Title of Invention

COLD PLATE WITH MACHINE GROOVED FLOW PASSAGES FOR ELECTRONICS COOLING

Abstract

Cold plate with machine grooved flow passages for cooling electronic components mounted over the external surface of the device, comprising a base plate (1); a cover plate (3); a clad sheet (2) sandwitched between the base plate (1) and the cover plate (3) by means of vacuum brazing; atleast one inlet port (5) and atleast one outlet port (6) configured at one end and/or opposite ends of the device for fluid entry and exit, characterized in that a plurality of fluid passages constituting of several grooves (4) parallely disposed on the base plate (1) being configured for fluid-flow thereby maintaining an optimum flow-velocity and an improved heat transfer

Full Text

FIELD OF INVENTION The invention relates to an improved Cold Plate device adaptable for cooling the electronic components mounted over the device. The electronic components dissipate thermal loads which need to be removed effectively so as to keep the temperature of the components below certain specified limits in order to make the components function efficiently and to have a longer life. The cooling effect is achieved by providing appropriate flow passages below the mounting surface. A fluid passing through the passages extracts the heat by convection and transfers the extracted heat to an appropriate sink. BACKGROUND ART Commercially available Cold Plates for cooling of power electronics and other high watt density electronics applications, generally configured to have 0.25" copper tubing pressed into a channeled aluminum. Such cold plates comprise 6" and / or 12" long straight plate having beaded fittings. Tap holes can be provided to the cold plates according to requirements. A further design of prior art cold plates relate to a high performance series of Cold Plates. It provides low thermal resistance and dual-sided component mounting, with the capability of being drilled and tapped on one surface. This all-aluminum cold plate is manufactured utilizing vacuum brazing techniques. To build these cold plates, corrugated aluminum fin is brazed into the liquid cavity below the mounting surfaces. US patent No 6367543 BI (Apr. 9, 2002) discloses a liquid cooled heat sink. This sink is having a cooling housing including a peripheral side wall extending from the perimeter of a bottom wall and a lid sized to engage the peripheral side wall so as to form a chamber. A fluid inlet port and a fluid outlet port are defined through the lid, and disposed in fluid communication with the chamber. Another version of liquid cooled heat sink has been disclosed in patent publications US 6;397,932 BI and US 6,719,039 B2. In these versions a plurality of pins projected outwardly from the bottom wall so as to be positioned within the chamber and arranged in a staggered pattern. The pins include an end that engages the undersurface of the lid. A third version of liquid Cooled heat sink has been disclosed in patent publication number US 6,578,626 BI. In this embodiment, a corrugated fin having a plurality of corrugations is positioned within the chamber so that at least one of the corrugations engages the bottom wall and at least one of the corrugations engages the under surface of the lid. The US patent no 6819561 B2 (Nov 16, 2004) describes a heat exchange system achieving similar objects that of the Cold Plate as described hereinabove. The object of the cited invention is to remove the generated heat away from high-power, heat-producing electronic components by conduction and convection. The heat exchange system comprises a metal tube that has been forged and drawn so as to define a flow channel for a cooling fluid, wherein the tube has an inner surface that comprises a plurality of integral fins that are structured and arranged to increase the available surface area of the inner surface of the metal tube exposed to the fluid and an outer surface that is in direct communication with the heat producing components. Coolant fluids are circulated through the flow channel, preferably, at turbulent flow conditions to minimize thermal resistance. The invention further provides a self-cooling self-supporting electronic assembly that comprises one or more high-power electronic devices, the heat exchange systems, and an attaching system for attaching high-power electronic devices to the heat exchange system. US patent no 5924481 describes another type of cooling device for electronic components. A header tank for accommodating refrigerant is formed on one side of the cold plate, on the other side of which an electronic component is mounted. A plurality of loop pipes in which the refrigerant is circulated are connected with the header tank. The plurality of loop pipes are arranged substantially parallel with the cold plate. The radiating area of the loop pipes distant from the cold plate is larger than the radiating area of the loop pipes close to the Cold Plate device. US patent no: US 66.34421, describes a high performance cold plate for electronic cooling. Here a fluid cooling device and a method for manufacturing the fluid cooling device are disclosed. The nula cooling device includes a plurality of cold plate members, each having a plurality of imperforate plate portions and perforate portions arranged in line; and at least one connector for connecting the plate portions together at one end thereof. The cold plate numbers are arranged in a stack, where in respective plate portions of each Cold Plates members are in registration with perforate portions formed in its adjacent cold plate members in the stack. The fluid cooling device can provide very high heat transfer by close clearance laminar developing flow there by increasing the thermal performance of the fluid cooling device while maintaining low pressure drop. The method for manufacturing the fluid cooling device includes performing a plurality of cold plate members from a planner metal type, or thin layer stock; positioning the cold plate members relative to each other so that the respective imperforate plate portions of each cold plate member are in registration with the perforate portions formed in adjacent cold plate members; and joining each cold plate member with the adjacent cold plate members. The Cold Plates of the prior art have the flow paths created by using coiled tubes sandwiched in between two flat plates. In another variant a corrugated fin, having a plurality of corrugations is positioned inside a chamber, keeping other constituent components almost unaltered. The heat removal contemplated in these embodiments by passing the fluid through a tube embedded within the plate, faces high contact resistance due to the metallic joints. In case of cold plates having corrugated fin the brazing joint between the fins and the plate may be ineffective due to uneven joining surfaces and further, owing to presence of comparatively low fluid velocity which may in turn affect the heat transfer process. Yet another variant describes plurality of pins projected outwardly from the bottom wall so as to be positioned within the bottom and the top plates with corresponding side walls and inlet outlet connectors. Here again the heat transfer rate is not sufficiently high due to comparatively low fluid velocities. An object of this invention is to provide an improved cold plate device which eliminates the disadvantages of the prior art devices. Another object of the invention is to provide an improved cold plate device which improves the heat transfer rate of cooling fluid. Yet another object of the invention is to provide an improved cold plate device which comprises flow-passages to improve flow-velocity of the cooling medium there through. Still another object of the invention is to provide an improved cold plate device which requires bonding of the base plate and the top plate eliminating thereby additional bonding of the flow-passages comprising of tubes or fins. Still yet another object of the invention is to provide an improved cold plate device which is easy to manufacture, cost-effective and designed to have in- built machine grooved flow-passages in registration with disposition of electronic components having varied heat transfer rate thereby achieving improved cooling effect. SUMMARY OF THE INVENTION Accordingly there is provided an improved cold plate device adaptable for cooling electronic components-mounted-over the external surface of the device, comprising a - base plate; a cover plate; a clad sheet sandwitched between the base plate and the cover plate by means of vacuum brazing; atleast one inlet port and atleast one outlet port configured at one end and/or opposite ends the of device for fluid entry and exit. A plurality of fluid passages consutituting of several grooves parallely disposed or a parallel- series combination on the base plate being configured for fluid-flow thereby maintaining an optimum flow-velocity and improved heat transfer. BFIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS Fig - 1 shows the base plate component of the device with flow passages. Fig - 2 shows the base plate component of the device with cross section of the flow passages. Fig - 3 shows a pre-assembled view of the improved cold plate device according to an embodiment of the present invention. Fig - 4 shows the temperature sensor locations of the assembled device of the invention. ( Fig 4. It is not part of the component, and used for testing the plate for performance evaluation. May also be deleted, if not needed.) Fig - 5 shows a table containing temperature profile of the electronic components mounted on the device of the invention. DETAIL DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION The Cold Plate constitutes a heat exchange means to cool the electronic components accommodated on the surface of the device. The fluid flow passages are configured by machining grooves on one of the components of the cold plate device so as to maintain the required heat transfer rates. The main variables available in designing the flow path configuration are: • Length of the passage • Width of the passage • Depth of the passage • Number of parallel flow paths. The cooling of a typical electronic component which has a heat load of 500 W in an area of 160mm by 500mm can be achieved by using the Cold Plate having machined grooves. The preferable material of construction is aluminum. The Cold Plate device has essentially three major components, a base plate (1) where the fluid passages (4) are grooved, a clad sheet (2) to effect the vacuum brazing and a cover plate (3). The thickness of the base plate (1) can preferably be selected between 5 to 10mm, more preferably between 7 to 9mm. The clad sheet (2) is selected to have a thickness ranging between 0.3mm to 0.6mm. The thickness of the cover plate (3) is selected in registration with the selected thickness of the base plate (1) and preferably ranges between 1.5mm to 3.5mm. The fluid passages constitute parallely disposed machined grooves (4). Machining of the parallel grooves (4) on the base plate (1) is preferably accomplished by using a Numerically Controlled (NC) machine or by a precision milling machine. The flow paths comprising the grooves (4) are of 3 mm to 6mm deep and preferably has a width between 4 to 7mm. The width of the solid portion of the base plate (1) between two adjacent passages are of 2.5mm to 5.00 mm with a centre and edge walls of 12 to 18mm thick. The flow passages (4) are parallelely configured having atleast one U-bend, so as to make the inlet (5) and outlets (6) of the fluid at the same end of the Cold Plate. The flow passages (4) are designed to atleast maintain intermittent solid areas with mounting holes (7) on the base plate (1) so that the mounting of the electronic components is enabled. The inlet (5) and the outlet (6) areas are provided with rectangular chambers having a plurality of nozzles (not shown) for fluid entry and exit. The bottom plate (1) is covered with top plate (3) keeping a clad plate (2) in between. They are brazed together (A,B,C) in a vacuum brazing furnace. The vacuum brazing process is an established process for aluminum-based materials. A typical Cold Plate device manufactured based on the described parameters has been tested with a fluid flow rate between 6 to 10 liters per minute. The temperature profile based on a selected heat load (8) has been evaluated after mounting the electronic components on the cold plate device. Typical test results are given in fig - 5. In an embodiment the inlet and outlet ports (5, 6) may be arranged in the horizontal direction by having a straight fluid passage from the rectangular chamber. In an alternative embodiment the inlet and outlet ports (5, 6) with fluid chambers are provided at two extreme ends of the Cold Plate device and making all the flow paths (4) parallel to each other without any U-bends. It is to be understood that the present invention is by no means limited only to the particular embodiments herein disclosed and shown in the accompanying drawings, but also includes any modifications or equivalents within the scope of the invention. WE CLAIM: 1. Cold plate with machine grooved flow passages for cooling electronic components mounted over the external surface of the device, comprising a base plate (1); a cover plate (3); a clad sheet (2) sandwitched between the base plate (1) and the cover plate (3) by means of vacuum brazing; atleast one inlet port (5) and atleast one outlet port (6) configured at one end and/or opposite ends of the device for fluid entry and exit, characterized in that a plurality of fluid passages constituting of several grooves (4) parallely disposed on the base plate (1) being configured for fluid-flow thereby maintaining an optimum flow-velocity and an improved heat transfer. 2. The device as claimed in claim 1, wherein the grooves (4) constitute machined grooves configured by means of a precision milling machine, preferably a numerically controlled machine. 3. The device as claimed in claim 1, wherein the plurality of flow- passages (4) are designed on the base plate (1) in such way that the electronic components can be accommodated in a plurality of mounting holes (7) provided in several intermittent solid areas of the base plate (1). 4. The device as claimed in claim 1 or 2, wherein the interconnections between the grooves (4) comprises one of a parallel and series flow path. 5. The device as claimed in claim 1, wherein the cooling fluid is selected from the group comprising air, vapour, oil, water glycol mixture, silicone based liquid and flurocarbon. 6. The device as claimed in claim 1, wherein the base plate (1) and the cover plate (3) comprise metallic material selected from a group constituting aluminium, aluminium alloy, copper, copper alloy and steel. 7. An improved cold plate device adaptable for cooling electronic components mounted over the external surface of the device as herein described and illustrated with accompanying drawings. Cold plate with machine grooved flow passages for cooling electronic components mounted over the external surface of the device, comprising a base plate (1); a cover plate (3); a clad sheet (2) sandwitched between the base plate (1) and the cover plate (3) by means of vacuum brazing; atleast one inlet port (5) and atleast one outlet port (6) configured at one end and/or opposite ends of the device for fluid entry and exit, characterized in that a plurality of fluid passages constituting of several grooves (4) parallely disposed on the base plate (1) being configured for fluid-flow thereby maintaining an optimum flow-velocity and an improved heat transfer

Documents:

00214-kol-2005-abstract.pdf

00214-kol-2005-claims.pdf

00214-kol-2005-correspondence-1.1.pdf

00214-kol-2005-correspondence.pdf

00214-kol-2005-description(complete).pdf

00214-kol-2005-drawings.pdf

00214-kol-2005-form-1.pdf

00214-kol-2005-form-18.pdf

00214-kol-2005-form-2.pdf

00214-kol-2005-form-3.pdf

214-KOL-2005-FORM-27-1.pdf

214-KOL-2005-FORM-27.pdf

214-kol-2005-granted-abstract.pdf

214-kol-2005-granted-claims.pdf

214-kol-2005-granted-correspondence.pdf

214-kol-2005-granted-description (complete).pdf

214-kol-2005-granted-drawings.pdf

214-kol-2005-granted-examination report.pdf

214-kol-2005-granted-form 1.pdf

214-kol-2005-granted-form 18.pdf

214-kol-2005-granted-form 2.pdf

214-kol-2005-granted-form 3.pdf

214-kol-2005-granted-form 5.pdf

214-kol-2005-granted-gpa.pdf

214-kol-2005-granted-reply to examination report.pdf

214-kol-2005-granted-specification.pdf