GB2427582A

GB2427582A - Manufacture of a heat pipe using ultrasonic welding

Info

Publication number: GB2427582A
Application number: GB0513143A
Authority: GB
Inventors: Pei-Pei Ding; Hsiu-Wei Yang; Jao-Ching Lin; Wen-Hwa Yu; Yen-Wen Chen
Original assignee: Asia Vital Components Co Ltd
Current assignee: Asia Vital Components Co Ltd
Priority date: 2005-06-28
Filing date: 2005-06-28
Publication date: 2007-01-03
Also published as: GB0513143D0

Abstract

A planar heat pipe manufacturing method is disclosed. The method makes use of an ultrasound welding system 2, to form a first component 31 and a second component 32, both of which are ductile and have the shape of a thin plane, into a planar heat pipe. The system 2 has a welding head 22 capable of moving along a straight line X and generating ultrasound vibration. The method includes (A) ultrasound welding the first component 31 to the second component 32 by propping the welding head 22 against the stacked first and second components 31,32 along the straight line X (B) moving the welding head 22 along a close route perpendicular to the straight line X and corresponding to the first and second components 31,32, and the welded first and second components forming a cavity, (C) deaerating gas of the cavity, (D) filling working fluid into the cavity, and (E) sealing the cavity. The cavity preferably includes a capillary structure 4.

Description

PLANAR HEAT PIPE MANUFACTURING METHOD USING

ULTRASOUND WELDING TECHNIQUE

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a planar heat pipe manufacturing method, and, more particularly, to a planar heat pipe manufacturing method using an ultrasound welding technique.

2. Description of the Prior Art

A heat pipe is one of the best heat conduction components used in 3C electronic devices, and is therefore usually applied to a heat source, such as a microprocessor of a notebook computer, a host of a play station, or a communication host, which are all not allowed to be installed with large sized heat conduction fins.

The heat pipe is used to conduct heat generated by the above heat sources to a heat conductor comprising heat conduction fins. The heat pipe is cheap, and has a lifespan as long as tens of years, for the heat pipe is a kind of passive heat conduction components. Different from copper or aluminum heat conduction components, which have constant conductivities, the heat pipe has a variable conductivity. The longer a length of the heat pipe is, the larger the heat conductivity of the heat pipe becomes.

Moreover, the heat conductivity of a conventional heat pipe is tens or more than tens of thousands times as large as the heat conductivity of copper.

Please refer to Fig.l. A conventional planar heat pipe 1 comprises a hollow package 11, a capillary structure 12 installed in an inner surface of the package 12, and working fluid 13 accommodated in the package 11. The package 11 comprises an endothermic end ill and a radiating end 112 installed opposite to the endothermic end 111. A pressure inside the package 11 is equal to a saturated vapor pressure of the working fluid 13, which is in a stable equilibrium state when a liquid state and a gas state exist concurrently. Additionally, the capillary structure 12 comprises a plurality of capillaries 121 infiltrated in the working fluid 13.

When the endothermic end 111 is heated and a temperature of the endothermic end 111 is increased, the stable equilibrium state of the working fluid 13 near the endothermic end 111 is destroyed, causing the liquid working fluid 13 neighboring the endothermic end ill to be evaporated gradually. At this moment, the endothermic end 111 has a vapor pressure higher than that of the radiating end 112, so a great volume of gas working fluid 13 is driven to flow from the endothermic end 111 to the radiating end 112. Since the temperature of the radiating end 112 is still low, the radiating end 112 is capable of congealing the gas working fluid 13 neighboring the radiating end 112 flew from the endothermic end ill. The excess congealed working fluid 13 flows along the capillaries 121 back to the endothermic end 111. A heat radiation cycle to radiate heat from the endothermic end ill to the radiating end 112 is therefore completed.

Since the heat radiation cycle is realized by destroying the stable equilibrium state of the working fluid 13, the heat radiation cycle can still function and radiate considerable quantity of heat continuously, even though the temperatures of the two ends of the package 11 differ from each other slightly.

In the following paragraphs, a flow chart shown in Fig.2 is used to illustrate the method to manufacture the conventional planar heat pipe 1.

Please also refer to Fig.1 and Fig.3. The method shown in Fig.2 starts from step 191. In step 191, a first component 113 and a second component 114 are formed. The first component 113 is complementary to the second component 114 in shape. Both of the first component 113 and the second component 114 are made of materials of good heat conductivity.

In step 192, a capillary structure 12 is formed. The capillary structure 12 is in the shape of a plurality of long striped ditches through the use of a depression process on opposite surfaces of the first component 113 and the second component 114.

In step 193, the first component 113 and the second component 114 are welded with a steel pipe 14. In the past, some available jointing materials such as glue or solder strips are installed in a peripheral region of the opposite surfaces of the first component 113 and the second component 114 to fix the first component 113 to the second component 114, so as to form a package 11. In the mean time, the package 11 comprises a corner for insertion of the steel pipe 14. The first component 113 can also be fixed to the second component 114 by fusing their welding points. However, either the fusing welding points or the jointing materials forms a heterogeneous interface 116 (as shown in Fig.4) in a jointing region between the first component 113 and the second component 114.

Please refer to Fig.l and Fig.4. In step 194, a working fluid filling process can be performed through the use of the steel pipe 14. In a conventional heat pipe, water is selected as a working fluid 13. In some other heat pipes, methyl alcohol, or propyl alcohol, is selected as the working fluid 13.

Different kinds of working fluid correspond to different working temperatures, beyond which the heat radiation cycle cannot be performed successfully.

In order to ensure that the heat radiation cycle can be performed successfully, a working pressure of the package 11 had better to be kept equal to a vapor pressure of the working fluid 13, that is enabling the working fluid 13 to reach the stable equilibrium state. Then, a deaerating process is performed in step 195 to deaerate gas except the gas working fluid 13 in the package 11. In general, as long as a pressure of the package 11 is equal to the vapor pressure of the working fluid 13, the gas except the gas working fluid 13 is determined having been expelled to a region outside of the package 11 completely.

In step 196, a clamping device 16 is used to clamp an end of the steel pipe 14. In step 197, a clipping device 17 is used to clip the steel pipe 14, which has been clamped by the clamping device 16 in step 196. Thus far, the package 11, as shown in Fig.1, has been sealed completely.

Please refer to Fig.5. In step 198, a seaming device 18 is used to spot weld the steel pipe 14, which has been clipped by the clipping device 17, to air tighten the package 11 completely.

In step 199, the package 11 is finished and formed. In the current trend, a notebook is demanded to be compact. In order to be able to be installed among the electronic components of the notebooks to save capacity, the planar heat pipe 1, if applied to the notebook, has to be through a bending process inevitably.

Note that in the bending process, the heterogeneous interface 116 formed in step 193 generates crisp easily or is broken. In such a scenario, the stable equilibrium state of the working fluid 13 is destroyed.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the claimed invention to provide a planar heat pipe manufacturing method to manufacture a planar heat pipe having a guaranteed quality.

Another objective of the claimed invention is to provide a planar heat pipe manufacturing method to manufacture a durable bendable planar heat pipe.

Another objective of the claimed invention is to provide a planar heat pipe manufacturing method using an ultrasound welding technique.

A planar heat pipe manufacturing method makes the use of an ultrasound welding technique in coordination to an ultrasound welding system, to form a first component and a second component, both of which are ductile and have the shape of a thin plane, into a planar heat pipe. The system has a welding head capable of moving along a straight line and generating ultrasound vibration. The method includes (A) ultrasound welding the first component to the second component by propping the welding head against the stacked first and second components along the straight line, (B) moving the welding head along a close route perpendicular to the straight line and corresponding to the first and second components, and the welded first and second components forming a cavity, (C) deaerating gas of the cavity, (D) filling working fluid into the cavity, and CE) sealing the cavity.

BRIEF DESCRIPTION OF DRAWINGS

Fig.l is a cross sectional view of a conventional planar heat pipe.

Fig.2 is a flow chart of a method to manufacture the planar heat pipe shown in Fig.l.

Fig.3 is a schematic diagram of a package and a steel pipe.

Fig.4 is a top view of the package and the steel pipe, both of which are shown in Fig.3, and a deaerating & filling device.

Fig.5 is a top view of the package and the steel pipe, both of which are shown in Fig.3, and a sealing device.

Fig.6 is a flow chart of a planar heat pipe manufacturing method using an ultrasound welding technique of a first preferred embodiment according to the present invention.

Fig.7 is an explosive view of a planar heat pipe of the first preferred embodiment.

Fig.8 is a flow chart of an ultrasound welding technique.

Fig.9 is a schematic diagram of an ultrasound welding system.

Fig.lO is an incomplete view of the ultrasound welding system shown in Fig.9.

Fig.ll is a top view of a welding gear of the ultrasound welding system shown in Fig.9.

Fig.l2 is a top view of a package and a deaerating & filling pipe of the first preferred embodiment Fig.l3 is the package and the deaerating & filling pipe shown in Fig.l3 and a deaerating & filling mechanism of the first preferred embodiment.

Fig.l4 is the package and the deaerating & filling pipe shown in Fig.13 and a sealing mechanism of the first preferred embodiment.

Fig.15 is a top view of another package to demonstrate a planar heat pipe manufacturing method using an ultrasound welding technique of a second preferred embodiment according to the present invent ion.

Fig.16 is a cross sectional view of the package, a deaerating & filling mechanism, and a sealing mechanism of the second preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The premise and other related technique contents, characteristics, and virtues of the present invention will be presented clearly in accord with detailed descriptions of two preferred embodiments of reference figures.

Before the present invention is described, note that similar components are assigned the same numbers in the following paragraphs.

Please refer to Fig.6. A first preferred embodiment of a planar heat pipe manufacturing method using an ultrasound welding technique of the present invention comprises steps 91 to 99.

Please refer to Fig.7. In step 91, available metal processes are used to form a first component 31 and a second component 32 complementary to the first component 31 in shape. Both of the first component 31 and the second component 32 have the shape of a thin plane and are made of copper, aluminum, or any other materials of good ductility and heat conductivity. The first component 31 and the second component 32 can be made of the same or different materials. The first component 31, and the second component 32 as well, comprises a corner 37 installed in a first region opposite to a second region of the second component 32 where another corner 37 of the second component 32 is installed for insertion of a deaerating & filling pipe 35.

In step 92, the available metal processes are used to form a capillary structure 4. The capillary structure 4 can be made of copper, aluminum, or any other materials of good heat conductivity. In the first preferred embodiment, the capillary structure 4 is a metal network, which comprises a plurality of capillaries 41 in communication with one another.

Such the capillaries 41 described here enable liquid to generate a capillarity effect. Thus, when some part of the capillary structure 4 contacts liquid, the liquid will be diffused via the capillaries 41 to the rest part of the capillary structure 4 quickly. Such a diffusion process has nothing to do with a direction of gravity. Therefore, the actual size of the capillaries 41 depend on the materials of the capillary structure and the liquid applied in coordination with the capillary structure 4. Moreover, when the first component 31, the second component 32, and the capillary structure 4 are stacked together, a peripheral region of the first component 31 protrudes a peripheral region of the capillary structure 4, and so does a peripheral region of the second component 32.

In step 93, the first component 31, the second component 32, and the deaerating & filling pipe 35 are assembled in coordination to an ultrasound welding system 2.

Please refer to Fig.9, Fig.1O, and Fig.ll. The ultrasound welding system 2 comprises a body 20, a platform 21, and a welding head 22. Both of the platform 21 and the welding head 22 are installed extending from an end of the body 20 and along a straight line X. The welding head 22 generates ultrasound vibration having a vibrating direction perpendicular to the straight line X. Additionally, in order to prevent the first component 31 and the second component 32 from generating relative sliding movements resulted from the ultrasound vibration, a skid strip 211 is installed along the straight line X on the platform 21, and a welding gear 221 is installed also along the straight line X on the welding head 22. A plurality of convex parts 222 and concave parts 223 are formed on an end surface of the welding gear 221 neighboring the skid strip 211 to provide the first component 31 and the second component 32 with strong enough side frictional force (as shown in Fig.ll) Please refer to Fig. 8 and Fig. lO. Step 93 comprises the following sub-steps- steps 931, 933, 935, and 937.

In step 931, the second component 32, the capillary structure 4, and the first component 31 are stacked on the skid strip 211 sequentially. Only the first component 31 and the second component 32 need to be welded, for both the first component 31 and the second component 32, when stacked on the skid strip 211, protrude to a region corresponding to the peripheral region of the capillary structure 4 and opposite to the welding gear 221 and the skid strip 211.

In step 933, the welding gear 221 is controlled to approach the skid strip 211 along the straight line X, and the peripheral regions of the first component 31 and the second component 32, which protrude the capillary structure 4, are against to each other when the welding gear 221 approaches the skid strip 211.

In step 935, the welding head 22 generates the ultrasound vibration having the vibrating direction perpendicular to the straight line X. The applied ultrasound vibration is to function according to the materials composed in the first component 31 and the second component 32. In general, the ultrasound vibration has a vibrating frequency from 20 to 40 thousand hertz, and a vibrating amplitude equal to micrometers. The applied ultrasound vibration enables the first component 31 and the second component 32 to rob to each other, and removes oxide metal layer and impurities on surfaces of the first component 31 and the second component 32, 80 that the first component 31 can be combined with the second component 32 closely with a cleaner surface, and vice versa.

In step 937, the first component 31 and the second component 32 are moved. In detail, a tensional force is applied to move the first component 31 and the second component 32, to enable the welding gear 221 to move along the peripheral regions of first component 31 and the second component 32 to form a package 3 (as shown in Fig.12) In contrast to welding techniques, such as a resistor heat welding technique, a laser welding technique, a brazed welding technique, and a solder welding technique, any one of which comprises many steps, the ultrasound welding technique comprises only one step and can still reach an efficiency as good as efficiencies of these complicated welding techniques. The ultrasound welding technique needs neither welding strips for heating purpose, nor a welding preceding process and a welding succeeding cleaning process. Moreover, the ultrasound welding technique consumes power one thirtieth as much as the power consumed by a conventional welding technique. In practice, the ultrasound welding technique does not use poison chemical materials, and does not generate welding smog. The ultrasound welding technique can be monitored in time, and can be operated accurately, so that the quality of finished products is ensured.

Moreover, the ultrasound welding technique belongs to low temperature processes, and has a working temperature due to friction is lower than one third of a melting point of the welded materials. Because the ultrasound welding technique generates less heat, an additional water cooling device is omitted. Since the welded materials do not need a melting & annealing process, the welded materials can be transferred to the next process, to increase the manufacturing efficiency.

The above low temperature characteristic is very important for the heat pipe applications. In melting and welding processes, insulating and fragile intermetallic compounds are generated easily. The compounds destroys the ductility of welding points.

Since the ultrasound welding technique does not melt the welded materials, the ultrasound welding technique does not destroy the ductility of the compounds Please refer to Fig.l2 and Fig.l3. The finished package 3 comprises a cavity 33, and a stamped pattern 36 formed on a welding region opposite to an outline of the welding gear 221 (as shown in Fig.ll) . The denser the stamped pattern 36 is, the better the sealing quality of the package 3 becomes.

The capillary structure 4 is located in the cavity 33, and comprises two opposite side surfaces contacted to an inner surface of the package 3 respectively. Through the inner surface and the two side surfaces, heat can be conducted from the package 3 to the capillary structure 4, and vice versa.

Note that steps 91 to 93 are disclosed here to demonstrate the first preferred embodiment only. In practical use, the capillary structure 4 in step 92 can be formed directly on the two opposite side surfaces of the first component 31 and the second component 32 through the use of an impression process or a seal cutting process. Such a structure can also be obtained by using the ultrasound welding technique to weld and combine the first component 31 and the second component 32.

Please refer to Fig.6 and Fig.13. In step 94, a deaerating & filling mechanism 6 is used to fill working fluid 5 via the deaerating & filling pipe 35 into the cavity 33. The working fluid 5 can be water, methyl alcohol, propyl alcohol, or any other proper fluid. The deaerating & filling mechanism 6 makes use of a pump to pump and fill the working fluid into the cavity 33. The volume of the working fluid 5 filled into the cavity 33 is constant, so that all of the capillaries 41 can be infiltrated into the working fluid 5.

In step 95, the deaerating & filling mechanism 6 is further used to reduce the inner pressures of the deaerating & filling pipe 35 and the cavity 33, to make the inner pressure of the cavity 33 is equal to the vapor pressure of the working fluid 5 in the working temperature and to expel the excess of gas in the cavity 33.

Note that using the deaerating & filling mechanism 6 to execute steps 94 and 95 are disclosed here to demonstrate the first preferred embodiment only. Any mechanism with the similar functions can be used to realize the present invention. For example, filling by hand & vacuum pump deaerating, a conventional deaerating & filling process, can obtain the same efficiency, and can be applied here to execute steps 94 and 95.

In steps 96 and 97, a sealing mechanism 7 is used to seal the cavity 33. The sealing mechanism 7 comprises a clamping device 71 and a clipping device 72, both of which are driven by conventional driven mechanisms, such as a water pressing mechanism or an oil pressing mechanism. In step 96, the clamping device 71 clamps an end of the deaerating & filling pipe 35. In step 97, the clipping device 72 clips the deaerating & filling pipe 35, which has been clamped by the clamping device 71, to form a clipped cross surface 351. Thus far, the cavity 33 is sealed completely.

Please refer to Fig.6 and Fig.14. In step 98, a seaming mechanism 8 is used to seam the clipped cross surface 351, to obtain the air tightened effect. The seaming mechanism 8 can be realized through the use of a spot gluing process, a spot welding process. The spot gluing process glues epoxy resin, silicon glue, or UV glue onto the clipped cross surface to seal to package 3. The spot welding process, for example, makes the use of ultrasound welding system 2 to perform a welding process, which is similar to the process disclosed in step 93, further description hereby omitted. The spot welding process can also perform a heat welding process on solder paste or silver tin, which is applied to the clipped cross surface 351, and convey the clipped cross surface 351 into a reflow or use a heating gun to melt the solder paste and the silver tin. The melted solder paste and sliver tin is adhered to the clipped cross surface 351, so as to seal the package 3 completely.

In step 99 the last step, the package 3 is finished and formed. Since the package 3 does not comprise the heterogeneous interface 116 (as shown in Fig.4) which is formed by some other welding technique, the package 3 does not generate any crisp and will not be broken, to diminish the possibility to destroying the stable equilibrium state of the Please refer to Fig.15 and Fig.l6. A second preferred embodiment of a planar heat pipe manufacturing method using the ultrasound welding technique of the present invention is similar to the first preferred embodiment. Differences between the first and the second preferred embodiments are the assembled package 3 of the second preferred embodiment does not comprise the corner 37 (as shown in Fig.l2), but the second preferred embodiment further comprises a projecting part 34 and an opening 34 formed on a side surface of the projecting part 34. Thus, in the second preferred embodiment, after the package 3 is assembled, the deaerating & filling pipe 35 is connected to the opening 341 and to the cavity 33 as well through the use of the conventional welding or gluing process.

Moreover, in the second preferred embodiment both the clamping process in step 96 and the clipping process in step 97 are preformed on the projecting 34, rather than the deaerating & filling pipe 35, 50 as to overcome the drawback that in step 93 the ultrasound welding process is performed while another process to weld the deaserting & filling pipe 35 has to be performed concurrently. Similarly, in step 98 a cross surface 342, which is clipped from the projecting part 34, is spot welded.

In summary, the present invention makes the use

of the characteristics of the ultrasound welding system 2 to overcome the drawback that a joint part, which is jointed to the package 3 through the use of the welding process or the gluing process, of the package 3 is easily broken when the package 3 has to be bent, Moreover, the ultrasound welding technique does not need an additional water cooling device, and can accelerate the efficiency of manufacturing

process. In conclusion, the planar heat pipe

manufacturing method using the ultrasound welding technique of the present invention indeed achieves the goals and merits of the invention.

Following the detailed description of the

present invention above, those skilled in the art will readily observe that numerous modifications and alterations of the device 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.

Claims

CLAIMS: What is claimed is: 1. A planar heat pipe manufacturing method

using an ultrasound welding technique in coordination to an ultrasound welding system, to form a first component and a second component, both of which are ductile and have the shape of a thin plane, into a planar heat pipe, the ultrasound welding system comprising a welding head capable of moving along a straight line and generating ultrasound vibration, the planar heat pipe manufacturing method comprising: (A) ultrasound welding the first component to the second component by propping the welding head against the stacked first and second components along the straight line; (B) moving the welding head along a close route perpendicular to the straight line and corresponding to the first and second components, and the welded first and second components forming a cavity; (C) deaerating gas of the cavity; (B) filling working fluid into the cavity; and (E) sealing the cavity.
2. The method of claim 1, where step (C) comprises: (C-i) inserting a deaerating & filling pipe connected to the cavity between the first and second components; (C-2) reducing an inner pressure of the deaerating & filling pipe to performing a deaerating process.
3. The method of claim 1, wherein step (D) makes the use of a deaerating & filling pipe connected to the cavity to fill the working fluid into the cavity.
4. The method of claim 1 further comprising step (F) stacking a capillary structure between the first component and the second component.
5. The method of claim 1 further comprising step (F) welding an opening to seal the cavity.
6. The method of claim 5, wherein step (F) makes the use of a spot gluing process to weld the opening.
7. The method of claim 5, wherein step (F) makes the use of a spot welding process to weld the opening.