Liquid Cooling Plate Manufacturing Process: From Materials to Precision Testing

As new energy vehicles, data centers, and energy storage systems experience explosive growth, the thermal performance of liquid cooling plates directly determines equipment stability and service life. A well-designed flow channel structure significantly improves temperature uniformity of battery modules, while advanced manufacturing processes ensure optimal flow path design, pressure resistance, and cost efficiency. This article provides a comprehensive overview of mainstream fabrication technologies, key techniques, and quality control points for liquid cooling plates.
1. Material Selection & Pre-Treatment
1.1 Mainstream Materials
Aluminum Alloys: The dominant choice for EV battery cooling plates, balancing thermal conductivity, light weight, strength, processability, and cost. 3003 aluminum alloy is widely used due to its mature technology and excellent comprehensive performance.
Copper Alloys: Pure copper (thermal conductivity: 401 W/m·K) is ideal for high-power scenarios (e.g., 800V high-voltage platforms), requiring nickel plating or anodization to prevent corrosion.
Composite Materials: High-strength aluminum alloy composites (3-layer structure: core + brazing layer + sacrificial layer) are used for applications demanding superior mechanical strength.

1.2 Pre-Treatment Process
Surface Degreasing: Ultrasonic cleaning (28–80 kHz) removes oil contaminants to ensure reliable welding and passivation.
Passivation: Chromate or chromium-free passivation (e.g., titanium salt solution) forms a nano-scale protective film, achieving 1,000+ hours of salt spray resistance.

2. Flow Channel Forming Technologies
2.1 Stamping Forming: High-Volume Production Core
Process Features: Servo presses deliver 60 strokes/min high-speed stamping with flow channel depth tolerance of ±0.05 mm. Ideal for medium/small cooling plates with 70%+ material utilization.
Case: BYD Seal CTB batteries adopt stamping plate direct cooling, boosting heat exchange efficiency by 40% via large-area flow channels.

2.2 Hydroforming: Complex Flow Channel Expert
Process Steps: Aluminum blank cutting (±0.1 mm) → hydraulic expansion (30–50 MPa, 2–10 seconds hold) → water jet trimming → vacuum brazing assembly.
Advantages: High design flexibility (serpentine, branched structures) with 20% lower pressure loss than stamped plates.
Case: CATL Kirin battery uses hydroformed large plates (1,200×800×50 mm), increasing cooling area by 4×.
2.3 Extrusion Forming: Cost-Effective Standard Solution
Process: Extrusion of aluminum profiles with preformed flow channels (e.g., harmonica tubes), followed by cutting and header welding.
Limitations: 30% lower cost than stamping but restricted to straight flow channels, suitable for energy storage container cooling plates.
2.4 3D Printing: Structural Innovation Breakthrough

Technology: Direct Metal Laser Sintering (DMLS) produces monolithic cooling plates without weld seams, withstanding 6+ bar pressure.
Case: Singapore’s CoolestDC’s 3D-printed plates use oblique fins to improve cooling efficiency by 20%, deployed in NVIDIA H100 GPU cooling systems.

3. Flow Channel Machining: Core of Thermal Performance
3.1 Mainstream Methods
Embedded Tube Process: Copper tubes are pressed into milled aluminum grooves (depth/diameter ratio ≤3:1) and fixed via brazing.
Pros: Zero leakage risk (seamless tubing), mature and cost-effective.
Cons: Limited flow channel flexibility; risk of galvanic corrosion between copper and aluminum.
Applications: Server liquid cooling, industrial inverter heat sinks.
Electrical Discharge Machining (EDM): Wire cutting (±0.01 mm precision) creates micro-channels in hard alloy molds for prototyping.
Chemical Etching: Photolithography + NaOH etching produces micro-scale channels for ultra-thin plates (≤0.5 mm).
3.2 Innovative Designs
Bionic Flow Channels: Valeo’s shark fin-shaped channels enhance coolant turbulence, increasing heat transfer coefficient by 15%.
Branched Structures: Tesla 4680 battery modules use side-branched plates with 15° sub-branches to minimize temperature differentials.

4. Welding Technologies: Sealing & Strength Challenges
4.1 Vacuum Brazing: Mass Production Preferred
Principle: Aluminum-silicon brazing filler melts in a vacuum furnace, bonding flow channel plates and covers metallurgically.
Advantages: Supports complex micro-channels/fin structures (30%+ efficiency gain); lightweight aluminum construction withstands 10+ bar pressure.
Case: CATL CTP battery plates use vacuum brazing with deformation <0.1 mm.
4.2 Friction Stir Welding (FSW): High-Strength Bonding
Principle: A rotating pin generates frictional heat to plasticize materials, creating solid-state welds.
Advantages: Weld strength reaches 90%+ of base metal; eco-friendly (no filler wire/shielding gas).
Case: BYD Dolphin batteries use FSW to bond plates and enclosures, passing 20 bar pressure testing.
4.3 Stamping + Brazing Hybrid Process
Features: Combines stamping efficiency with brazing sealing; 40% lower cost than FSW.
Applications: Energy storage container plates, home appliance heat sinks.
4.4 Laser Welding
Advantages: Minimal heat-affected zone, 90%+ weld strength, no deformation/porosity; 5–10× faster than traditional methods.
Applications: EV batteries, industrial refrigeration, solar power systems.

5. Surface Treatment & Quality Assurance
5.1 Surface Treatment
Anodization: Sulfuric acid anodization (12–18V) creates 5–20 μm oxide films, 10× improved corrosion resistance and enhanced insulation (breakdown voltage >500V).
PTFE Coating: 50–100 μm polytetrafluoroethylene layers reduce friction coefficient to 0.1, minimizing coolant flow resistance.

5.2 Full-Process Testing
Leak Detection:
Helium mass spectrometry (1×10⁻⁹ mbar·L/s): EV battery plates, leakage rate ≤0.1 sccm.
Hydrostatic testing (1.5× working pressure, 30 min hold): Energy storage plates.
Internal Quality:
Ultrasonic C-SAM (50–200 MHz): Detects brazing defects (voids >5%) with 50 μm resolution.
CMM (±0.002 mm): Verifies channel dimensions and cell contact accuracy.

Conclusion
Liquid cooling plate manufacturing integrates material science, precision machining, and advanced welding technologies. From 3003 aluminum substrate preparation to helium leak testing, every process directly impacts cooling performance and reliability. As high-density thermal management demands grow, innovations like 3D-printed bionic channels and FSW monolithic structures will further enhance efficiency while reducing costs.