United States Patent (19)
`Batchelder
`
`USOO6O19165A
`Patent Number:
`11
`(45) Date of Patent:
`
`6,019,165
`Feb. 1, 2000
`
`54) HEAT EXCHANGEAPPARATUS
`
`76 Inventor: John Samuel Batchelder, 2 Campbell
`Dr. Somers, N.Y. 10589
`s
`s
`21 Appl. No.: 09/080,915
`22 Filed:
`May 18, 1998
`(51) Int. Cl. ................................................... F28F 700
`52 U.S. Cl. ....................... 1651803; 165/804; 165,805.
`165/104.33; 257/714; 317/234 R
`58 Field of Search .................................. 165/80.3, 80.4,
`165/80.5, 104.33; 257/714; 317/234 R
`References Cited
`
`56)
`
`U.S. PATENT DOCUMENTS
`1819,528 8/1931 Terry
`3,654,528 4/1972 Barkan. 317,234 R
`4.519.447 5/1985 Wiech ...
`... 165/104.33
`4,780,062 10/1988 Yamada.
`... 417/322
`5,001,548 3/1991 Iversen ......
`... 165/80.3
`5,183,104 2/1993 Novotny ............................. 165/104.33
`
`5,203,399 4/1993 Koizumi ............................. 165/104.33
`5,316,077 5/1994 Reichard .
`... 165/104.28
`5,394.936 3/1995 Budelman
`165/104.33
`5,731,954 3/1998 Cheon ..................................... 361/699
`5,763,951
`6/1998 Hamilton et al. ....................... 257/714
`FOREIGN PATENT DOCUMENTS
`4225676 2/1994 Germany.
`Primary Examiner-ra S. Lazarus
`Assistant Examiner Terrell McKinnon
`57
`ABSTRACT
`
`An apparatus to transfer heat from a heat Source to a heat
`absorber, the apparatus consisting of an active thermal
`Spreader plate with internal flow channels, a recirculating
`heat transfer fluid, and a means to impel the heat transfer
`fluid using an external moving magnetic field. In the most
`preferred embodiment a centripetal pump impeller is trapped
`inside the active thermal spreader plate, and the impeller is
`motivated to rotate due to eddy currents generated by the
`external moving magnetic fields.
`
`35 Claims, 13 Drawing Sheets
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`1
`HEAT EXCHANGEAPPARATUS
`
`6,019,165
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`BACKGROUND OF THE INVENTION
`In 1981 Carver Mead pointed out that a computer is a
`thermodynamic engine that Sucks entropy out of data, turns
`that entropy into heat, and dumps the heat into the room.
`Today our ability to get that waste heat out of Semiconductor
`circuits and into the room at a reasonable cost limits the
`density and clock Speed of those circuits.
`Cooling technologies are available that can transport very
`high densities of waste heat For example the combined
`fluorocarbon and helium forced convection design described
`in U.S. Pat. No. 5,131,233 achieves a volumetric power
`transfer density which is much greater than what is expected
`for WorkStation microprocessors even through the year
`2010. However, due to the complexity of this system, the
`cost to implement this System is orders of magnitude above
`the S5 per microprocessor targeted by Intel and the PC
`manufacturers.
`A typical characteristic of heat transfer devices for elec
`tronics today is that the atmosphere is the final heat Sink of
`choice. Air cooling gives manufactures access to the broad
`est market of applications. Another typical characteristic of
`heat transfer devices for electronics today is that the Semi
`conductor chip thermally contacts a passive aluminum
`Spreader plate, which conducts the heat from the chip to one
`of Several types of fins, these fins convect heat to the
`atmosphere with natural or forced convection.
`AS the power to be dissipated by Semiconductor devices
`increases with time, a problem arises: within about ten years
`the thermal conductivity of the available materials becomes
`too low to conduct the heat from the Semiconductor device
`to the fins with an acceptably low temperature drop. The
`thermal power density emerging from the chip will be So
`high in ten years than even copper or Silver spreader plates
`will not be adequate. A clear and desirable Solution to this
`problem is to develop inexpensive ways to manufacture
`more exotic materials like pyrolitic graphite or diamond that
`have even higher thermal conductivities. If the cost of these
`exotic materials does not fall quickly enough, an alternative
`Solution is needed, Such as will be discussed shortly.
`Heat can be transported by an intermediate loop of
`recirculating fluid; heat from the hot object is conducted into
`a heat transfer fluid, the fluid is pumped by Some means to
`a different location, and there the heat is conducted out of the
`fluid into a fin means and finally into the atmosphere.
`Thermosiphons use a change in density of the heat transfer
`fluid to impel circulation of the fluid, while heat pipes and
`boiling fluorocarbon use a phase transition of the heat
`transfer fluid to impel circulation of the fluid. While these
`approaches have important cooling applications, their cost
`for implementation will have to be reduced to generally
`impact Semiconductor cooling. It is our Suspicion that
`extracting the power for moving the heat transfer fluid from
`the heat flow itself is not energetically warranted in Systems
`which dissipate hundreds of watts of waste heat from a
`Semiconductor chip, and which dissipate Several watts of
`electrical power by the fan circulating atmosphere through
`the fins.
`Many heat transfer Systems use an external Source of
`energy to pump a recirculating heat transfer fluid. Most of
`these do not incorporate the pumped heat transfer fluid in an
`active spreader plate geometry that can be implemented as
`a replacement for a passive spreader plate. Most of these
`incur the cost disadvantage of requiring Separate motors to
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`impel the heat transfer fluid and to impel the atmosphere.
`Most of these incur the reliability disadvantage of using
`Sealed shaft feed-throughs to deliver mechanical power to
`the heat transfer liquid. Most incur the added assembly cost
`and reliability exposure associated with hoses and fittings.
`None of these existing heat transfer Systems simultaneously
`use a Single motor to drive an impeller for the heat transfer
`fluid and an impeller for the atmosphere, use moving exter
`nal magnetic fields to eliminate a rotary Seal, and use
`monolithic assembly without hoses or fittings.
`U.S. Pat. No. 1,819,528 describes a refrigerator. A motor
`Sealed in the Freon reservoir compresses and circulates
`Freon through external plumbing coils, while Simulta
`neously driving an atmosphere cooling fan using an eddy
`current based magnetic coupling. The internally generated
`moving magnetic fields cause the atmosphere moving fan to
`rotate more slowly that the Freon compressing impeller.
`U.S. Pat. No. 4,519,447 describes an active spreader
`plate. The heat transfer fluid in the plate is impelled by
`magnetohydrodynamic pumping, which uses Stationary
`magnetic fields plus large electric currents passing through
`the heat transfer fluid, as opposed to moving magnetic fields
`alone.
`U.S. Pat. No. 5,183,104 describes a closed cycle expan
`Sion valve impingement cooling System for Semiconductor
`chips. It utilizes hoses and fittings, and does not use moving
`external magnetic field to impel the heat transfer fluid.
`U.S. Pat. No. 5,316,077 describes an active spreader
`plate. The heat transfer fluid in the active spreader plate is
`impelled by an impeller embedded in the active spreader
`plate that is driven by a Sealed Shaft passing through the
`plate.
`U.S. Pat. No. 5,731,954 describes an electronics cooling
`system. The heat transfer fluid is impelled by an external
`pump, and the fluid circulates through discrete heat
`eXchange elements through hoses and couplings.
`
`SUMMARY OF THE INVENTION
`The primary objective of this invention is to provide a low
`cost high reliability heat eXchange apparatus that incorpo
`rates a composite Substrate containing flow channels and a
`heat transfer fluid, providing low thermal resistance cooling
`to high density heat Sources.
`A further objective of this invention is to provide a design
`for cooling electronic components that is compatible with
`the geometry and manufacturing tooling associated with the
`passive spreader plate heat SinkS currently in general use.
`A further objective of this invention is to provide an active
`Spreader plate with no moving or rotary mechanical Seals.
`A further objective of this invention is to provide a heat
`Sink design for electronic components that uses a Single
`motor to impel atmospheric motion and the motion of an
`additional heat transfer fluid.
`A further objective of this invention is to provide an active
`Spreader plate without hoses or fluid couplings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 shows an example from the prior art of a heat
`eXchange device with a heat Source, a spreader plate, a fin
`array, and an atmospheric mover.
`FIG. 2 shows a croSS Section of the current invention,
`including a composite Substrate, an external impeller, an
`external motor, and an impeller internal to the composite
`Substrate that is magnetically coupled to the external motor.
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`FIG. 3 shows coplanar first and second surfaces of the
`composite Substrate.
`FIG. 4 shows a composite substrate where the normals to
`the heat transfer Surfaces are perpendicular, where the com
`posite Substrate is cooling a laser bar array.
`FIG. 5 shows two composite substrates attached to a
`common fin array.
`FIG. 6 shows various fin means.
`FIG. 7 shows the construction of a composite substrate
`with a plurality of interior channels, the heat producing
`component attached to the outside of the composite
`Substrate, the heat producing component thermally contact
`ing a fin means in the interior of the composite Substrate.
`FIG. 8 shows the thermal fluid flow pattern in the com
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`posite substrate of FIG. 7.
`FIG. 9 shows various impeller designs, including a cen
`trifugal pump, a displacement pump, a Viscosity pump, and
`a flexure pump.
`FIG. 10 shows eddy current and permanent magnet
`designs for magnetically coupling an impeller interior to the
`active spreader to plate to a motor exterior to the active
`Spreader plate.
`FIG. 11 shows a gas filled bladder in the interior of the
`composite Substrate.
`FIG. 12 shows a deformable Surface element of the
`composite Substrate.
`FIG. 13 Shows a heat producing component mounted
`inside of the composite Substrate.
`FIG. 14 shows a composite Substrate containing two
`flexure impellers.
`DETAILED DESCRIPTION
`The heat absorber used in this apparatus will typically
`facilitate transfer of heat to a Surrounding fluid. For clarity,
`in the remainder of the specification we will refer to the
`Surrounding fluid as atmosphere, however it can also be
`water, Freon, glycol, Steam, or any other thermal transfer
`fluid. The heat absorber will typically therefore be a fin
`means to provide good thermal contact to the Surrounding
`fluid. In a less preferred embodiment the heat absorber can
`contain a material undergoing a phase transition, So that the
`heat absorber by itself can be an isothermal sink for heat.
`A simplified limiting case helps to identify applications
`that need an active Spreader plate instead of a passive
`spreader plate. Suppose that a heat Source with an area A
`needs to be attached to a heat Sink with a thermal resistance
`R. We idealize the problem by allowing the heat source to
`be a hemisphere, and by allowing the Spreader plate to be a
`large hemispherical shell. This idealized three dimensional
`radial heat flow minimizes the temperature drop within the
`Spreader plate. If we say that the spreader plate can contrib
`ute at most a thermal resistance of Re/2, we can Solve for the
`minimum allowable thermal conductivity of the spreader
`plate material:
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`tivity is then calculated by the above equation to be 533
`wattst( C. meter). Since pure aluminum has a thermal
`conductivity of 202 watts/( C. meter), pure copper has a
`thermal conductivity of 385 watts/( C. meter), and even
`silver (the metal with the highest thermal conductivity) is
`410 watts/( C. meter), no metals are available as passive
`thermal spreaders for this application, even under ideal
`conditions.
`We define a composite substrate to be a rigid assembly of
`at least two pattemed objects that hermetically enclose one
`or more interior channels or passageways. The most pre
`ferred embodiment of the composite Substrate is an ultra
`Sonically welded assembly of Several injection molded plas
`tic shells. Another less preferred embodiment is for the
`composite Substrate to be composed of Several formed metal
`plates that are welded or Soldered together. Another leSS
`preferred embodiment is for the composite substrate to be
`composed of Several Stamped plastic and metal plates that
`are bonded together with adhesives.
`The most preferred application of a composite Substrate
`for transferring heat from a heat generating object to a heat
`absorbing object is as an active thermal spreader plate for
`electronic heat Sink applications. Other preferred applica
`tions include thermal processing heat eXchangers, tempera
`ture control of isolated chambers, and thermal equalization
`of Surfaces. For clarity and without a loSS of generality, we
`will refer to the composite Substrate as an active spreader
`plate in the remainder of the Specification.
`To illustrate the intent and implementation of the
`invention, FIG. 1 shows and example of a prior art heat
`transfer device. The heat Source (2) comprises a semicon
`ductor chip (4) cemented (6) to a metal cover (8). The cover
`(8) is hermetically sealed to a chip carrier (10), which acts
`as a carrier for the electrical contacts (12) between the chip
`and the next level of electronic packaging. A compliant
`thermal conductor and electrical insulator (14) conducts heat
`from the heat Source (2) to a passive spreader plate (20).
`Heat enters the passive spreader plate on its lower Surface
`(24) and is conducted through the bulk of the passive
`spreader plate (22) to the periphery of the top Surface (26),
`where it is conducted out of the passive spreader plate into
`heat absorbing devices (28). The passive spreader plate is
`typically aluminum owing to aluminum's good thermal
`conductivity, low cost, and low weight. Other materials used
`for the spreader plate are Steel, copper, pyrolytic graphite
`composite, and diamond, in order of increasing performance
`and increasing cost The heat flow lines (42) radiate from the
`heat Source (2) through the passive spreader plate (20) to the
`heat absorber (28). The heat absorber (28) consists of a
`material permeable to fluid flow and capable of conducting
`heat away from the passive spreader plate (20); examples of
`Various heat absorber designs will be Subsequently
`described. A fan housing (30) Supports a motor and rotor
`(32), and blades (34) are attached to the motor and rotor
`(32). Atmosphere is impelled to flow (40) through the fan
`and through the heat absorbing devices (28), So that heat is
`transferred to the air and exhausted into the environment.
`Other orientations of the atmosphere flow are operable,
`however this impinging flow is generally the most Success
`ful because by directing the flow towards the base of the heat
`absorber, the thermal efficiency of the heat absorber is
`typically increased.
`In FIG. 2 we show an embodiment of the invention as an
`evolution of the prior art design of FIG. 1. The heat source
`(2) comprises previously described elements. A compliant
`thermal conductor and electrical insulator (14) conducts heat
`from the heat source (2) to the active spreader plate (20).
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`kspreader =
`Ra VA,
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`For example, the Intel road map for microprocessor cooling
`for the year 2006 calls for 200 watts to be dissipated at a
`junction temperature of 95 C. into ambient atmosphere at
`45 C. from a 15mmx15 mm chip. From these specifications
`we have that Re=0.25 C./watt and that A=2.25 square
`centimeters. The minimum spreader plate thermal conduc
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`Heat enters the active spreader plate (20) on its lower surface
`(24), and is conducted into a metallic fin array (52). Instead
`of the heat primarily being conducted by the solid bulk
`material of the active spreader plate (22), it is transfer from
`the fin array (52) into a heat transfer fluid sealed in flow
`channels (50) inside the active spreader plate (20). The heat
`transfer fluid is impelled to flow by a mechanism described
`later, So that the heat transfer fluid releases heat near the
`periphery of the top Surface (26), where the heat is con
`ducted out of the active spreader plate into heat absorbing
`devices (28). A fan housing (30) supports a motor and rotor
`(32), and blades (34) are attached to the motor and rotor
`(32). Atmosphere is impelled to flow (40) through the fan
`and through the heat absorbing devices (28), So that heat is
`transferred to the atmosphere and exhausted into the envi
`ronment. The rotor (32) has an extended cylindrical Support
`for a permanent magnet (56), So that the magnet is main
`tained a small distance above the surface (26) of the active
`spreader plate, and So that the magnet (56) is rotated with the
`fan blades (34). The configuration and composition of the
`magnet will be Subsequently described. A rotatable impeller
`(54) inside the active spreader plate and immersed in the
`heat transfer fluid is motivated to rotate by the moving
`magnetic fields emanating from the magnet, which in turn
`impels the heat transfer fluid to circulate through the flow
`channels (50). In the most preferred embodiment the impel
`ler (54) is a centripetal or centrifugal pump that impels the
`heat transfer fluid to circulate as indicated (60); the heat
`transfer fluid flows radially outwards from the impeller (54),
`then in proximity to the heat absorbing devices (28), then
`back towards the fin array (52), and finally up again to the
`impeller (54). The composition of the heat transfer fluid is
`preferably a low Viscosity high heat capacity material Such
`as mixtures of water with alcohols or ethylene glycol. In the
`absence of the internal fin array (52) a preferred embodiment
`uses a low melt metal alloy as the heat transfer fluid, Such
`as the 58 C. eutectic containing gallium.
`The component parts of the active spreader plate will
`preferably be assembled initially without the heat transfer
`fluid filling the flow channels. There are several ways to fill
`the flow channels with heat transfer fluid and to Subse
`quently Seal the assembly that are well known to those
`skilled in the art. A preferred technique is to provide one or
`more access holes in the initial assembly which allow both
`the heat transfer fluid to be injected and the atmosphere
`inside the initial assembly to be remove; the access holes are
`then Sealed with adhesive, plugs, or heat Seals. An alterna
`tive preferred technique is to Seal the initial assembly with
`one or more rubber Septums, a hypodermic Syringe can then
`inject the heat transfer fluid through the septum into the flow
`channels after initial assembly. In FIG. 13 we describe
`another less preferred embodiment, in which Sub-assemblies
`of the active spreader plate are Screwed together with
`elastomeric Seals, in this case the final assembly can be done
`with the Sub-assemblies immersed in the heat transfer fluid.
`In FIG. 2 a tubaxial fan impels the atmosphere to flow in
`contact with the fin means. Other types of impellers known
`to those skilled in the art can also be used, Such as blowers
`and laminar flow fans.
`FIG. 3 shows an alternative preferred embodiment of an
`active spreader plate designed to transfer heat from one or
`more heat Sources on one side of the active spreader plate to
`a heat absorbing device also on the Same side of the active
`Spreader plate. This embodiment of the active spreader plate
`is shown laminated to the back Side of a printed circuit board
`on which there are Several heat dissipating components.
`Several heat Sources (2) generate heat, which is transferred
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`through a printed circuit board (66) and through the Surface
`(24) of the active spreader plate (20) into a heat transfer fluid
`sealed in flow channels (50) and (64). The circuit board can
`contain thermal Vias to improve the thermal conductivity of
`the circuit board (66). A fan housing (30) supports a motor
`and rotor (32), and blades (34) are attached to the motor and
`rotor (32). Atmosphere is impelled to flow (40) through the
`fan, through slots (62) in the active spreader plate (20), and
`through the heat absorbing devices (28), so that heat is
`transferred to the atmosphere and exhausted into the envi
`ronment. The rotor (32) contains a magnet proximal to the
`active spreader plate. A rotatable impeller (54) inside of the
`active spreader plate and immersed in the heat transfer fluid
`is motivated to rotate by the moving magnetic fields ema
`nating from the magnet, which in turn impels the heat
`transfer fluid to circulate through the flow channels (50). A
`bypass flow channel (64) conducts heat transfer fluid to the
`center of the impeller (54).
`FIG. 4 shows an alternative preferred embodiment of an
`active spreader plated designed to transfer heat from a heat
`Source on a first Surface of the active spreader plate to a heat
`absorbing device on a Second Surface of the active spreader
`plate, where the normals to the first and Second Surfaces are
`perpendicular to each other. This embodiment of the active
`Surface plate is optimized for cooling a Solid State laser bar.
`The heat Source (2) is a semiconductor (4), which is ther
`mally attached to a small passive spreader plate (8). The
`Small spreader plate (8) thermally contacts a Small fin array
`(52). The elements of the active spreader plate, fan, and fin
`means have been previously described. Solid State laser
`array bars are one of the most demanding electronics cooling
`applications. A typical device might contact a heat Sink Over
`an area 0.6 mmx10 mm, and dissipate 40 watts of waste heat
`at a junction temperature of 55 C. The aerial thermal
`resistance of this combination is 0.015 C. cm per watt
`(assuming that the heat sink requires a 10 C. temperature
`gradient to operate), which is about 20 times Smaller (more
`difficult) than what microprocessors will require over the
`next decade. Typically high power continuous duty laser
`bars are cooled today with refrigerated water. The design
`shown in
`FIG.3 has sufficiently low thermal resistivity that only the
`temperature drop between the junction and ambient
`(assumed to be 35° C) is required. In this application the
`heat transfer fluids of choice are liquid metals, Such as alloys
`of bismuth, tin, lead, cadmium, indium, mercury, gallium,
`Sodium, and potassium. These alloys have low Viscosity and
`high thermal conductivity compared to alternative heat
`transfer fluids. The most preferred embodiment of a laser bar
`cooler uses an alloy of Sodium and potassium, chosen So that
`the melting point stays below the coldest expected ambient
`temperature.
`FIG. 5 shows a preferred embodiment of an active
`Spreader plated, in which the active spreader plate of FIG. 2
`has been augmented with a second active spreader plate (70)
`attached to the heat absorbing devices (28), so that the first
`and Second heat active spreader plates are each attached to
`different surfaces of the heat absorbing device (28). Multiple
`conduits (74 and 78) are hermetically sealed to the first and
`Second active spreader plates, flowably connecting the flow
`channels (50) and (72) with passageways (76). In this
`alternative preferred embodiment, the Second active
`spreader plate and the fan frame (30) form a single fabri
`cated component. The heat absorbing devices (28) are
`preferably fin means. The principle advantage of the design
`shown in FIG. 5 is that the temperature gradient within the
`fin means is reduced, due to the shorter path length for heat
`
`Shenzhen Apaltek Co., Ltd. Ex. 1008, Page 17 of 23
`Shenzhen Apaltek Co., Ltd. v. Asetek Danmark A/S
`IPR2022-01317
`
`

`

`7
`conduction that results from heating the fin means from two
`Surfaces. This advantage could, for example, allow the use
`of lighter and leSS expensive fin means.
`FIG. 6 shows several embodiments of fin means, all of
`which are know in the prior art Each of the fin means is
`characterized by a thermal conduction means Such as pins
`(102), fins (112), foil (122), stampings (132), wires (142),
`louvers (152), plates, or sheets. The thermal conduction
`means are arrayed So as to be permeable to a flowing heat
`transfer fluid Such as the atmosphere, while also thermally
`contacting one or more Surfaces (104). The fin means
`function to increase the effective area of contact between a
`heat transfer fluid Such as the atmosphere and one or more
`Surfaces (104). Fin means can be manufactured by forging,
`folding, gluing, Welding, brazing, casting, molding, coining,
`or other processes. Fin means are preferably composed of
`aluminum, and can also be formed using metals Such as
`copper, aluminum, iron, Zinc, nickel, and Silver, as well as
`composite materials including graphite filled plastics. The
`Surfaces of the thermal conduction means can be grooved,
`textured, dimpled, embossed, or drilled to increase their
`Surface area in contact with the heat transfer fluid.
`FIG. 7 shows an assembly of a heat Sink containing an
`active spreader plate. A heat Source (2) is attached to the
`bottom sheet (202) of the active spreader plate assembly
`through a compliant insulating layer (14). If the heat Source
`is a Semiconductor device which is Sensitive to magnetic
`fields, the bottom sheet (202) should be composed of a
`ferromagnetic material that will shield the heat Source from
`magnetic field Sources in the active spreader plate. Heat
`from the heat Source passes through the bottom Surface (24)
`of the bottom sheet (202) and into a fin means (52) attached
`to the top Surface of the bottom sheet (202). The fin means
`(52) is contained in a pocket (230) bounded by a lower
`stamped plate (204), the bottom sheet (202), and a medial
`sheet (206). Heat transfer fluid enters the pocket (230)
`through four holes (228), passes in contact with the fin
`means (52), and exits through slots (232). An upper Stamped
`plate (208) is attached to the top of the medial sheet (206).
`A channel forming sheet (210) is attached to the top of the
`upper stamped plate (208), and a top sheet (212) Seals the top
`of the channel forming sheet (210). The top sheet (212) is
`easily penetrated by externally generated magnetic fields;
`the top sheet (212) can be a poor electrical conductor and a
`non-ferromagnetic material, or it be So thin that its effect on
`the magnetic fields is negligible. A rotatable impeller (54) is
`trapped in coaxial cavities (220) in the channel forming
`sheet (210) and the upper stamped plate (204). The rotatable
`impeller (54) is shown mounted on an axle (214) which is
`seated in the fin means (52) and which protrudes through the
`medial sheet (206). The bottom sheet (202) and fin means
`(52) are preferably metallic. The lower stamped plate (204),
`the medial sheet (206), the upper stamped plate (204), the
`channel forming sheet (210), and the top sheet (212) are
`preferably formed from plastic. Fin means (28) attaches to
`the upper Surface (26) of the top sheet (212). A fan housing
`(30), rotor (32), and fan blades (34) are attached to the top
`of the fin means, rotatably Suspending a permanent magnet
`(56) adjacent to the impeller (54). Rotation of a permanent
`magnet (56) motivates the impeller to rotate, thereby impel
`ling the heat transfer fluid Sealed inside the active spreader
`plate rising through slots (232) to flow radially away from
`the impeller (54) through channels (222) in the upper
`stamped plate (204), then to flow in the plane of the channel
`forming sheet (210) and in thermal communication with the
`fin means (28), to then flow radially towards the impeller
`through channels (226), where the fluid enters the lower
`
`5
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6,019,165
`
`8
`pocket through four holes (228). A gas filled bladder (not
`shown) resides in a cavity (234) in the upper Stamped plate
`(208); the bladder and its function will be described later.
`The entire heat sink assembly is shown in (240). The
`components of the active spreader plate shown in FIG. 7 are
`designed to be Stamped from sheets and Subsequently
`assembled with adhesives, ultraSonic bonding, Solvent
`bonding, or welding. Those skilled in the art will recognize
`that the individual components of the active spreader plate
`could be molded, and that several of the described compo
`nents can be functionally combined if the components are
`molded.
`FIG.8 shows a detailed heat transfer fluid flow pattern for
`the heat sink assembly described in FIG. 7.
`FIG. 9 shows several examples of fluid impellers that can
`effectively be used in an active spreader plate. Each is
`motivated by moving external magnetic fields. In the upper
`left is a viscosity pump (260). A heat transfer fluid feeds the
`Viscosity pump (260) through a channel (262) leading to a
`circular cavity (266) in the composite Substrate material
`(264). A rotor (268) formed with lands and grooves and a
`central opening (270) rotates as shown in the cavity (266)
`due to the action of external magnetic fields. Viscous drag of
`the heat transfer fluid between the rotor (268) and the cavity
`(266) drives the heat transfer fluid towards the center of the
`rotor (268). The heat transfer fluid leaves the pump (260) by
`passing through a channel (272) under the rotor (268) which
`joins with the exit channel (274). In the upper right is a
`displacement pump (280). A heat transfer fluid feeds the
`displacement pump (280) through a channel (282) leading to
`a circular cavity (286) in the composite Substrate material
`(284). An eccentric disk shaped rotor (288) in the cavity