JPS5888593A - Heat pipe type radiator - Google Patents

Abstract

PURPOSE:To permit sufficient heat dissipation by small sized fins by a method wherein a bellows is utilized as the container of the heat pipe and a cord-like wick is intersected with the group of grooves orthogonally, in the small sized radiator for the substrate of a semi-conductor circuit. CONSTITUTION:The container 11 is consists of the bellows utilized for the heat dissipating fins in combination and will never buckle by a high vacuum even through the thickness thereof is made very thin. Accordingly, heat exchange between airstream and operating vapor may be effected in a very short period of time since it is effected through a thin container wall having 0.08-0.18mm.. The wick 14 is intersected with the grooves of the bellows by an elastic wick supporting body 16 and is pressingly supported along the transversal direction of the bellows, therefore, it maintains heat exchanging capacity. Further, the thicknesses of a heat absorbing surface 13 and a heat dissipating surface 12 are permitted to make them thin, since the container 11 is the bellows and the bellows itself can resist a high pressure. Thus, the thickness of the wall of the heat transmitting surface may be made thin, therefore, a sufficient heat dissipating effect and a sufficient interior volume may be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a heat radiator for cooling a heating element with an enlarged surface area and a small capacity. In particular, the present invention is designed to individually absorb the heat generated by a large number of semiconductor circuit chips that are assembled in parallel in a housing of an electronic device, etc. and are densely mounted on each of nine circuit boards, and dissipate the heat into the air flow to raise the temperature of the board. Improved frequency as a small capacity heat pipe, most suitable as a small heat radiator to prevent heat build-up and ensure the unreliability and long service life of semiconductor chips.
It is intended to provide an e-structure.

FIG. 1 shows the structure and usage of a conventional heat radiator as described above. In the figure, 1-1, 1-2, and 1-3 are heat sinks, 2-1, 2-2, and 2-3 are heating elements such as semiconductor circuit chips, and 4 is a board on which these are mounted. It is. A large number of substrates are further incorporated into the device housing in parallel with and adjacent to the substrates. Usually, several dozen or more semiconductor cow circuit chips and heat sinks bonded thereon are mounted vertically and horizontally on each board. The material used for the heat sink is a metal with good thermal conductivity, such as copper or aluminum. As such a heat radiator, a metal heat conductor as shown in FIG. 1 is used, and the reason why a heat pipe heat radiator, which should be extremely efficient, is not used practically is as follows.

B) Since many heat sinks are installed close to each other, there is a limit to the diameter. Furthermore, since the distance between the heatsink and the adjacent substrate cannot be increased, there is a limit to the height of the heatsink. Therefore, the capacity of the heat pipe cannot be increased.

(+:I) Due to the same reason as in the previous section, there is a limit to the height or butterfly diameter of each fin, that is, it is not possible to increase the area of each fin.

e→ Since many radiators are lined up in relation to the direction of the cooling air, in order to send enough cold air to the radiators on the leeward side, the restrictions set forth in the previous item B) are required J) j! It is necessary to reduce the volume of each heatsink by adding a ml limit, and it is also necessary to increase the spacing between individual fins to reduce the resistance to wind pressure.

When a heat pipe with a conventional structure is used as a radiator under the above-mentioned limitations, the internal volume of the heat pipe is extremely small), the heat transfer characteristics are poor, the heat dissipation performance of the fins is poor, and the production cost of the heat pipe is high. However, the ratio of cost to performance decreases, making it unsuitable for practical use. FIG. 2 shows the shape of a heat pipe having a conventional structure when used as a heat radiator as described above. In the figure, 3 is a semiconductor circuit chip, 4 is a substrate, 5 is a heat pipe container, 6 and 7ri end face sealing plates, 8Fi fins, and 9 is a quick. In order to allow sufficient airflow to pass through, the mounting pitch of the fins 8 is more than twice the normal pitch, and for the same reason, the heat pipe 5 has a small diameter. Heat pipe containers are evacuated to a high vacuum, so even small heat pipes have a thickness of about 0.5 mm to prevent buckling.

Similarly, in order to withstand high vacuum, the terminal sealing plate is also 1.5mm to 2mm thick.
It's about 0 millimeters. The thickness of the working fluid reflux wick 8 is required to be 1.5 mm to 2 mm. Therefore, the fin outer diameter is 13
If the width is limited to 5mm, the outer diameter of the heat pipe container will be 3mm, and the container thickness,
(If the wick thickness is subtracted, it is impossible to provide a steam passage) It is no longer possible to demonstrate its performance as a heat pipe. When the steam passage diameter is set to 4 mm in order to obtain the characteristics as a heat pipe, the heat pipe diameter is 8 mm and the surface height is 13 mm. If the fin size is 3 mm, the cooling effect of the L fin cannot be expected, and the expansion of the heat pipe as a radiator becomes meaningless, and the expensive heat pipe production costs are completely wasted. I understand.

The heat pipe radiator according to the present invention exhibits a sufficient heat dissipation effect even with small fins, and makes it possible to configure a radiator that has sufficient internal volume and exhibits sufficient heat pipe characteristics even with a small heat pipe. It is. The scissors heat pipe radiator will be explained in detail below depending on the garden. 5th Itri
FIGS. 3 and 4 are cross-sectional views showing the basic structure of the heat pipe radiator according to the present invention, and show examples of its application. FIG. 3 is a longitudinal cross-sectional view of the shaft. FIG. 4 is a cross-sectional view of the Moom' in FIG. 3.

FIG. 6 shows another applied example. The numbers in the figure are all common numbers, and the 9th container is formed into a bellows shape and also serves as a fin. Because it has a bellows shape, the pressure resistance of the container is extremely strong, and even a pure copper container with a wall thickness of 0.15 mm can withstand pressure of 2Dk/j, and the bellows will shrink when withstanding the negative pressure of a high vacuum. There is no risk that the container will buckle even if the wall thickness is 0.1 mm. The biggest feature of this bellows fin is that it has a heat exchange rate of 0.1 to 0.
The vapor of the working fluid radiates heat and liquefies inside the fin only through an extremely thin metal wall such as 5 mm thick. Therefore, heat can be radiated with almost no thermal resistance against the airflow flowing on the outer surface of the fins. Compared to conventional heat pipe fins, where a large thermal resistance loss occurs as a sum of the thermal resistance of the fin, the contact resistance between the fin and the container, the thermal resistance of the wick, etc., the bellows fin according to the present invention has a large thermal resistance loss due to its height. is 3
Even if the fin is as small as a millimeter, or if the pitch is more than twice that of a conventional fin, its heat dissipation ability is far superior. This is the greatest effect of the bellows fin according to the present invention. In addition, while conventional heat pipe fins have a slow thermal response speed due to the heat transfer time in the fin material and the time to penetrate thick containers and quicks due to heat conduction, the bellows fin according to the present invention has a slow thermal response speed. .08～
Air flow and working fluid vapor can exchange heat with almost no heat transfer time 1-* only through the thin container wall thickness of 0.18 mm, so the thermal response time is so short that it can be ignored. It exhibits extremely excellent thermal response characteristics. This point is also a major effect of the bellows fin according to the present invention. In addition, the bellows fins do not have to change in height, and since they have high pressure resistance, the total wall thickness of the bellows container can be made extremely thin, giving the maximum internal volume within a limited size range. Another major effect of the heat pipe radiator of the present invention having a bellows container is that it can exhibit the characteristics of a heat pipe in light. This internal volume can be easily understood by comparing Figures 2 and 93 with a conventional heat pipe. 1 in each figure
4 is a wick, which is a tape-like or string-like quick such as a metal thin wire bundle, a braided cord of a metal thin wire bundle, a rolled metal mesh bundle, or a metal mesh tape thick. The quick 14 crosses the bellows groove by the elastic wick support 16,
It is supported by being pressed along the lengthwise direction of the heat pipe. The number of quicks used is determined by the inner diameter of the bellows of the heat pipe radiator, but they are placed along the bellows groove to form a necessary gap so that sufficient working liquid vapor can be supplied into the bellows groove. If a large amount of working fluid liquefied in the inner groove of each bellows fin drips into the container from an unspecified position in the bellows inner groove, the supply of steam to the groove becomes irregular or impossible. The working fluid is trapped in the bellows fin grooves by the steam flow, reducing the heat exchange ability of the heat pipe, and in the worst case, there is a risk that the heat pipe may stop operating. The role of the wick is to prevent this kind of situation from occurring, to continuously absorb the working fluid in the bellows fin grooves, and to make the working fluid flow quickly to the heat-absorbing surface of the heat pipe radiator. This is one of the main features of the structure of the heat vibrator according to the present invention. In the figure, reference numerals 12 and 13 are end faces of the heat pipe radiator, and only each thread 13 is a heat absorbing surface, and 12 is a heat radiating surface.

Conventional heat pipes have low container strength, so
Is it necessary to withstand the negative pressure caused by the reduced pressure of heat pipe molding?
Also, the end face sealing plate needed to be as thick as the thickness of the end sealing plate since it had the role of reinforcing the strength of the container in order to withstand the external pressure when using the heat pipe. As a conventional example of End Face Sealing Board Co., Ltd., a wall thickness of 1 mm is used for a small heat pipe, and a wall thickness of 3 to 5 mm is used for a heat pipe with an outer diameter of about 40 mm. In the heat pipe radiator according to the present invention, since the container has a bellows shape, the container itself has an extremely high pressure resistance, so the end sealing plate does not require a reinforcing force of 0.08 to 0.0.
It can be made extremely thin, such as 18 mm.

Also, in the heat dissipation port according to the present invention, 111! on both end faces! ? k
1 is a heat absorbing plane, and the other surface is also a heat radiating plane, so in order to improve heat exchange characteristics, the thinner the better. Furthermore, as mentioned above, there are strict limitations on the thickness of the heat radiator, so the thinner the end face sealing plate is, the more desirable it is because the content that operates as a heat pipe within the radiator can be increased. From this point of view, it can be said that by employing a bellows-shaped container, the thickness on both sides can be made thinner, which is a desirable effect that meets the purpose of use of the heat pipe radiator of the present invention. Because of this advantage, the structure of the present invention allows the sealing plate to be integrated with the container and the bottom plate at the same time, which improves mineral performance and reduces costs. This is also an extremely useful effect. In other words, due to manufacturing technology, the bellows-shaped container and the end face B
It is possible to simultaneously form a lid in a seamless manner from a single raw material plate, and the end face 12 can be formed into a single piece without a joint by using a support hollow tube as will be described later. This is possible because the wall thickness in the direction is thin, and is an effect of adopting a bellows-shaped container. In the production of heat pipes of conventional structure, end face welding and sealing work is a laborious and costly work. High vacuum heat pipe containers require air-tight sealing of the ends, which is a major cause of manufacturing loss. One of the most notable problems is the deformation of the end sealing plate during welding and the infiltration of solder material into the container during soldering. When the heat pipe heat radiator of the present invention is extremely small, such as 415 to 10 mm, and the end surface is used as a heat absorption surface, even a slight distortion due to the low temperature during welding causes an increase in contact thermal resistance. This can be a fatal flaw. Furthermore, if the melted 90% metal flows into the inner surface of the surface stopper plate and the thickness of that part increases when the plate is attached, it may cause a decrease in the performance of thick P''.

Due to the adoption of a bellows-like antenna, the wall thickness of the end face becomes thinner and thinner, and the end face of the heat pipe, which can be integrally molded, does not have the above-mentioned problems at all. In the figure, a hollow tubular support is used to prevent the bellows from contracting below a predetermined length and shortening the radiator. As shown in Figures 3 to 6, only one end surface is a heat absorbing part and To
In the case where the other end surface is given a role as a part of the heat dissipation surface, the hollow tube of the support body 15 is formed integrally with the end surface 12, and these are integrated and are independent of the bellows part. It is constructed like a heat pipe. The outer periphery of the end surface 12 is formed like a single peak of a bellows, so when the radiator contracts, the support cylinder elastically contacts the inner surface of the end surface 13 to support both ends and prevent further contraction. do. Since the radiator of the present invention is a heat pipe, the inside of the container is depressurized to a high vacuum, so it has a strong contraction property during low temperature operation, and even if the bellows itself has strong elasticity and does not completely contract. It has the property of contracting under small external pressure. If the shrinkage rate is large, the internal volume of the radiator will decrease, leading to a decrease in the degree of vacuum within the container. When the degree of vacuum decreases, the evaporation temperature of the working fluid increases, the flow rate of the working fluid a decreases, and the performance as a heat pipe deteriorates. Furthermore, the contraction of the heat radiator reduces the gap between the bellows fins, reducing the amount of cooling air passing through and reducing the heat radiation efficiency. The first purpose of the hollow tube of the support body 15 is to prevent this and maintain the heat radiation b at a predetermined height. Another effect of the supporting hollow tube is that it functions as an independent heat pipe when integrated with the ore end surface, so the working fluid is returned for the heat dissipation effect of the heat pipe that operates between direction B and the bellows container. The point is that it does not disturb the Nykul.

In #IIfrJ12, the working liquid vapor chamber for heat dissipation moves within the support hollow tube, so there is no interference with the bellows fin and the steam flow tube. Also, heat dissipation I at the end surface n! Since the cased working fluid passes through the support hollow tube and flows back to the heat absorbing section 13, there is no possibility that the liquid will drip into the vapor flow toward the vapor flow tube and disturb the flow and reduce efficiency. Another advantage of the support hollow tube is that by forming the quick string 14 with a large diameter as shown in No. 6a11fl1, the hollow tube can also serve as a wick support. In this case, there is an advantage that the elastic quick support 16 can be omitted. In this case Wick @14
Is there a need to reduce the number of books?

Further, as another effect of the support hollow tube, as is clear from No. 31il, when assembling the heat pipe container as a radiator according to the present invention, the welding point 18 is the end face n, 13
And, it is located at a position that has no relation to the working fluid return path for the working fluid vapor flow 1 during heat pipe operation, and is located at a location that facilitates welding workability. As mentioned above, the position of this explosive contact has a great influence on the small-sized heat pipe of the heat sink of the present invention.

When the wick support 15' is formed as a tensile elastic quick support as illustrated in FIG. 5, it is possible to have the wick support 15' also serve to prevent the bellows from contracting beyond the necessary limit. In this case, it is possible to make the line support hollow tube 15 4i11. When the support body 15 is omitted, Fi,
There is a risk that the operating TLL that has liquefied on the inner surface of the container at the end surface may drip from an unspecified location.

To prevent this, the end of the quick string can be made long, and the working fluid can be absorbed by dispersing it on the inner surface of the end surface 12, or the inner wall surface of the end surface 12 can be formed into a curved surface. Since the heat pipe radiator according to the present invention has a quick expansion, it can sufficiently exhibit its performance even under usage conditions where the radiator is inclined or horizontal. Since the working fluid transfer distance for such small heat pipes is short, the wicking effect is extremely large, and when used horizontally, it not only exhibits normal heat pipe characteristics, but also in some cases, when used upside down, it can be used under top heat conditions. However, the cooling effect is still effective with only a slight decrease in performance. However, when used upside down, the front surface will dry out and the heat dissipation effect will be lost. That is, the independent round heat pipe formed by the end face and the supporting hollow tube 15 is a siphon type heat pipe with a quickless lid or a butterfly, and relies only on the flow of the working fluid and gravity, and uses top heat. This is because it does not work at all under these conditions. The performance curve of the pipe radiator according to the present invention can be further improved by forming wicks 17t on both end faces of the pipe radiator.When the radiator is used horizontally, the working fluid is uniformly and rapidly distributed on the heat absorbing surface. It is effective in promoting dispersion and evaporation ability. As described above, a number of functions and effects of the structure according to the present invention as a heat pipe radiator having one end surface as a heat absorption surface will be described in detail. The above-mentioned effects were described as individual releasers, but
FIG. 1 shows the outstanding effects of the heat vibrator according to the present invention as a system in which a large number of heat sinks are used in an application as partially exemplified. The heat pipe radiator having a bellows container according to the present invention has a structure in which its length and shape always change depending on the temperature situation at that time. As mentioned above, it shrinks at low temperatures and is supported by a support hollow tube to prevent shrinkage, but if the device generates heat while in use,
The working fluid inside the heatsink generates a vapor pressure that corresponds to the temperature to which the heatsink is applied, and the length of the heatsink changes in response to the temperature of the semiconductor circuit chip that it cools. . For high-temperature chips, it expands to reduce the internal pressure of the container and activate the operating cycle within the heat pipe. Also, the pitch of the bellows fins, which are elongated due to the hot tip, is enlarged to allow more cooling air to pass through and dissipate more heat. Also, heatsinks serving chips that do not require much cooling will shrink, slowing down the heat transfer cycle within the container, reducing the bellows spacing, reducing air intake, and reducing length, reducing the overall Since the volume is smaller, unnecessary air flows to the radiator on the leeward side. The radiator that is currently active on the board and is responsible for cooling the heating element that produces a large amount of heat will automatically be turned on so that more air can be taken in and more heat can be dissipated. #It has the function of adjusting. This is not a problem for a single radiator, but when using hundreds of radiators in the same housing of the same device, it becomes effective for efficient cooling inside the housing. It can be said that the effect is outstanding.

In this way, in a heat pipe heat radiator that automatically adjusts heat radiation efficiency by expanding and radiating depending on the temperature of the heat absorption part, the selection of the working fluid influences its characteristics. 'For example, when a semiconductor device, which is a heating element, is heated within the range of 40°C to 100°C, which is the most common operating range in the industry, methanol is used as the working fluid, or the most appropriate pressure inside the container is generated. The internal pressure of a heat pipe container of methanol is 0.4 J at ℃! ＃／j、
1 at 70℃/-3 noodles at 1100℃, and the bellows expands and contracts by changing appropriately in the range of 2.5 to 3 times the atmospheric pressure. It is possible to maintain a balance with atmospheric pressure at a temperature in the middle of the range.If pure water is used as the working fluid in the heat pipe radiator of the present invention, which is used in a range of extremes, The internal pressure generated is 0.09 T4/d at 70°C.
It is 0.3 Kr/aj at ℃ and I Kg/- at 100℃, and it is necessary to operate under negative pressure relative to atmospheric pressure in all ranges, and contraction within the range where the bellows can expand and contract. Using only the side makes it difficult to design multiple bellows. In other words, in the case of the same metal material, the number of bellows threads is 2.
In addition to doubling the cost, it is also necessary to increase the thickness of the bellows in order to sufficiently withstand strong negative pressure. This means an increase in the wind pressure resistance of the bellows fins of the radiator, which is undesirable. On the other hand, a methanol working fluid heat pipe balanced with atmospheric pressure at 70° C. has a ratio of expansion and contraction of approximately -, so the full range of the 1M expansion characteristic of the bellows can be utilized. Also, the fact that the middle point of the heating element temperature and the middle point of the expansion/contraction range of the bellows coincides means that the most natural point of the bellows matches the most frequently used one. This makes the To9 heat pipe radiator extremely short in terms of life span. Even if ethanol is used as the working fluid according to the present invention, performance equivalent to that of the hydraulic fluid can be exhibited.

The structure and function and effect of the heat pipe radiator according to the present invention have been described in detail above.The basic structure of the heat pipe according to the present invention is that a bellows tube is used as a heat radiating part of a heat pipe container, and the peaks of the bellows are used as fins. In addition, it prevents the working fluid that is liquefied and accumulated inside the armpit bellows fins from staying, increases the heat dissipation ability of the bellows fins, and uses a string-like or tape-like wick as a return path for the working fluid. It has a vertical structure that intersects with the groove of the groove. This vertical string-like wick is a return path for the working fluid, but the gap provided between the wicks with a sufficient width serves as a steam passage that sends sufficient working fluid vapor to the bellows fin. This combination of string-like wick and bellows fins is a new structure not found in conventional heat pipes, and is the basic structure of the heat pipe radiator according to the present invention.

The shape of the bellows in carrying out the present invention is defined as a bellows shape. As another shape of the bellows, a helical bellows having a helical protrusion and * has been proposed for use in heat pipes for other uses.

However, in the case of the application of the present invention, if the edge carbelose is used as a fin, it will prevent the passage of airflow and increase the wind pressure resistance. - The cooling air volume is reduced compared to -, and the overall function is significantly reduced. Although this curved edge fin structure itself has the advantage that the working fluid can flow smoothly as a working fluid flow path, it cannot be used at all in the heat sink radiator according to the present invention for the above-mentioned reasons.

In the heat pipe heat radiator according to the present invention, if the metal for the bellows is appropriately selected, and if the wall thickness, number of ridges, and shape of the ridges are selected, the heat will depend on the elasticity of the bellows itself. It can sufficiently withstand reduced pressure inside the pipe container. However, when manufacturing the radiator tR according to the present invention as a particularly high-performance heat pipe, high-temperature heat treatment is required in the heat pipe manufacturing process, which may significantly reduce the elasticity of the bellows, and may also be difficult to use. Depending on the material, it may be completely annealed and lose its elasticity. The hollow tube support for preventing excessive shrinkage, which has been described in detail above, is used as an applied example that takes countermeasures against this difficult case into account, and is used to maintain the characteristics and improve the performance of the heat radiator according to the present invention. Since the hollow tube support also serves as a working fluid flow path and a steam passage on the heat dissipation side end surface, in the case of a basic structure that does not use the hollow tube support, the inner surface of the heat dissipation end surface should be made spherical as shown in each figure. Take measures such as installing a good wick to help the flow of the hydraulic fluid to the string-like quick, and to prevent the hydraulic fluid from dripping from unspecified positions.

Furthermore, when using the heat dissipation efficiency automatic adjustment function that utilizes the wide stretchability of the radiator described above, the hollow tube support for preventing overshrinkage can be expanded or omitted. In this case, it depends on the selection of the metal material for the expansion seeds to prevent overconcentration, and the elasticity and pressure resistance are enhanced. Since the heat pipe radiator according to the present invention is an extremely small and made heat pipe, as mentioned above, it makes full use of the capillary action so that it can be tilted, horizontally, or wherever necessary.
As mentioned above, the heat pipe radiator according to the present invention can be used upside down if the heat pipe is used upside down. Therefore, both end surfaces of the heat pipe radiator according to the present invention can be used as heat absorbing surfaces. In the case of double-sided use, both substrates are either vertical or horizontal; in the former case, the heat sink is used horizontally; in the latter case, one end side is bottom heat and the other side is top heat; The pipe works reliably in either case.

As mentioned above, the heat pipe heat radiator according to the present invention having bellows fins and string-like quicks solves all of the drawbacks of the conventional type and the one-piece heat radiator, and exhibits many more excellent functions and effects than the conventional type. Utilizes the advantages of alternative heat pipes to provide nine efficient heat sinks.

[Brief explanation of drawings]

Figure 1 is a front view showing an example of a conventional heatsink and its mounting on a board.
FIG. 2 is a cross-sectional view of a design example when a conventional heat pipe is used in the usage example shown in FIG. 3, 4, and 6 show other application examples; FIGS. 3 and 6 are longitudinal sectional views; FIG. 4 is a sectional view of the Moom in FIG. 3. DESCRIPTION OF SYMBOLS 1--Radiator, 3--Semiconductor circuit chip, 4--Substrate, 11--Bellows fin, shank--Radiating end surface, 13
... Endothermic end surface, 14-- Wick ζ15-- Support for preventing excessive shrinkage, 16- Quick support.

Claims (3)

[Claims] (1) A radiator in which one end surface of a cylindrical heat pipe is used as a heat absorption surface and the other outer surface is used as a heat radiation surface, and a deep grooved bellows tube with many grooves is used as a container for the heat pipe. The peaks of the bellows act as heat radiating fins, and the back surface of each heat radiating fin, that is, the inner surface of the groove when visible from inside the container, serves as a condensation surface for the working fluid vapor, and intersects with the group of grooves. And a predetermined number of string-like wicks are inscribed and installed vertically along the inner surface of the container? : Heat pipe radiator with % mold. (2) A patent claim characterized in that a hollow tube of a predetermined length is provided on the inner surface of the heat dissipation side end face to serve as a support for preventing the bellows container from shrinking below a predetermined length. A top pipe radiator according to item 1. (3) Claim 1i, characterized in that the working fluid for the heat pipe is methanol or mineral ethanol.
jl! The heat pipe radiator according to item 1.