US20050199376A1

US20050199376A1 - Heat sink

Info

Publication number: US20050199376A1
Application number: US11/007,192
Authority: US
Inventors: Yi-sheng Lee
Original assignee: Delta Electronics Inc
Current assignee: Delta Electronics Inc
Priority date: 2004-03-15
Filing date: 2004-12-09
Publication date: 2005-09-15
Also published as: US20060237167A1; TWM309091U; TW200530552A

Abstract

A heat sink including a main body and a plurality of porous structures is disclosed. The main body has a plurality of hollow fins and a base. The fins and the base form a closed room. The porous structures are set on the interior surfaces of different fins, and are connected to the base. Each porous structure defines a vapor chamber.

Description

BACKGROUND OF THE INVETION

a) Field of the Invention
The invention relates to a heat sink and, more particularly, to a heat sink that is able to dissipate heat quickly and efficiently.
b) Description of the Prior Art
With the advancement of electronic technology, the electronic components are miniaturized and densely packaged. However, this correspondingly produces more heat, and therefore relying on natural or forced convection is insufficient to remove heat.
The conventional method of removing heat generated from electronic components is to conduct the heat from a heat source to a heat sink and then to dissipate the heat to the surroundings through natural or forced convection to the fins of the heat sink. However, the conventional heat sinks with fins have some problems that do affect the efficiency of heat removal. For instance, a deficiency in temperature gradient due to the temperature difference between the fin surfaces and the heat sink airflow being only 5-10 degrees Celsius; the heat resistance problems due to the material and structure of the heat sink and low fin efficiency that is less than 70%. These problems are the root causes for the conventional heat sinks not able to increase its' heat dissipation efficiency and further unable to remove the heat produced by electronic components sufficiently.
Thus, U.S. Pat. No. 6,490,160 has disclosed a heat sink composed of a vapor chamber in view of the aforementioned problems. The concept of this patent is to form a single vapor chamber in a heat sink, wherein the top of the vapor chamber is composed of an array of sheet tapered hallow pins deeply mounted in the heat sink fins, and the bottom of the vapor chamber is a single chamber connected to the bottom of all sheet tapered hollow pins. The heat sink according to this patent dissipates heat by having a working fluid to absorb heat and to be vaporized to the hollow pins and then to be liquefied again after exchanging heat with the outer surroundings. After the condensation, the working fluid (liquid) flows along the groove wick structure on the surface of the hollow pins and returns to the chamber from the outer wall.
Nonetheless, the path for the working fluid to return to the chamber is long. Therefore, under a large heat-loading situation, there may be no condensed liquid (working fluid) in the vapor chamber and cause the chamber to dry out. In addition, the single phase state (only vapor) in the heat conductive mechanism and the long return path can make the fins except the outmost fins ineffective. Under this condition, the effective dissipating surface is greatly reduced and hence lowers the effectiveness of the heat sink.
Moreover, another heat sink with vapor chamber has been disclosed in U.S. patent application No. 2002/0118511. This patent application also forms a single vapor chamber in the heat sink, the chamber bottom is still a single chamber connected to all hollow pin except that a matrix arrangement of the columnar hollow pins is applied. This patent application utilizes a working fluid to absorb heat in the chamber and to be vaporized to the hollow pins. The vaporized working fluid then exchange heat with the surroundings and condenses, and then trickles down along the sidewall and back into the chamber due to gravity force. Since gravity is the return-flow mechanism used in this application, direction problems do exist. That is, when the installation direction of the heat sink changes, the return-flow mechanism becomes inoperable.
In regards to the foregoing statements, U.S. patent application 2002/0118511 also disclosed a method combining the two technologies by forming a porous structure inside the hollow fins, so that the working fluid can return to the chamber through the porous structure by capillary force. However, this technology did not solve the problem that exists in the U.S. Pat. No. 6,490,160, where the dry out occurs and all but the outmost hollow fins are inoperable under a high heat-loading condition, which lowers the dissipation efficiency.

SUMMARY OF THE INVENTION

To solve the abovementioned problems, the present invention discloses a heat sink with high heat dissipation efficiency under any heat loading.
An object of the invention is to provide a heat sink with high heat dissipation efficiency under high heat loadings.
Another object of the invention is to provide a heat sink with high heat dissipation efficiency when installed in any direction.
Yet another object of the invention is to provide a heat sink which prevents dry outs and hot spots from occurring.
The invention discloses a heat sink including a main body and a plurality of porous structures. The main body has a plurality of hollow fins and a base, the fins and the base form a closed room. The porous structures are set on the interior surfaces of a different fin and are connected to the base, and each porous structure defines a vapor chamber.
The invention also discloses a heat sink including a main body and a plurality of porous structures with the main body having a plurality of hollow protrusions and a base. The protrusions and the base form a closed room. The porous structures are set on the interior surfaces of a different protrusion and are connected to the base, and each porous structure defines a vapor chamber.
The porous structures are wick structures; common wick structures include mesh, fiber, sintered, groove wicks, or combinations thereof. The porous structures and the main body are assembled by methods such as sintering, adhering, filling, or depositing. The material of the porous structures includes plastics, alloys or metals such as copper, aluminum, iron, porous non-metallic materials and mixtures thereof. The porous structures contain a working fluid; the working fluid can be inorganic compounds, water, alcohols, liquid metals such as mercury, ketones, refrigerants such as HFC-134a, other organic compounds or mixtures thereof.
The main body can be one-piece molded or composed of several components. The components are bind together by soldering, engaging, embedding, adhering, or combinations thereof. Neighboring vapor chambers are communicated with each other directly, or indirectly in fluid communication through the porous structures.
The vapor chambers are arranged in the closed room either in an array arrangement, a longitudinal arrangement, a parallel arrangement, or a transverse arrangement.
Since the heat sink according to the invention utilizes wick structures (porous structures) to form several small vapor chambers and/or small sectors, the wick structure of every protrusion forms an independent heat-removal cycle. So, under high heat-loading situation, the dry outs will not occur and the high heat dissipation efficiency is maintained.
Moreover, since the bottom of the small vapor chambers and/or small sectors are composed of connecting wicks (heat-absorptive portion), the working fluid in each small vapor chamber are in fluid communication, and thus the possibility of hot spots occurring is lowered, and the heat is evenly distributed to each small vapor chamber and/or small sector.
Furthermore, since the return-flow mechanism of the heat sink according to the invention uses capillary force but not simply relies on gravity, the return-flow speed of the working fluid in the heat sink will not be affected by the direction for installation.
The vapor chamber in the heat sink according to the invention is composed of a plurality of small vapor chambers and/or small sectors, and therefore the return-flow path of the working fluid is short, and the return-flow speed and heat dissipation efficiency are enhanced.
The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a preferred embodiment of a heat sink in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a heat sink 100 includes a main body 102 and a plurality of porous structures 110 inside the main body 102, wherein the main body 102 has a closed room 124 formed therein.
The main body 102 has a plurality of hollow protrusions 120 and a base 122 connecting to a heat source 118. The shape and/or size of the base 122 varies in accordance with the placement of the protrusions 120 and the shape of the heat source 118. Each protrusion 120 is hollow and has two ends; the end proximate the base 122 has an opening and the other end is closed. The protrusions 120 are in a shape of fin, column, lamella, cone, or lump; and in a form of curve, arch, slant, vertical, or any other form. The protrusions 120 and the base 122 of the main body 102 can be one-piece molded or jointed by soldering, engaging, embedding, adhering, or a combination of any of the methods listed thereof. Moreover, the closed room 124 can be divided into a plurality of vapor chambers 112 by the porous structures 110.
The porous structures 110 are embedded on the interior surfaces of the main body 102, and are sealed therein. The porous structures 110 form a plurality of vapor chambers 112 in the main body 102. Each porous structure 110 is sectioned into two conductive portions, 104 and 106, and a heat-absorptive portion 108. The porous structures 110 are for absorbing working fluid; the condensed working fluid flows through the conductive portion 104, the conductive portion 106, and into the heat-absorptive portion 108. The working fluid is of inorganic compounds, water, alcohols, liquid metals such as mercury, ketones, refrigerants such as HFC-134a, other organic compounds, or a mixture of any of the fluids listed thereof. Using the pressure in the vapor chambers 112 can control the boiling temperature of the working fluid. The heat-absorptive portion 108 set on the interior surfaces of the base 122 is for absorbing the working fluid. The conductive portion 104 set on the interior surfaces of the protrusion 120 is for conducting the condensed working fluid to the heat-absorptive portion 108. The other conductive portion 106 is set between the heat-absorptive portion 108 and the conductive portion 104, and connected to both portions.
The conductive portions 104, 106 and the heat-absorptive portion 108 can be made of material such as copper, aluminum, iron, other metals and/or alloys, plastics, other porous non-metallic materials, or a mixture of any of the materials listed thereof. The conductive portions 104, 106 and the heat-absorptive portion 108 is required to have a porous formation such as wicking structures. Common wicking structures include mesh wicks, fiber wicks, sintered wicks, groove wicks, or other structures including a combination of any of the wicking structures listed thereof. The porous structures 110 and the main body 102 are assembled by sintering, adhering, filling, or depositing.
The conductive portion 106 is set between neighboring protrusions 120 so that the working fluid in the conductive portion 104 can flow quickly to the heat-absorptive section 108 along the conductive portion 106. The conductive portion 106 divides the closed room 124 into a plurality of vapor chambers 112; each vapor chamber 112 corresponds to at least one of the protrusions 120. The conductive portion 106 can also divide the closed room 124 into a plurality of sectors; the sectors each corresponds to a protrusion 120 and the neighboring sectors are communicated with each other. The vapor chambers 112 or the small sectors can be disposed in array, parallel, longitudinal, transverse, diagonal or irregular arrangements.
Although the closed room 124 has been divided into a plurality of vapor chambers 112 and/or small sectors by the conductive portions 106, the working fluid in the heat-absorptive portion 108 on the bottom of each vapor chamber is in fluid communication with other vapor chambers. Thus the occurred probability of the partial hot spots on the heat sink 100 is reduced, and the heat is distributed evenly on the bottom of the heat sink 100.
The heat sink 100 described above is used to illustrate the heat-removal mechanism used in the invention. In this embodiment, the base 122 of the heat sink 100 is installed on the heat source 118, wherein the heat source 118 is composed of a heat-generating element 116 and a conducting structure 114 connected to the heat-generating element 116. The conducting structure 114 can be a heat-dissipating paste, or a phase-changing metal sheet; the heat-generating element 116 can be a computer-processing unit (CPU), or a semi-conductor chip. For illustration purpose, the protrusions 120 exemplify a fin shape in this embodiment.
When the bottom of the vapor chambers 112 is heated and the temperature of the working fluid raises to the boiling point, the working fluid in the heat-absorptive portions 108 boils and evaporates, causing the pressure in the vapor chambers 112 to rise and the vapors move towards the fins quickly. The heat in the fins is then dissipated by natural or forced convection; the vapors condensate into liquid on the interior surfaces of the fins and the working fluid (liquid) penetrates into the conductive portions 104 (wick structure) in the fins. Since the heat-absorptive portions 108 (wick structure) are drier than the conductive portions 104, the capillary force drives the working fluid (liquid) to flow back to the bottom of the vapor chambers 112 and hence a heat-removal cycle is completed.
Since the bottom edges of the fins are connected to the base 122 with the conductive portions 106 (wick structure), the return-flow speed of the working fluid is enhanced and dry out is prevented from occurring.
Concluding from the description above, the heat sink according to the invention utilizes wick structures (porous structures) to form a plurality of small vapor chambers and/or small sectors, so that the wick structure in each protrusion forms an independent heat-removal cycle. Thus even under high heat-loading situations, dry outs caused by the lack of working fluid will not occur and the heat-dissipating effect can be maintained.
Moreover, the bottom of the small vapor chambers and/or small sectors are made of connecting wick structures (heat-absorptive portions), thereby the working fluid in each small vapor chamber and/or small sector is in fluid communication via the wick structures on the bottom. This in turn lowers the occurred probability of hot spots and the heat is evenly distributed to each small vapor chamber and/or small sector.
Furthermore, since the heat sink according to the invention utilizes capillary force in the return-flow mechanism instead of simply relying on gravity, thus the installation direction of the heat sink will not affect the return-flow speed.
In addition, since the vapor chamber of the heat sink according to the invention includes a plurality of small vapor chambers and/or small sectors, each small vapor chamber and/or small sector has shorter return-flow path than that of the conventional technology. Therefore, the return-flow speed of the working fluid is increased and the heat-dissipating effect is enhanced.
While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

1. A heat sink, comprising:

a main body having a plurality of hollow fins and a base, the fins and the base forming a closed room; and

a plurality of porous structures set respectively on the interior surfaces of the hollow fins and connected to the base, each porous structure defining a vapor chamber.

2. The heat sink as described in claim 1, wherein the fins are hollow and each fin has a close end and an open end facing the base.

3. The heat sink as described in claim 1, wherein the porous structures are wicks selected from the group consisting of a combination of one or more of mesh wicks, fiber wicks, sintered wicks, and groove wicks.

4. The heat sink as described in claim 1, wherein the porous structures contain a liquid selected from the group consisting of a mixture of one or more of inorganic compounds, water, alcohols, liquid metals, ketones, refrigerants, and organic compounds.

5. The heat sink as described in claim 1, wherein the material of the porous structures is selected from the group consisting of a mixture of one or more of plastics, metals, alloys, and porous non-metal materials.

6. The heat sink as described in claim 1, wherein the fins and the base are formed by a method selected from the group consisting of a combination of one or more of soldering, engaging, embedding, and adhering.

7. The heat sink as described in claim 1, wherein the main body is one-piece molded.

8. The heat sink as described in claim 1, wherein the fins are arranged in a longitudinal, parallel, transverse, diagonal, or irregular array.

9. The heat sink as described in claim 1, wherein neighboring vapor chambers are communicated with each other or in fluid communication through the porous structures.

10. A heat dissipating device, comprising:

a main body having a plurality of hollow protrusions and a base, the protrusions and the base forming a closed room; and

a plurality of porous structures set respectively on the interior surfaces of the protrusions and connected to the base, each porous structure defining a vapor chamber.

11. The heat dissipating device as described in claim 10, wherein the protrusions are hollow and each protrusion has a close end and an open end facing the base.

12. The heat dissipating device as described in claim 10, wherein one of the protrusions has a fin shape, columnar shape, lamellar shape, conical shape, or lump shape.

13. The heat dissipating device as described in claim 10, wherein the porous structures are wicks.

14. The heat dissipating device as described in claim 13, wherein the wicks are selected from the group consisting of a combination of one or more of mesh wicks, fiber wicks, sintered wicks, and groove wicks.

15. The heat dissipating device as described in claim 10, wherein the porous structures and the main body are assembled by sintering, adhering, filling, or depositing.

16. The heat dissipating device as described in claim 10, wherein the porous structures contain a liquid.

17. The heat dissipating device as described in claim 16, wherein the liquid is selected from the group consisting of a mixture of one or more of inorganic compounds, water, alcohols, liquid metals, ketones, refrigerants, and organic compounds.

18. The heat dissipating device as described in claim 10, wherein the material of the porous structures is selected from the group consisting of a mixture of one or more of plastics, metals, alloys, and porous non-metal materials.

19. The heat dissipating device as described in claim 10, wherein the main body is one-piece molded.

20. The heat dissipating device as described in claim 10, wherein the protrusions and the base are formed by soldering, engaging, embedding, or adhering.

21. The heat dissipating device as described in claim 10, wherein neighboring vapor chambers are communicated with each other.

22. The heat dissipating device as described in claim 10, wherein neighboring vapor chambers are in fluid communication through the porous structures.

23. The heat dissipating device as described in claim 10, wherein the vapor chambers of the porous structures are arranged in the closed room in a longitudinal, parallel, transverse, diagonal, or irregular array.