Issue link: https://iconnect007.uberflip.com/i/1542458
52 SMT007 MAGAZINE I JANUARY 2026 merely add-ons but are vital to the system's overall efficiency, occupant safety, and comfort. Their inte- gration, however, introduces new stresses on con- nectors, insulation, and the broader vehicle electri- cal architecture 1,2,3 Packaging and Placement Challenges Unlike propulsion components located in dedicated enclosures or drive units, auxiliaries are scattered across the vehicle, such as on the firewall, under seats, near wheel wells, or deep in the engine bay. This introduces unique challenges: environmental exposure to road spray, salt, and debris; mechanical stress from vibration or crash events; routing com- plexity for high-voltage cables and cooling lines; and electromagnetic interference between adja- cent control units. Reports of field reliability issues have been doc- umented for water ingress,4 corrosion,5 and cable positioning bracket vibration wear6. As integration increases, many automakers are packaging com- pressors, heaters, pumps, and controllers into multi- function thermal modules. 7,8 This reduces harness length but increases the need for multi-domain co- design involving electrical, thermal, and mechanical engineers who must coordinate on layout, sealing, and test protocols. Thermal Loads and the Rise of Electrified HVAC One of the largest HV auxiliary loads in an EV is the air conditioning compressor.9 Electrically driven and often liquid-cooled, the compressor must deliver precise climate control without a combus- tion engine. In colder climates, the HVAC system may also rely on HV PTC heaters or heat pump sys- tems, which consume large amounts of energy and demand robust insulation and switching electronics.10 In one report, HV cabin PTC heater units failed due to internal electrical faults, exacerbated by repeated thermal cycling and humidity exposure, resulting in a loss of cabin heating and range reduc- tion.11 The efficiency and reliability of these HVAC elements is closely tied to the quality of thermal interface materials (TIMs), the robustness of solder joints in inverter modules, EMI shielding and power integrity in the compressor control electronics, and the use of hermetically sealed connectors and mois- ture-resistant potting compounds.12 Poor adhesion between a potting compound and HV PCBs can lead to voids that act as moisture traps, resulting in inverter board short-circuits. Harnesses, Contactors, and High Voltage Connectors The HV harness system is another critical element. It includes orange-insulated cables, shielding lay- ers, mechanical supports, and HV connectors, each of which must withstand not only 800 VDC but also tens of kilowatts of transient power. System design must manage creepage and clearance distances to comply with insulation standards such as IEC 60664 or ISO 17409, particularly when operating at 800V or higher. Challenges include arc fault pro- tection and fast fault detection, connector durability under temperature cycling, and resistance to mois- ture and chemical ingress in routed areas. Failures at connectors or terminals such as contact fretting, corrosion, or arcing, can lead to intermittent faults or complete subsystem shutdowns.13 A field failure example has been reported where the HV connector to the heater module developed micro-movement under vehicle vibration, resulting in arcing, terminal wear, and eventual open-circuit failure.14 Routing multi-kilowatt loads through con- fined vehicle spaces requires careful management of electromagnetic interference (EMI),15 thermal dis- sipation, and mechanical durability.16 As more com- ponents draw HV power directly from the traction battery, the harness becomes a critical backbone.