LED luminaire bodies
High bay, flood, street and downlight bodies with radial or splayed fins, an integral optic seat, a driver cavity and cast mounting features. The highest-volume application for cast heat sinks.
Die cast aluminum heat sinks
Die Cast Aluminum Heat Sinks
A die cast aluminum heat sink is a thermal management casting with integral fins that moves heat away from an electronic or electrical component. CharMax Precision casts heat sinks in A360 and A413 aluminum, rated at 113 and 121 W/m·K against 96 W/m·K for A380, in weights from 50 g to 12 kg with cast fins from 1.5 mm thick.
In short
A die cast aluminum heat sink is a thermal management casting with integral fins that moves heat away from an electronic or electrical component. CharMax Precision casts heat sinks in A360 and A413 aluminum, rated at 113 and 121 W/m·K against 96 W/m·K for A380, in weights from 50 g to 12 kg with cast fins from 1.5 mm thick.
Casting wins on geometry, not on fin density. A cast heat sink can carry fins on curved surfaces, radial fins around a lamp body, mounting bosses, a cable channel and a sealed driver cavity all in one part with no assembly at all. What it cannot do is match an extrusion's thin, closely spaced fins: a cast fin needs 1.5 to 2 mm of thickness, 1 to 2° of draft per side, and a gap between fins of at least a quarter of the fin height.
The strongest case for a cast heat sink is integration. When the heat sink is also the housing, the enclosure and the mounting bracket, one casting replaces a machined base, a bonded fin stack, a layer of thermal interface material and a set of fasteners, and the thermal path from device to air has no assembled interfaces left in it.
Capability at a glance
| Typical parts | LED luminaire bodies, driver and inverter heat sinks, drive chassis, telecoms housings |
|---|---|
| Preferred alloys | A413 at 121 W/m·K, A360 at 113 W/m·K |
| Alloy to avoid for thermal | A380 and ADC12 at 96 W/m·K unless strength dominates |
| Part weight | 50 g to 12 kg per casting |
| Minimum fin thickness | 1.5 mm at the tip, 2 mm preferred |
| Fin draft | 1 to 2° per side, thicker at the root than the tip |
| Fin height to gap ratio | Up to 4:1, 5:1 with dedicated die cooling |
| Typical fin pitch | 5 to 10 mm centre to centre |
| Base thickness | 3 to 6 mm under a concentrated heat source |
| Machined mounting pad | 0.02 mm per 100 mm flatness, Ra 0.8 µm |
| Typical finishes | Shot blast, black powder coat, chromate conversion |
| Annual volume | 500 to 500,000+ parts |
What a die cast aluminum heat sink is
A heat sink is a casting whose job is to increase the surface area between a hot component and the surrounding air. Heat conducts from the device into a machined mounting pad, spreads laterally through the base, travels up the fins, and leaves by convection and radiation. Every design decision on a cast heat sink affects one of those four steps, and the weakest one sets the junction temperature.
Die casting is chosen for heat sinks when the part has to be more than a fin array. An LED high bay body is a heat sink, an optical housing, a driver cavity and a mounting hanger in one casting. A motor drive chassis is a finned rear wall and a sealed IP-rated enclosure in one casting. That kind of integration is where casting is clearly the cheapest total solution, even though an extrusion would out-perform it fin for fin.
The honest limit is surface area per unit volume. Cast fins are thicker, shorter and more widely spaced than extruded or skived fins, so a cast heat sink of the same envelope has less area. Where a design genuinely needs both maximum fin density and a complex body, the usual answer is a cast body with a machined pad and a separate extruded or skived fin stack bonded to it, and we will tell you when your numbers point that way.
Power electronics heat sinks
Inverter, converter and power supply heat sinks with a machined pad for the power module and a cast cavity that also encloses the control board.
Motor drive chassis
VFD and servo drive bodies where the finned outer wall is also the back of a sealed enclosure, so heat leaves the unit while the electronics stay at IP65.
Telecoms and outdoor radio housings
Remote radio and small cell housings cast in A360, with external fins for natural convection and an internal gasketed cavity, exposed to weather year round.
Automotive thermal parts
DC-DC converter, on-board charger and lighting heat sinks where the package envelope is fixed by the vehicle and the casting also has to be a structural mount.
Integrated housing and heat sink
Any part where the enclosure wall is used as the thermal path, removing a separate heat sink, its fasteners and the thermal interface material between them from the bill of materials.
Fin design rules for cast heat sinks
Fins are the hardest thing in a die to fill and the hardest thing in a die to cool. Metal reaches a fin tip through the thinnest section in the part, at the end of the longest flow path, and it has to arrive before it freezes. Every fin is also a narrow slot in the steel, and a tall thin slot heats up faster than the surrounding block and sheds that heat more slowly, so the fin region normally sets the cycle time for the whole casting.
Three numbers do most of the work. Fin thickness of 1.5 mm is the practical floor and 2 mm is comfortable. Draft of 1 to 2° per side is mandatory, which means a fin is always thicker at the root than at the tip, and a nominally parallel fin will drag or break on ejection. Fin height should not exceed four times the gap between fins, or five times where the die has dedicated cooling in the fin region, so a 40 mm fin wants an 8 to 10 mm gap.
Those limits are why cast fins cannot be as thin or as densely spaced as extruded or skived fins. An extrusion pushes metal through a fixed die aperture with no ejection or draft requirement at all, so it can hold 0.8 to 1.2 mm fins at a 2 to 4 mm pitch over long lengths. Skiving cuts fins from a solid block, so it can go thinner still. Casting gives up that density in exchange for geometry a constant cross-section cannot produce.
| Fin parameter | Die cast | Extruded | CNC machined or skived |
|---|---|---|---|
| Minimum fin thickness | 1.5 mm at the tip, 2 mm preferred | 0.8 to 1.2 mm | 0.5 to 1.0 mm |
| Draft per side | 1 to 2°, mandatory for ejection | 0°, constant cross-section | 0° |
| Practical fin height | 40 to 50 mm | 150 mm and beyond | Limited by tool reach |
| Height to gap ratio | Up to 4:1, 5:1 with die cooling | 10:1 and beyond | Up to 15:1 when skived |
| Typical fin pitch | 5 to 10 mm | 2 to 4 mm | 1.5 to 3 mm |
| Fin direction | Any: radial, curved, splayed or straight | One extrusion axis only | Any, at a cost |
| Integral bosses and cavities | Cast in at no piece cost | Not possible, needs machining | Machined, expensive |
| Surface area per unit volume | Lowest of the three | High | Highest |
Where a design needs both maximum fin density and a complex body, the usual answer is a cast body with a machined pad and a bonded extruded or skived fin stack. We will say so rather than push a casting that will not hit your thermal target.
Die cast, extruded or machined: which heat sink process wins
Extrusion produces better thermal performance per unit mass, machining produces the best of all, and casting produces the cheapest complete part when the heat sink has to do more than one job. Those three statements are all true at once, and which one matters depends on your design.
There is one disadvantage of casting that no amount of design work removes: alloy conductivity. Wrought 6063 sits around 200 W/m·K, while the best casting alloy, A413, is 121 W/m·K. The silicon that makes an alloy castable also scatters the electrons that carry heat, so an extruded fin conducts roughly 65% better than a cast fin of the same size. Casting wins the comparison back through geometry, integration and piece cost, not through the material.
In practice the decision usually comes down to whether the heat sink is a standalone fin array or part of a larger component. A straight fin array bolted to a chassis is extrusion work. A luminaire body, a drive chassis or a sealed outdoor radio housing is casting work, because the alternative is four parts, an assembly operation and two thermal interfaces.
| Factor | Die casting | Extrusion | CNC machining |
|---|---|---|---|
| Best annual volume | Above 2,000 parts | Above 1,000 parts, sold by length | 1 to 500 parts |
| Tooling | Steel die, 3,000 to 25,000 USD, 25 to 40 days | Extrusion die, 500 to 3,000 USD | None required |
| Geometric freedom | Full three-dimensional form, radial fins, bosses, sealed cavities | Constant cross-section only, plus secondary machining | Full, limited by tool access |
| Alloy conductivity | A413 at 121, A360 at 113 W/m·K | 6063 at around 200 W/m·K | 6061-T6 at around 167 W/m·K |
| Thermal performance per unit mass | Good | Better, thinner and denser fins | Best, thinnest fins |
| Piece price at 10,000 per year | Lowest for an integrated part | Low for the fin stack, plus cut and machine operations | Highest |
| Part consolidation | Heat sink, housing and bracket in one part | Fin stack only, everything else is added | Possible but costly |
| Where it wins | Complex body, higher volume, integrated functions | Straight fin arrays where fin density drives performance | Prototypes, low volume, extreme fin density |
Bonded-fin and skived constructions sit between extrusion and machining and are worth considering when a cast body has to carry a very dense fin stack. We can supply the cast body machined ready for a bonded stack.
Alloy choice for thermal conductivity
Thermal conductivity in aluminum casting alloys is governed mainly by copper and silicon content. Copper is the bigger penalty, which is why A380 with 3 to 4% copper sits at 96 W/m·K while A360 at 0.6% maximum copper reaches 113 W/m·K and A413 reaches 121 W/m·K. For a part whose function is moving heat, that ordering should drive the alloy decision unless something else overrides it.
A413 is the best conductor of the four and fills thin fins well thanks to 11 to 13% silicon, at the cost of the lowest tensile strength at 296 MPa and only fair machinability. A360 is the better all-round choice for a heat sink that is also a sealed or outdoor housing, because it combines 113 W/m·K with good corrosion resistance and excellent pressure tightness. A380 belongs on a heat sink only where the part is structurally loaded or heavily machined.
Keep the alloy decision in proportion. The spread from A380 to A413 is about 26%, which typically moves a junction temperature by a few degrees rather than tens of degrees. Adding 30% more fin area, unblocking the air path or machining the mounting pad flat are all bigger wins, so do not accept a strength or castability penalty for conductivity the design does not need.
| Alloy | Thermal conductivity | Tensile strength | Specify it when |
|---|---|---|---|
| A413 (AlSi12) | 121 W/m·K | 296 MPa | Thermal performance is the priority and the part is not heavily loaded |
| A360 (AlSi10Mg) | 113 W/m·K | 317 MPa | The heat sink is also a sealed or outdoor housing, the best all-round choice |
| ADC12 (A383) | 96 W/m·K | 310 MPa | Fins are thin or the flow path is long and filling is the constraint |
| A380 (AlSi8Cu3Fe) | 96 W/m·K | 324 MPa | The part is structurally loaded or heavily machined and conductivity is secondary |
Values are typical as-cast properties and match the alloy comparison on our materials pages. Copper content is the main reason A380 and ADC12 conduct less well than A360 and A413.
How a cast heat sink is manufactured, cast versus machined
Gate position, die temperature and cycle time on a heat sink are all set by the fins rather than by the body. Metal is gated into the heaviest section, usually the base, and has to reach every fin tip before freezing, so simulation is run with fin fill as the pass or fail criterion rather than overall cavity fill.
Die thermal management is the other half of the job. Cooling lines are run as close to the fin roots as the steel section allows, because the standing steel between fins is the part of the die that overheats first. Ejection needs equal planning: a fin array has a large contact area with the die, so ejection force is high, and the ejector layout has to push on the base and never on a fin.
After casting, gates and flash are trimmed and the part is shot blasted. Machining is deliberately minimal. On most heat sinks the only machined surface is the pad the device mounts to, because that interface is where a poor surface costs the most thermally. Fin surfaces are left as-cast, which is not a compromise: a slightly rough fin is marginally better for convection than a polished one.
- Cast: the entire fin array, base, mounting bosses, cable channels, driver cavity, gasket groove and cast-in identification
- Cast: 0.5 to 1.0 mm of machining stock on the component mounting pad, plus cast datum pads for the machining fixture
- Machined: the pad the power device or LED module bolts to, flattened to 0.02 mm per 100 mm and Ra 0.8 µm so the thermal interface material performs as specified
- Machined: tapped holes for the device, the driver and the mounting hardware
- Machined: any sealing land, gland hole or optic seat where the casting also serves as an enclosure
- Finishing: shot blast, then usually black powder coat at 60 to 90 µm, which slightly raises emissivity at negligible thermal cost
- Left as-cast: all fin surfaces at Ra 1.6 to 3.2 µm, which is marginally better for convective transfer than a smooth surface
Design considerations for cast heat sinks
Fin thickness and draft
1.5 mm minimum at the tip and 2 mm if the mass budget allows, with 1 to 2° of draft per side so the fin is thicker at the root. Draft is not negotiable: a parallel-sided fin will not release from the die and will drag or snap on ejection.
Fin height and gap
Keep fin height no more than four times the gap between fins, or five times where the die has dedicated cooling in the fin region. A 40 mm fin therefore needs an 8 to 10 mm gap. Taller and tighter than that and the steel between fins overheats, the metal freezes early, and you get short fins on every shot.
Fillet the fin roots
Radius the root at 25 to 50% of the base thickness. The root is where heat actually crosses from base to fin and where the casting is most likely to crack in service, so the fillet helps thermally and structurally.
Base thickness under the source
3 to 6 mm under a concentrated heat source. The base has to spread heat laterally before it reaches the fins, and a base that is too thin creates a hot spot directly under the device that no amount of extra fin area will fix.
Orient the fins for the air
Vertical fins for natural convection so air can rise between them, fins aligned with the flow for forced air. Radial fins around a lamp body work in any mounting orientation, which is why they dominate LED luminaires. A close-fitting shroud around cast fins usually costs more performance than it gains.
Machine only the interface
The mounting pad is the one surface that must be machined. A 0.1 mm air gap at the interface is worse thermally than 20 mm of aluminum, so specify flatness and roughness there and leave every other surface as-cast.
Integrate rather than assemble
Combine the heat sink with the housing, the enclosure and the mounting bracket in a single casting. Every eliminated interface removes a thermal resistance, a fastener and an assembly step, and this is the main reason a cast heat sink beats a better-performing extrusion in a finished product.
Choose the coating carefully
Powder coat at 60 to 90 µm has a negligible thermal penalty and slightly raises emissivity, which helps at low air speeds. Avoid thick films, avoid filling narrow fin gaps with coating, and confirm the spray can physically reach between the fins at your chosen pitch.
Do not chase conductivity first
Fin area, air path and interface quality dominate the result. Moving from A380 to A413 buys about 26% more conductivity in the metal, usually a few degrees of junction temperature. Adding 30% more fin area or clearing the air path is nearly always the larger win.
Industries that buy die cast aluminum heat sinks
LED lighting
High bay, street, flood, downlight and grow light bodies where a single casting is the heat sink, the optical housing and the mounting bracket. This is the largest volume application for cast heat sinks worldwide.
Power electronics
Inverter, converter, rectifier and power supply heat sinks, usually with a machined pad for the power module and a cast cavity that encloses the control electronics.
Motor drives and controls
Variable frequency and servo drive chassis where the heat sink forms the rear wall of a sealed enclosure, moving heat outside while the electronics stay protected to IP65.
Telecoms and networking
Outdoor remote radio units, small cells and gateways cast in A360 for corrosion life, with external fins sized for natural convection because a fan is not acceptable in the field.
Automotive and EV
DC-DC converter, on-board charger and exterior lighting heat sinks, where the envelope is fixed by vehicle packaging and the casting doubles as a structural mount.
Industrial equipment
Machine control cabinets, welding power sources and laser supplies, where duty cycle rather than peak power sets the required fin area and the part often sits in a dusty environment.
Proof
Related production programs
Real parts we have manufactured that involved this capability.
Keep exploring
Related capabilities and resources
Manufacturing services
Aluminum alloys
Part types
Industries served
Further reading
Frequently asked questions
How thin can die cast heat sink fins be?
1.5 mm at the tip is the practical minimum and 2 mm is the comfortable target, with 1 to 2° of draft per side so the fin is thicker at the root. Thinner than 1.5 mm and the metal freezes before it reaches the fin tip, producing short or incomplete fins. Extruded fins reach 0.8 to 1.2 mm and skived fins go thinner still, because neither has to release from a die.
Is a die cast heat sink worse than an extruded one?
Thermally, yes, per unit of volume. Cast fins are thicker and more widely spaced, and the best casting alloy conducts about 65% less well than wrought 6063. Commercially the answer often reverses, because a casting can carry the fins, the housing, the driver cavity and the mounting features in one part. Extrusion wins on a standalone straight fin array; casting wins when the heat sink is part of a larger component.
Which aluminum alloy has the best thermal conductivity for die casting?
A413 at 121 W/m·K, followed by A360 at 113 W/m·K, with A380 and ADC12 both at 96 W/m·K. Copper content is the main reason for the spread, since A380 carries 3 to 4% copper against 0.6% maximum in A360. A360 is usually the better practical choice for a heat sink that is also a sealed or outdoor housing, because it adds good corrosion resistance and excellent pressure tightness to nearly the same conductivity.
Can the heat sink and the housing be one casting?
Yes, and it is usually the reason to choose casting in the first place. A single part can carry external fins, an internal sealed cavity with a cast gasket groove, PCB standoffs, cable gland bosses and mounting features. Combining them removes a thermal interface, a set of fasteners and an assembly operation, and the thermal path improves because there is no interface material between heat sink and housing.
How closely can cast fins be spaced?
Keep the gap at a minimum of a quarter of the fin height, so a 40 mm fin needs an 8 to 10 mm gap and typical fin pitch lands at 5 to 10 mm. The constraint is die cooling rather than metal flow: the standing steel between two tall fins has a poor path to the cooling lines, overheats, and stops filling reliably. Dedicated cooling in the fin region can push the ratio to 5:1.
Does powder coating a heat sink reduce its thermal performance?
Not measurably at normal thickness. A 60 to 90 µm powder coat adds a small conduction resistance and slightly raises surface emissivity, and on most natural-convection heat sinks the two effects roughly cancel. The real risks are thick films, coating bridging across narrow fin gaps, and paint on the machined mounting pad, which is why that pad is masked or machined after coating.
What files do you need to quote?
A 3D model in STEP, IGES, X_T, SLDPRT or native CAD format, plus a 2D drawing showing critical dimensions, tolerances, surface finish, alloy and any inspection requirements. If you only have a 3D model we can still quote, but a drawing that marks which features are critical to function will get you a more accurate price and prevent misunderstandings later.
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Send your 2D drawing and 3D model with the power to dissipate, ambient temperature and air condition. You will get piece pricing, tooling cost and a written DFM report on fin geometry, alloy choice and whether casting is genuinely the right process for your target.
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