Cold Forged Heat Sinks

Selecting the appropriate material is a critical design decision that impacts thermal performance, mechanical robustness, manufacturability, and cost. Cold forging is compatible with a range of high-conductivity aluminum and copper materials, each with distinct trade-offs.

• Thermal conductivity: 200–210 W/m·K
• Mechanical strength: Moderate
• Cost: Moderate

Aluminum 6063 is the most commonly used alloy for cold-forged heat sinks due to its balanced combination of thermal performance, mechanical strength, corrosion resistance, and consistency in supply. Its mechanical properties make it well-suited for applications requiring good structural rigidity, precise tolerances, and post-forging secondary machining or mounting features.

• Thermal conductivity: ~230 W/m·K (higher than 6063)
• Mechanical strength: Lower (softer material)
• Cost: Low

Aluminum 1070 offers higher thermal conductivity and lower raw-material cost compared to 6063, making it attractive for thermally driven designs where mechanical strength is less critical. However, its softer nature results in reduced stiffness and lower resistance to mechanical stress, which may limit its suitability for applications involving heavy clamping forces, vibration, or demanding structural requirements.

• Thermal conductivity: 390–400 W/m·K
• Mechanical strength: High
• Cost: High

Copper provides the highest thermal conductivity among commonly forged heat-sink materials and is used in applications with extreme heat flux or tight thermal margins. Cold forging produces a dense, pore-free copper structure with excellent heat spreading characteristics. Due to material cost, weight, and tooling considerations, copper is typically reserved for specialized or performance-critical designs.

Surface finishing affects corrosion resistance, thermal performance, electrical conductivity, solderability, and long-term reliability. The optimal finish depends on material choice, operating environment, and system-level requirements. Below are commonly specified surface finishes for cold-forged aluminum and copper heat sinks.

• Aluminum
  • Anodization – MIL-A-8625, Type II Class 1 (clear finish): Cost-effective corrosion protection.
  • Anodization – MIL-A-8625, Type II Class 2 (black finish): Improves heat dissipation in natural convection.
  • Electroless Nickel Plating – ASTM B733-04, SC0 (0.5µm) or SC1 (5µm): Thin plating for solderable or conductive surfaces.
  • Natural Finish (not recommended): For prototypes, testing, or non-critical applications only.
• Copper
  • Anti-Oxidation (standard finish): Recommended unless plating is required; provides basic protection against oxidation.
  • Electroless Nickel Plating – MIL-C-26074E, Grade A (25µm): Maximum corrosion resistance for harsh environments.
  • Electroless Nickel Plating – MIL-C-26074E, Grade B (13µm): Cost-effective coating with moderate corrosion protection.
  • Electroless Nickel Plating – ASTM B733-04, SC0 (0.5µm) or SC1 (5µm): Thin plating for solderable or conductive surfaces.

To ensure optimal manufacturability, performance, and cost effectiveness, consider the following design parameters when developing a cold-forged heat sink:

• Maximum Width/Length: 500 mm x 500 mm
• Maximum Height: 70 mm
• Minimum Base Thickness: 2.0 mm
• Minimum Gap Between Pins: 1.5 mm
• Clearance from Base Edge: 0.5 mm
• Aspect Ratio (Pin Height to Diameter): Up to 50:1

These guidelines maintain forging stability, tool life, and consistent pin geometry.

• Pin geometry selection: Choose round, elliptical, or custom profiles based on airflow characteristics and pressure drop targets.
• Pin height and density: These are the primary levers for increasing surface area, but must be balanced against airflow resistance.
• Impingement configurations: Dense pin arrays are particularly effective when a fan directs airflow vertically onto the heat sink.
• Natural convection designs: Maintain adequate pin spacing to prevent boundary layer interference and stagnant zones.

• Integrate mounting bosses, alignment features, and structural supports directly into the forging when possible to minimize secondary machining.
• Through-holes, precision bores, and tight-tolerance features should be machined after forging for best dimensional control.
• Early collaboration between thermal and mechanical design teams can significantly reduce iteration cycles.

Modern CFD tools such as Icepak, Simscale, or FloTHERM should be used early in the design process to evaluate:

• Airflow distribution
• Pressure drop
• Junction temperature
• Hot spots on the heatsink or in the system

Simulation-driven optimization helps ensure the final design meets thermal targets without unnecessary material or excessive design iterations.

In high heat-flux or compact designs, solid aluminum or copper bases can limit heat spreading from localized hotspots. Integrating heat pipes or vapor chambers with a cold-forged pin-fin heat sink combines very high effective spreading conductivity (often exceeding 20,000 W/m·K for heat pipes) with the large convective surface area of dense pin arrays.

This approach is especially valuable when:

• Heat sources are small or centrally located (high local heat flux)
• Base temperature gradients dominate overall resistance
• Increasing airflow (noise or power constraints) is not feasible
• The mechanical envelope cannot increase

The dense, pore-free, dimensionally stable forged base provides a reliable, low-resistance interface for two-phase devices.

Heat pipes (typically copper) transport heat rapidly from the evaporator region at the hotspot to the condenser region beneath the pin array.

• Embedded Heat Pipes: Grooves are machined into the base; heat pipes are press-fit and soldered or bonded in place; provides minimal interface resistance and strong mechanical retention; well-suited for linear or elongated heat sources.
• Surface-Mounted Heat Pipes: Heat pipes are bonded or soldered directly to the base surface; simpler machining and flexible layout, with slightly higher interface resistance than embedded designs.

Vapor chambers provide two-dimensional heat spreading and are effective for multi-source or large-area hotspots.

The most common integration method is soldering the vapor chamber directly to the forged base to minimize interface resistance. Mechanical attachment with high-performance TIM may be used when reworkability is required.

The flatness and dimensional stability of cold-forged bases support uniform thermal contact across the vapor chamber interface, reducing spreading resistance and enabling more uniform utilization of dense pin-fin arrays.

Cold forging forms aluminum or copper pin-fin heat sinks at room temperature using extremely high compressive forces—typically hundreds to thousands of tons—in a single high-speed stroke (often 15–20 seconds). The base and pin array are formed simultaneously as one continuous, monolithic structure.

Because the material is plastically deformed rather than melted or assembled, the process provides several structural and thermal advantages:

• Monolithic construction → no fin-to-base interface
• No casting porosity, voids, or internal defects
• Continuous grain flow from base into pins → improved mechanical strength and consistent thermal conduction
• High dimensional repeatability (±0.05 mm typical)

The cold working process also refines and aligns the metal’s grain structure, improving mechanical strength and supporting consistent thermal conduction throughout the heat sink.

Unlike extrusion, die casting, stamping, or bonded-fin assembly, cold forging does not rely on molten metal flow or secondary bonding. The resulting structural and metallurgical continuity enables the high aspect ratios, dense pin arrays, and long-term reliability discussed earlier.

We currently offer the following standard heat sinks:

• Round Pin Heat Sinks
• Elliptical Pin Heat Sinks

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Please let us know your requirements or thermal challenges, and our experienced engineers can help you design the right heat sinks.