JP2008300455A - Power module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power module which has high reliability of a joint portion. <P>SOLUTION: The power module is constituted by stacking an underlay conductive member 28 formed by a melt-spraying process (cold spraying process), a solder layer 14, and a semiconductor chip 11 in order on a metal wiring 23 made of a first material (Cu). The underlay conductive member 28 is formed by spraying a group of particles of a first material and a group of particles of a second material (Si, AL<SB>2</SB>O<SB>3</SB>, SiC, Si<SB>3</SB>N<SB>4</SB>, SiO<SB>2</SB>, AlN, W, Mo, invar alloy, etc.) having a thermal expansion coefficient smaller than that of the first material. The underlay conductive member 28 which has a thermal expansion coefficient smaller than that of the metal wiring 23 is interposed between the metal wiring 23 and solder layer 14, so that thermal stress due to the difference in thermal expansion coefficient between the upper and lower members which is applied to the solder layer 14 is reduced to suppress cracking of the solder layer 14. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power module having a heat dissipation function for heat generation of a semiconductor chip.

  As a power module having a heat dissipation function for heat generation of a semiconductor element as a power device, as disclosed in Patent Document 1, a bare chip is mounted on the upper surface of a wiring member by soldering, and the whole is molded by resin, thereby wiring. 2. Description of the Related Art There are known devices that attempt to suppress bare chip peeling due to thermal stress resulting from a difference in thermal expansion coefficient between a member and a bare chip.

Further, in Patent Document 2, by providing an electrically conductive layer in which hard particles having low thermal expansion and high thermal conductivity are added to a conductive base material on the upper surface of the wiring member portion (upper Al layer) of the DBA substrate, It is described that the thermal stress caused by the difference in thermal expansion coefficient between the wiring member and the semiconductor chip is reduced.
Japanese Patent No. 3516789 JP 2006-173591 A

  However, in the technique of Patent Document 1, it is difficult to resist the thermal stress caused by the difference in thermal expansion coefficient between the wiring member and the bare chip depending on the resin mold, and there is a possibility that a crack may occur. On the other hand, in the technique of Patent Document 2, it is possible to relieve the thermal stress caused by the difference in thermal expansion coefficient by providing Al layers above and below the AlN substrate, but it requires an expensive AlN substrate. There is a problem that the manufacturing cost is increased due to the complexity of the structure in which many layers are stacked.

  An object of the present invention is to provide an inexpensive power module in which the reliability of a joint portion is high by taking a means for reducing thermal stress applied to a solder layer without using a DBA substrate.

  The power module of the present invention is an underlying conductive member between the wiring member containing the first material such as Al, Al alloy, Cu, and Cu alloy as a main component and the semiconductor chip and as the foundation of the solder layer. A member including a first material and a second material having a smaller coefficient of thermal expansion than the first material is provided.

  Accordingly, the underlying conductive member interposed between the wiring member and the solder layer includes the first material that is the constituent material of the wiring member and the second material that has a smaller thermal expansion coefficient than the first material. Therefore, the base of the solder layer is an underlying conductive member having a smaller coefficient of thermal expansion than the wiring member. Therefore, it is possible to suppress cracks in the solder layer caused by thermal stress caused by the difference in thermal expansion coefficient between the upper and lower layers. Moreover, this structure does not require an expensive DBA substrate. Therefore, it is possible to provide an inexpensive power module with high reliability of the joint.

  When the composition ratio of the second material in the underlying conductive member is 20 to 70%, the thermal expansion coefficient can be adjusted within a range that does not impair the conductivity of the underlying conductive member.

  Due to the fact that the composition ratio of the first material in the underlying conductive member is larger as it is closer to the wiring member and the composition ratio of the second material is closer to the solder layer, it is caused by the difference in thermal expansion coefficient between the wiring member and the solder layer. Therefore, the generation of cracks in the solder layer can be more reliably suppressed, and the reliability of the joint portion is improved.

  Since the thermal expansion coefficient of the underlying conductive member is 10 ppm / K or less, the difference in thermal expansion coefficient from the semiconductor chip in the range of 3 to 6 ppm / K can be further reduced. It is possible to further reliably suppress cracks.

The second material is at least one substance selected from Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ , AlN, W, Mo, and Fe ₃₂ Ni ₅ Co (Invar alloy). Is preferred.

  Since the underlay conductive member is formed by a thermal spraying method, even if it is difficult to form a composite material, the underlay conductive member is easily combined by the treatment at a relatively low temperature to realize the underlay conductive member. Therefore, a power module with a high reliability of the joint by reducing thermal stress can be obtained.

  By further including a heat sink provided below the wiring member and an insulating resin layer that connects the wiring member and the heat sink, the structure of the power module is simplified, and the manufacturing cost is greatly reduced.

  According to the power module of the present invention, it is possible to provide an inexpensive power module with high bonding reliability.

(Embodiment)
FIG. 1 is a cross-sectional view of a power module set according to an embodiment. FIG. 2 is an enlarged cross-sectional view of a main part of the power module according to the embodiment. Hereinafter, the structure of the power module and the power module set will be described with reference to FIGS. 1 and 2.

  In the power module set of the present embodiment, cooling water as a heat exchange medium flows in a direction perpendicular to the paper surface in the space 51 between the top plate 50a and the container 50b of the radiator. The power module 10 is screwed to the top plate 50 a by bolts 54 while being kept airtight by the O-ring 25.

  The power module 10 includes a heat sink 21 having a flat plate portion 21a and fin portions 21b, an insulating resin layer 26 formed on the flat plate portion 21a, a metal wiring 23 formed on the insulating resin layer 26, and a metal wiring. 23, an underlying conductive member 28 formed on the semiconductor substrate 11, a semiconductor chip 11 installed above the underlying conductive member 28, and formed with a semiconductor element such as an IGBT, and formed between the underlying conductive member 28 and the semiconductor chip 11. And a solder layer 14 containing Pb-free solder.

  The metal wiring 23 electrically connects the semiconductor element in the semiconductor chip 11 and an external member. On the upper surface and lower surface of the semiconductor chip 11, an upper surface electrode 12 and a rear surface electrode 13 connected to an active region of a semiconductor element such as an IGBT are provided. The back surface electrode 13 of the semiconductor chip 11 is joined to the underlying conductive member 28 in a conductive state by the solder layer 14. In this manner, the back electrode 13 of the semiconductor chip 11 and the metal wiring 23 are electrically connected via the underlying conductive member 28.

  A module resin frame 53 surrounding the semiconductor chip 11 and the like is provided on the top plate 50 a of the radiator, and the module resin frame 53 is fixed to the top plate 50 a by bolts 54. An electrode terminal layer 56 (bus bar) is provided on the inner and outer surfaces of the module resin frame 53 by integral molding. The electrode terminal layer 56 and the metal wiring 23 are connected by the high power wiring 18, and the electrode terminal layer 56 and a part of the upper surface electrode 12 of the semiconductor chip 11 are connected by the signal wiring 17. As a result, the power module 10 and the external device can be electrically connected. Further, a gel layer 40 made of silicon gel is provided on the inner side of the module resin frame 53, and the semiconductor chip 11, the signal wiring 17, the high power wiring 18, the metal wiring 23, the solder on the upper surface side of the heat sink 21. Members such as the layer 14 and the insulating resin layer 26 are embedded in the gel layer 40.

  In the present embodiment, the heat sink 21 is formed by die casting using Al or an Al alloy. However, an extruded product or a heat sink obtained by machining an extruded product may be used. The fin portion 21b of the heat sink 21 is configured to be exposed to cooling water, which is a heat exchange medium, so as to increase heat exchange efficiency. However, the fin portion 21b is not always necessary, and instead of the fin portion 21b. Other power modules may be provided.

The metal wiring 23 is made of Cu, which is a first material, and is a wiring member serving as a base for the underlying conductive member 28. The underlying conductive member 28 includes the first material (Cu) and a second material (Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ ) having a smaller thermal expansion coefficient than the first material. , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (Invar alloy), etc.), and is formed using a cold spray method. As will be described later, the underlying conductive member 28 formed using the cold spray method is formed at a relatively low temperature (several hundred degrees Celsius). In addition, it has been confirmed that the film formed using the cold spray method is dense. In the cold spray method, the deposition efficiency of the film is large, and the manufacturing cost is low. The thickness of the semiconductor chip 11 is 0.3 mm to 0.5 mm, the thickness of the underlying conductive member is about 0.5 mm, the thickness of the solder layer 14 is about 0.1 mm, and the thickness of the metal wiring 23 is The thickness of the insulating resin layer 26 is about 0.2 mm, the thickness of the flat plate portion 21a of the heat sink 21 is about 5 mm, and the length of the fin portion 21b in the vertical direction is about 15 mm. The pitch of the fin portions 21b is about 1.5 mm, and the lateral thickness of the fin portions 21b is about 1.5 mm.

  FIG. 3 is a cross-sectional view for explaining the outline of the cold spray method. The cold spray device 60A includes a mixer (hopper) 67 that mixes two kinds of materials (particles) introduced from two raw material supply pipes 68A and 68B, a heater 62 that heats compressed air, and a gun for spraying the particles. 63 and pipes 64 and 65 for supplying compressed air. A substrate is installed at a position about 5 to 30 mm away from the gun 63. Instead of compressed air, compressed gas such as helium or nitrogen may be used.

The first material (Cu) and the second material (Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ , AlN, W, Mo are respectively supplied to the mixer 67 from two raw material supply pipes 68A and 68B. And Fe ₃₂ Ni ₅ Co (invar alloy), etc.) are introduced into the mixer 67 and then sent to the gun 63 by compressed air fed from the pipe 64. It is done. On the other hand, the compressed air sent from the pipe 65 is heated to 300 to 500 ° C. by the heater 62 and sent to the gun 63. Then, in a state where the heated compressed air and each particle group are mixed with each other by the gun 63, the jet is injected in a supersonic flow. Each particle collides with the substrate at a high speed of 500 m / s or more, the particle is plastically deformed by the kinetic energy of the particle, and is joined in an entangled state to form the underlying conductive member 28. The gun 63 is repeatedly swept along the substrate. The diameter of each particle is 0.1 μm to 50 μm, preferably 10 μm to 50 μm.
As a substrate for depositing the underlying conductive member 28, a Cu plate that becomes the metal wiring 23 is used, and after that, the underlying conductive member 28 is patterned together with the Cu plate, and then the heat sink 21 is bonded to the heat sink 21 by an adhesive that becomes the insulating resin layer 26. The underlying conductive member 28 and the metal wiring 23 are formed by pasting. In the structure shown in FIG. 1, in the underlying conductive member 28, the region where the solder layer is not required is deleted by selective etching or the like, but the underlying conductive member 28 is left as it is. May be. Further, the member 28 may be formed on the Cu plate by a base track using a metal mask, and the etching process may be omitted.

Alternatively, the metal wiring 23 may be formed in advance on the heat sink 21 via the insulating resin layer 26, and the underlying conductive member 28 may be formed on the metal wiring 23 by direct thermal spraying.
In addition, the metal wiring 23 is previously formed on the heat sink 21 via the insulating resin layer 26, while the underlying conductive member 28 is formed on a suitable substrate by a thermal spraying method, and then the underlying conductive member 28 is peeled off from the substrate. Thus, the metal wiring 23 may be joined using solder or brazing material.

  According to the present embodiment, the thermal expansion coefficient of the underlying conductive member 28 including the first material (Cu) and the second material is the thermal expansion coefficient between the metal wiring 23 made of the first material and the semiconductor chip 11. Becomes an intermediate value. Therefore, the occurrence of cracks in the solder layer 14 can be suppressed by the thermal stress caused by the difference in thermal expansion coefficient between the semiconductor chip 11 and the metal wiring 23. And the reliability of the junction part between members (between the metal wiring 23 and the underlying conductive member 28 and between the underlying conductive member 28 and the semiconductor chip 11) can be maintained high.

In particular, by using the cold spray method in the step of forming the underlying conductive member 28, the underlying conductive member can be formed at a relatively low temperature. In the cold spray method, although compressed air heated to 300 to 400 ° C. by the heater 62 is used, it is rapidly cooled by the expansion of air, so that when it collides with the heat sink 21, the temperature becomes a low temperature of room temperature to 100 ° C. Because. Therefore, it is possible to suppress warping caused by the difference in thermal expansion coefficient between the metal wiring 23 and the underlying conductive member 28 after processing. A film formed using a thermal spraying method such as the cold spray method has been confirmed to be dense. In particular, the cold spray method has a high film deposition efficiency and a low manufacturing cost.
Further, when a plurality of materials are combined, a difference in specific gravity, a difference in melting point, or the like becomes an obstacle, and in most cases, the range that can be combined is limited. On the other hand, as in this embodiment, by using the thermal spraying method, the underlying conductive member 28 including the first material and the second material can be easily formed in an almost arbitrary composition range.

  In the present embodiment, when the cold spray shown in FIG. 3 is performed, the supply of the second material from the raw material supply pipe 68B is small during the first sweep, and the lower end portion of the underlying conductive member 28 The composition ratio of the second material is about 20 Vol%. Then, as the number of sweeps proceeds, such as the second time, the third time,..., The ratio of the second material supplied from the raw material supply pipe 68B increases, and the second material from the raw material supply pipe 68A at the time of the final sweep. The composition ratio of the second material at the upper end portion of the underlying conductive member 28 is set to about 60 Vol%.

  By such a thermal spraying method, the composition distribution of the underlying conductive member 28 is such that the composition ratio of the first material increases as it is closer to the metal wiring 23 and the composition ratio of the second material increases as it is closer to the semiconductor chip 11 that is the upper member. Realize. Thus, the underlying conductive member 28 has a composition distribution in which the composition ratio of the first material is larger as it is closer to the metal wiring 23 and the composition ratio of the second material is larger as it is closer to the semiconductor chip 11 that is the upper member. As a result, both the thermal expansion coefficient difference at the interface between the underlying conductive member 28 and the metal wiring 23 and the thermal expansion coefficient difference between the underlying conductive member 28 and the semiconductor chip 11 can be reduced. The thermal stress applied to 14 can be reduced, and the occurrence of cracks in the solder layer 14 can be reliably suppressed. Moreover, the reliability of joining between the members from the metal wiring 23 to the semiconductor chip 11 can be improved.

  In the present embodiment, the average composition ratio of the second material in the underlying conductive member 28 is 20 to 70%. In the case of addition of 80% or more, the network between the Cu powders becomes weak, the bonding strength is lowered, and the strength of the underlying conductive member 28 may not be ensured. In order to ensure electrical continuity, the local maximum composition ratio of the second material is preferably 70% or less. In the first sweep, the composition ratio of the second material at the lower end portion of the underlying conductive member 28 may be 0% without supplying the second material from the raw material supply pipe 68B. . However, it is preferable that the average composition ratio of the second material in the entire underlying conductive member 28 falls within a range of 20 to 70%.

  It should be noted that the composition distribution in the underlying conductive member 28 does not necessarily have to be as in the present embodiment. For example, even if the composition ratio of Cu and the second material is a uniform composition of 1: 1, if the thermal expansion coefficient of the second material is smaller than the thermal expansion coefficient (17 ppm / K) of Cu, The heat caused by the difference between the thermal expansion coefficient and the thermal expansion coefficient applied to the solder layer 14 is a value between the thermal expansion coefficient and the thermal expansion coefficient (3 to 6 ppm / K) of each material constituting the semiconductor chip 11 such as Si and SiC. Stress can be relaxed.

The first material is Cu or Cu alloy, the second material is Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (Invar alloy), etc. As a result, the following remarkable effects can be exhibited.

FIG. 7 shows the amount of addition (Vol%) when a second material (Al ₂ O ₃ , SiC, SiO ₂ , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (Invar alloy)) is added to Cu. It is a graph which shows the change of a thermal expansion coefficient. As shown in FIG. 7, the thermal expansion coefficient of the underlying conductive member 28 decreases as the amount of the second material added increases. When the amount of the second material added is 20% or more, the thermal expansion coefficient of the underlying conductive member 28 is 15 ppm / K or less.

FIG. 8 shows the addition amount (Vol%) when the second material (Al ₂ O ₃ , SiC, SiO ₂ , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (Invar alloy)) is added to Cu. It is a graph which shows the change of thermal conductivity. As shown in FIG. 8, the thermal conductivity decreases as the addition amount of the second material increases. However, if the addition amount of the second material is 70% or less, the thermal conductivity is 100 W / m · K. A sufficiently large value can be obtained as described above.
FIG. 9 is a table showing various characteristics of the first and second materials.

  In particular, when the thermal expansion coefficient of the underlying conductive member 28 is 10 ppm / K or less, it is preferable in that the difference in thermal expansion coefficient from the semiconductor chip 11 can be further reduced.

  On the other hand, by configuring the metal wiring 23 (upper member) with Cu, Cu alloy, Al, or Al alloy, the electrical resistance and the thermal conductivity can be particularly reduced, so that the conductive function and the heat dissipation function as the wiring member are particularly high. Become. Therefore, according to this embodiment, the overall performance of the power module 10 can be particularly improved, and the reliability of bonding between members can be maintained high by reducing the thermal stress. However, the constituent material of the metal wiring 23 of the present invention is not necessarily limited to Cu, Cu alloy, Al, or Al alloy.

  The underlying conductive member 28 only needs to include a region located directly below the semiconductor chip 11, and need not be widely formed on the metal wiring 23.

  The power module 10 according to the present embodiment includes the solder layer 14 made of the above-described Pb-free solder. In general, Pb-free solder includes the following. For example, Sn (liquid phase point 232 ° C.), Sn-3.5% Ag (liquid phase point 221 ° C.), Sn-3.0% Ag (liquid phase point 222 ° C.), Sn-3.5% Ag−0.55% Cu (liquid phase point) 220 ° C.), Sn-3.0% Ag-0.5% Cu (liquid phase point 220 ° C.), Sn-1.5% Ag-0.85% Cu-2.0 Bi (liquid phase point 223 ° C.), Sn-2.5% Ag-0.5% Cu -1.0Bi (liquid phase point 219 ° C), Sn-5.8Bi (liquid phase point 138 ° C), Sn-0.55% Cu (liquid phase point 226 ° C), Sn-0.55% Cu-others (liquid phase point 226 ° C) , Sn-0.55% Cu-0.3% Ag (liquid phase point 226 ° C), Sn-5.0% Cu (liquid phase point 358 ° C), Sn-3.0% Cu-0.3% Ag (liquid phase point 312 ° C), Sn- 3.5% Ag-0.5% Bi-3.0In (liquid phase point 216 ° C), Sn-3.5% Ag-0.5% Bi-4.0In (liquid phase point 211 ° C), Sn-3.5% Ag-0.5% Bi-8.0In (Liquid phase point 208 ° C), Sn-8.0% Zn 3.0% Bi (liquidus point 197 ° C.), and the like. In this embodiment, a low-melting point Pb-free solder having a liquidus point of 250 ° C. or lower, for example, Sn-3.0% Ag-0.5% Cu (liquidus point 220 ° C.) is used. It is not a thing.

  In the present embodiment, an epoxy resin containing a metal or ceramic filler is used for the insulating resin layer 26. Although the usable temperature of the epoxy resin varies depending on the type, it is easy to select a temperature exceeding 250 ° C. In this embodiment, a temperature higher than the liquid phase point of Pb-free solder is used. Therefore, it becomes possible to perform a Pb-free solder reflow process after the insulating resin layer 26 is formed in the power module assembly process described later. For example, an epoxy resin filled with alumina, silica, aluminum, aluminum nitride, or the like can be used, and the thermal conductivity is preferably 1.0 (W / m · K) or more, and 5.0 ( W / m · K) or more is more preferable.

  The thickness of the insulating resin layer 26 is preferably 0.4 mm or less, and more preferably 0.2 mm or less. The thermal resistance of the insulating resin layer 26 is determined depending on the thermal conductivity and thickness, but the thermal resistance decreases as the thickness decreases. Therefore, when the thickness is 0.4 mm or less, the heat dissipation function is enhanced.

  In the present embodiment, since one solder layer 14 and an insulating resin layer 26 made of a resin adhesive are used, as in the case of providing two solder layers, a low-melting point Pb is provided according to the process before and after the process. There is no need to use free solder and high-melting point Pb-free solder, and only low-melting point Pb-free solder is required. Currently, Pb-free solder having a relatively high Cu composition ratio (for example, Sn-5.0% Cu, Sn-3.0% Cu-0.3% Ag having a lamination point of 300 ° C. or higher) has been developed as Pb-free solder. It is difficult to obtain high melting point Pb-free solder having reliable connection reliability due to many problems such as erosion problems and oxide problems. On the other hand, as the low melting point Pb-free solder, for example, a solder having high connection reliability such as Sn-3.0% Ag-0.5% Cu (JEITA recommended alloy) having a liquidus point of 220 ° C. has been obtained. As the resin adhesive, an epoxy resin having a usable temperature exceeding 250 ° C. can easily be obtained that can withstand a higher temperature than the liquid phase point of the low melting point Pb-free solder. Therefore, according to the present embodiment, the solder layer 14 can be made Pb-free and Pb-free can be achieved while ensuring connection reliability.

  That is, when two solder layers are used, high melting point solder (Sn-90% Pb) having a liquidus point of 300 ° C. to 330 ° C. is used for the solder layer to be soldered first, and solder to be soldered later. For the layer, low melting point solder (Sn-50% Pb) having a liquidus point of about 216 ° C. is used. That is, high melting point solder is used in the previous soldering process, and low melting point solder is used in the subsequent soldering process so that the solder layer formed in the previous process does not melt in the reflow furnace.

  On the other hand, it is being obliged to use so-called Pb-free (lead-free) parts that do not use Pb (lead) as various products due to environmental problems. For example, low melting point solder (Sn-50% Pb) is used as (Sn). It is possible to replace with low melting point Pb-free solder such as -3.0% Ag-0.5% Cu), but it is possible to replace with conventional high melting point solder (Sn-90% Pb). It is difficult to use high melting point Pb-free solder.

  On the other hand, as in this embodiment, the insulating resin layer 26 is used for the connection between the underlying conductive member 28 and the metal wiring 23 (wiring member), so that the solder layer is used only for joining the semiconductor chip 11 and the metal wiring 23. 14 can be used. Therefore, the solder layer 14 can be made Pb-free while using Pb-free solder having a low melting point while ensuring connection reliability.

-Examples of other thermal spraying methods-
FIG. 4 is a cross-sectional view for explaining the outline of the HVAF (High Velocity Aero Fuel) method. The HVAF apparatus 60B sprays particles by a mixer (hopper) 67 that mixes two kinds of materials (particles) introduced from two raw material supply pipes 68A and 68B, a heater 62 that heats compressed air and combustible gas, and particles. For this purpose, a pipe 64 and 65 for supplying compressed air, and a gas pipe 66 for supplying a combustible gas (such as propane gas). A substrate is installed at a position about 5 to 30 mm away from the gun 63.

The first material (Cu) and the second material (Al ₂ O ₃ , SiC, SiO ₂ , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (from the two raw material supply pipes 68A and 68B) are supplied to the mixer 67, respectively. When each particle group (particle size 10 to 40 μm) of Invar alloy)) is charged, it is mixed in the mixer 67 and then sent to the gun 63 by compressed air fed from the pipe 64. On the other hand, the compressed air and combustible gas sent from the pipe 65 and the gas pipe 66 are accelerated by the ignition plug 69 and sent to the gun 63. Then, in a state where the combustion gas, compressed air, and each particle group are mixed with each other by the gun 63, the gun 63 and the flame are injected in supersonic flow. Each particle collided with the substrate at approximately the same temperature (300 to 500 ° C.) and higher speed (600 to 800 m / s) as in the cold spray method, and the particles were entangled by plastic deformation due to the kinetic energy of the particles. The underlying conductive member 28 is formed by being joined in the state. The particle size of the particles is 10 to 40 μm.

  Further, when the HVOF (High Velocity Oxigen Fuel) method is used, an apparatus as shown in FIG. 4 is used except that oxygen is supplied from the supply pipes 64 and 65. In that case, a frame speed of 2000 m / s or more and a particle speed of 750 m / s are achieved.

FIG. 5 is a sectional view for explaining the outline of the AD (Aerosol Deposition) method. A work holder 72, a substrate 72, a metal mask 73, and a nozzle 76 are disposed in a film forming chamber 71 provided with a vacuum pump VP. The aerosol generation chamber 78 is supplied with a particle group of the first material (Cu) from the raw material supply pipe 79A and from the raw material supply pipe 79B to the second material (Al ₂ O ₃ , SiC, SiO ₂ , AlN, A group of particles of W, Mo, Fe ₃₂ Ni ₅ Co (Invar alloy) is supplied, and each particle is mixed in the aerosol chamber 78. Each particle rides on a gas flow supplied from a compressed gas cylinder such as air, He, Ar, nitrogen, etc., is carried from the connecting pipe 77 to the nozzle 76, and is ejected at a high speed. Then, an underlying conductive member 74 including the first material and the second material is deposited on the substrate 73. When the film formation is completed, the underlying conductive member 74 is peeled off from the substrate 73 and bonded to the metal wiring 23 to form the structure shown in FIG.

  In this method, as in the cold spray method, the film is formed at a low temperature of about room temperature. The particle speed is 200 to 400 m / s, and the particle diameter is 0.03 μm to 0.1 μm, so that finer particles can be used.

  Comparing the thicknesses of the composite material films to be formed, the thickness is several tens μm to several mm in the cold spray method, HVAF method, and HVOF method, but several μm to several tens μm in the AD method. In the power module of the present invention, it is important to have a thickness of about several tens of μm or more that can relieve stress, and it is preferable to use a cold spray method, an HVAF method, or an HVOF method.

(Modification)
FIG. 6 is a diagram for explaining a modification of the manufacturing method of the first embodiment. In the first embodiment, the first material particle group and the second material particle group are mixed, and then each particle is ejected from one nozzle. The particle group is sprayed. That is, as shown in FIG. 6, a particle group of the first material (Cu) is ejected from the nozzle A, and the second material (Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ is ejected from the nozzle B. , AlN, W, Mo, Fe ₃₂ Ni ₅ Co (invar alloy), etc.) are ejected to deposit an underlying conductive member containing the first material and the second material on the substrate. The nozzles A and B are nozzles used in the cold spray method, the HVAF method, the HVOF method, or the AD method.

(Other embodiments)
In each of the above embodiments, Al or an Al alloy is used as the material of the heat sink 21, but the material is not limited to this. For example, ceramics such as Cu, Cu alloy, AlN, SiN, BN, SiC, and WC, or composite materials such as Al—SiC, Cu—W, and Cu—Mo may be used.

  In the present embodiment, Cu is used as the material of the metal wiring 23, but is not limited to this. For example, a composite material such as Cu alloy, Al, Al alloy, Al—SiC, Cu—W, or Cu—Mo may be used.

  The semiconductor element disposed in the power module of the present invention may be a power device using a wide band gap semiconductor (SiC, GaN, etc.) or a power device using Si.

  In the above embodiment, the IGBT is formed on the semiconductor chip 11, but a semiconductor chip on which a MOSFET, a diode, a JFET, or the like is formed may be used.

  In each of the above embodiments, a structure in which a large number of power modules 10 are attached to the top plate 50a is adopted. However, a large number of semiconductor chips may be mounted on a single heat sink member 24 that also serves as the top plate.

  The heat exchange medium for exchanging heat with the heat sink member 24 is preferably a liquid such as fluorinate or water in consideration of cooling ability and cost. However, it may be a gas such as helium, argon, nitrogen or air.

  In each of the above embodiments, the insulating resin layer 26 is made of an epoxy resin that is a thermosetting resin, but may be made of a thermoplastic resin such as PPS.

  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.

  The power module of the present invention can be used for various devices equipped with MOSFET, IGBT, diode, JFET and the like.

It is sectional drawing of the power module which concerns on embodiment. It is sectional drawing of the power module set which concerns on embodiment. It is sectional drawing explaining the outline of the cold spray method. It is sectional drawing explaining the outline of HVAF method (HVOF method). It is sectional drawing explaining the outline of AD method. It is a figure which shows the modification of embodiment. It is a graph which shows the change of the thermal expansion coefficient with respect to addition amount (Vol%) when the 2nd material is added to Cu. It is a graph which shows the change of the heat conductivity with respect to the addition amount (Vol%) when the 2nd material is added to Cu. It is a figure which shows the various characteristics of a 1st and 2nd material in a table | surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power module 11 Semiconductor chip 12 Upper surface electrode 13 Back surface electrode 14 Solder layer 17 Signal wiring 18 High power wiring 21 Heat sink 21a Flat plate part 21b Fin part 23 Metal wiring 25 O-ring 26 Insulating resin layer 28 Underlay conductive member 40 Gel layer 50a Top Plate 50b Container 51 Space 53 Module resin frame 56 Electrode terminal layer

Claims (7)

A semiconductor chip;
A wiring member electrically connected to a part of the semiconductor chip and containing as a main component a first material selected from Al, Al alloy, Cu, and Cu alloy;
An underlay conductive member interposed between the wiring member and the semiconductor chip, at least in a region located directly below the semiconductor chip;
A solder layer interposed between the underlying conductive member and the semiconductor chip;
The underlay conductive member includes the first material and a second material having a smaller coefficient of thermal expansion than the first material. The power module according to claim 1,
The power module, wherein the composition ratio of the second material in the underlying conductive member is 20 to 70%. The power module according to claim 1 or 2,
The power module, wherein the composition ratio of the first material in the underlying conductive member is larger as it is closer to the wiring member, and is larger as the composition ratio of the second material is closer to the solder layer. In the power module according to any one of claims 1 to 3,
A power module, wherein the underlying conductive member has a thermal expansion coefficient of 10 ppm / K or less. In the power module according to any one of claims 1 to 4,
The second material is at least one substance selected from Si, Al ₂ O ₃ , SiC, Si ₃ N ₄ , SiO ₂ , AlN, W, Mo, and Fe ₃₂ Ni ₅ Co (Invar alloy). , Power module. In the power module according to any one of claims 1 to 5,
The underlying conductive member is a power module formed by a thermal spraying method. In the power module according to any one of claims 1 to 6,
A heat sink provided below the wiring member;
An insulating resin layer connecting the wiring member and the heat sink;
A power module further comprising:

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