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NOVEMBER 2025 I SMT007 MAGAZINE 79 attach to solder fatigue at capacitor leads. Wide- bandgap semiconductors improve efficiency but increase sensitivity to parasitic inductance, requir- ing short interconnects and multilayer busbars 8 . Thermal management is critical. Junction tempera- tures can exceed 200°C in aggressive duty cycles. Hence, power modules are often attached using silver sintering or pressure contact methods for improved longevity. Heatsinks must combine low thermal resistance with mechanical compliance to accommodate differential expansion 9 . DFR considerations extend to transient overvolt- age protection, gate drive timing, and thermal inter- face materials. Design tools now integrate electro- thermal co-simulation, allowing engi- neers to predict hot-spot formation or thermal runaway before first builds 10 . OEMs and Tier 1s employ vehicle digi- tal twins to define key environmental/ mechanical/thermal stressors from extended mission profiles, and system reliability is a sum of sequential and additive stressors 11 . Board-level tests such as highly accelerated life testing (HALT) and power cycling are also increasingly standard 12 . DC-DC Converter: Silent Support System While the traction battery powers high-voltage systems (e.g., drive motor, compressor), a DC-DC con- verter steps voltage down, often from 400–800 V to 12–48 V, to sup- ply lights, infotainment, sensors, and safety modules. It also keeps the low- voltage auxiliary battery charged. Despite its secondary role, its reli- ability is paramount because a failure here can disable safety-critical sys- tems like braking or lighting. Inter- nally, the converter resembles a min- iaturized inverter with its own power stage, controller, and isolation trans- former. Size and weight constraints have driven the use of multilayer ceramic capacitors (MLCCs), planar magnetics, and integrated switching controllers. However, compact designs raise ther- mal and EMI challenges. DFR practices include derating of passive compo- nents, thermal isolation of control circuits, and PCB layout rules to minimize parasitic coupling. Isolation barriers must withstand long-term, high-potential stress, especially in humid or contaminated envi- ronments 13 . Redundant converters or failover strat- egies are gaining interest in commercial vehicles and automated platforms where uptime is mission- critical. Robust fault detection algorithms are now being embedded in digital controllers, helping iden- tify incipient degradation without relying solely on external sensors 14 .