When selecting the materials for heat sinks, thermal conductivity is not the only factor that determines thermal dissipation. This article explores the common materials for heat sinks and their properties in detail to guide you to choose the right material for your applications.
Common Materials Used for Heat Sinks
There are some common materials used for heat sinks. With so many materials to choose from, you may find yourself a bit confused, as an inappropriate choice could lead to performance and budget issues.
Below is a brief overview of these materials：
Aluminum
80%of the heat sinks on the market are made from aluminum, not because it has the highest thermal conductivity, but because aluminum alloy, as a single material, offers the best balance of thermal conductivity, weight, cost, and machinability.
Good heat dissipation
Aluminum has a thermal conductivity of 150–237 and a high specific heat capacity, so it can absorb heat while ensuring good heat dissipation. It heats up slowly, reducing the likelihood of localized overheating, making it suitable for products such as standard servers or LED lighting fixtures.
Lightweight
Since aluminum has a density of only about 2.7, it is an excellent choice when overall weight is a consideration for your application.
Easy to Machine
Aluminum has medium hardness, making it ideal for extrusion. Additionally, it offers low cutting resistance during CNC machining, which minimizes tool wear. This can help you significantly reduce machining time and costs.
Low Cost
The cost of raw aluminum ranges from $2 to $4 per kilogram. Combined with its ease of machining, this makes it the most cost-effective option for manufacturing heat sinks. You can use the savings to optimize other aspects of the heat sink.
Of course, aluminum is not a perfect heat sink material. It also has some significant drawbacks, such as susceptibility to corrosion, low wear resistance, and low emissivity. In such cases, you can improve these properties by applying anodizing or hard anodizing—which are also the most common aluminum finishes used in heat sinks.
Copper
Copper is the most widely used material for heat sinks after aluminum and holds an irreplaceable position primarily due to the following factors.
Extremely High Thermal Conductivity
Copper has a thermal conductivity of up to 400, which is twice that of aluminum. This high thermal conductivity allows copper to be used in heat dissipation applications where aluminum falls short—for example, when you’re looking for heat dissipation materials for CPUs and IGBT modules. Under the same cross-sectional area and thermal resistance conditions, copper can conduct heat more quickly.
Good CTE Matching with Chips
Copper’s coefficient of thermal expansion (approx. 17 µm/(m·K)) is much closer to that of chips. After being soldered to a chip and subjected to thermal cycling, the risk of cracking is low, making it suitable for use in the aerospace and automotive electronics industries.
High-Temperature Resistance
Copper has a high melting point, so even if your product is exposed to temperatures as high as 200°C, it will retain its strength and be unlikely to creep.
Although copper has excellent thermal conductivity, there are some drawbacks that prevent it from becoming the most widely used material for heat sinks. For example, it is prone to oxidation in humid environments, forming a green patina. In such cases, applying nickel plating of 5-8 μm thickness can help minimize the rise in thermal resistance and extend the effectiveness of your heat sink.
Graphite
Graphite is also an important material for heat sinks, primarily due to its unique microstructure.
Extremely high thermal conductivity in the in-plane direction
Graphite’s microstructure consists of carbon atoms arranged in layers, giving it optimal thermal conductivity in the in-plane direction—reaching up to 1,900, far exceeding that of all metallic materials.
Soft and Thin
Graphite can be processed to a thickness of 0.01 mm while still conducting heat effectively, and it can be bent repeatedly. If you’re looking to develop heat dissipation solutions for electronic devices such as smartphones and tablets—especially foldable smartphones.
Although graphite has an extremely high thermal conductivity, it cannot replace aluminum and copper because it has poor thermal conductivity in the perpendicular direction and can only be made into thin films, not large-volume structures.
Ceramic
The reasons why ceramic is used as a heat sink material are quite unique.
Electrical Insulation
Ceramic is an electrical insulator, whereas aluminum and copper are both conductive metals that cannot come into direct contact with the chip and circuitry. Ceramic can serve as a substrate that acts as both a heat dissipation pathway and an insulating material, which not only saves space but also effectively prevents short circuits between the chip/PCB and the heat sink.
Low Coefficient of Thermal Expansion
As mentioned earlier, the coefficients of thermal expansion for aluminum and copper differ significantly from that of silicon, which can easily lead to fractures at solder joints during thermal cycling. Ceramics have a coefficient of thermal expansion of only 4.5–8, which is particularly close to that of silicon chips, making them indispensable for equipment with a required lifespan of over ten years.
However, ceramics are relatively brittle, which may increase shipping costs.
Material Comparison: Key Differences Between 4 Types
| Property | Aluminum | Copper | Graphite | Ceramic |
|---|---|---|---|---|
| Thermal Conductivity (W/m·K) | 150–237 | 390–401 | 300–1,900 | 20–200 |
| Density (g/cm³) | 2.70 | 8.96 | 1.8–2.2 | 2.5–4.0 |
| High-Temperature Resistance | ★★☆☆☆ | ★★★☆☆ | ★★★★☆ | ★★★★★ |
| Typical Surface Finish | Anodizing | Nickel Plating | Metal Coating | Metallization |
| Machining Cost | ★★☆☆☆ (Low) | ★★★★☆ (High) | ★★★★★ (Very High) | ★★★★★★ (Highest) |
Design Consideration
The design of the heat sink also plays an important role in material selection. Otherwise, even if you choose high-quality, expensive materials, it will be difficult to achieve optimal heat dissipation.
- The aspect ratio of the fins not only affects the manufacturing process but also depends on the heat dissipation method—whether it is natural air cooling, forced air cooling, or water cooling. An aspect ratio that is too high may exceed the material’s thermal conductivity limit, while one that is too low may fail to fully utilize the material’s heat dissipation capacity.
- To prevent problems during installation after you’ve spent a great deal of effort selecting the heat sink material, you should consider whether welding will cause the material to deform when selecting the material.
How to Select Materials for Different Applications
There is no such thing as a perfect material—only the most suitable choice, which depends on the factors you prioritize for your application.
- Thermal Performance Priority:
AI training, lasers, radar, and the aerospace industry: In AI server CPUs and satellite transponders, if heat cannot be dissipated in a timely manner, it can cause damage to the system and equipment.
In these cases, you should choose a CNC-milled copper fin pin heat sink with a nickel-plated finish.
- Cost Priority:
LED lighting, home appliance industry: Applications such as streetlights and power adapters are already low-cost, so manufacturing cost is the primary consideration when selecting heat sink materials. You should choose extruded aluminum heat sinks with an anodized finish to ensure both thermal performance and aesthetic requirements are met.
- Weight Priority:
Consumer electronics and automotive electronics industries: For devices such as smartphones, tablets, and in-vehicle electronic control units, where portability and light weight are essential, choose aluminum alloys with lower density and graphite as a supplementary material. If aesthetic appeal is also a priority, you can incorporate anodizing and brushed finishes.
- Balance Between Performance and Cost:
Data centers and industrial power supply industries: CPUs, GPUs, and IGBT modules typically require solutions that ensure effective heat dissipation while keeping total costs in check. You can opt for a composite structure with a copper base and aluminum fins as the heat dissipation solution.
FAQ
Can a heat sink be made from stainless steel?
Because stainless steel has a very low thermal conductivity—only 16 W/m·K—it would require a very large volume to achieve the same heat dissipation effect, so it is rarely used as a material for heat sinks.
Does black anodizing improve heat sink performance?
Yes. Black anodizing is inexpensive, and in fanless, natural cooling scenarios, it can significantly increase the thermal emissivity—up to seven times that of bare aluminum—thereby improving heat dissipation.
Can heat sink materials be recycled?
Yes. The recycling process for aluminum heat sinks is simple, and they can be recycled at nearly 100%. The recycled material is then processed—through die-casting and other methods—to produce heat sink fins. As for copper-aluminum composite heat sinks, the material can be recovered by crushing the heat sinks, separating the aluminum and copper, and finally refining them.
Does surface roughness improve heat dissipation?
Surfaces that have been polished and anodized or that come into contact with a heat source require a relatively low level of surface roughness to improve heat dissipation efficiency. If the surface is too rough, the interfacial thermal resistance will increase rapidly, reducing the radiative efficiency of the oxide layer.
Can copper heat sinks be extruded?
No. Copper heat sinks can be rarely manufactured by extrusion because the temperature required for extruding copper is as high as 600°C, and the extrusion process can easily damage the dies and reduce the service life of the extrusion rollers, thereby significantly increasing costs.
When selecting materials for heat sinks, what is the order of priority for the factors to consider?
First, you need to determine the operating environment of the heat sink and the dimensions of the space where it will be installed. Next, consider the manufacturing process and design options. Finally, your team takes cost and budget into account to select the most suitable and cost-effective solution.
Which aluminum alloy is best for heat sinks?
Aluminum 6063 is the best for heat sinks. Its thermal conductivity is much higher than that of 6061, and it is well-suited for extrusion and CNC machining, as well as for air-cooled heat dissipation applications.
What are the advantages of CNC-machined heat sinks compared to extruded ones?
Compared to extrusion, CNC machining is better suited for the prototyping stage of heat sinks. At this stage, you don’t have to worry about tooling costs, so you can quickly produce prototypes and adapt to design changes. Additionally, CNC machining ensures lower surface roughness and tighter tolerances. When working with a limited budget, you can use extrusion to create the preliminary shape and then use CNC machining to machine the critical mounting surfaces.
Final Thoughts
When selecting materials for heat sinks, don’t just look at performance data and also take design into consideration. If you need to design or upgrade a heat sink, let us know your equipment type, application scenario and budget, and we’ll provide you with a practical solution.
