JP2005277411A - Loop thermosyphon with wicking structure and semiconductor die as evaporator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the heat energy generated by a semiconductor package fully dissipated. <P>SOLUTION: A loop thermosyphon system comprises a semiconductor die (10) having multiple microchannels (18), a condenser (14) which is in fluid communication with the microchannels, and a wicking structure (wick material structure, 26) which wicks a fluid between the condenser (14) and the semiconductor die (10). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor package cooling technique.

  As demands on computing performance increase, the complexity and cost associated with heat dissipation in computing systems continues to increase. These systems typically use a number of semiconductor packages that need to be combined with sufficient heat dissipation capabilities. In systems incorporating high density physical configurations, air cooling of the package may not be sufficient, in which case liquid cooling of the package is required.

  Some prior arts address heat dissipation requirements by directing fluid (eg, water or alcohol) directly to the semiconductor package. However, these techniques only dissipate some of the required heat dissipation. This is because how heat dissipation occurs depends on the fact that most of the thermal impedance is inside the semiconductor package rather than the fluid supplied and the heat sink attached to the package. Therefore, to greatly improve the overall heat dissipation, it is necessary to reduce the thermal impedance inside the package.

  The prior art has also attempted to improve cooling efficiency by incorporating microchannels in the semiconductor element (or “die”) of the package. Each microchannel is formed by etching in a semiconductor substrate, for example, so that more cooling areas are provided in the substrate. In one example, these microchannels are formed as a series of “fins” that help dissipate internally generated heat in the substrate. One of the problems associated with using such prior art microchannels is that high pressure is used to pump the fluid into the semiconductor die, that is, the fluid is forced through the microchannel by a pressure pump. It is. However, this pressurization pump has a high frequency of failure and is problematic for use in a computing system.

  The prior art has also attempted to cool semiconductor packages using “loop thermosyphon” technology. Prior art loop thermosyphons utilize an evaporator, such as a metal block, to cool the semiconductor package by carrying a cooling liquid between the evaporator and the semiconductor package. As the temperature rises, the package generates vapor from the liquid, and helps to transfer heat between the evaporator and the semiconductor package due to the density difference between the liquid and the vapor. However, prior art loop thermosyphons also do not reduce the internal thermal impedance of the semiconductor package, and thus also do not dissipate the thermal energy generated from the package sufficiently.

  In one embodiment, the loop thermosyphon system has a semiconductor die having a plurality of microchannels. A condenser is fluidly connected to the microchannel. Due to the wicking structure (light core structure), fluid is carried between the condenser and the semiconductor die by capillary action.

  In other embodiments, the loop thermosyphon system has a semiconductor die having a plurality of microchannels. One or more of the microchannels are shaped so that fluid preferentially flows along one direction of the semiconductor die. A condenser is fluidly connected to the microchannel, and the heated fluid from the semiconductor die is cooled and flows into the microchannel.

  In other embodiments, the loop thermosyphon system has a semiconductor die having a plurality of microchannels. At least one orifice is provided at the inlet of one of the microchannels so that fluid preferentially flows along one direction of the one microchannel. A condenser is fluidly connected to the microchannel, and the heated fluid from the semiconductor die is cooled and flows into the microchannel.

  FIG. 1 shows a schematic diagram of a loop thermosyphon system 10. The system 10 includes a semiconductor die 12 connected to the condenser 14 by an input side fluid flow path 16A and an output side fluid flow path 16B. The semiconductor die 12 has a plurality of microchannels 18 formed in the substrate as shown in FIG. 3, FIG. 4, FIG. 5, FIG. The condenser 14 is, for example, a heat exchanger that cools the fluid 20 in the system 10 by convection of air 22 adjacent to the condenser 14. The condenser 14 has a series of fins 14 </ b> A that enhance heat transfer to the air 22 as shown.

  The microchannel 18, the condenser 14, and the fluid channels 16A, 16B form a closed loop pressure volume of the fluid 20, thereby turning into vapor (or a mixture of vapor and fluid) when heated by the semiconductor die 12. And becomes liquid when cooled by the condenser 14. For convenience of explanation, fluid 20 is shown only in condenser 14, but it is clear that fluid 20 extends throughout the closed-loop pressure volume, either as fluid, steam, or a mixture of fluid and steam. is there. The heated fluid, vapor, or mixture of fluid and vapor from the semiconductor die is sometimes referred to herein as “heated fluid”.

  The system 10 includes an input side manifold 24A that connects the input side fluid flow path 16A to the semiconductor die 12, and an output side manifold 24B that connects the output side fluid flow path 16B to the semiconductor die 12.

  Inside the input side fluid flow path 16A, a wicking structure 26 (light) that provides capillary attraction that draws the fluid flow along the direction 28A from the condenser 14 through the input side fluid flow path 16A to the input side manifold 24A. A core material structure, shown in more detail in FIG. 2, is provided. The interaction of the fluid 20 and the semiconductor die 12 generates a heated fluid (or vapor or a mixture of vapor and fluid) that is also directed from the semiconductor die 12 through the output fluid flow path 16B. Move fluid flow along 28B. In one example of operation, the semiconductor die 12 boils the fluid 20 to produce a fluid and vapor mixture, thereby pressurizing the fluid stream along direction 28B. The mixture of the fluid and the vapor enters the condenser 14 from the output side fluid flow path 16B, and is then cooled in the condenser 14, so that the liquid fluid 20 exits the condenser 14 and enters the input side fluid flow path 16A. Head for. Thus, an autonomous circulating flow of fluid 20 along directions 28A, 28B can be obtained within system 10.

  Those skilled in the art will appreciate that upon reading and fully understanding the present disclosure, the condenser 14 may take other forms without departing from the scope thereof. For example, although the condenser 14 is shown to operate as a liquid-air heat exchanger, it may alternatively be in the form of a heat sink, another semiconductor die, or other heat exchange device, for example.

  The fluid 20 is, for example, water, fluorinate (fluorine-based inert fluid), or alcohol. Other liquids having suitable temperature and pressure phase change characteristics may be used.

  FIG. 2 is a cross-sectional view of the input side fluid flow path 16A for further explaining the wicking structure 26. FIG. The wicking structure 26 may be, for example, a thermally conductive fiber (eg, copper fiber), a thermally conductive powder (eg, copper powder), or a thermally conductive mesh filter (eg, a copper mesh filter), etc. This is a conductive porous material. This causes a fluid capillary force that draws the fluid 20 from the condenser 14 through the input side fluid flow path 16A to the input side manifold 24A. In one embodiment, the wicking structure 27 is also incorporated into the input manifold 24A to further increase the fluid capillary force from the condenser 14 to the semiconductor die 12. The wicking structure 27 may be the same as or different from the wicking structure 26. As long as it exerts a capillary action on the fluid, the wicking structures 26 and / or 27 can be, for example, fibrous materials (eg, metal fibers), microgrooves (eg, in the fluid flow path 16A and / or the input manifold 24A). Other materials or structures may be used, including microgrooves), sintered materials (sintered metal), porous or foamable plastics, non-metallic porous materials, and metal matrices.

  In FIG. 2, the cross-sectional shape of the input side fluid flow path 16 </ b> A is shown as a circle, but it is obvious that the input side fluid flow path 16 </ b> A may alternatively be a rectangle or another shape without departing from the scope of the present invention. .

  FIG. 3 shows a cross-sectional view (not to scale) of the semiconductor die 12 in which the microchannel 18 is formed by etching (as indicated by the etching line 18A). A silicon plate 30 (eg, glass) is used to seal the microchannel 18 to form a fluid channel for the fluid 20 (for illustration purposes, the plate 30 is also shown in FIG. 1).

  Still referring to FIG. 1, the system 10 has been “pre-filled” by filling the closed loop volume of the microchannel 18, condenser 14, and fluid channels 16A, 16B to at least about 50% with fluid (of the system). It may be ensured that the semiconductor die 12 (as “evaporator”) is “wet” in advance before operation. Further, the condenser 14 is disposed above the semiconductor die 12 so that the vapor generated by the interaction between the fluid 20 and the semiconductor die 12 moves upward to the condenser 14 through the input-side fluid flow path 16A. The cooled fluid 20 may be assisted by gravity to flow downwardly through the output fluid passage 16B to the semiconductor die 12.

  FIG. 4 is a perspective view of the semiconductor die 12 illustrating an exemplary embodiment of the microchannel 18 formed between the semiconductor die 12 and the plate 30 (shown in a transparent manner for purposes of explanation). ing. A plurality of openings 32A are formed on the input side of the semiconductor die 12 and connected to the input side manifold 24A, and a plurality of openings 32B are formed on the output side of the semiconductor die 12 and connected to the output side manifold 24B. As described in relation to FIG. 9, the opening 32B is made larger than the opening 32A to promote the preferential flow of fluid along the direction 34 corresponding to the fluid flow directions 28A and 28B of FIG. You may make it do.

  FIG. 5 illustrates one loop thermosyphon system 10 (1) according to one embodiment. FIG. 7 shows another loop thermosyphon system 10 (2) according to another embodiment. FIG. 9 shows another loop thermosyphon system 10 (3) according to another embodiment. In FIGS. 5, 7, and 9, the same numbers as those in FIGS. 1 to 4 provide similar functions.

  For example, in FIG. 5, an orifice 36 (see FIG. 6) is placed in one or more of the microchannels 18 (1) to provide preferential fluid flow through the semiconductor die. In particular, the semiconductor die 12 (1) of FIG. 5 has an orifice 36 disposed at each inlet of the microchannel 18 (1) (for example, at the input side opening 32A (1)), A preferential fluid flow along direction 34 is generated. FIG. 6 shows an embodiment of the orifice 36 in one opening 32A (1). Although not essential, a wicking structure such as the wicking structure 26 of FIG. 1 may be incorporated into the input side fluid flow path 16A (1) and / or the input side manifold 24A (1).

  In particular, FIG. 6 shows an orifice 36 formed by one microchannel 18 (1) of a semiconductor die 12 (1) and a blocking material 38 (eg, metal, plastic plating, or similar material), A cross-sectional view of a square orifice 36 that prevents fluid from entering the microchannel 18 (1) (other than through the orifice 36) is shown. Orifice 36 may be formed in other shapes as a design choice. The micro flow path 18 (1) in FIG. 6 is sealed by a plate 30 (1), and in a closed loop having fluid flow paths 16A (1) and 16B (1), the fluid flows in the micro flow of the semiconductor die 12 (1). It flows through the path and through the orifice 36. Since there is no restriction or orifice in the output side manifold 24B (1), the fluid in the microchannel 18 (1) flows preferentially along the direction 34.

  As shown in FIG. 7, the orifice 36 may be replaced with other fluid flow restricting materials. In FIG. 7, a fluid flow restricting material 46 (eg, a metal mesh filter, a non-metallic porous material, or a porous metal such as sintered copper or a metal matrix, in one or more of the microchannels 18 (2). Material) is disposed to achieve preferential fluid flow through the semiconductor die. In particular, the semiconductor die 12 (2) of FIG. 7 has a material 46 disposed at each inlet of the microchannel 18 (2) (eg, at the input side opening 32A (2)), A preferential fluid flow along direction 34 is generated. FIG. 8 shows an embodiment of the limiting material 46 in one input side opening 32A (2). Although not essential, a wicking structure such as the wicking structure 26 of FIG. 1 may be incorporated in the input side fluid flow path 16A (2) and / or the input side manifold 24A (2).

  In particular, FIG. 8 shows a cross section of one microchannel 18 (2) of a semiconductor die 12 (2) and a fluid flow restricting material 46 in the form of a mesh filter that limits fluid flow into the microchannel 18 (2). FIG. The microchannel 18 (2) of FIG. 8 is sealed by a plate 30 (2), and in a closed loop having fluid channels 16A (2), 16B (2), fluid passes through the fluid flow restricting material 46 and the semiconductor die 12 flows. It is designed to flow through the microchannel (2). Preferential flow along direction 34 is achieved by placing fluid flow restricting material 46 at the inlet of microchannel 18 (2).

  In FIG. 9, the microchannel 18 (3) is configured in a shape that realizes a preferential fluid flow along the direction 34. In other words, the micro flow path 18 (3) has an opening 32A (3) in the input side manifold 24A (3) smaller than the opening 32B (3) in the output side manifold 24B (3), and the micro flow path for the fluid flow. Is formed by etching so as to reduce the resistance in the direction 34. Therefore, the cross-sectional area of the micro flow path 18 (3) decreases as it approaches the input side manifold 24A (3), and increases as it approaches the output side manifold 24B (3). Although not essential, a wicking structure such as the wicking structure 26 of FIG. 1 may be incorporated into the input side fluid flow path 16A (3) and / or the input side manifold 24A (3).

  FIG. 10 shows one process 50 for cooling a semiconductor die as an evaporator in a loop thermosyphon system. In step 52, fluid is carried by capillary action from a condenser (eg, condenser 14 of FIG. 1) and flows into one or more microchannels in a semiconductor die (eg, semiconductor die 12 of FIG. 1). . An example of step 52 is to apply the wicking structure 26 of FIG. 1 in an input side fluid channel (eg, input side fluid channel 16A) that connects the condenser to the microchannel. Another example of step 52 is to apply a wicking structure in the input side manifold (eg, input side manifold 24A) between the input side fluid flow path and the micro flow path. In step 54, the heated fluid (or steam, or a mixture of fluid and steam) is conveyed to the condenser. An example of step 54 is to use an output side fluid flow path 16B that carries the heated fluid from the micro flow path to the condenser. In step 56, the liquid is cooled in the condenser. Steps 52, 54, and 56 may be repeated as necessary (58) to continue cooling the semiconductor die. Process 50 ends when the semiconductor die no longer needs to be cooled.

  Changes can be made in the above methods and systems without departing from the scope of the present invention. Accordingly, the above description and accompanying drawings are to be construed as illustrative rather than restrictive, and it is intended that the appended claims cover the generic and individual features of the features described herein. Is done.

1 is a schematic diagram of one loop thermosyphon system having a wicking structure and a semiconductor die as an evaporator. FIG. It is sectional drawing of the fluid flow path which has a wicking structure. It is a side view of one semiconductor die which has a plurality of microchannels. FIG. 4 is a perspective view of the semiconductor die of FIG. 3. It is the schematic explaining operation | movement of one thermosiphon system which has an orifice in the microchannel of a semiconductor die. It is sectional drawing of one microchannel with an orifice. FIG. 6 is a schematic diagram illustrating the operation of one thermosyphon system having a fluid flow restricting material in a microchannel of a semiconductor die. FIG. 6 is a cross-sectional view of one microchannel having a fluid flow restricting material. It is the schematic explaining operation | movement of one thermosiphon system which has the microchannel by which the semiconductor die was shape | molded. 6 is a flowchart illustrating one process for cooling a semiconductor die as an evaporator in a loop thermosyphon system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Loop thermosiphon system 12 Semiconductor die 14 Condenser 16A Input side fluid flow path 16B Output side fluid flow path 18 Micro flow path 20 Fluid 26 Wicking structure 30 Plate

Claims (10)

A semiconductor die having a plurality of microchannels;
A condenser fluidly connected to the microchannel;
A wicking structure that transports fluid between the condenser and the semiconductor die by capillary action;
A loop thermosyphon system characterized by comprising:   An input-side manifold connected to the semiconductor die; and an input-side fluid flow path connecting between the condenser and the input-side manifold; and the condensation by the input-side fluid flow path and the input-side manifold. 2. The loop heat according to claim 1, wherein a fluid is carried from a container to the micro flow path, and the wicking structure is provided in one or both of the input side fluid flow path and the input side manifold. Siphon system.   The loop thermosyphon system of claim 1, further comprising a plate coupled to the die to seal the microchannel and allow fluid to flow through the microchannel.   2. The loop thermosyphon system according to claim 1, wherein the microchannel has a shape such that a fluid flows preferentially along one direction of the microchannel.   The loop thermosyphon system according to claim 1, further comprising means for allowing fluid to flow preferentially along one direction of the microchannel. A semiconductor die having a plurality of microchannels, wherein one or more of the microchannels are shaped such that fluid preferentially flows along one direction of the semiconductor die Die,
A condenser fluidly connected to the microchannel, for cooling the heated fluid from the semiconductor die and flowing into the microchannel;
A loop thermosyphon system characterized by comprising: A semiconductor die having a plurality of microchannels;
At least one orifice provided at the inlet of at least one of the microchannels and allowing fluid to flow preferentially along one direction of the at least one microchannel;
A condenser fluidly connected to the microchannel, cooling the heated fluid from the semiconductor die and flowing into the microchannel;
A loop thermosyphon system characterized by comprising:   8. The loop heat of claim 7, further comprising a wicking structure disposed between the condenser and the semiconductor die and carrying a fluid from the condenser to the microchannel by capillary action. Siphon system. Carrying the fluid from the condenser by capillary action into one or more microchannels of the semiconductor die;
Conveying heated fluid from the semiconductor die to the condenser;
Cooling a fluid in the condenser;
A method for cooling a semiconductor die, comprising: Forming the microchannel into a shape such that fluid preferentially flows along the microchannel;
Forming an orifice at one or more inlets of the microchannels to allow fluid to flow preferentially along the one or more microchannels; and Disposing a fluid flow restricting material at one or more of the inlets to allow fluid to flow preferentially along the one or more microchannels;
10. The method for cooling a semiconductor die according to claim 9, further comprising at least one of the following steps.

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