Semiconductor unit

Abstract

To provide a technique capable of securing insulation between a screw for attaching a cooler and a horizontal terminal of a semiconductor module, and also capable of downsizing a semiconductor unit.SOLUTION: The cooling unit 2 is attached to the lower surface of the base plate 3, and the cooling unit 2 is attached to the lower surface of the base plate 3 by screwing the plurality of screws 4 into the plurality of screw hole 3a portions of the base plate 3, respectively, so that the cooling unit 2 is attached to the lower surface of the base plate 3 via the plurality of screw hole 3a portions of the base plate 3. A counterbore portion 3a having a depth smaller than the thickness of the base plate 3 is provided at a portion on the upper surface side of the base plate 3 in at least one screw hole 3a among the plurality of screw hole 3b.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a semiconductor unit. [Background technology]

[0002] In general, semiconductor modules such as an IGBT (Insulated Gate Bipolar Transistor) module, an intelligent power module (IPM), or a transfer-molded power module (T-PM) are connected to a cooler via a base plate to form a semiconductor unit in order to dissipate heat generated due to power loss (see, for example, Patent Document 1).

[0003] When attaching the cooler to the base plate using screws, it is necessary to consider heat dissipation, the torque required when tightening the screws, the insulation distance between the screw that serves as the reference potential and the terminal that has high-voltage potential, and miniaturization of the semiconductor unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 181198 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with conventional technology, it was difficult to achieve both the insulation between the screws for attaching the cooler and the horizontal terminals of the semiconductor module and the miniaturization of the semiconductor unit, as these are contradictory goals.

[0006] Therefore, an object of the present disclosure is to provide a technology that can ensure insulation between the screws for attaching the cooler and the horizontal terminals of the semiconductor module while also achieving miniaturization of the semiconductor unit. [Means for solving the problem]

[0007] The semiconductor unit according to the present disclosure comprises a semiconductor device, a semiconductor module having a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface, a base plate to whose upper surface the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface, a cooler attached to the lower surface of the base plate for cooling the semiconductor module, and a plurality of screws that are respectively screwed into the plurality of screw holes in the base plate to attach the cooler to the lower surface of the base plate, and a countersunk portion having a depth smaller than the thickness of the base plate is provided in the upper surface side portion of at least one of the plurality of screw holes. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to ensure insulation between the screws for attaching the cooler and the horizontal terminals of the semiconductor module while also achieving miniaturization of the semiconductor unit. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a configuration of a semiconductor unit according to a first embodiment. [Figure 2] 1 is a top view of a semiconductor unit according to a first embodiment. [Figure 3] 4 is a cross-sectional view of a screw fastening point between the base plate and the cooler and the surrounding area in the first embodiment. FIG. [Figure 4] 10 is a cross-sectional view of the screw fastening point between the base plate and the cooler and the surrounding area when no counterbore is provided in the screw hole. FIG. [Figure 5] FIG. 10 is a top view of a semiconductor unit according to a second embodiment. [Figure 6]FIG. 10 is a top view of a semiconductor unit according to a third embodiment. [Figure 7] FIG. 10 is a top view of a semiconductor unit according to a fourth embodiment. [Figure 8] 13 is a cross-sectional view of a screw fastening point between a base plate and a cooler and the surrounding area in the fifth embodiment. FIG. [Figure 9] FIG. 13 is a top view of a semiconductor unit according to a sixth embodiment. [Figure 10] FIG. 13 is a top view of a semiconductor unit according to a seventh embodiment. [Figure 11] 13 is a cross-sectional view of the screw fastening point between the base plate and the cooler and the surrounding area in the eighth embodiment. FIG. [Figure 12] FIG. 23 is a top view of a semiconductor unit according to a tenth embodiment. [Figure 13] FIG. 23 is a top view of a semiconductor unit according to an eleventh embodiment. [Figure 14] FIG. 10 is a top view of a semiconductor unit in which the number of screw holes on the P, N electrode side and the number of screw holes on the AC electrode side are the same. [Figure 15] FIG. 23 is a top view of a semiconductor unit according to a twelfth embodiment. [Figure 16] FIG. 23 is a top view of a semiconductor unit according to a thirteenth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] <First Embodiment> The first embodiment will be described below with reference to the drawings. Fig. 1 is a perspective view showing the configuration of a semiconductor unit according to the first embodiment. Fig. 2 is a top view of the semiconductor unit according to the first embodiment. Fig. 2 also shows a state in which a screw 4 has been removed.

[0011] As shown in FIGS. 1 and 2, the semiconductor unit includes six semiconductor modules 1, a base plate 3, a cooler 2, and nine screws 4. The semiconductor modules 1 are IGBT (Insulated Gate Bipolar Transistor) modules, intelligent power modules (IPMs), or transfer-molded power modules (T-PMs). The semiconductor modules 1 include a semiconductor device (not shown) built into the semiconductor module 1, a plurality of horizontal terminals 7 protruding horizontally from the side surfaces of the semiconductor module 1, and a plurality of control terminals 8 protruding from the side surfaces of the semiconductor module 1 and having their tips bent upward. Bus bars 10 and the like are connected to the horizontal terminals 7.

[0012] 2, in top view, the tips of the horizontal terminals 7 are located closer to the inner periphery than the outer periphery of the base plate 3. The number of semiconductor modules 1 is not limited to six, but may be one or more.

[0013] The semiconductor device may be an IGBT or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The material constituting the semiconductor device is, for example, silicon (Si). Note that the material constituting the semiconductor device is not limited to silicon, and may be, for example, a wide bandgap semiconductor material such as silicon carbide (SiC), gallium nitride (GaN), or diamond (C). The number of semiconductor devices may be one or more.

[0014] The horizontal terminals 7 are electrically connected to the semiconductor device inside the semiconductor module 1. The control terminals 8 are electrically connected to the semiconductor device inside the semiconductor module 1, and transmit control signals input from the outside to the semiconductor device.

[0015] The base plate 3 is formed in a rectangular shape. Six semiconductor modules 1 are arranged side by side on the upper surface of the base plate 3 in the long side direction. At least one pair of two semiconductor modules 1, each having horizontal terminals 7 provided at positions that are line-symmetrical with respect to the long side direction of the base plate 3, is arranged. In FIG. 2, three pairs of two semiconductor modules 1 are arranged, but this is not limited to this. Each semiconductor module 1 is joined to the upper surface of the base plate 3 by solder (not shown). A plurality of (for example, nine) screw holes 3a are formed on the outer periphery of the base plate 3, penetrating from the upper surface to the lower surface. The number of screw holes 3a is not limited to nine.

[0016] The cooler 2 is attached to the underside of the base plate 3 and cools the semiconductor module 1. Nine screw holes 2a (see FIG. 3) are provided in the cooler 2 at positions facing the nine screw holes 3a of the base plate 3, and communicate with the nine screw holes 3a, respectively. Nine screws 4 are screwed into the nine screw holes 3a of the base plate 3 and the nine screw holes 2a of the cooler 2, thereby attaching the cooler 2 to the underside of the base plate 3. The screws 4 are made of a conductive metal. Hereinafter, the screws 4 will also be referred to as conductive screws 4. The cooler 2 is of a water-cooled type, and the inside of the cooler 2 is filled with a cooling medium (not shown) for cooling the semiconductor module 1.

[0017] Next, a description will be given of the structure of the screw holes 3a, which is a feature of embodiment 1. Fig. 3 is a cross-sectional view of the screw fastening points between the base plate 3 and the cooler 2 and the surrounding area in embodiment 1.

[0018] 2 and 3, nine screw holes 3a are provided along the outer periphery of the base plate 3. Specifically, the nine screw holes 3a are provided only at the four corners of the base plate 3 and on the long sides of the outer periphery of the base plate 3. Furthermore, the nine screw holes 3a are provided on the outer periphery of the area where the intervals between adjacent horizontal terminals 7 of adjacent semiconductor modules 1 are larger, rather than in the area where the intervals between adjacent horizontal terminals 7 are smaller.

[0019] At least one of the nine screw holes 3a has a counterbore 3b on the upper surface side of the base plate 3, the counterbore 3b having a depth smaller than the thickness of the base plate 3. In the first embodiment, all of the screw holes 3a are provided with the counterbore 3b. The counterbore 3b is formed with a diameter larger than the diameter of the head 4a of the screw 4 and a depth greater than the height of the head 4a so that the head 4a can be accommodated therein. The counterbore 3b is also formed with a diameter larger than that of the screw hole 3a in the base plate 3. The depth d1 of the counterbore 3b is 1 mm or less, and the depth d2 of the screw hole 3a in the base plate 3 is 2 mm or more.

[0020] Next, the effects of the first embodiment will be described in comparison with the case where the counterbore portion 3b is not provided in the screw hole 3a shown in Fig. 4. Fig. 4 is a cross-sectional view of the screw fastening point between the base plate 3 and the cooler 2 and the surrounding area when the counterbore portion 3b is not provided in the screw hole 3a.

[0021] 4, the head 4a of the screw 4 is located above the upper surface of the base plate 3, and when the semiconductor unit is made smaller, the distance r2 between the screw 4 and the horizontal terminal 7 becomes shorter, making it difficult to ensure insulation between the screw 4 and the horizontal terminal 7. Therefore, it is difficult to simultaneously ensure insulation between the screw 4 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1 and to make the semiconductor unit smaller.

[0022] In contrast, in the first embodiment, the semiconductor unit includes a semiconductor module 1 having a semiconductor device and horizontal terminals 7 electrically connected to the semiconductor device and protruding horizontally from the side surface, a base plate 3 to whose upper surface the semiconductor module 1 is joined and which has a plurality of screw holes 3a penetrating from the upper surface to the lower surface, a cooler 2 attached to the lower surface of the base plate 3 and cooling the semiconductor module 1, and a plurality of screws 4 that are screwed into the plurality of screw holes 3a in the base plate 3, respectively, to attach the cooler 2 to the lower surface of the base plate 3. At least one of the plurality of screw holes 3a is provided on the upper surface side of the base plate 3 with a counterbore 3b having a depth smaller than the thickness of the base plate 3.

[0023] 3, head 4a of screw 4 is accommodated in counterbore portion 3b, so distance r1 between screw 4 and horizontal terminal 7 is longer than distance r2 in the case of FIG. 4. This makes it possible to ensure insulation between screw 4 and horizontal terminal 7. As a result, it is possible to both ensure insulation between screw 4 for attaching cooler 2 and horizontal terminal 7 of semiconductor module 1 and reduce the size of the semiconductor unit.

[0024] Furthermore, when viewed from above, the tip of the horizontal terminal 7 is located closer to the inner periphery than the outer periphery of the base plate 3, so that when multiple semiconductor units are arranged side by side, the semiconductor units can be arranged close to each other.

[0025] Furthermore, when the semiconductor module 1 is a transfer mold type power module, the effect of improving the insulation between the screws 4 for attaching the cooler 2 and the horizontal terminals 7 of the semiconductor module 1 is even greater.

[0026] <Embodiment 2> Next, a second embodiment will be described. Fig. 5 is a top view of a semiconductor unit according to the second embodiment. Fig. 5 also shows a state in which the screws 4 have been removed. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0027] 5, in the second embodiment, in a top view, the counterbore portions 3b are located closer to the outer periphery of the base plate 3 than the tips of the horizontal terminals 7, and are provided so as not to overlap with the horizontal terminals 7. In other words, the counterbore portions 3b are provided between the outer edge line of the base plate 3 and the tip lines of the horizontal terminals 7. The outer edge line of the base plate 3 is a line that follows the outer edge of the base plate 3, and the tip lines of the horizontal terminals 7 are a line that connects the tips of multiple horizontal terminals 7.

[0028] In the second embodiment, the countersunk portion 3b and the horizontal terminal 7 do not overlap when viewed from above, so that when the cooler 2 is attached to the base plate 3, the screws 4 can be easily fastened.

[0029] <Third Embodiment> Next, a third embodiment will be described. Fig. 6 is a top view of a semiconductor unit according to the third embodiment. Fig. 6 also shows a state in which the screws 4 have been removed. In the third embodiment, the same components as those described in the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0030] As shown in Fig. 6, in the third embodiment, at least one of the nine screw holes 3a does not have a counterbore 3b. In Fig. 6, two of the central screw holes 3a provided along the long side of the base plate 3 do not have a counterbore 3b.

[0031] In embodiment 3, by providing a screw hole 3a without a countersunk portion 3b, the tightening torque of the screw 4 can be made stronger compared to a screw hole 3a with a countersunk portion 3b, thereby making it possible to increase the mounting strength of the cooler 2.

[0032] <Fourth Embodiment> Next, a fourth embodiment will be described. Fig. 7 is a top view of a semiconductor unit according to the fourth embodiment. Fig. 7 also shows a state in which the screws 4 have been removed. In the fourth embodiment, the same components as those described in the first to third embodiments are designated by the same reference numerals, and description thereof will be omitted.

[0033] 7, in the fourth embodiment, at least one of the screw holes 3a provided at the four corners of the base plate 3 does not have a counterbore portion 3b. In FIG. 7, two of the screw holes 3a provided at the four corners of the base plate 3 do not have a counterbore portion 3b, but the present invention is not limited to this, and one or three or more of the screw holes 3a provided at the four corners of the base plate 3 may not have a counterbore portion 3b.

[0034] In the fourth embodiment, similarly to the third embodiment, it is possible to increase the mounting strength of the cooler 2.

[0035] <Fifth Embodiment> Next, a fifth embodiment will be described. Fig. 8 is a cross-sectional view of the screw fastening points between the base plate 3 and the cooler 2 in the fifth embodiment and the surrounding area. In the fifth embodiment, the same components as those described in the first to fourth embodiments are given the same reference numerals and the description thereof will be omitted.

[0036] As shown in Fig. 8, in the fifth embodiment, the counterbore portion 3b has a tapered shape that narrows in a direction from the upper surface to the lower surface of the base plate 3. The screw hole 3a in the base plate 3 and the screw hole 2a in the cooler 2 also have a tapered shape that narrows in a direction from the top to the bottom. The depth d1 of the counterbore portion 3b is 1 mm or less, and the depth d2 of the screw hole 3a in the base plate 3 is 2 mm or more. Note that the dotted lines in Fig. 8 indicate the areas that would be removed in a normal counterbore process.

[0037] Furthermore, the head 4a and the shank 4b of the screw 4 each have a tapered shape that narrows downward.

[0038] In the fifth embodiment, the amount of the base plate 3 that needs to be machined can be reduced compared to normal countersinking, which makes it possible to increase the strength of the base plate 3. Furthermore, when the screw 4 is screwed into the screw hole 3a, it is possible to easily fit the countersunk portion 3b into the head 4a of the screw 4 while suppressing misalignment between the two.

[0039] <Sixth Embodiment> Next, a sixth embodiment will be described. Fig. 9 is a top view of a semiconductor unit according to the sixth embodiment. In the sixth embodiment, the same components as those described in the first to fifth embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0040] In embodiments 1 to 5, by providing a countersunk portion 3b in the screw hole 3a, it is possible to ensure insulation between the screw 4 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1 while also achieving miniaturization of the semiconductor unit.

[0041] 9, in the sixth embodiment, a non-conductive screw 14 is employed as a screw to be screwed into the screw hole 3a without providing a counterbore portion 3b in the screw hole 3a. Specifically, at least one screw among the plurality of screws is a non-conductive screw 14. The non-conductive screw 14 is formed of, for example, an insulating resin.

[0042] In FIG. 9, the screws that are screwed into the screw holes 3a at the four corners of the base plate 3 are conductive screws 4, and the other screws are non-conductive screws 14.

[0043] In the sixth embodiment, insulation can be ensured regardless of the distance between the non-conductive screw 14 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1, and therefore, it is possible to ensure insulation between the non-conductive screw 14 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1 and to reduce the size of the semiconductor unit at the same time without providing the countersunk portion 3b.

[0044] <Seventh Embodiment> Next, a seventh embodiment will be described. Fig. 10 is a top view of a semiconductor unit according to the seventh embodiment. In the seventh embodiment, the same components as those described in the first to sixth embodiments are denoted by the same reference numerals, and the description thereof will be omitted.

[0045] 10, in the seventh embodiment, in contrast to the configuration of the sixth embodiment, a conductive screw 4 is screwed into at least one of the screw holes 3a provided in the four corners of the base plate 3. In FIG. 10, the conductive screws 4 are screwed into two of the screw holes 3a provided in the four corners of the base plate 3.

[0046] In the seventh embodiment, by replacing some of the screws at the four corners of the base plate 3, which are subject to a large tightening torque load, with conductive screws 4, it is possible to increase the mounting strength of the cooler 2.

[0047] <Embodiment 8> Next, an eighth embodiment will be described. Fig. 11 is a cross-sectional view of the screw fastening points between the base plate 3 and the cooler 2 in the eighth embodiment and the surrounding area. In the eighth embodiment, the same components as those described in the first to seventh embodiments are given the same reference numerals and the description thereof will be omitted.

[0048] In the sixth and seventh embodiments, the counterbore portion 3b is not provided in the screw hole 3a, and the non-conductive screw 14 is used as the screw to be screwed into the screw hole 3a.

[0049] In contrast to this, in the eighth embodiment, instead of the non-conductive screw 14, the head 4a of at least one screw 4 out of the plurality of screws 4 is covered with insulating resin 15, as shown in FIG.

[0050] In the eighth embodiment, as in the sixth embodiment, insulation can be ensured regardless of the distance between the screw 4 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1, and therefore, without providing the countersunk portion 3b, it is possible to ensure insulation between the screw 4 for attaching the cooler 2 and the horizontal terminal 7 of the semiconductor module 1 and to miniaturize the semiconductor unit at the same time.

[0051] <Ninth Embodiment> Next, a description will be given of embodiment 9. In embodiment 9, the same components as those described in embodiments 1 to 8 are denoted by the same reference numerals, and the description thereof will be omitted.

[0052] Although not shown, in embodiment 9, a screw 4 whose head 4a is coated with insulating resin 15 is screwed into at least one of the screw holes 3a provided at the four corners of the base plate 3.

[0053] In the ninth embodiment, by using screws 4 that are partially covered with insulating resin 15 for the screws at the four corners of base plate 3, the process and cost required for covering with insulating resin 15 can be reduced.

[0054] <Tenth Embodiment> Next, a tenth embodiment will be described. Fig. 12 is a top view of a semiconductor unit according to the tenth embodiment. Fig. 12 also shows a state in which the screws 4 have been removed. In the tenth embodiment, the same components as those described in the first to ninth embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0055] In the first to ninth embodiments, the nine screw holes 3a are provided only at the four corners of the base plate 3 and on the long sides of the outer periphery of the base plate 3.

[0056] 12, in the tenth embodiment, seven screw holes 3a are provided only on the long side of the outer periphery of the base plate 3. Note that while Fig. 12 shows a case where counterbore portions 3b are provided in the screw holes 3a of the first to fifth embodiments, the tenth embodiment can also be adopted in the configurations of the sixth to ninth embodiments.

[0057] In embodiment 10, the screw holes 3a are not provided on the short side of the outer periphery of the base plate 3, so that it is possible to reduce the size of the base plate 3 in the short side direction compared to when the screw holes 3a are provided on the short side of the outer periphery of the base plate 3, thereby enabling further miniaturization of the semiconductor unit.

[0058] <Embodiment 11> Next, an eleventh embodiment will be described. Fig. 13 is a top view of a semiconductor unit according to the eleventh embodiment. Fig. 14 is a top view of a semiconductor unit in which the number of screw holes 3a is the same on the P, N electrode side and the AC electrode side. Figs. 13 and 14 also show a state in which the screws 4 have been removed. In the eleventh embodiment, the same components as those described in the first to tenth embodiments are designated by the same reference numerals, and description thereof will be omitted.

[0059] As shown in FIG. 13 , in the eleventh embodiment, the horizontal terminals 7 include a first horizontal terminal 17 connected to a P electrode or an N electrode on one long side of the base plate 3, and a second horizontal terminal 27 connected to an AC electrode on the other long side of the base plate 3. In a top view, the first horizontal terminal 17 and the second horizontal terminal 27 protrude from diagonally opposite side surfaces of the semiconductor module 1. Note that in FIG. 13 , the P, N electrode side refers to the side connected to the P electrode or the N electrode, and the AC electrode side refers to the side connected to the AC electrode. Furthermore, the number of screw holes 3 a differs between one long side and the other long side of the outer periphery of the base plate 3. That is, the number of screw holes 3 a differs between the P, N electrode side and the AC electrode side of the base plate 3. The P, N electrode side is the upper side in FIG. 13 , and the AC electrode side is the lower side in FIG. 13 . Although FIG. 13 shows the case where the counterbore portion 3b is provided in the screw hole 3a of the first to fifth embodiments, the configuration of the eleventh embodiment can also be adopted for the configurations of the sixth to ninth embodiments.

[0060] In the eleventh embodiment, compared to the case where the number of screw holes 3a is the same on the P, N electrode side and the AC electrode side as shown in FIG. 14, the arrangement of the screw holes 3a can be made more flexible.

[0061] <Embodiment 12> Next, a twelfth embodiment will be described. Fig. 15 is a top view of a semiconductor unit according to the twelfth embodiment. Fig. 15 also shows a state in which the screws 4 have been removed. In the twelfth embodiment, the same components as those described in the first to eleventh embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0062] As shown in Fig. 15, in the twelfth embodiment, in top view, portions of the nine screw holes 3a are located closer to the inner periphery of the base plate 3 than the tips of the horizontal terminals 7. In Fig. 13, portions of two screw holes 3a are located closer to the inner periphery of the base plate 3 than the tips of the horizontal terminals 7, but the number of screw holes 3a whose portions are located closer to the inner periphery of the base plate 3 than the tips of the horizontal terminals 7 is not limited to two. Note that Fig. 15 shows a case where the counterbore portions 3b are provided in the screw holes 3a of the first to fifth embodiments, but the twelfth embodiment can also be adopted for the configurations of the sixth to ninth embodiments.

[0063] In the twelfth embodiment, the plurality of screw holes 3a are provided so that a portion thereof is located closer to the inner periphery of the base plate 3 than the tip of the horizontal terminal 7, thereby making it possible to reduce the size of the semiconductor unit.

[0064] <Embodiment 13> Next, a thirteenth embodiment will be described. Fig. 16 is a top view of a semiconductor unit according to the thirteenth embodiment. Fig. 16 also shows a state in which the screws 4 have been removed. In the thirteenth embodiment, the same components as those described in the first to twelfth embodiments are denoted by the same reference numerals, and description thereof will be omitted.

[0065] In the first to twelfth embodiments, the nine screw holes 3a are provided on the outer periphery of the region where the interval between adjacent horizontal terminals 7 of adjacent semiconductor modules 1 is larger.

[0066] In contrast, in the thirteenth embodiment, as shown in Fig. 16, the horizontal terminals 7 and the plurality of screw holes 3a have overlapping regions when viewed from above. In Fig. 16, six of the eight screw holes 3a overlap the horizontal terminals 7, and the remaining two screw holes 3a overlap the control terminals 8 when viewed from above, but the number of screw holes 3a overlapping the horizontal terminals 7 when viewed from above is not limited to this. Note that Fig. 16 shows a case where the counterbore portions 3b are provided in the screw holes 3a of the first to fifth embodiments, but the thirteenth embodiment can also be adopted for the configurations of the sixth to ninth embodiments.

[0067] In the thirteenth embodiment, a plurality of screw holes 3a are provided so as to overlap with the horizontal terminals 7 in top view, thereby enabling miniaturization of the semiconductor unit.

[0068] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

[0069] Various aspects of the present disclosure are summarized below as appendices.

[0070] (Appendix 1) a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; A semiconductor unit, wherein a countersunk portion having a depth smaller than the thickness of the base plate is provided in a portion of the upper surface side of the base plate in at least one of the plurality of screw holes.

[0071] (Appendix 2) 2. The semiconductor unit according to claim 1, wherein, in a top view, a tip of the horizontal terminal is located more inward than an outer edge of the base plate.

[0072] (Appendix 3) 3. The semiconductor unit according to claim 1, wherein, in a top view, the recessed portion is located closer to the outer periphery of the base plate than the tip of the horizontal terminal and does not overlap with the horizontal terminal.

[0073] (Appendix 4) 4. The semiconductor unit according to claim 1, wherein at least one of the plurality of screw holes is not provided with the counterbore portion.

[0074] (Appendix 5) the plurality of screw holes include screw holes provided at four corners of the base plate, 5. The semiconductor unit according to claim 1, wherein at least one of the screw holes provided at the four corners does not have the counterbore.

[0075] (Appendix 6) 6. The semiconductor unit according to claim 1, wherein the recessed portion has a tapered shape that narrows in a direction from the upper surface to the lower surface of the base plate.

[0076] (Appendix 7) a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; At least one of the plurality of screws is a non-conductive screw.

[0077] (Appendix 8) the plurality of screw holes include screw holes provided at four corners of the base plate, 8. The semiconductor unit according to claim 7, wherein a conductive screw is screwed into at least one of the screw holes provided at the four corners.

[0078] (Appendix 9) a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; A semiconductor unit, wherein a head of at least one of the plurality of screws is coated with an insulating resin.

[0079] (Appendix 10) the plurality of screw holes include screw holes provided at four corners of the base plate, The semiconductor unit described in Appendix 9, wherein the screw, the head of which is coated with the insulating resin, is screwed into at least one of the screw holes provided at the four corners.

[0080] (Appendix 11) The base plate is formed in a rectangular shape, 11. The semiconductor unit according to claim 1, wherein the plurality of screw holes are provided only on a long side of the outer periphery of the base plate.

[0081] (Appendix 12) 12. The semiconductor unit according to claim 11, wherein the number of screw holes is different between one of the long sides of the outer periphery of the base plate and the other long side of the outer periphery of the base plate.

[0082] (Appendix 13) a plurality of the semiconductor modules; The semiconductor modules are arranged side by side in the long side direction of the base plate, The semiconductor unit described in Appendix 12, wherein the horizontal terminal includes a first horizontal terminal connected to a P electrode or an N electrode on one of the long sides of the base plate, and a second horizontal terminal connected to an AC electrode on the other long side of the base plate.

[0083] (Appendix 14) at least one pair of the semiconductor modules, each having the horizontal terminals provided at positions that are line-symmetrical with respect to the long side direction of the base plate, are arranged side by side in the long side direction of the base plate; 14. The semiconductor unit according to claim 13, wherein the plurality of screw holes are provided on the outer periphery of an area where the spacing between adjacent horizontal terminals in adjacent semiconductor modules is larger.

[0084] (Appendix 15) 14. The semiconductor unit according to claim 13, wherein, in a top view, the first horizontal terminal and the second horizontal terminal protrude from the diagonally opposite side surfaces of the semiconductor module.

[0085] (Appendix 16) The semiconductor unit of claim 13, wherein, when viewed from above, the semiconductor module further has a control terminal that protrudes from the diagonal side of the semiconductor module, the tip of which is bent upward, and transmits a control signal.

[0086] (Appendix 17) 17. The semiconductor unit according to claim 1, wherein, in a top view, a portion of the plurality of screw holes is located closer to the inner periphery of the base plate than the tip of the horizontal terminal.

[0087] (Appendix 18) 17. The semiconductor unit according to claim 1, wherein the horizontal terminal and the plurality of screw holes have an overlapping region when viewed from above.

[0088] (Appendix 19) The semiconductor unit according to any one of claims 1 to 18, wherein the semiconductor module is a transfer mold type semiconductor module. [Explanation of symbols]

[0089] 1 semiconductor module, 2 cooler, 3 base plate, 3a screw hole, 3b counterbore portion, 4 screw, 4a head, 7 horizontal terminal, 8 control terminal, 15 insulating resin, 17 first horizontal terminal, 27 second horizontal terminal.

Claims

1. a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; A semiconductor unit, wherein a countersunk portion having a depth smaller than a thickness of the base plate is provided in a portion of the upper surface side of the base plate in at least one of the plurality of screw holes.

2. The semiconductor unit according to claim 1 , wherein, in a top view, the tip of the horizontal terminal is located on the inner periphery side of the outer periphery of the base plate.

3. The semiconductor unit according to claim 1 , wherein the counterbore portion is located closer to the outer periphery of the base plate than the tip of the horizontal terminal when viewed from above, and does not overlap the horizontal terminal.

4. The semiconductor unit according to claim 1 , wherein at least one of the plurality of screw holes is not provided with the counterbore portion.

5. the plurality of screw holes include screw holes provided at four corners of the base plate, The semiconductor unit according to claim 1 , wherein at least one of the screw holes provided at the four corners does not have the counterbore.

6. The semiconductor unit according to claim 1 , wherein the recessed portion has a tapered shape tapering in a direction from the upper surface to the lower surface of the base plate.

7. a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; At least one of the plurality of screws is a non-conductive screw.

8. the plurality of screw holes include screw holes provided at four corners of the base plate, The semiconductor unit according to claim 7 , wherein a conductive screw is screwed into at least one of the screw holes provided at the four corners.

9. a semiconductor module having a semiconductor device and a horizontal terminal electrically connected to the semiconductor device and protruding horizontally from a side surface; a base plate having an upper surface to which the semiconductor module is joined and having a plurality of screw holes penetrating from the upper surface to the lower surface; a cooler attached to the lower surface of the base plate and configured to cool the semiconductor module; a plurality of screws that are screwed into the plurality of screw holes of the base plate, respectively, to attach the cooler to the lower surface of the base plate; A semiconductor unit, wherein a head of at least one of the plurality of screws is coated with an insulating resin.

10. the plurality of screw holes include screw holes provided at four corners of the base plate, The semiconductor unit according to claim 9 , wherein the screw, the head of which is covered with the insulating resin, is screwed into at least one of the screw holes provided at the four corners.

11. The base plate is formed in a rectangular shape, 10. The semiconductor unit according to claim 1, wherein the plurality of screw holes are provided only on a long side of the outer periphery of the base plate.

12. The semiconductor unit according to claim 11 , wherein the number of the screw holes on one long side of the outer periphery of the base plate is different from the number of the screw holes on the other long side of the outer periphery of the base plate.

13. a plurality of the semiconductor modules; The semiconductor modules are arranged side by side in the long side direction of the base plate, 13. The semiconductor unit of claim 12, wherein the horizontal terminals include a first horizontal terminal connected to a P electrode or an N electrode on one of the long sides of the base plate, and a second horizontal terminal connected to an AC electrode on the other long side of the base plate.

14. At least one pair of the semiconductor modules, each having the horizontal terminals provided at positions that are line-symmetrical with respect to the long side direction of the base plate, is arranged side by side in the long side direction of the base plate, 14. The semiconductor unit according to claim 13, wherein the plurality of screw holes are provided on an outer periphery of an area where the interval between adjacent horizontal terminals of adjacent semiconductor modules is larger.

15. The semiconductor unit according to claim 13 , wherein the first horizontal terminal and the second horizontal terminal protrude from the diagonally opposite side surfaces of the semiconductor module when viewed from above.

16. 14. The semiconductor unit according to claim 13, wherein, in top view, the semiconductor module further includes a control terminal that projects from the diagonal side surface of the semiconductor module, has a tip that is bent upward, and transmits a control signal.

17. 10. The semiconductor unit according to claim 1, wherein a portion of the plurality of screw holes is located closer to an inner periphery of the base plate than the tips of the horizontal terminals when viewed from above.

18. 10. The semiconductor unit according to claim 1, wherein the horizontal terminal and the plurality of screw holes have an overlapping region when viewed from above.

19. 10. The semiconductor unit according to claim 1, wherein the semiconductor module is a transfer mold type semiconductor module.

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