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72 SMT007 MAGAZINE I JUNE 2026 real-world performance can drift over time. NREL has noted that grease-based TIMs can suffer from application problems, pump-out, and dry-out, and that in-situ performance may be worse than supplier datasheet values. 14 NREL also reports that improved TIM performance can materially reduce thermal resistance in compact electronics. 15 If a TIM pumps out, dries out, cracks, or loses contact pressure, the result is higher thermal resis- tance and higher junction temperature. That can reduce semiconductor lifetime, accelerate solder or sinter fatigue, and change switching behavior. In practical terms, what goes wrong may begin as a few extra degrees and end as a large reliabil- ity loss. This is one reason EV power electronics teams are paying closer attention to gels, pads, graphite systems, phase-change materials, and other alternatives, each with its own balance of thermal performance, compliance, aging behavior, and assembly tolerance. High Voltage Makes Cleanliness and Insulation a Materials Problem As EV platforms move toward 800 V architectures and charging systems push similar voltage ranges, contamination and moisture become more danger- ous. Residues that might be tolerable in lower-volt- age electronics can contribute to leakage current, electrochemical migration, dendritic growth, tracking, and insulation breakdown when bias, humidity, and field strength rise together. The Global Electronics Association's white paper on charging station electronics highlights high voltage, humidity, contamination, and thermal extremes as key stressors in outdoor charging systems. 16 Recent APEX EXPO work has also focused on high-voltage temperature-humidity- bias behavior and protective measures for printed boards and coatings. 17 This is important because the consequences can be intermittent and hard to diagnose. A charger, inverter, or converter may pass routine checks and still fail in humid service. A board may appear elec- trically sound until contamination, condensation, and voltage interact in the field. For EV electronics, materials such as laminates, solder masks, coat- ings, sealants, and cleaning chemistries are part of the insulation system, whether designers label them that way or not. PFAS: Useful Materials, Hard Questions PFAS-related materials are now part of the EV reliability discussion for two reasons. First, PFAS chemistry has been widely used because fluori- nated materials offer chemical resistance, thermal stability, dielectric performance, low surface ener- gy, and durability in coatings, seals, wire insulation, processing aids, fluids, and related applications. The EPA has noted that fluoropolymers offer fire resistance and oil-, stain-, grease-, and water-repel- lency, and are used in sectors such as electronics and automotive. 18 Second, PFAS are under growing regulatory and market pressure due to concerns about persistence and associated environmental and health risks. The EPA and OECD both describe PFAS substitution as a major ongoing challenge, and ECHA has continued advancing the EU-wide restriction process. 19,20,21 If PFAS are removed carelessly, the replacement material may have lower dielectric strength, higher moisture uptake, poorer chemical resistance, lower thermal endurance, worse friction and wear behav- ior, or lower long-term stability. In an EV environ- ment, that can mean reduced insulation margin, swelling, cracking, softening, fluid incompatibility, shortened seal life, or coating performance loss. PFAS substitution is therefore not only a compli- ance issue, but also a design validation issue. 22 What are the alternatives? There is no single universal replacement, making this a difficult topic. OECD work on coatings, paints, varnishes, lubricants, and hydraulic oils points to non-PFAS alternatives such as silicones, hydrocarbon and ester-based fluids, mineral oils, synthetic esters, polyalphaolefins, certain waxes, acrylics, ure- thanes, epoxies, and ceramic or sol-gel-based sys- tems, depending on the function being replaced. 23 In dielectric and thermal-fluid applications, ester and hydrocarbon families are often discussed as PFAS-free options, though OECD notes that equiv- alent performance is not always established and substitution barriers remain significant. 20 In coat- ings, non-fluorinated silicone, epoxy, polyurethane, sol-gel, and plasma-deposited systems may work for some functions, but each comes with tradeoffs in repellency, processability, durability, service tem- perature, or repairability. 21 The practical takeaway is that PFAS substitution