The Requirements for Printed Circuit Boards in Automotive Electronic Systems (1) Power & Energy Systems

Meta Description: Discover the key PCB design and manufacturing requirements for EV power and energy systems, including battery packs, BMS, on-board chargers, DC-DC converters, and traction inverters. Learn about high-voltage PCB design, thermal management, thick copper boards, and insulation standards.

Introduction

Power and energy systems serve as the core of electric vehicles (EVs), enabling the storage, conversion, and distribution of electrical energy that drives vehicle operation. Critical components such as battery packs, battery management systems (BMS), on-board chargers (OBC), DC-DC converters, traction inverters, and high-voltage junction boxes work in tandem to ensure efficient and safe energy flow. These systems operate under extreme conditions, handling high voltages ranging from 400V to 800V (and up to 1200V in advanced models) and large currents reaching hundreds of amperes. As a result, the design and manufacturing of printed circuit boards (PCBs) for these systems are pivotal to ensuring vehicle reliability, safety, and overall performance. This article delves into the specific PCB requirements, technical challenges, and emerging trends in EV power and energy systems.

Overview of EV Power & Energy Systems

EV power and energy systems consist of several interconnected modules, each with distinct functions but sharing common demands for reliability, safety, and thermal efficiency:

• Battery Pack & BMS: The battery pack stores electrical energy, while the BMS monitors cell voltage, temperature, and state of charge, balancing cells to maximize performance and lifespan.
• On-Board Charger (OBC): Converts alternating current (AC) from the grid into direct current (DC) to charge the battery pack, with efficiency directly impacting charging speed.
• DC-DC Converter: Steps down high-voltage power from the battery (typically 400V) to lower voltages (12V or 48V) to power auxiliary systems such as lights, infotainment, and sensors.
• Traction Inverter & Motor Controller: Converts DC from the battery into alternating current (AC) to drive the electric motor, a process critical to vehicle acceleration and efficiency.
• High-Voltage Junction Box: Safely distributes high-voltage power across the vehicle, incorporating protective mechanisms to prevent overloads or short circuits.
• Regenerative Braking Control: Captures kinetic energy during braking and converts it back to electrical energy for storage in the battery, enhancing energy efficiency.

PCB Design Requirements for Power & Energy Systems

To meet the demands of high-voltage, high-current operation, EV power system PCBs must adhere to stringent design criteria:

1. High Voltage and High Current Handling

The ability to manage large currents without overheating or voltage loss is fundamental. This requires:

• Thick copper layers: PCB copper thickness ranges from 2oz to 6oz (with 1oz equivalent to 35μm), and metal-core boards are often used for components like traction inverters to enhance current-carrying capacity.
• Wide traces and integrated busbars: Expanded trace widths and embedded copper busbars minimize resistance and reduce power loss, critical for high-current paths.

2. Insulation and Safety Standards

High-voltage operation demands robust insulation to prevent arcing and electrical hazards:

• Creepage and clearance distances: For high-voltage lines, these distances are typically ≥4mm–8mm to avoid insulation breakdown.
• Compliance with global standards: PCBs must meet IEC 60664 (for creepage/clearance), UL 796 (high-voltage certification), and IPC-2221 (general spacing rules), as detailed in Table 2.

3. Thermal Management

Excessive heat can degrade performance and shorten component lifespan. Thermal management strategies include:

• Thermal vias, embedded copper, and metal substrates: These features enhance heat dissipation from high-power components.
• High-Tg and low-CTE laminates: Laminates with a glass transition temperature (Tg) of ≥170°C and low coefficient of thermal expansion (CTE) resist warping under temperature fluctuations.

4. Multilayer & Hybrid Materials

Complex power systems require advanced PCB structures:

• 6–12 layer stack-ups: Common in power modules to separate power, ground, and signal layers, reducing interference.
• Hybrid materials: Combinations of FR-4 with high-frequency or ceramic substrates (e.g., for SiC/GaN inverter devices) optimize performance for specific components.

Table 1: Voltage & Current Levels vs. PCB Copper Thickness

EV System Component	Voltage Range	Current Range	Typical PCB Copper Thickness
Battery Pack / BMS	400–800V	200–500A	2–4 oz
On-Board Charger (OBC)	230–400V AC	10–40A	2–3 oz
DC-DC Converter	400V → 12/48V	50–150A	2–4 oz
Traction Inverter	400–800V DC	300–600A	4–6 oz or metal-core

Manufacturing Challenges

Producing PCBs for EV power systems involves several technical hurdles:

• Thick copper processing: Etching copper layers ≥4oz is prone to undercutting, requiring precise control to maintain trace accuracy.
• High voltage isolation: Balancing compact module design with the required creepage/clearance distances is challenging, as miniaturization often conflicts with insulation needs.
• Hybrid material lamination: Combining materials like FR-4 and ceramic or PTFE demands tight control over lamination pressure and temperature to avoid delamination.
• Reliability testing: PCBs must undergo rigorous thermal cycling, humidity aging, vibration, and high-voltage insulation tests to ensure durability in harsh automotive environments.

Table 2: PCB Safety & Insulation Standards

Standard	Requirement	Application in EV PCB
IEC 60664	Creepage & clearance ≥4–8 mm	High-voltage tracks in OBC/inverter
UL 796	High-voltage PCB certification	Battery pack, HV junction box
IPC-2221	General design rules for PCB spacing	DC-DC converter, traction inverter

Future Trends in EV Power PCB Design

As EV technology advances, PCB design is evolving to meet new demands:

• Wide Bandgap Semiconductors: Silicon carbide (SiC) and gallium nitride (GaN) devices, known for high efficiency and frequency, require low-inductance, low-loss PCB structures to maximize performance.
• Embedded Power Electronics: PCBs with embedded copper busbars reduce resistance and module size, improving energy efficiency.
• Advanced Thermal Solutions: Liquid-cooled PCB substrates are being adopted for inverters to handle higher heat loads from next-generation semiconductors.
• Integration & Miniaturization: Increasing integration of functions onto single PCB modules reduces system complexity and weight, enhancing vehicle efficiency.

Table 3: PCB Materials Comparison for EV Power Systems

Material	Tg (°C)	Thermal Conductivity (W/m·K)	Loss Tangent (Df)	Application Example
FR-4 (High Tg)	170–180	0.25	0.020	BMS, DC-DC boards
Rogers RO4350B	280	0.62	0.0037	Inverter control, radar
Metal-Core PCB	>200	2.0–4.0	N/A	OBC, inverter power stages

Conclusion

EV power and energy systems impose rigorous demands on PCB design and manufacturing, from thick copper layers and high-voltage insulation to advanced thermal management and hybrid material integration. As the backbone of safe and efficient energy delivery, these PCBs are critical to the performance of modern EVs. With the accelerating adoption of electric mobility, the need for high-performance, safety-certified, and thermally robust PCBs will only grow. Manufacturers that master these technologies will play a key role in driving the electric mobility revolution forward.