boards.
  • AEC-Q200 provides qualification tests for failure of passive components on automotive boards.
  1. Standards by the Association Connecting Electronics Industries (IPC) focusing on the design, manufacture and testing of automotive PCBs as follows:
  • IPC-6011 defines the generic specification of performance for an automotive PCB.
  • IPC-6012DA describes the test processes and tolerances for automotive rigid PCBs.
  • IPC-6013D outlines the performance specifications of flex and rigid-flex automotive PCBs.

For all your automotive PCB needs, contact Venture now.

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