US20100059207A1

US20100059207A1 - Fin, thermal module, and method for assembling the same

Info

Publication number: US20100059207A1
Application number: US12/554,284
Authority: US
Inventors: Yu Wei Chang; Chao Tsai Chung
Original assignee: Pegatron Corp
Current assignee: Pegatron Corp
Priority date: 2008-09-05
Filing date: 2009-09-04
Publication date: 2010-03-11
Also published as: TWI340229B; TW201011246A

Abstract

This invention provides a method for assembling the thermal module. According to the invention, the fin can be combined with a heat pipe and a joint material to form the thermal module. The fin includes a main body having a through hole and an feeding hole communicating with each other. The heat pipe passes through the through hole. The joint material is injected into the feeding hole to fill a clearance between the heat pipe and the inner wall of the through hole. In addition, when the fin is combined with the heat pipe, the feeding hole is above the through hole, the joint material flows downward along the clearance, and the clearance gradually narrows along a flowing direction of the joint material.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 097134173 filed in Taiwan, Republic of China on Sep. 5, 2008, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a cooling fin, a thermal module including the cooling fin, and a method for assembling the thermal module.
2. Description of the Related Art
In past, only a central processing unit needs a thermal module to keep an operating temperature and stability of the central processing unit. With improvement of operating performance of other electronic elements, such as a graphic chip, a north bridge chip, a south bridge chip, a light-emitting diode and so on, the thermal module becomes more and more important for preserving stability of the electronic elements and the electronic devices having the electronic elements.
For manufacturing light, slim, and powerful electronic device, a plurality of electronic elements is assembled on a circuit board with a limited area, which results in a high heat flux of heat dissipation. Therefore, the thermal module becomes more and more important.
A conventional thermal module generally includes a plurality of fins and one or more heat pipes passing through the fins. FIG. 1 is a three-dimensional schematic diagram showing a thermal module in the prior art. In FIG. 1, a thermal module 7 includes a plurality of fins 70 and a heat pipe 72. When the thermal module 7 is made, a through hole 700 whose size and shape are the same with the cross-section of the heat pipe 72 is formed on each of the fins 70 in advance. Then, solder paste 74 is spread on the heat pipe 72, and the heat pipe 72 passes through the through holes 700 one by one.
However, the heat pipe 72 may squeeze the solder paste 74 out when inserting the heat pipe 72 into the through holes 700. Thus, the solder paste 74 overflows onto other positions of the fins 70 around the through holes 700. Therefore, the overflowed solder paste 74 needs to be cleaned manually. Thus, additional labor is needed, and the solder paste 74 is wasted. Further, the distribution of the solder paste 74 is non-uniform, deteriorating the heat dissipation.
Therefore, a patent No. 568261 in Republic of China provides a novel thermal module. FIG. 2A is a three-dimensional schematic diagram showing the thermal module. FIG. 2B is a sectional schematic diagram showing the thermal module in FIG. 2A along a line O-O. In FIG. 2A and FIG. 2B, each fin 90 of a thermal module 9 has a through hole 900 as mentioned above, and the heat pipe 92 passes through the through holes 900 to combine the fins 90 in series. The difference between this patent and FIG. 1 is that a small solder paste feeding hole 902 is formed above the through hole 900 of the fin 90.
When the thermal module 9 is made, the heat pipe 92 first passes through the through holes 900 of the fins 90 one by one. Then, solder paste 94 is injected into the solder paste feeding holes 902. Next, the solder paste 94 is heated to be melted, such that the solder paste 94 flows and fills a clearance between the heat pipe 92 and the through holes 900 via capillary action. Afterwards, the solder paste 94 is cooled and solidified to finish making the thermal module 9.
However, practical applications show that the clearance between the heat pipe 92 and the through hole 900 cannot be fully filled by the patent No. 568261 in Republic of China. FIG. 2C and FIG. 2D are sectional schematic diagrams showing the thermal module in FIG. 2A along the line O-O in practical applications. In the mentioned manufacture process, the solder paste 94 could not flow to the edge of the through hole 900 opposite to the solder paste feeding hole 902. Therefore, the soldering of the fins 90 and the heat pipe 92 is not solid enough, and the solder paste 94 may not flow downward and may deposit at the solder paste adding hole 902. In addition, the non-uniform distribution of the solder paste 94 may also deteriorate the heat dissipation.

BRIEF SUMMARY OF THE INVENTION

One objective of this invention is to provide a cooling fin and a method for assembling the thermal module. Particularly, the invention can uniformly spread the solder material to the clearance between the heat pipe and the fins of the thermal module. The soldering quality and the heat transfer performance can be well improved, thus to improve the prior art.
According to a first embodiment of the invention, the cooling fin can be combined with a heat pipe and a joint material. The cooling fin includes a main body. The main body has a through hole and a feeding hole. The heat pipe passes through the through hole. The feeding hole communicates with the through hole. The joint material is injected into the feeding hole to fill the clearance between the heat pipe and the inner wall of the through hole.
According to a second embodiment of the invention, the thermal module includes a heat pipe, a joint material, and a plurality of fins. As mentioned above, each fin includes a main body having a through hole and an feeding hole. The heat pipe passes through the through hole. The feeding hole communicates with the through hole. The joint material is injected into the feeding hole to fill the clearance between the heat pipe and the inner wall of the through hole.
Particularly, when assembling the thermal module, the feeding hole is located above the through hole, the joint material flows downward along the clearance, and the clearance gradually narrows along a flowing direction of the joint material.
According to a third embodiment of the invention, a method for assembling the thermal module is provided to combine a cooling fin with a heat pipe and a joint material. The method includes the following steps. A plurality of fins is made. As mentioned above, each fin has a through hole and a feeding hole communicating with each other.
Then, the heat pipe is made to pass through the through holes of the fins, and the feeding hole is made to be above the through hole. A clearance between the heat pipe and the inner wall of the through hole gradually narrows downward. Finally, the joint material is injected into the feeding hole to fill the clearance between the heat pipe and the inner wall of the through hole, thus to allow the joint material to flow downward along the clearance.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional schematic diagram showing a thermal module according to the prior art;

FIG. 2A is a three-dimensional schematic diagram showing a thermal module according to the prior art;

FIGS. 2B to 2D are sectional schematic diagrams showing the thermal module in FIG. 2A along a line O-O;

FIGS. 3A to 3C are schematic diagrams showing a fin according to one embodiment of the invention;

FIG. 4 is a flowchart showing a method for assembling a thermal module according to one embodiment of the invention;

FIGS. 5A to 5E are schematic diagrams showing the thermal module in each step in FIG. 4;

FIG. 6A is a schematic diagram showing a fin and a heat pipe in FIG. 5E along a direction F;

FIG. 6B is a schematic diagram showing a fluid located between two gradually approaching walls;

FIG. 7A is a three-dimensional schematic diagram showing a thermal module according to one embodiment of the invention; and

FIG. 7B is a sectional schematic diagram showing the thermal module in FIG. 7A along a line P-P.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a cooling fin, a thermal module including the cooling fin, and a method for assembling the thermal module.
According to one embodiment of the invention, the cooling fin can be combined with a heat pipe and a joint material, thus to form the thermal module. FIGS. 3A to 3B are schematic diagrams showing a fin according to one embodiment of the invention. Please refer to FIGS. 3A to 3C.
In FIGS. 3A to 3C, a main body 100 of a cooling fin 10 is flat, and the main body 100 has a through hole 102 and an feeding hole 104. The through hole 102 can be used for the heat pipe (not shown) to pass through. The feeding hole 104 communicates with the through hole 102. When the cooling fin 10 is combined with the heat pipe, the feeding hole 104 is above the through hole 102, and the joint material (not shown) is injected into the feeding hole 104 to fill a clearance between the heat pipe and the inner wall of the through hole 102. In addition, the through hole 102 has a first end portion 102 a and a second end portion 102 b opposite to each other. The feeding hole 104 extends from the first end portion 102 a for containing the joint material (not shown). In one practical application, the joint material may be solder paste or other suitable materials.
In FIG. 3A, in one embodiment, the feeding hole 104 can be regarded as a extension portion of the through hole 102. Therefore, the feeding hole 104 is located at a vertical line L connecting the first end portion 102 a and the second end portion 102 b. Further, a width of the widest portion of the feeding hole 104 is equal to that of the widest portion of the through hole 102.
In FIG. 3B, in one embodiment, the feeding hole 104 is also located at a vertical line L connecting the first end portion 102 a and the second end portion 102 b. However, in this embodiment, a width of the widest portion of the feeding hole 104 is smaller than that of the widest portion of the through hole 102.
In FIG. 3C, in one embodiment, an angle between a central line C of the feeding hole 104 and a vertical line L connecting the first end portion 102 a and the second end portion 102 b is about 45 degrees. In one practical application, the feeding hole 104 may extend from a suitable position of the first end portion 102 a, such that the angle between the central line and the vertical line L connecting the first end portion 102 a and the second end portion 102 b may be between 0 to 45 degrees (such as 10, 20, or 30 degrees).
In addition, in one practical application, the shape of the feeding hole 104 can be adjusted according to needs, and it is not limited thereto. For example, the shape of the feeding hole 104 may be adjusted according to a used joint material, a needed moving speed of the joint material, needed capillary force and so on.
In one practical application, the main body 100 can further include a structure for helping heat dissipation or fastening, such as a bend, a protrusion, a recess, a fastening hole and so on. In addition, the appearance of the main body 100 can be changed and adjusted according to situations, and it is not limited to FIGS. 3A to 3C.
FIG. 4 is a flowchart showing a method for assembling a thermal module according to one embodiment of the invention. FIGS. 5A to 5E are schematic diagrams showing the thermal module in each step in FIG. 4. Please refer to FIG. 4 and FIGS. 5A to 5E together. To clearly describe this embodiment of the invention, only one cooling fin is shown from FIGS. 5A to 5E. In one practical application, the number of the cooling fin may increase or decrease according to needs. In FIG. 4, the method for assembling the thermal module includes the following steps.
In step S50, a heat pipe 12 and a cooling fin 10 as shown in FIG. 5A are made. The cross-section of the heat pipe 12 is flat. In one practical application, the cross-section of the heat pipe 12 may have other shapes. In addition, as described above, a main body 100 of the cooling fin 10 has a through hole 102 and an feeding hole 104. The through hole 102 has a first end portion 102 a and a second end portion 102 b opposite to each other, and the feeding hole 104 extends from the first end portion 102 a.
In this embodiment, the feeding hole 104 of the made fin 10 is the same as that in FIG. 3B. However, in one practical application, the cooling fin having the feeding hole 104 as shown in FIG. 3A and FIG. 3C or having other suitable feeding holes may be made.
In step S52, the cooling fin 10 is sleeved on the heat pipe 12 via the through hole 102 as shown in FIG. 5B.
In step S54, the joint material 14 is injected into the feeding hole 104 (as shown in FIG. 5C). In one practical application, the joint material 14 may be solder paste or other suitable materials. In addition, in FIG. 5C, the joint material 14 is a bar-shaped solid. However, in one practical application, the joint material 14 may be a pasty solid or have other forms.
In step S56, the cooling fin 10 is disposed to keep the feeding hole 104 above the through hole 102 (as shown in FIG. 5D). Particularly, a clearance between the heat pipe 12 and the inner wall of the through hole 102 gradually narrows downward. In one practical application, the cooling fin 10 may be disposed via a suitable holding device (not shown) to keep the above state. In addition, if the joint material 14 is a pasty material or other materials having high liquidity, the cooling fin 10 can be disposed as shown in FIG. 5D in step S52 or S54.
Finally, in step S58, the joint material 14 is made to flow downward along the clearance to tightly combine the cooling fin 10 and the heat pipe 12.
In one practical application, when the joint material is solder paste, step S58 can further include the following steps. The solder paste is heated to be melted. Further, after the solder paste flows downward along the clearance and reaches the bottom of the through hole, the solder paste is cooled to tightly combine the cooling fin and the heat pipe.
In the method according to the embodiment of the invention, the joint material flows downward and is uniformly distributed to the clearance between the heat pipe and the through hole via capillarity and gravity. In addition, the cooling fin is disposed to keep the feeding hole above the through hole. When the joint material flows from the first end portion of the through hole to the second end portion of the through hole along the clearance between the heat pipe and the through hole, the clearance between the heat pipe and a wall of the second end portion gradually narrows. Therefore, the capillary force can exist all the time, which is help for the joint material to fully fill the clearance between the heat pipe and the through hole.
To further describe the relation between gradually narrowing of the clearance and the capillary force, please refer to FIG. 6A and FIG. 6B. FIG. 6A is a schematic diagram showing the cooling fin 10 and the heat pipe 12 in FIG. 5E along a direction F. FIG. 6B is a schematic diagram showing a fluid 20 located between two gradually approaching walls 30, 32.
In FIG. 6A, the clearance between the heat pipe 12 and the through hole 102 gradually narrows along arrow directions at the second end portion 102 b of through hole 102. In addition, in FIG. 6B, it is supposed that an angle between the two walls 30, 32 is α, the contact angle between a liquid extending line of the fluid 20 and the two walls 30, 32 is θ, a curvature radius of the fluid 20 and an air interface at a lower side is R, and a distance between contacting points of the fluid 20 and the walls 30, 32 is H.
According to the following formula, in FIG. 6B, the capillary force ΔP is inversely proportional to the curvature radius R, where, σ is surface tension.
ΔP=2σ cos θ/R.
Further, as the clearance between the two walls 30, 32 gradually narrows, the following relation can be achieved according to α, θ, and H.
$R = \frac{H / 2}{\cos (θ - α)} \Rightarrow R \propto H$
In other words, the curvature radius R is directly proportional to the distance H. When the distance between the walls 30, 32 becomes smaller, the H becomes smaller, and the R also becomes smaller. Therefore, the ΔP becomes greater. As the clearance between the heat pipe and the through hole gradually narrows, the capillary force exists all the time, thus to allow the joint material to be capable of successfully filling the clearance between the heat pipe and the through hole.
FIG. 7A is a three-dimensional schematic diagram showing a thermal module according to one embodiment of the invention. FIG. 7B is a sectional schematic diagram showing the thermal module in FIG. 7A along a line P-P. Please refer to FIG. 7A and FIG. 7B together.
In FIG. 7A, a thermal module 1 includes a plurality of cooling fins 10 as mentioned above, a heat pipe 12, and a joint material 14. In addition, in this embodiment, the thermal module 1 further includes a fixture base 16 having a groove 160 for containing the heat pipe 12. In one practical application, the heat pipe 12 may be attached to or be fastened to the groove 160 via a fastening element.
In one practical application, the fixture base 16 is made of a material with a better heat dissipation effect (such as copper, alumina, alloy, or other suitable materials). The fixture base 16 can be fixed around a heating element (not shown) to allow the heat pipe 12 to approach the heating element, thus to quickly dissipate the heat generated by the heating element.
In FIG. 7B, according to the thermal module 1 assembled with the cooling fin 10 via the method provided by the embodiment of the invention, the joint material 14 can be uniformly distributed to the clearance between the through hole 102 and the heat pipe 12, and it does not deposit or overflow. The clearance between the through hole 102 and the heat pipe 12 in the figure is enlarged on purpose for showing clearly. In one practical application, the clearance may be adjusted according to needs and may conform to demands or standards on manufacture.
In one practical application, the thermal module can be applied to an electronic device such as a computer, a display, a light and so on for dissipating heat of a heating element in the electronic device such as a processor, a display chip, a graphic chip, a light-emitting diode and so on. In addition, the thermal module can include a plurality of heat pipes, or it can be combined with a fan, a heat dissipation plaster, a cooling fin, or other suitable elements for improving the heat dissipation effect.
To sum up, the joint material can be uniformly distributed to the clearance between the edge of the through hole and the heat pipe via the feeding hole and disposing the cooling fin to keep the feeding hole above the through hole during manufacture, thereby tightly combining the cooling fin and the heat pipe and improving the heat dissipation effect. In addition, according to the method provided by the embodiment of the invention, the situation that the joint material deposits or overflows in the prior art can be avoided.
Although the present invention has been described in considerable detail with reference to certain preferred embodiments thereof, the disclosure is not for limiting the scope of the invention. Persons having ordinary skill in the art may make various modifications and changes without departing from the scope and spirit of the invention. Therefore, the scope of the appended claims should not be limited to the description of the preferred embodiments described above.

Claims

1. A cooling fin combined with a heat pipe and a joint material, the cooling fin comprising:

a main body having a through hole and an feeding hole, the heat pipe passing through the through hole, the feeding hole communicating with the through hole, the joint material injected into the feeding hole to fill a clearance between the heat pipe and the inner wall of the through hole;

wherein when the cooling fin is combined with the heat pipe, the feeding hole is above the through hole, the joint material flows downward along the clearance, and the clearance gradually narrows along a flowing direction of the joint material.

2. The cooling fin according to claim 1, wherein a cross-section of the heat pipe is flat.

3. The cooling fin according to claim 1, wherein the through hole has a first end portion and a second end portion, and the feeding hole is located at a vertical line connecting the first end portion and the second end portion.

4. The cooling fin according to claim 1, wherein the through hole has a first end portion and a second end portion, and an angle between a central line of the feeding hole and a vertical line connecting the first end portion and the second end portion is between 0 to 45 degrees.

5. The cooling fin according to claim 1, wherein a width of the feeding hole is equal to that of the through hole.

6. The cooling fin according to claim 1, wherein the joint material is solder paste.

7. A thermal module comprising:

a heat pipe;

a joint material; and

a plurality of cooling fins, each cooling fin including a main body, the main body having a through hole and an feeding hole, the heat pipe passing through the through hole, the feeding hole communicating with the through hole, the joint material injected into the feeding hole to fill a clearance between the heat pipe and the inner wall of the through hole;

wherein when the thermal module is assembled, the feeding hole is located above the through hole, the joint material flows downward along the clearance, and the clearance gradually narrows along a flowing direction of the joint material.

8. The thermal module according to claim 7, wherein a cross-section of the heat pipe is flat.

9. The thermal module according to claim 7, wherein the through hole has a first end portion and a second end portion, and the feeding hole is located at a vertical line connecting the first end portion and the second end portion.

10. The thermal module according to claim 7, wherein the through hole has a first end portion and a second end portion, and an angle between a central line of the feeding hole and a vertical line connecting the first end portion and the second end portion is between 0 to 45 degrees.

11. The thermal module according to claim 7, wherein a width of the feeding hole is equal to that of the through hole.

12. The thermal module according to claim 7, wherein the joint material is solder paste.

13. The thermal module according to claim 7, further comprising:

a fixture base including a groove for containing the heat pipe and fastening the heat pipe to approach a heating element.

14. A method for assembling a thermal module to combine a fin with a heat pipe and a joint material, the method comprising the following steps of:

making a plurality of fins, each fin having a through hole and an feeding hole communicating with each other;

making the heat pipe pass through the through holes of the fins and making the feeding hole above the through hole;

injecting the joint material into the feeding hole to fill a clearance between the heat pipe and the inner wall of the through hole; and

making the joint material flow downward along the clearance, the clearance gradually narrowing along the flowing direction.

15. The method according to claim 14, wherein the fins are disposed via a holding device to keep the feeding hole above the through hole.

16. The method according to claim 14, wherein in the step of making the joint material flow downward along the clearance, the method further comprises the steps of:

heating the joint material to melt the joint material; and

cooling the joint material to solidify the joint material to tightly combine the cooling fins and the heat pipe after the joint material flows downward along the clearance to the bottom of the through hole.

17. The method according to claim 16, wherein the joint material is solder paste.

18. The method according to claim 14, wherein the through hole has a first end portion and a second end portion, and the feeding hole is located at a vertical line connecting the first end portion and the second end portion.

19. The method according to claim 14, wherein the through hole has a first end portion and a second end portion, and an angle between a central line of the feeding hole and a vertical line connecting the first end portion and the second end portion is between 0 to 45 degrees.

20. The method according to claim 14, wherein a width of the feeding hole is equal to that of the through hole.