Thermal and mechanical properties
Copper conducts heat roughly 60% better than aluminium, which lets copper coils use less surface area for the same heat-transfer duty. Aluminium is lighter and has decent thermal performance of its own, which is why it's common as fin material even on coils that use copper tube — combining copper's conductivity in the tube with aluminium's weight and cost advantage in the fins.
Cost and material volatility
Aluminium is generally cheaper and its price has historically been somewhat less volatile than copper, which is a real consideration for cost-sensitive product lines and large-volume manufacturing. This is one of the main reasons all-aluminium coils have gained ground in certain segments, particularly automotive and some commercial refrigeration applications.
Corrosion behavior and joint reliability
Copper resists general corrosion well and is compatible with standard brazing techniques using widely available filler alloys. Aluminium requires different joining methods — typically specialised brazing or welding processes — and is more susceptible to galvanic corrosion if it comes into direct contact with copper or brass fittings without proper isolation, something that has to be designed around carefully in mixed-metal systems.
So which one should you specify?
There's no universal answer. Copper tends to win where long service life, field serviceability and proven joining methods matter most — which covers most residential and commercial refrigeration. Aluminium earns its place where weight and cost are the primary drivers, provided the system is designed to manage the corrosion and joining considerations that come with it.