What is cold plates (water- cooled heat sink)?

High-end applications, such as electronic components used in high temperature environments, require an efficient cooling system that does not interfere with operation.

Cold plates (also known as water-cooled heat sinks) are used , as the most efficient cooling method, in vacuum chambers of vapor deposition equipment in the display manufacturing process and  protect electronic components from temperature environments of hundreds of degrees Celsius and thus provide a high level of performance and reliability to the equipment accordingly.

The cold plate with a water-cooled jacket structure heated in the vacuum chamber comes into contact with the cooling water circulating inside through a tube or passage (groove), which results in the entire cold plate being cooled, reducing the heat load by dissipating excess heat.

Cold plate of Kyoyu -SEISAKUSHO

Kyoyu Seisakusho’s cold plate has a water-cooled jacket structure made of aluminum, stainless steel and copper.

The method of joining the plate body and the water-cooled lid in the water-cooled jacket is specialised in Tig welding for stainless steel and friction stirring welding (FSW) for copper and aluminum. In addition, with advanced distortion technology, the ground contact with the heat source realises the optimal flatness and contributes to the improvement of cooling efficiency.

Production range

Material Aluminum, Stainless steel, Copper
Joining methods Tig welding, Vacuum brazing, Electron beam welding (EBW), Friction stirring welding (FSW)
Maximum size that can be manufactured Circular form:φ800mm
Rectangular form:Width 1,000 mm、Length 2,000 mm
Structure The jacket structure having grooves covering the lid from the above is main.
Shape Compatible with various external shapes and complex waterway shapes
Specifications All manufactured parts are custom-made with customer specifications

Product examples

Aluminum Cold Plate

This case is a prototype development product that has been requested through the homepage. The water-cooled groove is processed into the main body, the lid is attached from the top, and then joined by FSW After joining with frictional stirring welding, the surface in contact with the heat source provides plane accuracy by machining The ...

Round Stainless Cold Plate

After Tig welding with a water-cooled lid to the main body, distortion correction and machine finishing are performed.  After that, the distortion correction is done again to get flatness. Material SUS304 , SUS316 Size Diameter 400mm~900mm Industry Vacuum Industry Processing details Machining Center, Tig Welding

Copper Cold Plate

Pure copper is a difficult material, and warping occurs after cutting or joining. Therefore, in order to ensure the thickness of the water-cooled lid, distortion correction is necessary each time.It is also easy to scratch, so you need to pay close attention Material Pure Copper C1020 Size W300mm~400mm x L1000mm~1500mm Industry Vacuum Industry Processing details ...

Square Stainless Cold Plate

After Tig welding with a water-cooled lid on the main body, the distortion correction is performed to get flatness. Material SUS304、SUS316 Size W200mm~400mm x L500mm~1500mm Industry Vacuum Industry Processing details Machining Center, Tig Welding

Production process

Production process examples

Example 1: Copper Cold Plate

Product Customized Liquid Cold plate
Material Copper
Processing method Friction stir welding (FSW), Machining center

Process❶ Before welding (Preparation)

  1. On the main plate, the groove where the cooling water flows and the fitting part of the same depth as the thickness of the lid are machined.
  2. Cover the joint groove with a lid (tapping so that there is no step on the bonding surface)
Before welding (Preparation)

Process❷ FSW processing

At the time of joining, metal scrap is discharged around the joint by pressing force (1.2t) from the top of the tool and the force moving sideways. As shown in the image below, the joint marks by the tool remain (slightly discoloration due to frictional heat)

FSW processing

Process❸ After Finishing

1mm cutting from joined end face
The boundary of the joint cannot be determined as shown in the image below, and it can be understood that the main plate and the lid are integrated.

After Finishing

Example 2: Aluminum Cold Plate

Product Customized Liquid Cold plate
Material Aluminum (A6061)
Processing method Friction stir welding (FSW), Machining center

Process❶ Water cooling groove machining and Fitting step processing on the lid

Using a machining center, water cooling groove processing (groove through which cooling water flows) is performed on the main body plate.

After that, fitting step processing on the lid is carried out (step-machining to fit in the lid).


Process❷ Knock the lid

Knock the lid into the processed fitting step.


Process❸ FSW bonding

FSW junctions between the outer periphery of the lid and the water-cooled groove.
FSW bonding improves adhesion between the lid and the stepped surface.


Process❹ Finish cutting

Cut the outer periphery and FSW joint surface at the machining center.
This ensures the plane accuracy of the joint face.


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We can handle a wide range of services from technical consultation on product production and processing to consultation on specific estimates.

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Backing Plates by FSW(Friction Stir Welding)

Advantage 1: Uniform Cooling Performance

In order to make the lid thickness uniform after the surface finishing process, as shown in the figure, a dedicated press machine is used to correct the warping and distortion of the base material and the lid. After that, the finishing process is carried out. A uniform lid thickness will be realized by this process. If the thickness of the lid is uniform, the distance from the groove (cooling channel) to the top surface of the lid (contact face) is also constant, and it has a cooling performance with no variation.

If the finishing process is done from the contact area without correction with a press machine, the thickness of the lid at the time of completion will change depending on the place as shown in the figure. If there is a thick part and a thin part of the lid with respect to the groove (cooling channel), a temperature difference will be created due to the difference in thickness, and as a result, the cooling performance will vary.

Advantage 2: High Joints Reliability

The joints by FSW can be made with the lid onto the base material closely without gaps.
In fusion welding by an electron beam that heats the material above the melting point temperature, there are concerns in the reliability of the joints due to slag and bubble. And in the brazing process, there are concerns about joint failure due to brazing shortage. On the other hand, FSW, which is a solid phase joining, is heated and softened as a solid without melting, and then pressurized to be joined. So there is almost no slags, air bubble and thus joining defects will rarely occur. Therefore, it has realized high reliability at the junction of the base material and the lid.

Advantage 3: High-Mix Low-Volume(HMLV) Production

The parts used in the manufacturing equipment in production line are different from the ones in mass-produced products, and equipment-specific customized ones are also required. Since FSW is used utilizing a dedicated processing equipment, it can be used for high-mix low-volume production.
Our processing equipment is a specially made hybrid machine that can perform cutting and joining (FSW) on the same machine. We have an integrated production system from machining to joining, and we can manufacture products that guarantee high quality.

Advantage 4: High Material Strength

FSW can maintain high material strength. In the case of brazing, the entire material will become hot during the brazing process and the base material will soften. In some cases, the more bend with own weight, the weaker the strength of the material becomes. On the other hand, FSW is a solid phase joining, and the base material does not soften because there is no need to heat the entire material. In addition, the joining part has a material strength equal to or greater than that of the base material. In this way, FSW is a joining method that does not reduce the material strength of the base material.

First, please feel free to contact us.

We can handle a wide range of services from technical consultation on product production and processing to consultation on specific estimates.

Contact us

Things to consider when designing

1 Materials


Aluminum is excellent in terms of cost and weight. For example, the cost is about one-third in comparison to copper. In addition, it weighs only about one-third. On the other hand, compared to the thermal conductivity of copper 398W · m-1 · k-1, the thermal conductivity of aluminum is about half as much as 236W · m-1 · k-1. Although the cooling efficiency is inferior to copper, aluminum is suitable if you need a low-cost and lightweight cold plate.


The thermal conductivity of copper is 398W · m-1 · k-1, which is a high thermal conductivity compared to aluminum and stainless steel. For example, it is about 20 times that of stainless steel (SUS304) (16.7W · m-1 · k-1), and about twice that of aluminum (236W · m-1 · k-1). Therefore, if the heat dissipation performance is important, the use of copper is suitable.

Stainless steel

Stainless steel has high corrosion resistance. Compared to the use of copper or aluminum materials, an ion exchange unit is not required, and coolant (cooling water) management is easier. Therefore, if the maintainability of coolant is important, the use of stainless steel is suitable.

Temperature Uniformity

The cold plate doesn't just cool down. Depending on the location a uniform cooling function that does not vary is required. The cause of the cooling variation is the thickness of the lid of the groove in the cooling section. If the thickness of the lid varies from place to place, the temperature will vary and the function of the cold plate will decrease as you use it. In order to achieve uniform cooling properties, it is necessary to devise ways to keep the thickness of the lid constant and excellent processing technology to realize it.


In general, a water-cooled cold plates determines the coolant (cooling water) that can be used depending on the material . Because if you do not choose the appropriate coolant, an electrochemical reaction causing corrosion of the material will occur between the material and the cooling water. For example, if it is aluminum, corrosion may occur even with chloride ions and copper ions contained in water. Therefore, it is suitable to use pure water managed by the ion exchange unit and antifreeze solution with rust inhibitor.

Joint Methods of Liquid Cold Plate's Production Process

Tube-in-Plate Type

It is a cold plate that embeds a cooling tube in the base material. Apply pressure to the pipe into the flow channel of the base material and insert it into the flow channel of the base material. It is difficult to create a complex flow channel because it is necessary to process pipes according to the flow channel. In addition, the pipe may not be able to follow the bending part of the flow channel, and there is a possibility that there will be a gap between the pipe and the base material, and the cooling performance may be reduced locally.


Brazing is a method melting the adhesive called "brazing filler material" between the parts you want to join by heat and then fixing it with cooling. Unlike welding, the base material is not melted. There are several types of brazing fillers, and the one whose main component is silver is "silver brazing".
Brazing is possible both in the atmosphere and in vacuum, especially brazing in vacuum is possible to join with high airtightness, and there are many working examples in the cold plates. On the other hand, the heating of the brazing filler material and the heat treatment of the base material itself also occur, so there is a concern about the decrease in the strength of the base material due to the thermal effects.

FSW(Friction Stir Welding)

FSW stands for Friction Stir Welding in English. Friction Stir Welding is a method of connecting pressing parts materials with strong force while rotating cylindrical tools with protrusions at the tip. The protrusions of the tool are applied to the joint point between the joining parts materials and the main material is softened by the rotating friction heat, and at the same time, the surrounding area is plasticized by the rotation of the tool, and the components are integrated. It can be used in the atmosphere in general. The heat influence of the joining part can be minimized, and the generation of noise and dust can be reduced.