JP2020038893A - Semiconductor device - Google Patents

Abstract

To provide a semiconductor device which has excellent rupture prevention performance during short circuit current with a structure without using pressure-welding.SOLUTION: A semiconductor device includes a plurality of semiconductor element modules connected in parallel. Each of the semiconductor element modules SM1a and SM1b has at least one planar semiconductor element 40. A metallic member 20 in contact with one surface of the semiconductor element 40, a second metallic member 30 in contact with the other surface of the semiconductor element 40, and the semiconductor element 40 are laminated. A metallic reinforcing member 50 is provided to surround upper and lower sides in a lamination direction of the laminated metallic member 20, semiconductor element 40 and metallic member 30. The metallic member 30 and the metallic reinforcing member 50 are connected through a connection conductor 90. The connection conductor 90 has electrical resistivity larger than that of the second metallic member 30 or the metallic reinforcing member 50. A second connection conductor 95 connected to the metallic reinforcing member 50 has electrical resistivity larger than the metallic member 20 or the second metallic member 30.SELECTED DRAWING: Figure 9

Description

  Embodiments relate to a semiconductor device.

  There is a semiconductor device which can switch a large current of several kiloamps (kA) by connecting a plurality of semiconductor elements in parallel. In such a semiconductor device, a power converter that operates under a high voltage of several kilovolts (kV) can be configured by connecting a plurality of semiconductor devices in series.

  Further, in the power conversion device, it is preferable that one of the semiconductor devices connected in series has redundancy so that operation can be continued by the remaining semiconductor device even if a short circuit fault occurs. For this purpose, an explosion-proof structure that can avoid explosive damage when a semiconductor device is short-circuited is adopted.

Japanese Patent No. 4385324

  In order to avoid explosive damage when a semiconductor device is short-circuited, a press-contact type semiconductor in which a semiconductor element is sandwiched between conductors and sealed with a ceramic envelope is known. However, in the press-contact type semiconductor, it is required to press-contact all the semiconductor elements uniformly. Therefore, the processing accuracy of the parts and the assembly accuracy of the stack structure are required at a high level, and the cost is increased.

  On the other hand, although a semiconductor device not using pressure welding has been proposed, there is a problem that the rupture prevention performance when a short-circuit current flows at the time of failure is poor.

  The semiconductor device of the present embodiment has been proposed to solve the above-described problems of the related art, and provides a semiconductor device having a structure that does not use pressure welding and having excellent burst prevention performance at the time of short-circuit current. I do.

  The semiconductor device according to the present embodiment is a semiconductor device including a plurality of semiconductor element units connected in parallel, the semiconductor element unit including at least one plate-shaped semiconductor element, and one surface of the semiconductor element. A first metal member that is in contact with the first metal member, a second metal member that is in contact with the other surface of the semiconductor element, and faces the first metal member via the semiconductor element, A metal reinforcing member provided so as to surround the semiconductor element and the second metal member in the vertical direction in the stacking direction; and a first metal member or a second metal connected to the second metal member and the metal reinforcing member. A first connection conductor having an electric resistivity higher than that of the member; and a second connection conductor having one end connected to the metal reinforcing member and having an electric resistivity higher than that of the first and second metal members. To.

FIG. 2 is a perspective view illustrating the semiconductor device according to the first embodiment. FIG. 2 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. FIG. 2 is a perspective view schematically illustrating the semiconductor element module according to the first embodiment. FIG. 2 is a perspective view illustrating an exploded configuration of the semiconductor element module according to the first embodiment. FIG. 2 is a schematic cross-sectional view illustrating the semiconductor element module according to the first embodiment. FIG. 2 is a schematic cross-sectional view of another coordinate plane showing the semiconductor element module according to the first embodiment. FIG. 2 is a schematic cross-sectional view of another coordinate plane showing the semiconductor element module according to the first embodiment. FIG. 3 is a three-view drawing showing the semiconductor device according to the first embodiment. FIG. 2 is a cross-sectional view illustrating the semiconductor device according to the first embodiment. It is a perspective view showing the component of the semiconductor element module concerning a 2nd embodiment. It is a perspective view showing the component of the semiconductor element module concerning a 3rd embodiment. It is a perspective view showing a part of the assembling method of the semiconductor element module concerning a 3rd embodiment. It is a three-view figure showing the component of the semiconductor element module concerning a 4th embodiment. It is a perspective view showing a part of the assembling method of the semiconductor element module concerning a 4th embodiment. It is sectional drawing which shows the component of the semiconductor element module which concerns on 5th Embodiment. It is a figure showing the analysis value of the electric resistance in the component of the semiconductor element module concerning a 5th embodiment. FIG. 4 is a schematic cross-sectional view illustrating a semiconductor element module according to a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. The same portions in the drawings are denoted by the same reference numerals, detailed description thereof will be appropriately omitted, and different portions will be described. The drawings are schematic or conceptual, and the relationship between the thickness and the width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. In addition, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings. In addition, for the sake of convenience of description, a strict cross-sectional view is not necessarily used, and a simplified expression method may be partially used.

  Further, the arrangement and configuration of each part will be described using the X axis, Y axis, and Z axis shown in each drawing. The X axis, the Y axis, and the Z axis are orthogonal to each other, and represent the X, Y, and Z directions, respectively. In some cases, the Z direction is described as upward and the opposite direction is defined as downward.

[1. First Embodiment]
[1-1. Schematic configuration]
FIG. 1 is a perspective view illustrating the semiconductor device according to the first embodiment. FIG. 2 is a schematic sectional view showing the semiconductor device according to the first embodiment.

  As shown in FIGS. 1 and 2, in a semiconductor device 1 of the present embodiment, two semiconductor element modules SM <b> 1 a and SM <b> 1 b are mounted on a cooling member 10. Two semiconductor modules SM1a and SM1b are electrically connected in parallel. The semiconductor device 1 includes semiconductor element modules SM1a and SM1b, a cooling member 10, and an emitter conductor 100.

  The cooling member 10 is a rectangular parallelepiped member, and the bottom surface and the top surface are rectangular. The bottom surface and the top surface are located on the XY coordinate plane. Cooling member 10 contains iron, stainless steel, or aluminum as a main component. On the top surface of the cooling member 10, a collector terminal connecting portion 10T and two convex portions are provided at predetermined intervals.

  The collector terminal connection part 10T is a terminal common to the modules SM1a and SM1b.

  The convex portion is a rectangular parallelepiped, and the bottom surface of the convex portion is in contact with the top surface of cooling member 10, and the side surface of the convex portion stands upright with respect to the top surface of cooling member 10. The top surface of the projection is smooth so that no gap is formed between the top surface of the projection and the metal member when the top surface of the projection comes into contact with the respective metal members of the semiconductor modules SM1a and SM1b. The projection may be formed integrally with the cooling member 10.

  The cooling member 10 has a space 13 inside. In the cross section of the space 13 orthogonal to the bottom surface and the top surface of the cooling member 10, the space 13 is substantially rectangular. Cooling fins 15 are provided on the top side of the cooling member 10 in the gap 13. The cooling fins 15 are projections provided to increase the heat transfer area. For example, heat is radiated from the semiconductor element module SM1 by circulating a cooling liquid such as pure water inside the gap 13.

  The semiconductor element modules SM1a and SM1b are modules including at least one semiconductor element 40, a metal member 20, a metal member 30, and a second connection conductor 95. The semiconductor element 40 is, for example, a transistor element such as an IGBT (Insulated Gate Bipolar Transistor), a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a diode element such as an FRD (Fast Recovery Diode). One semiconductor element module SM1 may include both a transistor element and a diode element.

  The metal member 20 and the metal member 30 are plate-shaped members. One surface of the semiconductor element 40 contacts the metal member 20, and the other surface of the semiconductor element 40 contacts the metal member 30. In other words, the metal member 20, the metal member 30, and the semiconductor element 40 are stacked in the order of the metal member 30, the semiconductor element 40, and the metal member 20.

  Each of the semiconductor element modules SM1a and SM1b is a rectangular parallelepiped in which two of the six surfaces are open. The second connection conductor 95 protrudes from one opening surface located on the side surface when disposed on the cooling member. In addition, the metal member 20 is exposed from an opening surface that opens at a position facing the top surface of the cooling member when it is disposed on the cooling member. The shape of the opening surface from which the metal member 20 is exposed is a shape into which a convex portion can be inserted.

  The second connection conductor 95 is a member having the shape of a square pole. The emitter conductor 100 is connected to the end of the second connection conductor 95 protruding from the opening surface. The emitter conductor 100 has a so-called L-shape including a long side portion and a short side portion extending vertically from an end of the long side portion. The emitter conductor 100 is formed of a good electric conductive material such as copper or aluminum. The long side of the emitter conductor is connected to the second connection conductor 95 projecting from the semiconductor element modules SM1a and SM1b, and the short side of the emitter conductor 100 is formed with a common emitter terminal connection 100T.

  With such a configuration, the two semiconductor modules SM1a and SM1b are electrically connected in parallel.

[1-2. Configuration of Semiconductor Element Module]
FIG. 3 is a perspective view schematically showing the semiconductor element module SM1 according to the first embodiment. In FIG. 3, the resin member 70 is omitted to show the structure of the semiconductor element module SM1.

  As shown in FIG. 3, the second connection conductor 95 is provided on the semiconductor element module SM1. One end of the second connection conductor 95 is joined to the reinforcing member 70, and the other end of the second connection conductor 95 extends from the open portion of the case 60 to the outside. In FIG. 3, the second connection conductor 95 is shown as a square rod having a square cross section, but the cross section is not limited to a square or even a square. Further, the cross-sectional shape is not constant, and may change midway. Further, the shape is not limited to a straight rod shape, and may have an arc-shaped curved portion, or may have a bent portion in the middle.

  FIG. 4 is a perspective view schematically showing an exploded state of main components of the semiconductor element module SM1 according to the first embodiment. In FIG. 4, the resin member 70 is omitted to show the structure of the semiconductor element module SM1.

  As shown in FIG. 4, a first connection conductor 90 is provided between the metal member 30 and the reinforcing member 50, one end is joined to the metal member 30, and the other end is joined to the inside of the case 50. Have been.

  The semiconductor element module SM1 has an opening OP on the lower surface to expose a part of the metal member 20. The reinforcing member 50 has an opening OP50 corresponding to the opening OP, and the case 60 has an opening OP60 corresponding to the opening OP. The opening OP50 and the opening OP60 are, specifically, substantially rectangular through holes. The metal member 20 is connected to the cooling member 10 via the opening OP50 (see FIG. 1).

  FIGS. 5, 6, and 7 are schematic views showing a cross section of the semiconductor element module SM1. Each figure shows a plane defined by two axes out of three coordinate axes (X axis, Y axis, Z axis). Yes, it is. For example, FIG. 5 is a cross-sectional view corresponding to the XZ coordinate plane. However, they generally correspond to the direction of the arrow C shown in FIG. 6, and the respective figures have a correlation (as described above, they are not strict cross-sectional views).

  The semiconductor element module SM1 further includes a reinforcing member 50, a case 60, a resin member 70, and a resin member 75.

  The reinforcing member 50 is provided so as to surround the metal members 20 and 30. The reinforcing member 50 is, for example, a metal member. The case 60 is made of, for example, a resin member, and accommodates the metal members 20, 30, the semiconductor element 40, and the reinforcing member 50 therein.

  As shown in FIG. 5, the metal member 30 has a protrusion 30a on the lower surface.

  The semiconductor element 40 is disposed between the metal member 20 and the protrusion 30a. The protrusion 30a is disposed between the metal member 30 and the semiconductor element 40. The protrusion 30a may be provided integrally with the metal member 30, or may be a conductive member attached to the lower surface of the metal member 30. On the lower surface of the metal member 30, the same number of protrusions 30a as the semiconductor elements 40 are provided.

  On the surface 40T of the semiconductor element 40, for example, a first electrode (not shown) which is an emitter electrode, a source electrode, or a cathode electrode is provided. The first electrode is connected to the protrusion 30a by a conductive bonding material (not shown). The protrusion 30a has, for example, a shape that fits the first electrode when viewed in the Z direction.

  On the other hand, a second electrode (not shown) that is, for example, a collector electrode, a drain electrode, or an anode electrode is provided on the back surface 40B of the semiconductor element 40. The second electrode is connected to the metal member 20 via a conductive bonding material (not shown).

  The resin member 70 is provided so as to fill the internal space of the reinforcing member 50. Part of the resin member 70 seals the semiconductor element 40 between the metal member 20 and the metal member 30. Further, a part of the resin member 70 is filled between the metal member 20 and the reinforcing member 50 and between the metal member 30 and the reinforcing member 50.

  The resin member 75 is filled between the reinforcing member 50 and the case 60. The resin members 70 and 75 are a thermosetting resin such as an epoxy resin, for example, and are formed by vacuum molding.

  FIG. 6 is a schematic diagram showing another cross section of the semiconductor module SM1 corresponding to the XY coordinate plane. At the same time, it generally corresponds to the BB section shown in FIG. FIG. 6 is a cross-sectional view illustrating the semiconductor element 40 disposed on the metal member 20. The semiconductor element 40 is, for example, a transistor element and has a gate electrode 45.

  As shown in FIG. 6, two semiconductor elements 40 are arranged on the metal member 20. The semiconductor element 40 has an emitter electrode 43 (or a source electrode) provided on the surface 40T and a gate electrode 45. A gate terminal 80 is connected to the gate electrode 45. Gate terminal 80 extends from resin member 70 to the outside of semiconductor element module SM1. The gate terminal 80 is made of, for example, a metal material containing copper or aluminum as a main component, and is connected to a control circuit (not shown).

  The metal members 20 and 30 and the semiconductor element 40 are housed inside, for example, a box-shaped reinforcing member 50 whose one side is open. The case 60 that covers the reinforcing member 50 also has a box-like shape with one surface opened. The gate terminal 80 extends outside from the opening of the reinforcing member 50 and the case 60.

  FIG. 7 is a schematic diagram showing another cross section of the semiconductor module SM1 corresponding to the YZ coordinate plane. At the same time, it generally corresponds to the AA cross section shown in FIG. FIG. 7 is a cross-sectional view illustrating a configuration related to the metal member 30 and the reinforcing member 50. The first connection conductor 90 is provided between the metal member 30 and the reinforcing member 50. The first connection conductor 90 is made of, for example, a metal part mainly containing an alloy of nickel and chromium (Nichrome material) or an alloy of nickel and iron (42 alloy), and one end is joined to the metal member 30 and opposite to the other end. The end on the side is joined to the case 50.

  Further, a second connection conductor 95 is provided at an end of the case 50. Similarly, the second connection conductor 95 is made of a metal portion containing, for example, an alloy of nickel and chromium (Nichrome material) or an alloy of nickel and iron (42 alloy) as a main component. The end on the side extends from the release portion of the case 60 to the outside.

  FIG. 8 is a three-view drawing showing the semiconductor device according to the first embodiment. A collector-side current path in the semiconductor device of the present embodiment is simply shown by an IC. The collector-side current IC passes through the path of the collector terminal connection portion 10T → the cooling member 10 → the metal member 20 → the semiconductor element 40.

  The semiconductor module SM1 may pass through the semiconductor module SM1a or pass through the semiconductor module SM1b, and the current is distributed in the cooling member 10. Actually, a current having a three-dimensional spread is generated in each component, but this is a simple expression in particular.

  FIG. 9 is a diagram showing the cross-sectional view shown in FIG. 8 alone. The IE-side current path in the semiconductor device of the present embodiment is simply indicated by IE. The emitter-side current IE passes through the path of the semiconductor element 40 → the metal member 30 → the first connection conductor 90 → the reinforcing member 50 → the second connection conductor 95 → the emitter conductor 100 → the emitter terminal connection part 100T.

  Similarly to the collector side, the semiconductor module SM1 may pass through the semiconductor module SM1a or pass through the semiconductor module SM1b. On the emitter side, in the emitter conductor 100, the current passing through the semiconductor module SM1a and the current passing through the semiconductor module SM1b merge to form a parallel circuit. Further, similarly to the collector side, in reality, a current having a three-dimensional spread is generated in each component, but this is a simplified expression particularly in that respect.

[1-3. Effect]
In the semiconductor device of the present embodiment as described above, the reinforcing member 50 surrounding the metal member 20 and the metal member 30 is provided. The reinforcing member 50 suppresses the displacement and deformation when the metal member 20 and the metal member 30 try to be displaced or deformed in a direction in which the metal member 20 and the metal member 30 are vertically separated from each other when the semiconductor element 40a fails.

  FIG. 17 is a schematic sectional view illustrating a semiconductor element module SM2 according to a comparative example. The semiconductor element module SM2 includes the metal members 20, 30 housed in the case 60, and the semiconductor elements 40a and 40b. The semiconductor elements 40a and 40b are arranged between the metal member 20 and the metal member 30. The inside of the case 60 is filled with a resin member 70, and the semiconductor elements 40 a and 40 b are sealed between the metal member 20 and the metal member 30. Further, as shown in FIG. 17, the semiconductor element module SM2 does not include the reinforcing member 50. Also, the first connection conductor 90 joined to the reinforcing member 50 is not included. Similarly, neither the second connection conductor nor the 95 joined to the reinforcing member 50 is included.

  In FIG. 17, for example, if one of the semiconductor elements 40 is short-circuited, the conduction between the metal member 20 and the metal member 30 becomes conductive. For example, assuming that the semiconductor element 40a has a short-circuit fault, the current flowing through the semiconductor element module SM2 concentrates on the semiconductor element 40a when the current of the other normal semiconductor element 40b is interrupted. Alternatively, since the conduction resistance of the semiconductor element 40a is lower than the conduction resistance (channel resistance) of the other normal semiconductor element 40b, the current flowing through the semiconductor element module SM2 concentrates on the semiconductor element 40a. In any case, an overcurrent flows through the semiconductor element 40a, for example, a bonding member provided between the semiconductor element 40a and the metal member 20 or 30, and a part of the semiconductor element 40a is melted by Joule heat, Vaporize. Thus, the internal pressure of the resin member 70 that seals the semiconductor element 40a increases.

  As a result, the resin member 70 is broken by, for example, a pressure acting in a direction of separating the metal members 20 and 30 up and down, and, for example, a crack CR extends in a lateral direction. Then, when the crack CR reaches the case 60, pressure is applied to the case 60. If the case 60 does not have the strength to withstand the pressure, the semiconductor element module SM2 may be explosively damaged.

  On the other hand, the semiconductor element module SM1 according to the embodiment has the reinforcing member 50 surrounding the metal members 20 and 30. A material having higher strength than the case 60 and the resin member 70 is used for the reinforcing member 50. Here, the strength is, for example, a value obtained by dividing a tensile load at the time of material breakage by a sectional area of the material (initial sectional area or sectional area at break). Further, the tensile strength or the compressive strength of the material may be used. For the reinforcing member 50, for example, a metal material having higher strength than a resin member is used.

  Further, it is desirable that the reinforcing member 50 has higher toughness than the resin member 70. "High toughness" means that both the strength (tensile strength) and ductility of the material are large, and examples of the material having high toughness include a metal material. The reinforcing member 50 contains, for example, iron, stainless steel, or aluminum as a main component.

  For example, when a metal member is used for the reinforcing member 50, the toughness is higher than that of the case 60 and has high ductility. Therefore, the reinforcing member 50 subjected to the internal pressure is deformed so as to extend vertically starting from the crack CR. That is, the reinforcing member 50 is flexibly deformed without breaking due to its ductility. For this reason, the crack CR is prevented from reaching the case 60, and the force applied to the resin member 75 that covers the outside of the reinforcing member 50 and the case 60 is reduced.

  Further, by forming the reinforcing member 50 in a box shape, when the metal member 20 and the metal member 30 are displaced or deformed in a direction in which they are vertically separated from each other, the displacement and deformation can be suppressed.

  As described above, since a material that can withstand the internal pressure of the resin member 70 at the time of failure is used for the reinforcing member 50, explosive damage due to a short circuit failure of the semiconductor element 40 can be avoided.

  Note that the reinforcing member 50 may be arranged so that a part thereof contacts the inner surface of the case 60. That is, the resin member 75 provided between the reinforcing member 50 and the case 60 may be omitted. The reinforcing member 50 is arranged, for example, so as to be relatively movable with respect to the case 60. Thus, it is possible to prevent the stress caused by the deformation of the reinforcing member 50 from being applied to the case 60. That is, even if the reinforcing member 50 is in contact with the inner surface of the case 60, the stress applied to the case can be absorbed by forming the structure such that the reinforcing member 50 can be deformed along the inner surface of the case 60.

  Furthermore, if the resin member 70 and the resin member 75 completely seal the reinforcing member 50 and electrical insulation can be ensured, the case 60 may be omitted with the outer resin member 75 as the outermost periphery. Can also.

  Such an explosion-proof structure is simpler than, for example, an explosion-proof structure that covers the entire semiconductor device 1, and can be realized at low cost. In addition, it contributes to downsizing of the semiconductor device 1.

  Next, the operation of the semiconductor device according to the present embodiment when current is supplied will be described. As described above, the emitter-side current IE passes through the path of the semiconductor element 40 → the metal member 30 → the first connection conductor 90 → the reinforcing member 50 → the second connection conductor 95 → the emitter conductor 100 → the emitter terminal connection portion 100T.

  The first connection conductor 90 and the second connection conductor 95 of the path components of the emitter-side current IE are formed using a nichrome material or a 42 alloy. These materials have much higher volume resistivity than good electrical conductive materials such as copper and aluminum. Conversely, the conductivity is much smaller.

In general, a cross-sectional area S [m ² ] of a cross section perpendicular to a direction in which a current flows in a conductor and a DC resistance Rdc [Ω] of a conductor having a length (current path length) L [m] are roughly expressed by the following equations. It is determined.
Rdc = ρ0 × L / S [Ω] (ρ0: Volume resistivity [Ω · m])

  Since the first connection conductor 90 and the second connection conductor 95 have a large volume resistivity, the DC resistance also has a large value. In FIG. 9, the first connection conductor 90 and the second connection conductor 95 are connected in series in an electric circuit. The semiconductor element 40 at the time of the short circuit can be simply regarded as the resistor 40S. The electric circuit at the time of the short circuit is considered as a series circuit including the first connection conductor 90, the second connection conductor 95, and the assumed resistor 40S.

  The combined resistance of the series circuit is the sum of the respective resistances of the first connection conductor 90, the second connection conductor 95, and the assumed resistor 40S. As a result, when the resistance value of each of the first connection conductor 90 and the second connection conductor 95 becomes relatively large with respect to the resistance value of the assumed resistor 40S, the combined resistance also increases.

  The current generated when the semiconductor element 40 is short-circuited is inversely proportional to the circuit resistance value. Therefore, when the combined resistance of the circuit increases, the short-circuit current decreases.

In general, when a current I (A) flows through a conductor having a DC resistance Rdc [Ω], the generated energy (Joule heat) during the energization time t (s) is roughly determined by the following equation.
Q = Rdc × I ² × t [J]

  Therefore, when the short-circuit current I decreases, the generated energy Q also decreases. The first connection conductor 90 and the second connection conductor 95 in the present embodiment act as a current limiting resistor of the circuit, and an effect of reducing generated energy can be expected by current limitation at the time of short circuit.

  The effect of suppressing the generated Joule heat of the semiconductor element 40 by the first connection conductor 90 and the second connection conductor 95 acts simultaneously with the effect of preventing the semiconductor element 40 from being damaged by the reinforcing member 50 described above. That is, a synergistic effect can be expected. Breakage can be avoided even when a larger short-circuit energy is generated as compared with the case where only one of them exists.

  With respect to the first connection conductor 90 and the second connection conductor 95 of the present embodiment, the shape and dimensions are virtually set, and the DC electric resistance Rdc is estimated. At the same time, the heat capacity Cp (J / K) of both conductors is estimated. The estimated conditions and results are as follows.

[Common Items]
・ Material used: Nickel chrome alloy, Class 1 ・ Volume resistivity: ρ0 = 108 (μΩcm)
-Specific heat capacity: Cp = 0.503 (J / gK)
-Density: γ = 8.14 (g / cm3)

[First connection conductor 90]
・ Cross section: circular with a diameter of 0.8 (cm) ・ Length: 0.6 (cm)
・ DC resistance: Rdc = 0.13 (mΩ)
-Mass: w = 2.45 (g)
・ Heat capacity: C = 1.23 (J / K)

[Second connection conductor 95]
・ Cross section: 0.4 (cm) square on each side ・ Length: 2 (cm)
DC resistance: Rdc = 1.35 (mΩ)
-Mass: w = 2.6 (g)
-Heat capacity: C = 1.31 (J / K)

The first connection conductor 90 and the second connection conductor 95 can be regarded as resistors connected in series in terms of an electric circuit, and the DC resistance and heat capacity can be treated as a sum. The sum is:
[Total value of first connection conductor 90 and second connection conductor 95]
DC resistance: Rdc = 1.48 (mΩ)
・ Heat capacity: C = 2.54 (J / K)

  As for the DC resistance, the total value of the first connection conductor 90 and the second connection conductor 95 is about 1.5 mΩ. The semiconductor element 40 at the time of the short circuit can be simply regarded as the resistor 40S. When a short circuit occurs, the assumed resistor 40S, the first connection conductor 90, and the second connection conductor 95 form a series circuit. Assuming that the DC resistance of the assumed resistor 40S is on the order of 1 mΩ, the total resistance of the first connection conductor 90 and the second connection conductor 95 is preferably on the order of the DC resistance of the assumed resistor 40S.

  If the combined resistance of the first connection conductor 90 and the second connection conductor 95 is much smaller than the assumed resistor 40S, the combined resistance will not be so large, and the Joule heat suppression effect due to the current limiting effect cannot be sufficiently expected. .

  Conversely, if the combined resistance of the first connection conductor 90 and the second connection conductor 95 is much larger than the deemed resistor 40S, the Joule heat suppression effect due to the current limiting effect increases, but the Joule heat is reduced during normal operation. What happens even at times is a problem. In this case, even during normal operation, the emitter current IE generates large Joule heat due to the combined resistance of the first connection conductor 90 and the second connection conductor 95. This leads to a reduction in the efficiency of the device, and in some cases, it is necessary to add a mechanism for dissipating heat.

  The total resistance of the first connection conductor 90 and the second connection conductor 95 of this embodiment is estimated to be about 1.5 mΩ, which is the same order as the assumed DC resistance of the assumed resistor 40S of 1 mΩ. It goes without saying that the DC resistance can be freely set by changing the material used for the conductor, the cross-sectional shape, and the length. However, if a good conductor material such as copper or aluminum is used as the material to be used, measures such as significantly reducing the cross-sectional area of the conductor and significantly increasing the length of the conductor are necessary to achieve the target resistance value. Become. In that case, another problem such as an increase in parasitic inductance or a lack of strength emerges, which is not preferable.

  In the above, the trial calculation results of the heat capacity were shown together with the DC resistance. Joule heat generated by a large current at the time of a short circuit causes the first connection conductor 90 and the second connection conductor 95 to increase in temperature.

  If the heat capacity of each of the first connection conductor 90 and the second connection conductor 95 is extremely small, the temperature rise due to the generated Joule heat may affect various characteristics due to the temperature characteristics of the conductor, or in an extreme case may cause burnout. There is also a risk of connection.

  As described above, the heat capacity of the first connection conductor 90 was calculated to be 1.23 (J / K), and the heat capacity of the second connection conductor 95 was calculated to be 1.31 (J / K). As in the case of the DC resistance, it is needless to say that the heat capacity can be freely set by changing the material used for the conductor, the cross-sectional shape, and the length.

  Regarding the first connection conductor 90 and the second connection conductor 95, the DC resistance is inversely proportional to the conductor cross-sectional area, and the heat capacity is proportional to the conductor cross-sectional area. However, by appropriately setting the material and shape, it is sufficiently possible to set the DC resistance and the heat capacity to target values.

  According to the present embodiment, the synergistic effect of the effect of preventing the semiconductor element 40 from being damaged by the reinforcing member 50 and the effect of reducing the Joule heat due to the current limitation of the first connection conductor 90 and the second connection conductor 95 causes a large energy when the semiconductor module SM1 is short-circuited. Also when damage occurs, breakage can be avoided.

[2. Second Embodiment]
[2-1. Constitution]
Hereinafter, the semiconductor device according to the present embodiment will be described with reference to FIG. FIG. 10 is a perspective view showing a reinforcing member 50A that is a component of the semiconductor device according to the second embodiment. Portions other than the not-shown reinforcing member 50A are the same as in the first embodiment, and a description thereof will be omitted.

  In the present embodiment, a protrusion 50T is formed near the opening of the reinforcing member 50A. The protrusion 50T of the reinforcing member 50A has the same shape as the second connection conductor 95 in the first embodiment. In the first embodiment, the reinforcing member 50 and the second connection conductor 95 are configured as separate components, but in the present embodiment, the second connection conductor 95 is formed integrally with the reinforcement member 50.

[2-2. Effect]
With this configuration, the number of components of the semiconductor module SM1 can be reduced. Furthermore, since the step of joining the reinforcing member 50 and the second connection conductor 95 is not required at the stage of assembling the semiconductor module SM1, the semiconductor module SM1 can be configured more simply.

  In the present embodiment, by forming the protrusion 50T integrally with the reinforcing member 50A, the reinforcing member 50A and the protrusion 50T are made of the same material. When the reinforcing member 50A is made of stainless steel, the protrusion 50T is also made of stainless steel.

  The volume resistivity of stainless steel is 71 (μΩ · cm). (SUS304 alloy) Although it is smaller than the above-mentioned nickel chromium alloy type 1, it is much larger for copper and aluminum. For this reason, in this embodiment, even when the reinforcing member 50A is made of, for example, stainless steel, it is possible to expect a reduction in short-circuit energy due to the current limiting effect of the DC resistance value of the protrusion 50T.

[3. Third Embodiment]
[3-1. Constitution]
Hereinafter, the semiconductor device according to the present embodiment will be described with reference to FIG. FIG. 11 is a perspective view showing a second metal member 30A that is a component of the semiconductor element module according to the third embodiment. Portions other than the not-shown second metal member 30A are the same as those in the first embodiment, and a description thereof will be omitted.

  In the present embodiment, a protrusion 30T is formed near the center of the end face of the second metal member 30A. The protrusion 30T of the second metal member 30A has the same shape as the first connection conductor 90 in the first embodiment. In the first embodiment, the second metal member 30 and the first connection conductor 90 are configured as separate components, and are joined at an assembling stage. It can be said that the second metal member 30A in the present embodiment is formed by integrating the second metal member 30 of the first embodiment and the first connection conductor 90 as one component.

[3-2. Effect]
With this configuration, the number of components of the semiconductor module SM1 can be reduced. Furthermore, since the step of joining the second metal member 30 and the first connection conductor 90 is not required at the stage of assembling the semiconductor module SM1, the semiconductor module SM1 can be configured more simply.

  In the present embodiment, by forming the protrusion 30T integrally with the second metal member 30A, the second metal member 30A and the protrusion 30T are made of the same material. When the protrusion 30T is formed using a nickel-chromium alloy, the entire second metal member 30A is formed from a nickel-chromium alloy.

  Most of the heat generated from the semiconductor element 40 is transferred to the cooling member 10 via the first metal member 20. Since the amount of heat radiated from the semiconductor element 40 to the outside via the second metal member 30A is small, even if the second metal member 30A is formed without using copper or aluminum having a high thermal conductivity, the heat is radiated. The effect on the properties is slight.

  In the present embodiment, for example, the second metal member 30A can be made of stainless steel instead of the nickel-chromium alloy. As in the description of the second embodiment, by forming the second metal member 30A of a nickel chrome alloy, stainless steel, or the like, it is possible to expect a reduction in short-circuit energy due to a current limiting effect of the DC resistance value of the protrusion 30T.

  FIG. 12 is a view showing a part of the assembly procedure of the semiconductor module of the third embodiment. First, a group of components sandwiched between the first metal member 20 and the second metal member 30A is joined together to assemble the subassembly SA1. The bonding method at this time is, for example, solder bonding.

  The subassembly SA1 is inserted into the reinforcing member 50B having the through hole 50H. At this time, the tip of the projection 30T formed on the second metal member 30A of the sub-assembly SA1 is inserted into the through hole 50H of the reinforcing member 50B, and the inserted portion is joined. The joining method at this time is, for example, welding. In the case of welding, the welding electrode is applied from outside the reinforcing member 50B.

  When the second metal member 30A and the reinforcing member 50B of the subassembly SA1 are made of the same material, for example, stainless steel, the same type of material is joined, and the joining is more reliably performed than when joining different materials. it can. Finally, the case 60 is mounted, and further, a resin member (not shown) is applied to complete the sub-module assembly.

[4. Fourth embodiment]
Hereinafter, the semiconductor device according to the present embodiment will be described with reference to FIG. FIG. 13 is a three-view drawing showing a second metal member 30B, which is a constituent member, of the semiconductor element module according to the fourth embodiment. Portions other than the second metal member 30B (not shown) are the same as those of the third embodiment, and thus description thereof is omitted.

  In this embodiment, the projection 30U is integrally formed on the second metal member 30B, similarly to the third embodiment in which the projection 30T is integrally formed on the second metal member 30A. The projection 30U of the present embodiment has a band shape having a width larger than the thickness, and has a shape having a substantially U-shaped curved portion in a longitudinal direction, not a simple straight line.

  In the present embodiment, as in the third embodiment, it is possible to expect a reduction in short-circuit energy due to a current limiting effect by the DC resistance value of the projection 30U. In the present embodiment, the shape of the projection 30U is provided with a substantially U-shaped curved portion in the length direction, so that the effective path length can be increased. As a result, the DC resistance value of the projection is increased. Thus, the current limiting and short-circuit energy reduction effects can be further increased.

  Since the protrusion 30U has a shape in which a substantially U-shaped curved portion is provided in the length direction, a large stress is generated in the second electrode member 30B at the time of short circuit, and the stress is transmitted to the protrusion 30U. In particular, the tip of the projection is joined to the reinforcing member 50, and a large stress is also generated at the joint.

  In the present embodiment, a stress relaxation effect can be expected at the substantially U-shaped curved portion of the projection 30U. As a result, the stress generated at the joint with the reinforcing member 50 at the tip of the projection 30U can be reduced, and the reliability of the joint is further improved.

  FIG. 14 is a view showing a part of the assembly procedure of the semiconductor module of the fourth embodiment. First, a group of components sandwiched between the first metal member 20 and the second metal member 30B is joined together to assemble the subassembly SA2. The bonding method at this time is, for example, solder bonding.

  The subassembly SA2 is inserted into the reinforcing member 50C having the square through hole 50K. At this time, the distal end of the projection 30U formed on the second metal member 30B of the subassembly SA2 is inserted into the through hole 50K of the reinforcing member 50C, and the inserted portion is joined. The joining method at this time is, for example, welding or the like. In the case of welding, the welding electrode is applied by abutting from the outside of the reinforcing member 50C.

  When the metal member 30B and the reinforcing member 50C of the subassembly SA2 are made of the same material, for example, stainless steel, the same kind of material is joined, and the joining can be performed more reliably than the case of joining different kinds of materials. Finally, the case 60 is mounted, and further, a resin member (not shown) is applied to complete the sub-module assembly.

[5. Fifth Embodiment]
Hereinafter, the semiconductor device according to the present embodiment will be described with reference to FIG. FIG. 15 is a diagram showing a first connection conductor, which is a component of the semiconductor module SM1 shown in the first embodiment. In the present embodiment, the first connection conductor 90P is a linear conductor having a circular cross section, and has a configuration in which a plating layer 90S is applied to a base material 90B by surface treatment or the like. Although not shown, a plating layer 90S may be provided on both end surfaces of the conductor.

  In FIG. 15, a base material 90B is made of a material having a large volume resistivity, such as a nickel-chromium alloy. On the other hand, the plating layer 90S is made of a material having a small volume resistivity such as copper.

  When a current flows through the first connection conductor 90P thus configured, the electric resistance value shows a different tendency depending on the frequency of the current. In the case of DC or low frequency, current flows through both the base material 90B and the plating layer 90S. Since the cross-sectional area of the plating layer 90S is much smaller than that of the base material 90B, the resistance of the base material 90B becomes dominant. In the case of alternating current, the current tends to concentrate on the conductor surface due to the skin effect, but in the case of low frequency, the effect is small.

  The effect of the skin effect increases as the frequency increases. Since the plating layer 90S has a small cross-sectional area and a small thickness of the conductor, the influence of the skin effect is small. On the other hand, since the base material 90B has a large cross-sectional area, the influence of the skin effect becomes remarkable, and the resistance of the base material 90B increases with an increase in frequency.

  The first connection conductor 90 of the first embodiment is originally made of a material having a large volume resistivity, has a large DC resistance, and the resistance value increases as the frequency increases. The first connection conductor 90P in the present embodiment is similar to the first embodiment in that the DC resistance is large. Although the resistance of the base material 90B increases in response to the increase in the frequency, the resistance of the first connection conductor 90P in the region where the frequency is large exists because there is the plating layer 90S whose resistance does not increase significantly even when the frequency increases. The increase is smaller than in the first embodiment.

  FIG. 16 shows an analysis result of the resistance value of the first connection conductor of the present embodiment. The relationship between frequency and resistance value is shown for a conductor having a diameter of 0.8 cm and a conductor length of 5 cm. Basically, the base material 90B is made of a nickel-chromium alloy and the plating layer 90S is made of copper having a thickness of 0.05 mm (△). The case where the base material 90B was copper and there was no plating layer (●) was also analyzed.

  From DC to around 10 kHz, the configuration of the present embodiment is almost the same as the resistance value when the base material 90B is a nickel-chromium alloy base material without plating. In the configuration of the present embodiment, when the frequency exceeds 10 kHz, the degree of increase in the resistance value is smaller than that of the nickel-chromium alloy base material without plating. Become.

  When the first connection conductor 90B having the configuration according to the present embodiment is applied to the semiconductor module SM1, current limitation and short-circuit energy reduction during a short circuit can be expected depending on the resistance value of the first connection conductor 90B. This is because the frequency of the short-circuit current is assumed to be 1 kHz to 10 kHz.

  As described above, a current is generated in the first connection conductor even during normal operation. The current during normal operation has a rectangular waveform, and a current having a large current change rate is generated at the time of turn-on and turn-off due to switching of the semiconductor element 40, and the frequency of the current at that time corresponds to 1 MHz or more.

  As shown in FIG. 16, the configuration of the present embodiment can reduce the resistance value in the vicinity of 1 MHz as compared with the conductor of the nickel-chromium base material without plating. This makes it possible to relatively suppress the Joule heat generated in the conductor during turn-on and turn-off during normal operation.

  In the present embodiment, the first connection conductor 90 of the first embodiment has been described. However, the same configuration can be applied to the second connection conductor 95 and further to the reinforcing member 50. In this case, the effect of suppressing Joule heat generated in the conductor during normal operation in the semiconductor module SM is further increased.

  While some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor device 10 ... Cooling member 10T ... Collector terminal connection part 13 ... Void 15 ... Cooling fin 20, 30, 30A, 30B ... Metal member 30a ... Projection part 30T, 30U ... Projection part 40, 40a, 40b ... Semiconductor element 40B ... Back surface 40T ... Front surface 40S ... Deemed resistor 43 ... Emitter electrode 45 ... Gate electrode 50, 50A, 50B, 50C ... Reinforcement member 50H, 50K ... Through hole 50T ... Projection part 60 ... Case 70, 75 ... Resin member 80 ... Gate Terminals 90, 90B: first connection conductor 90B: base material 90S: plating layer 95: second connection conductor 100: emitter conductor 100T: emitter terminal connection CR: crack OP, OP50, OP60: opening SM1, SM2: semiconductor Module IC: Collector current IE: Emitter current

Claims (6)

A semiconductor device comprising a plurality of semiconductor element units connected in parallel,
The semiconductor element unit includes:
At least one plate-like semiconductor element is provided,
A plate-shaped first metal member that is in contact with one surface of the semiconductor element;
A second metal member that is in contact with the other surface of the semiconductor element and faces the first metal member via the semiconductor element;
A metal reinforcing member provided to surround the first metal member, the semiconductor element, and the second metal member to be stacked in the stacking direction of the second metal member;
A first connection conductor connected to the second metal member and the metal reinforcement member and having a higher electrical resistivity than the first metal member or the second metal member;
A second connection conductor having one end connected to the metal reinforcing member and having a higher electrical resistivity than the first and second metal members;
A semiconductor device comprising:   The semiconductor device according to claim 1, wherein the metal reinforcing member and the second connection conductor are a continuous member.   The semiconductor device according to claim 1, wherein the second metal member and the first connection conductor are a continuous member. The first connection conductor is a plate-shaped member, and has a substantially U-shaped curved portion on a part of the plate-shaped member;
4. The semiconductor device according to claim 1, wherein the plate-like member has a width greater than a thickness thereof. 5. The second connection conductor includes a base material disposed at a central portion, and a coating layer covering a surface of the base material,
5. The semiconductor device according to claim 1, wherein said base material is formed of a material having a large volume resistivity, and said coating layer is formed of a material having a small volume resistivity as compared with said base material.   6. The first connection conductor according to claim 1, wherein a base material is formed of a material having a large volume resistivity, and a plating layer is formed on a surface of the conductor with a material having a small volume resistivity. 3. The semiconductor device according to claim 1.