Semiconductor device and power conversion device

Abstract

Provided is a feature for improving cooling effects for a bus bar and a member connected thereto while shortening the bus bar. This semiconductor device is connected to a capacitor having the bus bar. The semiconductor device is provided with a semiconductor element, a case surrounding sides of the semiconductor element and having a case terminal of which one end part is connected to the bus bar, a cooler that is disposed on the lower side of the semiconductor element and is for cooling the semiconductor element, and a cooling block that is disposed between the case terminal and the cooler and is built into the case. The case terminal and the cooling block partially overlap in a top view.

Description

Semiconductor device and power conversion device

[0001] The present disclosure relates to a semiconductor device and a power conversion device.

[0002] In Patent Document 1, a structure is proposed in which a conductor portion (corresponding to a bus bar) connecting a power module and a smoothing capacitor is disposed so as to be in contact with a housing via an insulating layer, thereby cooling the bus bar during operation of an inverter.

[0003] Japanese Unexamined Patent Application Publication No. 2018-121457

[0004] However, in the technique described in Patent Document 1, since the routing of the bus bar is long, heat generation from the bus bar increases, and there is a problem that the cooling effect of the bus bar and members connected thereto is reduced.

[0005] Accordingly, an object of the present disclosure is to provide a technique capable of shortening the length of a bus bar and improving the cooling effect of the bus bar and members connected thereto.

[0006] A semiconductor device according to the present disclosure is a semiconductor device connected to a capacitor having a bus bar, the semiconductor device including: a semiconductor element; a case surrounding a side of the semiconductor element and having a case terminal of which one end portion is connected to the bus bar; a cooler disposed below the semiconductor element to cool the semiconductor element; and a cooling block disposed between the case terminal and the cooler and incorporated in the case, wherein the case terminal and the cooling block partially overlap in a top view.

[0007] According to the present disclosure, since one end portion of the case terminal included in the case is connected to the bus bar, the length of the bus bar can be shortened. Thereby, heat generation from the bus bar can be suppressed. Further, since the case terminal and the cooling block partially overlap in a top view, the cooling effect of the case terminal can be improved. As described above, the length of the bus bar can be shortened, and the cooling effect of the bus bar and the case terminal which is a member connected thereto can be improved.

[0008] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings.

[0009] Figure 1 is a cross-sectional view of a power converter according to Embodiment 1. Figure 2 is a top view of a semiconductor device according to Embodiment 1. Figure 3 is a top view of the semiconductor device according to Embodiment 1 with the top of the case hidden. Figure 4 is a perspective view of the cooling block and its surroundings provided by the semiconductor device according to Embodiment 1. Figure 5 is a perspective view showing the cooling block and case terminals of the semiconductor device according to Embodiment 1 overlapping. Figure 6 is a cross-sectional view taken along line A-A in Figure 2. Figure 7 is a cross-sectional view showing an example of a power converter according to Embodiment 2. Figure 8 is a cross-sectional view showing another example of a power converter according to Embodiment 2. Figure 9 is a cross-sectional view showing an example of a power converter according to Embodiment 3. Figure 10 is a cross-sectional view showing another example of a power converter according to Embodiment 3. Figure 11 is a block diagram showing the configuration of a power conversion system to which the power converter according to Embodiment 4 is applied.

[0010] <Embodiment 1> Embodiment 1 will be described below with reference to the drawings. Figure 1 is a cross-sectional view of the power conversion device according to Embodiment 1.

[0011] As shown in Figure 1, the power converter comprises a semiconductor device 202, a housing 1, and a capacitor 50 having busbars 51 and 52. The semiconductor device 202 is placed on the housing 1. The capacitor 50 is placed on the housing 1 adjacent to the semiconductor device 202. The capacitor 50 may be screwed to the housing 1.

[0012] The semiconductor device 202 comprises a semiconductor module 10, a case 20, a cooler 27 made of aluminum or copper, a plurality of cooling blocks 25, and a printed circuit board 21.

[0013] The cooler 27 is fixed to the housing 1 with screws 31, and the lower end 27a of the cooler 27 is positioned in a recess 2 provided on the upper surface of the housing 1. An O-ring (not shown) is placed between the cooler 27 and the housing 1. The semiconductor module 10 is fixed to the cooler 27 with a bonding material 28. It is preferable to arrange multiple semiconductor modules 10 on the cooler 27 in order to improve the output of the semiconductor device 202.

[0014] The semiconductor module 10 includes an insulating substrate 11 consisting of a ceramic insulating layer 11a and circuit patterns 11b and 11c arranged above and below it, a semiconductor element 12, a sealing material 16 that seals the semiconductor element 12 and the insulating substrate 11, and a lead frame 14 that is exposed from the sealing material 16. The circuit pattern 11c, which is located on the opposite side from the semiconductor element 12, is exposed from the sealing material 16.

[0015] The semiconductor element 12 is either an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The semiconductor material of the semiconductor element 12 is silicon (Si). The semiconductor element 12 and the circuit pattern 11b are joined together with solder or an internal bonding material 13 such as silver. The lead frame 14 is connected to the circuit pattern 11b or the semiconductor element 12 via wiring such as aluminum wire or the internal bonding material 13. Generally, a resin material such as epoxy is used as the encapsulating material 16.

[0016] The case 20 surrounds the side of the semiconductor device 202, which includes the semiconductor element 12, and has case terminals 22 and 23, one end of which is connected to the bus bars 51 and 52, respectively. The other ends of the case terminals 22 and 23 are connected to the lead frame 14. That is, the case terminals 22 and 23 are positioned between the bus bars 51 and 52 and the lead frame 14. In order to reduce losses in the power converter, it is necessary to reduce the inductance of the case terminals 22 and 23, so it is preferable that the case terminals 22 and 23 be formed as parallel flat plates. In the example in Figure 1, the lead frame 14 and the case terminals 22 and 23 are connected by welding. Also, the case terminals 22 and 23 and the bus bars 51 and 52 are connected by screws 55 and 56, respectively.

[0017] Furthermore, since large currents flow through the lead frame 14, case terminals 22 and 23, and busbars 51 and 52, it is preferable that they be made of copper, which has low electrical resistance. The case 20 also has case terminals 24. The case terminals 24 are terminals for controlling the semiconductor element 12 and are electrically connected to the through-holes 21a of the printed circuit board 21. In addition, the case terminals 22, 23, and 24 are held in the case 20 by insert molding, which makes it easier to achieve positional accuracy.

[0018] A feature of Embodiment 1 is that a cooling block 25 is built into the case 20. The cooling block 25 is positioned near the case terminals 22. The base end of the cooling block 25 is located on the inner circumference side of the cooler 27, and the tip of the cooling block 25 is located on the outer circumference side of the cooler 27. The case 20 is made of resin material, and a part of the case 20 made of resin material is positioned between the cooling block 25 and the case terminals 22. As a result, the cooling block 25 and the case terminals 22 are insulated from each other.

[0019] The lower surface of the cooling block 25 is exposed from the case 20, and the cooling block 25 is in contact with the cooler 27 via the heat dissipation material 26. In a power conversion device, the maximum current may be limited when an element (not shown) inside the capacitor 50 reaches its operating limit temperature. Therefore, if the temperature of the busbars 51 and 52 can be reduced when a large amount of power flows, the semiconductor device 202 can be made more densely packed.

[0020] In Embodiment 1, when the busbars 51, 52 or case terminals 22, 23 generate heat, the cooling block 25 absorbs heat from the case terminals 22, 23 and dissipates the heat through the heat dissipation material 26, thereby lowering the temperature of the busbars 51, 52. This makes it possible to increase the density of the semiconductor device 202.

[0021] Furthermore, since the case terminal 22 is located above the case terminal 23, it is difficult to dissipate heat to the cooler 27 through a part of the resin case 20, and therefore the temperature tends to rise. Heat is transferred to the bus bar 51 connected to the case terminal 22, causing the element temperature inside the capacitor 50 to rise, and the current density of the power converter becomes limited by the temperature rise of the case terminal 22. Therefore, by selectively cooling the case terminal 22 with the cooling block 25, it becomes possible to increase the density of the power converter. In addition, since the cooling block 25 can be mounted without increasing the length of components through which large currents flow, such as the lead frame 14, case terminals 22 and 23, and bus bars 51 and 52, it is easier to obtain effects such as low inductance and miniaturization in the semiconductor device 202.

[0022] Next, the positional relationship between the case terminals 22 and the cooling block 25 in a top view will be described. Figure 2 is a top view of the semiconductor device 202 according to Embodiment 1. Figure 3 is a top view of the semiconductor device 202 according to Embodiment 1 with the upper part of the case 20 hidden. Figure 4 is a perspective view of the cooling block 25 and its surroundings in the semiconductor device 202 according to Embodiment 1. Figure 5 is a perspective view showing the state in which the cooling block 25 and the case terminals 22 in the semiconductor device 202 according to Embodiment 1 are overlapping. Figure 6 is a cross-sectional view taken along line A-A in Figure 2.

[0023] As shown in Figures 2 to 5, the case terminal 22 and the cooling block 25 partially overlap in a top view. More specifically, in a top view, a portion of the case terminal 22, which is located on the upper side of the case terminals 22 and 23, overlaps with a portion of the cooling block 25. This enhances the cooling effect of the case terminal 22. Another important factor in improving cooling efficiency is that, as shown in Figures 4 and 5, the tip of the cooling block 25 extends in the direction of the bus bars 51 and 52 (see Figure 1). Specifically, the tip of the cooling block 25 is located at the connection point between the case terminals 22 and 23 and the bus bars 51 and 52. In particular, the fastening points between the bus bars 51 and 52 and the case terminals 22 and 23 tend to generate heat, so extending the tip of the cooling block 25 beyond these fastening points towards the capacitor 50 allows for efficient cooling.

[0024] Furthermore, the thinner the heat dissipation material 26, the greater the cooling effect on the busbars 51 and 52. For this reason, a thin heat dissipation material 26 with properties that allow it to spread easily is preferred. A grease containing a heat dissipation filler may be used as the heat dissipation material 26, but a silicone adhesive without a filler, which has a high gap-filling effect and can be made thin, may also be used.

[0025] Furthermore, as shown in Figure 1, the thickness of the heat dissipation material 26 can be reduced by fastening the case 20 and the cooler 27 with screws 29 and 30. This screw fastening structure makes it possible to reduce the thickness of the heat dissipation material 26 to 100 μm or less, thereby improving the cooling effect. In addition, by providing screw holes 25a on the lower surface of the cooling block 25 and fastening the cooling block 25 and the cooler 27 with screws 29, the thickness of the heat dissipation material 26 can be further reduced, thereby improving the heat dissipation effect of the semiconductor device 202.

[0026] Next, we will explain the dimensional relationships of the case terminals 22, 23, busbars 51, 52, and cooling block 25, which are well-suited to achieving the above-mentioned cooling effect.

[0027] As shown in Figure 1, when L1 is the length from the other end of the case terminal 22 to the connection point with the busbar 51, and L2 is the length from the base end of the busbar 51 to the connection point with the case terminal 22, it is preferable that the relationship L1 > L2 is satisfied. The case terminal 22 tends to have a complex shape in order to suppress inductance, and the amount of heat generated when a large current flows tends to increase, but by utilizing the heat dissipation function of the cooling block 25, the temperature rise of the case terminal 22 can be suppressed. In addition, since one end of the case terminal 22 is connected to the busbar 51, the length of the busbar 51 is shortened, and the heat generation of the busbar 51 can be suppressed, thereby extending the lifespan of the capacitor 50, which is sensitive to high temperatures. As a result, both low inductance and improved lifespan of the semiconductor device 202 can be achieved.

[0028] Next, as shown in Figure 6, when the distance between the case terminal 22 and the cooling block 25 is t1 and the thickness of the cooling block 25 is t2, it is preferable that the relationship t1 < t2 is satisfied. The smaller the distance t1 between the case terminal 22 and the cooling block 25, the easier it is for the heat generated by the case terminal 22 to be transferred to the cooling block 25, and the thicker the thickness t2 of the cooling block 25, the easier it is for the heat to dissipate horizontally within the cooling block 25. By satisfying the relationship t1 < t2, the heat generated from the case terminal 22 can be efficiently dissipated.

[0029] As described above, in Embodiment 1, the semiconductor device 202 is a semiconductor device 202 connected to a capacitor 50 having busbars 51 and 52. The semiconductor device 202 comprises a semiconductor element 12, a case 20 surrounding the sides of the semiconductor element 12 and having case terminals 22 and 23 at one end connected to the busbars 51 and 52, a cooler 27 positioned below the semiconductor element 12 to cool the semiconductor element 12, and a cooling block 25 positioned between the case terminals 22 and the cooler 27 and built into the case 20. The case terminals 22 and the cooling block 25 partially overlap in a top view.

[0030] The electrode conversion device also includes a semiconductor device 202 and a capacitor 50 having busbars 51 and 52 connected to one end of the case terminals 22 and 23. The base end of the cooling block 25 is located on the inner circumference side of the cooler 27, and the tip of the cooling block 25 is located at the connection point between the case terminals 22 and 23 and the busbars 51 and 52.

[0031] Therefore, since one end of the case terminals 22 and 23 of the case 20 is connected to the busbars 51 and 52, the length of the busbars 51 and 52 can be shortened. This suppresses heat generation from the busbars 51 and 52. In addition, since the case terminals 22 and the cooling block 25 partially overlap in a top view, the cooling effect of the case terminals 22 can be improved. Thus, the length of the busbars 51 and 52 can be shortened, and the cooling effect of the busbars 51 and 52 and the case terminals 22 and 23 connected to them can be improved.

[0032] Furthermore, the length of the busbars 51 and 52 can be shortened, which improves the flexibility of the layout.

[0033] Furthermore, the base end of the cooling block 25 is located on the inner circumference side of the cooler 27, and the tip of the cooling block 25 is located on the outer circumference side of the cooler 27. Therefore, the cooling effect of the busbars 51 and 52 and the case terminals 22 and 23 connected to them can be improved.

[0034] Furthermore, the semiconductor device 202 is equipped with multiple case terminals, and the multiple case terminals 22, 23 form a parallel plate. In a top view, the upper case terminal 22 of the multiple case terminals 22, 23 overlaps with a part of the cooling block 25.

[0035] Therefore, the effect of reducing the inductance of case terminals 22 and 23 and the cooling effect of case terminal 22 can be enhanced. In addition, the structure can be simplified by selectively cooling the upper case terminal 22, which is the thermal rate limiting factor. This enables higher density and miniaturization of the power conversion device.

[0036] Furthermore, the semiconductor device 202 further includes a lead frame 14 connected to the semiconductor element 12. The lead frame 14 and case terminals 22, 23 are connected by welding. The case terminals 22, 23 and busbars 51, 52 are connected by screw fastening.

[0037] To shorten the current path from the semiconductor module 10 to the capacitor 50, welding, which allows connection in a relatively small space, is preferred. However, considering the ease of assembly of the power conversion device, screw fastening is more feasible for connecting the busbars 51 and 52 to the case terminals 22 and 23. This makes it possible to achieve both miniaturization and ease of assembly in the power conversion device.

[0038] Furthermore, the case 20 is made of resin, and a portion of the case 20 is positioned between the cooling block 25 and the case terminals 22. Therefore, the cooling block 25 and the case terminals 22 can be insulated without using another insulating material. This reduces the number of parts and simplifies the structure, leading to miniaturization of the semiconductor device 202.

[0039] Since the heat dissipation material is disposed between the cooling block and the cooler, heat can be efficiently dissipated from the cooling block to the cooler. Thereby, the cooling effect of the bus bars and the case terminals which are members respectively connected to these bus bars can be further improved.

[0040] Furthermore, since the thickness of the heat dissipation material is 100 μm or less, the cooling effect of the bus bars and the case terminals which are members respectively connected to these bus bars can be further improved.

[0041] The heat dissipation material includes a silicone adhesive containing no filler. The case and the cooler are fastened with screws. Further, the cooling block is provided with a screw hole, and the cooling block and the cooler are fastened with screws. Therefore, the structure in which the heat dissipation material is disposed between the cooling block and the cooler can be easily realized.

[0042] Further, when a length from the other end of the case terminal to a connection point with the bus bar is defined as L1, and a length from a base end of the bus bar to a connection point with the case terminal is defined as L2, the relationship of L1>L2 is satisfied.

[0043] The case terminal is directly cooled by the cooling block, but the bus bar is cooled via the case terminal, so it is important to suppress heat generation of the bus bar. With this structure, heat generation of the bus bar can be suppressed while the case terminal is cooled by the cooling block, so that the service life of the capacitor which is vulnerable to high temperatures can be extended. As a result, both lower inductance and longer service life of the semiconductor device can be achieved.

[0044] Further, when a distance between the case terminal and the cooling block is defined as t1, and a thickness of the cooling block is defined as t2, the relationship of t1<t2 is satisfied.

[0045] The smaller the distance t1 between the case terminal 22 and the cooling block 25, the more easily the heat generated by the case terminal 22 is transferred to the cooling block 25, and the larger the thickness t2 of the cooling block 25, the more easily heat is dissipated in the horizontal direction within the cooling block 25. By satisfying the relationship of t1 < t2, the heat generated from the case terminal 22 can be efficiently dissipated.

[0046] <Embodiment 2> Next, Embodiment 2 will be described. FIG. 7 is a cross-sectional view showing an example of the power conversion device according to Embodiment 2. FIG. 8 is a cross-sectional view showing another example of the power conversion device according to Embodiment 2. In Embodiment 2, the same components as those described in Embodiment 2 are denoted by the same reference numerals, and descriptions thereof are omitted.

[0047] As shown in FIG. 7 and FIG. 8, Embodiment 2 has a structure in which the case 20 is filled with a sealing material 35 that seals the semiconductor module 10 including the semiconductor element 12. The other end portions of the case terminals 22 and 23 are located inside the case 20 and covered with the sealing material 35. The sealing material 35 is gel or epoxy. A lid 36 that covers the upper surface of the sealing material 35 is attached to the upper end portion of the case 20.

[0048] Further, in Embodiment 1, the lead frame 14 constitutes the current path from the semiconductor element 12 to the case terminals 22, 23, and 24. In contrast, in Embodiment 2, as shown in FIG. 7, the wire wiring 15 made of aluminum or copper constitutes the current path from the semiconductor element 12 to the case terminals 22, 23, and 24. Alternatively, as shown in FIG. 8, a conductive plate member 37 and a bonding material 38 such as solder constitute the current path from the semiconductor element 12 to the case terminals 22, 23, and 24. The plate member 37 includes the circuit pattern 11b and the case terminal 23.

[0049] The structures shown in Figures 7 and 8 have fewer components and connection points (in other words, fastening points) in the current-flow path compared to the structure shown in Figure 1 of Embodiment 1. This increases the degree of freedom in arranging the cooling block 25 and improves the cooling efficiency of the semiconductor device 202. Furthermore, since less heat is generated when current flows, the temperature of the busbars 51 and 52 can be reduced, leading to higher density of the semiconductor device 202. In particular, the structure shown in Figure 8 allows for a larger cross-sectional area of ​​the wiring in the current path, making it possible to reduce the electrical resistance of the wiring.

[0050] As described above, in the second embodiment, the semiconductor device 202 is filled inside the case 20 and further comprises a sealing material 35 that seals the semiconductor element 12. The other ends of the case terminals 22, 23, and 24 are located inside the case 20 and covered by the sealing material 35.

[0051] Therefore, the degree of freedom in arranging the cooling block 25 is increased, and the cooling efficiency of the semiconductor device 202 can be improved. In addition, since the temperature of the busbars 51 and 52 can be reduced, it leads to increased density of the semiconductor device 202.

[0052] In particular, in the structure shown in Figure 8, the current path from the semiconductor element 12 to the case terminals 22, 23, and 24 is formed within the case 20 using a conductive plate material 37 and a bonding material 38, thereby reducing the electrical resistance of the wiring.

[0053] <Embodiment 3> Next, Embodiment 3 will be described. Figure 9 is a cross-sectional view showing an example of a power conversion device according to Embodiment 3. Figure 10 is a cross-sectional view showing another example of a power conversion device according to Embodiment 3. In Embodiment 3, the same reference numerals are used for components that are the same as those described in Embodiments 1 and 2, and their descriptions are omitted.

[0054] In Embodiment 3, the structure around the cooling block 25 differs from that in Embodiment 1. Specifically, as shown in Figure 9, an insulating material 39 is placed between the case terminal 22 and the cooling block 25.

[0055] Generally, the thermal conductivity of the resin material that makes up the case 20 is low, so using a separate insulating material 39 can improve cooling efficiency. By inserting the insulating material 39 and the cooling block 25 during the molding of the case 20, the insulating material 39 can be stably formed even if its thickness is 0.5 mm or less, thus improving the cooling effect.

[0056] Furthermore, in the structure shown in Figure 1, screws 55 and nuts 53 are used to connect the case terminal 22 and the busbar 51, whereas in the structure shown in Figure 10, screw holes 25b are provided in the cooling block 25, and the busbar 51 and the case terminal 22 are screw-fastened to the cooling block 25.

[0057] Furthermore, in order to ensure insulation between the cooler 27 and the cooling block 25, a portion of the case 20 is placed between the heat dissipation material 26 and the cooling block 25. With this structure, no material with low thermal conductivity is placed on the heat conduction path from the case terminal 22 to the cooling block 25, so that cooling can be rapidly performed from the case terminal 22 to the cooling block 25. The higher the heat capacity of the cooling block 25, the greater the cooling effect.

[0058] As described above, in Embodiment 3, since an insulating material 39 is placed between the case terminal 22 and the cooling block 25, the cooling efficiency can be increased compared to the case where a part of the case 20 is placed between the case terminal 22 and the cooling block 25.

[0059] Furthermore, since the thickness of the insulating material 39 is 0.5 mm or less, the cooling effect can be enhanced.

[0060] Furthermore, since the insulating material 39 and the cooling block 25 are integrally molded with the case 20, it becomes easier to achieve a thickness of 0.5 mm or less for the insulating material 39.

[0061] Furthermore, screw holes 25b are provided in the cooling block 25, and the busbar 51 and case terminals 22 are screw-fastened to the cooling block 25. Therefore, the cooling effect on the busbar 51 is enhanced, making it possible to increase the density of the power conversion device.

[0062] Furthermore, a heat dissipation material 26 is placed between the cooling block 25 and the cooler 27. The case 20 is made of resin, and a part of the case 20 is placed between the heat dissipation material 26 and the cooling block 25. Therefore, it becomes easier to realize a structure in which the busbar 51 and case terminal 22 are screw-fastened to the cooling block 25 without using nuts 53.

[0063] <Modifications of Embodiments 1 to 3> Next, modifications of Embodiments 1 to 3 will be described.

[0064] In embodiments 1 to 3, the semiconductor element 12 may be an RC-IGBT (Reverse Conducting IGBT). This reduces the number of semiconductor elements 12, thereby enabling further miniaturization of the semiconductor device 202.

[0065] Furthermore, in embodiments 1 to 3, the semiconductor material of the semiconductor element 12 may be SiC. By using low-loss SiC as the semiconductor material, miniaturization and high density of the semiconductor device 202 can be achieved.

[0066] <Embodiment 4> This embodiment applies the semiconductor device 202 according to Embodiments 1 to 3 described above to a power converter. The application of the semiconductor device 202 according to Embodiments 1 to 3 is not limited to a specific power converter, but below, as Embodiment 4, we will describe the case in which the semiconductor device 202 according to Embodiments 1 to 3 is applied to a three-phase inverter.

[0067] Figure 11 is a block diagram showing the configuration of a power conversion system to which the power conversion device according to Embodiment 4 is applied.

[0068] The power conversion system shown in Figure 11 consists of a power supply 100, a power conversion device 200, and a load 300. The power supply 100 is a DC power supply and supplies DC power to the power conversion device 200. The power supply 100 can be made up of various components, for example, a DC grid, a solar cell, or a storage battery, or it may be made up of a rectifier circuit or AC / DC converter connected to an AC grid. Alternatively, the power supply 100 may be made up of a DC / DC converter that converts DC power output from a DC grid into a predetermined power.

[0069] The power converter 200 is a three-phase inverter connected between the power supply 100 and the load 300. It converts the DC power supplied from the power supply 100 into AC power and supplies the AC power to the load 300. As shown in Figure 11, the power converter 200 includes a main conversion circuit 201 that converts DC power into AC power and outputs it, and a control circuit 203 that outputs a control signal to the main conversion circuit 201 to control the main conversion circuit 201.

[0070] Load 300 is a three-phase motor driven by AC power supplied from power converter 200. Note that load 300 is not limited to a specific application; it is a motor mounted in various electrical devices, such as hybrid vehicles, electric vehicles, railway vehicles, elevators, or air conditioning equipment.

[0071] The details of the power converter 200 are described below. The main conversion circuit 201 includes switching elements (not shown) and freewheeling diodes (not shown). By switching the switching elements, it converts the DC power supplied from the power supply 100 into AC power and supplies it to the load 300. There are various specific circuit configurations for the main conversion circuit 201, but the main conversion circuit 201 according to this embodiment is a two-level three-phase full-bridge circuit and can be composed of six switching elements and six freewheeling diodes antiparallel to each switching element. At least one of the switching elements and freewheeling diodes of the main conversion circuit 201 is fitted with a semiconductor device 202 according to any of the above embodiments 1 to 3. The six switching elements are connected in series in pairs to form upper and lower arms, and each upper and lower arm constitutes 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 201, are connected to the load 300.

[0072] Furthermore, the main conversion circuit 201 includes a drive circuit (not shown) for driving each switching element. The drive circuit may be built into the semiconductor device 202, or it may be configured to be a separate drive circuit from the semiconductor device 202. The drive circuit generates a drive signal to drive the switching elements of the main conversion circuit 201 and supplies it to the control electrodes of the switching elements of the main conversion circuit 201. Specifically, according to a control signal from the control circuit 203, which will be described later, it outputs a drive signal to turn on the switching element and a drive signal to turn off the switching element to the control electrodes of each switching element. When the switching element is kept in the ON state, the drive signal is a voltage signal (ON signal) that is greater than or equal to the threshold voltage of the switching element, and when the switching element is kept in the OFF state, the drive signal is a voltage signal (OFF signal) that is less than or equal to the threshold voltage of the switching element.

[0073] The control circuit 203 controls the switching elements of the main converter circuit 201 so that the desired power is supplied to the load 300. Specifically, it calculates the time (on time) that each switching element of the main converter circuit 201 should be in the ON state based on the power to be supplied to the load 300. For example, the main converter circuit 201 can be controlled by PWM control, which modulates the ON time of the switching elements according to the voltage to be output. The control circuit then outputs a control command (control signal) to the drive circuit of the main converter circuit 201 so that an ON signal is output to the switching elements that should be in the ON state at each point in time, and an OFF signal is output to the switching elements 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.

[0074] In the power conversion device according to this embodiment, the semiconductor device 202 according to Embodiments 1 to 3 is used as the switching element and freewheeling diode of the main conversion circuit 201, thereby enabling miniaturization.

[0075] In this embodiment, an example of applying the semiconductor device 202 according to Embodiments 1 to 3 to a two-level three-phase inverter has been described. However, the application of the semiconductor device 202 according to Embodiments 1 to 3 is not limited to this, and it 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 semiconductor device 202 according to Embodiments 1 to 3 may be applied to a single-phase inverter. Furthermore, when supplying power to a DC load, etc., it is also possible to apply the semiconductor device 202 according to Embodiments 1 to 3 to a DC / DC converter or an AC / DC converter.

[0076] Furthermore, the power conversion device to which the semiconductor device 202 according to Embodiments 1 to 3 is applied 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 electrical discharge machining, laser processing machines, induction heating cookers, or non-contact power supply systems, and can even be used as a power conditioner for solar power generation systems or energy storage systems.

[0077] Although this disclosure has been described in detail, the above description is illustrative and not limiting in all respects. It is understood that countless variations not illustrated are conceivable.

[0078] Furthermore, it is possible to freely combine each embodiment, or to modify or omit each embodiment as appropriate.

[0079] 12 Semiconductor element, 14 Lead frame, 22, 23 Case terminals, 25 Cooling block, 25a, 25b Screw holes, 26 Heat dissipation material, 27 Cooler, 35 Encapacitating material, 37 Plate material, 38 Bonding material, 39 Insulating material, 50 Capacitor, 51, 52 Busbar, 200 Power converter, 201 Main converter circuit, 202 Semiconductor device, 203 Control circuit.

Claims

1. A semiconductor device connected to a capacitor having a busbar, comprising: a semiconductor element; a case surrounding the side of the semiconductor element and having a case terminal at one end connected to the busbar; a cooler disposed below the semiconductor element for cooling the semiconductor element; and a cooling block disposed between the case terminal and the cooler and built into the case, wherein the case terminal and the cooling block partially overlap in a top view.

2. The semiconductor device according to claim 1, wherein the base end of the cooling block is located on the inner circumference side of the cooler, and the tip of the cooling block is located on the outer circumference side of the cooler.

3. The semiconductor device according to claim 1, wherein it is provided with a plurality of case terminals, the plurality of case terminals form a parallel plate, and in a top view, the case terminal located on the upper side of the plurality of case terminals overlaps with a part of the cooling block.

4. A power conversion device comprising: a semiconductor device according to claim 1; and a capacitor having a busbar connected to one end of the case terminal, wherein the base end of the cooling block is located on the inner circumference side of the cooler; and the tip of the cooling block is located at the connection point between the case terminal and the busbar.

5. The power conversion device according to claim 4, wherein the semiconductor device further comprises a lead frame connected to the semiconductor element, the lead frame and the case terminals are connected by welding, and the case terminals and the busbars are connected by screw fastening.

6. The semiconductor device according to claim 1, wherein the case is made of a resin material, and a part of the case is arranged between the cooling block and the case terminals.

7. The semiconductor device according to claim 1, wherein a heat dissipation material is arranged between the cooling block and the cooler.

8. The semiconductor device according to claim 7, wherein the thickness of the heat dissipation material is 100 μm or less.

9. The semiconductor device according to claim 8, wherein the heat dissipation material includes a silicone adhesive that does not contain fillers.

10. The semiconductor device according to claim 8, wherein the case and the cooler are fastened together with screws.

11. The semiconductor device according to claim 8, wherein the cooling block is provided with screw holes, and the cooling block and the cooler are fastened together with screws.

12. The power conversion device according to claim 4, wherein the relationship L1 > L2 is satisfied when L1 is the length from the other end of the case terminal to the connection point with the busbar, and L2 is the length from the base end of the busbar to the connection point with the case terminal.

13. The semiconductor device according to claim 1, wherein the distance between the case terminal and the cooling block is t1, and the thickness of the cooling block is t2, such that the relationship t1 < t2 is satisfied.

14. The semiconductor device according to claim 1, further comprising a sealing material filled inside the case to seal the semiconductor element, wherein the other end of the case terminal is located inside the case and covered by the sealing material.

15. The semiconductor device according to claim 14, wherein a current path from the semiconductor element to the case terminal is formed within the case using a conductive plate material and a bonding material.

16. The semiconductor device according to claim 6, wherein an insulating material is placed between the case terminal and the cooling block.

17. The semiconductor device according to claim 16, wherein the thickness of the insulating material is 0.5 mm or less.

18. The semiconductor device according to claim 16, wherein the insulating material and the cooling block are integrally molded with the case.

19. The power conversion device according to claim 4, wherein the cooling block is provided with screw holes, and the busbar and the case terminals are screw-fastened to the cooling block.

20. The power conversion device according to claim 19, wherein a heat dissipation material is placed between the cooling block and the cooler, the case is made of a resin material, and a part of the case is placed between the heat dissipation material and the cooling block.

21. The semiconductor device according to any one of claims 1 to 3, 6 to 11, and 13 to 18, wherein the semiconductor element is an RC-IGBT (Reverse Conducting IGBT).

22. The power conversion device according to any one of claims 4, 5, 12, 19, and 20, wherein the semiconductor element is an RC-IGBT (Reverse Conducting IGBT).

23. The semiconductor device according to any one of claims 1 to 3, 6 to 11, 13 to 18, and 21, wherein the semiconductor material of the semiconductor element is SiC.

24. The power conversion device according to any one of claims 4, 5, 12, 19, 20, and 22, wherein the semiconductor material of the semiconductor element is SiC.

25. A power conversion device comprising a semiconductor device according to any one of claims 1 to 3, 6 to 11, 13 to 18, 21, and 23, a main conversion circuit that converts and outputs input power, and a control circuit that outputs a control signal to the main conversion circuit for controlling the main conversion circuit.

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