Automotive PCB Design

In the current automotive landscape, digitization has taken precedence, with an array of electronic features incorporated into vehicles, ranging from driver assistance systems to safety and convenience enhancements like backup cameras. This shift has resulted in numerous advantages, as it transfers a considerable portion of operational and safety responsibilities from drivers to the automotive systems themselves. These technologies heavily rely on circuit boards that facilitate monitoring, control, and drive for the mechanical systems, enabling various automotive functionalities. For this reason, adhering to essential automotive PCB design guidelines is crucial to meet the intelligent operational requirements of these advanced automotive systems.
There's a variety of aspects that go into automotive PCB design, from thermal to layout to safety considerations.

There’s a variety of aspects that go into automotive PCB design, from thermal to layout to safety considerations.

Essential Automotive PCB Design Standards

For automotive PCBs, designing for safety is paramount. As such, numerous automotive standards focus on the components and materials utilized, the quality of design and manufacturing, and the testing requirements for AV electronics boards and devices. It is absolutely essential for all stakeholders involved to be well-informed about these standards and diligently adhere to them to ensure the highest level of safety and reliability in autonomous vehicle technology. Below are some essential standards to be aware of.

Automotive PCB Design Standards and Regulations

IPC-6012D Section IPC-6012DA Description Fabrication/Assembly Step(s)
3.3 Introduces inspection procedures for uncovering defects in the printed circuit boards (PCBs) Visual/Automated Optical Inspection (AOI)
3.3.4 Specifies tolerances for lifted lands, pad, and plated through-hole (PTH) separation Hole drilling, plating
3.4.1 Establishes tolerances for drill hole sizes in the PCBs Hole drilling, plating
3.4.3 Specifies limitations on bow and flex in the PCBs Solder reflow
3.5 Defines quality standards for conductors in the PCBs and guides the inspection process PCB Stackup, AOI Details land quality standards and tolerance for defects in the PCBs Etching, visual/AOI Specifies quality standards for plated through-holes (PTHs) in the PCBs Hole drilling, soldering
3.7.3 Provides guidelines for solder mask thicknesses in the PCBs Solder masking
3.9 Outlines cleanliness quality control measures for fabrication and assembly of PCBs Fabrication and assembly quality control, finishing, Resistivity of Solvent Extract (ROSE) testing is required
3.9.1 Specifies requirements for board cleanliness prior to solder masking Fabrication quality control, and ionic testing is recommended
3.9.2 Directs the implementation of cleanliness testing after solder masking, soldering, and finishing Fabrication and assembly quality control, solder masking, soldering, finishing

IPC-6012DA Design Tips for Board Fabrication

IPC standards encompass specifications and guidelines applicable to circuit boards across diverse industries. One of the most important standards, the IPC-6012DA addendum to IPC-6012D, focuses on “ensuring the reliability of printed boards that must withstand the demanding vibration and thermal cycling environments of electronic interconnects within the automotive industry.” By adhering to these standards, engineers can gain assurance in their designs. Furthermore, contract manufacturers (CM) employ the manufacturing processes to ensure that the electronics and PCBs produced can reliably operate in the distinct and challenging automotive environment.

IPC-6012D Standards for Automotive vehicle design

Regulation   Description Key Area of Application Governing Organization
AEC-Q100 Establishes failure test qualifications for integrated circuits Ensuring reliability of integrated circuits Automotive Electronics Council (AEC)
AEC-Q101 Sets failure test qualifications for discrete semiconductors Ensuring reliability of discrete semiconductors Automotive Electronics Council (AEC)
AEC-Q102 Defines failure test qualifications for discrete optoelectronic semiconductors Ensuring reliability of optoelectronic semiconductors Automotive Electronics Council (AEC)
AEC-Q104 Specifies failure test qualifications for multichip modules Ensuring reliability of multichip modules Automotive Electronics Council (AEC)
AEC-Q200 Outlines failure test qualifications for passive components Ensuring reliability of passive components Automotive Electronics Council (AEC)
IATF 16949 Sets guidelines and requirements for quality management systems (QMS) in the automotive industry Ensuring high-quality product design and development International Automotive Task Force (IATF)
IPC-6011 Establishes generic performance specifications for PCBs Ensuring standardization in PCB design and manufacturing IPC – Association Connecting Electronics Industries
IPC-6012DA Defines tolerances and test procedures for rigid PCBs used in automotive systems Ensuring reliability of rigid PCBs in automotive applications IPC – Association Connecting Electronics Industries
IPC-6013D Specifies performance specifications for flex and rigid-flex PCBs Ensuring reliability of flex and rigid-flex PCBs IPC – Association Connecting Electronics Industries
SAE J3016_201401 Classifies automated driving systems Classifying vehicle types for automation Society of Automotive Engineers (SAE)
Below are some of the IPC-6012 design tips for board fabrication:

High Voltage Considerations

As we’ve mentioned, safety is of utmost importance when designing automotive systems, especially when designing EVs. One of the key factors to address is the presence of high voltages and currents. Vehicle system operations involve the use of high voltage, high current, or both for a variety of different electronic control units (ECUs). This necessitates the use of circuit boards that can efficiently handle, process, convert, and distribute electrical parameters at multiple levels. However, it is essential to be cautious, as high-voltage boards in automotive applications can be prone to surface tracking issues caused by arcing. Similarly, high current boards may face problems due to creeping and clearance distances not meeting standard requirements.

Automotive PCB Component Placement Design Tips

Component orientation and placement play a crucial role in determining a board’s reliability, manufacturability, and overall performance. To optimize the assembly process, consider the following approaches when placing components:

Lead Placement

Proper lead placement is also crucial to prevent undesirable magnetic coupling and the potential generation of mutual inductance. To ensure effective lead placement, consider the following points.

Thermal Management for Automotive PCB Design

Another critical aspect that demands attention is the thermal profile. In both high voltage and high current boards, there is a reliance on high-power components that generate significant amounts of heat. Furthermore the high voltage and current conditions may cause hot spots to arise on the board. Thus, effective management of thermal resistance becomes crucial in automotive designs to ensure the safety and reliability of the system. 

To effectively manage heat dissipation for components absorbing more than 10 mW or conducting over 10 mA, employ the following techniques for improved temperature control:

Techniques for improved temperature control in automotive PCBs 

Grounding Tips for Automotive PCBs

Implementing proper grounding rules is also crucial when designing automotive systems. To ensure effective grounding, all internal grounds should connect to a single point. Each PCBA (Printed Circuit Board Assembly) must have a single ground connection, and in the case of multiple boards, all ground connections should converge to a single point. For larger electronic systems, it is advisable to establish a single ground connection for each internal system, where all internal board grounds meet.

When implementing grounding techniques in your automotive design, consider the following guidelines:

Grounding techniques for automotive PCB design

Chassis Grounding

Since vehicles do not have direct contact with earth ground, it becomes essential to utilize chassis grounding techniques. This involves bonding all internal metallic elements of the system to a common point. For metallic enclosures, the enclosure itself can serve as this point. However, for other electronics systems like those with plastic enclosures, a chassis ground may not be present.

When it comes to chassis grounding, there should be only one connection from the chassis ground to the electronic system(s) that it serves as the safety ground for. Whether using the enclosure or mains neutral as the chassis ground, having a single connection enhances safety and reliability.

Preventing EMI Through Grounding 

Proper grounding techniques are also essential to prevent electromagnetic interference in your automotive PCB design. Below are some recommendations to ensure effective grounding:

RF Guidelines for Radiating PCBs

For automotive PCBs that require a receiver, transmitter, or other wireless capabilities, it is crucial to address challenges with radiating and wireless components. Incorporate the following tips into your design.

If you’re looking for CAD models for common components or reliable information on standards and design tips for automotive PCB design, Ultra Librarian helps by compiling all your sourcing and CAD information in one place. Working with Ultra Librarian sets up your team for success to ensure streamlined and error-free design, production, and sourcing. Register today for free.