WO1996037366A1 - Materiau formant enceinte pour dispositif de refroidissement de composants a deux phases - Google Patents

Materiau formant enceinte pour dispositif de refroidissement de composants a deux phases Download PDF

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Publication number
WO1996037366A1
WO1996037366A1 PCT/US1996/007372 US9607372W WO9637366A1 WO 1996037366 A1 WO1996037366 A1 WO 1996037366A1 US 9607372 W US9607372 W US 9607372W WO 9637366 A1 WO9637366 A1 WO 9637366A1
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WO
WIPO (PCT)
Prior art keywords
layer
vapor
flexible
heat
condenser
Prior art date
Application number
PCT/US1996/007372
Other languages
English (en)
Inventor
Ralph I. Larson
Richard J. Phillips
Original Assignee
Aavid Laboratories, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aavid Laboratories, Inc. filed Critical Aavid Laboratories, Inc.
Priority to AU58691/96A priority Critical patent/AU5869196A/en
Publication of WO1996037366A1 publication Critical patent/WO1996037366A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/085—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/28—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42
    • B32B27/281—Layered products comprising a layer of synthetic resin comprising synthetic resins not wholly covered by any one of the sub-groups B32B27/30 - B32B27/42 comprising polyimides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B37/00—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding
    • B32B37/14—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers
    • B32B37/15—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state
    • B32B37/153—Methods or apparatus for laminating, e.g. by curing or by ultrasonic bonding characterised by the properties of the layers with at least one layer being manufactured and immediately laminated before reaching its stable state, e.g. in which a layer is extruded and laminated while in semi-molten state at least one layer is extruded and immediately laminated while in semi-molten state
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F3/00—Plate-like or laminated elements; Assemblies of plate-like or laminated elements
    • F28F3/12—Elements constructed in the shape of a hollow panel, e.g. with channels
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/42—Fillings or auxiliary members in containers or encapsulations selected or arranged to facilitate heating or cooling
    • H01L23/427—Cooling by change of state, e.g. use of heat pipes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/306—Resistant to heat
    • B32B2307/3065—Flame resistant or retardant, fire resistant or retardant
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B32B2307/7242—Non-permeable
    • B32B2307/7246—Water vapor barrier
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2311/00—Metals, their alloys or their compounds
    • B32B2311/24—Aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/10—Polypropylene
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/0001—Technical content checked by a classifier
    • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Definitions

  • This invention relates, in general, to cooling apparatus for heat dissipating components including electronic devices, such as discrete electronic components and integrated circuit chips, and, in particular, to cooling apparatus which utilizes both a liquid phase and a vapor phase of a coolant to provide enhanced heat transfer.
  • liquid cooling techniques have conventionally been used with high-power electronic components. These techniques generally fall into two broad groups comprising single phase and two phase cooling systems.
  • single phase liquid cooling system the liquid coolant remains as a liquid over the normal operating range of the system. This is in contrast to a two phase cooling system in which the liquid coolant changes from its liquid phase to a vapor phase during at least one point in the normal operating range.
  • An example of a single phase liquid cooling system which uses natural convection comprises a hermetic enclosure which encloses the heat-generating component device.
  • the enclosure may be provided with external fins and is filled with a conductive liquid coolant. Heat is transferred from the heat dissipating component to the coolant mainly by conduction and from the coolant to the enclosure by natural convection.
  • the enclosure itself may be cooled by circulating air around the outside of the enclosure.
  • Such a cooling method is effective but involves additional problems, such as chemical incompatibilities between the component and the coolant and difficulty of maintaining the component.
  • two phase liquid cooling systems have been used to overcome the problems of single phase systems.
  • a low boiling point liquid coolant is used; the liquid is vaporized or boiled by heat dissipated by the electronic component and the vapor travels to a condenser.
  • the condenser the coolant vapor is converted back into a liquid and the liquid is then returned to the heat dissipating component so that the boiling/condensing cycle can be repeated.
  • U.S. Patent 3,741 ,292 An example of a two phase device in which the heat dissipating component is directly immersed in the coolant is shown in U.S. Patent 3,741 ,292.
  • the heat dissipating component is located in a hermetic enclosure which contains a sufficient pool of low boiling point dielectric liquid coolant to partially fill the enclosure and immerse the heat dissipating component.
  • the liquid is evaporated by the heat dissipated by the component and the resulting vapor is collected in the enclosure space located above the liquid pool.
  • This enclosure space is filled with fins extending inwardly into the enclosure which fins serve as a condenser for the coolant vapor.
  • the enclosure is also equipped with external fins which serve as an air cooled heat sink to cool the enclosure. As the vapor condenses it runs back into the liquid pool under the influence of gravity.
  • a heat pipe consists of an elongated, hermetic container with thermally conductive walls, for example, a copper pipe is often used.
  • One end of the container acts as an evaporator and the other end acts as a condenser.
  • a wick or other capillary device extends along the length of the container - if a copper pipe is used, the wick often consists of a fine mesh screen extending along the inside of the pipe.
  • the container is partially filled with a low boiling point liquid coolant and the residual non-condensing gases are purged. More particularly, during construction of the heat pipe, the air which normally fills the container is purged by boiling the coolant to drive off the air. The container is then sealed.
  • the evaporator end is mounted next to the heat dissipating component and heat is transferred by conduction through the container wall of the device. As the coolant evaporates or boils, the resulting vapor travels down the container to the condenser end where it condenses back to a liquid. The liquid is returned to the evaporator end by means of the wick (or alternatively by gravity).
  • both the direct immersion enclosure and the heat pipe can transfer heat efficiently away from a heat dissipating component, but also have limitations. More specifically, both the direct immersion enclosure and indirect heat pipe two phase devices utilize rigid, hermetically sealed containers and, thus, the internal pressure of the devices does not remain equal to the ambient environmental pressure.
  • a heat pipe device most of the non-condensable residual gas is purged during manufacture to prevent excessive pressures in the device in the normal temperature operating range. Consequently, when the device is not operating, there usually exists a slight vacuum in the device at normal ambient temperature. Accordingly, the device is prone to leaks, and, if a leak occurs, air will be drawn into the device. Later, when the device is operating, the increased pressure produced by the air may drive some of the liquid out of the container. Consequently, the devices are not reliable in an environment were long term maintenance is impossible.
  • the container walls are rigid, as the liquid coolant vaporizes, the pressure inside the prior art devices increases, in turn, increasing the coolant boiling point.
  • the increase in boiling point is exacerbated by the presence of residual air and air introduced into the system by leaks. Consequently, the coolant liquid within the devices does not have a single boiling point but rather a range of boiling points and the devices do not operate at a single temperature but instead operate over a relatively broad range of temperatures.
  • Overshoot occurs during device warmup because the liquid coolant does not begin to boil when it reaches its boiling point. Instead, the liquid temperature continues to increase until the temperature is significantly over the normal coolant boiling temperature and boiling suddenly erupts. When boiling finally does occur, the device temperature returns to its normal operating temperature range. Overshoot is highly undesirable as it stresses the components to be cooled and, in some cases, may cause a component to temporarily operate outside its normal operating temperature range.
  • a two phase liquid cooling system has a structure in which the internal pressure of the system remains substantially equal to the ambient environmental pressure over the entire thermal operating range. Operation without an internal pressure change is achieved by constructing the system with at least one flexible container wall.
  • the wall has sufficient flexibility that the wall expands as the coolant vapor expands thereby maintaining the internal container pressure substantially the same as the ambient pressure. Consequently, the liquid coolant boils within a single, very narrow temperature range and the inventive device can maintain a heat dissipating device with that range.
  • the cooling system consists of a rigid evaporator unit which is attached to the heat dissipating component and a condenser unit.
  • the evaporator unit and the condenser unit are connected together by rigid or semi-flexible tubes.
  • the condenser is constructed with at least one wall that is sufficiently flexible to maintain the internal pressure of the system substantially at the ambient pressure.
  • residual, non-condensing gases such as air are not purged from the system, but remains in the system so that when the device is not operating, the internal pressure remains, near to, or substantially at ambient pressure.
  • the inventive device is not prone to the leaking problem that is found in prior art heat pipes.
  • the overshoot problem of the prior art devices is reduced by allowing residual gases to remain in the cooling system. More particularly, sufficient residual gas is maintained in the system so that some of the gas dissolves in the liquid coolant when the device is not operating and is at ambient temperature. During warmup, the residual gas comes out of solution and creates nucleation sites that initiate boiling and prevent overshoot. Additional nucleation sites can also be added to reduce overshoot by treating the inside surface of the evaporator unit, for example by laser machining, to create nucleation sites.
  • the rigid evaporator can be either an integral part of the component package or a separate part which is attached to the component package.
  • the evaporator unit and the condenser unit are interconnected via one or more flexible pipes which can be preferably made of plastic tubing.
  • the coolant liquid is evaporated or boiled in the evaporator unit and travels to the condenser unit where the liquid condenses.
  • the condensed liquid is returned to the evaporator unit by gravity.
  • the condenser unit can be made entirely of a polymeric material.
  • the condenser may be entirely constructed of thin, flexible polymeric films or sheets.
  • a portion of the condenser can be constructed of thicker polymeric material by means of injection molding or blow molding and the remaining portions constructed of flexible polymeric material films in order to provide a flexible wall to maintain the internal pressure equivalent to the ambient pressure.
  • a portion of the condenser is constructed of sheet, or molded, metal or plastic formed with fins for enhanced heat transfer and a thin polymeric sheet is sealed to the metal condenser portion to provide a flexible wall.
  • the particular structure of the material from which the condenser is formed may be altered, but a multi-layer structure is preferred.
  • a three-layer material is preferred which has a non-flammable outer layer such as polyimide (e.g. KAPTON ® ), a central layer which is a vapor barrier, such as aluminum, and an inner layer which is a heat-sealable thermal plastic, such as polypropylene.
  • a KAPTON ® outer layer also provides the advantage of durability.
  • the layers can be bonded together with adhesive and, with the thermal plastic layer on the inside, the material may be bonded to itself to form a vapor-tight enclosure. If the material is particularly flexible (i.e.
  • a flexible bag-like structure may be formed by folding a piece of the three-layer material and heat-sealing the thermal plastic layer to itself along the three sides away from the fold.
  • a bag-like structure may be formed by two pieces of the three-layer material which are arranged so the thermal plastic layer of one faces the thermal plastic layer of the other, and which are subsequently heat-sealed to each other along a perimeter which encloses a coolant liquid inside.
  • a portion of the condenser is constructed of a vacuum-formed plastic material that has a vapor-deposited layer of metal applied to the plastic after it has been vacuum- formed.
  • the metal barrier helps make the enclosure air and vapor tight. The metal is not deposited in those areas that are used for heat seals.
  • Figure 1 is a schematic top view of an electrical component system, such as might be used in a personal computer, which system includes a plurality of expansion boards and incorporates one embodiment of the present invention including an evaporator and a condenser.
  • Figure 2 is a side view of the printed circuit board shown in Figure 1 with some of the expansion boards removed to show the condenser unit.
  • Figure 3 is a front view of the printed circuit board with some of the expansion boards removed to illustrate the condenser and its fins.
  • Figure 4 is an exploded view of the evaporator unit illustrating one manner of assembling the evaporator unit.
  • Figure 5 is an assembled view of the evaporator unit.
  • Figure 6 is a side view of the evaporator unit mounted on the heat dissipating component illustrating the use of clips to hold the evaporator on the component.
  • Figure 7 is a partial sectional view of the evaporator unit illustrating the manner of attaching the clips to the evaporator unit and to the component.
  • Figure 8 is a top view of one embodiment of a heat spreader plate showing heat spreading fins formed by grooves cut in the plate.
  • Figure 9 is a partial cross sectional view of the evaporator unit illustrating an alternative method of assembling the unit.
  • Figure 10 is a schematic cross sectional plan view of the condenser unit taken along the section lines 10-10 in Figure 3.
  • Figure 11 A is a partial cross sectional view of an embodiment of the condenser unit which is entirely comprised of flexible walls.
  • Figure 11 B is a partial cross section through a multi-layer flexible sheet as might be used in the flexible walls.
  • Figure 11C is a partial cross section through a multi-layer flexible sheet, which shows adhesive layers between the material layers.
  • Figure 12A is a partial cross sectional view of an embodiment of the condenser in which the flexible portion is heat sealed to a rigid portion, and folded fins are provided for additional heat transfer.
  • Figure 12B is a partial cross sectional view of an embodiment of the condenser in which a rigid portion occupies only one portion of one side of the condenser.
  • Figure 12C is a partial cross sectional view of an embodiment of the condenser unit which is comprised partially of rigid walls and partially of flexible walls.
  • Figure 13 is a perspective view illustrating an embodiment in which a condenser unit 8 with a circular cross section is mounted on top of the evaporator unit.
  • Figure 14 is a perspective exploded view illustrating an embodiment in which a condenser unit 8 utilizes forced air flow.
  • Figure 15 is a perspective view illustrating the embodiment shown in Figure 14 in assembled form.
  • Figure 16 is a plot of temperature versus time of the temperature of a heat dissipating component which is cooled with one embodiment of the present invention.
  • Figure 1 is a schematic top view of a main printed circuit board or
  • Mother board of the type that is commonly used in a personal computer system.
  • Figures 2 and 3 show the side and front views of mother board 1 , respectively.
  • Mother board 1 has a number of components mounted thereon which comprise the personal computer circuitry. These components include a power supply which is shown schematically as box 2 and a disc drive schematically shown as box 3.
  • mother board 1 would normally be populated with many integrated circuit chips which are not shown in Figure 1 for clarity. Typically, one more of such integrated circuit chips would be high-power chips and would be candidates for one or more of the cooling devices of the present invention. Such high-power chips might, for example, comprise the microprocessor of the personal computer system.
  • expansion card boards 4 are shown inserted into sockets 9 and 13. Each of the boards has a plurality of integrated circuit chips 14 mounted thereon. Boards 4 have been omitted from the side and front views of Figures 2 and 3 in order to expose the condenser unit 8 of the present invention. Although several boards 4 are shown inserted into mother board 1 in Figure 1 , it should be understood that, in a typical computer system, there may be no expansion boards inserted in the slots or all of the slots may be filled with expansion boards.
  • the condenser unit 8 of the inventive cooling system is designed to fit into an empty expansion card socket 9, thereby fixing the condenser unit 8 in a vertical position which is ideal for coolant drainage and to allow optimum air circulation around fins 11.
  • Figure 2 shows a side view of the mother board 1 shown in Figure 1 which illustrates the condenser unit 8 construction in more detail.
  • condenser unit 8 is equipped with fins 11 which increase the surface area and aid in transferring heat between the condenser unit 8 and the surrounding air.
  • fins 11 are hollow and communicate with the interior of the condenser unit 8 so that the fins also increase the amount of surface area presented to the coolant vapor within the condenser unit 8, thereby increasing the heat transfer from the vapor to the condenser unit 8.
  • FIG 3 shows a front view of the mother board 1 with the expansion cards 13 removed illustrating the condenser unit 8.
  • the condenser unit 8 is shown with fins 11 on one side however, fins maybe mounted on one or both sides of the condenser unit 8.
  • hook 12 is formed at the top of the condenser unit 8, which hook allows the condenser unit 8 to be hung from the top of an existing expansion board if no empty expansion slot sockets are available (hook 12 has been omitted from Figure 1 to illustrate fins 11).
  • the evaporator unit 5 of the inventive cooling system is illustratively shown mounted on top of a high-power integrated circuit chip 10 which is not visible in Figure 1 , but is shown in Figures 2 and 3.
  • Evaporator unit 5 is connected to the condenser unit 8 by means of coolant tubes 6 and 7.
  • Liquid coolant (not shown) in evaporator unit 5 is evaporated by heat dissipated by circuit 10 and the coolant vapor (not shown) is conveyed by vapor tube 6 to condenser unit 8 were the vapor condenses to a liquid and the liquid returns to the evaporator unit 5 via the condensate tube 7 under the influence of gravity.
  • Figure 4 shows an exploded view of the evaporator unit 5.
  • the evaporator unit 5 can be either an integral part of the electronic component package or manufactured separately and attached to the package.
  • the construction illustrated in Figure 4 is designed to be manufactured separately and attached to the component package during, or after, assembly of the printed circuit board 1.
  • the evaporator unit 5 consists of an evaporator cover 30 which may be made of metal or, preferably, polymeric material.
  • the evaporator cover 30 has a recess 36 which receives a heat spreader plate 34 which conducts the heat generated by the heat dissipating component into the interior of the evaporator unit 5.
  • the heat spreader plate 34 is sealed to the evaporator cover 30 by means of an O-ring seal 32 which fits into groove 38 in cover 30.
  • the heat spreader plate 34 and the evaporator cover 30 are fastened together by means of screws 40.
  • the heat spreader plate 34 is also shown in more detail in Figure 8 and can be smooth or flat in cooling systems designed for low-power components, however pin fins or tab fins may be used in high-power designs to help draw the coolant into the hottest areas of the spreader plate.
  • heat spreader plate 34 has a raised portion
  • the heat spreader plate 34 is generally made of a high-conductivity material such as copper, diamond-copper composite, aluminum or, in some cases, high-conductivity plastic materials.
  • the heat spreader plate 34 is provided with four threaded holes, 58, into which screws 40 are threaded to hold plate 34 to the evaporator unit cover 30.
  • the evaporator unit 5 can be attached to the integrated circuit chip 10 using a variety of conventional techniques.
  • the evaporator unit 5 can be attached to the chip 10 by epoxy cement, soldering, thermal grease or contact pressure (applied by means of clips or springs).
  • the evaporator cover 30 and the heat spreader plate 34 of porous materials in which case the evaporator unit 5 can be attached to the chip 10 by means of capillary suction forces.
  • FIG. 6 Illustrative C-shaped clips or springs 52 and 54 are shown in Figure 6 which clips attach the evaporator unit 5 to the chip 10.
  • Figure 7 shows a partial cross sectional view of the evaporator unit 5 showing a T-shaped channel 60 molded into the wall of the evaporator unit 30.
  • Each C-shaped clip 52 has a T-shaped end 56 which fits into the channel 60 and fastens the clip to the evaporator unit 5.
  • a right angle bend 57 at the lower part of each clip, such as clip 52 slips over the lower edge of chip 10 and holds the evaporator unit 5 firmly to the chip 10.
  • the evaporator unit 5 and the condenser unit 8 are connected together, via one or more tubes, of which tubes 6 and 7 are shown.
  • these tubes are flexible may preferably be made of flexible plastic tubing such as TYGON ® tubing.
  • TYGON ® tubing may limit the size of the pipes connected to it and it may be necessary to use two or more tubes for either or both of the vapor tubes and the condensate tubes in order obtain the necessary flow cross section. In general, the cross sectional area of the vapor tube will be larger
  • the pressure in the evaporator will increase and thereby increase the boiling point of the coolant. Consequently, the vapor and condensate tubes must be arranged such that a free flow of vapor and liquid occurs during the operation of the device.
  • Figure 9 shows an alternative method of attaching an evaporator cover 30 comprised of polymeric material to the heat spreader plate 34.
  • the heat spreader plate 34 is coated with a vacuum-formed layer of polymeric material 65.
  • Layer 65 allows the polymeric evaporator cover to be solvent welded to the polymeric layer 65.
  • a suitable solvent is applied to the lower edge 66 of evaporator cover 30 which then bonds to the upper surface
  • Addition screws 40 can be provided to increase the mechanical integrity of the structure.
  • FIG 10 shows an illustrative construction of the condenser unit 8 of the present invention.
  • the condenser unit 8 is preferably constructed of polymeric material and shaped such that the condensate returns to the condensate line 7 under the influence of gravity. Condensate return is accomplished by making the bottom edge of the condenser unit 8 slanted so that a "sump" area 82 is formed directly over the condensate tube 7.
  • a baffle 76 may be added to the condenser unit 8 so that vapor entering the condenser unit 8 from the vapor tube 6 passes directly upwards to the upper portion of the condenser unit 8 and does not mingle with the condensed vapor on entry to the condenser.
  • the condenser unit 8 shown in Figure 10 is provided with a tab 78 which can fit into an expansion slot socket on the mother board 1 as shown in Figures 1-3.
  • condenser unit 8 can be made of either thick or thin materials and can be injection-molded or blow-molded. Alternatively, where small size is desired, thin sheet materials can be used since there is a smaller thermal gradient across the material.
  • Figure 11 A illustrates a partial cross section of an embodiment of the condenser unit which is entirely comprised of flexible sheets of polymeric material. The polymeric material
  • the fins 102 which may, for example, be polypropylene, can be vacuum formed over a rigid mandrel (not shown) to form the fins 102.
  • the distance 104 between the fins is selected in accordance with conventional convection theory to maximize heat transfer between the condenser unit and the surrounding environment.
  • the width of the fins themselves is minimized in order to increase the heat transfer from the vapor in the condenser to the condenser walls.
  • the vapor tube 6 and the condensate tube 7 can be attached to the sheet material 100 by cementing the tubes or by suitable fittings 106.
  • the polymeric sheets may be multi-layered to limit gas permeability.
  • the polypropylene sheets illustrated in Figure 11A may consist of a polypropylene sheet 100 covered on one side by a layer of vapor-deposited aluminum 101.
  • the vapor deposited aluminum 101 may, in turn, be covered by a layer of polycarbonate, polyester or KAPTON ® 103 to protect it.
  • the sheet of thermal plastic material 100 can be vacuum formed to produce extended surface for enhancement of heat transfer.
  • vacuum forming may include the creation of hollow, longitudinal continuous fins, and pin fins 102.
  • the orientation of the fins can be readily formed to follow the air flow streamlines on the outside of the condenser and to enhance condensate return.
  • the vapor-deposited aluminum layer 101 can be applied directly to a vacuum formed sheet of thermal plastic material 100, as shown in Figure 11B.
  • the vapor-deposited thermal layer can also be applied to the inside of the thermal plastic material 100, but a mask must be used to prohibit application of the vapor-deposited aluminum layer 101 in those areas intended for use as heat seals.
  • any suitable metal may be substituted for the vapor-deposited aluminum layer 101.
  • the material shown in Figure 11 B is particularly useful for the characteristics which each of the three layers contributes.
  • the layer 103 (preferably KAPTON ® polyimide) should be a non-flammable material.
  • the layer 103 protects the container from contact with high-temperature devices which may come into contact with the container and which might consequently damage it.
  • the KAPTON ® also provides the film with strength and durability, thus reducing the incidence of tearing or puncturing, and the
  • KAPTON ® is preferred partly because of its U.L. 94VTM-0 rating in the Underwriters Laboratories flammability classification. If other materials are to be used in place of KAPTON ® , it is preferred that they are no more flammable than a classification of U.L. 94VTM-1.
  • the aluminum layer 101 provides a vapor barrier that prevents the permeation of air or water vapor into the condenser, or permeation of coolant vapor out of the condenser, any of which would, over time, alter the performance of the system.
  • the inner layer 100 (a thermal plastic such as polypropylene) may be used for heat-sealing.
  • a thermal plastic inner layer 100 is useful for sealing to itself. If the material is of a high degree of flexibility (i.e. is not made to retain a pre-formed shape), an air-tight, bag-like enclosure may be formed by heat- sealing the material either to itself, or to another piece of the same material. A good bond is achieved by heat-sealing together two separate thermal plastic layers. This simplifies manufacture of the condenser since only heat and pressure are required to enclose the liquid coolant. Furthermore, for the higher flexibility, bag-like embodiment of the condenser, the aluminum layer may supplied in the form of a foil, rather than through vapor deposition.
  • the polypropylene layer 100 is approximately 0.003" thick, and is sealed to a 0.0005" layer 101 of aluminum foil with a 0.00046" layer 107 of MOR-PRIME ® primer in between.
  • the other side of the aluminum layer 101 is
  • SUB.STITUTE SHEET (RULE 26) bonded to a 0.001" KAPTON ® layer 100 by a more conventional adhesive which, in the present embodiment, is a 0.00046" layer of silicone, or silicone- based material.
  • the material of the above embodiment has proven to be superior to prior art materials which had the same three layers, but which also included a layer of polyester between the KAPTON ® layer and the aluminum layer of the structure, and which may have used different adhesives. Most notably, the material of the present embodiment has superior durability in that the tendency of the layers of the material to separate under stress or wide temperature variation is greatly reduced relative to the prior art material.
  • At least one wall of the condenser unit 8 of a thin gauge metal, for example aluminum, which metal can also be formed with fins for enhanced heat transfer.
  • a thin flexible sheet can then be sealed to the metal wall to provide the flexible wall necessary for zero pressure operation.
  • FIG 12A illustrates a partial cross-section of a further embodiment of the condenser unit which is partially comprised of a rigid material and partially comprised of flexible sheets.
  • the rigid part 150 of the condenser unit 120 may be comprised of a metal sheet such as aluminum.
  • Aluminum folded fin 152 may be epoxied or arc welded to the rigid part 150.
  • An additional rigid stiffener plate 151 may be epoxied or arc welded to the folded fin 152 to provide additional stiffness if required.
  • the flexible portion 126 of the condenser may be comprised of a sheet material such as polypropylene and may also have hollow fins 128 molded into it. The flexible portion 126 is heat sealed to the rigid portion 150 in the areas 130 and 132 to form a sealed unit.
  • Figure 12B illustrates an embodiment in which the rigid part 141 occupies only a portion of one side of the condenser unit 140.
  • An additional sheet of flexible thermal plastic material 142 is heat sealed to the perimeter of the flexible thermal plastic material 126 in the areas 143 and 144.
  • the flexible plastic material 142 is also heat sealed about the perimeter of the rigid part 141 in the areas 145 and 146 to form a sealed unit.
  • folded fin 152 may be epoxy bonded, heat sealed or arc welded to the rigid part 141 and to an optional rigid stiffener plate 151.
  • Figure 12C illustrates a partial cross section of a further embodiment of the condenser unit which is partially comprised of a rigid material and partially comprised of flexible sheets.
  • the rigid part 122 of the condenser unit 120 may be comprised of a polymeric material such as polypropylene or may be comprised of a metal such as aluminum. Fins 124 may be molded into the rigid material as shown in Figure 12C or the rigid condenser section may consist of a smooth plate.
  • the flexible portion 126 of the condenser may be comprised of a sheet of polymeric material such as polypropylene, and may also have fins 128 molded into it. The flexible portion 126 is heat-sealed to the rigid portion 122 in the areas 130 and 132 to form a sealed unit.
  • the vapor and condensate tubes, 6 and 7, are preferably connected to the rigid portion as shown in Figure 12C.
  • Condenser unit 8 may also have spatial configurations different from that shown in Figure 10.
  • condenser unit 8 may be circular, or square in cross section.
  • the condenser unit 8 can also be located in almost any expansion slot location as shown in Figures 1-3.
  • the condenser unit 8 In lap-top, portable notebook and sub notebook size computers, the condenser unit 8 may be located on the backside of a flip-up display screen typically found in such computers.
  • a "chimney" enclosure can also be used to increase efficiency.
  • Other locations for the condenser unit 8 include the inlet or outlet of the power supply box 2. In designs where vertical height is not a problem above the chip 10 that is to be cooled, it is also possible to mount the condenser unit 8 on top of the evaporator unit 5.
  • FIG. 13 illustrates a condenser with a circular cross section.
  • the condenser unit 8 can also be made integral with the evaporator unit 5 thereby eliminating the need for the vapor and condensate tubes 6 and 7.
  • FIGS 14 and 15 show an exploded and assembled view of such an illustrative configuration, respectively.
  • the condenser unit 8 in this embodiment comprises a unit with a substantially rectangular cross section.
  • the condenser unit 8 has a number of through holes 80 which pass from side 82 to side 84.
  • a conventional electric fan 86 is mounted on one side 84 of the condenser unit 8 by means of screws 90.
  • the fan is covered by a cover 88.
  • the unit can be mounted on a stand 92.
  • the condenser unit 8 can be fabricated by injection or blow molding the unit 8 in two halves and selling the halves together by cementing, heat sealing or ultrasonic welding. Bevels 94 are located around each of the holes 80 to facilitate molding of the polymeric parts. However, as previously mentioned, because the condensate returns to the evaporator unit 5 by gravity, in all gravity-return embodiments, the condenser unit 8 must be located above the evaporator unit 5 and there must be no portion of either the vapor tubing 6 or the condensate tubing 7 that dips below the height of the evaporator unit so that no air pockets are formed in the tubing connecting the evaporator unit 5 and the condenser unit 8. However, other embodiments can use conventional pumps or wicking mechanisms to return the condensate to the evaporator unit 5. In these cases it is not necessary for the condenser unit 8 to be above the evaporator unit 5.
  • At least one flexible wall is provided in the system which allows the system to change in volume in order to maintain the internal system pressure substantially equal to the ambient pressure.
  • the flexible walls have been located in the condenser in the embodiments discussed above, the flexible walls may be located in any other part of the system including the evaporator. Alternatively, either or both of the vapor and condensate conduits may be made sufficiently flexible to allow the system to operate with a zero pressure differential.
  • the cooling system is partially filled with a liquid coolant during operation.
  • a liquid coolant can be used based on several factors including, but not limited to, boiling or evaporation temperature (which should be between 55°C and 80°C), chemical compatibility with the components of the evaporator unit 5 and the condenser unit 8, chemical stability, toxicity and cost.
  • Coolants which are suitable for use with the invention include ethyl alcohol, methanol and fluorochemicals, such as FLUORINERT ® manufactured by the Minnesota Mining and Manufacturing Company located in St. Paul Minnesota.
  • the present cooling system is not purged of residual gas during construction. Instead coolant is added to the system and the system is sealed including residual gas such that the internal pressure of the cooling system at ambient room temperature is the same as the ambient environment pressure (typically one atmosphere). As heat dissipated by the heat-generating integrated circuit causes the coolant to approach boiling, some of the residual gas dissolved in the coolant comes out of solution and activates nucleation sites which initiate boiling substantially at the normal boiling point of the coolant material.
  • Additional nucleation sites may be provided in the evaporator unit 5 by specially treating the inner surface of the evaporator unit 5, for example by laser machining the heat spreader plate and/or the interior of the evaporator cover 30 to provide a pitted surface. If the pits are of suitable shape and size, they will provide nucleation sites which ensure that the coolant boils substantially at its boiling point. The provision of suitable nucleation sites eliminates the overshoot phenomenon which is typically found in prior art devices.
  • the initial temperature of the evaporator unit 5 steadily rises as all of the cooling system units heat up (the time period illustrated as 200 in Figure 16). However, once the coolant boiling point temperature is reached at approximately point 210, the evaporator unit 5 temperature stabilizes and remains relatively constant over the time period 202. There is very little overshoot in the area 212 when the coolant boiling temperature is reached.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Abstract

Système de refroidissement par liquide à deux phases ayant une structure de contenant comportant au moins une paroi assez souple pour se dilater lorsque la vapeur du fluide de refroidissement se dilate, ce qui maintient la pression interne du contenant sensiblement au même niveau que la pression du milieu ambiant. On réduit le dépassement du point d'ébullition du fluide de refroidissement en permettant aux gaz résiduels de demeurer dans le système de refroidissement. Plus particulièrement, il est maintenu suffisamment de gaz résiduel dans le système pour qu'une partie du gaz se dissolve dans le liquide de refroidissement lorsque le dispositif ne fonctionne pas et se trouve à température ambiante. Au cours du réchauffement, le gaz résiduel perd son état dissous et crée des sites de nucléation qui amorcent l'ébullition et empêchent le dépassement du point d'ébullition. Il est aussi possible d'ajouter des sites de nucléation supplémentaires pour réduire ledit dépassement en traitant les surfaces internes de la structure de contenant, par exemple par usinage au laser, pour créer des sites de nucléation. Le condensateur est de préférence constitué d'un matériau formé de trois couches comportant une couche extérieure KAPTON®, une couche centrale en aluminium et une couche intérieure en polypropylène.
PCT/US1996/007372 1995-05-22 1996-05-22 Materiau formant enceinte pour dispositif de refroidissement de composants a deux phases WO1996037366A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU58691/96A AU5869196A (en) 1995-05-22 1996-05-22 Enclosure material for two-phase component cooler

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US44592295A 1995-05-22 1995-05-22
US08/445,922 1995-05-22

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4291085A (en) * 1972-11-10 1981-09-22 Toyo Seikan Kaisha Limited Packaging material for food to be subjected to high-temperature short-time sterilization and process for the preparation thereof
US5000256A (en) * 1990-07-20 1991-03-19 Minnesota Mining And Manufacturing Company Heat transfer bag with thermal via
WO1995007547A1 (fr) * 1993-09-10 1995-03-16 Aavid Laboratories, Inc. Dispositif de refroidissement de composants a deux phases

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4291085A (en) * 1972-11-10 1981-09-22 Toyo Seikan Kaisha Limited Packaging material for food to be subjected to high-temperature short-time sterilization and process for the preparation thereof
US5000256A (en) * 1990-07-20 1991-03-19 Minnesota Mining And Manufacturing Company Heat transfer bag with thermal via
WO1995007547A1 (fr) * 1993-09-10 1995-03-16 Aavid Laboratories, Inc. Dispositif de refroidissement de composants a deux phases

Also Published As

Publication number Publication date
AU5869196A (en) 1996-12-11

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