Vapor Chamber Design Guide Datasheet by Wakefield-Vette

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Vapor Chamber Design Guide
Vapor Chambers are used to transport heat over a distance with
very low thermal resistance. This is very helpful when small heat
sources need to be dissipated over a larger area. Vapor chambers
are a Fluid Phase Change application because they use a closed
loop to transfer heat quickly through evaporation and
condensation within the chamber. The particular aspect useful in
designs is that vapor chambers transport heat in a plane, more
effectively “spreading heat” compared to a heat pipe which
transports heat over a distance in a straight line.
Vapor chambers, like heat pipes, do not actually dissipate the
heat to the environment, but serve to move heat efficiently within
a thermal system. A vapor chamber is made from copper plates
(top and bottom) with an internal wick structure that is sealed
around the perimeter with a small amount of water inside. As
heat is applied to the chamber, the water will boil and turn to a
gas, which then travels to the colder section of the vapor
chamber, where heat is dissipated through an external heat
exchanger, where it condenses back to a liquid. It is the
evaporating and condensing of the water that form a pumping
action to move the water (and thus the heat) from the area of the
heat source to all other areas of the vapor chamber.
There are a few types of wick structure that can be used
within the vapor chamber, but most commercial chambers
are classified as mesh or powder. In both cases, the
powder or mess line the copper plate surfaces to allow
water flow to/from all directions within the area of the
vapor chamber. Often, when mesh is used as the wick
structure, different sized meshes are used together to
promote condensation or transport of liquid depending on
the void size. Vapor chambers are best used in horizontal
orientations. The effects of gravity may vary depending on
application and orientation, but one must consider lower
performance if used above 15°out of horizontal.
During the manufacturing process copper
columns are used throughout the vapor
chamber to support the plates that act as the
lids and contain the liquid and vapor. The
copper mesh is oriented within the chamber
pressed against the copper plates. The plates
are sealed around the perimeter via diffusion
bonding. In some cases, soldering or
welding are used, but diffusion bonding
allows for the strongest and highest
temperature compatible seal for the vapor
chamber. The diffusion bonding process
also allows the mesh to bond to the copper
plates as well.
Vapor Chamber Introduction
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Vapor Chamber Design Guide
Many thermal systems benefit from the addition of vapor chambers, especially when heat sources are dense
and the final heat exchanger is much larger and the heat from the source must be spread to a larger area
effectively to efficiently use the heat exchanger. Computer applications, such as processors, graphics cards
and other chip-sets, have high thermally dissipated power in a small area. Fan heat sink combinations used
in these applications can offer high-performance dissipation to the ambient, but much of the battle is to
spread the heat to the heat exchanger with as little temperature change as possible. Vapor chambers excel
at this and can transport large heat loads from small areas with very little temperature difference.
Why Use Vapor Chambers?
Key Features
Material: Copper
Wick Structure: Copper Mesh
Light Weight
Versatile with high thermal performance
Vapor chambers are used in many harsh environments such as:
Computers and Datacenters
Vapor chambers have proven to be robust and reliable over
many years in these types of applications. The next section will
give more technical detail on the performance of vapor
chambers depending on thickness and area.
How Vapor Chambers Operate
Heat Source
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Vapor Chamber Design Guide
Vapor Chamber Basics
Vapor Chamber Basics
Comparison to Heat Pipes
General parameters
In many applications, the decision to use a vapor chamber is frequently compared to a thermal solution using
heat pipes. In both cases, 2-phase transport is used as a vapor moves heat within the chamber or pipe and the
liquid is condensed at the heat exchanger and transported back to the heat source. However, the main aspects
of applications that differentiate vapor chambers from heat pipes are:
High power density: when the heat source is small but heat generation is large, vapor chambers can more
easily transport the heat to a larger area. A heat pipe solution would require multiple pipes, which may be
difficult to integrate within the footprint of the heat source.
High power: when the application must dissipate large wattage, a vapor chamber spreads the heat to a large
area efficiently with similar temperatures of the chamber surface. This allows more efficient use of the final
heat exchanger since hot spots are minimized. Heat pipes can also spread the heat, but unless many are
ganged together, the hot spots may still persist.
When considering the use of a vapor chamber in your
application, it is important to consider the orientation
with respect to gravity and overall heat load for the
thermal system. The transport of vapor within the vapor
chamber is responsible for the thermal conduction from
one area to the other. A thicker vapor chamber can
transport more vapor, translating into a larger heat
carrying capacity. Although vapor chambers can have
complex shapes and mounting features, they are not
typically bent and integration can be more direct with
the heat source than with heat pipes.
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Vapor Chamber Design Guide
Much like heat pipes, the ultimate dimension in determining
heat carrying capacity of a vapor chamber is the volume of
the vapor space. This is determined by the thickness and area
of the vapor chamber. For most applications, the thickness of
the vapor chamber does not exceed 3mm, however pedestals
and other surface features can be used to contact specific heat
sources while leaving clearance for other board mounted
objects. These pedestals can be extended 5mm from the
vapor chamber lid plate. Mounting holes can also be
integrated within the area of the vapor chamber for better
integration with the heat source and locating the heat source
a the center of the vapor chamber with good pressure
Vapor Chamber Thermal Capacity
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Vapor Chamber Design Guide
Interfacing vapor chambers with plates and heat exchangers is
predominately about maximizing contact area. In most cases, the
vapor chambers are soldered to heat exchanger fins for air cooled
applications. The vapor chambers can also be soldered to liquid cold
plates to take advantage of spreading the heat before final heat
exchange with the liquid. In many cases, the vapor chambers are
also integrated with heat pipes to take the heat that has spread in the
plane of the vapor chamber and extend it in the vertical dimension
to more efficiency interact with cooling fins. Integrating with the
heat source is most commonly done with pressure, up to 90 psi, and
the use of a thermal grease or other interface material to maximize
surface area contact to the source.
Vapor Chamber Assemblies
2 types of filling ports (7mm maximum):
Retracted Chamfer
u Wakefield-vette V—C'106'70' 3 Product Info Description Dimension(mm) , L: lOGmm/W : 70mm/T: 3mm Operation Power : 150W" Product Info Details -Therma| Resistance : 0.150°C/W '0peration Temp. : 4ON140°C -P|atform 2 Intel 2011 Narrow
Vapor Chamber Design Guide
Wakefield-Vette offers individual vapor chambers through distribution. These most common
offerings are a great option for testing, sampling, and validating your vapor chamber solution into
eventual production.
When building or testing your heat sink assembly please feel free to contact one of Wakefield Vette’s
authorized distributors to purchase. Always remember to contact us for free consultation on assembly
design or parameter questions.
Wakefield Vette Standard Vapor Chambers
WKV Part # Product Description
Resistance length width thickness qMax
Standard Vapor Chamber 113.1mm x 81.75mm X 5.17mm
0.145 113.1 81.75 5.7 180W~
VC-90-90-3 Standard Vapor Chamber 90mm x 90mm x 3.00mm 0.143 90 90 3 150W~
VC-106-70-3 Standard Vapor Chamber 106mm x70mm x 3mm 0.150 106 70 3 150W~
VC-106-82-3 Standard Vapor Chamber 106mm x 82mm x 3mm 0.140 106 82 3 150W~
VC-1131-8175-517 Product Info Description
Dimension(mm)L113mm / W81.8mm / T5.7mm
Operation Power180W~
Product Info Details
Thermal Resistance0.145/W
Operation Temp.40~130
VC-90-90-3 Product Info Description
Dimension(mm)L90mm / W90mm / T3mm
Operation Power150W~
Product Info Details
Thermal Resistance0.143/W
Operation Temp.40~140
PlatformIntel 2011 Square
Product Info Description
Dimension(mm)L106mm / W82mm / T3mm
Operation Power150W~
Product Info Details
Thermal Resistance0.140/W
Operation Temp.40~140
PlatformIntel 2011 Narrow

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