semiconductor device

Abstract

Semiconductor device comprising: a lower electrode (10); a semiconductor chip (12) arranged on the lower electrode (10); a pressure pad (30, 32, 60, 62, 70, 72) arranged above or below the semiconductor chip (12); an upper electrode (36) arranged on a structure in which the pressure pad (30, 32, 60, 62, 70, 72) is superimposed on the semiconductor chip (12); and a connecting conductor (16, 52) which creates a new current path between the lower electrode (10) and the upper electrode (36) only when a distance between the lower electrode (10) and the upper electrode (36) becomes greater than a predetermined value due to a short-circuit current which causes a repulsive force between the lower electrode (10) and the upper electrode (36), wherein the distance between the lower electrode (10) and the upper electrode (36) is variable, and the pressure pad (30, 32, 60, 62, 70, 72) electrically connects the lower electrode (10) and the upper electrode (36) via the semiconductor chip (12) regardless of the variable distance between the lower electrode (10) and the upper electrode (36).

Description

Area

[0001] The present invention relates to a semiconductor device used, for example, for switching a large current. background

[0002] Patent Literature 1 discloses a press-pack type power semiconductor device. Patent Literature 1 discloses Fig. 1 shows a pressure-packed power semiconductor device with a plurality of semiconductor chips inside. The semiconductor chip is, for example, an IGBT. Electrical connection in the semiconductor chip is achieved by pressure contact between the upper and lower surfaces of individual elements of the semiconductor device. To evenly apply pressure to the plurality of semiconductor chips, a spring structure and clearance in an electrical conduction path for each semiconductor chip are necessary.

[0003] A pressure pad provides this clearance and ensures the electrical connection. Sometimes, a plurality of pressure pads is provided to increase the current-carrying capacity for normal current. A spring is placed between the pressure pads; this spring acts as an inductor, even if it is conductive, and it has a high impedance, especially for high-frequency waves. Therefore, no current flows through the spring. State of the art

[0004] In US 2004 / 0 207 070 A1, a stackable power semiconductor module comprises electrically conductive base plates, an electrically conductive cover plate, and several semiconductor chips. The semiconductor chips are arranged in groups of several on separate base plates in pre-assembled submodules. The base plates are movable toward the cover plate. The submodules are connected in parallel in the module housing. The submodules are fully testable according to their current ratings. By changing the number of submodules connected in parallel in the housing, the total current of a module can be varied.

[0005] From DE 199 03 245 A1 a power semiconductor module is known in which at least one pressure-contacted semiconductor chip is electrically connected to a main terminal via a contact element. Patent literature

[0006] Patent literature 1: JP 2004- 528 724 A SummaryTechnical problem

[0007] If a short circuit occurs in a pressure-packaged semiconductor device, the risk of the device exploding is a concern. For example, a short-circuit current flowing through a pressure pad melts and ruptures the pad due to the generation of Joule heat, generating an arc. An electrical path within the device is interrupted, creating an arc at the interrupted point. The heat from the arc causes an atmosphere within the device to expand or a solid within it to vaporize, causing the device to explode.

[0008] A robust explosion-proof structure provided within the device in the event of an explosion as discussed above has been a factor that has prevented downsizing and low cost of the device. Sometimes, a restriction of the operating current range and / or separate provision of short-circuit protection was / were necessary.

[0009] The present invention is designed to solve the above-mentioned problems, and its object is to provide a semiconductor device capable of preventing a pressure pad from melting and breaking. Means to solve the problems

[0010] This problem is solved by the features of the independent claims. The subclaims contain advantageous embodiments of the invention. Advantageous effects of the invention

[0011] According to the present invention, a pressure pad can be prevented from melting and breaking by reducing a short-circuit current applied to the pressure pad and / or increasing heat dissipation of the pressure pad. Short description of the drawings Fig. 1 is a cross-sectional view of a semiconductor device according to Embodiment 1. Fig. 2 is a diagram exemplifying a package of the semiconductor device according to Embodiment 1. Fig. 3 is a cross-sectional view of the semiconductor device in short circuit. Fig. 4 is a cross-sectional view of a semiconductor device according to Embodiment 2. Fig. 5 is a cross-sectional view of the semiconductor device in short circuit. Fig. 6 is a cross-sectional view of a semiconductor device according to Embodiment 3. Fig. 7 is a cross-sectional view of a semiconductor device according to Embodiment 4. Fig. 8 is a cross-sectional view of a semiconductor device according to Embodiment 5. Fig. 9 is a cross-sectional view of the semiconductor device in short circuit. Fig. 10 is a cross-sectional view of a semiconductor device according to Embodiment 6. Fig. 11 is a cross-sectional view of the semiconductor device in short circuit. Description of embodiments

[0012] Semiconductor devices according to embodiments of the present invention will be described with reference to the drawings. The same or corresponding components are given the same reference numerals, and repeated descriptions thereof are sometimes omitted. Embodiment 1

[0013] Fig. 1 is a cross-sectional view of a semiconductor device 1 according to Embodiment 1. This semiconductor device 1 includes a lower electrode 10. A semiconductor chip 12 is provided on the lower electrode 10. The semiconductor chip 12 is, for example, an IGBT or a diode. A plate 14 formed of metal is provided on the semiconductor chip 12.

[0014] A structure including a connecting conductor 16 and pressure pads 30 and 32 is provided on the plate 14. The connecting conductor 16 has a first part 17 and a second part 18. The first part 17 is a part that is fixed to the lower electrode 10 by being fixed to the plate 14 and moves in a form-fitting manner with the lower electrode 10. A cavity 17a is formed in the first part 17. Thus, an upper surface 17b of an inner wall is present therein.

[0015] The second part 18 includes a linear conductor 20A, an upper end part 20C, which is a horizontally long conductor provided at the upper end of the linear conductor 20A, and a lower end part 20B, which is a horizontally long conductor provided at the lower end of the linear conductor 20A. The linear conductor 20A and the lower end part 20B form an inverted T-shape. The linear conductor 20A is a conductor that extends downward from the top of an opening of the first part 17 by penetrating the opening. Since the lower end of the linear conductor 20A is positioned in the cavity 17a, the lower end part 20B is also positioned in the cavity 17a. As a result, the lower end part 20B is positioned below the upper end of the first part 17.

[0016] The pressure pads 30 and 32 constitute a spring electrode of a pressure-packed power semiconductor device. A plate 34 is provided on the pressure pads 30 and 32, and an upper electrode 36 is provided on the plate 34. The upper ends of the pressure pads 30 and 32 are fixed to the plate 34, and their lower ends are fixed to the upper surface of the first part 17. The pressure pads 30 and 32 expand and contract in the y-direction, that is, the direction perpendicular to the lower surface of the lower electrode 10 and the upper surface of the upper electrode 36. Therefore, the pressure pads 30 and 32 electrically connect the lower electrode 10 and the upper electrode 36 via the semiconductor chip 12, regardless of the distance between the lower electrode 10 and the upper electrode 36.

[0017] A spring 33 is provided between the pressure pads 30 and 32. This spring 33 exerts a force that decreases the distance between the lower electrode 10 and the upper electrode 36 when the distance between the lower electrode 10 and the upper electrode 36 increases, and exerts a force that increases the distance between the lower electrode 10 and the upper electrode 36 when the distance between the lower electrode 10 and the upper electrode 36 decreases.

[0018] The above-mentioned upper end portion 20C of the connecting conductor 16 is mechanically and electrically connected to the upper surfaces of the inner wall of the pressure pads 30 and 32. Accordingly, the second portion 18 is fixed to the upper electrode 36 via the pressure pads 30 and 32 and the plate 34 and moves in a positive manner with the upper electrode 36.

[0019] Fig. 1 is a cross-sectional view of the semiconductor device in the state where no current flows through the semiconductor chip 12. In the state where no current flows through the semiconductor chip 12, the first part 17 and the second part 18 are not in contact with each other. Furthermore, even during normal operation of the semiconductor device, the first part 17 and the second part 18 are not in contact with each other. Accordingly, in the case where no current flows through the semiconductor chip 12 and the case where the semiconductor device is operating normally, no current flows through the pressure pads 30 and 32 and does not flow through the second part 18.

[0020] Fig. 2 is a diagram exemplifying a package of the semiconductor device 1 according to Embodiment 1. Three semiconductor devices 1 share a lower electrode 10. Six semiconductor devices 1 are arranged on a base plate 37. Fig. 2 illustrates a stacking of two structures in each of which twelve semiconductor devices 1 are mounted on the base plate 37. Fig. Figure 2 illustrates a power semiconductor device constructed from the twelve semiconductor devices 1 in a pressure-packed form. A force is applied to this device from the top and bottom of the device, and the individual elements in the device are brought into pressure contact with each other, thereby establishing electrical connections in the semiconductor chips.

[0021] To uniformly apply pressure to the plurality of semiconductor chips 12, a spring structure and clearance in an electrical conduction path are necessary for each semiconductor device 1. The pressure pads 30 and 32 provide this clearance and ensure electrical connection. Three or more pressure pads for one semiconductor device can be provided to increase the current-carrying capacity for normal current. In particular, since the spring 33 between the pressure pads 30 and 32 serves as an inductor, even if it has conductivity, it has a high impedance, particularly for high-frequency waves, and no current flows through the spring 33.

[0022] Fig. 3 is a cross-sectional view of the semiconductor device 1 in a short circuit. Solid arrows indicate directions of short-circuit currents. Short-circuit currents in opposite directions flow through the upper electrode 36, which is an upper power terminal, and the lower electrode 10, which is a lower power terminal. These short-circuit currents cause a repulsive force to occur between the upper electrode 36 and the lower electrode 10. This repulsive force causes the lower end part 20B of the second part 18 to move upward in the cavity 17a. When the distance between the lower electrode 10 and the upper electrode 36 becomes greater than a predetermined value, the lower end part 20B comes into contact with the first part 17. Specifically, the upper surface of the lower end part 20B comes into contact with the upper surface 17b of the inner wall of the first part 17.Only when the distance between the lower electrode 10 and the upper electrode 36 becomes greater than the predetermined value does the connecting conductor 16 create a new current path between the lower electrode 10 and the upper electrode 36.

[0023] For a contact of the lower end part 20B with the first part 17 when the short-circuit currents flow, the normal distance between the lower end part 20B and the upper surface 17b of the inner wall of the first part is now set slightly smaller than an increase in the distance between the upper electrode 36 and the lower electrode 10 due to a short circuit.

[0024] Since in Embodiment 1 of the present invention, in the event of a short-circuit condition, a current can be caused to flow not only through the pressure pads 30 and 32 but also through the connecting conductor 16, currents flowing through the pressure pads 30 and 32 can be reduced, and a temperature rise of the pressure pads 30 and 32 can be reduced. Therefore, the pressure pads 30 and 32 can be prevented from melting and breaking. Accordingly, since the semiconductor device according to Embodiment 1 of the present invention will not explode, a conventionally provided explosion-proof measure can be eliminated, which can achieve downsizing and low cost of the device.

[0025] Furthermore, in Embodiment 1 of the present invention, the lateral surface of the first part 17 and the lateral surface of the second part 18 are always separated from each other. Therefore, a problem such as an arc occurring due to insufficient electrical contact during normal operation can be prevented. In addition, since the spring 33 is provided, the upper electrode 36 and the lower electrode 10 are not separated too much from each other. Therefore, an effect of preventing peeling of a component in the semiconductor device in the longitudinal direction of the second part 18 due to excessive force applied to the second part 18 caused by the upper electrode 36 and the lower electrode 10 being separated too much from each other can also be expected.In particular, it is preferable to form an insulating film, for example, on at least one lateral surface of the linear conductor 20A, the lateral surfaces of the pressure pads 30 and 32, and the lateral surface of the first part 17 to prevent an occurrence of an arc.

[0026] As above, in Embodiment 1 of the present invention, focusing on the fact that the distance between the lower electrode 10 and the upper electrode 36 changes depending on the presence or absence of a short-circuit current, the connecting conductor 16 creates a new current path between the lower electrode 10 and the upper electrode 36 only when the distance between the lower electrode 10 and the upper electrode 36 becomes greater than a predetermined value. Various modifications of the connecting conductor 16 and the like may be made as long as they do not deteriorate their characteristics. For example, the linear conductor 20A and the lower end portion 20B do not have to form a T-shape; they may form an L-shape. In addition, the lower end portion 20B is intended to rise in the short circuit, and in this case, the upper surface of the lower end portion 20B may come into contact with the lower surfaces of the pressure pads 30 and 32.

[0027] Although the pressure pads 30 and 32 are provided above the semiconductor chip 12, their stacking order can be reversed so that the pressure pads 30 and 32 are provided below the semiconductor chip 12. The upper electrode 36 is provided above a structure in which the pressure pads 30 and 32 are superimposed on the semiconductor chip 12. Any stacking order of the individual elements between the lower electrode 10 and the upper electrode 36 can be provided, as long as the structure in which the pressure pads 30 and 32 are superimposed on the semiconductor chip 12 can be arranged between the lower electrode 10 and the upper electrode 36. Structures in which the pressure pads 30 and 32 are "superimposed" on the semiconductor chip 12 are not limited to direct contact between the two, but may include inserting a plate or the like between the two. Plates may be appropriately provided between such elements.Plates 14 and 22 may be added or eliminated as appropriate.

[0028] In addition, the entire configuration, which includes the connecting conductor 16 and the pressure pads 30 and 32 in Fig. 1, can be turned upside down. In this case, the first part 17 is provided above the pressure pads 30 and 32. Furthermore, a part corresponding to the cavity 17a of the first part 17 can be provided in the plate 14 or the plate 34 to receive the lower end part 20B in this cavity and omit the first part 17.

[0029] Although the semiconductor chip 12 may be made of silicon, it may be made of a wide-bandgap semiconductor having a larger bandgap than silicon. Examples of the wide-bandgap semiconductor include silicon carbide, a gallium nitride-based material, and diamond. By using the wide-bandgap semiconductor, the possible operating temperature of the device increases. Moreover, silicon carbide enables a MOSFET, which is a monopolar device, to have a high withstand voltage, which can achieve high frequency and high efficiency. In particular, these modifications can also be applied to semiconductor devices according to the following embodiments.

[0030] Since the semiconductor devices according to the following embodiments have a great similarity to that of Embodiment 1, their differences from that of Embodiment 1 will be mainly described. Embodiment 2

[0031] Fig. 4 is a cross-sectional view of a semiconductor device according to Embodiment 2. A connecting conductor 52 includes a metal block 50 provided on the lower surfaces of the inner wall of the pressure pad 30 and the pressure pad 32, a linear conductor 52A fixed to the metal block 50, and an upper end portion 52B connected to the linear conductor 52A. The metal block 50 is connected to the lower end of the linear conductor 52A. The upper end portion 52B is connected to the upper end of the linear conductor 52A. A T-shaped structure composed of the linear conductor 52A and the upper end portion 52B is fixed to the upper surface of the metal block 50.

[0032] The metal block 50 is preferably formed, for example, from a material with excellent heat dissipation, such as copper. The metal block 50 is a large metal lump. The metal block 50 according to Embodiment 2 has a width greater than the distance between the upper end portion of the pressure pad 30 and the upper end portion of the pressure pad 32, and is longer than half the length of the pressure pad 30, 32.

[0033] The linear conductor 52A penetrates a gap between the upper end portion of the pressure pad 30 and the upper end portion of the pressure pad 32. Furthermore, a cavity 34a is provided in the plate 34. The upper end portion 52B is housed in this cavity 34a. In the normal state, the upper end portion 52B is not in contact with the plate 34 or the pressure pads 30 and 32. Similar to Embodiment 1, an insulating film may be formed on at least one of the lateral surfaces of the linear conductor 52A and the lateral surfaces of the pressure pads 30 and 32.

[0034] Springs 58 are provided on the metal piece 50. The springs 58 are provided between the upper surfaces of the inner wall of the pressure pads 30 and 32 and the metal block 50. By appropriately maintaining the distance between the pressure pads 30 and 32 and the metal block 50, the springs 58 prevent peeling between the components of the semiconductor device and ensure electrical connection in the semiconductor chip 12. A plate 40 is provided on and below the pressure pads 30 and 32. The plate 40 is in contact with the upper surface of the plate 14.

[0035] Fig. 5 is a cross-sectional view of the semiconductor device in a short circuit. When a short circuit occurs, the distance between the lower electrode 10 and the upper electrode 36 increases, and thereby the lower surface of the upper end part 52B comes into contact with the upper surfaces of the pressure pads 30 and 32. Thus, short-circuit currents flow not only through the pressure pads 30 and 32 but also through the connecting conductor 52. Since short-circuit currents flowing through the pressure pads 30 and 32 can be reduced more than when the short-circuit currents flow only through the pressure pads 30 and 32, the pressure pads 30 and 32 can be prevented from melting and breaking. Since the short-circuit current is caused to flow particularly through the metal block 50, an impedance of this part can be made smaller than that in Embodiment 1.Therefore, a greater effect of preventing melting and cracking than that for the semiconductor device according to Embodiment 1 can be expected.

[0036] Now, when large currents flow in the same directions through the pressure pad 30 and the pressure pad 32, an attractive force sometimes occurs between the pressure pads 30 and 32, so that the pressure pads 30 and 32 come into close contact with the lateral surface of the metal block 50. To prevent this, the metal block 50 can be extended in the directions on the front and back of the view plane, or out of and into the view plane, and thereby the attractive force exerted on the pressure pads 30 and 32 can be reduced. Embodiment 3

[0037] Fig. 6 is a cross-sectional view of a semiconductor device according to Embodiment 3. The connecting conductor 52 containing the metal block 50 is placed above the plate 14. The main difference between the semiconductor device according to Embodiment 3 and the semiconductor device according to Embodiment 2 is the shape of the pressure pads. The upper end portions of the pressure pads 60 and 62 in Embodiment 3 are fixed to the plate 34. Therefore, the pressure pads 60 and 62 are mechanically and electrically connected to the upper electrode 36.

[0038] The pressure pads 60 and 62 contact the metal block 50 near the center of its lateral surface with their inwardly directed spring forces. Although the pressure pads 60 and 62 are electrically connected to the metal block 50, they are not mechanically attached thereto. Therefore, the pressure pads 60 and 62 slide on the lateral surface of the metal block 50 into contact with it as the distance between the lower electrode 10 and the upper electrode 36 changes.

[0039] Springs 66 are positioned on the upper surface of the metal block 50. These springs 66 ensure the degree of freedom of the distance between the lower electrode 10 and the upper electrode 36, while ensuring electrical connections between the individual components of the semiconductor device. When short-circuit currents flow through the semiconductor chip 12, a repulsive force occurs between the upper electrode 36 and the lower electrode 10, increasing the distance between the upper electrode 36 and the lower electrode 10. Accordingly, the pressure pads 60 and 62 slide on the lateral surface of the metal block 50, and the upper end portion 52B comes into contact with the lower surface of the inner wall of the plate 34. Thus, a short-circuit current can be caused to flow through the connecting conductor 52.In particular, by extending the metal block 50 in the horizontal direction parallel to the viewing plane, in the direction out of the viewing plane, or in the direction into the viewing plane, an attractive force exerted on the pressure pad 60 and the pressure pad 62 can be adjusted. Embodiment 4

[0040] Fig. 7 is a cross-sectional view of a semiconductor device according to Embodiment 4. In this semiconductor device, in addition to the pressure pads 30 and 32, pressure pads 70 and 72 are provided, thus reducing the current value for each pressure pad. Since a temperature rise of each pressure pad can be suppressed by increasing the number of pressure pads, this is effective in preventing melting and breakage of a pressure pad. The number of pressure pads must be a multiple and is not limited to four. Melting and breakage of a pressure pad can be prevented by providing a plurality of pressure pads in a semiconductor device and causing currents to be individually allocated to them. Embodiment 5

[0041] Fig. 8 is a cross-sectional view of a semiconductor device according to Embodiment 5. In the semiconductor device of Embodiment 5, the semiconductor device in Fig. 4, the linear conductor 52A, the upper end portion 52B, and the cavity 34a are removed. The metal block 50 is provided to be superimposed on the semiconductor chip 12. The pressure pads 30 and 32 are provided between the lower electrode 10 and the upper electrode 36, electrically connecting the lower electrode 10 and the upper electrode 36 via the semiconductor chip 12. The pressure pads 30 and 32 are provided to oppose each other, allowing the metal block 50 to be interposed therebetween.

[0042] When a current flowing through the two pressure pads 30 and 32 is not more than a predetermined value, as shown in Fig. 8, the two pressure pads 30 and 32 are separated from the lateral surface of the metal block 50. Since the normal current is the above-mentioned current that is "not more than the predetermined value," the normal current flows only through the pressure pads 30 and 32, not through the metal block 50.

[0043] Fig. 9 is a cross-sectional view of the semiconductor device in a short circuit. In the event of a short-circuit failure of the semiconductor chip 12, currents flow in the same directions through the pressure pads 30 and 32. When a current flowing through the two pressure pads 30 and 32 becomes larger than the predetermined value due to the short circuit occurring, a strong attractive force occurs between the two pressure pads 30 and 32. This attractive force reduces the distance between the two pressure pads 30 and 32, and the pressure pads 30 and 32 come into contact with the lateral surface of the metal block 50.

[0044] When the attractive force between the two pressure pads 30 and 32 is large as above, the pressure pads 30 and 32 collapse, so that they adhere to the metal block 50, and thus the short-circuit current also flows through the metal block 50. Therefore, the pressure pads 30 and 32 can be prevented from melting and breaking. Moreover, since a large heat capacity of the metal block 50 suppresses a temperature rise of the pressure pads 30 and 32, the effect of preventing the melting and breaking of the pressure pads 30 and 32 can be enhanced. In particular, by extending the metal block 50 in the directions out of and into the viewing plane, the force exerted on the pressure pads 30 and 32 can be adjusted. Embodiment 6

[0045] Fig. 10 is a cross-sectional view of a semiconductor device according to Embodiment 6. In the semiconductor device of Embodiment 6, the semiconductor device in Fig. 6, the linear conductor 52A, the upper end portion 52B, and the cavity 34a are removed. The two pressure pads 60 and 62 are mechanically and electrically connected to the upper electrode 36. Furthermore, the two pressure pads 60 and 62 are in contact with parts of the lateral surface of the metal block 50 while exerting an elastic force on the lateral surface of the metal block 50. Furthermore, the two pressure pads 60 and 62 slide on the lateral surface of the metal block 50 in contact therewith as the distance between the lower electrode 10 and the upper electrode 36 changes.

[0046] When a current flowing through the two pressure pads 60 and 62 is not more than a predetermined value, as shown in Fig. As shown in Figure 10, the contact area of ​​the two pressure pads 60 and 62 with the lateral surface of the metal block 50 is small. Therefore, a certain contact resistance exists between the two pressure pads 60 and 62 and the lateral surface of the metal block 50.

[0047] Fig.11 is a cross-sectional view of the semiconductor device in a short circuit. Since an attractive force is exerted between the pressure pads 60 and 62 when the semiconductor chip 12 is short-circuited, this attractive force causes the pressure pads 60 and 62 to adhere to the lateral surface of the metal block 50. This is because the contact area of ​​the two pressure pads 60 and 62 with the lateral surface of the metal block 50 increases. Since a short-circuit current can be caused to flow in the state where the contact resistance between the two pressure pads 60 and 62 and the lateral surface of the metal block 50 is reduced, the pressure pads 60 and 62 can be prevented from melting and breaking.

[0048] Furthermore, since a large heat capacity of the metal block 50 suppresses a temperature rise of the pressure pads 60 and 62, the effect of preventing melting and breakage of the pressure pads 60 and 62 can be enhanced. In particular, by extending the metal block 50 in the direction out of the view plane and in the direction into the view plane, an attractive force exerted between the pressure pads 60 and 62 can be adjusted.

[0049] In the inventions of Embodiments 5 and 6, the pressure pads are formed to a certain extent thin, so that when a current flowing through the two pressure pads becomes greater than a predetermined value, the distance between the two pressure pads becomes small, and the contact area of ​​the two pressure pads with the lateral surface of the metal block is allowed to increase. Various modifications of these can be made as long as they do not lose these features.

[0050] In particular, the features of the above-mentioned semiconductor devices according to the individual embodiments can be appropriately combined to enhance the effect of the present invention. Description of the symbols

[0051] 10 lower electrode, 12 semiconductor chip, 16 connecting conductor, 30, 32 pressure pad, 36 upper electrode

Claims

[1] A semiconductor device comprising: a lower electrode (10); a semiconductor chip (12) arranged on the lower electrode (10); a pressure pad (30, 32, 60, 62, 70, 72) arranged above or below the semiconductor chip (12); an upper electrode (36) arranged on a structure in which the pressure pad (30, 32, 60, 62, 70, 72) is superimposed on the semiconductor chip (12); and a connecting conductor (16, 52) which creates a new current path between the lower electrode (10) and the upper electrode (36) only when a distance between the lower electrode (10) and the upper electrode (36) becomes greater than a predetermined value due to a short-circuit current which causes a repulsive force between the lower electrode (10) and the upper electrode (36), wherein the distance between the lower electrode (10) and the upper electrode (36) is variable, and the pressure pad (30, 32, 60, 62, 70, 72) electrically connects the lower electrode (10) and the upper electrode (36) via the semiconductor chip (12) regardless of the variable distance between the lower electrode (10) and the upper electrode (36). [2] A semiconductor device according to claim 1, wherein the connecting conductor (16, 52) comprises a first part (17) which moves in a form-fitting manner with the lower electrode (10), and a second part (18) which moves in a form-fitting manner with the upper electrode (36), a lower end part (20B) of the second part (18) is positioned below an upper end of the first part (17), and the lower end part (20B) comes into contact with the first part (17) when the distance between the lower electrode (10) and the upper electrode (36) becomes greater than the predetermined value. [3] A semiconductor device according to claim 2, wherein a lateral surface of the first part (17) is always separated from a lateral surface of the second part (18). [4] A semiconductor device according to any one of claims 1 to 3, wherein the connecting conductor (52) includes a metal block (50). [5] A semiconductor device according to claim 1, wherein the connecting conductor (52) contains a metal block (50), and the pressure pad (60, 62) is in contact with a lateral surface of the metal block (50) and slides on the lateral surface of the metal block (50) in contact therewith when the distance between the lower electrode (10) and the upper electrode (36) changes. [6] A semiconductor device according to any one of claims 1 to 5, comprising a plurality of said pressure pads (30, 32, 70, 72). [7] A semiconductor device comprising: a lower electrode (10); an upper electrode (36) arranged above the lower electrode (10); a semiconductor chip (12) arranged between the lower electrode (10) and the upper electrode (36); a metal block (50) arranged between the lower electrode (10) and the upper electrode (36) so as to be superimposed on the semiconductor chip (12); and two pressure pads (30, 32, 60, 62, 70, 72) arranged between the lower electrode (10) and the upper electrode (36), wherein the two pressure pads (30, 32, 60, 62, 70, 72) are configured to electrically connect the lower electrode (10) and the upper electrode (36) to each other via the semiconductor chip (12) and are arranged so that they are opposite to each other, which allows the metal block (50) to be arranged between the two pressure pads (30, 32, 60, 62, 70, 72), wherein when a current flowing through the two pressure pads (30, 32, 60, 62, 70, 72) in the short circuit becomes greater than a predetermined value, a distance between the two pressure pads (30, 32, 60, 62, 70, 72) decreases and a contact area of ​​the two pressure pads (30, 32, 60, 62, 70, 72) with a lateral surface of the metal block (50) is created or increased. [8] A semiconductor device according to claim 7, wherein when the current flowing through the two pressure pads (30, 32, 60, 62, 70, 72) is not more than the predetermined value, the two pressure pads (30, 32, 60, 62, 70, 72) are separated from the lateral surface of the metal block (50). [9] A semiconductor device according to claim 7, wherein the two pressure pads (60, 62) are in contact with a part of the lateral surface of the metal block (50) while exerting an elastic force on the lateral surface of the metal block (50), and slide on the lateral surface of the metal block (50) in contact therewith when a distance between the lower electrode (10) and the upper electrode (36) changes. [10] A semiconductor device according to any one of claims 1 to 9, comprising a spring (33) that applies a force that decreases the distance between the lower electrode (10) and the upper electrode (36) when the distance between the lower electrode (10) and the upper electrode (36) increases, and applies a force that increases the distance between the lower electrode (10) and the upper electrode (36) when the distance between the lower electrode (10) and the upper electrode (36) decreases. [11] A semiconductor device according to any one of claims 1 to 10, wherein the semiconductor chip (12) is formed of a wide band gap semiconductor. [12] A semiconductor device according to claim 11, wherein the wide band gap semiconductor (12) is silicon carbide, a gallium nitride-based material, or diamond.

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