Straight-fin (plate-fin)
Parallel fins rising from a flat base. The default design for power supplies, motor drives and board-level cooling, and the most efficient when air flows along the fins.
Thermal management extrusions
Aluminium Heat Sink Extrusions
An extruded aluminium heat sink is a finned profile pushed through a die in one piece, then cut to length, so the base and fins form a continuous path for heat to flow from a component into the surrounding air. Metline supplies heat sink extrusions in 6063, 6060, 6061 and 1xxx alloys, as cut lengths or as fully machined and anodised parts, for power electronics, LED lighting, telecoms and industrial equipment worldwide.
- Main alloy
- 6063-T5 (~200 – 209 W/m·K)
- Fin types
- Straight, slant, radial, pin
- Supply
- Cut lengths or machined parts
- Finishes
- Clear or black anodised, chromate-free conversion
Why heat sinks are extruded from aluminium
Every electronic device turns part of its power into heat. A heat sink spreads that heat out of a small, hot component and offers a large finned surface to the air, keeping the component below its maximum junction temperature. Extrusion is the most economical way to make that finned shape in volume.
Aluminium wins over copper for most heat sinks on balance rather than on conductivity alone. Copper conducts about twice as well (around 390 W/m·K against roughly 200 W/m·K for 6063), but it is more than three times as dense and considerably more expensive, and it cannot be extruded into thin, tall fins. For a given weight and cost, an aluminium extrusion usually removes more heat; copper is reserved for small, very high flux spots, often as an insert or base plate under an aluminium fin stack.
The extrusion process also suits thermal design. One die produces a profile of constant cross-section in long lengths, so a single tool can serve heat sinks of 30 mm or 300 mm simply by cutting to different lengths. Cooling performance can be tuned later by changing the cut length, adding a fan, or machining pockets and mounting holes without new tooling.
Types of extruded heat sink
Slant or angled fin
Fins set at an angle to fit an enclosure, to direct airflow, or to give more fin length within a low height.
Radial / round (LED)
Fins radiating from a central core, used in downlights, spotlights and street lights. Works with air from any direction and suits natural convection when mounted vertically.
Pin-fin (cross-cut)
A straight-fin extrusion cross-cut by sawing or milling into an array of pins, so air can enter from any direction. Good in unpredictable airflow and in natural convection with horizontal mounting.
Enclosure heat sink
A profile that forms the housing of the electronics as well as the cooler, such as amplifier cases, inverter housings and LED drivers.
Large and wide profiles
Wide-base sections for IGBT modules, welders and inverters, often combined with fans or bonded-fin extensions where fins must be very tall.
Alloys for heat sink extrusions
Thermal conductivity falls as alloying content rises, but so does extrudability for thin fins. 6063-T5 is the standard compromise: high conductivity, excellent extrudability, good anodising and enough strength for mounting.
| Alloy and temper | Thermal conductivity (typical) | Typical tensile strength | When to choose it |
|---|---|---|---|
| 6063-T5 | about 200 – 209 W/m·K | about 185 MPa | Default for most heat sinks; thin fins, fine pitch, even anodising |
| 6063-T6 | about 200 W/m·K | about 240 MPa | Where mounting loads or clips need a harder profile |
| 6060-T5 | about 200 – 210 W/m·K | about 185 – 190 MPa | European equivalent to 6063; very easy to extrude |
| 6061-T6 | about 167 W/m·K | about 310 MPa | Heat sinks that are also structural: chassis, housings, frames |
| 1050A / 1070 | about 222 – 230 W/m·K | about 75 – 110 MPa | Maximum conductivity where loads are very light; simpler sections |
Values are typical published figures for the temper; conductivity varies slightly with exact composition and heat treatment. Electrical conductivity of 6063-T5 is roughly 53 – 55 % IACS.
How to size an extruded heat sink
Heat sink selection starts with a thermal budget. The total allowed thermal resistance from the component junction to the air is the temperature rise you can accept divided by the power dissipated. The heat sink must take whatever is left after the component package and the thermal interface material have used their share.
- Set the limitsMaximum junction or case temperature from the component datasheet, maximum ambient air temperature, and the power to be removed in watts.
- Work out the budgetRequired total resistance = (Tjunction − Tambient) ÷ power. Example: (110 − 50) °C ÷ 40 W = 1.5 °C/W.
- Subtract the lossesDeduct the junction-to-case resistance from the datasheet and the interface material resistance (pad, grease or phase-change). The rest is the heat sink target, for example 1.0 °C/W.
- Choose a profilePick a section whose published resistance per length meets the target in your airflow condition, natural or forced. Resistance does not halve when length doubles; extra length gives diminishing returns.
- VerifyConfirm with thermal simulation or a prototype test, especially in enclosures where airflow is uncertain.
| Design factor | Natural convection | Forced air (fan) |
|---|---|---|
| Fin spacing (gap) | Wider, roughly 6 – 12 mm, so warm air can rise freely | Narrower, roughly 2 – 5 mm, for more surface area |
| Fin orientation | Vertical fins, aligned with rising air | Aligned with the fan airflow |
| Surface finish | Anodising matters: raises emissivity from about 0.05 – 0.1 to around 0.8 | Radiation is minor; finish chosen for protection and appearance |
| Base thickness | Thicker bases spread heat from small sources across more fins | Same; also leaves material for tapped mounting holes |
Extrusion sets practical limits on fin geometry. The ratio of fin height to the gap between fins is the key one: conventional dies comfortably produce ratios of around 6:1 to 10:1, and specialised dies can go higher. Fins are normally 1 – 2 mm thick, with a slight taper towards the tip. Beyond these limits, bonded-fin, skived or brazed constructions are used instead.
Heat sink extrusion sizes and supply range
Typical capability
- Profile width
- from about 10 mm up to around 400 – 600 mm for wide sections, depending on the die and press
- Overall height
- from a few millimetres up to about 100 mm; taller fins by bonded-fin construction
- Fin thickness
- about 0.8 – 2.0 mm, with tapered tips
- Base thickness
- about 2.5 – 15 mm, chosen for heat spreading and thread depth
- Cut length
- from about 10 mm wafers to full mill lengths of 3 – 6 m
- Tolerances
- EN 755-9 / EN 12020-2 or ANSI H35.2; base flatness machined where required
Many common heat sink sections can be supplied from existing dies, avoiding tooling cost. For a new profile, send the envelope, power and airflow so the section can be reviewed for extrudability before the die is made.
| Example envelope (W × H) | Typical use |
|---|---|
| about 20 × 10 mm | TO-220 and small regulators |
| about 50 – 65 × 20 – 32 mm | DC/DC converters, small power supplies |
| about 100 – 125 × 20 – 60 mm | Motor drives, audio amplifiers, LED drivers |
| about 150 – 260 × 40 – 80 mm | IGBT modules, inverters, welding equipment |
| about 350 – 410 × 60 – 70 mm | High-power converters, rack-mounted equipment |
Machining and finishing
Precision cutting
Saw cutting to length with deburred ends; tight length tolerances for automated assembly.
CNC machining
Mounting holes, tapped threads, pockets for components, fin removal for clearance, and flycutting of the base for flat contact.
Cross-cutting
Sawing or milling across the fins to make pin-fin heat sinks from a straight-fin profile.
Anodising
Clear or black anodising to MIL-A-8625 Type II, typically 10 – 25 µm. Improves corrosion resistance and emissivity; the film is an electrical insulator, so mask contact areas if grounding is needed.
Conversion coating
Trivalent (RoHS-compliant) chromate conversion to MIL-DTL-5541 for a conductive, corrosion-resistant surface or a primer base.
Assembly
Pressed-in studs, threaded inserts, clips, thermal pads and fan fixings fitted before delivery on request.
Flatness of the mounting surface is often the deciding quality point: a poorly flat base leaves air gaps that raise interface resistance more than any alloy choice. For power modules, specify a machined base with a flatness tolerance and surface roughness on the drawing.
Where extruded heat sinks are used
- Power electronics: inverters, UPS systems, motor drives, welders and battery chargers using IGBTs and MOSFETs
- LED lighting: street lights, high-bay and flood lights, downlights and linear fittings
- Renewable energy: solar inverters and power-conversion cabinets
- Electric vehicles: on-board chargers, DC/DC converters and charging stations
- Telecoms and IT: base-station radios, network equipment and rack power supplies
- Audio and consumer: amplifiers, enclosures and appliance controllers
- Industrial control: PLC modules, servo amplifiers and cabinet electronics
Extruded heat sinks compared with other methods
| Method | Strengths | Limitations |
|---|---|---|
| Extruded aluminium | Low tooling cost, one-piece, any length, easy to machine | Fin height-to-gap ratio limited; constant cross-section |
| Bonded or brazed fin | Very tall, thin, dense fins; mixed materials possible | Higher cost; joint adds a small thermal resistance |
| Skived fin | Very thin, dense fins cut from a solid block | Higher unit cost; usually copper or 1xxx aluminium |
| Die-cast aluminium | Complex 3D shapes and integrated housings | Lower conductivity casting alloys (often around 90 – 150 W/m·K); expensive tooling |
| Stamped fin | Very low cost for small, low-power parts | Low performance; thin sheet only |
How to order heat sink extrusions
- SpecifyProfile drawing or envelope, alloy and temper, cut length and tolerance, machining drawing, finish, quantity, and the power and airflow if you want the section checked.
- QuoteWe confirm the die (existing or new), alloy, temper, finish, packing and delivery terms (EXW, FOB, CIF or DAP) for your destination.
- SampleFor new or appearance-critical sections, a short length or finish sample can be supplied for approval before the production run.
- ProcessProfiles are extruded, aged, cut, machined, finished and inspected for dimensions and base flatness; parts are packed to protect fins in transit.
- DocumentEach delivery carries a mill test certificate to EN 10204 3.1 with cast analysis and mechanical results; coating thickness reports and third-party inspection on request.
- ShipLengths are film-protected, bundled with spacers and packed in cartons, crates or on pallets for sea, air or road freight to your port or door.
References and standards
- ASTM B221 – Standard Specification for Aluminum and Aluminum-Alloy Extruded Bars, Rods, Wire, Profiles, and Tubes
- EN 755-2 – Aluminium and aluminium alloys: extruded rod/bar, tube and profiles, mechanical properties
- EN 12020-2 – Extruded precision profiles in alloys EN AW-6060 and EN AW-6063: tolerances on dimensions and form
- MIL-A-8625 (now MIL-PRF-8625) – Anodic coatings specification
- MIL-DTL-5541 – Chemical conversion coatings specification
- ASM Handbook, Volume 2 – Properties and Selection: Nonferrous Alloys (thermal data)
Aluminium (aluminum) heat sink extrusions: frequently asked questions
Which aluminium alloy is best for heat sinks?
6063-T5 for most extruded heat sinks. It conducts about 200 – 209 W/m·K, extrudes thin fins accurately and anodises well. Choose 6061-T6 only when the heat sink also carries structural loads, and 1050A when maximum conductivity matters more than strength.
Does black anodising improve heat sink performance?
In natural convection, yes: anodising raises surface emissivity from about 0.05 – 0.1 to around 0.8, which increases heat lost by radiation. The colour itself matters little at these temperatures. In fan-cooled designs the gain is small.
How long should my heat sink be?
Long enough to meet the thermal resistance target, but extra length gives diminishing returns because the far end of the profile runs cooler. Profile data sheets and a thermal check identify the useful length.
Can you supply heat sinks cut and machined?
Yes. Profiles can be cut to length, CNC machined, tapped, flycut flat, anodised or conversion-coated, and supplied ready to assemble.
Is copper better than aluminium for heat sinks?
Copper conducts about twice as well but is over three times heavier and much more expensive. Aluminium extrusions give better performance per kilogram and per unit cost for most applications.
Can a new heat sink profile be made?
Yes. Send the envelope, component layout, power and airflow. The section is reviewed for fin ratio and extrudability before the die is made, and samples can be supplied for testing.
Need a heat sink profile for your product?
Send the envelope, power, airflow and quantities, and we will propose a section, machining and finish with a delivered price.
