CNC Machined Heat Sinks Manufacturing Process

A heat sink is a thermal management component designed to dissipate heat from electronic devices into the surrounding environment. In Heat Sinks for electronics, heat is transferred through conduction from the heat source (such as a CPU or power module) into the heat sink base, then dispersed via heat sink fins through convection and radiation.

Understanding what is a heat sink, how heat sinks work, and how heat sinks are made is essential when selecting solutions such as aluminum heat sinks, copper heat sinks, liquid cooled heat sinks, or custom heatsinks for industrial and electronic applications.

Among all manufacturing methods, CNC machined heat sinks offer the highest design freedom and precision, making them ideal for complex, high-performance, and low-volume applications where extruded heat sinks or heat sink extrusion cannot meet design requirements.

1. Raw Material Management Stage

1.1 Metal Billet Preparation

Material Selection
High thermal conductivity metals and composites are selected according to thermal and mechanical requirements:

• Aluminum alloys: AA6061-T6 / AA6063-T5 / T651

• Copper alloys: C1100 / C1020

• Composite materials: AlSiC, CuW

These materials are commonly used in aluminum heatsinks, copper heat sinks, and high-end industrial heat sink solutions.

Material Certification & Verification

• Material certificates verification

• Spectral composition analysis

• Example (AA6061): Si 0.4–0.8%, Mg 0.8–1.2%

Physical Property Testing

• Thermal conductivity:

• Aluminum ≥ 180 W/m·K

• Copper ≥ 380 W/m·K

• Hardness:

• 6061-T6: HB 95–100

• 6063-T5: HB 75–85

• Tensile strength:

• 6061-T6 ≥ 290 MPa

• 6063-T5 ≥ 175 MPa

Billet Pre-Treatment

• Stress relief (if required): 300°C × 2 hours, furnace cooling

• Surface flatness check: ≤ 0.1 mm / 100 mm

• Dimensional tolerance: ±0.5 mm (L × W × H)

1.2 Auxiliary Materials Preparation

• Cutting tools:

• Carbide tools (K-grade)

• PCD diamond tools

• Coated tools (TiN / TiAlN)

• Coolant systems:

• Water-soluble coolant (5–8%)

• Oil-based coolant for high-precision CNC heatsink machining

• Fixture materials:

• Aluminum fixtures

• Hydraulic expansion fixtures

• Vacuum clamping systems

2. Process Design and CAM Programming Stage

2.1 Machining Strategy Development

Process Route Planning

• Rough machining: High-speed milling (80–90% material removal)

• Semi-finishing: Contour machining with 0.1–0.2 mm allowance

• Finishing: Precision machining to final dimensions

Toolpath Optimization

• Contour machining: Step-over 0.5–2.0 mm

• Parallel toolpaths: 30–70% tool diameter

• Spiral toolpaths: Reduced tool entry impact

Deformation Control Strategies

• Symmetrical machining

• Layered cutting (≤ 0.5 mm per layer during finishing)

• Intermittent machining to minimize heat accumulation

2.2 CAM Programming

3D Model Processing

• Model repair and simplification

• Machining allowance setup:

• Roughing: 0.3–0.5 mm

• Finishing: 0–0.05 mm

• Feature-based machining region segmentation

Toolpath Generation

• Roughing:

• Depth of cut: 2–5 mm

• Feed rate: 800–1500 mm/min

• Finishing:

• Depth of cut: 0.1–0.3 mm

• Feed rate: 2000–4000 mm/min

• Corner cleanup using small-diameter tools

Post-Processing & Simulation

• NC code generation for specific CNC systems

• Collision and travel verification

• Machining time estimation (±10%)

3. Machining Preparation Stage

3.1 CNC Machine Setup

Machine Selection

• 3-axis vertical machining centers: Standard CNC machined heat sinks

• 4-axis / 5-axis CNC: Complex curved surfaces

• High-speed machining centers: Spindle ≥ 12,000 rpm for thin fins

Machine Accuracy Verification

• Positioning accuracy: ±0.003 mm

• Repeatability: ±0.001 mm

• Spindle radial runout: ≤ 0.003 mm

3.2 Fixture System Design

• Multi-point positioning fixtures (6-point principle)

• Flexible fixture systems

• Vacuum fixtures for thin-wall heat sink fins

Clamping Force Control

• Hydraulic clamping: 0.5–1.0 MPa

• Pneumatic clamping: 0.4–0.6 MPa

• Mechanical clamping: Torque controlled to ±0.1 Nm

4. CNC Machining Stage

4.1 Rough Machining

• Workpiece alignment using edge finders (±0.01 mm)

• Coordinate systems: G54–G59

• Primary datum surface machining (flatness ≤ 0.02 mm)

Rough Cutting Parameters

• Spindle speed: 8000–12,000 rpm

• Feed rate: 1500–3000 mm/min

• Depth of cut: 2–5 mm

• Step-over: 60–70% tool diameter

Process Monitoring

• Cutting force monitoring

• Tool wear tracking

• Cutting temperature ≤ 80°C

4.2 Semi-Finishing

• Uniform material allowance: 0.1–0.2 mm

• Pre-machining of holes and slots

In-Process Control

• On-machine probing

• Tool offset compensation

• Preliminary surface roughness inspection

4.3 Finishing (Critical Process)

Heat Sink Fin Machining

• Thin fin processing using φ1–φ3 mm end mills

• Spindle speed: 18,000–24,000 rpm

• Feed rate: 300–800 mm/min

• High-pressure internal coolant (≥70 bar)

Anti-Vibration Measures

• Tool overhang control (L/D ≤ 4)

• Variable feed strategy

• Helical interpolation

Mounting Surface Machining

• Face milling (φ40–φ80 mm cutters)

• Surface roughness: Ra ≤ 0.8 μm

• Flatness: ≤ 0.03 mm / 100 mm

Hole Machining

• Drilling with carbide drills

• Reaming to H7 tolerance

• Thread forming for high-strength threads

Special Structures

• T-slots and profiled grooves

• 5-axis curved surface machining

• Micro-structure machining (φ0.1–φ0.5 mm tools)

4.4 Advanced Machining Technologies

• High-speed machining:

• Spindle speed: 20,000–40,000 rpm

• Feed rate: 5000–15,000 mm/min

• Micro-milling:

• Accuracy: ±0.002 mm

• Surface roughness: Ra ≤ 0.1 μm

• Ultrasonic-assisted machining:

• Frequency: 20–40 kHz

• Amplitude: 5–20 μm

5. In-Process Quality Control

5.1 Online Inspection

• Touch probes for alignment and dimensional inspection

• Automatic tool compensation

• Laser scanning for surface profiles

• Vision systems for defect detection

5.2 Process Parameter Monitoring

• Cutting force sensors

• Vibration frequency analysis

• Tool and workpiece temperature monitoring

6. Critical-to-Quality (CTQ) Control Points

7. Process Capability and Lead Time

Total Lead Time: 18–31 working days
Capacity:

• 3-axis CNC: 10–30 pcs/day

• 5-axis CNC: 5–20 pcs/day

• Micro-machining: 1–5 pcs/day

8. Process Characteristics and Advantages

Technical Advantages

• Extremely high design freedom

• Micron-level precision

• Suitable for custom heatsink solutions

• Ideal for CPU heatsink, CPU heatsink fan, heatsink fan, heat sink with fan, and liquid cooled heat sink designs

Process Limitations

• Low material utilization (30–60%)

• High machining cost

• Not suitable for mass production

Recommended Applications

• Prototypes and validation

• Small-batch, high-value products

• Complex geometry heat sinks

• High-performance industrial heat sinks

Not recommended for:

• High-volume standardized products

• Cost-sensitive applications

• Simple extruded heat sink designs

This CNC machined heat sink manufacturing process is optimized for high-precision, complex, and low-volume heat sink production. By combining optimized machining strategies, strict process control, and advanced inspection methods, heat sink manufacturers can achieve superior thermal performance, dimensional accuracy, and long-term reliability. The process can be flexibly adjusted to balance performance and cost according to specific application requirements.