|
Not only does Polara offer higher performance at reduced cost but it also competes
effectively on the basis of enabling solutions that are lighter, smaller, and quieter.
How Polara Works
Polara achieves its excellent performance due to its novel use of active heat pumping.
This pumping is accomplished using Peltier-Assisted Conduction, an innovative and unique
implementation of the Peltier effect. Polara is not like traditional thermoelectric
devices and does not share their drawbacks and inefficiencies.
A thermoelectric (TE) device or TE Chip (TEC) uses electricity to transfer ("pump")
heat energy from one location to another. It uses a direct current flowing through a
circuit comprised of dissimilar conductors or semiconductors, causing absorption of
heat energy at one junction and liberation of the absorbed energy at another.
Composed primarily of semiconductors, TECs are highly reliable, modular, silent and
non-polluting. Such devices are designed for sub-ambient (refrigerating) cooling and
use semiconductors of low thermal conductivity to insulate the area being cooled from
backstreaming heat flow. This backstreaming, represented by the last term of the heat
removal equation below, is the key contributor to the low Coefficient Of Performance
(COP) of conventional TECs.
TECs also transfer the heat in one direction only, straight away from the area to be
cooled (the Z-direction) and consequently offer no heat spreading capability.
Polara is entirely different in two key respects:
First, thermocouples can be oriented arbitrarily, allowing heat pumping in the XY-plane
and not just in the Z-direction. Polara’s unique architecture actively spreads heat in
all three planes. This allows Polara to be a heat spreader, not just a heat pump. The
thermocouples can also be placed with great flexibility, allowing the location of heat
rejecting and heat absorbing junctions to be sited for maximum performance and
efficiency.
Second, Polara is designed for ambient operation, allowing the use of semiconductors
of high thermal conductivity. There is no need to have insulating materials because
heat is pumped in the same direction as it is naturally conducted; the use of thermally
conductive materials in Polara adds to its performance. The heat removal equation for
Polara thus differs from conventional TECs by the sign of the last term:
Polara pumps heat down the thermal gradient; there is no backstreaming of heat.
Consequently, Polara enjoys a COP an order of magnitude higher than conventional TECs.
Hot Spots
Intel’s Steve Pawlowski described hot spots, localized die areas of greater heat flux
density, as the thermal problem “you really need to worry about.” Recent decisions
and announcements on chip architecture roadmaps by Intel and others show that this
problem is starting to retard flexibility in chip design. If chips can be designed
or cooled to have an even heat flux distribution, i.e. to be isothermal, then the
remainder of the cooling solution will operate more efficiently. This in turn allows
the desired reductions in size, weight and cost of those solutions.
Thermal map of die showing hot spots (red) and cooler regions (blue)
The active heat pumping of Polara solves this problem. While traditional spreader
materials conduct heat the same in every direction, i.e. are isotropic, Polara uses
Smart Spreading™ to conduct more heat where the need is greatest. Polara is the industry's
only true anisotropic heat spreader.
Polara Smart Spreading with Thermal Raceways™ graphically depicted
Smart Spreading allows die-level customization of the solution. It works by architecting the
placement and orientation of the thermocouples within the spreader to create Thermal Raceways,
pathways of vectorized active heat transport. The Peltier-Assisted Conduction of these Thermal
Raceways actively pumps heat from hotter to cooler regions. The result is both highly efficient
and has such incredibly high effective thermal conductivity that Polara provides hot spot
temperature reductions previously possibly only with costly diamond composites.
Polara Smart Spreading. Heat is absorbed at the hot spots and transported to the cooler edges
Polara’s adjustable thermal properties can be applied to Multi Chip Modules where a variety
of chips create varying hot spots as depicted on side A. Levels of heat transfer can now be
tailored above each chip to create an isothermal condition (side B) or preferential heating/cooling
of any number of components within the module.
Properties
No other cooling technology available today offers Polara’s unique combination of
features and benefits, or enjoys its powerful combination of advantages over other materials.
There are many kinds of heat spreader technologies and materials
available today. There are five key criteria in the selection of a heat spreader technology:
performance, CTE, cost, density of the material, and anisotropy. Optimizing the overall
solution can be a significant challenge because most approaches before Polara involved
compromising one or more of these criteria.
Polara's key properties include:
- Performance
- Higher thermal conductivities with performance exceeding bonded copper.
- Higher thermal performance than Aluminum/Silicon/Carbon (AlSiC) composite: fills the
performance gap between AlSiC and carbon fiber composites at a fraction of the cost.
- Thermoelectric junctions in multiple planes spread heat more quickly and efficiently.
- Adjustable thermal performance for a variety of heat loads. Polara power input can be
varied, adjusting the thermal conduction, to fit the application or mode of operation.
- CTE (Coefficient of Thermal Expansion)
- CTE compatibility with Silicon and Gallium Arsenide (GaAs) chips, eliminating
mechanical stress and extending reliability.
- Equivalent to the CTE matching ability of Copper-Molybdenum (Cu-Mo) and Copper-Tungsten
(Cu-W) alloys at a fraction of the cost.
- CTE matching permits thermally conductive direct eutectic bonding to the die. Non-CTE
matching spreader technologies cannot be eutectically bonded, but must instead use
thermally resistive die attach materials.
-
Cost
- Depending on application specifics and production volumes, Polara can cost as little as
$1 per square inch, less than 1/3 the cost of AlSiC, and 1/6 the cost of Cu-Mo and Cu-W composite spreaders.
With its increased performance additional solutions savings can be readily achieved in
other components, notably the heat sink and fan.
-
Density
- Up to 65% lower weight, about the same as aluminum.
- High strength and stiffness.
- Anisotropy
- Anisotropic (directional) heat transfer for maximum efficiency.
Effective thermal conductivity from hot spots equivalent to diamond
composites.
Customers of Polara can also take advantage of its ample design flexibility,
operational characteristics, and manufacturing advantages:
- Up to 25% smaller size.
- Nearly any geometry possible allows design simplification.
- Completely scalable to adapt to any size application.
- Flexible packaging solutions.
- Low Temperature Coefficient of Resistivity (TCR): Polara can also be utilized as
a stable low-value (droop) resistor.
- Electrical isolation, grounding and EMI shielding readily accommodated.
- Can be integrated with conventional TEC technology to achieve high thermal performance
for small form-factor sources requiring Peltier stability or sub-ambient operation.
- Silent, maintenance free, and non-polluting operation.
- Eutectic/Wafer bonding: Polara™ can be bonded to CMOS wafer during wafer fab or
post-singulation, can be integrated with the backside of a die, or used with SOI wafers.
- Looks, feels and handles about the same as a silicon die on the packaging line.
- Readily accommodates dielectric layers (SiO2, SiN) on any face.
- Provides structural, thermal basis for cavity-down wire bonded BGA packages.
- Fast fab set-up using a combination of well-established industry processes.
Availability & Information
Want more information?
| 
Enerdyne Solutions Polara™ heat spreader is a revolutionary advance in ambient
cooling. A new kind of heat spreader, it offers significant performance advantages
because it uses two methods of heat transfer: passive thermal conduction, and active
heat pumping. This dual mechanism yields performance higher than all other technologies
except costly carbon fiber and diamond composites. Polara serves both general electronics
cooling needs and the more specific problem of hot spot mitigation.
