KR101240250B1

KR101240250B1 - Flat type heat spreader

Info

Publication number: KR101240250B1
Application number: KR1020100087131A
Authority: KR
Inventors: 김성진; 윤영직; 이정석
Original assignee: 한국과학기술원
Priority date: 2010-09-06
Filing date: 2010-09-06
Publication date: 2013-03-11
Also published as: KR20120024292A

Abstract

The present invention relates to a flat heat spreader for cooling an electronic device by dissipating heat generated in the electronic device to the outside, and a manufacturing apparatus thereof, a body made of a plate-shaped resin material, and a closed loop inside the body. It provides a channel in which the hollow in the form is formed in a zigzag or spiral shape.

Description

Flat Heat Disperser {FLAT TYPE HEAT SPREADER}

The present invention relates to a flat heat spreader that cools an electronic device by releasing heat generated from the electronic device to the outside.

As the line width of the electronic circuit constituting the semiconductor device becomes smaller, the number of devices per unit area increases. However, with this, the heat dissipation rate per unit area of the semiconductor chip is further increased, and this increase in heat dissipation rate decreases the performance and lifespan of the semiconductor device and ultimately reduces the reliability of the electronic device employing the semiconductor device. . In particular, in the semiconductor device, various parameter values are sensitively changed according to the operating temperature, thereby deteriorating the characteristics of the integrated circuit even more.

As the heat dissipation rate is increased, cooling technologies have been developed a lot, such as fin fan cooling, thermoelectric cooling, water-jet cooling, immersion cooling, Heat pipe cooling.

Generally, computer coolers are mainly concentrated on heat sources such as CPU, VGA card, chips, and boards. Such computer coolers cool heat from heat sources through heat pipes. In the cooling unit, a fin is installed to remove the high temperature heat of the heat source with a fan.

As described above, a heat pipe is used as a heat transfer medium in a conventional computer cooling device. The heat pipe is a round pipe, and absorbs high temperature heat by using latent heat of evaporation of a liquid refrigerant in contact with a heat source. And an evaporation unit for evaporating the refrigerant into a gas phase, a heat insulation unit for forming a refrigerant movement, and a condensation unit for cooling the gaseous refrigerant by a fan to condense it into a liquid phase, and a wick is inserted therein.

The wick includes a screen mesh, a sintered metal, a groove, and the like, and are used differently depending on the purpose and purpose of use. Such a wick causes the refrigerant vapor generated in the evaporator of the heat pipe to move to the condenser by the internal pressure difference, and the refrigerant liquid condensed by the external air cooling in the condenser is evaporated again by capillary force. Let's circulate to wealth.

1 illustrates a cylindrical heat pipe of a general wick structure. The heat pipe 10 includes an inner space 11 through which a gaseous refrigerant moves, and a porous medium 15 having a wick structure through which a liquid phase refrigerant moves.

One of the heat pipes 10 is an evaporator in contact with a heat source, and the other is a condenser for condensing evaporated vapor.

The arrow inside the heat pipe 10 indicates the movement of the refrigerant. The gaseous refrigerant is moved to the condensation unit through the internal space 11, and the gaseous refrigerant introduced into the condensation unit is phase-changed to give a liquid phase. Becomes a refrigerant. The liquid refrigerant soaks into a porous material 15 provided on the inner surface of the heat pipe 10.

The liquid refrigerant that has soaked into the porous medium 15 is moved back to the evaporation part by a capillary action of the porous medium 15.

Such cylindrical heat pipes can be used in ultra-slim electronic products, such as notebook computers, where the heat pipes are pressed to make the cylindrical heat pipes thinner. In addition, it must be bent in order to increase the fan heat transfer area of the condensation unit. However, in the state where the cylindrical heat pipe is pressed and the thickness thereof is not easy to bend, even if it is bent, the wick droop occurs in the inner surface of the pipe, and the shape is physically deformed, so that the smooth refrigerant cannot be moved. The performance of the heat pipe may be degraded.

In addition, when the groove is applied to the ultra-slim heat pipe, there is a problem that the micro-machining of the groove is difficult and the processing cost is high. When the mesh screen is applied to the wick structure of the ultra-slim heat pipe, as the wick layer becomes thinner, the flow pressure drop increases, and the surface tension of the refrigerant is weakened because the pore size is not constant. As a result, the cooling efficiency for the heating element is lowered.

Therefore, the heat pipe used in the conventional computer cooling device is not only difficult to manufacture, but also has a large limitation in the use position and shape thereof, which makes it difficult to use in various forms.

The present invention is to provide a flat heat disperser in which a single channel closed loop is formed in a resin body using a three-dimensional rapid prototyping system (RP), thereby realizing a cooling device in a thin film form.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not intended to limit the invention to the particular embodiments that are described. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, There will be.

Flat heat spreader of the present invention for achieving the above object, the body made of a plate-shaped resin material; And a channel in which the hollow of the closed loop shape is formed in a zigzag or spiral shape in the body.

The channel is characterized in that a single channel of the closed loop form, the height of the body is about 1mm to 2mm, the height and width of the channel is characterized in that about 0.5mm to 1mm.

The resin is a photocurable resin, characterized in that the material of any one selected from polypropylene, polystyrene, polystyrene, polyamide, polycarmonate, polycarbonate, and polyphenylsulfone.

The channel may have the same width or vary based on the moving direction of the refrigerant.

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As described above, in the present invention, a single-channel closed loop is formed in the resin body by using a three-dimensional rapid prototyping system (RP) to form a thin film type heat spreader, so that the thickness of the heat spreader is thin and embedded in the electronic device. There is an advantage in that it is easy to do and does not need a lot of separate space for the heat spreader to provide a design convenience.

In addition, by inserting the thin film type heat spreader according to the present invention into an outer cover of an electronic device such as a mobile phone, a PDA, a smart phone, and the like, there is no need for a separate cooling device for the portable electronic device and its installation space, and thus the freedom of designing the electronic device. There is an advantage that can increase and also improve the reliability of the performance of the electronic device due to the cooling device.

1 is a cross-sectional view showing a cylindrical heat pipe of a general wick structure.
2 is a view showing an apparatus for manufacturing a flat heat spreader according to an embodiment of the present invention.
3A to 3D are views illustrating a manufacturing process of the heat spreader using FIG. 2.
4A and 4B are a plan view and a cross-sectional view showing a flat heat spreader according to an embodiment of the present invention.
5 is a plan view showing a flat heat spreader according to another embodiment of the present invention.
6 is a plan view showing a flat heat spreader according to another embodiment of the present invention.
7 is a view illustrating a heat absorption and heat dissipation process of the heat spreader according to the present invention.
8A and 8B are diagrams for explaining the relationship between the diameter of the channel and the gaseous and liquid refrigerant.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Like elements in the figures are denoted by the same reference numerals wherever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

2 is a view showing a manufacturing apparatus of a flat heat spreader according to an embodiment of the present invention, the manufacturing apparatus 100 is an elevator 110, a laser 120, a horizontal moving means 130, a vertical moving means ( 140, and a controller 150.

The elevator 110 is vertically moved in the container 50 in which the photocurable resin 55 is stored, and the plate-shaped platform 115 is seated on the part immersed in the resin 55. The platform 110 is mounted on the elevator 110, and the heat spreader 200 using the photocurable resin 55 is manufactured at the upper end of the platform 115.

In the container 50, a photocurable resin 55 is stored, and the photocurable resin 55 is made of polypropylene and polystyrene, polystyrene, polyamide, polycarmonate, polycarbonate and polyphenylsulfone. It may be any one material selected from among.

The laser 120 is configured to cure the photocurable resin 55 of a predetermined thickness by scanning UV rays to the surface of the resin present in the area of the platform 115 of the elevator 110.

The horizontal moving unit 130 moves the laser 120 horizontally according to a predetermined control signal. Although not shown in detail, the horizontal movement means 130 may be configured to include a support for fixing the laser 120, and a motor for horizontally moving the support.

The vertical movement means 140 moves the elevator 110 vertically by a predetermined control signal according to the scanning of the laser 120. The vertical movement means 140 may be configured to include a support for holding and supporting the elevator 110, a motor for moving the support vertically.

The controller 150 controls the horizontal movement means 130 and the vertical movement means 140 according to the pattern data for the heat spreader stored in the memory 160 so that the photocurable resin 55 is cured into a set shape. Thus, the heat spreader 200 is manufactured. The controller 150 controls the elevator 110 to move at a distance set downward from the surface of the resin 55.

The set distance is the same as the thickness of the photocurable resin 55 is cured by the laser 120, in the embodiment the vertical movement distance of the elevator 110 may be about 0.05mm to 0.75mm.

In this case, the laser 120 selectively scans the liquid photo-sensitive resin 55 stored in the container 50 to solidify the surface of the resin having a predetermined thickness in contact with the light beam. In this case, the thickness of the resin 55 cured by the laser 120 may vary depending on the power of the laser 120.

The heat spreader 200 manufactured in this manner is manufactured on the platform 115 of the elevator 110, and when a cross-sectional shape of one layer is generated, the controller 150 moves the elevator 110 through the vertical movement means 140. After moving vertically downward, the laser 120 is again scanned onto the resin surface to form the next layer.

As such, the manufacturing apparatus 100 receives pattern data corresponding to a cross section having a fine thickness obtained from the original modeling data from the outside, and stores the pattern data in the memory 160, and the controller 150 according to the pattern data stored in the memory 160. UV rays of a specific wavelength are scanned horizontally (x-axis, y-axis) on the liquid surface of the photocurable resin 55, and the corresponding micro-thickness is continuously solidified and laminated on the z-axis, corresponding to the desired heat spreader 200. Produce a three-dimensional solid shape.

3A to 3D are views illustrating a manufacturing process of the heat spreader using FIG. 2, which will be described with reference to FIG. 2.

First, the controller 150 controls the vertical movement means 140 to move the elevator 110 to an initial position as shown in FIG. 3A, and then controls the horizontal movement means 130 to control the laser 120 with the preset x axis. Move it on the y axis. Accordingly, the laser 120 cures the resin 55 to a predetermined thickness while scanning UV rays onto the resin surface to form the lower layer 210. The laser 120 then scans the UV light only into the resin 55 in the region of the platform 115 seated on top of the elevator 110. In FIG. 3A, the lower layer 210 of the heat spreader 200 is formed.

As such, when the lower layer 210 of the heat spreader is completed, the controller 150 lowers the elevator 110 downward by a predetermined height through the vertical movement means 140 as shown in FIG. 3B. Subsequently, the controller 150 controls the horizontal moving means 130 to move the laser 120 in a predetermined x-axis and y-axis so that the resin 55 is cured in a predetermined shape to form the partition wall 230. . The controller 150 may adjust the scanning pattern of the laser 120 through the horizontal moving unit 130 to manufacture and harden the resin 55 into the partition wall 230 having a desired shape. In FIG. 3B, the partition wall 230 is formed on the top of the lower layer 210 to form a single channel having a closed loop.

When the partition wall 230 of the heat spreader 200 is formed as described above, the controller 150 controls the vertical moving unit 140 as shown in FIG. 3C to lower the elevator 110 downward by a predetermined height. Subsequently, the controller 150 controls the horizontal moving means 130 to cure the resin 55 to a predetermined shape while moving the laser 120 on a predetermined x-axis and y-axis to form the upper layer 250. In FIG. 3C, the upper layer 250 of the heat spreader 200 is formed.

That is, when UV rays are scanned on the top surface of the partition wall 230, the resin 55 on the top surface of the partition wall 230 is cured to automatically form the top layer 250 of the heat spreader 200.

Herein, the controller 150 may repeatedly control the above steps several times according to the heights of the lower layer 210, the partition wall 230, and the upper layer 250 of the heat spreader 200.

Through this process, the heat spreader 200 made of the photocurable resin 55 is manufactured as shown in FIG. 3D. The heat spreader 200 includes a body 210, 230, and 250 made of a plate-shaped resin material, and a channel 270 in which a closed loop hollow is formed in a zigzag or spiral shape. have.

That is, the body of the heat spreader 200 is composed of a lower layer 210, a partition wall 230 and an upper layer 250, a single channel 270 of the closed loop form in which a refrigerant flows is formed between the partition wall 230. do.

When manufacturing the heat spreader 200 in the above, it is preferable to form a refrigerant inlet 290 for extracting the liquid resin 55 in the channel 270 to the outside or injecting the refrigerant into the channel in advance. At least one coolant injection hole 290 may be formed.

When the heat spreader 200 is completed as described above, the uncured resin and wax are removed, the heat spreader 200 is separated from the platform 115, and the uncured resin 55 in the channel 270 is refrigerant. After the injection port 290 is subjected to a post-processing process to be extracted to the outside. After the post-treatment process, the refrigerant is injected into the channel 270 of the heat spreader 200 through the refrigerant inlet 290, and then the refrigerant inlet 290 is sealed.

In FIGS. 3A to 3D, the SLA (Stereo Lithography Apparatus) technique, which is one of rapid 3D rapid prototyping systems, was used to manufacture the heat spreader 200, but in addition, the FDM technique was used. It is obvious that the heat spreader 200 may be manufactured by applying the SLS (Selective Laser Sintering), the Solid Ground Curing (SGG), the Laminated Object Manufacturing (LOM), and the Zephyr Recoating System (3D). .

4A and 4B are a plan view and a cross-sectional view showing a flat heat spreader according to an embodiment of the present invention.

As shown in FIG. 4A, the heat spreader 200 includes a lower layer 210, a partition wall 230, an upper layer 250, a channel 270, and a refrigerant inlet 290.

The lower layer 210 and the upper layer 250 are integrally formed through the partition wall 230.

A capillary channel 270 is formed in the form of a closed loop through the partition wall 230 between the lower layer 210 and the upper layer 250.

At least one coolant inlet 290 is formed to inject coolant into the channel 270 in a portion of the lower layer 210 or the upper layer 250. In the embodiment, the refrigerant inlet 290 is shown in the upper layer 250.

In the above, the refrigerant may be injected about 30% to 60% of the volume of the channel 270. Here, when the amount of refrigerant injected is less than 30%, the amount of heat transfer medium (refrigerant) decreases, and thus the heat transfer efficiency is decreased. When the amount of refrigerant injected is 60% or higher, there is less space left for the refrigerant to pulsate, so the heat transfer efficiency may be decreased. .

Here, a variety of refrigerants may be used, for example, water, ethanol, ammonia, acetone, R-134a, HFC-based refrigerant may be used. In the case of water or ethanol, the heat capacity is large, which is advantageous as a refrigerant material because it can transfer a large amount of heat.

The channel 270 is a single channel in the form of a closed loop as shown, and may be configured in a zigzag or meander or spiral form.

As shown in FIG. 4B, the channel 270 is formed as a groove having a predetermined width and height in the lower layer 210, and the channel 270 is formed in a rectangular shape. Of course, the groove of the channel 270 may be formed in a circular shape if necessary.

In an embodiment, the total thickness t of the heat spreader 200 is about 1 mm to 2 mm, the height of the channel, that is, the height h of the partition 230 is about 0.5 mm to 1 mm, and the channel 270 has a width ( w) is also about 0.5 mm to 1 mm. Of course, each dimension t, h, w of the heat spreader 200 can be varied as needed.

The heat spreader 200 configured as described above absorbs heat radiated from the electronic parts by being in contact with the electronic component as the evaporator 201, and the other side becomes the condensing unit 205 and is transferred through the refrigerant. Heat is released to the outside. Therefore, the evaporator 201 may be at least one, and the remaining part except the evaporator 201 becomes the condenser 205.

FIG. 5 is a plan view showing a heat spreader according to another embodiment of the present invention, and FIG. 5 has a different shape of the channel 270 compared to FIG. 4.

That is, the channel 270 is formed in the form of a closed loop between the lower layer 210 and the upper layer 250, and the width formed is variable along the refrigerant moving direction.

The channel 270 is a single channel in the form of a closed loop as shown, and may be configured in a zigzag or meander or spiral form. The width of the channel 270 has a tapered shape that is widened from one side to the other side.

Here, the width of the channel 270 is configured to widen from the evaporator 201 to the condensation unit 205 based on the movement direction of the refrigerant, and has the same width from the condenser 205 to the evaporator 201. . In the present invention, the reason for varying the width of the channel 270 is that the narrower the pressure is higher than the wide area, the refrigerant is pumped (pumping) from the narrow place to the wide place to move the refrigerant, that is heat transfer Because it is faster than this.

FIG. 6 is a plan view illustrating a heat spreader according to another embodiment of the present invention. In FIG. 6, the width of the channel 270 is not changed along the moving direction of the refrigerant as shown in FIG. The channel is different in width. That is, the heat spreader 200 has different widths of adjacent channels based on the partition wall 230.

For example, when the width of the first channel is wide, the second channel adjacent to the first channel is narrower than the first channel, the third channel is wider than the adjacent second channel, and the fourth channel is adjacent to the third channel. It is formed in a way narrower than the channel.

As described above, when heat is applied to one side of the channel group, that is, the evaporator 201, the refrigerant in the gaseous phase located in the evaporator 201 is expanded to increase the pressure. The refrigerant in the gas phase of the evaporator 201 having an increased pressure causes a force to push the adjacent refrigerant in the liquid phase and moves toward the condenser 205 having a low pressure. The refrigerant absorbing heat from the evaporator 201 reaches the condenser 205 to release heat and returns to the evaporator 201 along another connected channel 270.

The refrigerant returned to the evaporator 201 again absorbs heat, expands, increases pressure, and moves in the opposite direction of the channel 270 to reach the condenser 205. This process is repeated repeatedly so that the heat may be continuously transferred between the evaporator 201 and the condenser 205 while the refrigerant periodically vibrates.

When the heat spreader 200 is embedded in the cover as described above, the inner surface of the cover contacts the electronic component that generates a lot of heat to form the evaporation unit 201. Part 205 is achieved.

As such, when the heat spreader 200 is inserted into the outer cover of the electronic device, a separate space for the heat spreader 200 is not required, thereby minimizing the size of the electronic device.

In addition, the heat spreader 200 may be fixedly installed at upper and lower ends of a circuit board or an electronic component (for example, a CPU or a communication module) to cool the electronic component.

The heat spreader 200 configured as described above has a thermal conductivity somewhat variable depending on the size or thickness (usually the smaller the thickness, the smaller the value), but is about 20 ⁵ W / mK. This is superior to the thermal conductivity of aluminum (237 W / mK), copper (401 W / mK) and diamond (2300 W / mK).

FIG. 7 is a view illustrating an endothermic and heat dissipation process of a heat spreader according to the present invention. One side of the channel group is an evaporator, and the other side of the channel group is a condenser.

When heat is applied to the evaporator, the refrigerant in the gas phase located in the evaporator expands according to the endothermic reaction, thereby increasing the pressure. That is, the control volume (c.v.) of the evaporator is expanded by the endothermic reaction.

The gaseous refrigerant in the evaporator at the increased pressure induces a force to push the adjacent liquid refrigerant to the condenser at a lower pressure. In FIG. 3, the second refrigerant located in the evaporator is moved to the condenser by the inspection volume. The test volume moved to the condensation unit radiates heat absorbed to the outside. As a result, the test volume is contracted again.

The refrigerant absorbing heat from the evaporator reaches the condenser and releases heat and returns back to the evaporator along another connected channel. The refrigerant returned to the evaporator again absorbs heat and expands to increase the pressure, which then moves in the opposite direction of the channel to reach the condenser. This process is repeated repeatedly so that the refrigerant flows periodically while pulsating and heat can be continuously transferred between the evaporator and the condenser.

8A and 8B are diagrams for explaining the relationship between the diameter of the channel and the gaseous phase and the liquid refrigerant. When the diameter (D) of the channel 270 is greater than the critical diameter (D _crit ), as shown in FIG. As a result, a liquid refrigerant and a vapor phase refrigerant exist separately, so that a pulsating action like the present invention does not occur. Here, the diameter (D) includes both the width and height of the channel 270.

However, if the diameter D of the channel 270 is smaller than the critical diameter D _crit (meaning the maximum allowable diameter), the liquid phase and the gas phase are alternately present in the channel 270 as shown in FIG. 8B. When radiating heat, the same action as in FIG. 7 occurs.

Here, the critical diameter D _crit of the channel 270 according to the refrigerant is determined by Equation 1 below, and the critical diameter D _crit varies according to the type of the refrigerant.

here,

Is the acceleration of gravity,

Is the liquid phase density of the refrigerant,

Is the gas phase density of the refrigerant,

Is the surface tension of the refrigerant.

Therefore, the critical diameter D of the channel 270 is determined by Equation 1, and the diameter of the actual channel 270 should be smaller than the critical diameter. For example, was the critical diameter (D _crit) it is less than 5mm the case of water, for a critical diameter (D _crit) of ethanol is set to be smaller than 3mm. In general, refrigerants have a critical diameter (D _crit ) in the range of 2 mm to 5 mm.

The larger) is, the larger the critical diameter is.

In addition, the minimum diameter of the channel 270 may be a micrometer unit, and when the diameter of the channel 270 is larger than the micrometer unit, a pulsating action as shown in FIG. 7 occurs.

The heat spreader 200 configured as described above may be inserted into a cover or case of an electronic device such as a mobile phone, a smart phone, a PDA, a palmtop, a notebook, and the like, and may be manufactured integrally with the cover.

The present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

110: elevator 115: platform
120: laser 130: horizontal movement means
140: vertical movement means 150: control unit
200: heat spreader 201: evaporator
205: condensation unit 210: lower layer
230: partition 250: upper layer
270: channel 290: refrigerant inlet

Claims

A body made of a plate-shaped resin material; And
And a hollow loop of a closed loop shape formed in the body in a zigzag or spiral shape.
The height of the body is about 1mm to 2mm, the height and width of the channel is about 0.5mm to 1mm,
30% to 60% of the volume of the refrigerant is injected into the channel.
Wherein said resin is a photocurable resin and is a material of any one selected from polypropylene and polystyrene, polystyrene, polyamide, polycarmonate, polycarbonate and polyphenylsulfone.

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The method according to claim 1,
And said channel is a single channel in the form of a closed loop.

The method according to claim 1,
Said channel having the same width.

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The method according to claim 1,
The width of the channel is a flat heat spreader that is variable based on the moving direction of the refrigerant.

The method according to claim 1,
The critical diameter (D _crit ) of the channel is determined by the following equation, the critical diameter (D _crit ) is a flat heat spreader that varies depending on the type of refrigerant.
Equation

only,

Is the acceleration of gravity,

Is the liquid phase density of the refrigerant,

Is the gas phase density of the refrigerant,

Is the surface tension of the refrigerant.

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