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count, or a different material selection creates a product that's easier to manufacture and more reli- able in the field. Final Thoughts Looking back over 40 years, I've learned that good engineering isn't about pushing every design to the limit of today's technology. I want to understand the product's requirements and make decisions that support them. The best designs achieve the right balance of performance, reliability, manufac- turability, and cost. Input from a capable fabricator can reduce total program cost by aligning material selection and fabrication methods with the actual functional requirements of the design. FLEX007 | F L E X C O N N ECT I O N S Why Thermal Failure Is Still the No. 1 Killer in Power Electronics Why do power electronics fail? There's a range of answers, from overvoltage and mechan- ical stress to poor assembly and environmen- tal exposure. If you ask your favorite AI search engine for an answer, you'll get a pretty simple response: excessive temperature leads to com- ponent degradation, material breakdown, and eventual failure. In a sense, that's true, but it's oversimplified and incomplete. The real issue is thermal management failure at the system level. Heat is still the number one killer, and most of the time, you don't even realize it's there. The Hidden Thermal Bottlenecks I don't think engineers are ignoring heat. They're ac- tually misjudging where the heat is. We tend to focus on obvious hotspots: power devices, MOSFETs, and IGBTs. We add heatsinks, fans, maybe even liquid cooling. But here are some hidden bottlenecks: • Interfaces between materials • Solder joints with poor thermal conductivity • Die attach layers that trap heat • PCB dielectric materials that resist heat flow • Copper thickness that spreads current—but not heat—effectively BY C H A N D R A G U PTA , R E M T EC These bottlenecks are subtle resistances in the ther- mal path, and those small resistances compound. Heat just needs a place where it can't escape fast enough, and that's where degradation begins. Why PCB-based Designs Hit a Ceiling Traditional PCB materials, especially FR-4, were never designed for high-power thermal perfor- mance. They were designed for manufacturability, cost efficiency, and electrical insulation. Second- ary to that was thermal conductivity. In low- to moderate-power systems, this works fine. But as power densities increase, especially in EV, aerospace, and RF applications, we start to see a hard limit. You can only push so much heat through a material that fundamentally resists heat flow. At that point, no amount of heatsinking can compensate for what's happening inside the structure. Engineers hit a ceiling, so they work to optimize the cooling system, but the real bottleneck is em- bedded in the substrate itself. BELOW THE SURFACE Continue reading here. Every time I review a design, I find myself coming back to this simple reminder: Just because you can doesn't mean you should. It's a lesson that has served me well throughout my career, and one that's just as relevant today as it was when I first entered this industry. I-CONNECT007 Dan Skweres is a senior applications engineer for Flexible Circuit Technologies. AUGUST 2026 I I-CONNECT007 MAGAZINE 25