Extruded Liquid Cold Plates Manufacturing Process

Extruded liquid cold plates are integrated thermal management components manufactured through aluminum alloy extrusion processes. These liquid cold plates utilize liquid cooling media—such as water, water–glycol mixtures, or fluorinated fluids—to achieve efficient heat exchange.

The core feature of this cold plate liquid cooling technology is the formation of enclosed or multi-cavity internal flow channels within a single extruded aluminum profile. This structure provides low flow resistance, high pressure tolerance, compact design, and controlled cost, making it widely used in high power density electronics, battery packs, server liquid cooling, and power electronics.

Understanding how liquid cold plates work is critical: heat is conducted from the heat source into the cold plate body, transferred to the internal liquid flow channels, and then carried away by forced convection. Compared with tubed cold plates or brazed liquid cold plates, extruded designs offer higher structural integrity and reduced leakage risk.

Core Technical Characteristics

• One-piece extruded flow channels
  Seamless internal channels formed during extrusion eliminate weld seams and reduce leakage risk compared to brazed or tubed structures.

• High thermal conductivity materials
  Typically manufactured from 6061 or 6063 aluminum alloys with thermal conductivity ≥ 180 W/m·K. While copper cold plates offer higher conductivity, aluminum provides a superior balance of weight, cost, and corrosion resistance.

• Customizable flow channel designs
  Supports parallel channels, serpentine channels, and multi-cavity configurations, enabling flexible Liquid Cold Plate design.

• High pressure capability
  Typical operating pressure: 0.5–1.5 MPa
  Burst pressure: ≥ 3.0 MPa

• Lightweight structure
  20–40% lighter than CNC-machined or plate liquid cooling solutions.

• Excellent surface treatment compatibility
  Suitable for anodizing, electroless nickel plating, and functional coatings.

Typical Application Scenarios

• Electric vehicle battery pack water cooling plate systems

• Server CPU / GPU cold plates for electronics

• High-power laser cooling systems

• IGBT and power module cold plate cooling

• Energy storage system thermal management

Extruded Liquid Cold Plates Manufacturing Process

1. Raw Material Preparation Stage

Aluminum billet selection → Chemical composition analysis (spectrometer) → Mechanical property testing (hardness, tensile strength) → Pre-processing (cutting, end-face machining) → Material warehousing

• Alloy grades: 6061-T5 / T6, 6063-T5

• Billet diameter: φ100–φ300 mm

• Pre-processing accuracy:

• Length tolerance: ±1 mm

• End-face perpendicularity: ≤ 0.1 mm

2. Die Design and Manufacturing Stage

Flow channel design (CFD thermal simulation optimization) → Extrusion die design (port holes, welding chamber, bearing land) → Die steel selection (H13 hot work tool steel) → CNC rough machining → Heat treatment (quenching + triple tempering) → Precision machining (EDM, wire cutting) → Polishing (bearing land Ra ≤ 0.4 μm) → Trial extrusion validation

This stage directly determines the internal geometry and performance of extruded liquid cold plates, distinguishing them from brazed liquid cold plate structures that rely on post-assembly bonding.

3. Extrusion Forming Stage

Aluminum billet preheating (480–520°C) → Die preheating (450–480°C) → Extrusion parameter setup → Profile extrusion (speed 1–5 m/min) → Online quenching (air or mist cooling) → Pulling and straightening → Fixed-length cutting → Aging treatment (T5 / T6 condition)

The extrusion process enables consistent internal flow channels that support stable plate liquid cooling performance.

4. CNC Precision Machining Stage

Datum surface machining (coordinate system establishment) → End-face machining (flow channel opening) → Interface machining (inlet/outlet ports, mounting holes) → Sealing surface machining (flatness ≤ 0.05 mm) → Deburring → Cleanliness inspection

Machining Requirements

• End-face sealing grooves:

• Width tolerance ±0.02 mm

• Depth tolerance ±0.01 mm

• Threaded holes:

• Accuracy 7H

• Perpendicularity ≤ 0.05 mm

• Mounting surface flatness: ≤ 0.1 mm / 100 mm

• Cleanliness:

• Particles ≤ 100 pcs/m²

• Oil residue ≤ 10 mg/m²

5. End Cap Machining and Welding Preparation

End cap material selection (same or compatible alloy) → CNC finishing → Sealing surface finishing (Ra ≤ 1.6 μm) → Welding groove machining → Cleaning (ultrasonic cleaning) → Assembly positioning (dedicated fixtures)

End Cap Design Parameters

• Thickness: 3–10 mm (based on pressure requirements)

• Sealing methods:

• O-ring groove sealing

• Flat sealing

• Full welding sealing

• Welding options:

• Friction stir welding (FSW)

• Laser welding

• TIG welding

6. Welding and Sealing Stage

Welding process selection → Fixture assembly → Welding parameter setup → Automated welding execution → Post-weld heat treatment (stress relief) → Weld appearance inspection

Welding Process Comparison

• Friction Stir Welding (FSW):
  No filler material, high joint strength, ideal for long straight seams

• Laser Welding:
  Small heat-affected zone, high precision, suitable for complex seams

• TIG Welding:
  Cost-effective, flexible, suitable for small-batch custom liquid cold plate production

7. Pressure and Sealing Tests

• Helium leak testing

• Hydrostatic pressure testing (1.5× working pressure)

• Burst pressure testing (≥ 3× working pressure)

• Pressure cycle testing (100,000 cycles)

Test Standards

• Leak rate: ≤ 1×10⁻⁷ mbar·L/s (helium)

• Pressure holding: 1.5 MPa × 5 min, pressure drop ≤ 0.01 MPa

• Burst pressure: ≥ 3.0 MPa

• Pressure cycling: 0.2–1.0 MPa, 100,000 cycles without leakage

8. Surface Treatment Stage (Optional)

Pre-treatment (degreasing, pickling) → Anodizing (natural / black) → Sealing → Functional coatings → Baking and curing

Surface Treatment Options

• Anodizing:

• Thickness 10–15 μm

• Dielectric strength ≥ 500 V

• Electroless nickel plating:

• Thickness 10–20 μm

• Enhanced corrosion resistance

• PTFE coating:
  Improved chemical resistance

• Insulating coatings:
  For electrical isolation requirements

9. Cleaning and Drying Process

High-pressure DI water flushing → Ultrasonic cleaning (neutral detergent) → Triple-stage counterflow rinsing → Hot air drying (80–100°C) → Vacuum drying (high-reliability applications) → Nitrogen filling for oxidation prevention

Cleanliness Standards

• Particle size: ≤ 50 μm

• Non-volatile residue: ≤ 10 mg/m²

• Chloride ion content: ≤ 1 ppm

• Conductivity: ≤ 5 μS/cm

10. Accessory Assembly

Seal installation (silicone / FKM / EPDM) → Quick-connect fittings assembly → Temperature sensor installation (optional) → Pressure sensor installation (optional) → Labeling (product info and flow direction)

Accessory Requirements

• Seal materials: EPDM, FKM, silicone (−40°C to 150°C)

• Connector standards: DIN, SAE, JIS, BSPP

• Sensor accuracy:

• Temperature ±0.5°C

• Pressure ±1% FS

11. Finished Product Performance Testing

Thermal resistance testing (standard heat source method) → Flow resistance testing (flow vs. pressure drop curve) → Flow uniformity testing (multi-channel designs) → Durability testing (thermal and pressure cycling) → Final helium leak reinspection (100% inspection)

Performance Indicators

• Thermal resistance: 0.01–0.05 °C/W (design and flow dependent)

• Flow resistance: ≤ 50 kPa @ 10 L/min (typical)

• Flow uniformity deviation: ≤ 10%

• Operating temperature range: −40°C to 120°C

12. Final Inspection and Packaging

Visual inspection → Dimensional sampling (CMM) → Documentation preparation → Anti-corrosion packaging (VCI) → Shockproof packaging → Outer carton labeling

Packaging Specifications

• Single-unit protection: PE bag + VCI paper

• Packing orientation: Vertical placement

• Label content: Product ID, production date, flow direction, fragile marking

• Storage conditions: −10°C to 40°C, ≤ 70% RH

13. Documentation and Traceability

Certificate of conformity → Material certificates → Performance test reports → Process records → Traceability labels (QR code / barcode) → Installation and operation manual

Critical-to-Quality (CTQ) Control Points

Process Capability and Production Capacity

• Extrusion width: 30–300 mm

• Height: 10–100 mm

• Length: 500–6000 mm

• Minimum wall thickness:

• Channel wall: 1.0 mm

• Outer wall: 1.5 mm

• Surface roughness:

• Extruded surface: Ra ≤ 3.2 μm

• Machined surface: Ra ≤ 1.6 μm

Design Guidelines and Best Practices

Flow Channel Design

• Hydraulic diameter: 4–8 mm

• Aspect ratio: ≤ 10:1

• Bend radius: ≥ 1.5× channel width

• Bell-mouth inlet/outlet design

• Optional internal fins for enhanced heat transfer

Structural Design

• Uniform wall thickness

• Reinforcement ribs at critical locations

• Stress-free mounting layout

• Thermal expansion allowance

Material Selection Strategy

• General applications: 6063-T5

• High-performance applications: 6061-T6

• Harsh environments: Additional coatings

Cost Optimization

• Standardized cross-sections

• Improved material utilization

• Reduced secondary machining

• Economies of scale in mass production

With their one-piece extruded structure, low leakage risk, high reliability, and excellent cost efficiency, extruded liquid cold plates play an irreplaceable role in high power density cold plate cooling applications. As industries such as electric vehicles, data centers, 5G communications, and renewable energy continue to grow, Custom Cold Plates and custom liquid cold plate solutions will evolve toward higher performance, lighter weight, and smarter thermal management—providing robust and scalable solutions for next-generation liquid cooling systems.