POWER
How rising power density is changing thermal management in power electronics
By Thomas Hauer, fi eld application engineer and power specialist, Avnet Silica
A
s power electronics move towards higher voltages, faster switching speeds and more compact designs, effective thermal management is becoming a critical engineering consideration. This article examines where that pressure is building, how it is infl uencing semiconductor, packaging, and cooling decisions and why thermal design now needs to be considered earlier in the development process.
Power density raises the challenge Thermal management in power electronics is evolving into a more demanding task for a simple reason: designers are being asked to deliver more power in less space. Smaller systems, faster switching and higher operating voltages are increasing power density and putting greater pressure on thermal design. Measures that were once suffi cient, conventional packages, standard heatsinks and basic board-level cooling, can quickly become bottlenecks when the next design cycle pushes more power into a smaller form factor. This leaves less thermal headroom and requires earlier trade-offs in packaging, materials and cooling. That effect is more visible as power electronics are used in more demanding applications. The automotive sector is a prominent example, with electric vehicles moving from 400 V to 800 V architectures. That shift refl ects not only higher system voltage, but a broader trend toward higher- power operation, with greater thermal demands appearing across the design.
Pressure builds in real applications The effect is easiest to see in power- conversion functions that must manage higher voltages and higher current within tight space constraints. In EVs, the signifi cance of thermal design is heightened by on-board chargers, traction inverters, and DC-to-DC conversion. Similar concerns are appearing in
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other high-power density products, including drones, warehouse robots and cobots, as well as data centre and AI infrastructure, where rising compute density is intensifying pressure on power conversion and thermal design at system level. The underlying pattern is the same: higher performance is being pushed into smaller and more compact designs, and that makes heat removal harder.
This is one reason why power transitors are moving from silicon IGBTs to newer
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Designs using SiC can still run as hot as, or even hotter than, earlier silicon-based designs. The advantage lies in performance and
effi ciency, but the need for careful thermal design remains.
wide-bandgap (WBG) devices based on silicon carbide (SiC) and gallium nitride (GaN). While SiC, for example, is better suited to operating at higher power tiers and more thermally robust at higher temperatures, improved semiconductor performance does not eliminate the thermal challenge. Higher effi ciency can ease thermal strain, but every incremental improvement is harder to achieve. Designs using SiC can still run as hot as, or even hotter than, earlier silicon-based designs. The advantage lies in performance and effi ciency, but the need for careful thermal design remains.
Packaging becomes critical Packaging is at the heart of this change.
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Surface-mount (SMT) power transistors are becoming more popular because they are smaller than traditional leaded packages and allow for a higher component density. For example, the SMT equivalents of the traditional TO-220 package, DPAK and D2PAK, are rated for 50 W and 100 W power dissipation, respectively. They use underside pads to facilitate heat dissipation directly to, and even through, the PCB via thermal vias, with heat then coupled onward to a heatsink or chassis if required.
That makes package selection a design- stage decision rather than something deferred until later in the process. Topside- cooled SMT packages extend those options further by offering lower thermal resistance and improved switching performance, with single- or dual-sided cooling depending on application demands. Power quad fl at no-lead (PQFN) packages are also attractive for GaN devices because they combine compact size, low parasitics for low turn-on resistance (RDSon) and strong thermal performance. PQFN packages offer multiple die, clip and wire variations. This underlines how much package design is now being used to tune thermal and electrical performance to the application.
As designers push further on power and heat dissipation, packaging is playing a more vital
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