A concentrated high heat flux source is attached to one surface of the vapor chamber. The heat input vaporizes the working fluid. The vapor spreads to the entire inner volume and condenses over a much larger, cooler surface of the vapor chamber. The condensed liquid is transported back to the heat input area in the wick structure lining the vapor chamber inner wall. In some cases, the vapor chamber is referred to as a “heat flux transformer” because of its ability to convert higher heat fluxes into lower heat fluxes.
The photo above shows the internal structure of a typical copper/water vapor chamber. Arrays of internal posts provide structural support to accommodate the pressure difference across the vapor chamber envelope. A thin layer of wick lines the inner wall of the vapor chamber.
The photo below shows a completed vapor chamber heat pipe with an external structural frame.
Vapor chambers may be used to cool a single microprocessor or multiple processors in a single plane. The vapor chamber can accept heat from each source and transfer the heat to an integral air-cooled heat sink or water cooled edge rails.
The photo shows the components in an integral vapor chamber-heat sink assembly. The vapor chamber is bonded to the base of the heat sink. It accepts concentrated heat inputs and transfers the heat uniformly over the entire heat sink base. An isothermal heat sink base eliminates the temperature gradients due to conduction and improves the fin efficiency of the heat sink.
It should be noted that the effective thermal conductivity of a vapor chamber is dependent on the ratio of the heat removal area to the heat input area. This ratio is sometimes referred to as the area aspect ratio. The effective thermal conductivity of the vapor chamber increases with the area aspect ratio. Typical effective thermal conductivities range from 5,000 to 200,000W/m-K. The table below summarizes ACT’s vapor chamber product specifications.
|Planar dimensions||Scalable to 10″ x 20″|
|Thickness||0.125″ to 0.200″|
|Heat Flux||> 100 W/cm2|
|Thermal Resistance||< 0.08°C/W|