HOW TO DESIGN AND OPERATE VAPOR CHAMBER RADIATOR?

VC (vapor chambers) literal translation is called steam chamber, the industry is generally called flat heat pipe, vapor chamber, soaking plate. With the continuous improvement of chip power density, VC has been widely used in the heat dissipation of CPU, NP, ASIC and other high-power devices. This paper introduces the main problems in VC design.

1. VC radiator is better than heat pipe or metal base plate radiator

Although VC can be considered as flat heat pipe, it still has some core advantages. It is better than metal or heat pipe. Can make the surface temperature more uniform (less hot spots). Secondly, the VC radiator can make the heat source and the equipment contact directly, so as to reduce the thermal resistance; the heat pipe usually needs to be embedded in the substrate.

                                                                                                              Comparison of VC with heat pipe and metal

2. Use VC to equalize temperature instead of transferring heat like a heat pipe

Heat pipe is an ideal choice to connect heat source to the far end fin, especially for the relatively zigzag path. Even if the path is straight, more heat pipes are used instead of VC for heat transfer. This is the key difference between heat pipe and VC. Heat pipe focuses on heat transfer.

VC diffusion heat, heat pipe transfer heat

Of course, there are exceptions. When the cost is first, the two heat sources are close and the temperature is required to be uniform, the use of heat pipe is also an option.

3. Use VC when thermal budget is nervous

The maximum ambient temperature of the product minus the maximum temperature of die is called thermal budget, which is higher than 40 ℃ for many outdoor applications.

The sum of all △ - TS must be less than the thermal budget

4. The VC area shall be at least 10 times the area of the heat source

Like the heat pipe, the thermal conductivity of VC increases with the increase of its length. This means that VC with the same size as heat source has little advantage over copper substrate. One experience is that the area of VC should be equal to or greater than ten times the area of heat source. In case of large thermal budget or large air volume, this may not be a problem. However, in general, the basic bottom surface needs to be much larger than the heat source.

VC shall be at least 10 times the size of the heat source

5. Choose VC form according to application requirements

You should be familiar with the traditional VC. It is made of two stamping metals (two-piece design), which can be made into any shape to meet the needs.

Advantages and disadvantages of two-piece design

Now, some manufacturers are also producing integrated VC, which is similar to a big clearance. Its shape is limited to rectangle, but it can be bent in Z direction to form U-shaped or stepped type.

Advantages and disadvantages of overall design

6. Other considerations

Size - there is no theoretical limit, but VC used for cooling electronic equipment rarely exceeds 300-400 mm in X and Y directions. Thickness is a function of capillary structure and dissipation power. Sintered metal core is the most common type, VC thickness is between 2.5-4.0mm.

Power density - the ideal application of VC is that the power density of the heat source is more than 20 W / cm 2, but in practice, many equipment is more than 300 W / cm2.

Protection - the coating most commonly used for heat pipes and VC is nickel plating, which has the function of corrosion prevention and beauty.

Operating temperature - although VC can withstand multiple freeze / thaw cycles, their typical operating temperature range is 1-100 ℃.

Pressure - VC is usually designed to withstand a pressure of 60 psi before deformation. However, up to 90 psi.