JPH0122742B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a liquid cooling module, specifically a liquid cooling module for a heat generating element such as a high speed, high heat generation semiconductor element, that is, a fin cooling plate for heat dissipation. The present invention relates to a liquid cooling module in which a cooling plate is provided below the surface of the refrigerant liquid and is provided with a countermeasure against reduction in cooling capacity due to air entrainment, and further relates to a liquid cooling module in which a cooling plate is provided with vertical bubble passages.

(2) Background of the technology In order to cool packages in which semiconductor elements are densely mounted, liquid cooling modules are used in which the semiconductor elements are immersed in a boiling refrigerant in a sealed container. FIG. 1 is a schematic cross-sectional view of such a liquid cooling module, in which 1a and 1b are semiconductor elements (hereinafter referred to as elements), 2 is a substrate on which the elements are mounted, 3 is a sealed container, 4 is a boiling refrigerant,
Reference numerals 5 and 6 indicate plate-shaped fins for heat radiation disposed inside and outside the sealed container 3, respectively.

When either of the elements 1a, 1b becomes hot, the surrounding boiling refrigerant evaporates and bubbles 7 are generated.The bubbles 7 escape into the space above the refrigerant and become refrigerant vapor 8, while the sealed container 3 is cooled. Therefore, the condensed refrigerant becomes condensate 9 and returns to refrigerant 4. Although the element is efficiently cooled by repeating such a cycle, the heat contained in the bubbles 7 is transferred to the sealed container 3, so it is necessary to close the sealed container 3 in order to promote the liquefaction of the vaporized refrigerant. Needs to be cooled. There are two methods for cooling a sealed container: a water cooling method using cooling water and an air cooling method using air.

(3) Prior art and problems In general, the cooling capacity of sealed liquid cooling modules decreases significantly when air gets mixed in. On the other hand, in order to maintain the cooling capacity of the module, it has been proposed to provide a cooling plate with a small chamber for collecting air, as shown in FIG. In FIG. 2, 11 is a semiconductor element, 12 is a refrigerant liquid, and 1 is a semiconductor element.
3 is a bubble, 14 is a cooling plate, 15 is a module, and 16 is air.

In this example, when the refrigerant bubbles 15 condense, the effect that non-condensable gas such as air 16 is concentrated near the cooling plate 14 is utilized, but in reality, the air 16 is not cooled. plate 1
4, it was not possible to collect all of the air in a separate small chamber to retain the air, which had the disadvantage that it was not possible to completely prevent a decrease in cooling capacity due to air entrainment.

Further, the cooling plate is generally placed above the coolant liquid level to cool air bubbles generated from the semiconductor element surface and rising above the coolant liquid level. Problems have also been experienced in which when non-condensable gases such as air get mixed into the cooling module, they collect near the cooling plate and the cooling capacity is significantly reduced.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, the present invention provides a liquid cooling module in which a refrigerant liquid is sealed and is provided with a cooling plate. The purpose is to provide a module structure that does not reduce its performance.

(5) Structure of the Invention According to the present invention, in a liquid cooling module in which a plurality of semiconductor elements mounted on a substrate are immersed in a refrigerant liquid, fins are provided to condense bubbles of the refrigerant. This is achieved by providing a liquid cooling module characterized in that a cooling plate through which a second refrigerant flows is located below the level of the refrigerant liquid.

(6) Examples of the invention Embodiments of the present invention will be explained in detail below with reference to the drawings.

In the liquid cooling mechanism, the generated heat is removed as vaporization heat by boiling of the refrigerant liquid, and the vapor is transferred to the cooling plate by condensation.
Therefore, the inventors of the present application discovered that even if the cooling plate is placed below the liquid surface, efficient heat transfer is possible by contacting air bubbles, and on the other hand, in the boiling state of the refrigerant liquid, air does not dissolve in the liquid. They focused on the fact that if the cooling plate is below the liquid level, it will not be affected by air entrainment.

A first embodiment of the present invention is shown in FIG. 3, in which the parts numbered 21...26 are the same as the parts numbered 11...16 in FIG. In this embodiment, when the semiconductor element (hereinafter referred to as element) 21 operates and generates heat,
The refrigerant liquid 22 boils and takes away the heat of vaporization, generating bubbles 23 made of refrigerant liquid vapor. The bubbles 23 rise while stirring the liquid, contact the cooling plate 24 below the liquid surface, are cooled and condensed, and return to liquid.
In the figure, 24a indicates the fins of the cooling plate 24. Air layer 2 mixed into module 25
6 does not dissolve in the refrigerant liquid 22, so a decrease in cooling capacity is prevented. cooling plate 24
Cooling air or a coolant such as water is passed through.

In a second embodiment of the invention, the cooling plate is placed between the outermost fins 24 as shown in FIG. 4a.
The inner bottom part of a is curved so that the air bubbles 23 remain therein, so that the contact time with the air bubbles can be extended. Note that in FIG. 4 and subsequent figures, parts that have already been illustrated are designated by the same reference numerals.

FIG. 4b shows a third embodiment of the present invention, in which the fins 24a are inclined so that when the bubbles rise, they always come into contact with the fins 24a.

Furthermore, the inventors of the present application have found that the refrigerant liquid does not dissolve air near its boiling point, and therefore, if a cooling plate is provided below the liquid surface, the cooling plate will directly contact bubbles and condense them without coming into contact with air. At this time, by creating a large number of air bubble passages in the cooling plate that taper upward, it is possible to increase the contact area of the air bubbles and prevent air bubbles from remaining on the cooling plate and causing thermal insulation. We focused on the ability to prevent dissolved air from gathering on the cooling plate.

Referring to FIG. 5 showing the fourth embodiment of the present invention, when the element 21 is operated to generate heat, the heat is transferred to the refrigerant liquid 22 as vaporization heat, and bubbles 23 are generated. The bubbles contact the cooling plate 24 and are cooled back to the refrigerant liquid 22. At this time, if the amount of bubbles 23 is large, the bubbles further pass through the passage 27 provided in the cooling plate 24 and are cooled. For example, the passage 27 is 2 mm.
Form it so that it tapers upwards to 0.5mm. Since the cooling plate 24 is located in the refrigerant liquid 22, air does not collect therein, and some air is expelled to the air layer 26 via the passage 27 which narrows upward. A coolant 27a such as cooling air or water is flowed through the cooling plate 24. Further, the number of passages is determined based on the condensation area and the fluid resistance of the refrigerant 27a. Note that FIG. 6 is a perspective view of the cooling plate 24 showing a cross section with a portion cut away.

(7) Effects of the Invention As described in detail above, according to the present invention, in a liquid cooling module for high-speed, high-temperature semiconductor elements, a cooling plate with fins is provided below the surface of the refrigerant liquid, and the fins are attached to the fins. By making the cooling plate curved or slanted, and by forming passages in the cooling plate, it not only increases the cooling capacity, but also prevents the cooling capacity from decreasing due to air entrainment, which is effective in improving the reliability of semiconductor devices. It's large.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a conventional liquid cooling module, FIGS. 3 and 5 are cross-sectional views of an embodiment of the present invention, and FIGS. 4 a and b are a modification of the cooling plate of FIG. 3. The cross-sectional view, FIG. 6, is a partially cutaway perspective view of the cooling plate of FIG. 21...Semiconductor element, 22...Refrigerant liquid, 23
... air bubble, 24 ... cooling plate, 24a ... fin, 25 ... liquid cooling module, 26 ... air layer, 27 ... passage, 27a ... refrigerant.

Claims (1)

[Claims] 1. In a liquid cooling module in which a plurality of semiconductor elements mounted on a substrate are immersed in a refrigerant liquid, fins are provided to condense bubbles of the refrigerant, and a second refrigerant is flowed inside. A liquid cooling module characterized in that a cooling plate is arranged below the liquid level of a refrigerant liquid. 2. Claim 1, wherein the cooling plate is provided with a passage that tapers upward.
Liquid cooling module as described in section.