Partable Thermal Heat Pipe
A heat pipe for conducting heat away from an electronic device attached to a removable electronic module includes two self-aligning sections. A source section is attached to the removable electronic module and a target section passes through and is retained by a fixed member. One end of the source section is in thermal contact with a heat source and the other end includes a self aligning female thermal interface. One end of the target section includes a self aligning male thermal interface and the other end includes a heat sink. The female end of the source section and the male end of the target section are moved into contact with each other to form a thermal connection that permits heat from the heat source to be transferred to the heat sink.
This application claims priority to U.S. Patent Application No. 61/200,717 filed Dec. 3, 2008, which application is incorporated herein by references in its entirety.
BACKGROUND1. Field of the Invention
The present disclosure relates generally to thermal management, and more particularly to devices and methods for transferring heat from a removable module within a chassis.
2. Description of Related Art
High-performance semiconductor devices sometimes produce more waste heat than can be carried away from the device package by thermal radiation, conduction, and/or convection across the device package. Cooling problems may arise due to the power density of the device relative to its cooled surface area, difficulty in providing sufficient coolant flow across the device, and/or due to difficulty in providing a sufficiently large temperature differential between the device package and the coolant flowing across the device. Coolant temperature problems may arise due to the ambient temperature in which a system operates, and/or due to heating of the coolant flow prior to the coolant reaching the device package. Problematic device packages can be fitted with heat sinks and/or secondary cooling fans to assist in removing waste heat.
In some systems, spacing and packaging constraints and or local airflow/air temperature conditions prevent the successful application of a heat sink and/or secondary cooling fan directly to a semiconductor package. In such cases, a thermally conductive “heat pipe” can be fitted to the device package and used to draw heat away from the device package to a remote location. One end of the heat pipe maintains thermal contact with the device package to be cooled; the opposite end of the heat pipe is kept at a lower temperature, e.g., by immersing the second end in a relatively cool fluid stream. The temperature differential between the ends of the heat pipe draws heat away from the device to be cooled.
One difficulty with heat pipes arises when a device to be cooled by the heat pipe is built into a removable module, and the cooling fluid stream used by the heat pipe is located outside the module. In such cases, it may be difficult or even undesirable to design the heat pipe in a way that allows extraction of the heat pipe from the fluid stream and/or system when the module is removed from the system.
The present invention can be best understood by reading the specification with reference to the following Figures, in which:
It has now been discovered that prior art partable heat pipes contain several disadvantageous design features. First, the mating faces on the heat pipe section contact plates must be flat and perfectly parallel in order to maintain effective thermal contact between the two heat pipe sections. Slight misalignments between the two contact plates may sharply curtail the contact area and consequently the heat transfer capability of the heat pipe. Second, the “fully inserted” position of a module containing heat pipe section 120 is determined by the full contact position of the contact plates. In a system that mates electrical connectors through the same insertion sequence that causes contact between the heat pipe contact plates, the full mating of the electrical connectors can be critical to system operation. Thus electrical connectors and heat pipe sections must be critically aligned on both the module and the fixed portion of the system, or else at least one of the electrical and thermal connections will suffer. Third, the contact faces may require a large surface area to lower the thermal impedance of an imperfect (or even perfect) contact position, defeating miniaturization gains elsewhere in the system. Finally, the thermal grease present on the face of the contact plate 122 is subject to contact by a user when a module containing heat pipe 120 is removed from system 100. Not only may the user inadvertently spread thermal grease in places other than that desired, causing annoyance to the user, but the user may inadvertently or purposely remove the grease that is critical to the thermal interface function.
The present disclosure includes low-profile, self-aligning partable heat pipe embodiments that generally can be used to overcome the deficiencies noted above.
Heat transfer between the source heat pipe and the target heat pipe occurs at a partable conical or wedge shaped interface. Source heat pipe 250 includes a female interface element 252 in the form of a hollow cone or wedge with a conical or wedge-shaped inner cavity surface 260. Target heat pipe 230 includes a male interface element 232 in the form of a solid cone or wedge having the same release angle as the inner cavity surface 260. When the source and target heat pipes are brought together (see
Several advantages accrue from the use of a cone or wedge interface between the two heat pipes. Depending on the release angle selected (angles between 0.5 degrees and 45 degrees are preferred), the wedge interface can have a substantially lower profile than the flat face interface of the prior art. When combined with the articulation and spring-loading features described below, the wedge interface is also substantially self-aligning due to the complementary forces exerted by the cone or wedge faces. Thermal expansion of the receptacle, if greater than that of the wedge 232 due to higher temperature, merely causes a repositioning of the wedge in the receptacle, but does not decrease the contact area between the wedge and the receptacle or cause the wedge to stick in the receptacle. Thermal grease can be applied to both inner cavity surface 260 and wedge 232. The thermal grease inside receptacle 252 is inaccessible to the user when module 240 is removed from the system (at least for small cavity openings).
Carrier 220 is positioned with respect to an aperture 216, through which target heat pipe 230 passes, in fixed member 210. Carrier positioning nominally aligns target heat pipe 230 with the insertion direction 280 of module 240. A grommet or gasket 222 further positions heat pipe 230 within aperture 216, while providing some environmental sealing between the two sides of fixed member 210, if so desired. Grommet 222 allows target heat pipe 230 to translate along the insertion direction 280, and may also flex to allow minor translation of heat pipe 230 perpendicular to the insertion direction and/or to allow small angular variations in the alignment of target heat pipe 230. Carrier 220 also holds target heat pipe with a relatively loose tolerance that allows the translation and angular variations in the positioning of target heat pipe 230 with respect to fixed member 210.
Heat pipe 230 is spring-loaded to control the holding force between the target heat pipe 230 and source heat pipe 250 over a range of module 240 positions. In
The inner cavity surface 260 and wedge 232 are designed with a desired number of contact surfaces.
One use for embodiment 700 is to provide cooling for a compact form-factor electro-optic module that provides network connectivity to a computer, router, switch, etc. Such modules typically contain semiconductor lasers and drivers, receivers, and interface electronics in a small module package. The module can generate a substantial amount of waste heat, but the heat may be difficult to remove due to interference from the cage that holds the module and/or close proximity to similar modules that impede airflow.
Interface card 930 includes a substrate that is or includes a printed circuit board. A module cage 932, fixed to the printed circuit board, includes electrical connectors for providing signal/power connectivity between module 910 and supporting electronics on card 930. The module cage 932 also provides mechanical features to engage and hold module 910 when the module is inserted in the cage.
A target heat pipe 940 includes a heat transfer wedge 942, coated in thermal grease, integral cooling fins, and a spring/support 944. Spring support 944 fixes to card 930 at a position behind cage 932, such that the heat transfer wedge is cantilevered over the cage 932 in nominal alignment with the inserted position of source heat pipe 920.
Those skilled in the art will appreciate that the embodiments and/or various features of the embodiments can be combined in other ways than those described. For instance, although spring/support 944 is shown connected directly to a horizontal circuit board, the support can alternately connect to a vertical member or to an integral portion of the module cage. Various other locations for a spring means are possible and comprehended as within the scope of the disclosure. Other variations on the number of wedge contact surfaces are possible. The release angles of each surface need not be the same. The wedge need not come to a point. The source heat pipe may also comprise cooling and/or heat capture fins.
Although the specification may refer to “an”, “one”, “another”, or “some” embodiment(s) in several locations, this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment.
Claims
1. A self-aligning partable heat pipe comprising:
- a source section attached to a removable electronic module, the distal end of the source section in thermal contact with a heat source and the proximal end of the source section forming a female interface element;
- a target section passes through and is retained by both of an aperture in a fixed member and an aperture in a carrier member and is able to translate towards and away from an insertion direction of the removable electronic module, and the target section includes a thermal target and a proximal end of the target section forms a male interface element; and
- the female interface element of the source section and the male interface element of the target section together comprise a partable, self-aligning thermally conductive interface through which heat from the heat source is transferred to the thermal target.
2. The thermally conductive interface of claim 1, wherein the female interface element is comprised of a hollow wedge shaped receptacle and the male interface element is comprised of a solid wedge that fits inside the hollow wedge shaped receptacle of the female interface element.
3. The female interface element of claim 2, wherein the hollow wedge shaped receptacle is comprised of an inner cavity surface and the sides are wedge shaped.
4. The male interface element of claim 2, wherein the wedge is a two-sided wedge and the width of the wedge is smaller than the opening in the female interface element.
5. The wedge shaped form of claim 4, wherein the sides of the wedge are wedge-shaped.
6. The female interface element of claim 2, wherein the wedge is conical.
7. The male interface element of claim 2, wherein the wedge is conical.
8. The partable heat pipe of claim 1, wherein the removable electronic module is a printer circuit board.
9. The partable heat pipe of claim 1, wherein the heat source is an electronic device.
10. The partable heat pipe of claim 1, wherein the fixed member is any one of a bulkhead, other chassis member, electrical backplane, circuit board and second module.
11. The partable heat pipe of claim 1, wherein the carrier member is fastened to the fixed member.
12. The partable heat pipe of claim 1, wherein the thermal target is a thermal radiator.
13. The partable heat pipe of claim 1, wherein the target section is spring loaded.
14. The hollow wedge shaped receptacle of claim 3, wherein the inner cavity surface is coated with thermal grease.
Type: Application
Filed: Dec 2, 2009
Publication Date: Jun 3, 2010
Inventor: Donald Carson Lewis (Richmond, CA)
Application Number: 12/629,822
International Classification: F28D 15/02 (20060101);