1. Material Selection

• Base Material:
  • High-purity copper (e.g., C11000 electrolytic tough pitch copper, thermal conductivity ≈401 W/m·K) is used for superior heat transfer.
  • Copper alloys (e.g., C10100 oxygen-free copper) may be preferred for ultra-high conductivity in extreme applications.
• Material Form:
  • Typically starts as a solid copper block or slab (thickness: 10–30 mm) with uniform grain structure to ensure consistent machining performance.

2. Skiving fin Process Basics

(1) Machine Setup

• Single-Point Cutting Tool:
  • A high-speed steel (HSS) or carbide blade with a sharp edge (radius ≤0.02 mm) and precise angle (e.g., rake angle: 5–15°, clearance angle: 2–5°) is used.
  • The blade is mounted on a spindle that rotates at high speed (e.g., 1000–3000 RPM) while the copper block is fed linearly (feed rate: 0.1–0.5 mm/rev).
• Coolant/Lubricant:
  • Water-based or synthetic coolants are applied to reduce friction, dissipate heat, and improve surface finish (avoids blade wear and copper smearin

(2) Fin Geometry Control

• Fin Thickness:
  • Typically 0.05–0.8 mm (thinner fins increase surface area but risk bending or breaking).
  • Achieved by adjusting the blade depth of cut (DOC) and feed rate.
• Fin Height:
  • Ranges from 2–50 mm (limited by the copper block’s initial thickness and structural stability).
  • Taller fins require stiffer tooling to prevent vibration-induced defects.
• Fin Pitch (Spacing):
  • Usually 1.0–3.0 mm (dependent on airflow requirements; tighter pitches improve heat dissipation but reduce airflow).
  • Controlled by the linear feed rate of the copper block.

(3) Surface Finish and Tolerance

• Roughness (Ra):
  • A smooth finish (Ra ≤1.6 μm) is critical to minimize air resistance and enhance heat transfer (rough surfaces trap boundary layer air).
• Dimensional Tolerance:
  • Fin thickness and pitch must be precise (±0.05 mm) to ensure uniform airflow and compatibility with CPU heat spreaders.

3. Design and Structural Considerations

(1) Base Plate Integration

• The skived fins are integral to the base plate, creating a monolithic structure with minimal thermal interface resistance (unlike bonded or soldered fins).
• The base plate thickness (3–5 mm) is optimized for direct contact with the CPU (via thermal paste) and to evenly distribute heat to the fins.

(2) Airflow Optimization

• Asymmetric Fin Shapes:
  • Fins may be tapered or angled (e.g., 5–15°) to guide airflow and reduce turbulence.
• Chamfered Edges:
  • Rounded or chamfered fin tips (0.1–0.3 mm radius) minimize air resistance and noise.
• Fin Alignment:
  • Fins are aligned parallel to the airflow direction (e.g., perpendicular to the CPU fan) for optimal convective heat transfer.

(3) Thermal Performance Limits

• Heat Flux Constraints:
  • Copper’s high conductivity allows efficient heat spreading, but skived fins may struggle with ultra-high power CPUs (>250 W) without additional features like embedded heat pipes or vapor chambers.

4. Post-Processing Steps

(1) Deburring and Straightening

• Mechanical Deburring:
  • Fins are brushed or tumbled to remove burrs from cutting edges (critical for safety and airflow).
• Thermal Stress Relief:
  • Annealing (heating to 200–300°C for 1–2 hours) may be used to relieve machining-induced stresses and prevent fin warping.

(2) Surface Treatment

• Nickel Plating:
  • Applied to prevent oxidation (copper tarnishes easily) and improve compatibility with solder (if integrating heat pipes later).
• Black Anodization (for Aluminum-Copper Hybrids):
  • In rare cases, copper fins may be bonded to an aluminum base, with anodization enhancing corrosion resistance (though pure copper sinks typically skip anodizing).

(3) Quality Control

• Visual Inspection:
  • Check for bent fins, uneven spacing, or blade marks that could disrupt airflow.
• Thermal Testing:
  • Use a heat source (e.g., simulated CPU) and an airflow rig to measure temperature rise and pressure drop across the sink.

5. Advantages of Skived Copper Fins

1. Monolithic Structure:
   • No thermal interface resistance between fins and base, unlike bonded or stamped fins.
2. High Aspect Ratio Fins:
   • Thin, tall fins maximize surface area without compromising structural integrity (vs. extruded or folded fins).
3. Design Flexibility:
   • Custom fin geometries (e.g., varying pitch or thickness along the sink) can be tailored for specific CPU layouts.
4. Scalability:
   • Suitable for mass production with automated CNC skiving machines (lower cost than extruded copper fins for low-to-medium volumes).

6. Challenges and Limitations

1. Material Waste:
   • Skiving generates significant copper swarf (up to 30% material loss), increasing costs (mitigated by recycling).
2. Tool Wear:
   • Carbide blades degrade after machining ~50–100 sinks, requiring frequent replacement (HSS blades last fewer cycles).

1. Fin Thickness Limits( Vansim's skiving fin capability can manufacturing the fins thickness as min as 0.05mm):
2. 
   • Below ~0.2 mm, fins are prone to tearing or excessive burring, limiting surface area gains.
3. Thermal Bottlenecks:
   • For CPUs >200 W, skived copper alone may not suffice; hybrid designs (copper skived fins + heat pipes) are often used.

7. Comparison with Alternative Technologies