Semiconductor device

Abstract

This semiconductor device 100 includes: an insulating substrate 5 having a circuit surface 5a; an electrode 2 having one end joined to the circuit surface 5a of the insulating substrate 5; a resin case 3 having a side wall portion 3a surrounding the side of the insulating substrate 5 and an upper wall portion 3b covering above the insulating substrate 5; a cylindrical electrode 1 having a tip portion 1a electrically connected to the other end of the electrode 2 and the inside of the resin case 3, a buried portion 1b buried in the upper wall portion 3b, and a projecting portion 1c projecting upward from the upper wall portion 3b; a coating resin 3c extending from the upper wall portion 3b so as to cover the side surface of the projecting portion 1c of the cylindrical electrode 1; and a screw 11 for fixing a bus bar 9 or a control substrate 10 to the cylindrical electrode 1 by being screwed into a screw hole 1d of the cylindrical electrode 1. The screw hole 1d is provided only in the buried portion 1b of the cylindrical electrode 1, and a screw insertion hole 1e communicating with the screw hole 1d and having a diameter larger than that of the screw hole 1d is provided in the projecting portion 1c of the cylindrical electrode 1.

Description

Semiconductor Devices

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

[0002] Semiconductor devices are used, for example, for controlling motors in electric railway equipment or automotive equipment. In such semiconductor devices, a cylindrical electrode is fixed to a resin case by insert molding, and the electrode is further provided in the resin case. A narrow portion formed at the tip of the cylindrical electrode is inserted into the inside of an annular portion formed on the electrode, thereby electrically connecting the electrode and the cylindrical electrode, thereby enabling miniaturization (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2018-139278

[0004] However, in a structure in which a cylindrical electrode protrudes upward from a resin case and its side surfaces are covered with a thin resin, as in the semiconductor device described in Patent Document 1, when a screw is threaded into a thread groove located above the top surface of the resin case, the tightening torque of the screw is easily transmitted to the resin covering the side surfaces of the cylindrical electrode. As a result, breakage of the resin, which has low strength, becomes a bottleneck, and there is a problem in that the screw cannot be tightened to the cylindrical electrode with sufficient torque.

[0005] Therefore, the present disclosure aims to provide a technology in a semiconductor device that can reduce the screw tightening torque transmitted to the coating resin that covers the side of the portion of the cylindrical electrode that protrudes upward from the resin case.

[0006] The semiconductor device according to the present disclosure comprises an insulating substrate having a circuit surface, an electrode having one end joined to the circuit surface of the insulating substrate, a resin case having a side wall portion surrounding the sides of the insulating substrate and a top wall portion covering the top of the insulating substrate, a cylindrical electrode having a tip portion electrically connected to the other end of the electrode inside the resin case, an embedded portion embedded in the top wall portion, and a protruding portion protruding upward from the top wall portion, a coating resin extending from the top wall portion so as to cover the side of the protruding portion of the cylindrical electrode, and a screw that fixes a bus bar or a control board to the cylindrical electrode by screwing into a screw hole in the cylindrical electrode, wherein the screw hole is provided only in the embedded portion of the cylindrical electrode, and the protruding portion of the cylindrical electrode has a screw insertion hole that is connected to the screw hole and has a larger diameter than the screw hole.

[0007] According to the present disclosure, since the screw holes are provided only in the embedded portion of the cylindrical electrode, most of the tightening torque of the screws can be received by the upper wall portion surrounding the embedded portion of the cylindrical electrode, thereby reducing the tightening torque transmitted to the coating resin.

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

[0009] Fig. 1 is a cross-sectional view of a semiconductor device according to a first embodiment. Fig. 2 is a top view of an electrode and a bottom view of a cylindrical electrode included in a semiconductor device according to a modification of the first embodiment. Fig. 3 is a cross-sectional view showing a connection structure between an electrode and a cylindrical electrode included in a semiconductor device according to a second embodiment. Fig. 4 is a cross-sectional view showing a connection structure between an electrode and a cylindrical electrode included in a semiconductor device according to a third embodiment.

[0010] First Preferred Embodiment A first preferred embodiment will be described below with reference to the drawings. Fig. 1 is a cross-sectional view of a semiconductor device 100 according to the first preferred embodiment.

[0011] As shown in FIG. 1 , the semiconductor device 100 includes a heat sink 4, a plurality of (e.g., two) insulating substrates 5, a semiconductor element 8, a plurality of (e.g., two) electrodes 2 that are Z-shaped in cross section, a resin case 3, a sealing material 12, a plurality of (e.g., two) cylindrical electrodes 1, and a plurality of (e.g., two) screws 11.

[0012] The two insulating substrates 5 are disposed on the heat sink 4 via solder 7. The heat sink 4 and the two insulating substrates 5 may be fixed to each other by means of other means, such as solder 7, such as brazing material or sintered material, or integral molding. The material of the heat sink 4 may be copper (Cu) or aluminum (Al), or a composite material such as silicon carbide-aluminum composite (AlSiC) or silicon carbide-magnesium composite (MgSiC).

[0013] Circuit surfaces 5a are formed on the surfaces of the two insulating substrates 5, and one end of one of the electrodes 2 is bonded to the circuit surface 5a of one of the insulating substrates 5. A semiconductor element 8 is mounted on the circuit surface 5a of the other insulating substrate 5 via solder 7, and one end of the other electrode 2 is bonded to it. The semiconductor element 8 and the two electrodes 2 are electrically connected to the semiconductor element 8 via wires 6 that connect the circuit surfaces 5a to which the two electrodes 2 are bonded, respectively.

[0014] The two insulating substrates 5 are made of ceramic such as aluminum nitride (AlN), silicon nitride (SiN), or alumina (Al2O3).

[0015] The semiconductor element 8 is a switching element such as an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET), or a diode, etc. The material of the semiconductor element 8 may be ordinary silicon (Si), or may be a wide bandgap semiconductor such as silicon carbide (SiC), gallium nitride (GaN), or diamond.

[0016] The method for fixing the semiconductor element 8 to the insulating substrate 5 is not limited to solder 7, but may be bonding using a brazing material, a sintered material, or the like. The wire 6 may be a thin wire made of aluminum (Al) or copper (Cu), or may be a ribbon-shaped wiring or a wiring made by bonding a plate-shaped electrode with solder, or the like. The electrode 2 is bonded to the circuit surface 5a of the insulating substrate 5 by solder bonding, ultrasonic bonding, or laser bonding.

[0017] The resin case 3 is fixed to the peripheral edge of the heat sink 4 and includes a frame-shaped side wall portion 3a that surrounds the sides of the insulating substrate 5, and a plate-shaped upper wall portion 3b that covers the upper side of the insulating substrate 5. The material of the resin case 3 is an engineering plastic such as polyphenylene sulfide (PPS) or polybutylene terephthalate (PBT).

[0018] The cylindrical electrode 1 is a nut that functions as a terminal and is embedded in the upper wall portion 3b while protruding upward from the upper wall portion 3b. The cylindrical electrode 1 is formed in a long, thin cylindrical shape and has an embedded portion 1b embedded in the upper wall portion 3b, a tip portion 1a provided below the embedded portion 1b, and a protruding portion 1c provided above the embedded portion 1b. The tip portion 1a protrudes downward from the upper wall portion 3b and is electrically connected to the other end of the electrode 2 inside the resin case 3.

[0019] Next, the connection between the tip end 1 a of the cylindrical electrode 1 and the other end of the electrode 2 will be described. As shown in FIG. 1 , a circular hole 15 is provided at the other end of the electrode 2. The tip end 1 a of the cylindrical electrode 1 is provided with a cylindrical press-fit portion 16 that can be press-fitted into the hole 15. The diameter of the press-fit portion 16 is smaller than the diameter of the rest of the tip end 1 a. By press-fitting the press-fit portion 16 into the hole 15, the tip end 1 a of the cylindrical electrode 1 is electrically connected to the other end of the electrode 2.

[0020] Returning to the description of each part of the cylindrical electrode 1, the protrusion 1c protrudes upward from the upper wall portion 3b to secure the bus bar 9 or the control board 10, and the amount of upward protrusion of the protrusion 1c is greater than the amount of downward protrusion of the tip portion 1a. The side surfaces of the protrusion 1c are covered with a coating resin 3c extending from the upper wall portion 3b. The material of the coating resin 3c is the same as the material of the upper wall portion 3b. The thickness of the coating resin 3c is also formed to be thinner than the thickness of the upper wall portion 3b. Therefore, the strength of the coating resin 3c covering the side surfaces of the protrusion 1c is lower than the strength of the upper wall portion 3b existing around the embedded portion 1b. The side surfaces of the tip portion 1a are not covered with the coating resin 3c.

[0021] The screws 11 are threaded into the threaded holes 1d of the cylindrical electrode 1 to secure the busbar 9 or the control board 10 to the cylindrical electrode 1. The threaded holes 1d are provided only in the embedded portion 1b, and not in the protruding portion 1c. That is, the threaded holes 1d are provided below the upper surface of the upper wall portion 3b. The protruding portion 1c is also provided with a screw insertion hole 1e that communicates with the threaded hole 1d and has a larger diameter than the threaded hole 1d. That is, the screw insertion hole 1e is provided above the threaded hole 1d.

[0022] The cylindrical electrode 1 is insert-molded into the resin case 3. The connection between the cylindrical electrode 1 and the electrode 2 may be made before or after molding the resin case 3. The material of the cylindrical electrode 1 and the electrode 2 is a metal having low electrical resistance and a predetermined strength, such as iron (Fe), copper (Cu), or aluminum (Al).

[0023] The current (signal) input from the bus bar 9 or the control board 10 is transmitted via the cylindrical electrode 1 to the circuit surface 5a of the insulating substrate 5 joined to the electrode 2 inside the resin case 3, and via the wire 6 to the semiconductor element 8 joined to the circuit surface 5a of the insulating substrate 5.

[0024] The resin case 3 is filled with a sealing material 12. The sealing material 12 is a silicone gel, a resin, or the like.

[0025] In order to ensure the creepage distance (dotted arrow in FIG. 1 ) between the cylindrical electrodes 1 (between terminals) while miniaturizing the semiconductor device 100, the cylindrical electrodes 1 must be positioned so that their protruding portions 1c are located above the upper surface of the upper wall portions 3b, and the side surfaces of the protruding portions 1c must be covered with the coating resin 3c. However, by providing the screw holes 1d of the cylindrical electrodes 1 only in the embedded portions 1b located below the upper surface of the upper wall portions 3b, most of the tightening torque of the screws 11 can be received by the upper wall portions 3b surrounding the embedded portions 1b of the cylindrical electrodes 1. As a result, the tightening torque transmitted to the coating resin 3c, which is weaker than the upper wall portions 3b surrounding the embedded portions 1b, can be reduced, and the screws can be tightened with a sufficient tightening torque without breaking the coating resin 3c.

[0026] Next, a description will be given of the connection between the tip end 1a of the cylindrical electrode 1 and the other end of the electrode 2 in a modification of the first embodiment. Fig. 2 is a top view of the electrode 2 and a bottom view of the cylindrical electrode 1 provided in the semiconductor device 100 according to the modification of the first embodiment. In Fig. 2, the top view of the electrode 2 is shown on the left side, and the bottom view of the cylindrical electrode 1 is shown on the right side.

[0027] When the electrode 2 is formed by punching out a flat plate, a polygonal hole 15 or recess is provided at the other end of the electrode 2, as shown in Fig. 2. A polygonal press-fit portion 16 that can be press-fit into the hole 15 or recess is provided at the tip 1a of the cylindrical electrode 1 formed by forging or the like. Here, the number of corners of the hole 15 or recess and the press-fit portion 16 are the same.

[0028] 1 and 2 , by forming the press-fit portion 16 in a polygonal shape, the tightening torque is received not only by the upper wall portion 3b existing around the embedded portion 1b of the cylindrical electrode 1 but also by the polygonal press-fit portion 16, but because one end of the electrode 2 is joined to the circuit surface 5a of the insulating substrate 5, the tightening torque received by the polygonal press-fit portion 16 is received by the insulating substrate 5. Furthermore, when a resin is used for the sealing material 12, the tightening torque received by the polygonal press-fit portion 16 can be more firmly received by the entire surface of the sealing material 12 that contacts the electrode 2.

[0029] On the other hand, when a soft silicone gel is used as the sealing material 12, the distance between the connection part between the cylindrical electrode 1 and the electrode 2 and the circuit surface 5a of the insulating substrate 5 can be shortened, and the thickness and width of the electrode 2 can be increased to increase the rigidity of the electrode 2, thereby increasing the proportion of the tightening torque that the electrode 2 can withstand.

[0030] Even when resin or soft silicone gel is used as the sealing material 12, the tightening torque transmitted to the coating resin 3c covering the side of the protrusion 1c of the tubular electrode 1 can be reduced, so that the screws can be tightened with a larger tightening torque without breaking the coating resin 3c.

[0031] As described above, it is easier to manufacture the electrode 2 by punching out the electrode 2 from a flat plate. However, when the electrode 2 is forged, a polygonal recess (not shown) may be provided at the tip end 1a of the cylindrical electrode 1, and a polygonal press-fit portion (not shown) that can be press-fitted into the recess may be provided at the other end of the electrode 2. Here, the recess and the press-fit portion have the same number of corners. The above-mentioned effect can also be obtained in this case.

[0032] As described above, the semiconductor device 100 according to the first embodiment includes an insulating substrate 5 having a circuit surface 5a, an electrode 2 having one end joined to the circuit surface 5a of the insulating substrate 5, a resin case 3 having a side wall 3a surrounding the sides of the insulating substrate 5 and a top wall 3b covering the upper part of the insulating substrate 5, a cylindrical electrode 1 having a tip portion 1a electrically connected to the other end of the electrode 2 inside the resin case 3, an embedded portion 1b embedded in the top wall 3b, and a protruding portion 1c protruding upward from the top wall 3b, a coating resin 3c extending from the top wall 3b so as to cover a side surface of the protruding portion 1c of the cylindrical electrode 1, and a screw 11 threadedly engaging with a threaded hole 1d in the cylindrical electrode 1 to fix a bus bar 9 or a control board 10 to the cylindrical electrode 1. The threaded hole 1d is provided only in the embedded portion 1b of the cylindrical electrode 1, and the protruding portion 1c of the cylindrical electrode 1 is provided with a screw insertion hole 1e that is connected to the threaded hole 1d and has a larger diameter than the threaded hole 1d.

[0033] Since the screw holes 1d are provided only in the embedded portion 1b of the cylindrical electrode 1, most of the tightening torque of the screws 11 can be received by the upper wall portion 3b existing around the embedded portion 1b of the cylindrical electrode 1. This reduces the tightening torque transmitted to the coating resin 3c.

[0034] In addition, the tip 1a of the cylindrical electrode 1 protrudes downward from the upper wall portion 3b, and the other end of the electrode 2 is provided with a polygonal recess or hole 15, and the tip 1a of the cylindrical electrode 1 is provided with a polygonal press-fit portion 16 that can be press-fitted into the recess or hole 15, and by pressing the press-fit portion 16 into the recess or hole 15, the tip 1a of the cylindrical electrode 1 is electrically connected to the other end of the electrode 2.

[0035] Therefore, the tightening torque can be received not only by the upper wall portion 3b around the embedded portion 1b of the cylindrical electrode 1 but also by the polygonal press-fit portion 16, thereby further reducing the tightening torque transmitted to the coating resin 3c covering the side surface of the protruding portion 1c of the cylindrical electrode 1. Note that instead of the above configuration, a polygonal recess (not shown) and a polygonal press-fit portion (not shown) may be provided at the tip portion 1a of the cylindrical electrode 1 and the other end of the electrode 2, respectively. In this case, the same effect can be obtained.

[0036] Second Embodiment Next, a semiconductor device 100 according to a second embodiment will be described. Fig. 3 is a cross-sectional view showing a connection structure between an electrode 2 and a cylindrical electrode 1 provided in a semiconductor device 100 according to a second embodiment. In Fig. 3, the sealant 12 and the screw 11 are not shown in order to simplify the drawing. Note that 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.

[0037] As shown in FIG. 3, the second embodiment differs from the first embodiment in the connection structure between the electrode 2 and the cylindrical electrode 1.

[0038] The tip 1a of the cylindrical electrode 1 does not protrude downward from the upper wall 3b. That is, not only the embedded portion 1b but also the tip 1a is embedded in the upper wall 3b. The tip 1a and the other end of the electrode 2 are joined by solder 17 or welding.

[0039] By joining the tip end 1a of the cylindrical electrode 1 and the other end of the electrode 2 by soldering 17 or welding, the electrode 2 can bear part of the tightening torque, similar to the connection structure between the electrode 2 and the cylindrical electrode 1 in embodiment 1. This not only further reduces the tightening torque transmitted to the coating resin 3c covering the side surface of the protrusion 1c, but also makes it possible to reduce the electrical resistance of the connection portion between the cylindrical electrode 1 and the electrode 2.

[0040] The electrode 2 and the cylindrical electrode 1 may be joined either before or after molding the resin case 3, but if joining is performed after molding the resin case 3, it is desirable to join the cylindrical electrodes 1 and 2 by spot welding or laser welding rather than reflow welding in order to avoid damage to the resin case 3 during joining. In particular, low electrical resistance is required for the cylindrical electrode 1, which carries the main current of the semiconductor device 100, so the connection structure between the electrode 2 and the cylindrical electrode 1 in embodiment 2 is desirable.

[0041] As described above, in the semiconductor device 100 according to the second embodiment, the tip 1a of the tubular electrode 1 is joined to the other end of the electrode 2 by solder 17 or welding, so that the tightening torque transmitted to the coating resin 3c covering the side surface of the protrusion 1c of the tubular electrode 1 can be further reduced compared to the first embodiment, and the electrical resistance of the connection portion between the tubular electrode 1 and the electrode 2 can be reduced.

[0042] Third Embodiment Next, a semiconductor device 100 according to a third embodiment will be described. Fig. 4 is a cross-sectional view showing a connection structure between an electrode 2 and a cylindrical electrode 1 provided in a semiconductor device 100 according to the third embodiment. In Fig. 4, the sealant 12 and the screw 11 are not shown to simplify the drawing. Note that 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.

[0043] In the first embodiment, the diameter of the embedded portion 1b of the cylindrical electrode 1 is the same as the diameter of the protruding portion 1c, but in the third embodiment, as shown in Fig. 4, the diameter D of the embedded portion 1b of the cylindrical electrode 1 is larger than the diameter d of the protruding portion 1c. The embedded portion 1b and the protruding portion 1c may be integrally formed, or may be made by joining separate members.

[0044] The structure of the cylindrical electrode 1 in the third embodiment can be adopted not only in the first embodiment but also in the second embodiment.

[0045] As described above, in the semiconductor device 100 according to the third embodiment, the diameter D of the embedded portion 1b of the tubular electrode 1 is larger than the diameter d of the protruding portion 1c, so that the tightening torque transmitted to the upper wall portion 3b existing around the embedded portion 1b of the tubular electrode 1 is dispersed, and the tightening torque transmitted to the coating resin 3c covering the side surface of the protruding portion 1c of the tubular electrode 1 can be further reduced compared to the first embodiment.

[0046] Although this disclosure has been described in detail, the above description is illustrative in all respects and is not restrictive. It is understood that countless variations not illustrated can be envisioned.

[0047] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate.

[0048] 1 Cylindrical electrode, 1a Tip portion, 1b Embedded portion, 1c Protruding portion, 1d Screw hole, 1e Screw insertion hole, 2 Electrode, 3 Resin case, 3a Side wall portion, 3b Upper wall portion, 9 Bus bar, 10 Control board, 11 Screw, 15 Hole, 16 Press-fit portion, 17 Solder

Claims

1. An insulating substrate having a circuit surface, an electrode having one end joined to the circuit surface of the insulating substrate, a resin case having a side wall portion surrounding the side of the insulating substrate and an upper wall portion covering the upper side of the insulating substrate, a cylindrical electrode having a tip electrically connected to the other end of the electrode inside the resin case, an embedded portion embedded in the upper wall portion, and a protruding portion protruding upward from the upper wall portion, a coating resin extending from the upper wall portion so as to cover the side surface of the protruding portion of the cylindrical electrode, and a screw for fixing a bus bar or a control board to the cylindrical electrode by screwing into a screw hole of the cylindrical electrode, wherein the screw hole is provided only in the embedded portion of the cylindrical electrode, and the protruding portion of the cylindrical electrode is provided with a screw insertion hole communicating with the screw hole and having a diameter larger than that of the screw hole. A semiconductor device.

2. The tip of the cylindrical electrode protrudes downward from the upper wall portion, a polygonal recess or hole is provided in the other end of the electrode, a polygonal press-fit portion that can be press-fitted into the recess or the hole is provided at the tip of the cylindrical electrode, and by press-fitting the press-fit portion into the recess or the hole, the tip of the cylindrical electrode is electrically connected to the other end of the electrode. The semiconductor device according to claim 1.

3. The tip of the cylindrical electrode protrudes downward from the upper wall portion, a polygonal recess is provided at the tip of the cylindrical electrode, a polygonal press-fit portion that can be press-fitted into the recess is provided at the other end of the electrode, and by press-fitting the press-fit portion into the recess, the tip of the cylindrical electrode is electrically connected to the other end of the electrode. The semiconductor device according to claim 1.

4. The semiconductor device according to claim 1, wherein the tip of the cylindrical electrode is joined to the other end of the electrode by soldering or welding.

5. The semiconductor device according to any one of claims 1 to 4, wherein the diameter of the embedded portion of the cylindrical electrode is larger than the diameter of the protruding portion.

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