BACKGROUND OF THE INVENTION 1. Field of the Invention
The invention relates to a thin heat pipe and, more particularly, to a thin heat pipe with a capillary structure formed by a chemical etching process.
2. Description of the Prior Art
Heat dissipating device is a significant component for electronic products. When an electronic product is operating, the current in circuit will generate unnecessary heat due to impedance. If the heat is accumulated in the electronic components of the electronic product without dissipating immediately, the electronic components may get damage due to the accumulated heat. Therefore, the performance of heat dissipating device is a significant issue for the electronic product.
So far the heat dissipating device used in the electronic product usually consists of a heat pipe, a heat dissipating fin and a heat dissipating fan, wherein one end of the heat pipe contacts the electronic component, which generates heat during operation, the other end of the heat pipe is connected to the heat dissipating fin, and the heat dissipating fan blows air to the heat dissipating fin so as to dissipate heat. In general, the heat pipe mainly consists of a hollow tube, a capillary structure and a working fluid. The conventional capillary structure is formed by sintering metal powders on an inner wall of the hollow tube through a sintering process. Consequently, the conventional capillary structure occupies partial inner space of the hollow tube such that the heat pipe cannot be thinned.
SUMMARY OF THE INVENTION The invention provides a thin heat pipe with a capillary structure formed by a chemical etching process, so as to solve the aforesaid problems.
According to an embodiment of the invention, a thin heat pipe comprises a thin hollow tube and a capillary structure. The capillary structure is formed in at least half of an inner wall of the thin hollow tube by a chemical etching process . In this embodiment, a wall thickness of the thin hollow tube is between 0.2 mm and 0.3 mm.
As mentioned in the above, the invention forms the capillary structure in at least half of the inner wall of the thin hollow tube by the chemical etching process. Since the capillary structure is formed in the inner wall of the thin hollow tube, it does not occupy inner space of the thin hollow tube such that the heat pipe of the invention can be thinned accordingly.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram illustrating a thin heat pipe according to a first embodiment of the invention.
FIG. 2 is a cross-sectional view illustrating the thin heat pipe along line X-X shown in FIG. 1.
FIG. 3 is a microscopic diagram illustrating parts of the capillary structure shown in FIG. 2, wherein a magnification shown in FIG. 3(B) is larger than that shown in FIG. 3(A).
FIG. 4 is a schematic diagram illustrating the thin heat pipe shown in FIG. 1 connected to a non-thin heat pipe.
FIG. 5 is a cross-sectional view illustrating a thin heat pipe according to a second embodiment of the invention.
FIG. 6 is a schematic diagram illustrating a thin heat pipe according to a third embodiment of the invention.
FIG. 7 is a schematic diagram illustrating a thin heat pipe according to a fourth embodiment of the invention.
FIG. 8 is a schematic diagram illustrating a thin heat pipe according to a fifth embodiment of the invention.
FIG. 9 is a microscopic diagram illustrating parts of the capillary structure shown in FIG. 8, wherein a magnification shown in FIG. 9(B) is larger than that shown in FIG. 9(A).
DETAILED DESCRIPTION Referring to FIGS. 1 and 2, FIG. 1 is a schematic diagram illustrating a thin heat pipe 1 according to a first embodiment of the invention, and FIG. 2 is a cross-sectional view illustrating the thin heat pipe 1 along line X-X shown in FIG. 1. As shown in FIGS. 1 and 2, the thin heat pipe 1 comprises a thin hollow tube 10, a capillary structure 12 and a working fluid 14. The thin hollow tube 10 is elongated and sealed and may be made of copper, aluminum or other metal materials with good heat conductivity. The thin hollow tube 10 has an inner space 100 for accommodating the working fluid 14. In practical applications, the working fluid 14 may be water or other fluids with low viscosity.
As shown in FIG. 2, the capillary structure 12 is formed in at least half of an inner wall of the thin hollow tube 10 by a chemical etching process. Since the capillary structure 12 is formed in the inner wall of the thin hollow tube 10, it does not occupy the inner space 100 of the thin hollow tube 10. In this embodiment, a wall thickness T1 of the thin hollow tube 10 may be, but not limited to, between 0.2 mm and 0.3 mm. Furthermore, a thickness T2 of the capillary structure 12 may be between ⅓ times and ⅔ times the wall thickness T1 of the thin hollow tube 10. In this embodiment, the capillary structure 12 is a porous capillary structure comprising a plurality of micro-holes 120 and a diameter of each micro-hole 120 is between 1 μm and 100 μm.
Referring to FIG. 3, FIG. 3 is a microscopic diagram illustrating parts of the capillary structure 12 shown in FIG. 2, wherein a magnification shown in FIG. 3(B) is larger than that shown in FIG. 3(A). As shown in FIG. 3, a shape of each micro-hole 120 of the capillary structure 12 formed by the chemical etching process is irregular and the arrangement of each micro-hole 120 is also irregular. It should be noted that the arrangement, shape and diameter of each micro-hole 120 are determined by process parameters of the chemical etching process.
In this embodiment, the thin hollow tube 10 has an evaporation end 102 and a condensation end 104 and the capillary structure 12 at least covers the evaporation end 102. As shown in FIG. 2, the evaporation end 102 of the thin hollow tube 10 is disposed on the heat source 3 (e.g. electronic component, which generates heat during operation, of an electronic product). The working fluid 14 can permeate into the capillary structure 12 by capillary effect and evaporate by heat so as to flow circularly in the inner space 100. The inner wall of the evaporation end 102 may be hydrophilic and the inner wall of the condensation end 104 may be hydrophobic, so as to accelerate the working fluid 14 to flow circularly in the inner space 100 of the thin hollow tube 10. Accordingly, the heat dissipating efficiency is enhanced.
It should be noted that, under different conditions, the inner wall of the evaporation end 102 may be hydrophobic and the inner wall of the condensation end 104 may be hydrophilic, or alternatively all the inner wall of the thin hollow tube 10 may be hydrophilic or hydrophobic. In other words, the property of the inner wall of the thin hollow tube 10 can be determined based on practical applications.
Referring to FIG. 4, FIG. 4 is a schematic diagram illustrating the thin heat pipe 1 shown in FIG. 1 connected to a non-thin heat pipe 5. For different heat dissipation requirements, some heat pipes consist of different heat pipes with different sizes. The thin heat pipe 1 of the invention may be connected to the non-thin heat pipe 5 so as to form the heat pipe shown in FIG. 4. As mentioned in the above, the capillary structure 12 of the thin heat pipe 1 is formed in at least half of the inner wall of the thin hollow tube 10 by the chemical etching process, but a capillary structure (not shown) of the non-thin heat pipe 5 is formed on the inner wall of the hollow tube by a sintering process or other processes. The tube sizes of the thin heat pipe 1 and the non-thin heat pipe 5 can be determined based on practical applications.
Referring to FIG. 5, FIG. 5 is a cross-sectional view illustrating a thin heat pipe 1′ according to a second embodiment of the invention. The difference between the thin heat pipe 1′ and the aforesaid thin heat pipe 1 is that a capillary structure 12′ of the thin heat pipe 1′ is formed in all the inner wall of the thin hollow tube 10 by the chemical etching process. In other words, the capillary structure 12′ covers the evaporation end 102 and the condensation end 104 completely. In this embodiment, the capillary structure 12′ is also a porous capillary structure comprising a plurality of micro-holes 120. It should be noted that the same elements in FIG. 5 and FIG. 2 are represented by the same numerals, so the repeated explanation will not be depicted herein again. Furthermore, the thin heat pipe 1 shown in FIG. 4 can be replaced by the thin heat pipe 1′ shown in FIG. 5.
Referring to FIG. 6, FIG. 6 is a schematic diagram illustrating a thin heat pipe 4 according to a third embodiment of the invention. As shown in FIG. 6, the thin heat pipe 4 consists of a thin heat pipe 40 with large cross-section and a thin heat pipe 42 with small cross-section, wherein the thin heat pipe 40 communicates with the thin heat pipe 42. In this embodiment, the capillary structure 12 shown in FIG. 2 or the capillary structure 12′ shown in FIG. 5 may be formed in the inner walls of the thin heat pipes 40, 42 by the chemical etching process. Furthermore, the thin heat pipe 40 may be an evaporation end, the inner wall of the thin heat pipe 40 may be hydrophilic, the thin heat pipe 42 may be a condensation end, and the inner wall of the thin heat pipe 42 may be hydrophobic . It should be noted that the aforesaid embodiment is for illustration purpose only and the invention is not limited to this embodiment.
Referring to FIG. 7, FIG. 7 is a schematic diagram illustrating a thin heat pipe 4′ according to a fourth embodiment of the invention. As shown in FIG. 7, the thin heat pipe 4′ consists of a thin heat pipe 40 with large cross-section and two thin heat pipes 42, 44 with small cross-section, wherein the thin heat pipe 40 communicates with the thin heat pipes 42, 44 and is located between the thin heat pipes 42, 44. In this embodiment, the capillary structure 12 shown in FIG. 2 or the capillary structure 12′ shown in FIG. 5 may be formed in the inner walls of the thin heat pipes 40, 42, 44 by the chemical etching process. Furthermore, the thin heat pipe 40 may be an evaporation end, the inner wall of the thin heat pipe 40 may be hydrophilic, the thin heat pipes 42, 44 may be condensation ends, and the inner walls of the thin heat pipes 42, 44 may be hydrophobic. It should be noted that the aforesaid embodiment is for illustration purpose only and the invention is not limited to this embodiment.
Referring to FIGS. 8 and 9, FIG. 8 is a schematic diagram illustrating a thin heat pipe 6 according to a fifth embodiment of the invention, and FIG. 9 is a microscopic diagram illustrating parts of the capillary structure 62 shown in FIG. 8, wherein a magnification shown in FIG. 9(B) is larger than that shown in FIG. 9(A). The difference between the thin heat pipe 6 and the aforesaid thin heat pipe 1 is that the capillary structure 62, which is formed in the inner wall of the thin hollow tube 10 of the thin heat pipe 6 by the chemical etching process, is groove-type capillary structure. As shown in FIG. 9, the image within the dotted line frame shows grooves of the capillary structure 62 formed by the chemical etching process. It should be noted that the same elements in FIG. 8 and FIG. 2 are represented by the same numerals, so the repeated explanation will not be depicted herein again. Furthermore, the arrangement and shape of each groove of the capillary structure 62 are determined by process parameters of the chemical etching process. Moreover, the aforesaid porous capillary structure 12 or 12′ can be replaced by the groove-type capillary structure 62.
Compared to the prior art, the invention forms the capillary structure in at least half of the inner wall of the thin hollow tube by the chemical etching process. Since the capillary structure is formed in the inner wall of the thin hollow tube, it does not occupy inner space of the thin hollow tube such that the heat pipe of the invention can be thinned accordingly.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
