How to select automotive PCB-to-wire harness connectors

An automotive wiring harness routes electrical power and signals between various vehicle components. Within this system, PCB-to-wire harness interfaces use connectors to link discrete wiring bundles with board-mounted electronics.

This article explores the fundamentals of PCB-to-wire harness interfaces and outlines connector electrical performance requirements across vehicle platforms. It also highlights the importance of mechanical stability, environmental resilience, and standards compliance in connector selection.

The building blocks of a PCB-to-wire harness interface

As shown in Figure 1, automotive manufacturers integrate PCB-to-wire harnesses across a wide range of electronic control units (ECUs), including engine and transmission controllers, airbag systems, infotainment platforms, telematics modules, and body electronics.

Figure 1. An automotive wiring harness with sealed multi-pin connectors is designed for power and signal routing across vehicle subsystems. These harness-side plugs mate with PCB-mounted headers at critical interface points. (Image: Asif Khan)

These harnesses — and their interfaces — form the critical connection between PCB-mounted electronics and the vehicle’s electrical system.

Each interface brings together three primary components:

Printed Circuit Board (PCB): The board houses and links electronic components for various functions, including powertrain control, safety systems, and infotainment.
Wiring Harness: This organized bundle of wires distributes power and signals throughout the vehicle, linking sensors, actuators, and control units.
Connectors: These components join harness wires to the PCB, enabling secure, reliable, and easily serviceable electrical connections.

As shown in Figure 2, interfaces operate through wire-to-board connectors mounted on the PCB. Harness-side plugs, with wires terminated using crimp contacts and secured in a connector housing, mate with these PCB-mounted connectors. Once mated, the housing plugs into a header or socket on the PCB, completing the circuit.

Figure 2. A 12-pin male automotive PCB electrical wire harness connector, highlighting a typical interface used in automotive applications for reliable power and signal transmission. (Image: Wiring-Connector.com)

This common configuration enables bidirectional transmission of power and signals between the vehicle’s wiring network and the PCB. Typical examples include relaying sensor inputs to control modules, supplying current to actuators, and transmitting data between telematics systems and central processors.

As modern vehicles incorporate more high-speed communication protocols, such as CAN, LIN, FlexRay, and automotive Ethernet, connector selection must also account for signal integrity, shielding requirements, and electromagnetic compatibility.

Electrical performance requirements across vehicle platforms

PCB-to-wire harness interface connectors must support varying electrical loads without introducing failure risks. Current and voltage ratings should match the demands of specific applications such as infotainment systems, advanced driver-assistance systems (ADAS), and battery management systems (BMS). These ratings help prevent overheating, arcing, and degradation of long-term performance.

Increasing electronic complexity in modern vehicles often results in higher pin counts and more I/O connections per module. Connector density is therefore a critical electrical design factor, especially where space is limited and signal integrity, current capacity, and electromagnetic compatibility (EMC) performance must be maintained.

Electrical requirements vary across internal combustion engine (ICE), hybrid, and electric vehicles (EVs). EVs often operate at 400V to 900V, compared to 12V systems in ICE vehicles and 48V to 400V in hybrids. These voltage ranges can vary depending on the vehicle architecture and specific subsystem requirements. Connectors used in EV platforms typically require tighter EMC compliance, improved insulation, and greater creepage and clearance distances to manage high-voltage safety and suppress electromagnetic interference (EMI).

To ensure reliable operation, connectors should exhibit low and stable contact resistance, ensuring consistent power and signal transmission. High insulation resistance and adequate dielectric strength in connector materials are also critical to prevent leakage currents and electrical breakdown, especially in high-voltage systems. Shielding, proper grounding, and controlled impedance within the connector design help minimize EMI and radio frequency interference (RFI) on data lines.

Designing for mechanical stability and vibration resistance

PCB-to-wire harness interface connectors are routinely subjected to vibration, shock, and thermal cycling. To ensure long-term reliability, manufacturers should select connectors with proven mechanical stability and appropriate mating cycle ratings. Although many interfaces are connected once during production, some may be mated and unmated during service, diagnostics, or module replacement.

To prevent vibration-induced loosening, automotive manufacturers should incorporate connectors with robust locking features such as board-lock clips, blade-and-spring designs, or dual-beam contacts. As shown in Figure 3, the connector’s size and form factor should fit the available space on the PCB and within the vehicle’s mechanical envelope, while also accommodating the wire gauges used in the harness to ensure reliable crimping or soldering.

Figure 3. Designed for space-constrained automotive applications, the TE Connectivity NanoMQS sealed PCB-mount connector features a compact footprint and high vibration resistance for ECU, ADAS modules, and sensor interfaces. (Image: TE Connectivity)

Material and environmental considerations for harsh automotive conditions

PCB-to-wire harness interface connectors must withstand extreme temperatures, moisture, and chemical exposure. Components should be rated for full automotive operating ranges, typically from –40°C to 125°C. Materials such as PBT, PPS, or PA66-GF25 offer high thermal stability, while gold- or nickel-plated contacts resist corrosion caused by humidity and oxidation.

As shown in Figure 4, sealed connectors for under-hood and exterior applications should feature high IP67, IP68, or IP69K ratings, along with elastomeric gaskets made from silicone or EPDM, to prevent water and dust ingress.

Figure 4. JAE MX60A Series waterproof PCB-mount connectors for high-density automotive applications, such as engine ECUs and PCUs, are designed for secure wire harness integration under harsh environmental conditions. (Image: JAE)

In ICE and hybrid powertrains, engine compartments often contain oil, fuel, and other aggressive chemicals, requiring connector housings made from PEEK or similarly durable polymers. In electric vehicles (EVs), PCB-to-wire harness interface connectors may be exposed to moisture and thermal stress; however, the absence of fuel and oil reduces the need for chemically resistant materials in certain areas. Nevertheless, exposure to coolants — used in the thermal management of batteries and power electronics — can still present chemical compatibility challenges.

Connector housings are typically molded from flame-retardant polymers such as PA6, PA66, PP, ABS, or PBT, which provide mechanical strength and resistance to heat, impact, and environmental aging. Contact elements are commonly made from copper alloys, such as brass or bronze, and plated with tin, nickel, or gold to enhance conductivity and corrosion resistance. Seals and gaskets formed from rubber or elastomers, such as neoprene, silicone, or EPDM, help maintain ingress protection in harsh conditions.

Connector design and automotive industry standards

PCB-to-wire harness interface connector designs must prevent unintentional disconnection and incorrect mating to ensure reliable connections. Polarized shapes, secondary locks, and keyed interfaces help ensure proper alignment, improve serviceability, and reduce the risk of failure under shock or vibration.

Engineers should also select connectors with the appropriate number of contacts and pin pitch to meet circuit-level electrical and spatial requirements. Mounting methods — such as through-hole, surface-mount, or panel-mount — should be selected to match the PCB layout and mechanical constraints of the assembly process.

To ensure safety, reliability, and system interoperability, connectors must meet applicable automotive standards, such as LV214, USCAR, or ISO specifications. These standards define performance thresholds for vibration resistance, sealing, current-carrying capacity, and environmental durability. Notably, EVs may introduce additional requirements for EMC, high-voltage compliance, and creepage and clearance distances.

Summary

Automotive PCB-to-wire harness interface connectors must support a wide range of electrical, mechanical, and environmental demands. These crucial components ensure reliable power and signal transmission across ECUs, from infotainment to ADAS and powertrain systems. Selection criteria span current and voltage ratings, mating durability, environmental resilience, and compliance with industry standards.