7 Processes to Manufacture Heat Sink

This article will discuss several processes to manufacture heat sinks, those essential cooling parts that stop hot electronics, like your computer’s CPU and graphics card, from burning out. We’ll show you how engineers ensure these coolers work perfectly.

What is a Heat Sink?

A heat sink is a device that transfers the operating heat of the equipment to maintain normal operation and is applied to components such as computer CPUs and GPUs. According to the cooling method, they are divided into multiple types, such as air cooling, liquid cooling, and heat pipes. The main materials are copper and aluminum alloys, and of course, there are some non-metallic materials such as graphene thermal plastics and ceramics. Heat dissipation is achieved through the collaborative effect of heat conduction, convection, and radiation. Manufacturing processes cover technologies such as aluminum extrusion and copper-aluminum bonding. The design and manufacturing of the fins directly affect the heat dissipation efficiency.

Heat Sink Materials

The dominant materials used for heat sinks are copper and aluminum alloys.

• Copper: Copper’s thermal conductivity of 380-420 W/mK is significantly better than that of aluminum alloys (Aluminum alloys range from 150 to 250 W/mK. It is primarily used in high-end thermal management applications where performance is paramount, such as AI computing servers, high-power RF devices, premium consumer electronics, and GPU/CPU cooling.
• Aluminum alloys: Aluminum heat sinks are mainly deployed in large-scale environmental applications with relatively lower thermal requirements but high demands for structural integrity and lightweighting, such as in power systems, photovoltaics (solar), automotive, and communication base stations.
• Non-metallic materials: Other materials, including graphene-based thermal plastics and ceramics (e.g., silicon carbide, boron nitride), are also used.

Recently, new metal matrix composite materials have emerged, including graphene-based aluminum, diamond/aluminum composites, and diamond/copper composites.

• Graphene-based aluminum: This material is produced by modifying aluminum through the smelting process. It not only enhances the thermal conductivity of the aluminum alloy but also retains its excellent structural properties and lightweight advantages. Current graphene-based aluminum can achieve a thermal conductivity of 300-350 W/mK.
• Diamond/aluminum composite: Diamond has a theoretical thermal conductivity of up to 2000 W/mK. By modifying aluminum with diamond, the composite’s thermal conductivity is significantly increased, currently reaching 500-600 W/mK. However, achieving higher thermal conductivity requires a greater diamond content, which negatively impacts the aluminum’s structural and processing performance, and the high cost of diamond affects overall product cost-effectiveness.
• Diamond/copper composite: Utilizing diamond’s high thermal conductivity to modify copper significantly boosts the copper’s thermal performance. Diamond/copper composites can currently achieve thermal conductivity of 600-1000 W/mK, depending on the diamond filling content.

7 Heat Sink Manufacturing Processes

There are several technologies to manufacture heat sinks, including:

1. CNC Machining

CNC machining is not a single process but a technology platform. A digital 3D model created by a designer is converted into machine-readable instructions (typically G-code) via specialized software. The CNC system then precisely controls the motors and cutting tools to automatically perform cutting, carving, drilling, and other operations on materials like metal, plastic, or wood, producing a physical part identical to the digital model.

Key CNC machining processes include CNC milling (tool rotates, workpiece is fixed) and CNC turning (workpiece rotates, tool is fixed and moves). Others include CNC drilling, grinding, and wire cutting.

• Advanced machining: Multi-axis machining represents high-end CNC. A 3-axis machine is fundamental, processing only the top and sides of a part, unable to handle complex curved surfaces or undercuts. A 5-axis machine, with an A-axis (rotation around X) and C-axis (rotation around Z), allows the tool to approach the workpiece from any direction, enabling the machining of highly complex geometries (e.g., impellers, aerospace structural parts) with extreme precision and efficiency.
• Advantages: CNC offers extremely high precision and repeatability, easily achieving micron-level tolerances and producing identical parts consistently. It’s typically used in the prototyping stage of heat sinks and for milling the base of die-cast or forged heat sinks to ensure flatness against the heat source.
• Disadvantage: As a “subtractive manufacturing” process, it generates a certain amount of material waste from cutting.

2. Aluminum Extrusion

In this process, an aluminum billet is heated to a softened state (approximately 400-500 ℃ below its melting point of 660 ℃). A huge hydraulic force (up to thousands of tons) is used to force the softened aluminum through a die with a specific cross-sectional shape (die hole), resulting in an infinitely long profile matching the die’s cross-section. Finally, the profile is cut to the required length and undergoes post-processing (e.g., cutting, CNC milling, tapping).

• Advantages: Aluminum extrusion is low-cost and suitable for mass, standardized production. It is the most common heat sink process on the market, used for the fin sections of most low-power CPU air coolers and common aluminum profile heat sinks.
• Limitation: The aspect ratio (height-to-thickness ratio) of the fins is limited, making it impossible to create very thin and tall fins.

3. Die Casting

Die casting involves heating the aluminum alloy in a furnace until it is completely molten. A shot mechanism then injects the liquid aluminum at high speed and high pressure into a precise two-part steel mold, where it rapidly cools and solidifies.

• Advantages: Its strength lies in one-piece molding, capable of producing heat sinks with complex shapes and tight structures, such as GPU cooler housings and highly integrated chip cooling modules.
• Limitation: The process is prone to defects like porosity and shrinkage, resulting in slightly inferior thermal conductivity.

4. Forging

Forging, analogous to a blacksmith hammering iron, is a mechanized, mold-based process. An aluminum alloy blank is heated to the forging temperature (typically below the melting point but achieving excellent plasticity) and placed in the lower half of a forging die. The upper half of the die closes rapidly under immense pressure (from a forging machine), impacting or squeezing the blank to fill the entire mold cavity, thus forming the desired shape and size.

Advantages: Since it involves plastic deformation rather than melting, the internal metal grains flow and refine along the deformation direction, resulting in a dense structure. Forged parts typically have superior mechanical strength and thermal conductivity compared to die-cast parts.

5. Stamping

Stamping is a cold-working process that uses a punch press and specialized dies to apply pressure to metal sheets (usually coils or blanks), causing them to separate or plastically deform to achieve the desired shape and size.

Main Applications in Heat Sinks:

Manufacturing Heat Sink Fins: This is the most crucial and largest application. The dense fins on most mid-to-high-end air coolers are made by stamping. Stamping allows for various functional structures to be designed onto the fins, such as lock-in features (for buckle fins), airflow guides, and weight reduction holes, which are impossible with aluminum extrusion.

Manufacturing structural and auxiliary parts: This includes metal brackets for mounting the heat sink to the CPU/motherboard, spring screw bases (often made of high-strength steel or stainless steel), fan retention clips, and decorative covers.

Advantages: Stamping offers extremely high production efficiency. Modern high-speed presses can produce hundreds or even thousands of highly consistent parts per minute. After tooling is created, the per-part cost is very low, making it ideal for mass manufacturing.

Limitations: The high cost of designing and manufacturing precision progressive dies means it is only suitable for high-volume production. This process is limited to thin sheet metal parts and cannot produce solid, heavy 3D components (like heat sink bases).

6. Wire Cutting

Wire cutting service, or Wire Electrical Discharge Machining (WEDM), uses a continuously moving, extremely thin metal wire (typically molybdenum or copper) as the electrode. A pulsed spark discharge occurs between the wire and the workpiece, generating instantaneous high temperatures that locally melt and vaporize the metal to achieve cutting.

The electrode wire and workpiece maintain a tiny discharge gap, meaning there is no direct physical contact. This results in minimal cutting force, preventing workpiece deformation and allowing for the processing of very thin or easily deformed parts. Furthermore, it can cut any conductive material, regardless of its hardness.

• Application in heat sinks: Its most widespread and important use is in tooling manufacturing. WEDM is the preferred method for creating the complex, high-precision punch and die inserts in progressive dies used for stamping fins. These inserts are made of extremely hard, wear-resistant tool steel (e.g., SKD11, DC53), which traditional mechanical methods struggle to process, especially when forming sharp corners and fine gaps.
• Limitations: Processing speed is slow compared to high-volume processes like stamping or extrusion. There is also electrode wear, which is more noticeable with fast-moving wires, although slow-moving wires compensate through multi-cut techniques.

7. Skived Fin

Skiving or skive fin is a special cutting process for manufacturing thin metal fins. Unlike stamping (material separation) or extrusion (forcing material through a die), skiving uses a specialized skiving blade to precisely plane the fixed base plate. While cutting, the blade plows up and bends the removed metal into a vertical fin instead of cutting it off as scrap. This process has several advantages, including:

Zero contact thermal resistance: The fins and base are “grown” from a single block of material, forming a complete monolith. This ensures seamless heat transfer from base to fin tip, eliminating contact thermal resistance from mechanical joints or welding. This is the fundamental reason for the excellent performance of skived fin heat sinks.

High, thin, and dense fins: By adjusting the tooling and process parameters, fins with a very large aspect ratio (height-to-thickness ratio) can be produced. For example, it can easily create a dense fin array with a thickness of only 0.2 mm and a height exceeding 20 mm, which is unattainable with aluminum extrusion. The minimum fin thickness/gap is reportedly around 0.08 mm, though the height would be limited to 2-3 mm.

Excellent structural strength and rigidity: The monolithic structure makes the fin root very strong and less susceptible to deformation from vibration or impact, offering much greater stability than “through-fin” or “buckle-fin” assemblies.

Design flexibility: Fins of different heights and spacing can be created on the same heat sink to optimize airflow and thermal efficiency, for instance, by making the fins taller and denser over the core heat source.

Applications: Skived fin heat sinks are primarily used in applications demanding extreme thermal performance and reliability, such as high-power chip air coolers and the microchannel cold plates in liquid cooling heads.

Heat Sink Surface Finishes

Untreated metal heat sink surfaces have a rough structure that impedes heat transfer. Furthermore, the oxide layer acts as an insulator, and the metal itself is susceptible to corrosion in harsh environments. Surface treatments address these issues.

Anodizing

Anodizing service is suitable for aluminum and aluminum alloy heat sinks. It typically involves applying an external current in a sulfuric acid environment to form an oxide film on the heat sink surface. This effectively compensates for deficiencies in the aluminum alloy’s surface hardness and wear resistance. Unlike traditional electrostatic powder coating, anodizing does not affect the heat sink’s cooling effect, making it popular among manufacturers.

• Advantages: High hardness, wear and corrosion resistance, good insulation (breakdown voltage more than 200 V and available in various colors (commonly black). The process is mature, stable, and cost-controllable.
• Disadvantages: The oxide layer introduces some thermal resistance, slightly affecting ultimate heat dissipation (though overall performance is excellent). Color is primarily black, with other colors potentially having slightly inferior effects.
• Application: The mainstream choice for CPU/GPU cooler fins and bases.

Electroplating

Electroplating involves depositing a thin layer of another metal or alloy onto the heat sink’s metal surface. This process prevents surface oxidation and enhances wear resistance, conductivity, reflectivity, corrosion resistance, and aesthetics. It is an economical and scientific approach for providing a protective and decorative surface.

• Nickel Plating: Offers excellent corrosion resistance and a silver-white, textured appearance. Commonly used to protect copper bases or connectors. The coating is uniform, suitable for complex shapes, but a too-thick layer may reduce thermal efficiency (Nickel’s thermal conductivity is 90 W/mK).
• Chromium Plating: Provides high hardness and high reflectivity (beneficial for thermal radiation). It has a shiny appearance, often used for decorative parts.
• Silver Plating: Theoretically offers exceptional thermal conductivity 429 W/mK, close to pure copper’s 398 W/mK but the cost is high. Primarily used in top-tier or specialized applications, such as aerospace and RF devices.

Micro-Arc Oxidation

Micro arc oxidation is an advancement of anodizing that forms a superior coating. By matching the electrolyte and electrical parameters, an arc discharge generates instantaneous high temperatures and pressures, growing a modified ceramic coating on the surface of valve metals (like aluminum, magnesium, titanium) and their alloys. This coating consists mainly of the base metal oxide, supplemented by electrolyte components, and its anti-corrosion and wear resistance properties are significantly better than traditional anodizing.

• Advantages: Extremely high hardness (approaching ceramic), top-tier wear and corrosion resistance, good insulation, and a firm bond between the film and the substrate. It can significantly increase the surface emissivity of aluminum alloys.
• Disadvantages: High cost. The film is relatively thick, meaning its thermal conductivity is lower than anodizing, which negatively impacts cooling efficiency. The color is typically gray-white or dark gray.
• Application: Often used in special thermal scenarios with extremely high demands for wear and corrosion resistance, such as heat sinks in certain military, aerospace, or severe industrial environments.

How Can Getzshape Help

Getzshape is your essential manufacturing partner in producing heat sinks in aluminum, copper or other advanced materials. By leveraging our certified network and self-owned manufacturing shop, Getzshape can handle the CNC machining, die casting, and Wire EDM required for high-performance heat sinks, ensuring the final parts meet the requirements necessary to achieve next-generation heat efficiency.