Copper Vapor Chamber Cold Plate CNC Machining Leak Tested 0.01mm Flatness

Dongguan Changxinda Precision Technology Co., Ltd. has machined custom parts to drawing since 2008. The plant runs 4-axis and 5-axis machining centers, turn-mill combined lathes and precision CNC lathes, employs more than 90 people, and exports 50 to 60 percent of output to industrial buyers in Europe, North America and Southeast Asia. ISO 9001:2015 certified, first article reports with ballooned drawings as standard.

A vapor chamber cold plate is a copper plate with an internal cavity, a wick structure and a small amount of working fluid sealed inside. Heat spreads across the cavity by phase change instead of conduction alone, so a 200 W device can be cooled by a plate that would otherwise need a much thicker copper block. This page covers the machining, brazing and leak testing route for custom cold plates.

Copper Grade And Why It Matters

Thermal performance starts with the material callout, not with the machining.

• C1100 oxygen free copper: the default for vapor chambers, because oxygen content below 10 ppm keeps the cavity clean and stops the wick from oxidising during brazing.
• C1020 and C11000: acceptable for solid cold plates without an internal cavity, where conductivity matters more than brazeability.
• Copper to aluminum hybrids: machined as a bimetallic assembly when weight has to come down, with the joint designed so the thermal expansion mismatch is carried by the braze rather than by the screws.
• Nickel plating: applied on request for coolant compatibility, with the plating thickness recorded so that fin gaps do not close up.

Machining The Cavity And The Fins

• Cavity depth from 2 mm to 12 mm, held to 0.05 mm so the internal volume stays inside the design window
• Pin fins and straight fins from 0.8 mm width, cut with a relieved cutter and a light radial step to avoid deflection
• Copper is gummy, so cutters are polished and rake angles are chosen for the material rather than borrowed from aluminum programs
• Sealing land width 3 mm minimum, flatness 0.02 mm, since the braze joint relies on contact across the whole land
• Threaded ports and mounting holes machined after the cavity so that no chip is trapped inside the sealed volume

Brazing And Leak Testing

The plate is only as good as its seal. Brazing and testing are treated as one operation, not two.

• Vacuum brazing in a controlled furnace with a copper or silver based filler, and a recorded thermal profile per batch
• Helium leak test on every plate, with the rejection threshold agreed before the first batch
• Pressure hold test at 1.5 times the working pressure for plates that will carry coolant
• Flow test on liquid cooled versions, with pressure drop recorded and compared to the drawing value
• Flatness re-checked after brazing, because furnace cycles relax the plate and move the mounting face

Interface Flatness And Thermal Contact

A cold plate that is not flat performs like a plate with a smaller area, so the mounting face is the last operation and the first inspection item.

• Mounting face flatness 0.02 mm over the die footprint, 0.05 mm over the full plate
• Surface roughness Ra 0.8 on the contact face for thermal grease interfaces, Ra 1.6 for thermal pads
• Hole pattern referenced to the die outline, not to the plate edge, so the plate can be flipped without changing the stack
• Screw counterbores spot faced so that fastener torque does not bow the plate
• Plates supplied as a matched set with the heat spreader when both are machined in the same batch

Custom Design Inputs

• Plate sizes from 30 x 30 mm to 400 x 400 mm, thickness from 4 mm
• Heat load from 30 W to 800 W, with wick and fluid charge selected by the thermal requirement rather than by catalogue
• Ports: G1/8, G1/4, NPT, quick disconnect bodies or barbed fittings, positioned to clear the enclosure
• Mounting patterns to your board or chassis drawing, with dowel holes for repeatable location
• Laser marking of serial number and flow direction arrow on the edge of the plate
• Prototype quantity from 5 pieces, since brazing and testing need a small batch to be meaningful

Delivery And Documentation

• Prototype cold plates: 10 to 15 working days including brazing and helium leak test
• Batch of 50 to 500 pieces: 15 to 25 working days, with brazing in lots of 50 to keep the furnace profile stable
• Documentation pack: material certificate, braze profile record, leak test record per serial number, flatness report
• Packaging in individual foam cavities with port caps fitted, so no particle enters the loop in transit
• Written notice at least 5 working days before the ship date if the braze lot needs to be repeated

Questions From Thermal Engineers

Can you machine a vapor chamber from a solid block instead of brazing two halves?

For thin plates we machine the cavity from one side and braze a cover plate, because a monoblock cavity cannot be closed after machining. For thick plates with simple channels, a monoblock design with a welded or brazed plug is sometimes cheaper, and we will quote both routes.

Who owns the wick and the fluid charge?

You do. Send the wick specification and the charge mass, or send a working sample and we will match its internal volume. We machine, braze and test to your thermal design.

How do you prove the plate does not leak?

Every plate gets a helium leak test with a recorded rejection rate, and liquid cooled plates also get a pressure hold test at 1.5 times working pressure. Both records ship with the plate.