Semiconductor device and power conversion device

Abstract

When viewed from the stacking direction of a base member and semiconductor substrates, a case comprises: a surrounding wall having an opening section for storing a plurality of semiconductor substrates; and a beam section that straddles the opening section and is supported by the surrounding wall so as to form a gap with the base member. The beam section internally includes a control terminal connected to the semiconductor substrates via a wire and is arranged so that at least a part thereof overlaps the semiconductor substrates when viewed from the stacking direction.

Description

Semiconductor device and power conversion device

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

[0002] For example, Patent Document 1 discloses a power semiconductor module including a plurality of semiconductor elements. The power semiconductor module disclosed in Patent Document 1 includes a case arranged to surround the plurality of semiconductor elements. Each semiconductor element is connected to a terminal molded in the case by a bonding wire.

[0003] Japanese Patent Application Laid-Open No. 2016-164919

[0004] Incidentally, semiconductor devices including semiconductor elements, such as the power semiconductor module disclosed in Patent Document 1, must be installed in limited spaces, such as inside a vehicle, and there is a constant demand for miniaturization of their shape in plan view, etc. The power semiconductor module disclosed in Patent Document 1 requires a case that surrounds the semiconductor substrate including the semiconductor elements from the outside to have portions for molding pin-shaped terminals. This results in an increase in the size of the case in plan view, making it impossible to sufficiently miniaturize the semiconductor device.

[0005] The present invention has been made in view of the above-mentioned problems, and has as its object to realize miniaturization of a semiconductor device having a case that encloses a plurality of semiconductor substrates.

[0006] The present invention employs the following configuration as a means for solving the above problems.

[0007] A first aspect of the present invention is a semiconductor device comprising a base member, a plurality of semiconductor substrates arranged on a surface of the base member, and a case fixed to the base member and enclosing the plurality of semiconductor substrates, wherein the case comprises, when viewed from the stacking direction of the base member and the semiconductor substrates, a surrounding wall portion having an opening for accommodating the plurality of semiconductor substrates, and a beam portion supported by the surrounding wall portion so as to straddle the opening and form a gap between the base member and the case, and the beam portion contains a control terminal connected to the semiconductor substrates via a wire, and is arranged so that at least a portion of the beam portion overlaps the semiconductor substrates when viewed from the stacking direction.

[0008] A second aspect of the present invention is a power conversion device that includes the semiconductor device of the first aspect and performs power conversion using the semiconductor device.

[0009] According to the present invention, the case includes a surrounding wall portion surrounding multiple semiconductor substrates and a beam portion spanning an opening in the surrounding wall portion. Furthermore, the beam portion includes a control terminal connected to the semiconductor substrates via a wire. Therefore, the present invention eliminates the need to include the control terminal in the surrounding wall portion, allowing the case to be compact in plan view. Furthermore, because a gap is provided between the beam portion and the base member, the multiple semiconductor substrates can be densely arranged without interfering with the beam portion. Therefore, the present invention reduces the space required for installing the multiple semiconductor substrates and allows the case to be compact in plan view. Therefore, the present invention allows for miniaturization of a semiconductor device including a case surrounding multiple semiconductor substrates.

[0010] 1 is a circuit diagram showing a schematic electrical configuration of a power conversion device according to one embodiment of the present embodiment; FIG. 2 is an exploded perspective view showing a schematic structural configuration of a power conversion device according to one embodiment of the present embodiment; FIG. 3 is a schematic exploded perspective view of a power module included in an intelligent power module of a power conversion device according to one embodiment of the present embodiment; FIG. 4 is a schematic enlarged cross-sectional view including one power device of a power module according to one embodiment of the present embodiment; FIG. 5 is a schematic enlarged cross-sectional view showing an enlarged joint portion between a bus bar connected to a positive electrode of a battery and a power device; FIG. 6 is a schematic enlarged plan view including one power device of a power module according to one embodiment of the present embodiment; FIG. 7 is a plan view of a power device according to one embodiment of the present embodiment; FIG. 8 is a perspective view of a mounting substrate included in a power device according to one embodiment of the present embodiment; and FIG. 9 is a flowchart showing a part of a manufacturing process of a power module according to one embodiment of the present embodiment.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor device and a power conversion device according to the present invention will be described below with reference to the drawings.

[0012] 1 is a circuit diagram showing a schematic electrical configuration of a power conversion device 1 of this embodiment. The power conversion device 1 of this embodiment is mounted on a vehicle such as an electric automobile and is provided between a motor M and a battery B. The power conversion device 1 of this embodiment performs power conversion between the motor M and the battery B. For example, the power conversion device 1 of this embodiment converts DC power supplied from the battery B into three-phase AC power and supplies it to the motor M. The power conversion device 1 also converts regenerative power (AC power) from the motor M into DC power and supplies it to the battery B.

[0013] As shown in FIG. 1 , the power conversion device 1 of this embodiment has a power conversion circuit H. As described above, the power conversion circuit H converts DC power into AC power. The power conversion circuit H also converts AC power into DC power. The power conversion circuit H includes a capacitor C and an inverter circuit E. The power conversion device 1 may also include, for example, a step-up / step-down converter or a DC / DC converter (not shown). If the vehicle has multiple motors M, the power conversion device 1 may also include multiple inverter circuits E.

[0014] The power conversion device 1 of this embodiment also includes a conductive line BU through which power is conducted. For example, the power conversion device 1 of this embodiment includes a conductive line BU that connects the inverter circuit E and the battery B, and a conductive line BU that connects the inverter circuit E and the motor M.

[0015] As shown in FIG. 1 , the inverter circuit E includes three legs R corresponding to the respective phases of the motor M. Each leg R includes an upper arm HA and a lower arm LA. The upper arm HA is connected to the positive electrode side of a battery B via a conductive line BU. The lower arm LA is connected to the negative electrode side of the battery B via a conductive line BU. The upper arm HA and the lower arm LA are connected in series. An output terminal that connects the legs R and the motor M is connected between the upper arm HA and the lower arm LA.

[0016] 1, the power conversion device 1 of this embodiment includes power devices 20 (semiconductor substrates) corresponding to each leg R. That is, in this embodiment, the power conversion device 1 includes three power devices 20. Each power device 20 includes a power transistor corresponding to the upper arm HA and a power transistor corresponding to the lower arm. That is, in this embodiment, each power device 20 includes two power transistors. Each of these power transistors is formed using a plurality of semiconductor elements.

[0017] Fig. 2 is an exploded perspective view showing a schematic structural configuration of the power conversion device 1 of this embodiment. As shown in Fig. 2, the power conversion device 1 of this embodiment includes an inverter case 2, an intelligent power module 3, and a capacitor unit 4. The power conversion device 1 may also include other components, such as a reactor unit forming a step-up / step-down circuit and a DC-DC converter unit forming a DC-DC converter. When multiple inverter circuits E are included, the power conversion device 1 may also include multiple intelligent power modules 3. The power conversion device 1 may also include a step-up / step-down circuit unit separate from the intelligent power module 3.

[0018] The inverter case 2 is a case that houses the intelligent power module 3, the capacitor unit 4, etc., and includes a center plate 2a and a case cover 2b. The center plate 2a and the case cover 2b are formed as separate parts that can be detached from each other. Note that FIG. 2 illustrates a state in which the case cover 2b is separated above the center plate 2a. However, the installation posture of the power conversion device 1 is not particularly limited. In other words, the power conversion device 1 may be mounted on a vehicle so that the case cover 2b is located to the side of the center plate 2a.

[0019] The central plate 2a has a bottom wall to which the intelligent power modules 3 and the capacitor units 4 are fixed, and side walls that surround the intelligent power modules 3 and the capacitor units 4. In other words, the central plate 2a is formed in the shape of a container that is open on the case cover 2b side. Such central plate 2a is provided with water channels as necessary, and is formed to be able to guide the coolant that cools the intelligent power modules 3 and the capacitor units 4.

[0020] The case cover 2b is fixed to the center plate 2a and covers the intelligent power modules 3 and the capacitor units 4. That is, the intelligent power modules 3 and the capacitor units 4 are exposed when the case cover 2b is detached from the center plate 2a.

[0021] Such an inverter case 2 is fixed to, for example, a housing (not shown) that covers the motor M or a gear case that houses a gear that transmits power generated by the motor M to the outside. In such a case, for example, the center plate 2a is fastened to the motor housing or the gear case using a bolt (not shown) or the like. Note that if the housing that covers the motor M has a space for accommodating the power conversion device 1, the case cover 2b may be omitted.

[0022] The inverter case 2 also holds bus bars that form part or all of the conductive line BU (see Figure 1) that connects the battery B to the intelligent power module 3 and the capacitor unit 4, and the conductive line BU (see Figure 1) that connects the intelligent power module 3 to the motor M.

[0023] The intelligent power module 3 includes a power module 3a (semiconductor device) and a substrate unit 3b. The power module 3a is a module provided with a plurality of power devices 20 (described later). In other words, the power module 3a forms an inverter circuit E with the plurality of power devices 20.

[0024] The board unit 3b is stacked on the power module 3a. This board unit 3b includes, for example, a gate driver board and an ECU (Electronic Control Unit) board. The gate driver board is a board provided with a gate driver that generates a drive signal for the inverter circuit E formed by the power module 3a. The ECU board is a board provided with an ECU that controls the gate driver board.

[0025] The capacitor unit 4 is a unit that houses a capacitor element therein. The capacitor unit 4 is connected to the power module 3a. The capacitor unit 4 forms the capacitor C shown in FIG. 1.

[0026] 3 is a schematic exploded perspective view of a power module 3a included in the intelligent power module 3. As shown in this figure, the power module 3a includes a module case 10 (case), the above-described power device 20 (semiconductor substrate), a heat sink 30 (base member), and a lead frame 40.

[0027] The module case 10 is a resin case that houses the power devices 20 and the like. In this embodiment, the module case 10 includes a surrounding wall 11 and a plurality of beams 12. When viewed from the stacking direction of the power devices 20 and the heat sink 30, the surrounding wall 11 has an opening 11a that houses the plurality of power devices 20.

[0028] In this embodiment, the surrounding wall 11 is formed in a substantially rectangular shape when viewed from the stacking direction, and is provided so as to surround all of the power devices 20 included in the power module 3a. In this embodiment, the power module 3a includes three power devices 20. These three power devices 20 are arranged in one direction when viewed from the stacking direction. The surrounding wall 11 is formed in the shape of a rectangular frame whose longitudinal direction is the arrangement direction of these power devices 20 and whose lateral direction is a direction perpendicular to the longitudinal direction and the stacking direction.

[0029] In this embodiment, the control terminal 70, which will be described later, is contained within the beam portion 12. Therefore, the surrounding wall portion 11 does not contain the control terminal 70. Therefore, in this embodiment, the surrounding wall portion 11 does not have a portion that contains the control terminal 70. Such a surrounding wall portion 11 has a thinner thickness in the direction perpendicular to the stacking direction, compared to a case where the surrounding wall portion 11 has a portion that contains the control terminal 70.

[0030] 4 is a schematic cross-sectional view of the power module 3a with one power device 20 enlarged. As shown in FIG. 4, the surrounding wall 11 of the module case 10 is fixed onto the heat sink 30 via an adhesive 50. In this way, the module case 10 is fixed to the surface 30a of the heat sink 30 so as to surround the power device 20.

[0031] Each beam portion 12 is formed to straddle the opening 11a of the surrounding wall portion 11. Each beam portion 12 is formed to extend linearly in a direction perpendicular to the arrangement direction of the power devices 20 (the short-side direction of the surrounding wall portion 11). That is, each beam portion 12 is a linear portion whose extension direction is the direction perpendicular to the arrangement direction of the power devices 20 (the short-side direction of the surrounding wall portion 11). Both ends of each beam portion 12 are connected to the surrounding wall portion 11, and each beam portion 12 is supported in a state spaced apart from the surface 30a of the heat sink 30. That is, each beam portion 12 is supported by the surrounding wall portion 11 and is arranged to form a gap between itself and the heat sink 30, as shown in FIG. 4 .

[0032] 4, each beam portion 12 is arranged so that at least a portion thereof overlaps with a power device 20 when viewed from the stacking direction. Each beam portion 12 includes a control terminal 70 therein, which is connected to the power device 20 via a bonding wire 80 (described later). A plurality of control terminals 70 are provided for each power device 20. These control terminals 70 are arranged along the extension direction of the beam portion 12. In other words, each beam portion 12 is formed so as to include a plurality of control terminals 70 arranged along the extension direction.

[0033] 4, the power devices 20 are located below each beam portion 12. The lower surface of each beam portion 12 is located above the upper surface of the power device 20 and is not in contact with the upper surface of the power device 20. In other words, each beam portion 12 is disposed with a gap between it and the power device 20 in the stacking direction.

[0034] A bus bar 60 and a control terminal 70 are molded into the module case 10. The bus bar 60 is enclosed in the surrounding wall portion 11 of the module case 10. In this embodiment, the power conversion device 1 of this embodiment includes a bus bar 60 (hereinafter referred to as a bus bar 61) that conducts power between the battery B and the power device 20, and a bus bar 60 (hereinafter referred to as a bus bar 62) that conducts power between the power device 20 and the motor M.

[0035] The bus bar 61 is molded into the module case 10 with a connection terminal 61a (see FIG. 3) on the battery B side and the portion where the lead frame 40 is joined exposed from the module case 10. The connection terminal 61a is connected to the capacitor unit 4 and a power supply terminal (not shown), and is connected to the battery B via the power supply terminal.

[0036] The power module 3a includes a bus bar 61 connected to the anode of battery B and a bus bar 61 connected to the cathode of battery B. In this embodiment, of these bus bars 61, the bus bar 61 connected to the anode of battery B is directly joined to the power device 20 without using the lead frame 40. Of these bus bars 61, the bus bar 61 connected to the cathode of battery B is connected to the power device 20 via the lead frame 40.

[0037] 5 is a schematic cross-sectional view showing an enlarged view of a joint portion between a bus bar 61 connected to the anode of battery B and a power device 20. As shown in this figure, the bus bar 61 connected to the anode of battery B has a joint piece 61b (joint portion) that is soldered to the power device 20. The joint piece 61b is a plate-shaped portion that protrudes from the main body of the bus bar 61 to a position above the power device 20.

[0038] 5, the module case 10 also includes a holding portion 13 that holds the joining piece 61b. The holding portion 13 is a portion that protrudes from the surrounding wall portion 11 of the module case 10 toward the power device 20 so as to hold the joining piece 61b from above. The holding portion 13 and the joining piece 61b are provided with a through hole 14 that penetrates in the vertical direction. This through hole 14 penetrates in the vertical direction through the integrated holding portion 13 and joining piece 61b. A solder bar is inserted into this through hole 14 during the reflow process, which will be described later. The solder bar inserted into the through hole 14 is melted during the reflow process, thereby joining the joining piece 61b and the power device 20.

[0039] In this embodiment, the joint piece 61b is soldered to an extension portion 24a2 (described later) of the power device 20. Note that the bus bar 61 connected to the negative electrode of the battery B and the bus bar 62 (described later) can also be directly joined to the power device 20 without using the lead frame 40.

[0040] The bus bar 62 is molded into the module case 10 with a connection terminal 62a (see FIG. 3) on the motor M side and a portion where the lead frame 40 is joined exposed from the module case 10. The connection terminal 62a is connected to the motor M.

[0041] 4, the control terminal 70 is molded to the beam portion 12 of the module case 10 in an L-shaped bent state. One end of the control terminal 70 protrudes upward from the module case 10. This one end of the control terminal 70 is inserted into a through-hole provided in the board unit 3b and connected to the board unit 3b. The other end of the control terminal 70 is arranged so as to be exposed upward at the opening 11a.

[0042] 6 is a schematic plan view of the power module 3a in which one power device 20 is enlarged. As shown in this figure, a plurality of control terminals 70 are provided for one semiconductor element 22, which will be described later. A bonding wire 80 is connected to each of these control terminals 70, connecting the semiconductor element 22 and the control terminal 70. In other words, the power conversion device 1 of this embodiment includes a plurality of bonding wires 80 (wires) that connect the semiconductor element 22 and the control terminal 70. As shown in FIG. 4, the interior of the opening 11a is sealed with a sealing material 90.

[0043] 4 , each power device 20 includes a mounting substrate 21 and a semiconductor element 22. The mounting substrate 21 is a substrate on which the semiconductor element 22 is mounted. The mounting substrate 21 includes a sheet-like insulating substrate 23, a front conductor layer 24 (first conductor layer) provided on the front surface (one surface) of the insulating substrate 23, and a back conductor layer 25 (second conductor layer) provided on the back surface (the other surface) of the insulating substrate 23.

[0044] The insulating substrate 23 is formed of an insulating material such as ceramics and is formed in a sheet shape. A front conductor layer 24 is formed on the surface of the insulating substrate 23 (the surface on the semiconductor element 22 side). This front conductor layer 24 is a metal layer that is electrically connected to the semiconductor element 22 and forms part of the conductive circuit. In other words, the front conductor layer 24 is a conductor layer on which the semiconductor element 22 is mounted.

[0045] 7 is a plan view of the power device 20. As shown in this figure, two semiconductor elements 22 are mounted on the front-side conductor layer 24. The front-side conductor layer 24 is divided into sections for each semiconductor element 22. The portion of the front-side conductor layer 24 on which one semiconductor element 22 is mounted is referred to as the first portion 24a, and the portion of the front-side conductor layer 24 on which the other semiconductor element 22 is mounted is referred to as the second portion 24b. The first portion 24a and the second portion 24b are provided on the insulating substrate 23 and spaced apart from each other.

[0046] FIG. 8 is a perspective view of the mounting substrate 21. As shown in this figure, the first portion 24a has a recess 24c for accommodating the semiconductor element 22. For example, the depth of the recess 24c is greater than the thickness of the semiconductor element 22. One of the semiconductor elements 22 is provided on the bottom surface of the recess 24c. The recess 24c has a rectangular portion 24c1 and bulging portions 24c2 bulging outward from the rectangular portion 24c1. The bulging portions 24c2 bulge outward from both ends of the rectangular portion 24c1 in the short direction of the surrounding wall 11. These bulging portions 24c2 are smaller than the rectangular portion 24c1 to prevent the semiconductor element 22 placed in the rectangular portion 24c1 from entering the bulging portions. The bulging portions 24c2 are used to expel air bubbles generated in the solder or the like from between the power device 20 and the semiconductor element 22 during the reflow process described below.

[0047] 8, the first portion 24a of the front conductor layer 24 has a plurality of protrusions 24a1 protruding from the bottom surface of the recess 24c. These protrusions 24a1 are intended to form a gap between the sheet solder before heating and the bottom surface of the recess 24c in the reflow process described below. By providing such a gap, it becomes easier for the reducing gas to come into contact with a wide area of ​​the underside of the sheet solder.

[0048] The second portion 24b also has a recess 24d for accommodating the semiconductor element 22. For example, the depth of the recess 24d is greater than the thickness of the semiconductor element 22. The other semiconductor element 22 is provided on the bottom surface of the recess 24d. The recess 24d has a rectangular portion 24d1 and bulging portions 24d2 bulging outward from the rectangular portion 24d1. The bulging portions 24d2 are provided so as to bulge outward from both ends of the rectangular portion 24d1 in the short direction of the surrounding wall portion 11. These bulging portions 24d2 are formed smaller than the rectangular portion 24d1 so as to prevent the semiconductor element 22 placed in the rectangular portion 24d1 from entering the bulging portions. The bulging portions 24d2 are provided to expel air bubbles generated in the solder or the like from between the power device 20 and the semiconductor element 22 during the reflow process described below.

[0049] 8, the second portion 24b of the front-side conductor layer 24 has a plurality of protrusions 24b1 protruding from the bottom surfaces of the recess 24d and the lead frame bonding portion 24e. These protrusions 24b1 are intended to form a gap between the sheet solder before heating and the bottom surface of the recess 24d in the reflow process described below. Providing such a gap makes it easier for the reducing gas to come into contact with a wide area of ​​the underside of the sheet solder.

[0050] Additionally, the second portion 24b is provided with a recessed lead frame bonding portion 24e for bonding the lead frame 40. The lead frame bonding portion 24e has a rectangular portion 24e1 and bulging portions 24e2 that bulge outward from the rectangular portion 24e1. The bulging portions 24e2 are provided so as to bulge outward from both ends of the rectangular portion 24e1 in the short direction of the surrounding wall portion 11. These bulging portions 24e2 are formed smaller than the rectangular portion 24e1 so as to prevent the semiconductor element 22 disposed in the rectangular portion 24e1 from entering the bulging portions. The bulging portions 24e2 are provided to expel air bubbles generated in the solder or the like from between the power device 20 and the lead frame 40 during the reflow process described below.

[0051] 8, the second portion 24b of the top conductor layer 24 has a plurality of protrusions 24b1 protruding from the bottom surface of the lead frame joint 24e. These protrusions 24b1 are intended to form a gap between the sheet solder before heating and the bottom surface of the lead frame joint 24e in the reflow process described below. Providing such a gap makes it easier for the reducing gas to come into contact with a wide area of ​​the underside of the sheet solder.

[0052] In this embodiment, the first portion 24a and the second portion 24b are arranged in the extension direction of the beam portion 12 of the module case 10. As shown in FIG. 8 and other figures, the first portion 24a has an extension portion 24a2 extending from a main portion on which the semiconductor element 22 is mounted. The extension portion 24a2 extends from the main portion so as to pass beside the second portion 24b, and its tip reaches the opposite side of the second portion 24b. In this embodiment, a joint piece 61b of a bus bar 61 connected to the positive electrode of battery B is joined to the tip of the extension portion 24a2. The extension portion 24a2 is arranged below the beam portion 12. In other words, the beam portion 12 is arranged to overlap the extension portion 24a2 when viewed from the stacking direction.

[0053] Returning to FIG. 4 , a back-side conductor layer 25 is formed on the other surface of the insulating substrate 23 (the surface opposite the semiconductor element 22). This back-side conductor layer 25 forms part of a heat transfer path that transfers heat conducted from the semiconductor element 22 and the like to the heat sink 30. The surface of this back-side conductor layer 25 opposite the insulating substrate 23 is the mounting surface when the power device 20 is mounted on the heat sink 30. This mounting surface is bonded to the heat sink 30 via solder 100, as shown in FIG. 4 . Note that in this embodiment, the mounting substrate 21 includes the back-side conductor layer 25. However, the mounting substrate 21 does not necessarily need to include the back-side conductor layer 25. In this case, the insulating substrate 23 is bonded to the heat sink 30.

[0054] The backside conductor layer 25 also has a plurality of protrusions 25a that protrude downward from the mounting surface. These protrusions 25a are intended to form a gap between the sheet solder and the mounting surface before heating in the reflow process described below. By providing such a gap, it becomes easier for the reducing gas to come into contact with a wide area of ​​the upper surface of the sheet solder.

[0055] The semiconductor element 22 is mounted on the front conductor layer 24, for example. The number of semiconductor elements 22 mounted on the front conductor layer 24 is not limited. Such semiconductor elements 22 can be formed using a silicon (Si) semiconductor. Alternatively, the semiconductor element 22 can be formed using a wide-gap semiconductor such as a silicon carbide (SiC) semiconductor or a gallium nitride (GaN) semiconductor.

[0056] As described above, the semiconductor element 22 includes a mounting substrate bonding electrode 22a provided on the front conductor layer 24 side. The mounting substrate bonding electrode 22a is bonded to the front conductor layer 24 via solder 100. In this embodiment, the mounting substrate bonding electrode 22a is formed in a rectangular shape. As described above, the semiconductor element 22 also includes a lead frame bonding electrode 22b provided on the lead frame 40 side. The lead frame bonding electrode 22b is bonded to the lead frame 40 via solder 100.

[0057] Each power device 20 is housed in the opening 11a of the module case 10 while being placed on a heat sink 30. The heat sink 30 supports the module case 10 and the power devices 20. The heat sink 30 also absorbs heat from the power devices 20 to cool them. The heat sink 30 is fixed to the central plate 2a so that the bottom surface thereof is exposed to a flow path provided in the central plate 2a, for example. The heat sink 30 may also have a plurality of fins formed on the bottom surface.

[0058] The lead frame 40 is joined to the power device 20 and the bus bar 60. The lead frame 40 is joined to the lead frame joining electrode 22b of the semiconductor element 22 via solder 100. The lead frame 40 is also joined to the bus bar 60 via solder 100. Furthermore, the end of the bus bar 60 joined to the lead frame joining electrode 22b of the semiconductor element 22 mounted on the first portion 24a is joined to the lead frame joining portion 24e via solder 100.

[0059] 6 , the power module 3 a of this embodiment includes, as the lead frame 40, a lead frame 41 that connects the bus bar 62 to the semiconductor element 22 mounted on the first portion 24 a, and a lead frame 42 that connects the bus bar 61 to the semiconductor element 22 mounted on the second portion 24 b. These lead frames 41 and 42 are arranged linearly along the extension direction of the beam portion 12.

[0060] 9 is a flowchart showing a part of the manufacturing process of the power module 3a of this embodiment. As shown in this figure, the manufacturing process of the power module 3a of this embodiment includes a mounting substrate arrangement step S1, a case arrangement step S2, a semiconductor element arrangement step S3, a lead frame arrangement step S4, a reflow step S5, and a wire bonding step S6, which are performed in this order.

[0061] The mounting board placement step S1 is a step of placing the mounting board 21 on the surface 30a of the heat sink 30 via sheet solder. Note that the sheet solder may be melted before the case placement step S2 to bond the mounting board 21 to the heat sink 30 in advance.

[0062] The case placement step S2 is a step of placing the module case 10 that surrounds the mounting substrate 21 relative to the heat sink 30. In the case placement step S2, the module case 10 is adhered to the heat sink 30 via an adhesive 50.

[0063] The semiconductor element placement step S3 is a step of placing the semiconductor element 22 on the mounting substrate 21. In the semiconductor element placement step S3, sheet solder is placed on the mounting substrate 21. Furthermore, in the semiconductor element placement step S3, the semiconductor element 22 is placed on the mounting substrate 21 via the sheet solder.

[0064] The lead frame placement step S4 is a step of placing the lead frame 40. Here, the lead frame 40 is placed so as to be in contact with the semiconductor element 22, the bus bar 60, and the lead frame joint portion 24e via sheet solder, bar solder, or the like.

[0065] The reflow process S5 is a process in which the sheet solder or the like is melted by heating and then hardened to bond the mounting substrate 21, the semiconductor element 22, the heat sink 30, and the lead frame 40 to one another. The wire bonding process S6 is a process in which the control terminals 70 and the semiconductor element 22 are connected via bonding wires 80.

[0066] Thereafter, the power module 3a of this embodiment is manufactured by performing necessary operations such as forming the sealing material 90. Furthermore, the power conversion device 1 is manufactured using such a power module 3a.

[0067] The power module 3a of this embodiment as described above includes a heat sink 30, power devices 20, and a module case 10. A plurality of power devices 20 are provided and arranged on a surface 30a of the heat sink 30. The module case 10 is fixed to the heat sink 30 and encloses the plurality of power devices 20. The module case 10 also includes a surrounding wall 11 and beams 12. The surrounding wall 11 has an opening 11a that accommodates the plurality of power devices 20 when viewed from the stacking direction of the heat sink 30 and the power devices 20. The beams 12 are supported by the surrounding wall 11 so as to straddle the opening 11a and form a gap between them and the heat sink 30. The beams 12 also include control terminals 70 that are connected to the power devices 20 via bonding wires 80. The beams 12 are also arranged so that at least a portion of the beams 12 overlaps the power devices 20 when viewed from the stacking direction.

[0068] According to the power module 3a of this embodiment, the module case 10 includes a surrounding wall 11 that surrounds the multiple power devices 20 and a beam 12 that spans the opening 11a of the surrounding wall 11. Furthermore, the beam 12 houses the control terminal 70 that is connected to the power device 20 via a bonding wire 80. Therefore, the power module 3a of this embodiment does not require the surrounding wall 11 to house the control terminal 70, allowing the module case 10 to be compact in plan view. Furthermore, because a gap is provided between the beam 12 and the heat sink 30, the multiple power devices 20 can be densely arranged without interfering with the beam 12. Therefore, the power module 3a of this embodiment reduces the space required for installing the multiple power devices 20, allowing the module case 10 to be compact in plan view.

[0069] Furthermore, in the power module 3a of this embodiment, the module case 10 is provided with a beam 12 that straddles the opening 11a of the surrounding wall 11. This improves the rigidity of the module case 10 compared to a case where the beam 12 is not provided. Therefore, the power module 3a of this embodiment includes a module case 10 with high strength.

[0070] In the power module 3a of this embodiment, the power device 20 includes a plurality of semiconductor elements 22 and a mounting substrate 21 on which the plurality of semiconductor elements 22 are mounted. The mounting substrate 21 includes an insulating substrate 23, a top conductor layer 24, and a bottom conductor layer 25. The insulating substrate 23 is formed in a sheet shape. The top conductor layer 24 is provided on one surface (front surface) of the insulating substrate 23, and the semiconductor elements 22 are mounted thereon. The bottom conductor layer 25 is provided on the other surface (back surface) of the insulating substrate 23. The top conductor layer 24 includes a first portion 24a and a second portion 24b that are aligned in the extension direction of the beam portion 12 and spaced apart from each other when viewed from the stacking direction. The first portion 24a includes an extension portion 24a2 that extends along the extension direction of the beam portion 12 and is located to the side of the second portion 24b. The beam portion 12 is arranged to overlap the extension portion 24a2 when viewed from the stacking direction.

[0071] In the power module 3a of this embodiment, the beam portion 12 is arranged to overlap the extension portion 24a2 of the first portion 24a. The extension portion 24a2 is a portion where the semiconductor element 22 is not normally mounted. By positioning the beam portion 12 above the extension portion 24a2, the semiconductor element 22 is prevented from being hidden by the beam portion 12. This makes it possible to easily connect the control terminal 70 included in the beam portion 12 to the semiconductor element 22 using a bonding wire 80.

[0072] In this embodiment, two semiconductor elements 22 are provided on the mounting substrate 21. These semiconductor elements 22 are arranged along the longitudinal direction of the mounting substrate 21 and are arranged so as to overlap when viewed from the lateral direction of the mounting substrate 21. Therefore, a region in the lateral direction of the mounting substrate 21 in which no semiconductor elements 22 are mounted is generated continuously along the longitudinal direction of the mounting substrate 21. At least a portion of the extending portion 24a2 is formed in such a region in which no semiconductor elements 22 are mounted. In other words, by arranging the semiconductor elements 22 so as to overlap when viewed from the lateral direction as described above, the extending portion 24a2 can be made into a portion in which no semiconductor elements 22 are mounted.

[0073] In the power module 3a of this embodiment, a gap is provided between the beam portion 12 and the heat sink 30 as described above. Therefore, as shown in Fig. 4, two power devices 20 can be arranged so that portions of them overlap each other when viewed from above below one beam portion 12. In other words, the extension portion 24a2 of one power device 20 and a portion of another power device 20 can be positioned below one beam portion 12. Therefore, the power devices 20 can be arranged closer to each other, and the power module 3a can be made smaller.

[0074] The power module 3a of this embodiment also includes a lead frame 41 that connects the bus bar 60 enclosed in the surrounding wall portion 11 to the semiconductor element 22 mounted on the first portion 24a, and a lead frame 42 that connects the bus bar 60 to the semiconductor element 22 mounted on the second portion 24b. The lead frames 41 and 42 are arranged linearly along the extension direction of the beam portion 12.

[0075] According to the power module 3a of this embodiment, the lead frames 41 and 42 can be prevented from interfering with the adjacent power devices 20. Therefore, the power module 3a of this embodiment can densely arrange a plurality of power devices 20. Therefore, the power module 3a of this embodiment can make the module case 10 more compact.

[0076] In the power module 3a of this embodiment, the bus bar 61 has a joining piece 61b soldered to the first portion 24a. The module case 10 has a holding portion 13 that holds the joining piece 61b. The power module 3a of this embodiment is further provided with a through hole 14 that passes through the joining piece 61b and the holding portion 13.

[0077] According to the power module 3a of this embodiment, a solder bar can be inserted into the through-hole 14. In the reflow process S5, the solder bar inserted into the through-hole 14 is melted and melted, whereby the joining piece 61b and the power device 20 can be easily joined together.

[0078] In the power module 3a of this embodiment, the top conductor layer 24 has recesses (recesses 24c and 24d) on the bottom surface thereof for mounting the semiconductor element 22. The power device 20 of this embodiment can prevent the semiconductor element 22 from moving significantly during the reflow process S5.

[0079] Furthermore, in the power module 3a of this embodiment, the front conductor layer 24 has protrusions (protrusions 24a1 and 24b1) that protrude from the bottom surfaces of the recesses (recesses 24c and 24d). In the power module 3a of this embodiment, a gap is formed between the sheet solder before heating and the bottom surface of the recess 24c in the reflow process S5. This makes it easy to bring the reducing gas into contact with a wide area of ​​the underside of the sheet solder.

[0080] In addition, in the power module 3a of this embodiment, the recess 24c has a rectangular portion 24c1 that is rectangular when viewed in the stacking direction and a bulging portion 24c2 that bulges outward from the rectangular portion 24c1. Therefore, in the reflow process S5, bubbles generated inside the solder or the like can be discharged from between the power device 20 and the semiconductor element 22 through the bulging portion 24c2, thereby preventing voids from being generated in the solder 100.

[0081] In addition, in the power module 3a of this embodiment, the recess 24d has a rectangular portion 24d1 that is rectangular when viewed from the stacking direction and a bulging portion 24d2 that bulges outward from the rectangular portion 24d1. Therefore, in the reflow process S5, bubbles generated inside the solder or the like can be discharged from between the power device 20 and the semiconductor element 22 through the bulging portion 24d2, thereby preventing voids from being generated in the solder 100.

[0082] Furthermore, in the power module 3a of this embodiment, the beam portion 12 contains a plurality of control terminals 70 arranged along the extension direction. In the power module 3a of this embodiment, a single beam portion 12 contains a plurality of control terminals 70. This allows the module case 10 to be made smaller than when a beam portion 12 is provided for each control terminal 70.

[0083] In the power module 3a of this embodiment, the beam portions 12 are arranged with a gap in the stacking direction from the power devices 20. In the power module 3a of this embodiment, it is possible to prevent heat from accumulating between the beam portions 12 and the power devices 20, resulting in a temperature rise.

[0084] Furthermore, the power module 3a of this embodiment is provided with a plurality of beam portions 12. Therefore, the strength of the module case 10 can be improved compared to when a single beam portion 12 is provided.

[0085] The power conversion device 1 of this embodiment also includes a power module 3 a, and performs power conversion using the power module 3 a. The power conversion device 1 of this embodiment includes the power module 3 a. Therefore, the power conversion device 1 of this embodiment can be made smaller.

[0086] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above-described embodiments. The shapes and combinations of the components shown in the above-described embodiments are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0087] For example, in the above embodiment, a configuration has been described in which a gap is provided between the beam portion 12 and the power device 20. However, the present invention is not limited to this, and the beam portion 12 may be in contact with the power device 20.

[0088] The above embodiment can also be described as follows, for example:

[0089] (Supplementary Note 1) A semiconductor device comprising: a base member; a plurality of semiconductor substrates arranged on a surface of the base member; and a case fixed to the base member and enclosing the plurality of semiconductor substrates, wherein the case comprises: a surrounding wall portion having an opening for accommodating the plurality of semiconductor substrates when viewed from a stacking direction of the base member and the semiconductor substrates; and a beam portion supported by the surrounding wall portion so as to straddle the opening and form a gap between the base member and the case; and the beam portion contains a control terminal connected to the semiconductor substrate via a wire, and is arranged so that at least a portion of the beam portion overlaps the semiconductor substrate when viewed from the stacking direction.

[0090] (Supplementary Note 2) The semiconductor device according to Supplementary Note 1, characterized in that the semiconductor substrate comprises: a plurality of semiconductor elements; and a mounting substrate on which the plurality of semiconductor elements are mounted; the mounting substrate comprises: a sheet-like insulating base material; and a first conductor layer provided on one surface of the insulating base material and on which the semiconductor elements are mounted; the first conductor layer has a first portion and a second portion that are arranged in the extension direction of the beam portion as viewed from the stacking direction and are arranged with a gap between them; the first portion has an extension portion that extends along the extension direction of the beam portion and is located to the side of the second portion; and the beam portion is arranged so as to overlap the extension portion as viewed from the stacking direction.

[0091] (Appendix 3) A semiconductor device according to Appendix 2, characterized in that it comprises: a first connecting conductor that connects a conductive member contained in the surrounding wall portion to the semiconductor element mounted in the first portion; and a second connecting conductor that connects the conductive member to the semiconductor element mounted in the second portion, wherein the first connecting conductor and the second connecting conductor are arranged in a straight line along the extension direction.

[0092] (Appendix 4) The semiconductor device according to appendix 3, characterized in that the conductive member has a joint portion that is solder-joined to the first portion, the case has a holding portion that holds the joint portion, and a through hole that passes through the joint portion and the holding portion is provided.

[0093] (Supplementary Note 5) The semiconductor device according to any one of Supplementary Notes 2 to 4, wherein the first conductor layer has a recess in a bottom surface thereof in which the semiconductor element is mounted.

[0094] (Supplementary Note 6) The semiconductor device according to Supplementary Note 5, wherein the first conductor layer has a protrusion protruding from the bottom surface of the recess.

[0095] (Supplementary Note 7) The semiconductor device according to Supplementary Note 5 or 6, wherein the recess has a rectangular portion that is rectangular when viewed from the stacking direction, and a bulging portion that bulges outward from the rectangular portion.

[0096] (Supplementary Note 8) The semiconductor device according to any one of Supplementary Notes 2 to 7, wherein the beam portion includes a plurality of control terminals arranged along the extending direction.

[0097] (Supplementary Note 9) The semiconductor device according to any one of Supplementary Notes 1 to 8, wherein the beam portion is disposed with a gap from the semiconductor substrate in the stacking direction.

[0098] (Supplementary Note 10) The semiconductor device according to any one of Supplementary Notes 1 to 9, wherein a plurality of the beam portions are provided.

[0099] (Supplementary Note 11) A power conversion device comprising the semiconductor device according to any one of Supplementary Notes 1 to 10, and performing power conversion using the semiconductor device.

[0100] DESCRIPTION OF SYMBOLS 1 Power conversion device 3a Power module (semiconductor device) 10 Module case (case) 11 Surrounding wall portion 11a Opening 12 Beam portion 13 Holding portion 14 Through hole 20 Power device (semiconductor substrate) 21 Mounting substrate 22 Semiconductor element 23 Insulating base material 24 Front conductor layer (first conductor layer) 24a First portion 24a1 Protrusion 24a2 Extension portion 24b Second portion 24b1 Protrusion 24c Recess 24c1 Rectangular portion 24c2 Bulging portion 24d Recess 24d1 Rectangular portion 24d2 Bulging portion 24e Lead frame bonding portion 24e1 Rectangular portion 24e2 Bulging portion 25 Back conductor layer (second conductor layer) 25a Protrusion 30 Heat sink (base member) 30a Front surface 40 Lead frame 41 Lead frame (first connecting conductor) 42 Lead frame (second connecting conductor) 50 Adhesive material 60 Bus bar (conductive member) 61 Bus bar 61a Connection terminal 61b Joining piece (joint portion) 62 Bus bar 62a Connection terminal 70 Control terminal 80 Bonding wire (wire) 90 Sealing material 100 Solder

Claims

1. A semiconductor device comprising: a base member; a plurality of semiconductor substrates arranged on a surface of the base member; and a case fixed to the base member and enclosing the plurality of semiconductor substrates, wherein the case comprises: a surrounding wall portion having an opening for accommodating the plurality of semiconductor substrates when viewed in a stacking direction of the base member and the semiconductor substrates; and a beam portion supported by the surrounding wall portion so as to straddle the opening and form a gap between the base member and the case; and the beam portion contains a control terminal connected to the semiconductor substrate via a wire, and is arranged so that at least a portion of the beam portion overlaps the semiconductor substrate when viewed in the stacking direction.

2. The semiconductor device according to claim 1, characterized in that the semiconductor substrate comprises a plurality of semiconductor elements and a mounting board on which the plurality of semiconductor elements are mounted, the mounting board comprises a sheet-like insulating base material and a first conductor layer provided on one side of the insulating base material and on which the semiconductor elements are mounted, the first conductor layer has a first portion and a second portion that are arranged in the extension direction of the beam portion when viewed from the stacking direction and are disposed with a gap between them, the first portion has an extension portion that extends along the extension direction of the beam portion and is located to the side of the second portion, and the beam portion is disposed so as to overlap the extension portion when viewed from the stacking direction.

3. The semiconductor device according to claim 2, further comprising: a first connecting conductor that connects a conductive member contained in the surrounding wall portion to the semiconductor element mounted in the first portion; and a second connecting conductor that connects the conductive member to the semiconductor element mounted in the second portion, the first connecting conductor and the second connecting conductor being arranged in a straight line along the extension direction.

4. The semiconductor device according to claim 3, characterized in that the conductive member has a joint portion that is solder-joined to the first portion, the case has a holding portion that holds the joint portion, and a through hole is provided that passes through the joint portion and the holding portion.

5. A semiconductor device according to any one of claims 2 to 4, characterized in that the first conductor layer has a recess in the bottom surface in which the semiconductor element is mounted.

6. A semiconductor device according to claim 5, wherein said first conductor layer has a protrusion protruding from said bottom surface of said recess.

7. The semiconductor device according to claim 5, wherein said recess has a rectangular portion having a rectangular shape when viewed from the stacking direction, and a bulging portion bulging outward from said rectangular portion.

8. The semiconductor device according to any one of claims 2 to 4, characterized in that the beam portion includes a plurality of control terminals arranged along the extension direction.

9. The semiconductor device according to any one of claims 1 to 4, characterized in that the beam portion is disposed with a gap from the semiconductor substrate in the stacking direction.

10. The semiconductor device according to any one of claims 1 to 4, characterized in that a plurality of said beam portions are provided.

11. A power conversion device comprising the semiconductor device according to any one of claims 1 to 4, and performing power conversion using said semiconductor device.

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