WO2011105800A2

WO2011105800A2 - Heat sink including a heat-dissipation fin capable of vibrating

Info

Publication number: WO2011105800A2
Application number: PCT/KR2011/001252
Authority: WO
Inventors: 김성진; 박희승
Original assignee: 한국과학기술원
Priority date: 2010-02-23
Filing date: 2011-02-23
Publication date: 2011-09-01
Also published as: WO2011105800A3

Abstract

The present invention relates to a heat sink including a heat-dissipation fin capable of vibrating. The heat sink of the present invention comprises a piezoelectric device that is attached to a surface of a heat-dissipation fin for dissipating heat, wherein the piezoelectric device compresses or expands so as to vibrate the heat-dissipation fin. The same frequency as the natural frequency of the heat-dissipation fin can be inputted to the piezoelectric device. According to the present invention, since airflow is generated by the vibration of the heat-dissipation fin, the heat sink has good cooling performance without using a separate fan. Thus, a space for accommodating a fan in the heat sink is unnecessary.

Description

Heat sink with vibrating heat sink fins

The present invention relates to a heat sink having a vibrating heat dissipation fin, and more particularly, to a heat sink in which a heat dissipation fin vibrates due to contraction and expansion of a driving part on one side of a heat dissipation fin for dissipating heat. .

Recently, electronic products are rapidly becoming high performance according to the trend of high integration, high performance, and miniaturization of semiconductor chips and packages including the same. As electronic products become more efficient, a lot of heat is generated inside the operation. In particular, as the capacity of the CPU and the peripheral electronic components used in the electronics becomes relatively large, the heat generation amount is extremely increased.

Therefore, in order to operate electronic products stably, it is important to efficiently and quickly release the heat generated therein during operation. To this end, the interior of the electronics is equipped with a cooling device for dissipating heat. Looking at the conventional cooling device mounted inside the electronic products as follows.

First, the electronic chip cooling apparatus disclosed in Korean Unexamined Patent Publication No. 10-2004-52010 includes a terminal base that directly contacts a heating element such as a CPU and conducts heat, a heat pipe that is soldered on top of the terminal base, and a heat pipe. A heat dissipation block soldered to the end, a fan motor positioned at the center thereof to supply cooling fluid to the heat dissipation block, a base frame to which the fan motor and the terminal base are fixed, and a top center of the fan motor mounting portion of the base frame. It is made of a fan cover to block most except for allowing the cooling fluid to be efficiently introduced and discharged. Here, the fan cover formed under the installation line of the heat pipe is soldered to the heat pipe to integrate the heat cover, so that the heat cover can be used as a heat sink that conducts heat from the heat pipe and radiates heat in the air. The electronic chip cooling device transfers heat generated from a heating element such as a CPU to the heat pipe through the terminal base, and the heat transferred to the heat pipe is moved to the heat dissipation block formed at each end of the heat pipe and moved to the heat dissipation block. The heat causes forced convection by driving the fan motor to cool it.

In addition, the cooling device for computer parts presented in the Republic of Korea Patent No. 10-600448 is a device for cooling the heat generating parts that generate heat during operation of the parts built into the computer, so that the heat generated from the heat generating parts can be received At least one heat pipe and heat radiation fins of the heat pipe formed of a heat block that is tightly coupled to the heat generating parts, a heat block block portion coupled to the heat block to receive heat from the heat block, and a heat radiation fin coupling portion bent to form a curved shape. Is coupled to the coupling portion, it comprises a plurality of heat dissipation fins spaced apart from each other along the radiating fin coupling portion. The cooling device for the computer parts configured as described above serves to cool the heat by dissipating heat into the air from the parts other than the parts coupled to the heat block through the heat pipe when heat is transferred from the heat-generating electronic parts to the heat block. In addition, the plurality of heat dissipation fins allow the air flow generated by the cooling fan to pass through the heat dissipation fins so that the air flows to the outside of the cooling fan in a spiral manner to cool the computer components.

However, such a conventional cooling device is configured to apply an axial fan to introduce external air along the rotational axis of the fan to pass through the heat radiating fins and then to flow out in the axial direction. That is, the heat dissipation fins are cooled by an axial fan installed on the top of the heat dissipation fins through which heat is transmitted from a heat generating component such as a CPU. Cooling is sequentially performed through a plurality of heat-dissipating fins stacked below.

At this time, the wind generated from the axial fan has a problem of lowering the cooling efficiency due to the low wind strength by the interference of the heat radiation fins, and there is also a problem that the volume occupied by the fan reduces the heat transfer area so that heat transfer is not effectively performed.

Therefore, it is desired to develop a heat sink having excellent emission efficiency through effective heat transfer by increasing the heat transfer area without using an axial fan.

It is an object of the present invention to provide a heat sink that can effectively transfer internal heat to the outside without using an axial fan.

The present invention to achieve the above object is a heat radiation fin for dissipating heat; And a driving unit attached to one side of the heat dissipation fins and repeating contraction and expansion to vibrate the heat dissipation fins.

The present invention also provides a base; A plurality of heat dissipation fins spaced apart from each other and attached to the base, for dissipating heat; And a driving unit attached to one side of the heat dissipation fins and repeating contraction and expansion to vibrate the heat dissipation fins.

In another aspect, the present invention provides a heat sink having a vibrating heat dissipation fin, characterized in that the drive unit is a piezoelectric element.

In another aspect, the present invention provides a heat sink having a vibrating heat sink fin, characterized in that the same frequency as the natural frequency of the heat sink fin is input to the piezoelectric element.

In the heat sink according to the present invention, the driving unit is attached to one side of the heat dissipation fin so that the driving unit vibrates the heat dissipation fin. The air flow is generated by the vibration, so the cooling performance is excellent even without a separate fan.

In addition, since the heat sink does not have to be equipped with a fan, there is no need for a separate space for the fan inside the heat sink. Therefore, the heat sink design can be made more free, and the size of the heat sink can be reduced.

1 is a view schematically showing a heat sink according to an embodiment of the present invention.

2 is a view showing a principle that the heat radiation fin of the heat sink according to an embodiment of the present invention vibrates.

3 is a view showing a heat sink combined with a heater and an insulation system according to an embodiment of the present invention.

4 shows that a heat sink coupled with a heater and a thermal insulation system is connected to another device.

5 is a diagram showing a comparison result between experimental data of the present invention and a related Bar-cohen equation.

6 is a diagram showing the thermal performance of the heat sink as a thermal resistance to the input frequency in the piezoelectric element having an input voltage of 24V.

7 is a graph illustrating a change in flow rate according to an input voltage.

8 is a graph showing a relationship between a thermal resistance of a heat sink having a piezoelectric element and an input voltage of the piezoelectric element.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, it should be noted that in the drawings, the same components or parts denote the same reference numerals as much as possible. In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

As used herein, the terms "about", "substantially", and the like, are used at, or in close proximity to, numerical values when manufacturing and material tolerances inherent in the meanings indicated are intended to aid the understanding of the invention. Accurate or absolute figures are used to assist in the prevention of unfair use by unscrupulous infringers.

As shown in FIG. 1, the heat sink 100 according to the embodiment of the present invention includes a heat dissipation fin 110, a base 120, and a driver 130.

The heat dissipation fin 110 is a portion that radiates heat. In the present embodiment, the heat dissipation fin 110 has a plate shape, but is not limited thereto and may have various shapes according to the use form or purpose. The heat dissipation fins 110 are plural and spaced apart from each other and attached to the base 120.

The base portion 120 fixes the heat dissipation fins 110 and is a portion for mounting the heat dissipation fins 110 to the heating element. Heat generated from the heating element is transferred to the heat dissipation fin 110 through the base 120.

The driver 130 is attached to one side of the heat dissipation fin 110. The drive unit 130 is capable of contraction and expansion. In this embodiment, the driving unit 130 is a piezoelectric element. The piezoelectric element contracts when a positive field is induced and expands when a negative field is induced. It is connected to the AC power supply 140 for the contraction and expansion of the piezoelectric element. The AC power supply 140 inputs AC into the piezoelectric element. Although the driving unit 130 is described as being a piezoelectric element in this embodiment, the present invention is not limited thereto and may be various members capable of vibrating the heat dissipation fin 110 through contraction and expansion.

The heat dissipation fin 110 vibrates by contraction and expansion of the driving unit 130. When the heat dissipation fin 110 vibrates, a boundary layer of air around the heat dissipation fin 110 is disturbed, thereby increasing cooling performance. In addition, since the air around the heat radiating fins 110 is moved by the vibration of the heat radiating fins 110, the air around the heat radiating fins 110 is discharged into the atmosphere without a device such as a fan for generating air flow. Therefore, the heat sink 100 according to the present embodiment has a higher cooling performance than a heat sink that does not use a conventional fan, and has the same or superior cooling performance as that of a heat sink using a fan. Since there is no need for space, there is an advantage to save space.

2 is a view showing a principle that the heat radiation fin of the heat sink with a piezoelectric element according to an embodiment of the present invention vibrates.

As shown in FIG. 2, the piezoelectric element 230 is attached to one side of the heat dissipation fin 210 of the heat sink 200 according to the embodiment of the present invention. Preferably, piezoelectric element 230 is attached to the end adjacent to base 220. The piezoelectric element 230 is connected to an AC power supply.

When a positive electric field is induced in the piezoelectric element 230 by the AC power supply device, as shown in FIG. 2A, the piezoelectric element 230 contracts. Since the piezoelectric element 230 is attached to one side of the heat dissipation fin 210, one side of the heat dissipation fin 210 is contracted by the contraction of the piezoelectric element 230 and the other side is not changed. Therefore, the heat dissipation fin 210 is bent to one side to which the piezoelectric element 230 is attached.

When a negative electric field is induced in the piezoelectric element 230, as shown in FIG. 2B, the piezoelectric element 230 expands. Due to the expansion of the piezoelectric element 230, one side of the heat dissipation fin 210 expands and the other side thereof does not change. Therefore, the heat dissipation fin 210 is bent to the other side to which the piezoelectric element 230 is not attached.

When the positive and negative electric fields are repeatedly induced to the piezoelectric element 230 using the AC power supply in this manner, the piezoelectric element 230 repeats the contraction and expansion, and thus the heat dissipation fin 210 is fanned. Similar vibrations will occur. In this case, inputting the same frequency as the natural frequency of the heat dissipation fin 210 into the piezoelectric element 230 increases the vibration of the heat dissipation fin 210 by resonance, thereby improving cooling performance.

An experiment was performed to measure the thermal performance of a heat sink according to an embodiment of the present invention. The heat sink for the experiment is the shape of an optimized natural convection heat sink, and this natural convection heat sink optimization was performed based on Bar-cohen's research. The width, length and fin height of the base of the heat sink were fixed and the fin thickness and the optimal channel width between fins were obtained through iteration. The shape of the heat sink is shown in the table below and the temperature of the heat sink was measured with three J-type thermocouples.

Table 1

Material	Aluminum 6061
Base width	39.5 mm
Base length	38 mm
Fin height
	40 mm
Fin thickness	300 μm
Channel width between fins	5.3 mm

3 is a view showing a heat sink coupled to a heater and a thermal insulation system according to an embodiment of the present invention, Figure 4 is a view showing a heat sink coupled to the heater and the thermal insulation system is connected to another device.

The heater is manufactured to about 0.025mm and is connected to the DC power supply. Direct current is applied to the heater and a constant heat flux boundary condition is generated. The heat generated by the heater is controlled by the current of the DC power supply and the electrical resistance of the heater. The insulation system is made of Teflon to reduce unwanted heat losses. However, the thermal insulation system could not completely prevent heat loss, so the heat loss was measured with six J-type thermocouples. Therefore, the experiment as combined as shown in Figure 3 can be confirmed that the heat is transferred to the heat transfer through the heat sink is not transferred to other places, through which the heat transfer performance of the heat sink can be seen.

The function generator (Stanford Research System, DS340) generates sinusoidal signals of various frequencies, which are then passed to the AC power supply. An AC power supply is a power source for applying AC power to a piezoelectric element. The input frequency is controlled by the function generator and the input voltage is controlled by the AC power supply.

The difference between the heat in the heater and the heat loss in the insulation system is the heat input to the heat sink. The temperature of the heat sink is also measured by a J-type thermocouple, which is connected to a digital data acquisition system (Agilent, 34970A). In experiments to measure the heat performance of a heat sink, it is important to establish a steady state to eliminate transient effects. When the base temperature of the heat sink and the temperature of the thermal insulation system change to less than 0.1 ° C, it can be regarded as a stable state. 0.1 ° C is the limit of analysis of the digital data capture system used in the experiment. It took about 2 hours to become stable and all measurements were performed after 2 hours. Verification of heat loss was performed using a natural convection heat sink. There are many studies on the thermal performance of natural convection heat sinks, and the Bar-cohen equation is used for verification.

5 is a diagram showing a comparison result between experimental data and a Bar-cohen equation of the present invention.

As shown in FIG. 5, the experimental data of the present invention is consistent with Bar-cohen's equation within ± 10%. The thermal performance of the heat sink can thus be measured well with the experimental equipment used in the present invention.

The vibration frequency of the heat sink coincides with the input frequency of the piezoelectric element. The thermal performance of the heat sink increases as the input frequency increases because the vibration speed increases as the vibration frequency increases. However, cooling performance increases significantly at special input frequencies due to resonance. The oscillation width is amplified by the resonance and the thermal performance is also amplified.

FIG. 6 shows that optimal frequency input is important in piezoelectric elements to maximize the thermal performance of a heat sink having heat sink fins with piezoelectric elements mounted thereon. Also, the optimum input frequency is the natural frequency of the heat sink fins of the heat sink.

The shape of the heat sink is similar to the cantilever beam, and the natural frequency of the cantilever beam can be obtained by the following equation (1).

In Eq. (1), G is a proportionality constant, which is determined experimentally. Y is the Young's modulus, ρ is the density, and σ is the Poisson's ratio, which is a property of the material of the cantilever beam. When the property values are fixed, the natural frequency is determined by the shape of the cantilever beam, the thickness t of the fin and the height H of the heat sink fin. If the input frequency is fixed, it is necessary that a heat sink based on Equation (1) be manufactured to produce a natural frequency of the heat sink fin that matches the input frequency.

7 is a graph illustrating a change in flow rate according to an input voltage.

As shown in FIG. 7, it can be seen that the flow rate is proportional to the input voltage of the piezoelectric element in the case of the heat sink having the heat dissipation fin to which the piezoelectric element is attached. As the flow rate increases, the thermal resistance of the heat sink with heat sink fins with piezoelectric elements decreases.

The input frequency of the piezoelectric element matches the natural frequency of the heat sink fins. In FIG. 8, the thermal resistance of the heat sink having the heat dissipation fin to which the piezoelectric element is attached is inversely proportional to the input voltage. This means that the thermal resistance is inversely proportional to the flow rate generated.

In FIG. 8, the points on the thermal resistance axis represent the thermal resistance of the optimal natural convection heat sink without the piezoelectric element. The thermal resistance of the natural convection heat sink decreases as the heat transferred from the heater is reduced.

FIG. 8 shows that the thermal performance of the heat sink with the heat dissipation fin to which the piezoelectric element is attached is more than twice as large as that of the natural convection heat sink, and the rate of increase of the thermal performance may be increased as the input voltage is increased.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

Reference

[1] A. Bar-Cohen, M. Iyengar and A.D. Kraus, Design of optimum plate-fin natural convective heat sinks, J. Electronic Packaging 125 (2003) 208-216

Claims

Heat dissipation fins for dissipating heat; And

And a driving unit attached to one side of the heat dissipation fin and repeating contraction and expansion to vibrate the heat dissipation fin.
Base;

A plurality of heat dissipation fins spaced apart from each other and attached to the base, for dissipating heat; And

And a drive unit attached to one side of the heat dissipation fin and repeating contraction and expansion to vibrate the heat dissipation fin.
The method according to claim 1 or 2,

And the driving unit is a piezoelectric element.
The method of claim 3,

The piezoelectric element is a heat sink having a vibrating radiating fin, characterized in that the same frequency as the natural frequency of the radiating fin is input.