The Requirements for Printed Circuit Boards in Automotive Electronic Systems (5) Thermal Management & Comfort Systems

Meta Description: Explore PCB requirements for EV thermal management and comfort systems, including battery thermal units, PTC heaters, AC compressors, and lighting modules. Learn about thick copper PCBs, reliability, and environmental adaptation.

Introduction

Thermal management and comfort systems are vital components of electric vehicles (EVs), directly impacting battery efficiency, passenger comfort, and overall vehicle performance. These systems regulate temperatures across critical components—from maintaining optimal battery cell conditions to ensuring cabin comfort in extreme climates—and include modules such as battery cooling units, PTC (Positive Temperature Coefficient) heaters, AC compressor controllers, heat pumps, and climate control modules. Given their role in balancing energy efficiency and passenger experience, the printed circuit boards (PCBs) powering these systems must meet strict standards for power handling, thermal reliability, and environmental durability. This article explores the specialized PCB requirements, manufacturing challenges, and emerging trends in EV thermal management and comfort systems.

System Overview

Thermal management and comfort systems consist of interconnected modules, each addressing specific temperature or comfort needs:

• Battery Thermal Unit: Monitors and regulates battery cell temperatures (typically maintaining 25–40°C) to prevent overheating, optimize charging efficiency, and extend battery lifespan.
• PTC Heater: Converts electrical energy into heat to warm the cabin in cold climates, providing rapid heating without relying on waste heat from internal combustion engines (absent in pure EVs).
• AC Compressor Controller: Drives electric compressors to circulate refrigerant, enabling cabin cooling and dehumidification in warm conditions.
• Heat Pump: Enhances energy efficiency by transferring heat from the environment (or vehicle components) to the cabin, reducing power consumption compared to traditional heaters.
• Lighting & Seat Control Modules: Manage ambient lighting, heated/cooled seats, and steering wheel heaters, contributing to passenger comfort through precise temperature regulation.

PCB Design Requirements

To support the reliable operation of thermal management and comfort systems, PCBs must adhere to targeted design criteria:

1. Medium Power Handling

Many modules in these systems operate at moderate to high power levels, demanding robust current-carrying capabilities:

• Thick copper layers: PCBs for heating and compressor modules typically use 2–4 oz copper (1 oz = 35μm). This thicker copper minimizes resistance and power loss, ensuring efficient energy conversion in high-current circuits (e.g., PTC heaters with 1–5 kW power output).
• Optimized trace design: Wide, short traces and copper pours reduce resistive heating, preventing PCB overheating even during peak power operation.

2. Environmental Durability

These systems often operate in harsh conditions—exposed to moisture, vibration, and temperature fluctuations—requiring PCBs to withstand extreme environments:

• Moisture resistance: Protection against condensation (common in climate control systems) and water ingress (for under-hood modules) via conformal coatings or sealed housings.
• Vibration tolerance: Structural reinforcement to survive road-induced vibrations, ensuring solder joints and components remain intact over vehicle lifetimes.

3. Thermal Reliability

Effective heat dissipation is critical to prevent PCB degradation and maintain component performance:

• Metal-core PCBs (MCPCBs): Used in high-heat zones (e.g., PTC heater controllers, compressor drivers), MCPCBs feature a metal substrate (aluminum or copper) that enhances thermal conductivity (2.0–4.0 W/m·K), rapidly transferring heat away from components.
• Thermal vias: Strategically placed vias connect hot components to metal cores or heatsinks, accelerating heat dissipation from critical areas like power semiconductors.

Table 1: Thermal Management Modules & Power Levels

Module	Power Range	PCB Copper Thickness
Battery Cooling Unit	500–1500W	2–3 oz
PTC Heater	1–5 kW	3–4 oz
AC Compressor	500–1000W	2–3 oz

Manufacturing Challenges

Producing PCBs for thermal management and comfort systems involves unique technical hurdles:

• Mixed Power & Control Circuits: Integrating high-power circuits (e.g., heater drivers) with low-voltage sensor/control circuits on a single PCB requires careful isolation. This prevents electromagnetic interference (EMI) from high-current paths disrupting sensitive temperature sensors or control signals.
• Moisture Resistance: Applying conformal coatings (e.g., acrylic or silicone) evenly across complex PCB layouts—including under components—demands precise application techniques to avoid coverage gaps that could lead to corrosion.
• Vibration Resistance: Meeting automotive vibration standards (e.g., ISO 16750-3) requires PCBs with high glass fiber content and thicker substrates (1.6–2.0mm), which can complicate drilling and lamination processes due to increased material rigidity.

Table 2: Environmental Requirements for Comfort Systems

Environment	Requirement
Temperature	-40°C ~ 125°C
Humidity	95% RH
Vibration	ISO 16750-3 compliance

Future Trends

As EVs evolve, thermal management and comfort system PCBs are adapting to meet new efficiency and integration demands:

• Heat Pump Integration: PCBs are being designed to support multi-functional heat pump systems, combining heating, cooling, and battery thermal management on a single board to reduce size and energy loss.
• Intelligent Climate Systems: AI-driven control algorithms are being integrated into PCBs, enabling adaptive temperature regulation that balances passenger comfort with energy efficiency (e.g., zone-specific cabin heating).
• Eco-friendly PCBs: Manufacturers are adopting low-carbon production processes and recyclable materials (e.g., lead-free solders, halogen-free laminates) to reduce the environmental footprint of thermal system PCBs.

Table 3: PCB Technology for Thermal Systems

Technology	Benefit
Metal-Core PCB	High thermal conductivity
Thick Copper PCB	High current handling
Conformal Coating	Moisture protection

Conclusion

Thermal management and comfort system PCBs play a critical role in balancing EV energy efficiency and passenger experience. These boards require thick copper for power handling, metal-core substrates for thermal dissipation, and robust environmental protection to withstand moisture, vibration, and extreme temperatures. As EV technology advances, future PCBs will focus on integration, intelligence, and sustainability, ensuring thermal and comfort systems remain efficient, reliable, and eco-friendly in the next generation of electric vehicles.