Heatsinks · Extruded
Extruded aluminum heatsinks
Extruded aluminum heatsinks are the workhorse of thermal management — continuous finned profiles produced from a dedicated die, ideal for medium power densities and high volumes at low tooling cost.
When to choose extruded
If your power density is moderate and volume is meaningful, an extruded heatsink beats machined or skived on cost. The fins are formed in the extrusion die, so there is no per-part cutting — only cut-to-length and secondary machining of the base. Extrusion is the cheapest way to make a long finned section at volume, and the die cost is a one-time tooling charge you do not pay again on reorders.
Fin density is the main limit. A practical fin height-to-thickness (fin ratio) reaches roughly 15:1–20:1 in regular production, and up to ~40:1 for selected geometries — but taller, thinner fins usually call for skived or bonded construction instead.
Typical specs
- Fin pitch: 4–12 mm common
- Base flatness: per print, milled if needed
- Alloy: 6063 (finish), 6061 (strength)
- Finish: anodized clear/black
Exact fin ratio and width confirmed at die design.
How an extruded heatsink is made
- Die design. The finned cross-section is modeled as a die; port balance and tongue support decide whether thin fins run cleanly.
- Extrude. Heated billet is pressed into the continuous finned profile.
- Quench & age. Air or water quench, then age to T5/T6 for strength.
- Cut to length. Bars are cut to the required heatsink length.
- Base machining. The mounting face is fly-cut or milled flat; holes, threads and pockets are CNC-machined.
- Finish. Anodize (clear or black) or powder coat, then inspect.
Capability & typical specs
Numbers below are typical production ranges; confirm exact limits against your drawing.
| Parameter | Typical capability |
|---|---|
| Fin ratio (h:t) | ~15:1–20:1 practical; up to ~40:1 selected |
| Fin thickness | ≥ ~1.0 mm practical |
| Fin pitch | 4–12 mm common |
| Max width | ~350 mm flat / 250 mm CCD on 3600T; up to 500 mm via partner |
| Base machining | CNC milled mounting, holes, pockets |
| Finish | Anodize II/III, powder coat |
Thermal & design notes
Design for extruded fins
- Fin thickness ≥ 1.2 mm, pitch ≥ 4 mm — keeps airflow open and protects die life.
- Specify base flatness if the sink mounts to a flat device; the base is milled flat after extrusion.
- Anodize for appearance and light corrosion resistance — a thin oxide; it is fine on fins because it barely affects conduction through the aluminum body.
- Watch fin density vs airflow. Very tight pitch chokes natural convection; match pitch to your fan or flow.
- Tighter features are machined, not extruded. Holes, threads and pockets are added by CNC after extrusion.
Extruded vs other fin types
| Need | Best choice |
|---|---|
| Low cost at volume, moderate fins | Extruded |
| Very thin, tall, dense fins, compact | Skived fin |
| Tall fins, no die limit, moderate cost | Bonded fin |
| Complex shape, low volume, tight tol | CNC machined |
Many designs start as extruded and add a machined base or bonded insert where extra density is needed.
Where extruded heatsinks are used
Power electronics
Inverter and converter sinks, diode and MOSFET mounts at moderate load.
LED & lighting
Long extruded heat-sink channels for luminaires and drivers.
Industrial
Enclosure cooling ribs and equipment thermal rails.
Automotive & EV
DC-DC and onboard charger sinks where volume justifies tooling.
Frequently asked questions
What is the maximum fin density for extruded heatsinks?
A practical fin height-to-thickness ratio is around 15:1–20:1 in regular production, and up to about 40:1 for selected geometries — but the real limit depends on alloy, section size and die design. If you need denser fins than extrusion can hold, skived or bonded construction is the usual next step.
Should the base be machined flat?
Usually yes if the sink mounts to a flat device. The extruded base is milled (fly-cut) flat to your flatness callout so the mating surface sits true against the component. Holes, threads and locating pockets are CNC-machined at the same time.
6061 or 6063 for an extruded sink?
6063 extrudes and anodizes with the best surface finish, so it is the default for exposed sinks. Choose 6061 when the part also carries structural load or needs more machining. Pure 1060 is used where thermal conductivity is the only priority, but it is soft and not structural.
Will anodizing hurt heat transfer?
Minimally. Anodize is a thin oxide (5–25 µm) and the fin body stays aluminum, so conduction through the sink is essentially unchanged. Clear anodize is standard on heatsinks; avoid paint or powder on fins because a thick insulating film adds thermal resistance.
What do you need to quote an extruded heatsink?
Envelope (length, width, fin height/pitch), alloy, power or thermal resistance target, mounting details and finish. A drawing gets the tightest quote; for volume we also confirm the die approach and MOQ with you.
Quote an extruded heatsink
Send the envelope, power and airflow — we return alloy, fin proposal and price.