US20110154833A1

US20110154833A1 - Miniaturized liquid cooling device

Info

Publication number: US20110154833A1
Application number: US12/755,437
Authority: US
Inventors: Chien-Yu Chao; Yen-Chih Chen
Original assignee: Foxconn Technology Co Ltd
Current assignee: Foxconn Technology Co Ltd
Priority date: 2009-12-29
Filing date: 2010-04-07
Publication date: 2011-06-30
Also published as: TW201122403A; TWI506238B

Abstract

An exemplary miniaturized liquid cooling device includes a base, a closed loop pipe and electrode units formed on the base. The loop pipe has a pipe body defining a loop passage therein for accommodating a working fluid. A hydrophobic layer is formed on an inner surface of the pipe body. The electrode units are spaced from each other along the loop pipe. Each electrode unit comprises a first electrode and an opposite second electrode. The first and the second electrodes of each electrode unit are located at two sides of the pipe body of the loop pipe to sandwich the pipe body therebetween. A first dielectric layer is formed between the first electrode and an outer surface of the pipe body. A second dielectric layer is formed between the second electrode and the outer surface of the pipe body.

Description

BACKGROUND

1. Technical Field
The disclosure generally relates to liquid cooling devices, and more particularly to a miniaturized liquid cooling device for dissipating heat generated by electronic components.
2. Description of Related Art
With fast developments in electronic information industries, electronic components such as central processing units (CPUs) of computers are now capable of operating at much higher frequencies and speeds. As a result, the heat generated by these CPUs during normal operation is commensurately increased. If not quickly removed from the CPUs, this generated heat may cause them to become overheated and finally affect their workability and stability.
In order to remove the heat of the CPUs and hence enable the CPUs to continue normal operation, cooling devices are provided on the CPUs to dissipate heat therefrom. A conventional cooling device includes an extruded heat sink combined with a fan. However, such kind of cooling device may be unsatisfactory for cooling a modern high-speed CPU. Nowadays, liquid cooling devices with high heat dissipation efficiencies are often used for dissipating heat generated by high frequency CPUs.
A typical liquid cooling device generally includes a heat absorber absorbing heat from the CPU, a heat dissipater dissipating the heat to the surrounding environment, a plurality of tubes connecting the heat absorber with the heat dissipater, and a pump driving working fluid to circulate along the tubes between the heat absorber and the heat dissipater. However, the pump occupies a large volume, which increases the size of the liquid cooling device. This goes against the need for compact size in electronic products.
What is needed, therefore, is a miniaturized liquid cooling device.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an assembled, isometric view of a miniaturized liquid cooling device in accordance with an exemplary embodiment of the present disclosure.

FIG. 2 is essentially a cross-sectional view of the liquid cooling device of FIG. 1, taken along a line II-II thereof and showing a control circuit used for driving the liquid cooling device.

FIG. 3 is an enlarged view of a circled portion III of FIG. 2.

FIGS. 4-5 are essentially cross-sectional views illustrating a principle of an electrowetting-on-dielectric (EWOD) effect, which principle is utilized by the liquid cooling device of FIG. 1.

DETAILED DESCRIPTION

Referring to FIGS. 1-2, a miniaturized liquid cooling device 200 according to an exemplary embodiment of the present disclosure is shown. The liquid cooling device 200 includes a base 20, a closed loop pipe 21 and a plurality of electrode units 22. The liquid cooling device 200 is used for cooling an electronic component 300.
The base 20 is a rectangular plate made of glass or silicon. The base 20 defines a loop groove 201 in a top surface thereof. The loop pipe 21 is formed on the base 20 and located in the loop groove 201. The loop pipe 21 is made of silicon nitride (Si₃N₄), and defines a loop passage therein. The loop passage of the loop pipe 21 is filled with a working fluid 30. In this embodiment, the loop pipe 21 has a substantially rectangular frame shape, as viewed from above. The loop pipe 21 includes a heat absorbing section 211, and an opposite heat dissipation section 212. The heat dissipation section 212 can be thermally connected to a cooling member via the base 20. The loop pipe 21 forms two substantially spherical reservoirs 213 at two diagonally opposite corners thereof, for storing the working fluid 30. One of the two reservoirs 213 defines an injection hole 214 therein. The working fluid 30 is filled into the loop pipe 21 through the injection hole 214. The injection hole 214 is sealed by a plug 215. The loop pipe 21 is integrally formed on the base 20 by a wet etching method. That is, the loop pipe 21 is in contact with the base 20, with the loop pipe 21 and the base 20 forming portions of a single, unitary body. Referring also to FIG. 3, a hydrophobic layer 216 made of Teflon® (polytetrafluoroethylene) is coated on an inner surface of the loop pipe 21 to make the surface hydrophobic.
The electrode units 22 are formed on the base 20 and spaced from each other along the loop pipe 21. The electrode units 22 are arranged along substantially an entire length of the loop pipe 21. In particular, the electrode units 22 are arranged at substantially regular intervals along the entire length of the loop pipe 21. Each electrode unit 22 includes a first electrode 221 and an opposite second electrode 222. The first electrode 221 and the second electrode 222 of each electrode unit 22 are located at two sides of a pipe body of the loop pipe 21 to sandwich the pipe body of the loop pipe 21 therebetween. In particular, the first electrode 221 and the second electrode 222 of the electrode unit 22 are indirectly connected to the pipe body of the loop pipe 21. A first dielectric layer 23 is formed between the first electrode 221 and an outer surface of the pipe body of the loop pipe 21, and a second dielectric layer 24 is formed between the second electrode 222 and the outer surface of the pipe body of the loop pipe 21. The first electrode 221 and the second electrode 222 are integrally formed on the base 20 via an etching method.
In one method of forming the liquid cooling device 200, the electrode units 22 are firstly formed on the base 20. In this method, the first and the second dielectric layers 23, 24 can then be respectively formed by depositing a layer of silicon nitride (Si₃N₄) on inner ends of the first electrode 221 and the second electrode 222 of each electrode unit 22. After that, the loop pipe 21 is formed on the base 20.
In another method of forming the liquid cooling device 200, the loop pipe 21 is firstly formed on the base 20. In this method, the first and the second dielectric layers 23, 24 can then be respectively formed by depositing a layer of silicon nitride (Si₃N₄) on the outer surface of the loop pipe 21. After that, the electrode units 22 are formed on the base 20.
Referring back to FIG. 2, the first electrode 221 and the second electrode 222 of each electrode unit 22 are electrically connected to a control circuit 40 via a plurality of electrical wires 41. The electronic component 300 is attached to a bottom surface of the base 20, and is located under the heat absorbing section 211 of the loop pipe 21. Heat generated by the electronic component 300 is transferred to the heat absorbing section 211 of the loop pipe 21 via the base 20, thereby heating the working fluid 30 in the loop pipe 21.
Referring to FIGS. 4-5, the electrowetting-on-dielectric (EWOD) effect is a phenomenon where a contact angle of a fluid segment or a fluid droplet varies when a voltage is applied on the fluid segment or fluid droplet (see FIG. 5), whereas a contact angle of the fluid segment or fluid droplet remains as normal when no voltage is applied (see FIG. 4). Therefore, when a voltage is applied on just one side of a fluid segment or fluid droplet, contact angles of two opposite sides of the fluid segment or fluid droplet become different from each other, which causes a difference between surface tensions of the two sides of the fluid segment or fluid droplet. The difference between the surface tensions drives the fluid segment or fluid droplet to move towards a place having higher voltage.
During operation of the liquid cooling device 200, voltages are regularly applied on the electrode units 22 via the control circuit 40 so as to drive the working fluid 30 to move along the loop pipe 21 under the EWOD effect. Thus the heated working fluid 30 in the heat absorbing section 211 of the loop pipe 21 can be driven to the heat dissipation section 212 of the loop pipe 21. After releasing heat through the base 20 at the heat dissipation section 212 of the loop pipe 21, the cooled working fluid 30 is driven back to the heat absorbing section 211 of the loop pipe 21. Thus the working fluid 30 circulates in the liquid cooling device 200 under the EWOD effect to continuously dissipate heat from the electronic component 300 to the surrounding environment.
The liquid cooling device 200 can be manufactured by Micro Electro Mechanical Systems (MEMS) manufacturing technology. The liquid cooling device 200 is miniaturized and occupies a small size. Thus the liquid cooling device 200 can be used in compact electronic products such as notebook computers. The working fluid 30 is driven to efficiently circulate in the loop pipe 21 under the EWOD effect. No mechanical pump exits in the liquid cooling device 200. Therefore, a quiet working environment is obtained.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A miniaturized liquid cooling device, comprising:

a base;

a closed loop pipe formed on the base, the loop pipe comprising a pipe body defining a loop passage therein, a hydrophobic layer being formed on an inner surface of the pipe body;

a working fluid accommodated in the loop passage of the loop pipe; and

a plurality of electrode units formed on the base and spaced from each other along the loop pipe, each electrode unit comprising a first electrode and an opposite second electrode, the first electrode and the second electrode of each electrode unit being located at two sides of the pipe body of the loop pipe to sandwich the pipe body of the loop pipe therebetween, a first dielectric layer being formed between the first electrode and an outer surface of the pipe body of the loop pipe, and a second dielectric layer being formed between the second electrode and the outer surface of the pipe body of the loop pipe.

2. The miniaturized liquid cooling device of claim 1, further comprising a control circuit, the first electrode and the second electrode of each electrode unit being electrically connected to the control circuit, voltages being regularly applied on the electrode units via the control circuit so as to drive the working fluid to move along the loop passage of the loop pipe during operation of the liquid cooling device.

3. The miniaturized liquid cooling device of claim 2, wherein the loop pipe further comprises at least one reservoir fluidly communicating with the pipe body.

4. The miniaturized liquid cooling device of claim 3, wherein the at least one reservoir is generally spherical.

5. The miniaturized liquid cooling device of claim 1, wherein the base defines a loop groove in a top surface thereof, and the loop pipe is located in the loop groove.

6. The miniaturized liquid cooling device of claim 1, wherein the loop pipe is integrally formed on the base.

7. The miniaturized liquid cooling device of claim 6, wherein the loop pipe comprises a heat absorbing section, the base at the heat absorbing section being configured for being thermally connected to an electronic component.

8. The miniaturized liquid cooling device of claim 7, wherein the loop of the loop pipe has a substantially rectangular frame shape, and the loop pipe further comprises a heat dissipation section located opposite to the heat absorbing section.

9. The miniaturized liquid cooling device of claim 1, wherein the first electrode and the second electrode of each electrode unit are integrally formed on the base.

10. The miniaturized liquid cooling device of claim 1, wherein the base is made of one of glass and silicon.

11. The miniaturized liquid cooling device of claim 1, wherein the electrode units are arranged along substantially an entire length of the loop pipe.

12. The miniaturized liquid cooling device of claim 11, wherein the electrode units are arranged at substantially regular intervals along the entire length of the loop pipe.

13. A miniaturized liquid cooling device for cooling an object, the miniaturized liquid cooling device comprising:

a base;

a closed loop pipe formed on the base, the loop pipe comprising a pipe body defining a loop passage therein, and a hydrophobic layer formed on an inner surface of the pipe body, the loop pipe having a heat absorbing section and an opposite heat dissipation section, the base at the heat absorbing section configured for being thermally connected to the object;

a working fluid accommodated in the loop passage of the loop pipe;

a plurality of electrode units formed on the base and spaced from each other along a length of the loop pipe, each electrode unit comprising a first electrode and an opposite second electrode, the first electrode and the second electrode of each electrode unit being located at two sides of the pipe body of the loop pipe to sandwich the pipe body of the loop pipe therebetween;

a first dielectric layer formed between the first electrode and an outer surface of the pipe body of the loop pipe; and

a second dielectric layer formed between the second electrode and the outer surface of the pipe body of the loop pipe.

14. The miniaturized liquid cooling device of claim 13, further comprising a control circuit, the first electrode and the second electrode of each electrode unit being electrically connected to the control circuit, voltages being regularly applied on the electrode units via the control circuit so as to drive the working fluid to move along the loop passage of the loop pipe during operation of the liquid cooling device.

15. The miniaturized liquid cooling device of claim 13, wherein the base defines a loop groove in an outer surface thereof, and the loop pipe is located in the loop groove.

16. The miniaturized liquid cooling device of claim 15, wherein the loop pipe is integrally formed on the base.

17. The miniaturized liquid cooling device of claim 13, wherein the base is one of following materials: glass and silicon.

18. The miniaturized liquid cooling device of claim 17, wherein the first electrode and the second electrode of each electrode unit are integrally formed on the base.

19. The miniaturized liquid cooling device of claim 1, wherein the electrode units are arranged along substantially an entire length of the loop pipe.

20. The miniaturized liquid cooling device of claim 19, wherein the electrode units are arranged at substantially regular intervals along the entire length of the loop pipe.