What Is An FSW Liquid Cold Plate?
An FSW (Friction Stir Welded) liquid cold plate is a thermal management component that removes heat from high-power electronics using internal liquid coolant channels, joined through a solid-state welding process rather than melting or brazing. Metal sheets are machined to form precise flow channels, electronic components are mounted on the plate's surface, and coolant enters through an inlet, absorbs heat as it flows across the channels, and exits through an outlet—carrying the heat away without fans, refrigerant, or moving parts near the electronics themselves.
What Makes Friction Stir Welding Different
Most liquid cold plates are joined using vacuum brazing, which relies on melting a filler metal to bond the plates together. FSW instead uses a rotating tool that generates frictional heat and mechanical pressure, softening the base metal just enough to fuse the two plates into a single, monolithic structure—without melting either surface or introducing filler material or flux.
Because there's no flux or filler metal involved, there's no risk of residue clogging the internal channels or contaminating the coolant—a common failure point in brazed designs. The resulting weld typically reaches 85–95% of the base material's strength, with thermal conductivity loss kept below 5% and leakage rates under 1×10⁻⁹ mbar·L/s.
How An FSW Liquid Cold Plate Is Made
Manufacturing starts with high-precision CNC Machining, cutting complex flow channels, fins, or turbulators into the base plate to maximize contact area between the coolant and the heat source. A cover plate is then friction stir welded onto the base using a rotating tool with a specially shaped pin, fusing the two aluminum or copper components into a sealed, leak-resistant unit.
The exact welding parameters depend on the base material, since aluminum and copper respond differently to frictional heat and pressure:
| Key Parameters For Aluminum FSW | |
|---|---|
| Rotation Speed | 800–1600 RPM |
| Travel Speed | 200–800 mm/min |
| Plunge Depth | 0.1–0.3 mm |
| Pin Design | Threaded conical structure |
| Key Parameters For Copper FSW | |
|---|---|
| Rotation Speed | 1200–2000 RPM |
| Travel Speed | 50–200 mm/min |
| Axial Force | 8–15 kN |
| Preheat Requirement | 150–250°C |
Where FSW Liquid Cold Plates Are Used
Because FSW liquid cold plates offer quiet operation, stable cooling, and low sensitivity to ambient conditions, they're used across several industries where component temperature control is critical:
Medical equipment — life science instruments that require precise, stable temperature control for accuracy and reliability
Industrial automation — motors, drivers, and controllers that generate heat during continuous operation
New energy vehicles — battery management systems and motor controllers, where space is limited and cooling demands are high
Communication equipment — base stations, switches, and routers running under sustained high loads
Aluminum Or Copper: Which Material Fits Which Application
Material choice generally comes down to a trade-off between thermal performance, weight, and space. Aluminum alloys like 6061 offer a lighter, more cost-effective solution suited to applications like industrial lasers, where heat needs to be managed efficiently without adding excessive weight. Copper delivers stronger thermal conductivity—useful in space-constrained, high-density applications like data center server cabinets—though at a higher cost and weight. Some designs, such as those used in EV charging piles, combine copper and aluminum through dissimilar-metal FSW to balance thermal performance with long-term durability in outdoor conditions.
Common Questions About FSW Liquid Cold Plates
Can FSW handle complex internal flow channels?
Yes. High-precision CNC machining (±0.005mm tolerance) allows complex paths, pin fins, or spiral channels to be milled before welding, increasing the heat transfer surface area.
How is the cleanliness of the internal channels ensured?
Through a multi-stage process: ultrasonic cleaning before welding, the inherently clean flux-free FSW process itself, and post-weld nitrogen purging to fully dry the channels.
What's the typical lead time?
Prototypes are typically delivered in 2–3 weeks, with mass production timelines depending on volume and production capacity.
If you're evaluating whether an FSW liquid cold plate fits your application, sharing your power density, space constraints, and operating environment can help determine the right material and channel design for your project.
