JP2008262974A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device having a heat-dissipating function using a heat pipe. <P>SOLUTION: A chip unit 10 has semiconductor chips 11, metallic wirings 23 supporting the semiconductor chips, wiring supporting substrates 22 supporting the metallic wirings 23 and a heat pipe 40 connected to the wiring supporting substrates 22 in a thermally conductible manner. The chip unit 10 further has a heat sink member 21 connected to the wiring supporting substrates 22 and the heat pipe 40 in the thermally conductible manner and exposed in a region making an external heat exchanging medium flow. The heat sink member 21 and the wiring supporting substrates 22 are composed of a material having the small difference of a coefficient of thermal expansion with the semiconductor chips 11 and having a thermal conductivity higher than the semiconductor chips 11. The heat pipe 40 is extended up to a region protruded from a natural heat-dissipating region, and cooled by the central section 21A and side sections 21B of the heat sink member 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device in which a heat pipe is mounted, and particularly to a device suitable for a power device.

  In recent years, modules using IGBTs or FETs have been used as power devices (semiconductor devices) including motor-driven switching elements such as electric vehicles, hybrid vehicles, and fuel cells. In particular, in-vehicle semiconductor devices require a cooling structure with a small area and a large heat dissipation function because of the demand for miniaturization.

  As a cooling structure with a small area and a large heat dissipation function, Patent Document 1 discloses that a heat pipe is embedded in the lid of the semiconductor package to reduce the thermal resistance to the lateral flow of the heat flux passing through the lid of the semiconductor package. A structure is disclosed. Patent Document 2 discloses a structure that attempts to increase the cooling efficiency of the heat pipe by directly attaching fins to the heat pipe.

JP-A-11-233698 Japanese Patent Laid-Open No. 06-268123

  However, with the technologies of Patent Documents 1 and 2, it is difficult to secure a heat radiation amount that can cope with the reduction in size and the increase in power required for an in-vehicle semiconductor device using an SiC device or the like. For example, the technique of Patent Document 1 is a structure in which an electrode is provided only on one surface of a semiconductor chip, and it is difficult to expand the application range to an in-vehicle power device. Moreover, with the technique of patent document 2, the contact area of a fin and a heat pipe becomes small, and sufficient heat dissipation cannot be obtained.

  An object of the present invention is to provide a semiconductor device that can exhibit a high cooling effect by effectively utilizing the heat dissipation function of a heat pipe.

  In the semiconductor device of the present invention, a heat pipe is connected to a wiring support substrate of a semiconductor chip so as to be able to conduct heat, and a heat sink member is connected to the wiring support substrate and the heat pipe so as to be able to conduct heat.

  Thereby, since it has a connection structure capable of heat conduction between the wiring support substrate and the heat pipe, between the heat sink member and the heat pipe, and between the heat sink member and the wiring support substrate, as a whole, between the semiconductor chip and the heat exchange medium. Therefore, the heat dissipation function can be improved.

  By extending the heat pipe to the area that protrudes from the natural heat dissipation area of the semiconductor chip, the area where the heat generated in the semiconductor chip is released via the heat pipe is expanded to an area wider than the natural heat dissipation area. Therefore, the heat dissipation function is improved.

  Since a part of the heat pipe is bent toward the region through which the external heat exchange medium flows, the flow path through which the external heat exchange medium flows can be efficiently used to maintain the heat dissipation function and Miniaturization can be achieved.

  Since the heat sink member is divided into a plurality of portions, manufacturing can be facilitated.

  As the semiconductor element formed in the semiconductor device is a power device using a wide band gap semiconductor, even if the operating temperature range of the chip is expanded, the thermal stress is minimized and the reliability of the connection is maintained. However, an excessive temperature rise of the power device can be prevented by the high heat dissipation function.

  According to the semiconductor device of the present invention, a semiconductor device having a high heat dissipation function using a heat pipe can be obtained.

  FIG. 1 is a perspective view schematically showing a structure of a semiconductor device (power module) in an embodiment. As shown in the figure, the semiconductor device of this embodiment is configured by joining a chip unit 10 on a radiator 50. The radiator 50 includes a top plate 50a and a container 50b joined to the top plate 50a. The top plate 50a is provided with a number of rectangular through holes for incorporating the chip unit 10 therein. In the present embodiment, a large number of rectangular through holes are provided, but only one may be provided. The top plate 50a and the container 50b constituting the radiator 50 are made of aluminum or an aluminum alloy, and can be manufactured by die casting, extrusion, forging, casting, machining, or the like. Although not shown in FIG. 1, a resin case (see FIG. 3) is attached on the top plate 50a.

  In the assembly process of the present embodiment, after the chip unit 10 is mounted on the top plate 50a of the radiator 50, the top plate 50a is joined to the container 50b. This joining may be performed by mechanical caulking or the like. Further, in the present embodiment, the radiator 50 is formed by individually forming the top plate 50a and the container 50b and then joining them together, but the top plate and the container may be integrally formed. In that case, the radiator can be formed, for example, by die casting using an integral type. Thereafter, a resin case is attached to the top plate 50a by screwing or the like.

  FIG. 2 is a plan view of the semiconductor device according to the embodiment. 3 is a cross-sectional view of the semiconductor device according to the embodiment taken along line III-III shown in FIG. 4 is a cross-sectional view taken along line IV-IV shown in FIG. 2 of the semiconductor device of the embodiment. However, in FIGS. 2 to 4, the wiring structure and the resin case are not shown. Also, illustration of members that are not essential elements of the present invention, such as solder layers and metallized layers, is omitted for the sake of clarity. Hereinafter, the structure of the semiconductor device will be described with reference to FIGS.

  In the semiconductor device of the present embodiment, cooling water as a heat exchange medium flows in the flow path 51 between the top plate 50a and the container 50b of the radiator 50 in the direction indicated by the broken line arrow in FIG. The chip unit 10 includes, as main members, a semiconductor chip 11 in which semiconductor elements such as diodes and IGBTs are formed, a heat sink member 21 for releasing heat generated in the semiconductor chip 11 to the outside, and a back surface of the semiconductor chip 11. Metal wiring 23 joined to the electrode 14 via a solder layer (not shown) and formed from a metal plate such as Cu or Al, a metallized layer (not shown) and a solder layer formed on the main surface and the back surface A wiring support substrate 22 made of AlN, joined to the metal wiring 23 via the heat sink 40, a heat pipe 40 connected to the wiring support substrate 22 so as to be thermally conductive, and capable of conducting heat to the wiring support substrate 22 and the heat pipe 40. And a heat sink member 21 connected thereto. In the present embodiment, the semiconductor chip 11 is formed with a diode and an IGBT (or MOSFET), and the back electrode 14 of the semiconductor chip 11 is connected to an active region of a semiconductor element such as a diode or IGBT. . Further, the main surface of the semiconductor chip 11 is provided with a control signal electrode and an upper surface electrode, which are not shown.

  As shown in the partially enlarged view of FIG. 4, the heat sink members 21 </ b> A and 21 </ b> B have grooves, and the heat pipes 40 are embedded in the grooves and the flat plate of the heat sink members 21 </ b> A and 21 </ b> B by the brazing material layer 41. It is joined to the part 21a. Further, the wiring support substrate 22 is joined to the flat plate portion 21a of the heat sink members 21A and 21B and the heat pipe 40 by a brazing material layer 41. With this structure, the wiring support substrate 22 and the heat pipe 40 are connected to each other so as to be able to conduct heat, and the heat sink members 21A and 21B are connected to the wiring support substrate 22 and the heat pipe 40 so as to be able to conduct heat. Here, “connected so that heat conduction is possible” means a member such as a resin having a low thermal conductivity (for example, a resin having a thermal conductivity of less than 1 (W / m · K) and increased heat conduction due to filler mixing. This means that the thermal resistance can be reduced as much as possible by interposing only the solder layer, the brazing material layer, the metallized layer, and the like.

  The heat pipe 40 may be commercially available inside, for example, one described in Patent Document 1. Generally, a wick for promoting the circulation of an internal heat exchange medium (for example, alcohols, water, naphthalene, etc.) is provided inside the heat pipe 40 using capillary action. The internal heat exchange medium can be appropriately selected in consideration of the operating temperature range, cooling capacity, and the like. As shown in FIG. 5, the wick includes a mesh-like wick made of a mesh provided on the inner wall of the heat pipe, a groove-like wick formed by forming fine grooves on the inner wall of the heat pipe, a composite wick in which both are combined, Any of these may be used.

  In the present embodiment, the heat sink member 21 is formed by joining three divided members of a central portion 21A and two side portions 21B on both sides thereof. The central portion 21A includes a region (hereinafter referred to as “natural heat dissipation region”) that expands at an inclination angle of 45 ° from the semiconductor chip 11 to the flow path 51 that is a region through which an external heat exchange medium (for example, water or glycols) flows. In other words, it is made of a relatively expensive material such as Si—SiC or AlN, which has a low thermal expansion coefficient and high thermal conductivity. The side portion 21B does not include a natural heat dissipation region and is made of a relatively inexpensive material such as Cu or Al. Further, both the central portion 21A and the side portion 21B of the heat sink member 21 have a flat plate portion 21a and a fin portion 21b protruding from the back surface side of the flat plate portion 21a to a region where the external heat exchange medium flows. The heat sink member 21 is joined to the top plate 50a by a brazing material layer 25 made of an aluminum-silicon based brazing material.

  According to the present embodiment, the heat generated in the semiconductor chip 11 inside the heat pipe 40 is released to the internal heat exchange medium through the pipe wall of the metal wiring 23 -the wiring support substrate 22 -the heat pipe 40, The heat exchange medium evaporates. A large cooling action is obtained by this heat of vaporization. The evaporated internal heat exchange medium moves to the side in the heat pipe 40 and is condensed and liquefied. Thereafter, the liquefied internal heat exchange medium returns to the evaporated region through a wick or the like. In the present embodiment, the heat pipe 40 is connected to the wiring support substrate 22 so as to be able to conduct heat, and the heat sink members 21A and 21B are connected to the wiring support substrate 22 and the heat pipe 40 so as to be able to conduct heat. The heat transmitted to the 11-metal wiring 23-wiring support substrate 22 branches into a heat radiation path flowing from the heat pipe 40 to the heat sink member 21 and a heat radiation path flowing directly to the heat sink member 21. Thus, since the heat dissipation path is configured to expand more widely, the overall heat dissipation function of the semiconductor device is improved.

  When there is no heat pipe 40, heat dissipation to the external heat exchange medium in the heat sink member 21 in the area outside the area that expands at an inclination angle of 45 ° from the semiconductor chip 11 to the area through which the external heat exchange medium flows, Almost does not contribute to cooling of the semiconductor chip 11. Therefore, in this specification, the “region that expands at an inclination angle of 45 ° from the semiconductor chip to the region through which the external heat exchange medium flows” is defined as “natural heat dissipation region”.

  However, in the present embodiment, the heat pipe 40 extends in a direction orthogonal to the flow of the external heat exchange medium to a side that is far from the natural heat dissipation region. Therefore, the internal heat exchange medium evaporated in the region immediately below the semiconductor chip inside the heat pipe 40 is condensed in the side region of the heat pipe 40 by heat exchange with the heat sink 21 (particularly, the side portion 21B). Liquefaction. Thereafter, the liquefied internal heat exchange medium returns to a region directly below the semiconductor chip through a wick or the like. That is, in the heat pipe 40, heat is carried between a region directly below the semiconductor chip and a region located on the side thereof. Therefore, the heat radiation path flowing from the heat pipe 40 to the heat sink member 21 is expanded to include not only the natural heat radiation region but also the side region thereof. The expansion of the heat radiation area can improve the cooling function. In that case, the heat pipe 40 extends in the direction intersecting the flow of the external heat exchange medium (in the present embodiment, the direction orthogonal), whereby the heat exchange amount in each part in the flow path 51 of the container 50b. Can be distributed uniformly, and the cooling function can be greatly improved.

  In the present embodiment, the material of the central portion 21A of the heat sink member 21 is nitride ceramics such as AlN, BN, SiN, GaN, carbide ceramics such as SiC, WC, Si-SiC, Al-SiC, or the like. It is comprised by the composite ceramics. Although not limited to these materials, it is preferable to limit to these materials for the following reasons. For example, the thermal expansion coefficient α of AlN is about 4.5 (ppm / K), the thermal conductivity is about 200 (W / m · K), and the thermal expansion coefficient α of Si—SiC is about 2.3-3. (Ppm / K), thermal conductivity is about 200 (W / m · K), thermal expansion coefficient α of SiC is about 3 (ppm / K), and thermal conductivity is about 210 (W / m · K). The thermal expansion coefficient α of GaN is about 3.2 or 5.6 (ppm / K), and the thermal conductivity is about 130 (W / m · K). Therefore, these heat-dissipating materials are much larger than the thermal conductivity of general-purpose ceramics such as alumina, and have a thermal conductivity close to that of aluminum (thermal conductivity of about 240 (W / m · K), while being thermally expanded. The coefficient α is much smaller than aluminum (α≈23 (ppm / K)), and the thermal expansion coefficient α of the semiconductor chip (approximately 3 (ppm / K) for Si single crystal, approximately 4 (ppm / K) for SiC single crystal. Therefore, by configuring the central portion 21A of the heat sink member 21 with the nitride ceramics, carbide ceramics, or composite ceramics, it is possible to minimize the thermal stress while maintaining a large heat transfer amount. .

  On the other hand, since the side portion 21B of the heat sink member 21 is not located directly below the semiconductor chip 11, even if the difference in thermal expansion coefficient from the semiconductor chip 11 is large, it does not cause so much thermal stress. . Therefore, the side portion 21B can be made of Al and Cu, which are relatively inexpensive materials, and the manufacturing cost can be reduced. In particular, Cu has a thermal conductivity of 393 (W / m · K), and the side portion 21B is made of Cu, thereby reducing the manufacturing cost and improving the heat exchange efficiency at the side of the heat pipe 40. Can also be realized. However, it is not always necessary to divide the heat sink member 21, and the heat sink member 21 may be integrally formed of the same material.

  In the case where a part or the whole of the heat sink member 21 is made of AlN, SiN, GaN, BN, SiC, WC, Si—SiC, Al—SiC, or the like, in a region for joining with other members, By forming the metallized layer, soldering and brazing can be easily performed.

  The material of the metal wiring 23 is not limited to Cu or Al. For example, you may use metals, such as Cu-Mo and CuW. The thermal expansion coefficient α of Cu—Mo is about 6.5 to 8 (ppm / K), the thermal conductivity is about 200 (W / m · K), and the thermal expansion coefficient α of Cu—W is about 6.5. -7 (ppm / K), thermal conductivity is 180-200 (W / m · K). The thermal conductivity of these composite materials is much lower than that of Cu (about 400 (W / m · K)), but is close to that of aluminum (Al), while the thermal expansion coefficient α is , Much smaller than the thermal expansion coefficient α (≈17) of Cu and close to the thermal expansion coefficient α of the semiconductor chip (about 3 (ppm / K) for Si and about 4 (ppm / K) for SiC). Therefore, by configuring the metal wiring 23 from Cu—Mo or Cu—W, it is possible to reduce the thermal stress as much as possible while maintaining a large heat transfer amount.

  The external heat exchange medium that exchanges heat with the heat sink member 21 is preferably water in consideration of cooling ability and cost. However, instead of water, a gas such as helium, argon, nitrogen, or air may be used.

(Modification)
6 is a cross-sectional view of a semiconductor device according to a modification of the embodiment (corresponding to a cross section taken along line III-III shown in FIG. 2). In this modification, the heat pipe 40 is bent at right angles along the container 50b on both sides. The heat sink member 21 is divided into a central part 21A and two side parts 21B. The fin part 21b of the central part 21A extends in the vertical direction, but the fin part 21b of the side part 21B Extending in the direction. The structure of other members is as shown in FIGS. 2 to 5, and the same reference numerals are given and description thereof is omitted.

  According to this modification, the heat pipe 40 is bent, and the fin portion 21b of the heat sink member 21B is configured to extend in the lateral direction, so that the flow path 51, which is the region through which the external heat exchange medium flows, is utilized to the maximum extent. Since the heat exchange efficiency can be increased, the heat dissipation function can be improved while downsizing the semiconductor device. It should be noted that the heat pipe may be branched downward from a portion located in the middle of the two semiconductor chips 11 of the heat pipe 40.

(Other embodiments)
The structure of the embodiment of the present invention disclosed above is merely an example, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  In the above embodiment, the fin members 21A and 21B both have the flat plate portion 21a and the fin portion 21b. However, both or one of the heat sink members 21A and 21B has the fin portion. It may not be only a flat plate part.

  In the above-described embodiment, a structure in which the heat pipe 40 is fitted into the groove formed in the heat sink member 21 is adopted, but it is not necessarily limited to this structure. If the connection structure between the heat pipe 40 and the heat sink member 21, the connection structure between the wiring support substrate 22 and the heat pipe 40, and the connection structure between the wiring support substrate 22 and the heat sink member 21 are connected so as to be capable of heat conduction, A connection structure other than the embodiment can be employed.

  In the above embodiment, the structure in which the two semiconductor chips 11 are mounted above the heat pipe 40 is employed. However, the number of semiconductor chips mounted above the heat pipe 40 may be one, or 3 There may be more than one.

  When the semiconductor device of the present invention is applied to a device having a power device using a wide band gap semiconductor (SiC, GaN, etc.), a switching operation or the like is performed at a temperature higher than the operating temperature of the Si device, and the chip temperature is 150 °. Even when the temperature reaches C or more, an excessive temperature rise of the power device can be prevented by a high heat radiation function while maintaining the reliability of the connection portion by reducing the thermal stress as much as possible, and the effect can be obtained. .

  In the above embodiment, the diode and the IGBT are formed on the semiconductor chip 11. However, in addition to the diode, a semiconductor chip on which a MOSFET, a JFET, or the like is formed may be used. Moreover, you may form a diode and IGBT, MOSFET, or JFET in a separate chip | tip.

  The semiconductor device of the present invention can be used in various devices equipped with MOSFETs, IGBTs, diodes, JFETs and the like.

1 is a perspective view illustrating a structure of a semiconductor device in an embodiment. It is a top view of the semiconductor device concerning an embodiment. It is sectional drawing in the III-III line | wire of the semiconductor device which concerns on embodiment. It is sectional drawing in the IV-IV line of the semiconductor device which concerns on embodiment. It is sectional drawing which shows the example of the wick in the heat pipe of embodiment. It is sectional drawing of the semiconductor device which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Chip unit 11 Semiconductor chip 14 Back surface electrode 21 Heat sink member 21A Center part 21B Side part 21a Flat plate part 21b Fin part 22 Wiring support substrate 23 Metal wiring 24 Heat sink member 25 Brazing material layer 40 Heat pipe 41 Brazing material layer 50 Radiator 50a Top plate 50b Container 51 Flow path 53 Resin case

Claims (5)

A semiconductor chip on which a semiconductor element is formed;
A wiring member connected to a part of the semiconductor chip;
A wiring support substrate for supporting the wiring member;
A heat pipe connected to the wiring support substrate so as to allow heat conduction;
A semiconductor device comprising: The semiconductor device according to claim 1,
The said heat pipe is a semiconductor device extended to the area | region which protruded from the natural thermal radiation area | region of the said semiconductor chip in the direction which cross | intersects the flow of an external heat exchange medium. The semiconductor device according to claim 1 or 2,
A part of the heat pipe is a semiconductor device bent toward a region where an external heat exchange medium flows. The semiconductor device according to claim 1,
The semiconductor device, wherein the heat sink is divided into a part including a natural heat dissipation region of the semiconductor chip and a part not including the natural heat dissipation path. In the semiconductor device according to claim 1,
The semiconductor device is a power device using a wide band gap semiconductor.

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