Two Metals, Two Thermal Realities
Copper conducts heat at roughly 400 W/mK – about twice the 200 W/mK of aluminium. If thermal conductivity were the only factor, every heat sink would be copper. But a heat sink is a system of geometry, weight and cost, and that is where the comparison gets interesting. Extruded aluminium compensates for lower conductivity with fins that copper cannot economically match.
Why Aluminium Wins Most Designs
Aluminium wins on four fronts. Weight: one third of copper, critical for anything mounted or shipped. Cost: roughly half per kilogram and far cheaper to extrude into complex fin geometries. Geometry: extrusion produces tall, thin fins – 0.8 mm walls with fin ratios above 10:1 – that multiply surface area, and surface area is what actually moves heat. Surface finish: anodising adds corrosion protection and emissivity. For 90 percent of B2B thermal designs, an extruded aluminium sink delivers the lowest cost per watt.
When Copper Earns Its Price
Copper earns its price in three situations. Extreme space constraints: a tiny base plate where every square millimetre matters. Very high heat flux: IGBT and CPU hotspots where the spreading layer must be copper. Hybrid designs: a copper base or heat pipes embedded in an aluminium fin body – the best of both worlds. Copper is also used as a complete sink for small quantities where tooling for aluminium extrusion is not justified.
The Practical Verdict
For volume production, extruded aluminium is almost always the right answer: lower cost, lighter, and geometry beats conductivity. Where a design genuinely needs copper performance, the smart move is a hybrid – aluminium fins with a copper base or heat pipes – rather than a solid copper block. Siken Aluminum extrudes heat sink profiles in 6063-T5 and T6, and our machining line can integrate copper base plates, heat pipes and press-fit fins into a single delivered assembly.