Semiconductor Modules

Abstract

Provided is a semiconductor module that can suppress surge voltage even when a switching element is turned on and off at high speed by setting an electrode structure with low inductance and can be miniaturized. The semiconductor module comprises: a semiconductor element; a substrate on which the semiconductor element is mounted; a heat sink on which the substrate is mounted; a resin case that houses the substrate and the semiconductor element; and first and second main current electrodes through which a main current of the semiconductor element flows, wherein one end of each of the first and second main current electrodes is bonded to a circuit pattern on the substrate, and the other end of each of the first and second main current electrodes is inserted into the side wall of the resin case in a manner that protrudes to the outside of the resin case, and each of the first and second main current electrodes has an overlapping portion that overlaps in parallel with each other at least partially at a distance, and each of the first and second main current electrodes has an inclined portion provided between an external protruding portion that protrudes to the outside of the resin case and an internal protruding portion that protrudes to the inside of the resin case.

Description

Technical Field

[0001] The present invention relates to a semiconductor module, and in particular, to a semiconductor module having an electrode structure capable of reducing inductance. Background Art

[0002] Conventionally, as an electrode structure for suppressing a surge voltage on a power supply line of a semiconductor module, the invention disclosed in Patent Document 1 has been proposed. Figure 1 The disclosed structure. Figure 1 In the invention, two power terminals composed of plate-shaped conductors are arranged close to each other through an insulating sheet with a thickness of 0.5 mm to 1.5 mm, and the currents flowing through the two power terminals are antiparallel to each other. Therefore, the inductance parasitically formed in the path formed by the two power terminals and the semiconductor element is reduced, and the surge voltage is also reduced.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 6-21323

[0004] The electrode structure of Patent Document 1 is a parallel plate electrode having a plurality of right-angled portions. Therefore, the current path length becomes longer and the electrode inductance becomes larger. The semiconductor element may be destroyed by the surge voltage generated during the high-speed switching operation of the semiconductor element.

[0005] In addition, due to the large number of right-angled portions, it is difficult to process the electrode, and thick conductive materials cannot be used. The increase in current density in the electrode increases the inductance. Here, there is a relationship between the surge voltage (ΔV) generated when the switching element is switched off and the inductance (Ls): ΔV = Ls × di / dt. The allowable surge voltage is fixed, so the inductance and the current change rate (di / dt) are inversely related. When the inductance (Ls) is large, in order to reduce the current change rate (di / dt), it is necessary to reduce the switching speed or the current value. When high-speed switching is sought, the allowable current value will be reduced, and the current capacity will be limited. In order to reduce the inductance, it is effective to reduce the current density of the electrode, but when the electrode cannot be made thicker, the electrode width will increase, and there is a problem that miniaturization of the semiconductor module becomes difficult. Summary of the invention

[0006] The present invention is made to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor module which can suppress surge voltage even during high-speed switching operations of a switching element by setting an electrode structure with low inductance and can be miniaturized.

[0007] The semiconductor module of the present invention comprises: a semiconductor element; a substrate on which the semiconductor element is mounted; a heat sink on which the substrate is mounted; a resin case that accommodates the substrate and the semiconductor element; and first and second main current electrodes through which the main current of the semiconductor element flows, wherein one end of each of the first and second main current electrodes is joined to a circuit pattern on the substrate, and the other end of each of the first and second main current electrodes is inserted into the side wall of the resin case in a manner protruding to the outside of the resin case, and each of the first and second main current electrodes has at least a portion of an overlapping portion that overlaps in parallel with each other at a distance, and each has an inclined portion provided between an external protruding portion that protrudes to the outside of the resin case and an internal protruding portion that protrudes to the inside of the resin case.

[0008] Effects of the Invention

[0009] According to the semiconductor module of the present invention, the first and second main current electrodes each have an overlapping portion that overlaps in parallel with each other at least partially at a distance, so that the self-inductance can be reduced by mutual inductance. In addition, the first and second main current electrodes each have an inclined portion, so that the electrode path can be shortened and the inductance can be further reduced. By reducing the inductance, when the semiconductor element is a switching element, the surge voltage can be suppressed even during high-speed on-off operations. In addition, by having an inclined portion, the processability is good, and thick electrode materials can be used, so the current density of the electrode is reduced, and the miniaturization of the semiconductor module can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a plan view showing the structure of the semiconductor module according to the first embodiment.

[0011] Figure 2 It is a cross-sectional view showing the structure of the semiconductor module according to the first embodiment.

[0012] Figure 3 It is a perspective view showing the high potential electrode and the low potential electrode in a state of being incorporated in a resin case.

[0013] Figure 4 It is a perspective view showing a high potential electrode.

[0014] Figure 5 It is a perspective view showing a low potential electrode.

[0015] Figure 6 It is a perspective view showing the output electrode in a state of being incorporated in a resin case.

[0016] Figure 7 This is a schematic diagram for explaining the process of bending the electrode when no inclined portion is provided.

[0017] Figure 8 This is a schematic diagram for explaining the process of bending the electrode when an inclined portion is provided.

[0018] Fig. 9 It is a cross-sectional view showing the structure of a semiconductor module according to the second embodiment.

[0019] Fig.10 This is a plan view for explaining a method for manufacturing a semiconductor module according to a third embodiment.

[0020] Fig.11 This is a cross-sectional view for explaining a method for manufacturing a semiconductor module according to the third embodiment.

[0021] Fig.12 It is a cross-sectional view showing the structure of a semiconductor module according to a fourth embodiment. DETAILED DESCRIPTION

[0022] <Implementation method 1>

[0023] Figure 1 1 is a plan view showing the structure of the semiconductor module 100 according to the first embodiment, and the upper surface of the resin case CS is omitted to clearly show the internal structure. Figure 2 is a cross-sectional view showing the structure of the semiconductor module 100. Figure 1 Sagittal section view at line AA in the figure.

[0024] like Figure 1 and Figure 2 As shown, in the semiconductor module 100, the upper surface of the base plate BS functioning as a heat sink is bonded to the conductor film CF on the lower surface of the insulating substrate IS via a bonding material SD1 such as solder. A circuit pattern PT is provided on the upper surface of the insulating substrate IS, and a plurality of semiconductor elements SE such as power transistor chips and diode chips are bonded to the circuit pattern PT via a bonding material SD2 such as solder.

[0025] The insulating substrate IS is made of resin or ceramics, and the base plate BS is made of a material having excellent heat dissipation properties such as aluminum (Al) or copper (Cu).

[0026] The insulating substrate IS mounted on the base plate BS is accommodated in a box-shaped resin case CS mounted on the base plate BS and sealed with resin or the like, but illustration is omitted for convenience.

[0027] exist Figure 1 , Figure 2 In FIG. 1 , a transistor constituting an inverter such as an IGBT (Insulated Gate Bipolar Transistor) is shown as an example of a semiconductor element SE. Figure 1In the embodiment, a plurality of high potential side transistors QH mounted on a circuit pattern PTH connected to a high potential electrode HT having a high potential and a plurality of low potential side transistors QL mounted on a circuit pattern PTL connected to a low potential electrode LT having a low potential are electrically connected to the circuit pattern PT via a wire WR. In addition, the electrical circuit provided on the insulating substrate IS is not limited to an inverter.

[0028] like Figure 1 As shown, the circuit pattern PT is provided to extend from between the circuit pattern PTH and the circuit pattern PTL which are elongated in a plan view to the end of the insulating substrate IS which is opposite to the side where the high potential electrode HT and the low potential electrode LT are provided in a plan view, and is connected to the output electrode OT at the end of the insulating substrate IS. The high potential electrode HT and the low potential electrode LT can be respectively referred to as the first main current electrode and the second main current electrode through which the main current of the semiconductor element SE flows.

[0029] like Figure 1 As shown in FIG. 1 , the high potential electrode HT and the low potential electrode LT are incorporated into a side wall of the resin case CS in a rectangular shape in a plan view in the longitudinal direction, one end of which is exposed at the upper surface of the terminal block TB1 protruding from the side wall to the outside, and the other end is connected to the circuit pattern PTH and the circuit pattern PTL. The high potential electrode HT and the low potential electrode LT are arranged in a manner that they are partially parallel to each other and overlap, so that the self-inductance of the semiconductor module 100 can be reduced by mutual inductance. In addition, as shown in FIG. Figure 2 As shown, the high potential electrode HT and the low potential electrode LT have an inclined portion SL bent at an angle less than 90° relative to the horizontal direction parallel to the base plate BS, thereby shortening the electrode length compared to the case of right-angle bending, and further reducing the inductance of the semiconductor module 100.

[0030] In addition, if Figure 1 As shown, the output electrode OT is incorporated into the other side wall in the longitudinal direction of the resin case CS, one end of which is exposed on the upper surface of the terminal block TB2 protruding outward from the side wall, and the other end is joined to the circuit pattern PT.

[0031] like Figure 2 As shown, the joint portion JP of the high potential electrode HT and the low potential electrode LT that is joined to the circuit pattern PTH and the circuit pattern PTL is the end surface of the other end of the high potential electrode HT and the low potential electrode LT, and is joined by a joining material such as solder. In addition, the front end of each electrode can be bent, and the back surface can be joined to the circuit pattern by a joining material. Similarly, for the output electrode OT, the joint portion JP that is joined to the circuit pattern PT can be the end surface or the back surface.

[0032] Figure 3The slant portion SL is provided between the external protrusions of the high potential electrode HT and the low potential electrode LT protruding from the side wall of the resin case CS to the outside and exposed on the upper surface of the terminal block TB1 and the internal protrusions protruding from the side wall of the resin case CS to the inside, and is provided inside the side wall of the resin case CS.

[0033] Figure 4 and Figure 5 The perspective views each separately show the high potential electrode HT and the low potential electrode LT, and the hatched portions are overlapping portions. By further increasing the overlapping portion, the self-inductance of the semiconductor module 100 can be further reduced.

[0034] Figure 6 1 is a perspective view showing the output electrode OT in a state of being installed in the resin case CS, wherein the resin case CS is omitted. The inclined portion SL is provided between the external protruding portion of the output electrode OT protruding from the side wall of the resin case CS to the outside and exposed at the upper surface of the terminal block TB2 and the internal protruding portion protruding from the side wall of the resin case CS to the inside, and is provided inside the side wall of the resin case CS.

[0035] Figure 7 It is a schematic diagram for explaining the bending processing process of the electrode when no inclined portion is provided, showing the state S1 where the electrode FT is a flat plate, through the state S2 where one end of the electrode FT is bent at a right angle to form the first right-angle portion C1, the state S3 where the electrode FT is bent at a right angle closer to the proximal side than the first right-angle portion C1 to form the second right-angle portion C2, the state S4 where the electrode FT is bent at a right angle closer to the proximal side than the second right-angle portion C2 to form the third right-angle portion C3, and the state S5 where the electrode FT is assembled into the resin shell CS.

[0036] Figure 8 It is a schematic diagram for explaining the bending process of the electrode when an inclined portion is provided, showing a state S1 in which the electrode FT is a flat plate, a state S2 in which one end of the electrode FT is bent at a right angle to form a first right-angle portion C1, a state S13 in which the electrode FT is bent from a horizontal state at an angle less than 90° closer to the proximal end than the first right-angle portion C1 to form a first obtuse-angle portion C11, a state S14 in which the electrode FT is bent from a horizontal state at an angle less than 90° closer to the proximal end than the first obtuse-angle portion C11 to form a second obtuse-angle portion C12, and a state S15 in which the electrode FT is installed in a resin case CS. In addition, Figure 7 and Figure 8 The electrode FT shown corresponds to the high potential electrode HT.

[0037] like Figure 7 As shown in FIG. 1 , when no inclined portion is provided, the electrode is bent at right angles at three locations to form the high potential electrode HT. However, as shown in FIG. Figure 8 As shown, when the inclined portion is provided, in order to form the high potential electrode HT, it is sufficient to be bent at a right angle at one location. Therefore, the processability is good, and thick electrode materials can be used, so the current density of the electrode is reduced, the inductance is reduced, and the semiconductor module 100 can be miniaturized.

[0038] That is, when the electrode is bent at a right angle (90°) by stamping, the required bending stress is proportional to the thickness of the electrode. On the other hand, when the electrode is bent at an angle less than 90°, the required bending stress becomes lower than that of the right angle bending. According to experience, sometimes only about half of the bending stress of the case of bending at 90° is required. Therefore, from the perspective of bending stress, compared with the case of bending at 90°, the electrode thickness can be increased by about 2 times when bent at 45° under the same bending stress.

[0039] The current density is inversely proportional to the cross-sectional area of ​​the electrode, and therefore, when the electrode thickness is doubled, the current density is halved.

[0040] In order to reduce the inductance, it is also important to shorten the current path. When the electrode is bent at a right angle less than 90 degrees, the electrode path becomes shorter, which contributes to the reduction of the inductance.

[0041] The high potential electrode HT, the low potential electrode LT, and the output electrode OT can all be embedded in the resin case CS by insert molding. Insert molding is a manufacturing method that uses a vertical molding machine to insert metal parts such as electrodes into resin parts by injection molding, using a mold divided into an upper mold and a lower mold. The stamping parts such as electrodes are mounted on the lower mold and the mold is closed with the upper mold, and the molten resin is injected into the mold and cooled, thereby forming the resin part.

[0042] According to this method, the resin case CS in which the high potential electrode HT, the low potential electrode LT, and the output electrode OT are incorporated can be obtained by a single insert molding, so that the manufacturing cost of the semiconductor module 100 can be reduced.

[0043] In addition, since the fixing force of each electrode to the resin case CS can be increased and the distance between electrodes can be shortened, it is effective for reducing the inductance.

[0044] In addition, the high potential electrode HT and the low potential electrode LT can also be Figure 4 and Figure 5In the bent state shown, the electrode is inserted into a slit that penetrates the resin case CS and is incorporated into the resin case CS. The slit is provided so as to have an inclination corresponding to the shape of the inclined portion of the high potential electrode HT and the low potential electrode LT.

[0045] <Implementation method 2>

[0046] In the semiconductor module 100 of the first embodiment described above, the high potential electrode HT, the low potential electrode LT, and the output electrode OT each have the inclined portion SL at one location. However, the inclined portions may be provided at a plurality of locations on each electrode.

[0047] Fig. 9 is a cross-sectional view showing the structure of a semiconductor module 200 according to the second embodiment. Figure 1 The sagittal section at line AA in FIG. Fig. 9 In, for and use Figure 1 and Figure 2 The same components as those of the semiconductor module 100 described above are denoted by the same reference numerals, and repeated description is omitted.

[0048] like Fig. 9 As shown, one end of the high potential electrode HT and the low potential electrode LT of the semiconductor module 200 is exposed on the upper surface of the terminal block TB1 protruding outward from the side wall of the resin case CS, and the other end is connected to the circuit pattern PTH and the circuit pattern PTL.

[0049] The high potential electrode HT and the low potential electrode LT have an inclined portion SL1 provided in the side wall of the resin case CS and an internal inclined portion SL2 provided in the internal protruding portion protruding from the side wall of the resin case CS. The inclined portion SL1 is the same as the inclined portion SL of the high potential electrode HT and the low potential electrode LT of the semiconductor module 100 of the first embodiment, but the inclined portion SL2 is provided near the joint portion JP where the high potential electrode HT and the low potential electrode LT are respectively joined to the circuit pattern PTH and the circuit pattern PTL, and is bent at an angle less than 90° relative to the horizontal direction parallel to the base plate BS. Therefore, the contact area between the joint portion JP and the circuit pattern becomes larger.

[0050] In addition, if Fig. 9 As shown in FIG. 1 , the output electrode OT also has an inclined portion SL1 provided in the side wall of the resin case CS and an internal inclined portion SL2 provided in a portion protruding from the side wall of the resin case CS to the inside. The inclined portion SL2 is provided near the joint portion JP where the output electrode OT is joined to the circuit pattern PT, and is bent at an angle less than 90° relative to the horizontal direction parallel to the base plate BS. Therefore, the contact area between the joint portion JP and the circuit pattern becomes larger.

[0051] In this way, at the high potential electrode HT and the low potential electrode LT, all the bent portions are not right angles but are bent at an angle less than 90°, so that the processability of the electrode is further improved, and thicker electrodes can be used, thereby further reducing the inductance and realizing the miniaturization of the semiconductor module 200.

[0052] <Implementation method 3>

[0053] Fig.10 and Fig.11 1 and 2 are a plan view and a cross-sectional view respectively illustrating a method for manufacturing a semiconductor module 300 according to Embodiment 3. Fig.10 and Fig.11 In, for and use Figure 1 and Figure 2 The same components as those of the semiconductor module 100 described above are denoted by the same reference numerals, and repeated description is omitted.

[0054] like Fig.10 and Fig.11 As described above, the semiconductor module 300 has a housing CS that is completed in the following manner, that is, the side wall of the housing CS in which the high potential electrode HT and the low potential electrode LT are housed is formed independently of the other parts of the housing CS, and the separate side wall CSX is joined to the other parts of the housing CS by an adhesive, etc. Therefore, there is a seam between the side wall CSX and the other parts.

[0055] The closer the distance between the high potential electrode HT and the low potential electrode LT is, the lower the inductance can be. However, if the electrodes are conductive, they no longer function as a semiconductor module. Therefore, the processing accuracy of the distance between the electrodes is important. Therefore, by forming the side wall portion of the housing CS in which the high potential electrode HT and the low potential electrode LT are incorporated as independent entities through insert molding, the processing accuracy of the mold for insert molding can be improved, and the portion can be formed with high accuracy, thereby shortening the distance between the electrodes and improving the effect of reducing the inductance.

[0056] In addition, Fig.10 and Fig.11 , the output electrode OT is shown as an integrated structure with other parts of the shell CS, but it is not limited to this. It can also be a structure in which the side wall part of the shell CS in which the output electrode OT is installed is also set as an independent body, and the shell CS is completed by joining it with other parts of the shell CS in the same way as the side wall part of the shell CS in which the high potential electrode HT and the low potential electrode LT are installed. Figure 6As described above, the shape of the output electrode OT is also complex. Therefore, by forming the side wall portion of the shell CS in which the output electrode OT is housed as an independent individual through insert molding, the processing accuracy of the insert molding mold can be improved, the portion can be formed with high precision, and the cost of mold manufacturing can also be reduced.

[0057] <Modification>

[0058] When the side wall portion of the case CS in which the high potential electrode HT and the low potential electrode LT having a large potential difference are embedded is formed independently, it can be formed by a resin different from that of other portions of the case CS. For example, by setting the resin in which the high potential electrode HT and the low potential electrode LT having a large potential difference are embedded to a resin with a high CTI (Comparative Tracking Index), it is less likely to cause creeping discharge, and thus even if the distance between the electrodes is set to be narrower, insulation can be ensured, and the effect of reducing inductance can be further improved by arranging the high potential electrode HT and the low potential electrode LT closer together.

[0059] More specifically, a resin having a CTI of 600 or more (600 ≤ CTI) can be used for the side wall portion of the case CS in which the high potential electrode HT and the low potential electrode LT are housed, and a resin having a CTI of 175 or more and less than 400 (175 ≤ CTI < 400) can be used for the other portions of the case CS. By using a resin having a CTI of 600 or more, the distance between electrodes can be set to about half compared to the case of using a resin having a CTI of 175 or more and less than 400.

[0060] <Implementation method 4>

[0061] Fig.12 is a cross-sectional view showing the structure of a semiconductor module 400 according to a fourth embodiment. Figure 1 The sagittal section at line AA in FIG. Fig.12 In, for and use Figure 1 and Figure 2 The same components as those of the semiconductor module 100 described above are denoted by the same reference numerals, and repeated description is omitted.

[0062] like Fig.12 As shown in FIG. 1 , the semiconductor module 400 includes an insulator IF between the high potential electrode HT and the low potential electrode LT. By providing the insulator IF between the electrodes, conduction between the electrodes can be suppressed.

[0063] The insulator IF can use a gel-like insulating material or a sheet-like insulating material such as insulating paper. When using a gel-like insulating material, the high potential electrode HT and the low potential electrode LT are fixed by filling the gel-like insulating material between the electrodes and then hardening it, thereby facilitating subsequent handling.

[0064] When a sheet-like insulating material with stable processing accuracy, such as insulating paper, is used as the insulator IF, the distance between the electrodes can be reduced to the thickness of the insulating material by sandwiching and fixing the sheet-like insulating material formed in a manner that matches the shape between two electrodes, thereby achieving a further reduction in the inductance of the semiconductor module 400.

[0065] Furthermore, since the dielectric breakdown initiation voltage per unit length of the insulating paper is about three times higher than that of the gel-like insulating material, the distance between electrodes can be reduced to about 1 / 3 compared to the case of using the gel-like insulating material.

[0066] <Applicable semiconductor devices>

[0067] The semiconductor modules 100 to 400 of the first to fourth embodiments described above do not mention the constituent material of the semiconductor element SE. However, the constituent material of the semiconductor element SE may be a silicon (Si) semiconductor or a silicon carbide (SiC) semiconductor.

[0068] The silicon carbide semiconductor element, i.e., the switching element, which is composed of SiC semiconductor, has low switching loss and can perform high-speed switching operations, but the surge voltage increases during high-speed switching, and the semiconductor element may be destroyed by the surge voltage. However, in the semiconductor modules 100 to 400 of the first to fourth embodiments, the inductance can be reduced, and thus the surge voltage during high-speed switching can be suppressed.

[0069] In addition, the switching element formed of SiC semiconductor has low power loss and high heat resistance. Therefore, when a power module having a cooling unit is configured, the heat dissipation fins of the heat sink can be miniaturized, thereby achieving further miniaturization of the semiconductor module.

[0070] In addition, the switching element composed of SiC semiconductor is suitable for high-frequency switching operation. Therefore, when applied to an inverter circuit that requires high frequency, the reactor, capacitor, etc. connected to the inverter circuit can be miniaturized by increasing the switching frequency.

[0071] In addition, the semiconductor element SE can also be formed of a wide bandgap semiconductor other than the SiC semiconductor.

[0072] As wide bandgap semiconductors other than SiC semiconductors, there are gallium nitride materials and diamond. Switching elements composed of wide bandgap semiconductors can also be used in high voltage areas where unipolar operation is difficult for Si semiconductors, and can significantly reduce the switching loss generated during the switching operation. Therefore, it is possible to achieve a significant reduction in power loss.

[0073] In addition, the present invention can freely combine the various embodiments within the scope of the present invention, or can appropriately modify or omit the various embodiments.

Claims

1. A semiconductor module comprising: Semiconductor components; a substrate on which the semiconductor element is mounted; a heat sink mounted with the substrate; a resin housing that accommodates the substrate and the semiconductor element; and first and second main current electrodes, through which the main current of the semiconductor element flows, One end of each of the first and second main current electrodes is joined to the circuit pattern on the substrate, and the other end of each is inserted into the side wall of the resin case in a manner protruding to the outside of the resin case. The first and second main current electrodes each have at least a portion of overlapping portions that overlap in parallel with each other at a distance, and each have an inclined portion provided between an external protruding portion protruding to the outside of the resin case and an internal protruding portion protruding to the inside of the resin case.

2. The semiconductor module according to claim 1, wherein: The first and second main current electrodes have inner inclined portions provided on the respective inner protruding portions.

3. The semiconductor module according to claim 1, wherein: As for the resin housing, The side wall in which the first and second main current electrodes are mounted is provided independently of other parts of the resin housing. A seam is provided between the side wall and the other parts.

4. The semiconductor module according to claim 3, wherein: The side wall of the resin case is formed of a resin having a higher relative tracking index than the other portions.

5. The semiconductor module according to claim 4, wherein: The relative tracking index of the resin of the sidewall is greater than or equal to 600.

6. The semiconductor module according to claim 1, wherein: The invention further includes an insulator provided between the electrodes at the overlapping portion of the first and second main current electrodes.

7. The semiconductor module according to claim 6, wherein: The insulating material is formed of insulating material or insulating paper obtained by hardening a gel-like insulating material.

8. The semiconductor module according to claim 1, wherein: The first and second main current electrodes are incorporated into the side wall by insert molding.

9. The semiconductor module according to claim 1, wherein: The semiconductor element is a silicon carbide semiconductor element.

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