An FSW liquid cold plate (friction stir welded liquid cold plate) is a sealed thermal management heat exchanger manufactured by joining aluminum cover plates using a rotating tool that generates frictional heat to create a solid-state weld – producing leak-proof, porosity-free joints without melting the base material. FSW is one of three primary cold plate manufacturing processes alongside vacuum brazing and tube embedding, each suited to different thermal requirements, production volumes, and cost targets. ToneCooling manufactures custom cold plates using all three processes – FSW, vacuum brazing, and CNC machining – under one roof in Huizhou, Guangdong, China. This guide compares all three methods with real thermal performance data to help engineers select the optimal process. ISO 9001 certified. MOQ 5 pcs prototype.
Last Updated: 2026-04-14 | Author: ToneCooling Thermal Engineering Team
What Is Friction Stir Welding (FSW) for Cold Plates?
Friction stir welding is a solid-state joining process invented by The Welding Institute (TWI) in 1991. A non-consumable rotating tool is plunged into the joint line between two aluminum plates, generating frictional heat (80-90% of melting point) that plasticizes the material without melting it. The softened material is mechanically mixed by the tool’s pin, creating a solid-state bond as the tool traverses along the weld path.
For liquid cold plates, FSW joins a machined base plate (containing coolant channels) to a flat cover plate, sealing the internal flow passages. Key advantages:
- Zero porosity: No melting means no gas entrapment – leak-proof by design
- No filler material: Parent material only – no brazing alloy contamination risk
- Minimal distortion: Lower heat input than fusion welding – flatness maintained within 0.1mm
- High joint strength: 80-95% of parent material tensile strength (vs 30-60% for brazed joints)
- Aluminum-to-aluminum: Ideal for 6061-T6 and 6063-T5 alloys used in most cold plates
What Is Vacuum Brazing for Cold Plates?
Vacuum brazing joins cold plate components in a controlled atmosphere furnace at 10⁻² to 10⁻&sup4; Pa vacuum, using a filler metal (typically aluminum-silicon alloy for aluminum plates, or silver-copper for copper plates) that melts at a temperature below the parent material’s melting point. The molten filler flows into joint gaps by capillary action, creating sealed bonds upon cooling.
For liquid cold plates, vacuum brazing enables complex internal micro-channel geometries impossible to achieve with FSW:
- Complex channels: Multi-layer, serpentine, and pin-fin micro-channels with 0.15-0.5mm wall thickness
- Copper compatibility: Works with both aluminum AND copper (FSW is limited to aluminum)
- Multi-layer assembly: Can join 3+ layers in a single braze cycle
- Micro-channel density: Channel pitch as fine as 0.3mm for maximum heat transfer
- Highest thermal performance: 0.02-0.05°C/W achievable with optimized micro-channels
FSW vs Vacuum Brazing vs Tube Embedding: Complete Comparison
This comparison uses ToneCooling production data across hundreds of cold plate projects:
| Factor | FSW (Friction Stir Welding) | Vacuum Brazing | Tube Embedding (Press-fit) |
|---|---|---|---|
| Materials | Aluminum only (6061, 6063) | Aluminum + Copper + Stainless | Cu tube in Al/Cu base |
| Thermal resistance | 0.06–0.12°C/W | 0.02–0.05°C/W (best) | 0.10–0.20°C/W |
| Max heat flux | 50 W/cm² | 100+ W/cm² | 30 W/cm² |
| Channel complexity | Simple (parallel/serpentine) | Complex (micro-channel, pin-fin) | Simple (tube path) |
| Min channel width | 2mm | 0.3mm | Tube OD (4-12mm) |
| Joint strength | 80-95% of parent (best) | 30-60% of parent | Mechanical (press-fit) |
| Leak reliability | Excellent (solid-state) | Good (requires QC) | Moderate (O-ring dependent) |
| Flatness after joining | <0.1mm | <0.05mm (post-machining) | <0.03mm (no heat) |
| Tooling cost | $500–2,000 (FSW tool) | $1,000–5,000 (braze fixture) | $200–800 (lowest) |
| Unit cost (500 pcs) | $15–60 (lowest for Al) | $30–150 | $10–40 |
| Production MOQ | 100 pcs | 50 pcs | 20 pcs |
| Prototype MOQ | ToneCooling: 5 pcs for all processes | ||
| Best application | Large Al plates, EV battery, moderate heat | GPU/CPU high-flux, copper, micro-channel | Low-cost, moderate heat, simple layout |
When to Choose Each Process
Choose FSW When:
- Material is aluminum (6061-T6 or 6063-T5)
- Cold plate area is large (>200mm x 200mm)
- Channel geometry is simple (parallel or serpentine)
- Cost is a primary concern at 500+ production volume
- Application: EV battery packs, industrial power electronics, telecom equipment
Choose Vacuum Brazing When:
- Material is copper (C1100/C1020) OR aluminum requires micro-channels
- Thermal performance must be below 0.05°C/W
- Internal channel geometry is complex (multi-layer, pin-fin)
- Application: NVIDIA GB200/H200 GPU cooling, IGBT power modules, laser diodes, medical imaging
Choose Tube Embedding When:
- Budget is severely constrained
- Heat load is moderate (<200W per cold plate)
- Coolant is corrosive (stainless steel tube option)
- Application: LED lighting, low-power electronics, industrial cooling
ToneCooling Cold Plate Manufacturing Capabilities
| Process | Equipment | Max Size | Tolerance | Leak Test |
|---|---|---|---|---|
| FSW | Gantry FSW machine, 3-axis | 1200 x 600mm | ±0.05mm | Pressure decay + He leak |
| Vacuum Brazing | 10⁻&sup4; Pa furnace, 1100°C max | 800 x 500mm | ±0.03mm (post-CNC) | Helium mass spectrometry |
| CNC Machining | 5-axis, ±0.01mm | 1000 x 500mm | ±0.02mm | Pressure decay |
| Tube Embedding | Hydraulic press + CNC | 1500 x 800mm | ±0.1mm | Pressure decay |
Real-World Performance Comparison: ToneCooling Data
Measured thermal resistance at 1.5 LPM flow rate, 50/50 EGW coolant per ASHRAE W55 guidelines:
| Application | Process | Material | Rth (measured) | TDP Handled |
|---|---|---|---|---|
| EV Battery Pack (400x300mm) | FSW | Al 6061-T6 | 0.08°C/W | 500W |
| IGBT Module (62x108mm) | Vacuum Brazed | Cu C1100 | 0.03°C/W | 850W |
| Server CPU (LGA4677) | Vacuum Brazed | Cu C1020 | 0.04°C/W | 350W |
| GPU GB200 Superchip | Vacuum Brazed | Cu C1100 | 0.02°C/W | 1200W |
| Telecom RF Module | Tube (Cu in Al) | Al+Cu | 0.15°C/W | 150W |
| LED Heat Sink (200x200mm) | FSW | Al 6063-T5 | 0.12°C/W | 200W |
Why ToneCooling for Cold Plate Manufacturing
- All 3 processes in-house: FSW + vacuum brazing + CNC – no outsourcing delays, single-source quality control
- Lowest prototype MOQ: 5 pieces for ANY process, 7–15 day delivery
- Free CFD simulation: ANSYS Fluent thermal analysis with every custom project
- Process recommendation: ToneCooling engineers analyze your thermal requirements and recommend the optimal manufacturing process – not just the one they happen to have
- ISO 9001 + PPAP: Automotive, defense, and aerospace documentation available
- Tsinghua validated: Selected by China’s #1 university for precision thermal components
About ToneCoolingCooling
ToneCooling (Guangdong ToneCooling Precision Manufacturing Co., Ltd.) is a National High-Tech Enterprise founded in 2004 in Dongguan, China. New 30,000m² factory (RMB 80M investment) with 80+ CNC machines, 3 FSW systems, vacuum brazing furnaces including 1.2M×68M tunnel brazing line. 200+ employees (40%% technical), 46 patents (14 invention + 32 utility). Certified: ISO 9001 + ISO 14001 + IATF 16949. R&D partnerships with Tsinghua University, NUDT, HUST. Global: ToneCooling Texas LLC (USA), ToneCooling Australia Pty Ltd.
Request Cold Plate Quote
Not sure which process is right for your application? Send us your thermal requirements and ToneCooling engineers will recommend FSW, vacuum brazing, or tube embedding based on your specific needs – with free CFD analysis.
➔ Get Cold Plate Manufacturing Quote (48h Response) | info@tonecooling.com | US: +1 (832) 720-7542 | AU:
Frequently Asked Questions
What is an FSW liquid cold plate?
A liquid cold plate manufactured using friction stir welding – a solid-state joining process that seals internal coolant channels by mechanically mixing aluminum without melting. Produces zero-porosity, leak-proof joints at 80-95% of parent material strength.
FSW vs vacuum brazing: which is better for cold plates?
FSW is better for large aluminum plates, lower cost at volume, and simple channel geometries. Vacuum brazing is better for copper, micro-channels, complex multi-layer designs, and maximum thermal performance (0.02 vs 0.06 deg C/W). ToneCooling offers both processes in-house.
What thermal resistance can FSW cold plates achieve?
ToneCooling FSW cold plates achieve 0.06-0.12 deg C/W at 1.5 LPM flow rate depending on channel geometry and size. Vacuum brazed designs achieve 0.02-0.05 deg C/W for higher-performance applications.
Can FSW join copper cold plates?
FSW is primarily for aluminum (6061, 6063). Copper cold plates require vacuum brazing or CNC machining. ToneCooling manufactures both aluminum FSW and copper vacuum brazed cold plates.
Which cold plate process is cheapest?
Tube embedding is cheapest ($10-40/unit). FSW is cheapest for aluminum ($15-60/unit at 500+). Vacuum brazing is highest cost ($30-150/unit) but delivers best thermal performance. ToneCooling recommends based on your thermal and cost requirements.
