Heatsinks · Liquid Cooling
Liquid cold plates
Aluminum liquid cold plates move heat from high-density devices into a coolant loop — the solution for power electronics, battery packs and EV charging where air cooling cannot keep up.
When to choose a cold plate
A liquid cold plate (or aluminum cold plate) transfers heat from a device into coolant circulating through internal channels. We build it by machining flow paths into aluminum plates and sealing them with friction stir welding or vacuum brazing for a leak-tight joint. Cold plate cooling beats air once power density pushes a finned sink past what a fan can remove in the available space.
Use one for inverters, IGBT stacks, energy-storage cells, battery modules and EV charging — anywhere heat per area is high and the envelope is tight.
Typical specs
- Seal: vacuum brazed / FSW
- Leak test: 100% helium, ≤1×10⁻⁹ mbar·L/s
- Flow: per your pump curve
- Finish: anodized or bare
Typical working pressure 3–10 bar (data-center loops 1–4 bar); plate size up to ~400 × 250 mm. Exact values confirmed against your spec.
How a liquid cold plate is made
- Define the thermal path. From your heat load, coolant and pressure we set channel layout, width and manifold position.
- Mill the channels. Flow paths and ports are CNC-machined into the base plate.
- Close the plate. A cover is joined by friction stir welding (FSW) or vacuum brazing for a clean, leak-tight seal.
- Machine ports & face. Inlet/outlet fittings and the mounting face are finished to print.
- Leak test. Every plate is pressure- or helium-tested before finish.
- Finish & clean. Anodize if specified; passages are flushed so no debris reaches your loop.
Capability & typical specs
Below are conventional ranges for our vacuum-brazed and FSW plates. Working pressure and plate size scale with your design — confirm exact limits against your drawing and coolant spec.
| Parameter | Typical capability |
|---|---|
| Construction | milled channels + FSW / vacuum braze |
| Brazing | fluxless vacuum braze, 4343/3003/4045 clad sheet, ~595–610 °C |
| Channel width | ~2–6 mm typical (down to 1 mm milled) |
| Working pressure | 3–10 bar typical; data-center loops 1–4 bar |
| Proof / burst | hydrostatic proof ≥1.5× working; burst > 20 bar |
| Flow uniformity | ±5% typical across plate |
| Plate size | up to ~400 × 250 mm typical |
| Leak test | 100% helium MS, ≤1×10⁻⁹ mbar·L/s; + hydrostatic proof |
Tube-in-plate, embedded and milled-channel
Three ways to build a cold plate: a copper or stainless tube pressed into a milled groove (tube-in-plate), a fully milled channel closed by FSW or vacuum brazed cover, or an embedded serpentine for high pressure. Tube-in-plate is simple and cheap at low volume; a milled and brazed plate gives the most uniform flow and the highest pressure rating. We pick the method from your pressure, coolant and volume rather than defaulting to one.
Cold plate vs air heatsink
A finned air sink is cheaper and simpler, but its capacity is capped by fin area and airflow. A liquid cooling plate carries heat away through fluid at a much higher rate, so it fits higher power in a smaller footprint. Choose liquid when a fan-plus-fin stack would be too large, too noisy, or simply unable to hold the device temperature. For lower loads, an extruded or CNC machined air sink is usually enough.
Where liquid cold plates are used
Power electronics
Inverter and IGBT cooling where density outruns air — the core cold plate application.
Energy storage
Battery cooling plate modules for cells and packs, holding temperature spread low across the bank.
EV charging
Charge-point power modules and onboard converters needing compact liquid loops.
Server & data center
Server cold plate loops for high-TDP CPUs and accelerators in rack cooling.
Thermal & design notes
Design for a liquid cold plate
- State the coolant. Water-glycol, dielectric fluid or pure water changes material and seal choice — tell us early.
- Give flow rate and pressure limits. They set channel size and manifold; we design to your pump curve, not a guess.
- Define the hot spots. Mark where heat enters so channels are dense where it matters and sparse where it doesn't.
- Pick the seal with pressure. FSW and vacuum braze both seal well; braze leads at high pressure and complex paths.
- Plan the interface. Flatness and TIM at the device face decide how much heat actually reaches the plate.
How to specify a cold plate
Send thermal load (watts and ΔT), coolant type, flow rate and pressure, inlet/outlet position and the envelope. For a battery cooling plate or server loop, also give cell or device pitch so channels line up. We return a flow-path proposal and a DFM note before any build.
Frequently asked questions
Liquid cold plate or air heatsink — which?
Air wins on cost and simplicity at low power. A liquid cold plate wins when power density is high, the envelope is tight, or a fan-plus-fin stack cannot hold temperature. Rule of thumb: if the device needs a large or loud fan to stay cool, move to liquid. We can size both from your heat load and space.
What does vacuum brazed mean for a cold plate?
Vacuum brazing joins a milled base and cover in a furnace under vacuum, with a filler metal that flows into the joint without flux. We use aluminum brazing sheet — typically 3003 core with 4343 or 4045 cladding (about 8–12% silicon on each face) — heated to roughly 595–610 °C so the cladding flows and wets the joint. It gives a strong, clean, leak-tight seal and handles complex channels and higher pressure than a simple bonded cover. Friction stir welding (FSW) is the alternative for aluminum-to-aluminum plates and adds little heat distortion.
How are cold plates leak tested?
Every plate is helium leak-tested before finishing — a mass-spectrometer sniff or accumulation test that finds leaks down to about 1×10⁻⁹ mbar·L/s, far smaller than a pressure gauge can show — and we also run a hydrostatic proof hold at ≥ 1.5× the working pressure. We set both the test pressure and the acceptance limit to your acceptance plan, so a plate that passes is safe in your loop. Tell us the working pressure and we test above it.
Can you make a battery cooling plate?
Yes. Battery and energy-storage cooling plates are a standard build: milled or tube-in-plate channels sized to cell pitch, holding temperature spread low across the pack. Give cell layout, heat load and coolant and we propose the channel pattern and manifold.
What pressure can a cold plate handle?
It depends on construction — tube-in-plate, milled-channel with FSW, or vacuum brazed each rate differently — but a typical working pressure is 3–10 bar (data-center and server loops often 1–4 bar). We design to your stated working pressure with margin, hydrostatic-proof to ≥ 1.5× working (burst typically above 20 bar), and helium-test the seal. Confirm the pressure and coolant and we return the rated build.
What do you need to quote a liquid cold plate?
Thermal load (watts and allowed ΔT), coolant type, flow rate and pressure, inlet/outlet position and envelope. A drawing gets the tightest quote; describe the load and we propose the flow path and price.
Quote a liquid cold plate
Send thermal load, coolant and envelope — we design the flow path.