JPS58119659A - Formation of heat pipe type heat connecting element structure and cooling structure - Google Patents

Abstract

PURPOSE:To substantially improve the heat-absorbing and heat-radiating capabilities as well as to simplify the installation and adhesion of the heat sink of a heat-connecting element by a method wherein the heat-connected element container is formed heavily in thickness to the extent that the pipe used thereon will be widened easily by the boosting of the working fluid pressure, and a small-pitched bellows part is provided at the part in the vicinity of the heat absorbing surface of the container. CONSTITUTION:One end face 3 of the heat pipe type heat-connecting element is located adjoining to the heat generating element 10, which is provided on a circuit substrate 15, on the heat absorbing surface, and the external circumferential surface 1 of the container adjoining to the other end face of the element is inserted in and fixed tightly to the inserting hole 11', provided at a heat sink 11, on the heat radiating surface. The container is formed at a very thin at the part 1, and this makes the pipe to easily widened earlier than the other part to the element container when the vapor pressure of the working fluid inside the element is boosted by heating. Also, the short-length part of the container adjoining to a heat-absorbing end face 3 is formed in a bellows 2. According to this construction, the heat rediating area and the heat absorbing efficiency are sharply increased, and the heat exchange capacity is unchanged even when some non-condensing gas is generated and stagmated on the end face 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for thermally connecting a heat generating element installed on a circuit board and a heat sink to cool the heat generating element and preventing a rise in temperature inside the circuit board and equipment housing. The present invention relates to the structure of a heat pipe type thermal connection element, and to a method of forming a cooling complement consisting of a plurality of heat pipe type thermal connection elements and a heat sink.

'4 = The novel structure of the heat pipe type thermal connection element according to the invention greatly improves the heat transfer ability of the conventional structure thermal connection element, that is, it only greatly improves its heat absorption ability and heat dissipation ability. The present invention provides a method for forming a novel cooling structure that facilitates attachment of a thermal connection element to a heat sink and facilitates adhesion to a heat generating element.

The conventional method for cooling a heat generating element is to cool only the heat generating element.
How to separate it from the t11 circuit board and install it directly on the heat sink, or attach the circuit board to the heat sink 1! :! A method has been adopted in which heat generating elements are indirectly cooled through a circuit board. The former has the disadvantage that the volume of the equipment case becomes excessively large.
Although it is possible to lower the temperature inside the device case, the circuit board temperature is not sufficiently cooled, and the heat generating elements are not sufficiently cooled. In modern electronic equipment such as those equipped with a large number of heat generating elements on a high-density circuit board, a cooling method to improve the above-mentioned drawbacks is to use a metal plate with a water cooling jacket or a metal combined with a heat pipe cooling device. A cooling method is being adopted in which a heat sink such as a plate and a heat generating element on a circuit board are directly connected by a heat pipe type thermal connection element.

FIG. 1 shows one example, and FIG. 2 shows an example of the company et al.

In FIG. 1, an ordinary heat pipe 1'' is used as a thermal connection element, one end surface 3 of which is soldered to a heating element 10, and the other end surface 4 is soldered to a heat sink 11. Thermal energy is generated in the heating element and quickly transferred to the heat sink, and the heating element is transferred to the substrate 1.
5. It is cooled without increasing the temperature inside the equipment.

However, in this case, the bonding work is extremely difficult when bonding a large number of elements, and it is necessary to apply a large cold compression force between the heat sink and the substrate in order to absorb dimensional errors and thermal distortions caused by the manufacturing of the substrate. In addition, there were drawbacks such as the fact that it was difficult to guarantee the lifespan and reliability of the solder joints. FIG. 2 shows a thermal connection element proposed for rounding to avoid these drawbacks, and the container 2 has curved edges.

The elasticity of the bellows not only facilitates the soldering work but also improves bonding reliability by absorbing stress generated due to differences in distance between the heat sink and the substrate due to manufacturing errors in the plane of the substrate and thermal distortion. Furthermore, the helical vessel 4 serves as a return path for the working fluid and does not require a wick as shown in FIG. 1, resulting in many improvements such as a simpler structure and lower manufacturing costs.

However, the thermal connection elements shown in FIGS. 1 and 2, in which the end face of the heat pipe is used as the heat exchange surface, have the following drawbacks, and there remains a need for improvement.

a) The heat exchange area was small, so it was difficult to absorb and dissipate sufficient heat, which is a characteristic of heat pipes.

(b) Although the improvement depends on the elasticity of the bellows, it is difficult to bond a large number of elements to both end faces. 4!
Bellows heat pipes are dependent on the rise in temperature during soldering, which causes the vapor pressure of the working fluid to rise, causing the bellows to stretch, and even if pressure is applied to limit the stretch at both ends, there is a risk of it bending laterally and buckling. Therefore, it is necessary to solder to the heat sink before the heat pipe is completed, that is, before filling the hydraulic fluid, and then fill in the hydraulic fluid. It is by no means an easy task.

(c) In the production of heat pipes, a small amount of non-condensable gas may get mixed into the container due to a slight error in the procedure, or non-condensable gas may be generated from the container metal. These gases accumulate on the upper end surface of the heat pipe, and in the case of a thermal connection heat pipe element whose upper end surface is the heat exchange surface as shown in Figures 1 and 2, a very small amount of non-condensable gas is accumulated. Even if it occurs, it spreads over the entire inner surface of the heat exchange surface and forms a thermal insulation layer, resulting in a fatal drop in performance. Therefore, the yield rate for manufacturing thermal connection elements is greatly reduced, and it becomes necessary to use extremely sophisticated manufacturing control techniques during manufacturing.

(2) Since the heat pipe type thermal connection element is extremely small, the amount of working fluid required is extremely small, making it difficult to fill in a fixed amount of working fluid.Also, even a slight error in the amount of hydraulic fluid filled in can cause damage to the thermal connection element. Performance will be significantly affected.

The heat pipe type thermal connection element according to the present invention improves all of the drawbacks of the conventional heat pipe type thermal connection element mentioned above, and FIGS. 3 and 4 are structural diagrams showing an embodiment thereof. Each side is shown in four longitudinal cross-sectional views. Its basic structure and its effects are as follows.

0) One end surface 3 of the heat pipe type thermal connection element is a heat absorption surface and is adjacent to the heating element 10 installed on the circuit board 15.

(b) The outer peripheral surface 1 of the container near the other end is a heat radiation surface and is tightly inserted and fixed into an insertion hole 11' provided in a heat sink 11.

(c) The container is formed to have an extremely thin wall in part 1, so that it can be easily expanded before other parts of the element container due to the rise in vapor pressure of the working fluid inside the element due to high temperature heating. It is formed.

(B) The close insertion and fixation of part 1 of the ring is easily inserted and easily fixed by this tube expansion method.

In addition, when using this tube expansion method, it is possible to insert a large number of thermal connection elements at the same time, expand the tube at the same time, and insert them at the same time, and the degree of insertion can be adjusted by making the overall tube expansion temperature uniform. Uniform insertion strength can be achieved. In addition, when this insertion and fixing method is adopted, even if the diameter of the insertion hole provided in the heat sink is slightly uneven, or the inner wall of the hole is slightly uneven, the element container wall will expand to follow suit, resulting in a perfect seal. There is also the advantage that it is possible to obtain Since the thermal connection element according to the present invention has a small number of bellows threads, there is no possibility of lateral buckling occurring due to elongation due to tube expansion temperature.

(b) The short portion of the container near the heat-absorbing end face 3 is formed into an accordion-like bellows 2. The role of the bellows is as follows. (6) Providing appropriate stretchability and elasticity to the thermal connection element to facilitate assembly work.

0 Maintain contact with the heat generating element with appropriate pressing force to ensure adhesion reliability with the heat generating element. Even if there is an error in the distance between the heat sink 11 and the circuit board 15, assembly becomes easy. ■ Absorbs misalignment between thermal connection elements and heating elements that occur due to thermal expansion and contraction between the heat sink and circuit board, alleviates strain stress, and maintains bonding reliability between thermal connection elements and heating elements for many years. Guaranteed for months. (g) Acts as a heat radiation fin inside the container and promotes evaporation of the working fluid.

[F] Since the working fluid is uniformly dispersed in the circumferential direction in the working fluid evaporating section and uneven distribution of the working fluid in the working fluid evaporating section is prevented, heat exchange efficiency is improved.

(E) Because of the structure as described above, the heat dissipation area is greatly increased and the heat absorption efficiency is also greatly increased compared to the heat pipe type thermal connection element as shown in FIGS. 1 and 2.

(f) Even if some non-condensable gas is generated and accumulates on the end face 4, it does not affect the heat exchange ability. This is because heat exchange is performed in the outer cylinder of the container 1.

The basic features and effects of the thermal connection element according to the present invention illustrated in Figures 3 and 4 are as described above.

In the figure, reference numeral 5 indicates a hydraulic fluid injection capillary which is sealed after the hydraulic fluid has been sealed, and reference numeral 7 indicates a welded joint between the thin-walled container 1 and the thick-walled container 1' of the thermal connection element container.

8 shows the amount of working fluid when the thermal connection element is not in operation. A liner 9 is filled between the heating element 10 and the bellows 2 to increase the heat transfer area. 12.1
Reference numeral 2' indicates a heat transfer means such as a water pipe or a heat pipe for further transferring and dissipating the thermal energy absorbed in the heat sink 11 to the outside of the housing.

6 in the applied embodiment of FIG. 3 is a hydraulic fluid metering capillary.

The capillary tube passes through the container 1' and is hermetically welded to the container, and its end in the container holds the thermal connection element in a predetermined position (vertical position in this figure) and extends the bellows to a predetermined length. The opening is opened on a plane that coincides with y in the horizontal plane that is formed when the working fluid condenses on the bottom of the container at a predetermined temperature (in this figure, at room temperature). Further, the end of the thin tube outside the container is hermetically sealed by welding after the hydraulic fluid has been quantified into the element container.

Such a working fluid metering capillary is provided to accurately and quickly inject a required amount of working fluid when forming a heat pipe, and its usage is as follows.

(a) Distillation method While cooling the container, superheated steam from the working fluid is introduced through the working fluid injection capillary and discharged through the metering capillary. The hydraulic fluid measuring capillary and the hydraulic fluid injection capillary are sealed in a state in which air and other non-condensable gases in the container are completely exhausted and steamed hydraulic fluid is spouted from the metering capillary.

←) Hydraulic fluid discharge method using steam. Once the inside of the container is filled with purified working fluid, superheated steam of the working fluid is introduced from the injection capillary, and the working fluid is discharged from the metering capillary. When superheated steam starts coming out from the metering capillary, both capillaries are closed. Seal.

(→Drainage method of hydraulic fluid by heating the container. Once the inside of the container is filled with purified hydraulic fluid, the hydraulic fluid injection tube is sealed. After that, the container is heated to increase the vapor pressure inside the container. The hydraulic fluid is then discharged from the hydraulic fluid metering capillary, and when the hydraulic fluid is no longer discharged and steam begins to blow out, the metering capillary is sealed.

2) A hydraulic fluid discharge method that relies on the pressure difference inside and outside the container. A method in which container heating and suction using a metering capillary as described in item (c) are used in combination.

By using the various metering tubes as described above, it is possible to quantify the amount of hydraulic fluid injected into the thermal connection element.

However, in the case of a heat pipe container with a conventional structure, it is necessary to change the amount of working fluid depending on the type of working fluid, the usage conditions of the thermal connection element, etc.). It was necessary to manufacture different containers. However, since the container for the thermal connection element according to the present invention has a bellows at its bottom, the opening position of the hydraulic fluid metering capillary can be freely adjusted by expanding and contracting the bellows, so that operations can be performed using the same container. It becomes possible to freely adjust the amount of liquid. This is one of the effects of the thermal connection element structure according to the present invention.

In the applied embodiment shown in FIG. 4, in addition to the basic structure described above, an outer cylinder 13 having an inner diameter larger than the outer diameter of the bellows is provided in a portion near the heat absorption surface of the container. At its bottom 13', the outer cylinder adjoins the end face of the heat-generating element 10 together with the end face 3 of the thermal connection element and together with the end face of the heat connection element forms a heat-absorbing surface.

Further, the upper end of the outer cylinder 13 is a free end, and is slidable independently of expansion and contraction of the thermal connection element container.

The gap between the outer cylinder 13 and the thermal connection element container 2 is filled with a heat transfer material 14 that is non-evaporative, has good thermal conductivity, and is flowable.
It is filled with. Due to the fact that the upper end of the outer cylinder 13 is a free end and the filling heat transfer material has fluidity, the elasticity and elasticity of the bellows container 2 are not hindered in any way. The heat transfer material 14 is also completely filled between the valleys of the bellows. These additional structures such as 13 and 14 not only allow heat conduction from the heat absorbing surface 3, but also rely on thermal energy absorbed at the bottom 13' of the outer cylinder to transfer the bellows container part 2 through the heat transfer material. Further, since the bellows 2 serves as a radiation fin within the container, heating and evaporation of the working fluid is further promoted. That is, the above-mentioned outer cylinder structure exhibits the effect of greatly improving the heat exchange ability in the heat absorption surface and the working fluid evaporation section that returns from the bellows section.

As mentioned above, the heat pipe type thermal connection element according to the present invention overcomes the drawbacks of the heat pipe type thermal connection element of the conventional structure, greatly improves its heat conduction ability, and also improves the heat transfer ability of the heat pipe type thermal connection element. In addition to providing a highly efficient and reliable cooling structure by combining a large number of heat sinks and a heat sink, the present invention also provides a novel forming method that makes it possible to assemble the cooling structure extremely easily and with stable quality. It is.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing a conventional example, FIG. 3 is a cross-sectional view showing one embodiment of the present invention, and FIG. 4 is a longitudinal cross-sectional view showing another embodiment of the present invention. 106. Thin wall container, l'@@11 thick wall container, 20, bellows, 3, fist, end face, 5... hydraulic fluid injection capillary, 6... hydraulic fluid measuring capillary, 7... welded joint,
8@...Amount of working fluid, 9...Liner, 10...Heating element, ]l・■Heat sink, 13...Outer cylinder, 14・
...heat transfer material.

Claims (4)

[Claims] (1) A heat source installed on a circuit board that thermally connects a heat generating element and a heat sink to absorb the thermal energy generated in the heat generating element and prevent an increase in temperature within the circuit board and device housing. A pipe type thermal connection element, wherein the end surface of one end of the thermal connection element forms a heat absorption surface adjacent to the ends of the heating element, and a portion of the thermal connection element near the heat absorption surface of the container is provided with a small pitch bellows part, and the outer peripheral surface of the part near the other end of the thermal connection element container is tightly inserted and fixed into the insertion hole provided in the heat sink to form a heat dissipation surface. Moreover, the wall thickness of the thermal connection element container is formed to be extremely thin in most of the heat dissipation surface portion, and the thickness is such that it can be easily expanded by means of increasing the vapor pressure of the working fluid by heating. The structure of a heat pipe type thermal connection element is characterized by being as thick as possible. (2) A hydraulic fluid metering capillary is provided at a predetermined location in the thermal connection element container, and the capillary is a hollow capillary provided through the container, and the terminal inside the container holds the thermal connection element in a predetermined posture. And when the bellows is kept stretched at a predetermined length, the horizontal surface formed by the hydraulic fluid inside the container at a predetermined temperature has an opening near the plane that coincides with y, and the terminal outside the container is exposed to heat. 2. The structure of the heat pipe type thermal connection element according to claim 1, wherein the connection element is airtightly welded and sealed with a fixing working fluid sealed inside the connection element. (3) An outer cylinder with an inner diameter larger than the outer diameter of the bellows is provided in the part near the heat absorption surface of the thermal connection element container, and the outer cylinder has an outer diameter of m
is adjacent to the end surface of the heating element together with the end surface of the thermal connection element at its bottom, forming a heat absorption surface together with the end surface of the thermal connection element, and the top of the outer cylinder is free i4. It can slide freely when the thermal connection element container expands and contracts! ! The space between the outer cylinder and the thermal connection element container is filled with a non-evaporative, highly thermally conductive, and flowable heat transfer material. A structure of a heat pipe type thermal connection element according to claim 1. (4) The thermal connection element according to claim (1) is inserted into each insertion hole of the heat sink, which is provided with insertion holes at positions corresponding to the respective elements of the heating element group installed at the circuit board temperature. After inserting the heat sink, the heat sink and the entire group of inserted thermal connection elements are heated all at once to uniformly raise the temperature to a predetermined temperature, and each thermal connection element is heated by increasing the vapor pressure of the working fluid. A method for forming a cooling structure, which comprises expanding the insertion portion of the container 3 and press-fitting it to the inner wall of a group of wall holes to be inserted.