JP7487614B2 - Semiconductor device, manufacturing method thereof, and power conversion device - Google Patents

Description

This disclosure relates to a semiconductor device, a method for manufacturing a semiconductor device, and a power conversion device.

Conventional semiconductor devices are provided with a wiring board on which semiconductor elements are mounted and a heat dissipation member bonded to the wiring board, with Al (aluminum) being widely used as the material for the heat dissipation member. In order to solder the Al heat dissipation member to the conductor layer of the wiring board, surface treatment such as plating the Al surface with Cu (copper) that is solder wettable is required, but plating is difficult because a dense oxide film is likely to form on the Al surface. Therefore, there is a technology that uses a Cu-Al clad material in which an Al layer and a Cu layer are bonded together as a heat dissipation member (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 9-298259

However, in the semiconductor device described in Patent Document 1, the heat dissipation member is made of a bimetal made of Cu and Al bonded together, which have different thermal expansion coefficients, and this causes the problem of warping when heated.

This disclosure has been made to solve the above-mentioned problems, and aims to obtain a semiconductor device with reduced warping of the heat dissipation member.

The semiconductor device according to the present disclosure includes a heat dissipation member having a substrate portion made of Al or an Al alloy, a metal layer formed on the substrate portion of the heat dissipation member and made of Cu or a Cu alloy, or Ni or a Ni alloy, a first bonding material provided on the metal layer, a wiring board having a first conductor layer provided on the first bonding material and at least a surface layer on the metal layer side made of Cu or a Cu alloy, or Ni or a Ni alloy, an insulating layer provided on the first conductor layer, and a second conductor layer provided on the insulating layer, and a semiconductor element bonded to the second conductor layer of the wiring board via the second bonding material, and the thickness of the metal layer is 50% or less of the thickness of the substrate portion of the heat dissipation member.

The method for manufacturing a semiconductor device according to the present disclosure includes a first step of bonding a substrate portion of a heat dissipation member having a substrate portion formed of Al or an Al alloy to a metal layer formed of Cu or a Cu alloy, or Ni or a Ni alloy, a second step of bonding the side of the metal layer opposite to the substrate portion to a surface layer of a first conductor layer of a wiring board having an insulating layer, a first conductor layer provided on one side of the insulating layer and at least a surface layer opposite to the insulating layer side formed of Cu or a Cu alloy, or Ni or a Ni alloy, and a second conductor layer provided on the other side of the insulating layer, and a third step of bonding the second conductor layer of the wiring board to a semiconductor element, wherein the thickness of the metal layer is 50% or less of the thickness of the substrate portion of the heat dissipation member.

The semiconductor device according to the present disclosure has an advantage that the thickness of the metal layer is 50% or less of the thickness of the substrate portion of the heat dissipation member, thereby reducing warping of the heat dissipation member and improving reliability.

The method of manufacturing a semiconductor device according to the present disclosure has the advantage that the thickness of the metal layer is 50% or less of the thickness of the substrate portion of the heat dissipation member, thereby reducing warping of the heat dissipation member and making it possible to obtain a semiconductor device with improved reliability.

1 is a cross-sectional view showing a semiconductor device according to a first embodiment; 1 is a perspective view showing a configuration of a portion of a semiconductor device according to a first embodiment; 4 is a cross-sectional view for illustrating the first half of the process of the manufacturing method of the semiconductor device in the first embodiment. 4A to 4C are cross-sectional views for illustrating latter steps of the manufacturing method of the semiconductor device according to the first embodiment. 1 is a perspective view showing a partial configuration of a modified example of the semiconductor device of the first embodiment; 11 is a cross-sectional view for illustrating a modified example of the manufacturing method of the semiconductor device according to the first embodiment. FIG. 11 is a cross-sectional view showing a semiconductor device according to a second embodiment. FIG. 11 is a perspective view showing a configuration of a portion of a semiconductor device according to a second embodiment. 11 is a cross-sectional view for illustrating the first half of the process of the manufacturing method of the semiconductor device according to the second embodiment. 13A to 13C are cross-sectional views for illustrating latter steps of the manufacturing method of the semiconductor device according to the second embodiment. FIG. 11 is a perspective view showing a partial configuration of a first modified example of a semiconductor device according to a second embodiment. 13 is a cross-sectional view showing a configuration of a portion of a second modified example of the semiconductor device according to the second embodiment. FIG. FIG. 11 is a perspective view showing a configuration of a portion of a semiconductor device according to a third embodiment. 11 is a cross-sectional view for explaining a configuration of a semiconductor device according to a third embodiment. FIG. FIG. 11 is a cross-sectional view showing a semiconductor device according to a fourth embodiment. 13A to 13C are cross-sectional views for illustrating the first half of the process of the manufacturing method of the semiconductor device according 13A to 13C are cross-sectional views for illustrating the latter half of the process for manufacturing a semiconductor device according to the fourth embodiment. FIG. 13 is a cross-sectional view showing a semiconductor device according to a fifth embodiment. 13 is a cross-sectional view for illustrating the first half of the process of the manufacturing method of the semiconductor device according to the fifth embodiment. 13A to 13C are cross-sectional views for illustrating the latter half of the process for manufacturing a semiconductor device according to the fifth FIG. 13 is a block diagram for explaining a power conversion device according to a sixth embodiment.

The following describes an embodiment based on the drawings. Note that in the following drawings, the same or corresponding parts are given the same reference numerals, and their description will not be repeated. Also, the values of dimensions, temperatures, time, etc. described below are merely examples, and other values may be used. Furthermore, in the following description, terms that mean specific directions such as "upper" or "lower" may be used, but these terms are used for convenience and do not relate to the directions in actual implementation.

In addition, in this disclosure, the term "on" does not preclude the presence of an intervening element between components. For example, the description "B provided on A" includes both cases where another component C is provided between A and B and cases where it is not provided.

In addition, in this disclosure, each member may be described as being made of Al (aluminum), Cu (copper), or Ni (nickel), but "made of Al" means that it is made of Al or an Al alloy whose main component is Al, "made of Cu" means that it is made of Cu or a Cu alloy whose main component is Cu, and "made of Ni" means that it is made of Ni or a Ni alloy whose main component is Ni.

Embodiment 1.
A semiconductor device and a method for manufacturing the semiconductor device according to the first embodiment will be described with reference to FIGS.

First, the semiconductor device of the first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view showing a semiconductor device 100 of the first embodiment, and Figure 2 is a perspective view showing a portion of the configuration of the semiconductor device 100.

As shown in FIG. 1, the semiconductor device 100 includes a heat dissipation member 1 having a substrate portion 1a and pin fins 1b, copper foil 10 as a metal layer provided on the substrate portion 1a of the heat dissipation member 1, a wiring board 2 in which a first conductor layer 2b is bonded to the copper foil 10 via solder 11 as a first bonding material, a semiconductor element 4 bonded to a second conductor layer 2c of the wiring board 2 via solder 3 as a second bonding material, a case 6 bonded to the outer peripheral side of the wiring board 2 with adhesive 5, a main terminal 7a and a signal terminal 7b attached to the case 6, a wire 8a electrically connecting the main terminal 7a and the semiconductor element 4, a wire 8b electrically connecting the signal terminal 7b and the semiconductor element 4, and a sealing material 9 filled in the area surrounded by the heat dissipation member 1 and the case 6.

Here, the copper foil 10 is made of Cu and is bonded to the upper surface of the substrate portion 1a of the heat dissipation member 1 made of Al by silver oxide (not shown in FIG. 1). The first conductor layer 2b and the second conductor layer 2c of the wiring board 2 are also made of Cu. The copper foil 10 and the first conductor layer 2b made of Cu are bonded by solder 11 as a first bonding material. In other words, the solder 11 is provided on the copper foil 10, and the first conductor layer 2b of the wiring board 2 is provided on the solder 11.

As shown in Figures 1 and 2, the heat dissipation member 1 has a substrate portion 1a and multiple pin fins 1b. The substrate portion 1a is, for example, a flat plate with external dimensions of 85 mm x 70 mm x 4 mm thickness, and 256 (16 x 16) rectangular column-shaped pin fins 1b with side widths of 2 mm and heights of 8 mm are provided on the underside of the substrate portion 1a. The heat dissipation member 1 is made of Al, and the substrate portion 1a and pin fins 1b are formed integrally, for example, by forging. Copper foil 10 is joined to the upper surface of the substrate portion 1a of the heat dissipation member 1 by silver oxide.

The heat dissipation member 1 is not particularly limited as long as it is made of Al or an Al alloy mainly composed of Al, but it is preferable to make it of an Al alloy such as JIS A6063 or JIS A6061, since it is possible to increase the strength without substantially impairing the thermal conductivity. The heat dissipation member may have at least a flat substrate portion, and may have fins other than pin fins, or may not have fins, such as a heat dissipation member consisting only of a flat substrate portion. The thickness of the substrate portion 1a of the heat dissipation member 1 is not particularly limited, but may be, for example, 0.5 mm to 10 mm.

The copper foil 10 is a metal layer made of Cu, and has external dimensions of, for example, 61 mm x 61 mm x 0.2 mm thickness before soldering. Here, it is considered that the copper foil 10 after soldering is diffused and dissolved by the solder 11 that melts during soldering with the first conductor layer 2b of the wiring board 2, and becomes thinner. The diffusion and dissolution rate of Cu is about 0.02 μm/s, and even if the melting time of the solder 11 in the reflow furnace is estimated to be 600 s, the melted thickness is 12 μm. Therefore, it can be said that the copper foil 10 has sufficient heat resistance against soldering by having a thickness of 0.2 mm before soldering.

The thickness of the copper foil 10 before soldering is not limited to 0.2 mm, and a copper foil of any desired thickness can be used as the metal layer material, but it is preferable that the thickness is 20 μm or more so that it can be produced as a single foil and to prevent it from diffusing and dissolving in the solder and disappearing during soldering as described above. In this way, it is possible to prevent the copper foil 10 from diffusing and dissolving in the solder during soldering, exposing the substrate portion 1a of the Al heat dissipation member 1, and causing poor bonding due to lack of solder wetting.

Furthermore, as described above, if the thickness of the copper foil 10 before soldering is 0.2 mm, the thickness of the copper foil 10 after soldering will be 0.2 mm or less when considering diffusion and dissolution, and will have a thickness of 5% or less of the 4 mm thickness of the substrate portion 1a. As such, the thickness of the substrate portion 1a of the heat dissipation member 1 and the copper foil 10 as a metal layer differ greatly, and there is a large difference in rigidity between the substrate portion 1a and the copper foil 10, so warping due to being a bimetal can be suppressed.

In this embodiment, the copper foil 10 as the metal layer after soldering has a thickness of 5% or less of the substrate portion 1a of the heat dissipation member 1, but this is not limited thereto. If the thickness of the metal layer after soldering is 50% or less of the thickness of the substrate portion of the heat dissipation member 1, it is effective in reducing warping due to the difference in rigidity between the Al heat dissipation member 1 and the Cu copper foil 10. However, in order to further suppress warping, it is preferable that the thickness of the metal layer is 20% or less of the thickness of the substrate portion of the heat dissipation member, and more preferably 10% or less.

Taking the above into consideration, the preferred thickness of the metal layer after soldering is 0.1 mm to 3 mm, but is not limited to this. The copper foil 10 is not particularly limited as long as it is made of Cu or a Cu alloy, but it is preferable to use one with high thermal conductivity, such as JIS C1020 or JIS C1100.

As shown in FIG. 1, the wiring board 2 has a ceramic substrate 2a made of AlN (aluminum nitride) as an insulating layer, a first conductor layer 2b made of Cu provided on the lower surface, which is one surface of the ceramic substrate 2a, and a second conductor layer 2c made of Cu provided on the upper surface, which is the other surface of the ceramic substrate 2a. That is, the ceramic substrate 2a is provided as an insulating layer on the first conductor layer 2b, and the second conductor layer 2c is provided on the ceramic substrate 2a. In the wiring board 2, the outer dimensions of the ceramic substrate 2a are, for example, 65 mm x 65 mm x 0.64 mm thick, and the outer dimensions of the first conductor layer 2b and the second conductor layer 2c are, for example, 61 mm x 61 mm x 0.4 mm thick. The first conductor layer 2b of the wiring board 2 is provided on the solder 11 and is joined to the copper foil 10 via the solder 11. In addition, the second conductor layer 2c is composed of a conductor pattern divided into six parts, as shown in FIG. 2.

In addition, the wiring board 2 of the present embodiment has _a ceramic base material 2a made of AlN as an insulating layer, but is not limited to this, and by using a ceramic base material made of _Si3N4 (silicon nitride), it is possible to increase the flexural strength and suppress cracking. Also, by using a _ceramic base material made of _Al2O3 (alumina), it is possible to increase the thermal expansion coefficient, reduce thermal stress, and improve reliability.

As shown in Figs. 1 and 2, a plurality of semiconductor elements 4 are bonded via solder 3 on the second conductor layer 2c of the wiring board 2. The semiconductor elements 4 provided on each divided conductor pattern of the second conductor layer 2c are, for example, a Si (silicon) diode with external dimensions of 15 mm x 12 mm x 0.2 mm, and a Si IGBT (Insulated Gate Bipolar Transistor) with external dimensions of 15 mm x 12 mm x 0.2 mm. In other words, two semiconductor elements 4 are mounted on each of the six conductor patterns constituting the second conductor layer 2c, and 12 semiconductor elements 4 are provided in the entire semiconductor device 100.

In the present embodiment, a case will be described in which a diode and an IGBT made of Si are provided as the semiconductor element 4, but this is not limited thereto, and for example, a semiconductor element such as an IC (integrated circuit) or a MOSFET (metal-oxide-semiconductor field-effect transistor) may be provided. Furthermore, the semiconductor element is not limited to being made of Si, and may be made of, for example, SiC (silicon carbide) or GaN (gallium nitride).

In addition, in this embodiment, a semiconductor device 100 having a 6-in-1 module configuration in which six pairs of IGBTs and diodes are provided will be described, but the present invention is not limited to this, and may be a discrete component having one semiconductor element, a 1-in-1 module having one pair of semiconductor elements, or a 2-in-1 module having two pairs of semiconductor elements, etc.

As the material for the solder 11 as the first bonding material and the solder 3 as the second bonding material, for example, solder manufactured by Senju Metal Co., Ltd. (model number: M705) having a composition ratio of 96.5 wt% Sn-3.0 wt% Ag-0.5 wt% Cu and a melting point of 219°C can be used. Furthermore, the outer dimensions of the solder 11 before bonding are, for example, 19 mm x 14 mm x 0.3 mm thick, and the outer dimensions of the solder 3 before bonding are, for example, 15 mm x 12 mm x 0.1 mm thick.

The composition ratio of the solders 3 and 11 is not limited to 96.5 wt% Sn-3.0 wt% Ag-0.5 wt% Cu, and a solder material with a composition ratio of, for example, 98.5 wt% Sn-1 wt% Ag-0.5 wt% Cu or 96 wt% Sn-3 wt% Sb-1 wt% Ag may be used. Furthermore, instead of solder, the first and second bonding materials may be a highly heat-resistant Cu-Sn paste obtained by dispersing copper powder and isothermally solidifying it, or a nano-silver paste that is bonded by low-temperature firing of nano-silver particles.

The case 6 is made of PPS (Polyphenylene Sulfide) resin and has a frame shape with multiple sides that surround the outer periphery of the wiring board 2. It is adhered to the heat dissipation member 1, wiring board 2, copper foil 10, and solder 11 with a silicone adhesive 5. The outer dimensions of the case 6 are, for example, 85 mm x 85 mm x 15 mm high.

The case 6 is not limited to being made of PPS resin, and may be made of, for example, LCP (Liquid Crystal Polymer) resin. The case 6 is bonded to at least one of the heat dissipation member 1, the copper foil 10 as the metal layer, the solder 11 as the first bonding material, and the wiring board 2 by the adhesive 5, and may have a structure that does not leak out when the sealing material 9 is injected.

In addition, main terminals 7a and signal terminals 7b are attached to the case 6 by insert molding as external terminals. The main terminals 7a and signal terminals 7b are made of Cu and are Ni-plated, and each has a thickness of, for example, 1.0 mm.

The wires 8a and 8b are made of Al. The wire 8a electrically connecting the semiconductor element 4 and the main terminal 7a forms a main power circuit and has a diameter of, for example, 0.4 mm. On the other hand, the wire 8b connecting the semiconductor element 4 and the signal terminal 7b forms a signal circuit and has a diameter of, for example, 0.15 mm. Note that the wires 8a and 8b are not limited to being made of Al. For example, an Al ribbon bond or a Cu wire may be used for the wire 8a bonded to the main terminal 7a, and an Ag (silver) wire or an Au (gold) wire may be used for the wire 8b connected to the signal terminal 7b.

In FIG. 1, the electrical connections between each semiconductor element and wires are shown in a schematic manner, including wires that are actually present at the back of the page in FIG. 1. The wires are shown in the same manner in the other cross-sectional views described below.

The sealing material 9 is filled into the area surrounded by the heat dissipation member 1 and the case 6, and insulates and seals the semiconductor element 4 and the wires 8a and 8b. The sealing material 9 is formed, for example, from a thermosetting silicone gel. Note that the material of the sealing material 9 is not limited to silicone gel, and may be formed, for example, from an epoxy resin containing silica filler, etc.

Next, the method for manufacturing the semiconductor device of the first embodiment will be described with reference to Figures 3 and 4. Figure 3 is a cross-sectional view for explaining the first half of the process of the method for manufacturing the semiconductor device 100 of the present embodiment, and Figure 4 is a cross-sectional view for explaining the second half of the process of the method for manufacturing the semiconductor device 100.

First, as shown in FIG. 3(A), a silver oxide paste 10a is printed and applied to a thickness of 50 μm on the upper surface of the substrate portion 1a of the heat dissipation member 1 in the area where the copper foil 10 will be placed. The silver oxide paste is a paste in which silver oxide powder is dispersed in a reducing solvent. The copper foil 10 is then placed on the printed silver oxide paste 10a, and heated at 400° C. for 10 minutes in the atmosphere while applying a pressure of 1 MPa, thereby bonding the substrate portion 1a of the heat dissipation member 1 and the copper foil 10.

In order to suppress deformation of the pin fin 1b in the above-mentioned joining process, the pin fin may not be located in the center of the substrate, and pressure may be applied by clamping this center with a jig, or a thick pin fin may be provided in the center of the substrate, and pressure may be applied by clamping this thick pin fin with a jig. Also, deformation of the pin fin can be suppressed by forming a recess corresponding to the pin fin in the jig for applying pressure so that pressure is not applied directly to the pin fin.

In this way, after the copper foil 10 is bonded to the substrate portion 1a of the heat dissipation member 1 via silver oxide (not shown in FIG. 3(B) and subsequent figures), a plate-shaped solder 11 is placed on the copper foil 10, and the wiring board 2 is placed on the solder 11 so that the first conductor layer 2b side faces the solder 11. Furthermore, 12 plate-shaped solders 3 are placed on the second conductor layer 2c of the wiring board 2, and a semiconductor element 4 is placed on each solder 3. Then, the solders 3 and 11 are heated using a reflow furnace to melt the solders, thereby bonding the copper foil 10 to the first conductor layer 2b of the wiring board 2 via the solder 11, and bonding the second conductor layer 2c of the wiring board 2 to the semiconductor element 4 via the solder 3. In this way, as shown in FIG. 3(C), the copper foil 10 provided on the heat dissipation member 1 is soldered to the wiring board 2, and the wiring board 2 is soldered to the semiconductor element 4 at the same time.

Next, as shown in FIG. 4(A), the case 6 with the main terminals 7a and signal terminals 7b insert-molded is adhered to the heat dissipation member 1, copper foil 10, solder 11, and wiring board 2 using a silicone adhesive 5. At this time, it is heated at 140°C for 10 minutes, for example. Note that the adhesion should be such that the silicone gel injected into the inside of the case 6, which will be described later, does not leak out.

Then, as shown in FIG. 4(B), the main terminal 7a and the semiconductor element 4 are wired with wire 8a using a wire bonder to form a main power circuit. Also, the signal terminal 7b and the semiconductor element 4 are wired with wire 8b using a wire bonder to form a signal circuit.

Finally, as shown in FIG. 4(C), silicone gel is injected into the case 6, heated at 100°C for 1.5 hours, and then heated at 140°C for another 1.5 hours to harden it, forming the sealing material 9 for insulation and sealing, and the semiconductor device 100 is completed.

The effects of the semiconductor device 100 configured as above and the manufacturing method of the semiconductor device 100 will be described.

In semiconductor devices, Al, which has excellent heat dissipation properties and is lighter than Cu, is widely used as a material for heat dissipation components. Soldering is generally used as a method for joining heat dissipation components to wiring boards, but since the Al surface does not wet with solder, in order to solder join the wiring board to an Al heat dissipation component, surface treatment such as plating the surface of the substrate part of the heat dissipation component with Cu or Ni, which are solder wettable, is required. However, plating the Al surface is difficult because an oxide film is easily generated on the surface and is dense, which poses a problem.

It is therefore conceivable to provide a solder-wettable metal layer, such as made of Cu, on the heat dissipation component. However, if the thickness of the substrate part of the heat dissipation component and the metal layer are approximately the same, the thermal expansion coefficient of Al for the heat dissipation component and the metal layer made of Cu is 21 ppm/K while that of Cu is 17 ppm/K. As a result, due to the difference in thermal expansion coefficients, warping occurs when heated during soldering, etc., and there is a concern that the wiring board may crack when returned to room temperature or that reliability such as temperature cycle resistance may be poor.

In the semiconductor device 100 of this embodiment, the copper foil 10 is provided on the upper surface of the substrate portion 1a of the heat dissipation member 1, so that it is possible to perform solder bonding to the wiring board 2 without the need for surface treatment such as plating. In addition, since the copper foil 10 made of Cu is sufficiently thin, at 5% or less, compared to the substrate portion 1a of the heat dissipation member 1 made of Al, warping due to heating can be suppressed due to the difference in rigidity, and reliability can be improved. As described above in the explanation of the copper foil 10, if the Cu metal layer is 50% or less thick than the substrate portion of the heat dissipation member made of Al, it is effective in reducing warping due to the difference in rigidity, and a thickness of 20% or less is more preferable, and a thickness of 10% or less is even more preferable.

In addition, in order to plate the substrate of the heat dissipation member with Cu or Ni, etc., it is necessary to remove the oxide film on the Al surface as a pretreatment, but the oxide film formed on the Al surface is stable and requires the use of strong acid or strong alkali, which makes management and processing complicated. On the other hand, brazing or the like is usually used to bond and attach copper foil to the substrate of the heat dissipation member, but brazing requires heating at 600°C in a nitrogen atmosphere, which limits the conditions. Therefore, in the manufacturing method of the semiconductor device 100 of this embodiment, the substrate 1a of the heat dissipation member 1 and the copper foil 10 are bonded using silver oxide paste 10a, so that it is possible to directly bond the substrate 1a of the Al heat dissipation member 1 having an oxide film on its surface, and it is also possible to bond by heating at 400°C in the atmosphere.

Furthermore, the silver oxide contained in the silver oxide paste 10a described in this embodiment is an aggregate of powdered silver, and is therefore easily deformed. This results in less distortion than when materials with different thermal expansion coefficients are directly joined by solid-phase diffusion bonding or the like, and has the effect of reducing warping. In addition, silver oxide has heat resistance to heating during soldering between the wiring board 2 and the copper foil 10 as the metal layer, and therefore has the effect of providing high joint reliability.

In this embodiment, the case where the copper foil 10 as the metal layer is made of Cu has been described, but by using nickel foil made of Ni (diffusion rate is about 0.005 μm/s) instead of the copper foil 10 as the metal layer, which can be soldered and has a slower rate of diffusion and dissolution in solder than Cu, the heat resistance during soldering is improved. Also, in this embodiment, the copper foil 10 as the metal layer is called "copper foil" because it is 0.2 mm or less, but it does not necessarily have to be thin enough to be called "metal foil" like "copper foil" or "nickel foil", and it is effective as long as it has a thickness of 50% or less compared to the thickness of the substrate portion 1a of the heat dissipation member 1.

In addition, in this embodiment, the case where silver oxide is used to bond the substrate portion 1a of the heat dissipation member 1 to the copper foil 10 has been described, but this is not limited to this, and bonding can also be done using an aluminum silicon-based brazing material (bonding temperature 600°C) or a zinc aluminum brazing material (bonding temperature 400°C). Furthermore, bonding using a eutectic reaction between copper and aluminum (bonding temperature 540°C or higher) or solid-phase diffusion bonding (heating at 320°C for 30 minutes while applying pressure) can be used to achieve bonding with excellent thermal conductivity that does not leave any bonding material as a separate member at the interface.

In addition, in the wiring board 2 of this embodiment, the first conductor layer 2b and the second conductor layer 2c are both made of Cu, that is, the first conductor layer 2b and the second conductor layer 2c are each a single-layer structure formed of Cu or a Cu alloy, but the first conductor layer and the second conductor layer may have a surface layer made of Cu or Ni that is joined by the solder 3, 11. More specifically, the first conductor layer and the second conductor layer may have a layer structure including an inner layer made of Al provided on the ceramic substrate side and a surface layer made of Cu or Ni laminated on the inner layer made of Al. Here, the surface layer of the first conductor layer is a layer formed on the side opposite the ceramic substrate 2a side as an insulating layer, on the side of the solder 11 as a first bonding material. Also, the surface layer of the second conductor layer is a layer formed on the side opposite the ceramic substrate 2a side as a second bonding material that bonds the semiconductor element 4. In other words, the first conductor layer and the second conductor layer of the wiring board may have at least a surface layer made of Cu or Ni, regardless of the layer structure.

As described above, it is desirable that the first conductor layer and the second conductor layer of the wiring board have a layer structure formed of the same material from the viewpoint of formability. In other words, if the first conductor layer 2b is made of Cu, it is desirable that the second conductor layer 2c is made of Cu. Also, if the first conductor layer has a layer structure including an Al inner layer and a Cu surface layer, it is desirable that the second conductor layer also has a layer structure including an Al inner layer and a Cu surface layer, and if the first conductor layer has a layer structure including an Al inner layer and a Ni surface layer, it is desirable that the second conductor layer also has a layer structure including an Al inner layer and a Ni surface layer.

It goes without saying that the above-mentioned variations in materials and joining methods can also be applied to the variations and other embodiments described below.

A modified example of the semiconductor device of the first embodiment will be described with reference to FIG. 5. FIG. 5 is a perspective view showing the configuration of a portion of a semiconductor device according to a modified example of the semiconductor device 100 of the present embodiment.

As shown in FIG. 5, the semiconductor device of this embodiment differs from semiconductor device 100 in that copper foil 13 is a punched metal having a plurality of holes formed therein. The rest of the configuration of the semiconductor device according to the modified example is similar to that of semiconductor device 100, so the following description will focus on the differences from semiconductor device 100.

The copper foil 13 is a punched metal having a plurality of holes penetrating in the thickness direction. Such copper foil 13 can be formed, for example, by press working. The copper foil 13 is bonded onto the substrate portion 1a of the heat dissipation member 1 using silver oxide paste, as in the semiconductor device 100 of this embodiment. Then, the first conductor layer 2b of the wiring board 2 is bonded onto the copper foil 13 via plate-shaped solder 11.

In the semiconductor device according to the modified example configured in this way, air can escape through multiple holes, which has the effect of preventing the formation of unbonded areas due to air being trapped.

In addition, since the substrate portion 1a of the aluminum heat dissipation member 1 is exposed through the holes in the copper foil 13, it is possible that the solder 11 for joining to the first conductor layer 2b of the wiring board 2 will not wet in parts and will be repelled. However, even if voids occur due to the lack of solder wettability, if the voids are small they will not cause problems with poor bonding or thermal resistance.

A modified example of the method for manufacturing the semiconductor device of the first embodiment will be described with reference to FIG. 6. FIG. 6 is a cross-sectional view for explaining a modified example of the method for manufacturing the semiconductor device 100 of the present embodiment.

The manufacturing method of the semiconductor device according to the modified example differs from the manufacturing method of the semiconductor device 100 in that the jig 90 has a protrusion 91 when applying pressure, as shown in FIG. 6. The other steps of the manufacturing method of the semiconductor device according to the modified example are the same as the manufacturing method of the semiconductor device 100, so the following description will focus on the differences from the manufacturing method of the semiconductor device 100.

The manufacturing method of the semiconductor device 100 includes a step of placing the copper foil 10 on the printed silver oxide paste 10a, and heating it while applying pressure to bond the substrate portion 1a of the heat dissipation member 1 to the copper foil 10, as described in FIG. 3(A). In this modified example, a jig 90 is used in this step, in which multiple protrusions 91 are formed on the copper foil 10 at the points where it contacts the copper foil 10. The protrusions 91 are, for example, 0.2 mm high and are provided at a pitch of 15 mm. The protrusions 91 of the jig 90 apply pressure to the copper foil 10 so that it is embedded in the substrate portion 1a of the heat dissipation member 1. The semiconductor device thus formed has periodic protrusions formed on the copper foil 10 as a metal layer, which is embedded in the substrate portion 1a of the heat dissipation member 1, as shown in FIG. 6.

As described above in the description of the first embodiment, by using the silver oxide paste 10a, it is possible to bond the Al heat dissipation member 1 to the copper foil 10 without removing the oxide film formed on the upper surface of the substrate portion 1a. However, by exposing the new surface, which is a pure metal surface without an oxide film, the bonding spreads from the exposed new surface as a starting point, and the bonding is accelerated. Therefore, in the manufacturing method of the semiconductor device according to the modified example, the points of high pressure that serve as the starting points of bonding are formed periodically at equal intervals by the protrusions 91, which has the effect of increasing the bonding strength.

Embodiment 2.
A semiconductor device and a method for manufacturing the semiconductor device according to the second embodiment will be described with reference to Fig. 7 to Fig. 10. Fig. 7 is a cross-sectional view showing a semiconductor device 200 according to the present embodiment, and Fig. 8 is a perspective view showing a configuration of a portion of the semiconductor device 200. Fig. 9 is a cross-sectional view for explaining the first half of the steps in the method for manufacturing the semiconductor device 200 according to the present embodiment, and Fig. 10 is a cross-sectional view for explaining the second half of the steps in the method for manufacturing the semiconductor device 200.

As shown in Figures 7 and 8, the semiconductor device 200 of this embodiment differs from the semiconductor device 100 of the first embodiment in that the copper foil 20 as the metal layer has slits 22 and is divided into multiple pieces. The rest of the configuration of the semiconductor device 200 is similar to that of the semiconductor device 100 of the first embodiment, so the following description will focus on the differences from the semiconductor device 100.

As shown in FIG. 7, the semiconductor device 200 is similar to the semiconductor device 100 of the first embodiment in that a copper foil 20 is provided as a metal layer on the substrate portion 1a of the heat dissipation member 1, and the copper foil 20 and the first conductor layer 2b of the wiring board 2 are joined via solder 21. As shown in FIGS. 7 and 8, the copper foil 20 is divided into multiple pieces by slits 22, and is provided in accordance with the arrangement of the semiconductor elements 4.

The divided copper foil 20 has external dimensions of, for example, 19 mm x 14 mm x 0.2 mm thickness before soldering, and is arranged so that the spacing between adjacent copper foils 20, i.e., the width of the slits 22, is 2 mm in the vertical direction and 1.25 mm in the depth direction as shown in FIG. 8. As shown in FIG. 8, the divided structure of the copper foil 20 as a metal layer provided in the semiconductor device 200 of this embodiment is a structure divided into 12 parts, so that it is 4 columns x 3 rows in a plan view. Here, the second conductor layer 2c of the wiring board 2 has a conductor pattern divided into 6 parts, and two semiconductor elements 4 are mounted on each conductor pattern. In other words, the copper foil 20 is divided and provided in accordance with the arrangement of the semiconductor elements 4.

In this way, by forming the copper foil 20 so that it is directly below each semiconductor element 4 and positioning the slits 22 directly below the locations where the semiconductor element 4 is not present, it is possible to suppress the inclusion of voids while suppressing a decrease in heat dissipation. Therefore, it is desirable that the copper foil 20 is formed in a shape that is the same size as the semiconductor element 4 or larger than the semiconductor element 4 in a plan view and can cover the entire semiconductor element 4.

Next, the manufacturing method of the semiconductor device 200 will be described with reference to Figures 9 and 10, focusing on the differences from the semiconductor device 100 of embodiment 1.

First, as shown in FIG. 9(A), silver oxide paste 20a is printed and applied to the upper surface of the substrate portion 1a of the heat dissipation member 1 in a thickness of 50 μm in each of the 12 areas where the divided copper foil 20 will be placed. Then, the copper foil 20 is placed on the printed silver oxide paste 20a, and heated at 400° C. for 10 minutes while applying a pressure of 1 MPa in the atmosphere, thereby bonding the substrate portion 1a of the heat dissipation member 1 and the copper foil 20.

Then, 12 pieces of plate-shaped solder 21 (outer dimensions 19 mm x 14 mm x thickness 0.3 mm) corresponding to the copper foil 20 are placed on the copper foil 20, and the wiring board 2 is placed so that the first conductor layer 2b faces the solder 21. Furthermore, 12 pieces of plate-shaped solder 3 are placed on the second conductor layer 2c of the wiring board 2, and the semiconductor element 4 is placed on each solder 3. Then, the solders 3 and 11 are heated using a reflow furnace to melt the solders, thereby bonding the copper foil 10 and the first conductor layer 2b of the wiring board 2 through the solder 11, and bonding the second conductor layer 2c of the wiring board 2 and the semiconductor element 4 through the solder 3. In this way, as shown in FIG. 9(C), the copper foil 20 provided on the heat dissipation member 1 is soldered to the wiring board 2, and the wiring board 2 is soldered to the semiconductor element 4 at the same time. Then, slits 22 are formed between the divided adjacent copper foils 20 and between the solders 21. In addition, the solder 21 may connect adjacent plate-shaped solder pieces when joined.

Next, as shown in FIG. 10(A), the case 6 with the main terminals 7a and signal terminals 7b insert-molded is adhered using a silicone adhesive 5, similar to the semiconductor device 100 of the first embodiment.

After that, as shown in FIG. 10(B), the main terminal 7a and the semiconductor element 4 are wired with wire 8a using a wire bonder to form a main power circuit. Also, the signal terminal 7b and the semiconductor element 4 are wired with wire 8b using a wire bonder to form a signal circuit.

Finally, as shown in FIG. 10(C), silicone gel is injected into the inside of the case 6 and heated to harden it, forming an insulating seal as the sealant 9. At this time, the silicone gel is injected while drawing a vacuum, so that the case can be filled without leaving any voids. In this way, the semiconductor device 200 is completed.

The semiconductor device 200 and the manufacturing method for the semiconductor device 200 configured in this manner have the same effects as the semiconductor device 100 and the manufacturing method for the semiconductor device 100 of the first embodiment, and in addition, because the copper foil 20 as the metal layer is divided, air can escape through the slits 22, and the effect of preventing air from being trapped in the joint and existing as a void is achieved.

A first modified example of the semiconductor device of the second embodiment will be described with reference to FIG. 11. FIG. 11 is a perspective view showing the configuration of a portion of a semiconductor device according to the first modified example of the semiconductor device 200 of the present embodiment.

The first modified example of the semiconductor device of this embodiment differs from semiconductor device 200 in that, as shown in FIG. 11, the copper foil 20 is divided to correspond to the conductor pattern of the second conductor layer 2c of the wiring board 2. The rest of the configuration of the semiconductor device according to the first modified example is similar to that of semiconductor device 200, so the following description will focus on the differences from semiconductor device 200.

As shown in FIG. 11, the copper foil 20 of the semiconductor device according to the first modified example is provided in accordance with the arrangement of the six-part conductor pattern in the second conductor layer 2c of the wiring board 2. Even when formed in this manner, it is desirable to form the copper foil 20 so that it is present directly below the semiconductor element 4, and to place the slits 22 directly below the location where the semiconductor element 4 is not present. By dividing the copper foil 20 into six parts, the number of parts is reduced compared to when a 12-part copper foil is used, improving productivity, and the area occupied by the slits 22 is reduced, improving thermal conductivity and improving heat dissipation.

The divided structure of the copper foil 20 as the metal layer described above is characterized in that in the semiconductor device 200, the divided structure corresponds to the arrangement of the semiconductor element 4, while in the first modified example, the divided structure corresponds to the conductor pattern of the second conductor layer 2c of the wiring board 2. Therefore, when applied to a semiconductor device with a different module configuration, the divided structure should correspond to the arrangement of the semiconductor element or the conductor pattern arrangement of the second conductor layer of the wiring board, and is not limited to the 12-division or 6-division structure described above.

A second modified example of the semiconductor device of the second embodiment will be described with reference to FIG. 12. FIG. 12 is a cross-sectional view showing the configuration of a portion of a semiconductor device according to the second modified example of the semiconductor device 200 of the present embodiment.

The second modified example of the semiconductor device of this embodiment differs from semiconductor device 200 in that, as shown in FIG. 12, a frame-shaped protrusion 1c is provided around the upper surface side of the substrate portion 1a of the heat dissipation member 1, i.e., the side on which the copper foil 20 as a metal layer is provided. The rest of the configuration of the semiconductor device according to the first modified example is the same as that of semiconductor device 200, so the following description will focus on the differences from semiconductor device 200.

As shown in FIG. 12, the heat dissipation member 1 has a substrate portion 1a, pin fins 1b provided on the underside of the substrate portion 1a, and a protruding portion 1c provided in a frame shape on the upper surface of the substrate portion 1a. The protruding portion 1c is formed to a thickness of, for example, 4 mm, and the substrate portion 1a is formed to a thickness of, for example, 2 mm. In other words, the protruding portion 1c and the substrate portion 1a have a combined thickness of 6 mm, and the central portion where the protruding portion 1c is not provided is a recessed portion with a depth of 4 mm. The recessed portion has, for example, external dimensions of 66 mm x 66 mm. In this way, the protruding portion 1c is provided surrounding the copper foil 20 as the metal layer.

Thinning the substrate portion 1a of the heat dissipation member 1 improves heat dissipation, but warping occurs during soldering, which increases the warping of the wiring substrate 2 and raises concerns about cracks. Therefore, by leaving a thick portion on the periphery of the heat dissipation member 1, rigidity is ensured, and the difference in rigidity with the copper foil 20 has the effect of further suppressing warping.

Embodiment 3.
A semiconductor device according to a third embodiment will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is a perspective view showing a configuration of a part of the semiconductor device according to the present embodiment, and Fig. 14 is a cross-sectional view for explaining the configuration of the semiconductor device according to the present embodiment.

As shown in FIG. 13, the semiconductor device of this embodiment differs from the semiconductor device 100 of the first embodiment in that a mesh 30 made of woven Cu thin wires is used as the metal layer instead of the copper foil 10. The rest of the configuration of the semiconductor device of this embodiment is similar to that of the semiconductor device 100 of the first embodiment, so the following description will focus on the differences from the semiconductor device 100.

The mesh 30 as a metal layer is formed by weaving fine Cu wires as shown in Figures 13 and 14. As shown in Figure 14(A), the mesh 30 has a thickness H1 due to the weaving of fine Cu wires before bonding, but as shown in Figure 14(B), it has a thickness H2 smaller than H1 after bonding due to pressure applied during bonding. Note that Figure 14(B) shows a case where the Al substrate portion 1a and the Cu mesh 30 are directly bonded by, for example, solid-phase diffusion bonding, and in this case, the mesh 30 is bonded so as to sink into the substrate portion 1a.

The mesh 30 can also be bonded using silver oxide paste 30a, as shown in FIG. 14(C). In this case, the mesh 30 is bonded so that it sinks into the silver oxide paste 30a, and may be partially in contact with the substrate portion 1a of the heat dissipation member 1. Even in this case, as in FIG. 14(B), the mesh 30 after bonding has a thickness H2 that is smaller than the thickness H1 before bonding.

In the semiconductor device and the method for manufacturing the semiconductor device of this embodiment configured in this way, in addition to the same effects as the semiconductor device 200 and the method for manufacturing the semiconductor device 200 of embodiment 2, by using the mesh 30, the contact area is smaller than that of a single foil, so the surface pressure increases, deforming the Al surface and breaking the oxide film, making it easier to plastically deform, thereby improving the bondability.

Embodiment 4.
A semiconductor device and a method for manufacturing the semiconductor device according to the fourth embodiment will be described with reference to Fig. 15 to Fig. 17. Fig. 15 is a cross-sectional view showing a semiconductor device 400 according to the present embodiment. Fig. 16 is a cross-sectional view for explaining the first half of the process of the method for manufacturing the semiconductor device 400 according to the present embodiment, and Fig. 17 is a cross-sectional view for explaining the latter half of the process of the method for manufacturing the semiconductor device 400.

As shown in FIG. 15, the semiconductor device 400 of this embodiment differs from the semiconductor device 200 of the second embodiment in that the main power circuit is formed by joining the semiconductor element 4 to the main terminals 41, 42 via solder 43. Since the other configurations of the semiconductor device 400 are similar to those of the semiconductor device 200 of the second embodiment, the following description will focus on the differences from the semiconductor device 200.

Similar to the semiconductor device 200 of the second embodiment, the semiconductor device 400 has copper foil 20 as a plurality of divided metal layers, and the copper foil 20 and the first conductor layer 2b of the wiring board 2 are joined via solder 21. The semiconductor device 400 does not use wires to form the main power circuit, but forms the main power circuit by soldering main terminals 41, 42 attached to the case 6 by insert molding onto the semiconductor element 4. In addition to being electrically joined to the main terminals 41, 42, the semiconductor element 4 is wire-joined to a signal terminal (not shown) that is insert-molded into the case 6.

Next, the manufacturing method of the semiconductor device 400 will be described with reference to Figures 16 and 17, focusing on the differences from the semiconductor device 200 of the second embodiment.

First, as shown in FIG. 16(A), similar to the semiconductor device 200 of the second embodiment, silver oxide paste 20a is printed on the upper surface of the substrate portion 1a of the heat dissipation member 1 in the range of 12 locations where the divided copper foil 20 will be placed. Then, the copper foil 20 is placed on the printed silver oxide paste 20a, and the substrate portion 1a of the heat dissipation member 1 and the copper foil 20 are joined by heating while applying pressure in the atmosphere.

After that, as shown in FIG. 16(B), the copper foil 10 and the first conductor layer 2b of the wiring board 2 are joined via solder 21, and the second conductor layer 2c of the wiring board 2 and the semiconductor element 4 are joined via solder 3. In this way, as shown in FIG. 16(C), the copper foil 20 provided on the heat dissipation member 1 is soldered to the wiring board 2, and the wiring board 2 is soldered to the semiconductor element 4 at the same time. As a result, slits 22 are formed between the divided adjacent copper foils 20 and between the solders 21.

Next, as shown in FIG. 17(A), the case 6 with the main terminals 41, 42 and signal terminals (not shown) insert-molded is adhered using a silicone adhesive 5. At this time, while adhering the case 6, plate-shaped solder 43 is sandwiched between the top surface of the semiconductor element 4 and the main terminals 41, 42. The main terminals 41, 42 and the semiconductor element 4 are then joined by melting the solder 43 to form a main power circuit. Furthermore, the signal terminals (not shown) and the semiconductor element 4 are wired with Al wires (not shown) using a wire bonder to form a signal circuit. In this way, the case 6 is joined and the circuit is formed as shown in FIG. 17(B).

Finally, as shown in FIG. 17(C), silicone gel is injected into the inside of the case 6 and heated to harden it, forming an insulating sealant 9. In this way, the semiconductor device 400 is completed.

The semiconductor device 400 and the manufacturing method for the semiconductor device 400 configured in this manner achieve the same effects as the semiconductor device 200 and the manufacturing method for the semiconductor device 200 of the second embodiment.

Embodiment 5.
A semiconductor device and a method for manufacturing the semiconductor device according to the fifth embodiment will be described with reference to Fig. 18 to Fig. 20. Fig. 18 is a cross-sectional view showing a semiconductor device 500 according to the present embodiment. Fig. 19 is a cross-sectional view for explaining the first half of the process of the method for manufacturing the semiconductor device 500 according to the present embodiment, and Fig. 20 is a cross-sectional view for explaining the latter half of the process of the method for manufacturing the semiconductor device 500.

As shown in FIG. 18, the semiconductor device 500 of this embodiment differs from the semiconductor device 200 of the second embodiment in that it does not have a case and has a transfer molded structure. The rest of the configuration of the semiconductor device 500 is similar to that of the semiconductor device 200 of the second embodiment, so the following description will focus on the differences from the semiconductor device 200.

Similar to the semiconductor device 200 of the second embodiment, the semiconductor device 500 has copper foil 20 as a plurality of divided metal layers, and the copper foil 20 and the first conductor layer 2b of the wiring board 2 are joined via solder 21. The semiconductor device 500 does not have a case, and has a structure in which the sealing material 51 is molded by transfer molding and insulated and sealed.

In addition, since the semiconductor device 500 does not have a case, the main terminals 7a and signal terminals 7b are fixed to the heat dissipation member 1, wiring board 2, copper foil 20, and solder 21 by means of a silicone adhesive 5. The main terminals 7a and signal terminals 7b are also part of the lead frame.

Next, the manufacturing method of the semiconductor device 500 will be described with reference to Figures 19 and 20, focusing on the differences from the semiconductor device 200 of the second embodiment.

First, as shown in FIG. 19(A), similar to the semiconductor device 200 of the second embodiment, silver oxide paste 20a is printed on the upper surface of the substrate portion 1a of the heat dissipation member 1 in the range of 12 locations where the divided copper foil 20 will be placed. Then, the copper foil 20 is placed on the printed silver oxide paste 20a, and the substrate portion 1a of the heat dissipation member 1 and the copper foil 20 are joined by heating while applying pressure in the atmosphere.

After that, as shown in FIG. 19(B), the copper foil 10 and the first conductor layer 2b of the wiring board 2 are joined via solder 21, and the second conductor layer 2c of the wiring board 2 and the semiconductor element 4 are joined via solder 3. In this way, as shown in FIG. 19(C), the copper foil 20 provided on the heat dissipation member 1 is soldered to the wiring board 2, and the wiring board 2 is soldered to the semiconductor element 4 at the same time. As a result, slits 22 are formed between the divided adjacent copper foils 20 and between the solders 21.

Next, as shown in FIG. 20(A), a Cu lead frame having a thickness of, for example, 0.6 mm and including main terminals 7a and signal terminals 7b is adhered to the heat dissipation member 1, wiring board 2, copper foil 20, and solder 21 using a silicone adhesive 5. At this time, it is heated, for example, at 140°C for 10 minutes.

After that, as shown in FIG. 20(A), the main terminal 7a and the semiconductor element 4 are wired with wire 8a using a wire bonder to form a main power circuit. Also, the signal terminal 7b and the semiconductor element 4 are wired with wire 8b using a wire bonder to form a signal circuit.

Finally, as shown in FIG. 20(B), the whole is sandwiched between a mold consisting of an upper mold 93 and a lower mold 94, and transfer molding resin is injected and hardened to perform insulation and sealing, completing the semiconductor device 500 that is insulated and sealed with the sealing material 51 as shown in FIG. 20(C).

The semiconductor device 500 and the manufacturing method for the semiconductor device 500 configured in this manner achieve the same effects as the semiconductor device 200 and the manufacturing method for the semiconductor device 200 of the second embodiment.

Embodiment 6.
A power conversion device according to a sixth embodiment, in which the semiconductor device according to any one of the first to fifth embodiments is mounted, will be described with reference to Fig. 21. Fig. 21 is a block diagram for explaining the power conversion device according to the present embodiment, and the whole of Fig. 21 shows a power conversion system to which the power conversion device according to the present embodiment is applied. Below, a specific description will be given of the case where the sixth embodiment is a three-phase inverter.

The power conversion system shown in FIG. 21 is composed of a power conversion device 600 of this embodiment, a power source 610, and a load 620. The power source 610 is a DC power source, and supplies DC power to the power conversion device 600. The power source 610 can be composed of various things, for example, a DC system, a solar cell, or a storage battery, or it may be composed of a rectifier circuit connected to an AC system or an AC/DC converter. The power source 610 may also be composed of a DC/DC converter that converts the DC power output from the DC system into a predetermined power.

The power conversion device 600 is a three-phase inverter connected between a power source 610 and a load 620, converts DC power supplied from the power source 610 to AC power, and supplies the AC power to the load 620. As shown in FIG. 21, the power conversion device 600 includes a main conversion circuit 601 that converts input DC power into AC power and outputs it, and a control circuit 603 that outputs a control signal to the main conversion circuit 601 to control the main conversion circuit 601.

The load 620 is a three-phase motor driven by AC power supplied from the power conversion device 600. Note that the load 620 is not limited to a specific use, but is a motor mounted on various electrical devices, and is used, for example, as a motor for hybrid cars, electric cars, railroad cars, elevators, or air conditioning equipment.

The power conversion device 600 of this embodiment will be described in detail below. The main conversion circuit 601 includes a switching element and a freewheeling diode (not shown), and the switching element switches to convert DC power supplied from the power source 610 into AC power, which is then supplied to the load 620. There are various specific circuit configurations for the main conversion circuit 601, but the main conversion circuit 601 according to this embodiment is a two-level three-phase full bridge circuit, and can be configured with six switching elements and six freewheeling diodes connected in reverse parallel to each switching element. The semiconductor device according to any one of the above-mentioned embodiments 1 to 5 is applied to at least one of the switching elements and freewheeling diodes of the main conversion circuit 601. The six switching elements are connected in series with two switching elements to form upper and lower arms, and each upper and lower arm forms each phase (U phase, V phase, W phase) of the full bridge circuit. The output terminals of each upper and lower arm, i.e., the three output terminals of the main conversion circuit 601, are connected to the load 620.

The main conversion circuit 601 also includes a drive circuit (not shown) for driving each switching element, but the drive circuit may be built into the semiconductor device 602, or may be configured to include a drive circuit separate from the semiconductor device 602. The drive circuit generates a drive signal for driving the switching element of the main conversion circuit 601 and supplies it to the control electrode of the switching element of the main conversion circuit 601. Specifically, in accordance with a control signal from a control circuit 603 (described later), a drive signal for turning the switching element on and a drive signal for turning the switching element off are output to the control electrode of each switching element. When the switching element is maintained in the on state, the drive signal is a voltage signal (on signal) equal to or higher than the threshold voltage of the switching element, and when the switching element is maintained in the off state, the drive signal is a voltage signal (off signal) equal to or lower than the threshold voltage of the switching element.

The control circuit 603 controls the switching elements of the main conversion circuit 601 so that the desired power is supplied to the load 620. Specifically, the time (on time) that each switching element of the main conversion circuit 601 should be in the on state is calculated based on the power to be supplied to the load 620. For example, the main conversion circuit 601 can be controlled by PWM control that modulates the on time of the switching elements according to the voltage to be output. Then, a control command (control signal) is output to the drive circuit provided in the main conversion circuit 601 so that an on signal is output to the switching element that should be in the on state at each point in time, and an off signal is output to the switching element that should be in the off state. The drive circuit outputs an on signal or an off signal as a drive signal to the control electrode of each switching element according to this control signal.

In the power conversion device of this embodiment, a semiconductor device according to any one of the first to fifth embodiments is applied to at least one of the switching elements and the free wheel diode of the main conversion circuit 601, which has the effect of improving reliability.

In this embodiment, an example of application to a two-level three-phase inverter has been described, but the present invention is not limited to this and can be applied to various power conversion devices. In this embodiment, a two-level power conversion device is used, but a three-level or multi-level power conversion device may also be used, and when supplying power to a single-phase load, the present embodiment may also be applied to a single-phase inverter. In addition, when supplying power to a DC load, the present embodiment can also be applied to a DC/DC converter or an AC/DC converter.

The power conversion device of this embodiment is not limited to the case where the load is an electric motor, but can also be used, for example, as a power supply device for an electric discharge machine, a laser processing machine, an induction heating cooker, or a non-contact power supply system, and can also be used as a power conditioner for a solar power generation system, a power storage system, etc.

In addition, the scope of this disclosure also includes combining, modifying, or omitting each embodiment as appropriate.

1 heat dissipation member, 2 wiring board, 2a ceramic base material (insulating layer), 2b first conductor layer, 2c second conductor layer, 3 solder (second bonding material), 4 semiconductor element,
10, 13, 20 Copper foil (metal layer), 11, 21 Solder (first bonding material), 22 Slit, 30 Mesh (metal layer),
100, 200, 400, 500, 602 Semiconductor device,
600 Power conversion device, 601 Main conversion circuit, 603 Control circuit

Claims (11)

A heat dissipation member having a substrate portion formed of Al or an Al alloy;
a metal layer provided on the substrate portion of the heat dissipation member and made of Cu or a Cu alloy, or Ni or a Ni alloy;
A first bonding material provided on the metal layer;
a wiring board including a first conductor layer provided on the first bonding material, the first conductor layer having at least a surface layer on the metal layer side formed of Cu or a Cu alloy, or Ni or a Ni alloy, an insulating layer provided on the first conductor layer, and a second conductor layer provided on the insulating layer;
a semiconductor element bonded onto the second conductor layer of the wiring board via a second bonding material;
The semiconductor device according to claim 1, wherein the thickness of the metal layer is 50% or less of the thickness of the substrate portion of the heat dissipation component. 2. The semiconductor device according to claim 1, wherein the substrate portion and the metal layer of the heat dissipation member are joined together by silver oxide. 3. The semiconductor device according to claim 1, wherein the metal layer has a plurality of holes formed therein. 3. The semiconductor device according to claim 1, wherein the metal layer has a mesh structure formed by weaving fine wires. 4. The semiconductor device according to claim 1, wherein the metal layer is divided into a plurality of pieces. The semiconductor device according to claim 5 , wherein the divided metal layer is provided directly below the semiconductor element. 7. The semiconductor device according to claim 1, wherein the heat dissipation member has a frame-shaped protrusion provided on the side of the substrate where the metal layer is provided, the frame-shaped protrusion surrounding the metal layer. A first step of joining a substrate portion of a heat dissipation member made of Al or an Al alloy to a metal layer made of Cu or a Cu alloy, or Ni or a Ni alloy;
a second step of bonding a surface of the metal layer opposite to the surface bonded to the substrate portion to a surface layer of a wiring board having an insulating layer, a first conductor layer provided on one surface of the insulating layer and having at least a surface layer opposite to the insulating layer made of Cu or a Cu alloy, or Ni or a Ni alloy, and a second conductor layer provided on the other surface of the insulating layer;
a third step of bonding the second conductor layer of the wiring board to a semiconductor element;
A method for manufacturing a semiconductor device, comprising the steps of: forming a heat sink on a substrate; forming a heat sink on the substrate; 9. The method for manufacturing a semiconductor device according to claim 8, wherein in the first step, the substrate portion of the heat dissipation component and the metal layer are joined together using a silver oxide paste. 10. The method for manufacturing a semiconductor device according to claim 8, wherein in the first step, a pressure is applied to the metal layer so as to sink the metal layer into the substrate portion using a jig having a protrusion. A main conversion circuit having the semiconductor device according to any one of claims 1 to 7, which converts input power and outputs the converted power;
a control circuit that outputs a control signal for controlling the main conversion circuit to the main conversion circuit;
A power conversion device comprising:

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