JP2014116478A - Semiconductor module, semiconductor module manufacturing method and power conversion apparatus - Google Patents

Abstract

An object of the present invention is to reduce the influence of thermal expansion of each member constituting a semiconductor module on a pressing force applied to each member constituting the semiconductor module.
A semiconductor module includes a switching element, a diode, a source electrode, a drain electrode, and a housing. The source electrode 4 has a source internal electrode 4a and a source external electrode 4b. The source internal electrode 4a and the source external electrode 4b are provided apart from each other, and the connection conductor 13 is provided between the source internal electrode 4a and the source external electrode 4b. The connection conductor 13 is a conductor made of the same material as the source internal electrode 4a and the source external electrode 4b or a conductor having a thermal expansion coefficient similar to that of the source internal electrode 4a and the source external electrode 4b, and is formed in a wire shape or a ribbon shape. Is done. The connection between the connection conductor 13 and the source internal electrode 4a (or the connection between the connection conductor 13 and the source external electrode 4b) is performed by ultrasonic bonding or resistance welding.
[Selection] Figure 1

Description

  The present invention relates to a semiconductor module that electrically connects an electrode layer and an electrode of a semiconductor element by pressure welding, a method for manufacturing the semiconductor module, and a power converter using the semiconductor module.

  In recent years, high-voltage, high-capacity IGBTs (Insulated Gate Bipolar Transistors) are used for insulated power semiconductor modules used in the fields of industrial and vehicle systems, power converters such as transformers and inverters. Has been applied. Standards for “insulated power semiconductor modules” or “Isolated power semiconductor devices” represented by this IGBT module are established in JEC-2407-2007 and IEC60747-15, respectively.

  In a general insulated power semiconductor module, a semiconductor element such as an IGBT or a diode is soldered onto a copper circuit foil of a DBC (Direct Bond Copper) substrate through an electrode layer provided on the lower surface of the semiconductor element ( For example, Non-Patent Document 1). The DBC substrate is obtained by directly bonding a copper circuit foil to an insulating plate such as ceramics.

  An aluminum wire is connected to the electrode layer provided on the upper surface of the semiconductor element by a method such as ultrasonic bonding. This aluminum wire is connected to, for example, a copper circuit foil on a DBC substrate. And the copper terminal (lead frame or bus bar) for connecting to the outside from the copper circuit foil of the DBC substrate is connected to the copper circuit foil by soldering or ultrasonic bonding. In addition, this is surrounded by a (super) engineering plastic case, which is filled with silicone gel for electrical insulation.

  Insulated power semiconductor modules using solder have problems such as lead-free soldering for compliance with RoHS (Restriction of Hazardous Substances), temperature cycle, and improvement of reliability when the power cycle is repeated.

  To solve the problem of lead-free soldering, lead-free solder materials include metal-based high-temperature solder (Bi, Zn, Au), compound-based high-temperature solder (Sn-Ag-based, Sn-Cu-based), and low-temperature sintering. Metals (Ag nanopaste) and the like have been proposed. Further, a flat pressure contact structure package has been proposed as a semiconductor module structure that does not use solder (for example, Non-Patent Documents 1 and 2).

  In the flat pressure contact structure package, electrical connection between the electrode layer of the semiconductor element and the contact terminal and electrical connection between the electrode layer of the semiconductor element and the substrate are performed by pressure contact. In a general flat pressure contact structure package, a guide for positioning a semiconductor element and a contact terminal is provided at an end of the semiconductor element. And a semiconductor element is provided on board | substrates, such as Mo, in the state which the upper surface electrode layer of the semiconductor element contacted the contact terminal. That is, the contact terminal and the substrate are provided in the semiconductor module with the semiconductor element sandwiched therebetween.

  Since the flat pressure contact structure package has a flat structure, the semiconductor element can be cooled from both sides. For this reason, in general, both sides of the flat pressure contact structure package are pressed with heat sinks to cool both sides of the flat pressure contact structure package, and the heat sink is used as a conductive member. Further, since the flat pressure contact structure package connects the semiconductor element and the electrode terminal by pressure contact, the semiconductor element is electrically and thermally connected to the outside without using solder.

  The pressure welding between the heat sink and the flat pressure welding structure package is mainly performed by the user. In the flat pressure welded structure package, the electrode post of the flat pressure welded package is designed to electrically insulate the heat sinks above and below the flat pressure welded package or press the flat pressure welded package with a leaf spring. It is necessary to make it evenly. These have know-how, and if the pressure contact is poor, the semiconductor element may be destroyed. In addition, a semiconductor module having a flat pressure contact structure requires skill to be fully used, for example, because the heat sink and the leaf spring for pressure contact prevent the miniaturization of the circuit. For these reasons, the flat type pressure contact structure package is applied to a limited apparatus, and a conventional type of insulated power semiconductor module that is easy to use is widely used instead.

  In order to improve the reliability of the temperature cycle and power cycle, it is necessary to solve the problem caused by the difference in thermal expansion of each member (semiconductor, metal, ceramics, etc.) constituting the semiconductor module. For example, when a DBC substrate and a copper base are joined by solder, or when a DBC substrate and a copper terminal are joined by solder, a shear stress acts on the solder due to a difference in thermal expansion coefficient between ceramics and copper. There is a risk of cracking. As a result, the thermal resistance between the DBC substrate and the copper base (or copper terminal) may increase, or the copper base (or copper terminal) may peel off. For the same reason, when the semiconductor element and the DBC substrate are joined with solder, there is a possibility that the solder may crack. Also, depending on the use conditions of the semiconductor module, stress may be generated at the connection portion of the aluminum wire on the semiconductor element due to the difference in thermal expansion coefficient between the semiconductor element and aluminum, and the aluminum wire may be fatigued.

  The power density of semiconductor modules is increasing year by year, and the junction temperature inside the semiconductor module is rising. As a result, the shear stress of the solder and the stress applied to the aluminum wire are increasing. Therefore, it is necessary to prevent the influence of thermal expansion from becoming apparent during the period until the design life of the semiconductor module is reached. With the advent of wide-gap semiconductor elements that can be used at high temperatures such as SiC semiconductors and GaN semiconductors, further reduction in thermal expansion is required. Further, in order to make use of the performance of semiconductor elements that can be used at high temperatures such as SiC semiconductors and GaN semiconductors, it is required to improve the reliability of semiconductor modules such as temperature cycle and power cycle.

  Therefore, in order to achieve high reliability, environmental friendliness, and convenience of the semiconductor module at the same time, it is possible to easily realize double-sided cooling without using solder bonding or wire bonding, which is advantageous in terms of heat dissipation. Insulated power modules are again in the limelight.

  As shown in FIG. 3, in the insulation displacement type power semiconductor module 22, a fastening member 19 such as a spring, a bolt, or a screw is provided on the outer periphery of the semiconductor module 22, and the coolers 16 and 18 are fastened by the fastening member 19. Uniform pressure stress is applied to the switching element 2 and the diode 3.

  The source electrode 23 which is a main electrode is provided on the source electrode layer 8 formed on the surface of the switching element 2 and the anode layer 11 formed on the surface of the diode 3. Similarly, the drain electrode 24 as the main electrode is provided on the drain electrode layer 7 formed on the surface of the switching element 2 and the cathode layer 12 formed on the surface of the diode 3. The source electrode 23 and the drain electrode 24 are provided directly or via a stress relaxation member 14 such as molybdenum (Mo) on these electrode layers 7, 8, 11, 12. The source electrode 23 and the drain electrode 24 are provided through a housing 25 provided between the coolers 16 and 18 and are connected to a circuit outside the semiconductor module 22. Then, by fastening the coolers 16 and 18 with the fastening member 19, the source electrode 23 and the drain electrode 24 are pressed in the direction of the switching element 2 (and the diode 3).

  The gate electrode 26 which is a signal electrode is provided on the gate electrode layer 10 formed on the surface of the switching element 2 and is pressed against the switching element 2. The gate electrode 26 is provided through the housing 25 and connected to a circuit outside the semiconductor module 22.

  The pressure-contact type semiconductor module 22 electrically connects the electrode layers of the switching element 2 and the diode 3 to the source electrode 23 and the drain electrode 24 without using wire bonds and solder. As a result, the semiconductor module 22 performs electrical connection between the switching element 2 and the source electrode 23 (or the drain electrode 24) without using wire bonding or solder bonding that may be a factor that determines the life of the semiconductor module. Therefore, the design life of the semiconductor module 22 can be improved.

Japanese Utility Model Publication No. 6-62549 JP-A-4-306855

IEEJ Technical Committee on High Performance and High Performance Power Devices and Power ICs, “Power Device and Power IC Handbook”, Corona, July 1996, p289, p336 Hiroshi Mori, Yasukazu Seki, “Recent Advances in Large Capacity IGBTs”, The Institute of Electrical Engineers of Japan, The Institute of Electrical Engineers of Japan, May 1998, Vol. 118 (5), pp. 274-277

  In the semiconductor module 22, the source electrode 23, the drain electrode 24, and the gate electrode 26 pass through the housing 25 and are taken out of the semiconductor module 22. Therefore, when the semiconductor module 22 is hermetically sealed, for example, the space between the housing 25 and the electrodes 23, 24, and 26 is sealed with a sealing material 17 such as brazing or high-temperature adhesive. That is, the housing 25 and the electrodes 23, 24, and 26 are fixed integrally.

  In the case where the source electrode 23 and the drain electrode 24 are fixed to the same surface of the casing 25, the coefficient of thermal expansion (for example, 7 ppm / ° C. for alumina) of the casing 25 made of ceramics and the source electrode 23 and the drain electrode 24, the stress in the lateral direction increases as the distance from the side where the source electrode 23 and the drain electrode 24 are fixed increases, and the switching element 2 and the diode 3 are applied. The pressure contact force may be non-uniform due to the temperature change of the semiconductor module 22.

  In the case of a structure in which the source electrode 23 and the drain electrode 24 are fixed to the facing housing 25 as in the semiconductor module 27 shown in FIG. 4, the housing 25, the source electrode 23, and the drain electrode formed of ceramics. Due to the difference in thermal expansion coefficient of 24, alternating stress is applied above and below the switching element 2 and the diode 3 that are in pressure contact, and the pressure contact force applied to the switching element 2 and the diode 3 is caused by the temperature change of the semiconductor module 27. May be non-uniform.

  Further, the switching element 2 (or the diode 3), the source electrode 23, and the drain electrode 24 are stacked on the basis of the difference between the thermal expansion coefficient of the casing 25 made of ceramics and the thermal expansion coefficient of the source electrode 23 and the drain electrode 24. Due to the difference between the coefficient of thermal expansion of the body and the coefficient of thermal expansion of the housing 25, the positions of the source electrode 23 and the drain electrode 24 are shifted in the pressure contact direction of the switching element 2 and the diode 3, and the pressure contact force applied to the switching element 2 and the diode 3 is increased. There is a risk of non-uniformity due to temperature changes of the semiconductor modules 22 and 27.

  In view of the above circumstances, an object of the present invention is to provide a technique that contributes to reducing the influence of thermal expansion of each member constituting a semiconductor module on the pressure contact force acting on each member constituting the semiconductor module. To do.

  One aspect of the semiconductor module of the present invention that achieves the above object includes a semiconductor element and an internal electrode that is electrically connected to an electrode layer formed in the semiconductor element, and a space in which the semiconductor element is provided Is a semiconductor module in which the semiconductor element and the internal electrode are connected by pressure contact, and a housing provided on an outer periphery of the semiconductor module, and provided through the housing And an external electrode that connects the internal electrode and a circuit outside the semiconductor module, and a connection conductor that connects the internal electrode and the external electrode.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that in the semiconductor module, the housing is formed of an inorganic insulating material.

  According to another aspect of the semiconductor module of the present invention for achieving the above object, the connection conductor is provided on both surfaces of the internal electrode and the external electrode in the semiconductor module.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that, in the semiconductor module, the connection conductor is formed in a wire shape or a ribbon shape.

  In another aspect of the semiconductor module of the present invention that achieves the above object, in the semiconductor module, the connection conductor is formed of a material having a thermal expansion coefficient comparable to that of the internal electrode or the external electrode. It is a feature.

  In another aspect of the semiconductor module of the present invention that achieves the above object, in the semiconductor module, the internal electrode and the external electrode are separated by a distance that does not interfere with thermal expansion in an operating temperature range of the semiconductor module. It is characterized by being provided.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that in the semiconductor module, the internal electrode is made of a material having a thermal expansion coefficient close to that of the semiconductor element. .

  According to another aspect of the semiconductor module of the present invention that achieves the above object, in the semiconductor module, a metal plating layer is formed on a joint surface of the internal electrode with the connection conductor.

  According to another aspect of the semiconductor module of the present invention that achieves the above object, in the semiconductor module, the bonding between the internal electrode and the connection conductor and the bonding between the external electrode and the connection conductor are ultrasonic bonding or resistance welding. It is characterized by performing by.

  According to one aspect of the method for manufacturing a semiconductor module of the present invention, which achieves the above object, a semiconductor element, an internal electrode electrically connected to an electrode layer formed on the semiconductor element, and a space apart from the internal electrode are provided. An external electrode that connects the internal electrode and an external circuit, a connection conductor that electrically connects the internal electrode and the external electrode, and a housing through which the external electrode is inserted. And a method of manufacturing a semiconductor module in which a space in which the semiconductor element is provided is hermetically sealed with an inert gas, and the semiconductor element and the internal electrode are connected by pressure contact, the internal electrode and the external electrode being It is characterized in that it is joined by the connection conductor, the semiconductor element is provided on the internal electrode, and the internal electrode terminal is pressed in the direction of the semiconductor element.

  In addition, a power conversion device of the present invention that achieves the above object includes any one of the above semiconductor modules.

  According to the above invention, it can contribute to reducing the influence of the thermal expansion of each member which comprises a semiconductor module with respect to the press-contact force which acts on each member which comprises a semiconductor module.

2A is a top view of the semiconductor module according to the first embodiment of the present invention, and FIG. 2B is a cross-sectional view of the main part of the semiconductor module according to the first embodiment of the present invention. (A) The top view of the semiconductor module which concerns on 2nd Embodiment of this invention, (b) It is principal part sectional drawing of the semiconductor module which concerns on 2nd Embodiment of this invention. It is principal part sectional drawing of the semiconductor module which concerns on a prior art. It is principal part sectional drawing of the semiconductor module which concerns on a prior art.

  A semiconductor module, a method for manufacturing a semiconductor module, and a power converter according to the present invention will be described in detail with reference to the drawings. 1 and 2 schematically show a semiconductor module according to an embodiment of the present invention, and the dimensional ratio on the drawing does not necessarily match the actual dimensional ratio.

(First embodiment)
[Semiconductor module]
As shown in FIGS. 1A and 1B, the semiconductor module 1 according to the first embodiment of the present invention includes a switching element 2, a diode 3, a source electrode (emitter electrode) 4, and a drain electrode (collector electrode) 5. And a housing 6.

  The switching element 2 is a semiconductor element such as an IGBT or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). A drain electrode layer 7 electrically connected to the drain electrode 5 is provided on the lower surface of the switching element 2. A source electrode layer 8 electrically connected to the source electrode 4 and a gate electrode layer 10 electrically connected to the gate electrode 9 are provided on the upper surface of the switching element 2. In the description of the embodiment, for convenience, the upper surface and the lower surface are used, but the vertical direction does not limit the present invention.

  The diode 3 is a semiconductor element such as FWD (Free Wheeling Diode). An anode layer 11 electrically connected to the source electrode 4 is provided on the upper surface of the diode 3, and a cathode layer 12 electrically connected to the drain electrode 5 is provided on the lower surface of the diode 3.

  The source electrode 4 has a source internal electrode 4a and a source external electrode 4b. The source internal electrode 4a and the source external electrode 4b are provided at a distance that does not interfere with each other due to thermal expansion of the source internal electrode 4a and the source external electrode 4b in the operating temperature range of the semiconductor module 1. For example, when the source internal electrode 4a and the source external electrode 4b are made of copper and the length of the housing 6 is 100 mm, when used up to 225 ° C., the distance at room temperature is 0.2 mm or more (about 0.25 mm). is necessary. The source internal electrode 4 a and the source external electrode 4 b are electrically connected by the connection conductor 13. At this time, heat generation due to the resistance of the connection conductor 13 can be reduced by shortening the distance between the source internal electrode 4a and the source external electrode 4b.

  The source internal electrode 4a and the source external electrode 4b are made of copper, aluminum, copper, or an alloy containing aluminum. The source internal electrode 4a (or source external electrode 4b) is made of a material having a thermal expansion coefficient close to that of the material constituting the housing 6 or the switching element 2 (or diode 3) (for example, tungsten (W) or molybdenum (Mo)). Alternatively, the stress generated by the difference in coefficient of thermal expansion between the switching element 2 (or the housing 6) and the source internal electrode 4a can be further relaxed. In this case, if at least a portion of the source internal electrode 4a to which the connection conductor 13 is bonded is plated with a metal such as nickel (Ni) or gold (Au), the source internal electrode 4a and the connection conductor 13 can be easily bonded. The reliability of the joint between 4a and the connecting conductor 13 is also improved.

  The source internal electrode 4a is provided on the source electrode layer 8 of the switching element 2 and the anode layer 11 of the diode 3 via a stress relaxation member 14 formed of tungsten, molybdenum or the like. A cooler 16 is provided on the upper surface of the source internal electrode 4 a via an insulating plate 15. The source internal electrode 4a is pressed in the direction of the switching element 2 (and the diode 3) by the cooler 16.

  The source external electrode 4b is provided through the housing 6 and electrically connects the source internal electrode 4a and an external circuit (not shown). When the semiconductor module 1 is hermetically sealed, the space between the housing 6 and the source external electrode 4 b is sealed with a sealing material 17 such as brazing or high-temperature adhesive, and the source external electrode 4 b is integrated with the housing 6. Fixed.

  The connection conductor 13 is a conductor having the same material as the source internal electrode 4a and the source external electrode 4b or a thermal expansion coefficient similar to those of these electrodes, and is formed in a wire shape or a ribbon shape, for example. The connection between the connection conductor 13 and the source internal electrode 4a (or the connection between the connection conductor 13 and the source external electrode 4b) is performed by ultrasonic bonding or resistance welding. In addition, you may join the junction part of the connection conductor 13 and the source internal electrode 4a (or source external electrode 4b) with high-temperature joining materials, such as silver nano paste, and solder. The distance between the source internal electrode 4a and the source external electrode 4b is changed by thermal expansion by forming the length of the connection conductor 13 so that the tension applied to the connection conductor 13 is low in the operating temperature range of the semiconductor module. Also, it is possible to suppress the influence of the thermal expansion of the source external electrode 4b from acting on the source internal electrode 4a. That is, by providing the connection conductor 13 between the source internal electrode 4a and the source external electrode 4b, the source internal electrode 4a and the source against the pressure contact force that acts in the direction in which the source internal electrode 4a presses the switching element 2 (or the diode 3) is applied. The influence of the stress change due to the thermal expansion of the external electrode 4b is mitigated. In addition, it is desirable that the connection conductor 13 has a structure in which the mutual inductance is canceled out so that the parasitic inductance in the connection conductor 13 portion does not increase.

  The drain electrode 5 has a drain internal electrode 5a and a drain external electrode 5b. The drain internal electrode 5a and the drain external electrode 5b are provided at a distance apart so as not to interfere with each other due to thermal expansion of the drain internal electrode 5a and the drain external electrode 5b in the operating temperature range of the semiconductor module 1. The drain internal electrode 5 a and the drain external electrode 5 b are electrically connected by the connection conductor 13.

  Similar to the source internal electrode 4a and the source external electrode 4b, the drain internal electrode 5a and the drain external electrode 5b are formed of copper, aluminum, copper, an alloy containing aluminum, or the like. Further, the drain internal electrode 5a (or the drain external electrode 5b) is formed using a material having a thermal expansion coefficient close to that of the material constituting the casing 6 or the switching element 2 (or the diode 3), and the switching element 2 (or the casing). The stress caused by the difference in coefficient of thermal expansion between the body 6) and the drain internal electrode 5a may be relaxed. In this case, at least a portion of the drain internal electrode 5a to which the connection conductor 13 is joined is plated with a metal such as nickel (Ni) or gold (Au).

  The drain internal electrode 5 a is provided on the drain electrode layer 7 of the switching element 2 and the cathode layer 12 of the diode 3. A cooler 18 is provided on the lower surface of the drain internal electrode 5 a via an insulating plate 15. The drain internal electrode 5a is pressed against the switching element 2 direction (and the diode 3 direction) by the cooler 18.

  The drain external electrode 5b is provided through the housing 6 and electrically connects the drain internal electrode 5a and an external circuit (not shown). Similar to the source external electrode 4 b, the drain external electrode 5 b is fixed integrally with the housing 6 by the sealing material 17.

  The gate electrode 9 has a gate internal electrode 9a and a gate external electrode 9b. The gate internal electrode 9a and the gate external electrode 9b are provided at a distance that does not interfere with each other due to thermal expansion of the gate internal electrode 9a and the gate external electrode 9b in the operating temperature range of the semiconductor module 1. The gate internal electrode 9 a and the gate external electrode 9 b are electrically connected by the connection conductor 13.

  Similarly to the source internal electrode 4a and the source external electrode 4b, the gate internal electrode 9a and the gate external electrode 9b are formed of copper, aluminum, copper, an alloy containing aluminum, or the like. Further, the gate internal electrode 9a (or the gate external electrode 9b) is formed using a material having a thermal expansion coefficient close to that of the material constituting the casing 6 or the switching element 2 (or the diode 3), and the switching element 2 (or the casing). The stress caused by the difference in coefficient of thermal expansion between the body 6) and the gate internal electrode 9a may be relaxed. In this case, at least a portion of the gate internal electrode 9a to which the connection conductor 13 is joined is plated with a metal such as nickel (Ni) or gold (Au).

  The gate internal electrode 9 a is provided on the gate electrode layer 10 of the switching element 2. The gate internal electrode 9a is pressed in the direction of the switching element 2 by a pressing member (not shown).

  The gate external electrode 9b penetrates the housing 6 and electrically connects the gate internal electrode 9a and an external circuit (not shown). Similarly to the source external electrode 4 b, the gate external electrode 9 b is fixed integrally with the housing 6 by the sealing material 17.

  The coolers 16 and 18 are fixed by fastening members 19 such as bolts and nuts (or screws). Refrigerant paths 16a and 18a are formed in the cooler 16 and the cooler 18, respectively, and the semiconductor module 1 (the switching element 2 and the diode 3) is cooled by the refrigerant flowing through the refrigerant paths 16a and 18a. A housing 6 is provided between the coolers 16 and 18 and on the side of the semiconductor module 1. When the semiconductor module 1 is hermetically sealed, the sealing members 20 are respectively provided between the cooler 16 (and the cooler 18) and the housing 6, and the cooler 16 (and the cooler 18) and the housing 6 are provided. The connecting portion is sealed.

  The housing 6 is made of resin or an inorganic insulating material. When an inorganic insulating material such as a ceramic material is used as the housing 6, the airtightness of the semiconductor module 1 can be improved. Then, by filling the hermetically sealed semiconductor module 1 with an inert gas such as nitrogen, for example, when the semiconductor module 1 is operated at a temperature exceeding 200 ° C., the semiconductor module 1 such as copper or aluminum is Oxidation of the constituent materials (the source electrode 4 and the drain electrode 5) is suppressed, and the operation reliability of the semiconductor module 1 is improved.

[Semiconductor module manufacturing method]
A method for manufacturing the semiconductor module 1 according to the first embodiment of the present invention will be described with reference to FIG.

  First, the source external electrode 4b and the gate external electrode 9b are inserted into the housing 6, the respective insertion portions are sealed with the sealing material 17, and the source external electrode 4b and the gate external electrode 9b are fixed integrally to the housing 6. To do. Similarly, the drain external electrode 5 b is inserted into the housing 6, the insertion portion of the drain external electrode 5 b is sealed with the sealing material 17, and the drain external electrode 5 b is fixed integrally to the housing 6.

  Next, a connection conductor is connected to each external electrode (source external electrode 4b, drain external electrode 5b, gate external electrode 9b) and internal electrodes corresponding to the external electrodes (source internal electrode 4a, drain internal electrode 5a, gate internal electrode 9a). 13 are joined, and each external electrode and the internal electrode corresponding to this external electrode are electrically connected through the connection conductor 13.

  Then, the drain internal electrode 5 a is provided in the cooler 18 through the insulating plate 15. The switching element 2 and the diode 3 are provided on the drain internal electrode 5 a, and the source internal electrode 4 a is provided on the source electrode layer 8 of the switching element 2 and the anode layer 11 of the diode 3 via the stress relaxation member 14. A gate internal electrode 9 a is provided on the gate electrode layer 10 of the switching element 2.

  The cooler 16 is provided on the source internal electrode 4a through the insulating plate 15, the cooler 16 and the cooler 18 are fastened by the fastening member 19, and the source internal electrode 4a and the drain internal electrode 5a are connected to the switching element 2 (and the diode 3). ) Press in the direction.

(Second Embodiment)
[Semiconductor module]
The semiconductor module 21 according to the second embodiment of the present invention will be described in detail with reference to FIG. The semiconductor module 21 according to the second embodiment is the same as the semiconductor module 1 according to the first embodiment except that the internal electrode (source internal electrode 4a, drain internal electrode 5a, gate internal electrode 9a) and external electrode (source external electrode 4b, In this embodiment, connection conductors 13 for electrically connecting the drain external electrode 5b and the gate external electrode 9b) are provided on a plurality of surfaces of each internal electrode and external electrode. Accordingly, the same components as those of the semiconductor module 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Moreover, since the manufacturing method of the semiconductor module 21 which concerns on 2nd Embodiment is the same as the manufacturing method of the semiconductor module 1 which concerns on 1st Embodiment, the description is abbreviate | omitted.

  As shown in FIGS. 2A and 2B, the semiconductor module 21 includes a switching element 2, a diode 3, a source electrode 4, a drain electrode 5, and a housing 6.

  The source internal electrode 4 a of the source electrode 4 is provided on the source electrode layer 8 (and the anode layer 11 of the diode 3) of the switching element 2 via a stress relaxation member 14. The connection conductors 13 and 13 are joined to the upper and lower surfaces of the source internal electrode 4a and the source external electrode 5b, and the source internal electrode 4a is electrically connected to the source external electrode 4b through the connection conductors 13 and 13.

  The drain internal electrode 5 a of the drain electrode 5 is provided on the drain electrode layer 7 of the switching element 2 (and the cathode layer 12 of the diode 3). The connection conductors 13 and 13 are joined to the upper and lower surfaces of the drain internal electrode 5a and the drain external electrode 5b, and the drain internal electrode 5a is electrically connected to the drain external electrode 5b through the connection conductors 13 and 13.

  The gate internal electrode 9 a of the gate electrode 9 is provided on the gate electrode layer 10 of the switching element 2. The connection conductors 13 and 13 are joined to the upper and lower surfaces of the gate internal electrode 9a and the gate external electrode 9b, and the gate internal electrode 9a is electrically connected to the gate external electrode 9b through the connection conductors 13 and 13.

  By minimizing the region where the connection conductor 13 is joined, the semiconductor module 21 can be reduced in size and inductance. On the other hand, if the joint area to which the connection conductor 13 is connected is small, the number of connection conductors 13 that can be applied is limited, and parasitic resistance and parasitic inductance are generated there. The parasitic resistance becomes Joule loss at that portion and causes power loss in the semiconductor module 21 and heat generation factors of the switching element 2 and the diode 3. Further, since the parasitic inductance causes a surge voltage at the time of switching of the switching element 2, it is desired to be as small as possible. Therefore, by providing the connection conductors 13 on both surfaces of the internal electrode (and the external electrode), it is possible to obtain a double connection area with the same junction area as compared with the semiconductor module 1 according to the first embodiment. As a result, the parasitic resistance in the connecting conductor 13 portion can be halved compared to the semiconductor module 1 according to the first embodiment, and the parasitic inductance is reduced.

  As described above, the specific embodiment is described as an example. According to the semiconductor module of the present invention, the internal electrode connected to the electrode layer of the semiconductor element, and the external electrode connecting the internal electrode and the external circuit Are provided apart from each other, so that a uniform pressure contact force can be applied to each semiconductor element in the semiconductor module. In other words, the external electrode fixed to the housing and the internal electrode that press-contacts the semiconductor element are separately provided, so that the displacement of the position of the external electrode and the internal electrode due to the difference in thermal expansion affects the press-contact of the semiconductor element. Can be reduced. As a result, each semiconductor element operates uniformly, and each semiconductor element can be operated with uniform heat loss.

  Further, since the internal electrode is not affected by the thermal expansion of the external electrode (and the housing), the positional accuracy between the internal electrode and the electrode layer of the semiconductor element electrically connected to the internal electrode is also improved.

  Thus, the semiconductor module of the present invention can reduce the influence of the thermal expansion of the members constituting the semiconductor module on the pressure contact between the semiconductor element and the electrode. Therefore, even when a wide gap semiconductor such as a SiC semiconductor or a GaN semiconductor is used as the semiconductor element, the pressure contact force between the semiconductor element and the electrode can be made more uniform in the operating temperature range of the semiconductor module. As a result, the SiC semiconductor or the GaN semiconductor can be operated at a high temperature exceeding 200 ° C., and the power density of the semiconductor module can be improved.

  Furthermore, by providing an external electrode fixed to the housing, a semiconductor element, and an internal electrode constituting the stacked body, the coefficient of thermal expansion of the stacked body stacked in the direction in which the semiconductor element is pressed and the heat of the housing Even when the positions of the external electrode and the internal electrode are shifted in the pressure contact direction of the semiconductor element due to the difference in expansion coefficient, the internal electrode can press the semiconductor element with the design pressure.

  In the semiconductor module according to the related art, the external electrode and the semiconductor element may be connected with a wire. In this case, there is a case where the wire is directly wired from the semiconductor element to the terminal, and a case where the wire is once wired from the semiconductor element to the copper pattern on the DBC substrate and further connected to the external terminal from the copper pattern. In these structures, the aluminum pattern on the semiconductor element and the aluminum wire have the same thermal expansion coefficient (23 ppm / ° C.), but the aluminum pattern on the semiconductor element has a thermal expansion coefficient of the semiconductor element (thermal expansion coefficient: 3 ppm / ° C.). A strong thermal expansion coefficient mismatch occurs with the wire. Moreover, the copper pattern on the DBC substrate is affected by the ceramics (thermal expansion coefficient: 5-7 ppm / ° C.) used for the DBC substrate, and even if copper wiring is applied to this, the thermal expansion coefficient between the wires is large. A mismatch occurs. This mismatch in coefficient of thermal expansion acts on bonding, and bonding and peeling occurs between the semiconductor element, ceramics, and copper pattern due to heat cycles and the like, which may be a factor that determines the life of the semiconductor module.

  On the other hand, if the internal electrode and the external electrode are formed of the same material and the two electrodes are joined with a connection conductor (or a conductor having a similar coefficient of thermal expansion) of the same material as these electrodes, There is no rate mismatch, and the effect of the connecting conductor junction on the life of the semiconductor module is significantly reduced compared to conventional structures. Here, having the same coefficient of thermal expansion as used herein means having a coefficient of thermal expansion such that the deformation due to the difference in thermal expansion falls within the range of the hook law. In addition, by joining the connection conductor and the internal electrode (or external electrode) by ultrasonic welding or resistance welding, since no bonding material is present in the joint, the connection conductor and internal electrode (or external electrode) can be further bonded. Can be improved.

  Further, by providing connection conductors for joining the internal electrode and the external electrode on both surfaces of the internal electrode and the external electrode, it is possible to reduce the influence of parasitic resistance and parasitic inductance associated with the connection of the connection conductor. That is, by disposing the connection conductors on both surfaces of the internal electrode and the external electrode, it is possible to reduce the loss at the joint between the internal electrode and the external electrode and improve the reliability of the joint. Further, the contact resistance is reduced, and heat generation from the joint portion of the connection conductor can be suppressed. As a result, the amplitude of the heat cycle of the semiconductor module is reduced, and the reliability of the semiconductor module is improved. In the semiconductor module according to the related art, since the electrodes formed on the opposing surfaces of the semiconductor element and the DBC substrate have different potentials, a structure in which wiring is performed from both surfaces of the electrodes cannot be taken.

  In addition, by using a material having a coefficient of thermal expansion close to that of the semiconductor element (or housing) as the material for forming the internal electrode (or external electrode), the semiconductor module is configured in the operating temperature range of the semiconductor module. The stress due to the difference in coefficient of thermal expansion between the member to be performed and the internal electrode can be reduced.

  Further, according to the method for manufacturing a semiconductor module of the present invention, the internal electrode is provided on the electrode layer of the semiconductor element after the internal electrode and the external electrode are joined by the connection conductor, thereby mechanically and electrically connecting the semiconductor element. , Thermal damage can be reduced. In other words, by joining the internal electrode (and external electrode) and the connecting conductor before providing the internal electrode in the semiconductor element, mechanical, electrical, and thermal damage caused by ultrasonic bonding, resistance welding, and the like are caused by the semiconductor. It can prevent acting on an element. In the description of the embodiment, the internal electrode and the external electrode are electrically joined after fixing the external electrode to the housing. However, after the internal electrode and the external electrode are electrically joined in advance, the external electrode May be fixed to the housing.

  In addition, a power conversion device such as an inverter or a converter can be configured by combining the semiconductor module, the diode, the capacitor, and the like of the present invention. In the semiconductor module of the present invention, the semiconductor element and the electrode are electrically connected by pressure welding, so that even if the semiconductor module is operated at a high temperature, the joining member such as solder does not peel off due to a temperature change. In addition, since the change in pressure contact force due to temperature change can be reduced, each semiconductor element can be operated more uniformly. Therefore, the power conversion device configured using the semiconductor module of the present invention can improve operation reliability at high temperatures. In addition, by providing connection conductors that electrically connect internal electrodes and external electrodes on multiple surfaces, parasitic resistance and parasitic inductance can be reduced even if the area of the connection conductor junction of internal electrodes and external electrodes is reduced. Therefore, the semiconductor module can be made small. As a result, the power converter having the semiconductor module of the present invention can be made smaller than the conventional power converter.

  The semiconductor module, the semiconductor module manufacturing method, and the power conversion device according to the present invention have been described in detail with specific examples. However, the semiconductor module, the semiconductor module manufacturing method, and the power conversion device according to the present invention have been described above. Not only the form but also the design can be changed as appropriate without departing from the characteristics of the present invention, and such a modified form also belongs to the technical scope of the present invention.

  For example, the present invention is applicable to a semiconductor module in which an electrode layer of a semiconductor element and an electrode for connecting to an external circuit are electrically connected by pressure welding. Therefore, the type and number of semiconductor elements (switching elements) are The invention is not limited to the embodiment. Therefore, the same effect can be obtained even if a semiconductor module is configured by using a known semiconductor element as appropriate and using a required number of semiconductor elements to configure a predetermined circuit.

  Further, the pressure contact method of the semiconductor module is not limited to the pressure contact by the fastening member (fastening member and elastic member), and the effect of the present invention can be obtained even when the semiconductor module is appropriately fixed by a known pressure contact method.

  In addition, by applying the structure of the internal electrode and the external electrode to each of the source electrode 4, the drain electrode 5, and the gate electrode 9, the effects of the semiconductor module of the present invention can be partially obtained. Therefore, the structure of the internal electrode and the external electrode of the present invention may be applied to the source electrode 4, the drain electrode 5, and the gate electrode 9 individually or in combination.

1, 2, 22, 27... Semiconductor module 2. Switching element (semiconductor element)
3. Diode (semiconductor element)
4 ... Source / emitter electrode 4a ... Source internal electrode, 4b ... Source external electrode 5 ... Drain / collector electrode 5a ... Drain internal electrode, 5b ... Drain external electrode 6, 25 ... Housing 7 ... Drain electrode layer 8 ... Source electrode layer DESCRIPTION OF SYMBOLS 9 ... Gate electrode 9a ... Gate internal electrode, 9b ... Gate external electrode 10 ... Gate electrode layer 11 ... Anode layer 12 ... Cathode layer 13 ... Connection conductor 14 ... Stress relaxation member 15 ... Insulating plates 16, 18 ... Cooler 17 ... Sealing Stop material 19 ... Fastening member 20 ... Sealing member 23 ... Source / emitter electrode 24 ... Drain / collector electrode 26 ... Gate electrode

Claims (11)

A semiconductor element;
An internal electrode electrically connected to an electrode layer formed in the semiconductor element;
A semiconductor module in which a space in which the semiconductor element is provided is hermetically sealed with an inert gas, and the semiconductor element and the internal electrode are connected by pressure contact,
A housing provided on an outer periphery of the semiconductor module;
An external electrode provided through the housing and connecting the internal electrode and an external circuit of the semiconductor module;
A connection conductor connecting the internal electrode and the external electrode;
A semiconductor module comprising: The semiconductor module according to claim 1, wherein the casing is made of an inorganic insulating material. The semiconductor module according to claim 1, wherein the connection conductor is provided on both surfaces of the internal electrode and the external electrode. The semiconductor module according to claim 1, wherein the connection conductor is formed in a wire shape or a ribbon shape. 5. The semiconductor module according to claim 1, wherein the connection conductor is formed of a material having a thermal expansion coefficient comparable to that of the internal electrode or the external electrode. 6. The semiconductor according to claim 1, wherein the internal electrode and the external electrode are provided apart from each other by a distance that does not interfere due to thermal expansion in an operating temperature range of the semiconductor module. module. 7. The semiconductor module according to claim 1, wherein the internal electrode is made of a material having a thermal expansion coefficient close to a thermal expansion coefficient of a semiconductor element. The semiconductor module according to claim 7, wherein a metal plating layer is formed on a joint surface of the internal electrode with the connection conductor. The semiconductor according to any one of claims 1 to 8, wherein the joining of the internal electrode and the connection conductor and the joining of the external electrode and the connection conductor are performed by ultrasonic bonding or resistance welding. module. A semiconductor element;
An internal electrode electrically connected to an electrode layer formed in the semiconductor element;
An external electrode provided apart from the internal electrode and connecting the internal electrode and an external circuit;
A connection conductor for electrically connecting the internal electrode and the external electrode;
A housing through which the external electrode is inserted;
A semiconductor module manufacturing method in which a space in which the semiconductor element is provided is hermetically sealed with an inert gas, and the semiconductor element and the internal electrode are connected by pressure contact,
Bonding the internal electrode and the external electrode with the connection conductor,
Providing the internal electrode with the semiconductor element;
A method of manufacturing a semiconductor module, wherein the internal electrode is pressed against the semiconductor element. A power conversion device comprising the semiconductor module according to claim 1.

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