JP5554444B1 - Compound package cooling structure - Google Patents

Abstract

A cooling structure excellent in cooling performance of a semiconductor package configured by three-dimensionally mounting a semiconductor is provided.
In a composite cooling structure of a semiconductor package in which a plurality of layers of semiconductors 2, 4 and 5 are stacked on a mother board 1, the semiconductor layer 5 is heated to evaporate and dissipate heat. A vapor chamber type heat diffusion plate 8 filled with a working fluid to be condensed is disposed so as to transfer heat to and from the uppermost semiconductor 5, and a heat sink 11 is provided on the heat diffusion plate 8, and the heat diffusion is performed. The plate 8 extends toward the upper surface of the first semiconductor layer 2 disposed on the upper surface of the mother board 1 and has a leg 8b having a hollow structure that is in contact with the upper surface of the first semiconductor layer so as to be able to transfer heat. And a wick 9 in which the liquid-phase working fluid permeates and generates capillary force is housed in the heat diffusion plate 8 including the inside of the leg portion 8b.
[Selection] Figure 1

Description

  The present invention relates to a cooling structure for cooling a semiconductor package by promoting heat radiation from the semiconductor package, and more particularly to a structure for cooling a semiconductor package in which a plurality of chips are stacked in a three-dimensional direction. .

  Conventionally, a plurality of chips including a memory and a microcomputer and a silicon die are stacked and mounted, and such a technique is called three-dimensional mounting. These chips, silicon dies, and the like are connected by flip chip connection using bumps, through electrodes, or the like, and by this connection technology, chips and silicon dies having the same dimensions can be stacked.

  A semiconductor package configured by stacking chips or the like by three-dimensional mounting has a higher mounting density of elements and circuits, but has a smaller area in contact with surrounding air. Therefore, the amount of heat radiation per unit area of the outer surface that becomes the heat radiating surface increases, and if heat radiation is not performed reliably and sufficiently, the chip itself and the contacts etc. become abnormally or unevenly hot, causing malfunctions. There is a possibility. In addition, a three-dimensionally mounted semiconductor package requires a large surface for input / output of various signals such as electrical or optical signals in order to increase the function, which reduces the area for heat dissipation. It has become. And, the electrical performance and manufacturing method when three-dimensionally mounting in about 100 layers are actively researched, and at the same time, cooling is an important issue. When the layers are stacked in more layers, the thermal resistance between the lower layer chip and the outside air increases, and the temperature of the contact point in the chip increases accordingly. Conventionally, a semiconductor package or chip mounted in three dimensions is cooled by a cooling technique in two dimensions. For example, a heat diffusion plate is placed on a semiconductor chip stacked in multiple layers on a substrate or mother board, with a heat transfer material interposed, and heat is transferred to the heat sink via the heat diffusion plate. Is configured to do. However, in such a configuration, the semiconductor package mounted three-dimensionally cannot always be sufficiently cooled. On the other hand, Patent Document 1 describes a semiconductor device in which two types of semiconductor chips are superposed, sandwiched between metal heat transfer plates, and a refrigerant tube is disposed outside thereof.

JP 2001-308245 A

  When stacking semiconductor chips, silicon dies, etc., an insulating layer may be provided between the layers. Since the insulating layer is inferior in thermal conductivity, temperature control of the semiconductor package is coupled with an increase in integration degree due to three-dimensional mounting. Becomes difficult. The cooling structure as described in Patent Document 1 described above is configured so that the semiconductor chips stacked in two layers are cooled by the refrigerant tubes provided on both sides thereof. It has a configuration in which two refrigerant tubes are provided. This is not different from the conventional cooling technology of a two-dimensionally mounted semiconductor package, and its cooling capacity is not necessarily high, such as its heat dissipation area being limited, so when used for cooling a three-dimensionally mounted semiconductor package, There is a possibility that the temperature becomes high, and it is necessary to develop a technique suitable for cooling a three-dimensionally mounted semiconductor package.

  The present invention has been made paying attention to the above technical problem, and provides a composite cooling structure capable of sufficiently cooling a lower layer chip or a silicon die in a three-dimensionally mounted semiconductor package. It is for the purpose.

  In order to achieve the above object, the invention according to claim 1 is a semiconductor package composite cooling structure in which a plurality of semiconductors are stacked on a mother board, and is heated and evaporated on the uppermost semiconductor. And a vapor chamber type heat diffusion plate filled with a working fluid that dissipates heat and condenses is disposed so as to transfer heat to and from the uppermost semiconductor, a heat sink is provided on the heat diffusion plate, and the heat The diffusion plate includes a leg portion having a hollow structure that extends toward the upper surface of the first layer semiconductor disposed on the upper surface of the motherboard and is in contact with the upper surface of the first layer semiconductor substrate so as to be able to transfer heat. The heat diffusion plate including the inside of the leg portion contains a wick that penetrates the liquid-phase working fluid and generates capillary force.

  According to a second aspect of the present invention, there is provided the composite cooling structure for a semiconductor package according to the first aspect, wherein another heat sink is disposed on the lower surface of the mother board so as to be able to exchange heat with the mother board.

  According to a third aspect of the present invention, in the second aspect of the present invention, the motherboard is provided with a heat transfer member that penetrates from the upper surface to the lower surface and transfers heat to the other heat sink. This is a composite cooling structure for a semiconductor package.

  According to the present invention, heat is generated when the stacked semiconductors operate. Since the vapor chamber type heat diffusion plate is arranged on the uppermost semiconductor side, the working fluid inside the heat diffusion plate takes heat from the semiconductor and evaporates, and the vapor spreads inside the heat diffusion plate. On the other hand, since the heat sink is arranged on the upper surface side of the heat diffusion plate, the upper surface of the heat diffusion plate is lower in temperature than the lower surface in contact with the semiconductor, and therefore the vapor of the working fluid is transferred to the upper surface of the heat diffusion plate. Contact with the heat dissipates and condenses. That is, the working fluid transports heat to the heat sink as its latent heat. Then, heat is radiated from the heat sink to the surrounding air.

  The heat diffusion plate includes a leg portion that comes into contact with the upper surface of the semiconductor of the first layer so that heat can be transferred, and the working fluid is also present inside the leg portion. Therefore, when the temperature of the first-layer semiconductor is low, the heat of the upper-layer semiconductor is transported to the first-layer semiconductor, and heat is dissipated using the first-layer semiconductor as a heat radiating portion. Can be cooled. Alternatively, when the temperature of the semiconductor of the first layer is high, the working fluid inside the legs takes heat from the semiconductor of the first layer and evaporates, and the heat is transferred to the upper heat sink to be dissipated. In this case, the thermal diffusion plate functions not only as an upper semiconductor layer but also as a heat dissipation means for the first semiconductor layer. The vapor chamber constituting the heat diffusing plate contains a wick that generates capillary pressure when the liquid-phase working fluid permeates therein. It is possible to sufficiently or reliably distribute the working fluid in order to perform necessary and sufficient heat transport from the semiconductor to the heat sink.

  Further, according to the present invention, since heat radiation from the semiconductor of the first layer can be promoted, even if a low melting point solder is used to avoid damage to the semiconductor due to heat during soldering, the solder is It is possible to prevent the occurrence of poor connection due to softening or melting.

It is typical sectional drawing for demonstrating the specific example of this invention.

  FIG. 1 is a cross-sectional view schematically showing a specific example of the present invention, in which a semiconductor package is formed by stacking a plurality of semiconductors on a mother board 1. The mother boat 1 has a conventionally known configuration, a circuit is formed on the upper surface thereof, and a ceramic substrate 2 that is a first layer semiconductor having electronic elements and circuits is provided on the upper surface side of the mother boat 1. Is arranged. The circuit of the ceramic substrate 2 and the circuit of the mother board 1 are connected by a low melting point solder 3 containing copper.

  On the ceramic substrate 2, a plurality of silicon dies 4, 5 having an outer dimension smaller than that of the ceramic substrate 2 (in other words, a smaller area) are stacked. These silicon dies 4 and 5 correspond to the upper layer semiconductor in the present invention, have electronic elements or circuits, and are connected to each other by flip chip connection using bumps 6 having a melting point higher than that of the solder 3. It is connected to the ceramic substrate 2.

  A vapor chamber heat diffusion plate 8 is disposed on the upper surface of the uppermost silicon die 5 with a heat transfer material 7 interposed therebetween. The heat transfer material 7 is a grease-like or thin-film-like material containing a material having a high thermal conductivity, and is conventionally known as a thermal interface material (TIM). The vapor chamber heat diffusion plate 8 is a hollow member that encloses a working fluid that is heated to evaporate and dissipates heat and condenses. In particular, in the example shown in FIG. 1, the vapor chamber heat diffusion plate 8 contacts the upper surface of the uppermost silicon die 5. And a leg portion 8b extending downward from the periphery of the flat plate portion 8a.

  The flat plate portion 8a is a hollow flat plate having a larger area than the upper surface of the silicon die 5, and a microchannel is formed in the flat plate portion 8a by providing a large number of partition plates in parallel with each other at a narrow interval. Yes. Further, the leg portion 8b is a hollow columnar or vertical wall-like portion, and the inside thereof communicates with the flat plate portion 8a. The lower surface of the leg 8b is in contact with the upper surface of the ceramic substrate 2 via the heat transfer material 9 so as to be able to transfer heat. Further, a wick 10 is disposed along the inner surfaces of the flat plate portion 8a and the leg portion 8b. The wick 10 is a porous structure that generates capillary pressure when a liquid-phase working fluid permeates, and is constituted by a sintered material such as copper particles as an example. The working fluid is generally water, and other fluids such as alcohol may be used instead.

  A heat sink 12 is brought into contact with the upper surface of the heat diffusion plate 8 via a heat transfer material 11. Since the heat sink 12 is for dissipating heat to the surrounding air, it may be a heat sink having a general structure having a large number of radiating fins. However, in the example shown in FIG. 1, a microchannel is formed. It is constituted by a cooling plate. Explaining its structure, it is formed as a hollow flat plate as a whole, and inside it is provided with a number of fins (or partition plates) arranged in parallel with each other at narrow intervals, and these fins provide slit-like ventilation. Many paths (channels) are formed.

  The heat sink 12 has a flange portion 13 protruding to the outer peripheral side, and the heat sink 12 is attached to the mother boat 1 via the flange portion 13. That is, at least two locations of the flange portion 13 are provided with fastening bolts 14 penetrating the flange portion 13 and the mother boat 1, and the spring 15 is interposed between the head of the fastening bolt 14 and the upper surface of the flange portion 13. And a nut 16 is fastened to the tip of the fastening bolt 14 protruding from the lower surface side of the mother boat 1. Therefore, the elastic force of the spring 15 acts as a load that brings the heat sink 12 and the mother boat 1 closer to each other, and as a result, the heat sink 12 is pressed against and contacts the upper surface of the heat diffusion plate 8. At the same time, the ceramic substrate 2, the silicon dies 4 and 5 stacked on the ceramic substrate 2, and the heat diffusion plate 8 are sandwiched between the mother boat 1 and the heat sink 12 by the elastic force of the spring 15. In FIG. 1, reference numeral 17 denotes a reinforcing plate provided on the upper surface of the mother boat 1.

  Further, another heat sink 18 is attached to the lower surface of the mother boat 1. This is for accelerating the heat radiation from the ceramic substrate 2 which is the first layer semiconductor that is likely to increase in temperature due to heat accumulation, and is similar to the heat sink 12 for radiating heat from the heat diffusion plate 8. Further, it is constituted by a microchannel type cooling plate. The other heat sink 18 is brought into contact with the lower surface of the mother boat 1 with the heat transfer material 19 interposed. The heat sink 18 has a flange portion 20 protruding to the outer peripheral side, and a tip end portion of a mounting screw 21 inserted into the flange portion 20 from the lower surface side is screwed into a nut 22 embedded in the mother boat 1. In addition, a spring 23 is interposed between the head of the mounting screw 21 and the lower surface of the flange portion 20, and the heat sink 18 is pressed against and adhered to the lower surface of the mother boat 1 by the spring 23.

  In order to promote heat conduction to the heat sink 18, the mother boat 1 is provided with a heat transfer member 24 called a thermal via. The heat transfer member 24 is a thin shaft-like or pin-like member made of a material having a high thermal conductivity such as a metal, and penetrates in the thickness direction at a position in the mother boat 1 avoiding electronic elements and circuits. The edge is embedded in a state where it is exposed on both the upper and lower sides.

  Next, the operation of the above composite cooling structure will be described. When the ceramic substrate 2 and the silicon dies 4 and 5 are energized and operated, heat is inevitably generated and the temperature rises. Part of the heat is dissipated from the respective surfaces to the surrounding air, and the other part is transferred from the ceramic substrate 2 to the heat diffusion plate 8 via the silicon dies 4 and 5 on the upper layer side. The heat causes the working fluid inside the heat diffusing plate 8 to evaporate, and the vapor flows to a location where the pressure is relatively low due to the low temperature, that is, to the upper surface side in contact with the heat sink 12. Then, the working fluid vapor dissipates heat and condenses by contacting the upper surface of the heat diffusion plate 8. The heat transferred to the heat sink 12 in this way is transferred to the surrounding air, and the heat sink 12 is cooled. Since the heat transfer from the uppermost silicon die 5 to the heat sink 12 is carried as latent heat of the working fluid in this way, the heat amount of the latent heat of the working fluid is large, so that the uppermost silicon die 5 and the heat sink are heated. Therefore, the entire semiconductor package is efficiently cooled.

  Further, in the above structure according to the present invention, the heat diffusing plate 8 has the above-described leg portion 8b, and is configured to mediate the transfer of heat from the ceramic substrate 2 to the heat sink 12. Heat can be transferred from the ceramic substrate 2 to the heat sink 12 without going through the large silicon dies 4 and 5, and the heat transfer is carried out by the working fluid sealed in the heat diffusion plate 8 as latent heat. Is done. Therefore, the thermal resistance between the ceramic substrate 2 and the heat sink 12 can be reduced, and the ceramic substrate 2 disposed in the lowermost layer can be effectively cooled. When the temperature of the ceramic substrate 2 is lower than the temperature of the uppermost silicon die 5, the vapor of the working fluid in the heat diffusion plate 8 descends in the legs 8b and enters the ceramic substrate 2. In contrast, it dissipates heat and condenses. That is, heat can be dissipated using the ceramic substrate 2 as a heat sink, and the uppermost silicon die 5 can be cooled. In that case, the condensed working fluid is refluxed upward by the wick 10 and heat transport by the working fluid is continued.

  In the example shown in FIG. 1, the lowermost ceramic substrate 2 is larger than the upper silicon dies 4 and 5 and generates a larger amount of heat. As described above, the heat is transmitted upward in FIG. 1 through the silicon dies 4 and 5, and is carried upward through the legs 8b. In addition to this, another heat sink 18 is attached to the lower surface of the mother boat 1, and a large number of heat transfer members 24 penetrating from the upper surface to the lower surface are embedded, so that the heat of the ceramic substrate 2 (especially the ceramic substrate 2 and the motherboard). 1) is transmitted to the heat sink 18 on the lower surface side and radiated to the surrounding air. In other words, the ceramic substrate 2 and its connecting portion to the mother board 1 are air-cooled through the heat sink 18 on the lower surface side. Therefore, even if the solder 3 used for the connection has a low melting point, it is possible to avoid problems such as poor connection.

  DESCRIPTION OF SYMBOLS 1 ... Mother board, 2 ... Ceramic substrate, 3 ... Solder, 4, 5 ... Silicon die, 6 ... Bump, 7 ... Heat transfer material, 8 ... Vapor chamber type thermal diffusion plate, 8a ... Flat plate part, 8b ... Leg part, 9 ... heat transfer material, 10 ... wick, 11 ... heat transfer material, 12 ... heat sink, 13 ... flange, 14 ... fastening bolt, 15 ... spring, 16 ... nut, 17 ... reinforcing plate, 18 ... other heat sink, 19 ... Heat transfer material, 20 ... flange portion, 21 ... mounting screw, 22 ... nut, 23 ... spring, 24 ... heat transfer member (thermal via).

Claims (3)

In a composite cooling structure of a semiconductor package configured by stacking a plurality of semiconductor layers on a motherboard,
A vapor chamber type heat diffusion plate in which a working fluid which is heated and evaporated and dissipates and condenses is disposed on the uppermost semiconductor so as to transfer heat to and from the uppermost semiconductor. A heat sink is provided on the heat diffusion plate, and the heat diffusion plate extends toward the upper surface of the first layer semiconductor disposed on the upper surface of the motherboard and contacts the upper surface of the first layer semiconductor so as to be able to transfer heat. A leg portion having a hollow structure, and a wick that allows the working fluid in a liquid phase to permeate and generate capillary force is accommodated in the heat diffusion plate including the inside of the leg portion. A combined cooling structure for semiconductor packages.   2. The composite cooling structure for a semiconductor package according to claim 1, wherein another heat sink is disposed on the lower surface of the motherboard so as to be able to exchange heat with the motherboard.   3. The composite cooling structure for a semiconductor package according to claim 2, wherein the mother board is provided with a heat transfer member that penetrates from the upper surface to the lower surface to transmit heat to the other heat sink.

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