WO2009072698A1

WO2009072698A1 - The flat plate type micro heat spreading device

Info

Publication number: WO2009072698A1
Application number: PCT/KR2008/001811
Authority: WO
Inventors: Seok Hwan Moon; Gunn Hwang
Original assignee: Electronics And Telecommunications Research Institute
Priority date: 2007-12-06
Filing date: 2008-04-01
Publication date: 2009-06-11
Also published as: KR100917599B1; KR20090059449A; US20100258278A1

Abstract

A flat plate type heat spreading device is provided. The flat plat type heat spreading device can reduce heat by generating phase transition of liquid by using heat of a heat source so as to solve various problems caused by heat generated in components of electronic devices such as personal computers or mobile phones. Specifically, the flat plate type heat spreading device includes a lower plate for evaporating liquid, a middle plate combined with an upper surface of the lower plate, which separately includes a path through which evaporated vapor passes and a path through which condensed fluid flows into the lower plate, and an upper plate combined with an upper surface of the middle plate, which condenses the evaporated vapor.

Description

Description THE FLAT PLATE TYPE MICRO HEAT SPREADING DEVICE

Technical Field

[1] The present invention relates to a flat plate type heat spreading device, and more particularly, to a device capable of reducing heat by inducing phase transition of liquid by using heat of a heat source so as to solve various problems caused by heat generated in components of electronic devices such as personal computers (PCs) or mobile phones.

[2] Specifically, the present invention relates to a flat plate type heat spreading device capable of evaporating operating fluid injected into a closed space by using a heat source and dissipating the heat through a procedure of condensing the evaporated vapor, again. Background Art

[3] As the latest technique has been developed, it is impossible to ignore heat emitted by

CPUs (central processing units) as performance of personal computers (PCs) has been increased and as a degree of packaging integration has been increased. In addition, this problem on heat is not limited to CPUs. This is because the latest fabrication technique used for the CPUs of the PCs tends to be used for other electronic products. Typically, if performance of mobile phones that require a more highly integrated design than the PCs has been developed at a current development speed, the heat problem may become serious.

[4] At present, the mobile phones have been developed so as to provide a data service such as a color display service, a multimedia service, a video on demand (VOD) service, a video phone service, a mobile game service, and the like. Accordingly, an amount of data to be processed in a system is increased. As a result, an amount of heat generated in the system is expected to increase.

[5] Accordingly, a heat spreading technique for compact devices has to be developed so as to secure stability of the mobile phones. In addition, since mobility of the mobiles phones is an important factor, the technique has to be developed in consideration of a light weight and a small size of the mobile phones.

[6] Accordingly, in order to efficiently process heat generated in this environment, a heat spreading device is required to be developed in addition to a heat transfer device. Heating parts in electronic devices may have a hot spot type with a relatively small area. It is impossible to efficiently spread the heat only by attaching a heat sink for spreading the heat and a cooling device for transferring heat. A heat spreading device for reducing heat flow resistance due to a sharp increase in a heat transfer area from a small area of the hot spot to a relatively large area is required. [7] In case of a solid material with high thermal conductivity which is generally used as the heat spreading device has a limit in performance. In a range of high heat flux, a difference in temperature between hot and cold junctions increases. Recently, although a solid material of which heat transfer coefficient is largely improved may be used, this also has a limit in heat performance. Unlike the solid material, a heat pipe method is frequently considered as the heat spreading device. Since heat pipes have a high heat performance and low costs, usability of the heat pipes is high.

[8] However, in spite of high heat performance of the heat pipes, if there is no space available for the heat pipes in a small electronic package structure, the heat pipes have to be manufactured with a small and thin shape. In this case, although heat pipes with a circular type may be compressed and used, if the heat pipes are not initially designed with a thin shape, the heat performance is largely reduced. Disclosure of Invention Technical Problem

[9] Accordingly, a heat spreading device capable of spreading heat generated in an electronic device such as a personal computer (PC) and a mobile phone with high performance is necessary. In addition, as the electronic device such as the PC and the mobile phone has been miniaturized, a heat spreading device with a small size, a light weight, and a simple structure is required to be developed. Technical Solution

[10] According to an aspect of the present invention, there is provided a flat plate type heat spreading device comprising: a lower plate evaporating liquid; a middle plate combined with an upper surface of the lower plate, which separately includes a path through which evaporated vapor passes and a path through which condensed fluid flows into the lower plate; and an upper plate combined with an upper surface of the middle plate, which condenses the evaporated vapor.

[11] According to another aspect of the present invention, there is provided a flat plate type heat spreading device comprising: a lower plate having a step difference between a center part and edges thereof, in which a multi-channel capillary structure constructed with unidirectional grooves is formed so as to evaporate liquid by using heat of a heat source located under the lower plate; a middle plate combined with an upper surface of the lower plate, in which a path through which evaporated vapor passes is formed at a position corresponding to the center part of the upper surface of the lower plate, and a liquid flow path through which condensed liquid flows into the lower plate is formed at a position corresponding to edges of the lower plate in a direction perpendicular to the unidirectional grooves; an upper plate combined with an upper surface of the middle plate, in which a multi-channel capillary structure constructed with unidirectional grooves is formed on a lower surface, and liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to the liquid flow path.

[12] According to another aspect of the present invention, there is provided a flat plate type heat spreading device comprising: a lower plate having a step difference between a center part and edges thereof, in which a multi-channel capillary structure constructed with unidirectional grooves is formed so as to evaporate liquid by using heat of a heat source of a lower surface of the lower plate; and an upper plate combined with an upper surface of the low plate, in which a multi-channel capillary structure constructed with unidirectional grooves is formed on a lower surface, and liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to edges of the lower plate.

[13] According to another aspect of the present invention, there is provided a flat plate type heat spreading device comprising: a lower plate evaporating liquid by using heat of a heat source of a lower surface, in which a multi-channel capillary structure constructed with unidirectional grooves is formed in edges of an upper surface; a middle plate combined with the upper surface of the lower plate, in which a path through which vapor evaporated in the lower plate passes is formed, a liquid flow path through which condensed liquid flows into the lower plate is formed at a center part in a direction perpendicular to the unidirectional grooves; and an upper plate combined with the middle plate, in which a multi-channel capillary structure constructed with unidirectional grooves is formed on a lower surface, liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to the liquid flow path.

Advantageous Effects

[14] As described above, since the flat plate type heat spreading device according to an embodiment of the present invention is constructed with a multi-channel capillary structure in which edges of a cross section of grooves of upper and lower plates are sharply formed, capillary force is largely improved, thereby activating a circulation procedure of evaporation and condensation.

[15] In addition, the flat plate type heat spreading device according to an embodiment of the present invention can prevent a back flow of vapor bubbles without another structure by using a two-step capillary structure of a lower plate and remove a probability of compression generated in a vacuum state by using bridges formed in upper, middle, and lower plates.

[16] In addition, since the flat plate type heat spreading device can adjust a size thereof, if necessary, the flat plate type heat spreading device can be applied to various fields. Brief Description of the Drawings

[17] FIG. 1 is a flat plate type heat spreading device according to a first embodiment of the present invention.

[18] FIG. 2 is a flat plate type heat spreading device according to a second embodiment of the present invention.

[19] FIG. 3 is a flat plate type heat spreading device according to a third embodiment of the present invention.

[20] FIG. 4 is a flat plate type heat spreading device according to a fourth embodiment of the present invention.

[21] FIG. 5 is a flat plate type heat spreading device according to a fifth embodiment of the present invention. Best Mode for Carrying Out the Invention

[22] The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the description of the present invention, if it is determined that a detailed description of commonly-used technologies or structures related to the invention may unnecessarily obscure the subject matter of the invention, the detailed description will be omitted.

[23] Like reference numerals designate like elements throughout the specification.

[24] FIG. 1 is a flat plate type heat spreading device according to a first embodiment of the present invention.

[25] The flat plate type heat spreading device according to the embodiment is constructed by combining an upper plate 100, a middle plate 200, and a lower plate 300 with one another so as to form a closed structure. An operating fluid is injected into the closed heat spreading device. Heat is exchanged between an evaporation part of the lower plate 300 and a condensation part of the upper plate 100 through a heat transfer method through phase transition.

[26] Specifically, the lower plate 300 evaporates the operating fluid (hereinafter, referred to as liquid) by using heat transferred from a heat source. The evaporated vapor is transmitted to the upper plate 100 through a vapor flow path 210 formed in the middle plate 200. The evaporated vapor is condensed into liquid in the upper plate 100 and transmitted to the lower plate 300 again, so as to dissipate heat of the heat source to the outside of the upper plate 100. Detailed description on components which performs the aforementioned processes will be described, in heat transfer order.

[27] An evaporation space is formed on an upper surface of the lower plate 300 so that the liquid is uniformly distributed and easily evaporated. Here, the evaporation space is a spatial concept of the evaporation part for evaporating the liquid. The evaporation space is formed by forming an empty space with a predetermined dept except edges of the lower plate 300. In the evaporation space, the liquid is evaporated by using heat transferred from the heat source.

[28] A bridge for preventing compression due to vacuum is formed in the evaporation space. The bridge is formed with a structure for connecting edges in both sides to each other. Specifically, a center part of the upper surface of the lower plate 300 is formed by using a pushing method. Grooves of a multi-channel capillary structure are fabricated by using a laser.

[29] In addition, the multi-channel capillary structure constructed with a plurality of grooves is formed in the evaporation space. The multi-channel capillary structure can improve a capillary force for returning the liquid to the evaporation part. Here, the grooves are unidirectionally formed. A cross section of the grooves may be a circle or a polygon such as a triangle, a quadrangle. The plurality of grooves may be disposed at a predetermined interval or disposed without a predetermined interval. However, the interval of the grooves may be small so as to increase the capillary force.

[30] In addition, the multi-channel capillary structure may have at least one step difference. FIG. 1 illustrates two-step multi-channel capillary structure in the evaporation space according to the embodiment of the present invention. The two-step structure is constructed with upper and lower end parts 320 and 310. Edge parts of the evaporation space are higher than the center part of the evaporation space. Here, each groove extends from the upper end part to the lower end part. The liquid flow path of the middle plate 200 is disposed on the upper surface of the upper end part 320. As a result, the liquid that is transferred to the lower plate 300 again through the liquid flow path 220 is transferred to the lower end part 310 along the upper end part 320. Finally, the liquid is uniformly spread over the entire area of the evaporation part. The two-step capillary structure has an effect of preventing a back flow of the vapor. Accordingly, an additional structure is not needed.

[31] The middle plate 200 enables the vapor and the liquid to be passed between the lower and upper plates 300 and 100. In the middle plate 200, the vapor flow path 210 for passing the evaporated vapor is formed at a position corresponding to the lower end part 310 of the evaporation space of the lower plate 300, and the liquid flow path 220 for passing the condensed liquid is formed at a position corresponding to the upper end part 320 of the evaporation space. In addition, a bridge 230 is formed at a position corresponding to bridges of the lower and upper plates 300 and 100. The middle plate 200 supports the upper plate 100 and enables the upper plate 100 to be spaced apart from the lower plate 300. In some cases, the upper or lower plate 100 or 300 can perform the function of the middle plate 200. [32] The upper plate 100 condenses the vapor evaporated in the lower plate 300. A lower surface of the upper plate 100 has a multi-channel capillary structure constructed with unidirectionally formed grooves like the lower plate 300. The vapor is condensed in a space in which the capillary structure is formed. The space is referred to as a condensation part. The multi-channel capillary structure enables the condensed liquid to flow fast.

[33] In addition, liquid collection grooves 120 are formed on both sides of the condensation part of the upper plate 100 in a direction perpendicular to the direction of the plurality of grooves. Accordingly, the liquid condensed in the multi-channel capillary structure is collected into the liquid collection grooves 120. The collected liquid is transferred to the lower plate 300 through the liquid flow path 220 of the middle plate 200. However, like the lower plate 300, a cross section of the grooves 120 formed in the upper plate 100 may be a circle or a polygon such as a triangle, a quadrangle, and the like.

[34] The flat plate type heat spreading device according to the embodiment is constructed with the upper plate 100, the middle plate 200, and the lower plate 300 so as to form the closed structure. An inlet for injecting the operating fluid into at least one of the upper, middle, and lower plates 100 to 300 is formed so as to inject the operating fluid into the closed space.

[35] In addition, although the structure constructed by combining the upper, middle, and lower plates 100 to 300 with one another is described with reference to FIG. 1, the structure may be constructed by directly combining the upper and lower plates 100 and 300 with each other.

[36] The heat spreading device according to the embodiment serves to reduce heat from the heat source through the following procedures. The heat that is transferred from the heat source to the lower plate 300 is transformed into latent heat by evaporating the liquid. The latent heat is transferred to the upper plate 100 through the vapor flow path 210 of the middle plate 200. The transferred vapor is condensed by the condensation part of the upper plate 100 by emitting heat. Finally, the condensed liquid is transferred to the lower plate 300 again through the liquid flow path 220. The heat of the heat source is dissipated to the outside of the upper plate 100 through a circulation procedure with a loop type.

[37] FIG. 2 is a flat plate type heat spreading device according to a second embodiment of the present invention.

[38] FIG. 2 illustrates a structure constructed with the upper, middle, and lower plates 100 to 300 with one another so as to form a closed structure, like the heat spreading device of FIG. 1. The operating fluid is injected into the heat spreading device with the closed structure. As described in FIG. 1, heat is exchanged between the evaporation part of the lower plate 300 and the condensation part of the upper plate 100 through a heat transfer process based on phase transition.

[39] However, in FIG.2, two orthogonal bridges for preventing compression in a vacuum state are formed instead of a single bridge. That is, two orthogonal bridges are formed in the evaporation space of the lower plate 300. In the upper and middle plates 100 and 200, two orthogonal bridges are also formed at a position corresponding to the two orthogonal bridges of the lower plate 300.

[40] FIG. 3 is a flat plate type heat spreading device according to a third embodiment of the present invention.

[41] In FIG. 3, heat of the heat source is dissipated to the outside of the upper plate through the same procedure as the procedure of FIG. 1. However, the capillary structures of the upper and lower plate 100 and 200 are constructed with unidirectional grooves and new grooves perpendicular to the unidirectional grooves instead of unidirectional grooves.

[42] Accordingly, in the upper plate 100, two liquid collection grooves 120 for collecting the condensed liquid are further formed in a direction perpendicular to the new grooves. Accordingly, in FIG. 2, the condensed liquid is collected into the liquid collection grooves formed on both sides of the upper plate.

[43] In addition, in the middle plate 200, the liquid flow paths 220 are additionally formed at positions corresponding to the liquid collection grooves. In the lower plate 320, upper end parts with a two-step structure are further formed.

[44] FIG. 4 is a flat plate type heat spreading device according to a fourth embodiment of the present invention.

[45] FIG. 4 illustrates the embodiment in which a structure for performing a capillary function instead of the capillary grooves of the lower plate 300 is inserted in the lower plate 300.

[46] Here, the inserted structure has a wick type. Accordingly, a relatively fine sintered wick is formed on a part that directly contacts a bottom of the lower plate. In the upper plate, a coarse sintered wick is formed.

[47] FIG. 5 is a flat plate type heat spreading device according to a fifth embodiment of the present invention.

[48] Unlike the aforementioned embodiments, in FIG. 5, the liquid collection grooves 120 of the upper plate 100, the liquid flow path 220 of the middle plate 200, and an upper end part with a capillary structure in the lower plate 230 are unidirectionally formed not in the sides but in the central part of the upper, middle, and lower plates, respectively.

[49] Accordingly, the liquid transferred from the upper plate 100 to the lower late 300 is spread over the grooves with the capillary structure in both sides from the upper end part 320 of the lower plate 300 and evaporated.

[50] Then, the evaporated vapor is condensed by the upper plate 100 and collected to the liquid collection groove 120. In addition, in the middle plate 200, a liquid flow path for enabling the liquid to flow through a position corresponding to the liquid collection groove 120 and the upper end part of the lower plate 300.

[51] While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

[I] A flat plate type heat spreading device comprising: a lower plate evaporating liquid; a middle plate combined with an upper surface of the lower plate, which separately includes a path through which evaporated vapor passes and a path through which condensed fluid flows into the lower plate; and an upper plate combined with an upper surface of the middle plate, which condenses the evaporated vapor. [2] The flat plate type heat spreading device of claim 1, wherein the lower plate has a multi-channel capillary structure constructed with grooves. [3] The flat plate type heat spreading device of claim 2, wherein the multi-channel capillary structure has at least one step difference. [4] The flat plate type heat spreading device of claim 3, wherein in the lower plate, a bridge for preventing compression due to vacuum is formed at a center part of the lower plate. [5] The flat plate type heat spreading device of claim 1, wherein the upper plate has a multi-channel capillary structure constructed with grooves. [6] The flat plate type heat spreading device of claim 5, wherein in the upper plate, liquid collection grooves in which liquid condensed by the multi-channel capillary structure constructed with the grooves is collected are formed. [7] The flat plate type heat spreading device of claim 6, wherein in the middle plate, paths through which the fluid flows are formed at positions corresponding to the liquid collection grooves. [8] The flat plate type heat spreading device of claim 7, wherein in the lower plate, the bridge for preventing compression is formed, and wherein the middle and upper plates respectively include a bridge at a position corresponding to the bridge. [9] The flat plate type heat spreading device of claim 1, which is closed and evacuated. [10] The flat plate type heat spreading device of claim 1, wherein the upper surface of the lower plate is constructed with at least one of a sintered wick, a fiber wick, a screen mesh wick, a fine fiber wick, and a woven wire wick.

[I I] A flat plate type heat spreading device comprising: a lower plate having a step difference between a center part and edges thereof, in which a multi-channel capillary structure constructed with unidirectional grooves is formed so as to evaporate liquid by using heat of a heat source located under the lower plate; a middle plate combined with an upper surface of the lower plate, in which a path through which evaporated vapor passes is formed at a position corresponding to the center part of the upper surface of the lower plate, and a liquid flow path through which condensed liquid flows into the lower plate is formed; and an upper plate combined with an upper surface of the middle plate, in which a multi-channel capillary structure constructed with unidirectional grooves is formed on a lower surface, and liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to the liquid flow path.

[12] The flat plate type heat spreading device of claim 11, wherein in the lower plate, a bridge for preventing compression is formed at a center part of the lower plate, and wherein the middle and upper plates respectively include a bridge at a position corresponding to the bridge.

[13] The flat plate type heat spreading device of claim 12, wherein grooves of the lower and upper plates are further formed in a direction perpendicular to the unidirectional grooves.

[14] The flat plate type heat spreading device of claim 13, wherein the upper plate further includes liquid collection grooves perpendicular to the further formed grooves, and wherein the middle plate further includes liquid flow paths at a position corresponding to the liquid collection grooves.

[15] The flat plate type heat spreading device of claim 11, wherein an interval of the grooves of the lower plate is smaller than that of the grooves of the upper plate.

[16] The flat plate type heat spreading device of claim 11, wherein the grooves of the lower plate are formed to the positions corresponding to the liquid flow paths.

[17] The flat plate type heat spreading device of claim 11, wherein a center part of the upper surface of the lower plate is formed by using a pushing method, and wherein grooves of a multi-channel capillary structure are fabricated by using a laser.

[18] A flat plate type heat spreading device comprising: a lower plate having a step difference between a center part and edges thereof, in which a multi-channel capillary structure constructed with unidirectional grooves is formed so as to evaporate liquid by using heat of a heat source of a lower surface of the lower plate; and an upper plate combined with an upper surface of the low plate, in which a multi- channel capillary structure constructed with unidirectional grooves is formed on a lower surface, and liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to edges of the lower plate.

[19] The flat plate type heat spreading device of claim 18, wherein in the lower plate, a bridge for preventing compression is formed at a center part of the lower plate, and wherein in the upper plate, a bridge is formed at a position corresponding to the bridge of the lower plate.

[20] A flat plate type heat spreading device comprising: a lower plate evaporating liquid by using heat of a heat source of a lower surface, in which a multi-channel capillary structure constructed with unidirectional grooves is formed in edges of an upper surface; a middle plate combined with the upper surface of the lower plate, in which a path through which vapor evaporated in the lower plate passes is formed, a liquid flow path through which condensed liquid flows into the lower plate is formed at a center part in a direction perpendicular to the unidirectional grooves; and an upper plate combined with the middle plate, in which a multi-channel capillary structure constructed with unidirectional grooves is formed on a lower surface, liquid collection grooves through which condensed vapor is collected are formed in a direction perpendicular to the unidirectional grooves at a position corresponding to the liquid flow path.