JP2015115471A - Power semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable power semiconductor device that can cope with high temperature and high current.SOLUTION: A semiconductor device comprises: a ceramic substrate 2; a power semiconductor element 3 of which one surface is provided with an element electrode and the other surface is bonded to the ceramic substrate 2; an electric lead 62 of which one end side is bonded to the element electrode and the side of a terminal portion 62c is electrically connected to the outside; and a sealing body 7 sealing the portion of the electrode lead 62 bonded to the element electrode and also sealing a power semiconductor element 3. The electrode lead 62 has: a metal plate 621 that has a junction surface portion bonded to the element electrode and extends from the terminal portion 62c toward the one end side; and a metal plate 622 bonded to the surface on the opposite side to the junction surface of the metal plate 621 with a bonding material having a lower elastic modulus than the metal plate 621 so as to forming a parallel circuit with the metal plate 621 between the terminal portion 62c and the element electrode.

Description

  The present invention relates to a power semiconductor device, and more particularly to a configuration of an electrode lead joined to an element electrode.

  Power semiconductor devices are spreading in all kinds of products from industrial equipment to home appliances and information terminals, and power semiconductor devices mounted on home appliances have high productivity and high reliability that can be used in various types as well as being smaller and lighter. Desired. In addition, it is also required that the package form be applicable to a silicon carbide (SiC) semiconductor that is likely to become the mainstream in the future because of its high operating temperature and excellent efficiency.

  In power semiconductor devices, in order to handle high voltages and large currents, for example, a plurality of wire bonds such as thick aluminum having a diameter of 0.5 mm are wired to the electrodes (element electrodes) on the power semiconductor element surface. It was common to form a circuit. On the other hand, for the purpose of improving productivity, a power semiconductor device in which a metal plate wiring member such as a lead frame is directly joined to the surface of an element electrode by soldering or the like is becoming widespread. And, due to environmental problems such as global warming countermeasures and resource / energy saving in recent years, power semiconductor devices are being applied to various products, and the cross-sectional area of wiring members is increased in order to cope with large currents. There is a tendency.

  On the other hand, a ceramic substrate excellent in heat dissipation and heat resistance has been used as an insulating substrate of these power semiconductor devices. However, the linear thermal expansion coefficient of the ceramic substrate is, for example, 5 ppm / K for aluminum nitride and 7 ppm / K for alumina, which is greatly different from the linear expansion coefficient (copper: 17 ppm / K) of the wiring member. For this reason, there is a concern that the solder joint portion between the power semiconductor element and the wiring member may be damaged by thermal stress due to the difference in linear expansion coefficient, causing problems such as peeling or fracture. In particular, in the case of SiC power semiconductor elements, which are expected to spread in the future due to high efficiency, it becomes possible to operate up to a higher temperature compared to conventional silicon (Si) power semiconductor elements. Problems may become apparent.

  Therefore, the thermal stress applied to the solder joint portion is suppressed by using a wiring member in which the thickness of the portion to be joined to the element electrode is made thinner than that of the main body portion or is formed in a comb shape to reduce the joint area. A power semiconductor device has been proposed (see, for example, Patent Document 1).

Japanese Patent No. 4499577 (paragraphs 0049 to 0052, FIGS. 6 to 8)

  However, if the thickness of the part that joins the device electrode is reduced, or if a wiring member that reduces the joining area is used, the electrical resistance increases, the power loss increases, and the temperature rises due to the heat generated by the joined part itself. And sometimes damaged.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a highly reliable power semiconductor device that can cope with high temperatures and high currents.

  The power semiconductor device of the present invention includes a circuit board, a power semiconductor element having an electrode formed on one surface and the other surface bonded to the circuit substrate, one end side bonded to the electrode, and the other end electrically connected to the outside. An electrode lead to be connected; and a sealing body that seals the power semiconductor element together with a portion joined to the electrode of the electrode lead, and the electrode lead has a joint surface portion with the electrode A bonding material having a lower elastic modulus than the metal plate so as to form a parallel circuit between the metal plate connected from the other end side to the one end side and the metal plate between the other end side and the electrode. And a conductive member bonded to a surface opposite to the bonding surface portion of the metal plate.

  According to the power semiconductor device of the present invention, rigidity can be kept low without increasing the resistance of the current path from the element electrode of the electrode lead. A semiconductor device can be obtained.

2A and 2B are a plan view and a cross-sectional view for explaining the configuration of the power semiconductor device according to the first embodiment of the present invention. It is sectional drawing for demonstrating the structure of the semiconductor device for electric power concerning the modification of Embodiment 1 of this invention. It is the top view and sectional drawing for demonstrating the structure of the power semiconductor device concerning Embodiment 2 of this invention. It is sectional drawing for demonstrating the structure of the power semiconductor device concerning the 1st example of Embodiment 3 of this invention. It is sectional drawing for demonstrating the structure of the semiconductor device for electric power concerning the 2nd example of Embodiment 3 of this invention. It is sectional drawing for demonstrating the structure of the power semiconductor device concerning the 3rd example of Embodiment 3 of this invention.

Embodiment 1 FIG.
1 and 2 are diagrams for explaining the configuration of the power semiconductor device according to the first embodiment of the present invention. FIG. 1A shows a state in which the sealing resin is removed from the power semiconductor device. FIG. 1B is a plan view corresponding to a cross section taken along line AA of FIG. FIG. 2 is a cross-sectional view for explaining the configuration of the power semiconductor device according to the modification, and the cutting position corresponds to the line AA in FIG.

  As shown in FIG. 1, the power semiconductor device 1 according to the first embodiment includes a switching element 3 </ b> S and a rectifying element 3 </ b> R (collectively electric power) on a conductor layer 2 a of a ceramic substrate 2 that is a circuit board by a solder joint 4 b. The semiconductor element 3) is joined. The gate electrode 3g, which is a control electrode of the switching element 3S, is electrically connected to the control terminal 52 by a wire 51 (aluminum φ0.15 mm), and is electrically connected to an external control circuit (not shown). That is, the control wiring member 5 is formed by the wire 51 and the terminal 52.

  On the other hand, of the main power electrodes of the power semiconductor element 3, the emitter electrode 3e and the surface electrode of the rectifier element 3R are soldered to the other end of the electrode lead 62 provided with a terminal portion 62c using a nut at one end. Each is connected by the part 4t. One end of a lead terminal 61 having a terminal portion 61c at the other end is joined to the conductor layer 2a. That is, the main power electrode of the power semiconductor element 3 can be electrically connected to an external power circuit by the lead terminal 61 and the electrode lead 62 (collectively, the main power wiring member 6).

  The circuit body formed in this manner is fixed using a silicone adhesive 9 so as to fill a gap between the resin base case 8 and the ceramic base material 2i. Thereafter, a sealing resin (R-416 manufactured by Ryoden Kasei Co., Ltd.) is poured into the case 8 by direct potting to form the sealing body 7, whereby the power semiconductor device 1 is completed.

  The power semiconductor element 3 is an element using SiC, which is a wide band gap semiconductor material, and has a rectangular plate shape with a thickness of 0.3 mm and a 15 mm square, respectively. As the switching element 3S, various types of elements such as MOSFET (Metal Oxide Semiconductor Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor) are used, and as the rectifying element 3R, various types of elements such as SBD (Schottky Barrier Diode) are used. Can be used. Also, the number of elements is not limited to two, and may be more or one.

  For the ceramic substrate 2, use is made of a copper base layer 2a, 2b having a thickness of 0.4 mm formed on both sides of a ceramic substrate 2i made of aluminum nitride (AlN) having a size of 40 mm × 25 mm × thickness 0.635 mm. It was. The case 8 was made of PPS (Poly Phenylene Sulfide) 48 mm × 28 mm × height 12 mm.

  Of the main power wiring member 6, the electrode lead 62 is obtained by stacking two copper metal plates 621 and 622 each having a thickness of 0.5 mm in the thickness direction and joining the overlapping portions with solder (not shown). is there. Of the metal plates 621 and 622, the metal plate 622 that is not in direct contact with the element electrode is formed with a free portion 622i that is bent and released from the metal plate 621 at a position across the two power semiconductor elements 3. Yes. The free portion 622i has a lower rigidity with respect to bending in the thickness direction than a portion joined in close contact with the metal plate 621, and is easily deformed. Therefore, the free portion 622i can easily respond to expansion and contraction due to a difference in thermal expansion.

  Note that the portion corresponding to the cross-sectional area of the portion where the free portion 622i is not provided and the metal plate 621 and the metal plate 622 are in close contact with each other is compared with the case where the metal plate 621 is formed with a single metal plate. The rigidity against bending in the thickness direction is low. Since the rigidity against bending in the thickness direction is proportional to the cube of the thickness, the rigidity when the metal plate 621 and the metal plate 622 are simply overlapped is when the electrode lead 62 is formed of a single metal plate. It becomes 1/4 of.

  And the evaluation test was done about the rigidity in case the metal plate 621 and the metal plate 622 are joined with the solder whose elastic modulus is lower than a metal plate like this Embodiment. As a result, the rigidity when a metal plate generally used as a wiring member is solder-bonded at a normal bonding pressure may be half that when the electrode lead 62 is formed of a single metal plate. all right. In other words, unless the surface accuracy is specially increased or the joining pressure is set to an extreme pressure that cannot be achieved by a normal joining technique, the bending of the portion where the two metal plates 621 and 622 are joined is performed. The rigidity can be half that of a single metal plate.

  That is, according to this method, while keeping the total cross-sectional area as the electrode lead 62 at a value corresponding to the current, the increase in rigidity is suppressed, the thermal stress is reduced, and the electrode lead 62 and the power semiconductor element 3 are reduced. It is possible to extend the life of the solder joint 4t between the two. Note that the number of sheets to be stacked is not limited to two and may be larger.

  Further, as in the modification shown in FIG. 2, when the free portion 622 i is expanded to a portion directly above the element electrode of one power semiconductor element 3 (rectifier element 3 </ b> R in the figure), solder bonding with the power semiconductor element 3 is performed. It is possible to reduce the stress on the portion 4t. Note that the power semiconductor element 3 may be the target for providing the free portion 622i, but it is preferable to provide it on the wiring path on the side closer to the external circuit. In addition, the gap formed between the metal plate 621 and the metal plate 622 by the free portion 622i enters the sealing resin (sealing body 7) by direct potting, so that they can be freely deformed without restraining each other. Expected effects.

  Although an example in which copper plates are used as the metal plates 621 and 622 constituting the electrode lead 62 is shown here, the present invention is not limited to this. As long as it has good electrical conductivity, can be processed into any shape, and has a metallized surface that can be soldered, a metal plate such as nickel (Ni), aluminum (Al), iron (Fe), etc. The same effect can be obtained with CIC (copper / invar / copper clad material). About the thickness of each of the metal plates 621 and 622, by setting the lower metal plate 621 directly connected (close) to the power semiconductor element 3 to be thicker than the upper metal plate 622, It is also possible to cope with current concentration on the short path.

  Although an example in which AlN is used as the material of the ceramic substrate 2 has been shown, the same effect can be obtained by using a ceramic material such as alumina or silicon nitride (SiN). Furthermore, when there is not much need for heat dissipation, a glass epoxy substrate or the like can be used. Furthermore, if a metal substrate having both the functions of a base plate and a ceramic substrate is used, the number of parts can be reduced, and the weight and size can be reduced. Also, the wire bond is not limited to aluminum, and the same effect can be obtained by using a copper wire, an aluminum-coated copper wire, or a gold wire. Furthermore, the same effect can be obtained by using a ribbon bond or a bus bar that ultrasonically bonds a metal plate. Moreover, about a sealing body, it is not restricted to resin for direct potting, The same effect is acquired even if it uses a silicone gel. Alternatively, the same effect can be obtained even in a structure in which the sealing body is formed by transfer molding the whole using a thermosetting resin or the like without using the case 8 or the like.

  As described above, according to the power semiconductor device 1 of the first embodiment, the circuit board (ceramic substrate 2) and the electrode (element electrode: for example, the emitter electrode 3e) are formed on one surface, and the other surface is formed. A power semiconductor element 3 bonded to a circuit board (ceramic substrate 2), an electrode lead 62 having one end side bonded to an element electrode and the other end side (terminal portion 62c) electrically connected to the outside, and an electrode lead 62 And a sealing body 7 that seals the power semiconductor element 3 together with a portion bonded to the element electrode, and the electrode lead 62 has a bonding surface portion with the element electrode and one end from the other end side (terminal portion 62c). A joining material having a lower elastic modulus than the metal plate 621 (for example, a metal plate 621 connected between the metal plate 621 and the other end side (terminal portion 62c) and the element electrode, for example, is formed. Use solder) And the second metal plate (metal plate 622) joined to the surface opposite to the joining surface portion of the metal plate 621, so that the resistance of the current path from the element electrode of the electrode lead 62 is increased. Therefore, the rigidity of the semiconductor device 1 can be kept low, so that the power semiconductor device 1 with high reliability corresponding to high temperature and high current can be obtained.

  If the thickness of the metal plate 621 is made larger than the thickness of the second metal plate (metal plate 622), it is directly connected to the power semiconductor element 3, and the current concentrates on the short path. it can.

  The second metal plate (metal plate 622) is formed with a free portion 622i that is released from the metal plate 621 on one end side, so that the stress can be further relaxed.

Embodiment 2. FIG.
In the power semiconductor device according to the second embodiment, a communication hole is formed in a portion of the electrode lead that contacts the element electrode. Further, the electrode lead is configured by overlapping two metal plates having the same shape. FIG. 3 is a diagram for explaining the configuration of the power semiconductor device according to the second embodiment of the present invention, and FIG. 3A is a plan view of a state in which the sealing resin is removed from the power semiconductor device. FIG. 3B is a cross-sectional view corresponding to a cut surface taken along line BB in FIG. In the figure, the same components as those described in the first embodiment are denoted by the same reference numerals, and detailed description of overlapping portions is omitted.

  As shown in FIG. 3, the power semiconductor device 1 according to the second embodiment also has a power semiconductor element 3 joined to a conductor layer 2a of a ceramic substrate 2 that is a circuit board by a solder joint 4b. is there. The gate electrode 3g, which is a control electrode of the switching element 3S, is electrically connected to the control terminal 52 by an aluminum wire 51, and is electrically connected to an external control circuit (not shown).

  On the other hand, of the main power electrodes of the power semiconductor element 3, the emitter electrode 3e and the surface electrode of the rectifying element 3R are connected to the other end side of the electrode lead 62 provided with the terminal part 62c at one end by the solder joint 4t. Each is connected. One end of a lead terminal 61 having a terminal portion 61c at the other end is joined to the conductor layer 2a. That is, the main power electrode of the power semiconductor element 3 can be electrically connected to an external power circuit by the lead terminal 61 and the electrode lead 62.

  The circuit body formed in this manner is fixed using a silicone adhesive 9 so as to fill a gap between the resin base case 8 and the ceramic base material 2i. Thereafter, a sealing resin (R-416 manufactured by Ryoden Kasei Co., Ltd.) is poured into the case 8 by direct potting to form the sealing body 7, whereby the power semiconductor device 1 is completed.

  The power semiconductor element 3 has a rectangular plate shape having a thickness of 0.3 mm and a 15 mm square, and various types of elements such as MOSFET and IGBT are used as the switching element 3S and SBD is used as the rectifying element 3R. be able to.

  The ceramic substrate 2 was formed by forming 0.4 mm thick copper conductor layers 2a and 2b on both sides of an AlN ceramic base 2i having a size of 40 mm × 25 mm × thickness 0.635 mm. The case 8 was made of PPS measuring 48 mm × 28 mm × height 12 mm.

  The electrode lead 62 has a thickness of 0.5 mm, and is formed by stacking two copper metal plates 623 and 624 having the same shape in the thickness direction, and joining the overlapping portions with solder (not shown). Further, each of the metal plates 623 and 624 is provided with an oval through hole extending in the longitudinal direction so that the through shape is circular among the communication holes generated when they are stacked. Of the communication holes as the electrode leads 62, one end side is a through hole for the terminal portion 62c, and therefore it is important that the shape of the through portion is circular. On the other hand, the communication hole 62a located on the element electrode of the power semiconductor element 3 is filled with the solder material of the solder joint portion 4t. The through holes formed in the plates 623 and 624 may not be oval.

  Thus, by using the metal plates 623 and 624 having the same shape, productivity can be improved without increasing the types of members having different specifications. Furthermore, by forming the communication hole 62a that communicates to the opposite surface on the element electrode, the bonding of the metal plate 623 and the metal plate 624 is also realized when the element electrode of the power semiconductor element 3 is bonded. Therefore, it is not necessary to join the metal plate 623 and the metal plate 624 in advance, and the productivity is further improved. The configuration in which the communication hole 62a is provided can also be applied to the power semiconductor device 1 according to the first embodiment.

  Therefore, the metal plate 623 and the metal plate 624 are bonded within the bonding conditions with the element electrode, that is, within the range of the bonding pressure used in the normal bonding technique. As a result, as described in the first embodiment, the bending rigidity of the electrode lead 62 in which the two metal plates 623 and the metal plate 624 are joined can be halved when formed with a single metal plate. . Furthermore, by filling the solder joint 4t into the communication hole 62a of the electrode lead 62, the joint strength can be improved.

  That is, while maintaining the total cross-sectional area as the electrode lead 62 at a value corresponding to the current, the increase in rigidity is suppressed, the thermal stress is reduced, and the solder bonding between the electrode lead 62 and the power semiconductor element 3 is performed. The life of the portion 4t can be extended.

  In the second embodiment, the example in which the copper plate is used as the metal plates 623 and 624 constituting the electrode lead 62 is shown, but the present invention is not limited to this. As long as it has good electrical conductivity, can be processed into any shape, and has a metallized surface that can be soldered, a metal plate such as nickel (Ni), aluminum (Al), iron (Fe), etc. The same effect can be obtained with CIC (copper / invar / copper clad material). Further, the plurality of metal plates may be formed of different materials.

  Although an example in which AlN is used as the material of the ceramic substrate 2 has been shown, the same effect can be obtained by using a ceramic material such as alumina or SiN. Furthermore, when there is not much need for heat dissipation, a glass epoxy substrate or the like can be used. Furthermore, if a metal substrate having both the functions of a base plate and a ceramic substrate is used, the number of parts can be reduced, and the weight and size can be reduced. Also, the wire bond is not limited to aluminum, and the same effect can be obtained by using a copper wire, an aluminum-coated copper wire, or a gold wire. Furthermore, the same effect can be obtained by using a ribbon bond or a bus bar that ultrasonically bonds a metal plate. Moreover, about a sealing body, it is not restricted to resin for direct potting, The same effect is acquired even if it uses a silicone gel. Alternatively, the same effect can be obtained even in a structure in which the sealing body is formed by transfer molding the whole using a thermosetting resin or the like without using the case 8 or the like.

  As described above, according to the power semiconductor device 1 of the second embodiment, the circuit board (ceramic substrate 2) and the electrode (element electrode: for example, the emitter electrode 3e) are formed on one surface, and the other surface is formed. A power semiconductor element 3 bonded to a circuit board (ceramic substrate 2), an electrode lead 62 having one end side bonded to an element electrode and the other end side (terminal portion 62c) electrically connected to the outside, and an electrode lead 62 And a sealing body 7 that seals the power semiconductor element 3 together with a portion bonded to the element electrode, and the electrode lead 62 has a bonding surface portion with the element electrode and one end from the other end side (terminal portion 62c). A bonding material having a lower elastic modulus than the metal plate 623 (for example, for example, so as to form a parallel circuit with the metal plate 623 between the metal plate 623 and the other end side (terminal portion 62c) and the element electrode. Use solder) Since the second metal plate (metal plate 624) having the same shape as the metal plate 623 joined to the surface opposite to the joining surface portion of the metal plate 623 is provided, the types of components are not increased. Since the rigidity can be kept low without increasing the resistance of the current path from the element electrode of the electrode lead 62, a highly reliable power semiconductor device 1 corresponding to high temperature and high current can be obtained. .

  The electrode lead 62 is formed with a communication hole 62a that communicates with the surface on the opposite side in the bonding surface portion (bonding portion with the element electrode), so that the metal plate (621, 623) is simultaneously formed with the bonding with the element electrode. And the second metal plate (622, 624) can be joined. That is, it is not necessary to join in advance.

  Since the electrode lead 62 has a portion extending in the horizontal direction and the vertical direction, such as a Z-shape, for example, when the metal plate (623) and the second metal plate (metal plate 624) are overlapped, a positional shift corresponding to the thickness occurs. . However, if each through-hole is made long, the through-hole shape of the communication hole 62a can be formed like a circle, for example.

Embodiment 3 FIG.
In the first embodiment or the second embodiment, the example in which the electrode lead is configured by stacking two metal plates has been described. In the power semiconductor device according to the third embodiment, a flexible member is stacked on a metal plate directly connected to the element electrode to ensure a cross-sectional area. 4 to 6 are diagrams for explaining the configuration of the power semiconductor device according to each example of the third embodiment of the present invention. FIG. 4 is a cross-sectional view of the power semiconductor device of the first example. 5 is a cross-sectional view of the power semiconductor device according to the second example, and corresponds to a cross section taken along line AA or BB in FIGS. 1 and 3, respectively. FIG. 6 shows the configuration of the power semiconductor device according to the third example. FIG. 6A is a cross-sectional view of the power semiconductor device with the sealing resin removed, and FIG. 6B. These are sectional drawings corresponding to the cut surface by the CC line of Fig.6 (a). In the figure, the same components as those described in the first or second embodiment are denoted by the same reference numerals, and detailed description of the overlapping portions is omitted.

  As shown in FIGS. 4 to 6, the power semiconductor device 1 according to the third embodiment and each example is also provided with a power semiconductor element 3 by a solder joint 4 b on a conductor layer 2 a of a ceramic substrate 2 that is a circuit board. Are joined. The gate electrode 3g, which is a control electrode of the switching element 3S, is electrically connected to the control terminal 52 by an aluminum wire 51, and is electrically connected to an external control circuit (not shown).

  On the other hand, the emitter electrode 3e of the switching element 3S and the surface electrode of the rectifying element 3R are respectively connected to the other end side of the electrode lead 62 provided with the terminal portion 62c at one end by a solder joint 4t. One end of a lead terminal 61 having a terminal portion 61 c at the other end is joined to the conductor layer 2 a, and the main power electrode of the power semiconductor element 3 is connected to an external power circuit by the lead terminal 61 and the electrode lead 62. It can be connected electrically.

  The circuit body formed in this manner is fixed using a silicone adhesive 9 so as to fill a gap between the resin base case 8 and the ceramic base material 2i. Thereafter, a sealing resin (R-416 manufactured by Ryoden Kasei Co., Ltd.) is poured into the case 8 by direct potting to form the sealing body 7, whereby the power semiconductor device 1 is completed.

  The power semiconductor element 3 has a rectangular plate shape having a thickness of 0.3 mm and a 15 mm square, and various types of elements such as MOSFET and IGBT are used as the switching element 3S and SBD is used as the rectifying element 3R. be able to.

  The ceramic substrate 2 was formed by forming 0.4 mm thick copper conductor layers 2a and 2b on both sides of an AlN ceramic base 2i having a size of 40 mm × 25 mm × thickness 0.635 mm. The case 8 was made of PPS measuring 48 mm × 28 mm × height 12 mm.

  In the electrode lead 62, the thickness (0.5 mm) of the other end side portion (thin wall portion 62n) in contact with the element electrode is equal to the thickness (1. The metal plate 625 or 626 formed to be thinner than 0 mm) is used. The use of the metal plate 625 or 626 having a different thickness depending on the region is common in the examples shown in FIGS. However, as the thickness is reduced, the configuration for securing a necessary cross-sectional area is different between the first example and the third example.

  As shown in FIG. 4, the power semiconductor device 1 according to the first example is formed by twisting 20 strands of φ0.2 on the surface opposite to the surface joined to the element electrode of the thin portion 62n. A plurality of copper twisted wires 62t were arranged. Each of the copper stranded wires 62t is arranged so that one end thereof covers the thick portion 62k, and the other end thereof is positioned corresponding to the element electrode of the switching element 3S, and is soldered. Thereby, the cross-sectional area of the current path from the power semiconductor element 3 to the terminal portion 62c in the electrode lead 62 can be made wider than the cross-sectional area of the thin-walled portion 62n, and a cross-sectional area suitable for the assumed current can be ensured. . Further, the copper stranded wire 62t is flexible, and the rigidity of the portion in contact with the element electrode is the rigidity of the thin portion 62n having half the thickness of the thick portion 62k. That is, while maintaining the total cross-sectional area as the electrode lead 62 at a value corresponding to the current, the increase in rigidity is suppressed, the thermal stress is reduced, and the solder bonding between the electrode lead 62 and the power semiconductor element 3 is performed. The life of the portion 4t can be extended.

  Although it is conceivable to directly bond the flexible copper stranded wire 62t to the element electrode, it is preferable to bond a rugged stranded wire to the element electrode because local stress may be applied to the element electrode. Absent. However, as in the first example, if the bonding is performed via the metal plate 625, no local stress is applied to the element electrode. Further, since the metal plate 625 has higher rigidity than the element electrode, even if local stress due to the unevenness of the copper stranded wire 62t is applied to the metal plate 625, the bonding reliability is not impaired.

  Further, as shown in FIG. 5, in the power semiconductor device 1 according to the second example, the electrode lead 62 is configured by forming the solder layer 62s on the surface opposite to the surface joined to the element electrode of the thin portion 62n. . The thickness of the solder layer 62s was adjusted so as to ensure a cross-sectional area corresponding to the cross-sectional area required for copper in consideration of the volume resistivity. The solder layer 62s needs to be thicker than the metal plate 622 in the first embodiment, but the elastic modulus of the solder is much smaller than that of copper. Therefore, as the electrode lead 62, the increase in rigidity is suppressed and the thermal stress is reduced while the cross-sectional area converted to copper is maintained at a value corresponding to the current, so that the thermal stress is reduced between the electrode lead 62 and the power semiconductor element 3. This makes it possible to extend the life of the solder joint 4t.

  Further, as shown in FIG. 6, the power semiconductor device 1 according to the third example uses a metal plate 626 in which the width of the portion corresponding to the thin portion 62n is double the width of the portion corresponding to the thick portion 62k. Thus, an electrode lead 62 was formed. And when joining to the element electrode as the electrode lead 62, the both side surface part (side surface part 62w) which protrudes from an element electrode was bent upwards, and it comprised in the U shape. Thereby, the thickness of the flat part (flat part 62f) joined to the device electrode is half that of the case of using a single piece, while the cross-sectional area on the current path is secured by adding the side part 62w. . Therefore, as the electrode lead 62, while keeping the cross-sectional area at a value corresponding to the current, the increase in rigidity of the portion (flat portion 62f) joined to the element electrode is suppressed, the thermal stress is reduced, and the electrode lead 62 The life of the solder joint 4t between the power semiconductor element 3 can be extended.

  At this time, when the flat portion 62f is curved so that both ends are lifted from the element electrode, the thickness of the joint portion 4t is continuously set so that the center portion of the solder joint portion 4t is thin and the both end portions are thick. It becomes possible to change to. By doing so, it is also possible to expect an effect of dispersing the bonding stress concentrated on the end portion of the bonding surface over the entire surface. The configuration for bending the contact surface with the element electrode is not limited to the third example, and can be applied to the other example of the third embodiment and the electrode lead 62 described in the first and second embodiments.

  Moreover, although the example which used the copper plate was shown for the metal plate 625 or 626 which comprises the electrode lead 62, it does not restrict to this. As long as it has good electrical conductivity, can be processed into any shape, and has a metallized surface that can be soldered, a metal plate such as nickel (Ni), aluminum (Al), iron (Fe), etc. The same effect can be obtained with CIC (copper / invar / copper clad material) or the like in the present embodiment as well.

  Although an example in which AlN is used as the material of the ceramic substrate 2 has been shown, the same effect can be obtained by using a ceramic material such as alumina or SiN. Furthermore, when there is not much need for heat dissipation, a glass epoxy substrate or the like can be used. Furthermore, if a metal substrate having both the functions of a base plate and a ceramic substrate is used, the number of parts can be reduced, and the weight and size can be reduced. Also, the wire bond is not limited to aluminum, and the same effect can be obtained by using a copper wire, an aluminum-coated copper wire, or a gold wire. Furthermore, the same effect can be obtained by using a ribbon bond or a bus bar that ultrasonically bonds a metal plate. Moreover, about a sealing body, it is not restricted to resin for direct potting, The same effect is acquired even if it uses a silicone gel. Alternatively, the same effect can be obtained even in a structure in which the sealing body is formed by transfer molding the whole using a thermosetting resin or the like without using the case 8 or the like.

  As described above, according to the power semiconductor device 1 according to the third embodiment, the circuit board (ceramic substrate 2) and the electrode (element electrode: for example, the emitter electrode 3e) are formed on one surface and the other surface is formed. A power semiconductor element 3 bonded to a circuit board (ceramic substrate 2), an electrode lead 62 having one end side bonded to an element electrode and the other end side (terminal portion 62c) electrically connected to the outside, and an electrode lead 62 And a sealing body 7 that seals the power semiconductor element 3 together with a portion bonded to the element electrode, and the electrode lead 62 has a bonding surface portion with the element electrode and one end from the other end side (terminal portion 62c). A bonding material having a lower elastic modulus than that of the metal plate 625 (for example, a metal plate 625 formed between the metal plate 625 and the element electrode between the other end side (terminal portion 62c) and the element electrode) (for example, Use solder) Thus, the conductive member (copper stranded wire 62t, solder layer 62s) joined to the surface opposite to the joining surface portion of the metal plate 625 is included, so that the current path from the element electrode of the electrode lead 62 is Since the rigidity can be kept low without increasing the resistance, it is possible to obtain a highly reliable power semiconductor device 1 that can cope with high temperatures and high currents.

  Alternatively, a circuit board (ceramic substrate 2), a power semiconductor element 3 having an electrode (element electrode: for example, an emitter electrode 3e) formed on one surface and the other surface bonded to the circuit substrate (ceramic substrate 2), and one end A circuit board so that the power semiconductor element 3 is wrapped with the electrode lead 62 whose side is joined to the element electrode and the other end side (terminal portion 62c) is electrically connected to the outside, and the portion of the electrode lead 62 joined to the element electrode A sealing body 7 for sealing a surface of the (ceramic substrate 2) to which the power semiconductor element 3 is bonded, and the electrode lead 62 has a bonding surface portion with the element electrode and the other end side (terminal portion 62c). ) To one end side, and is formed of a metal plate 626 that is thinner on one end side (thin wall portion 62n) than the other end side (thick wall portion 62k), and the thin wall portion 62n Bonding surface Since the portion protruding from the element electrode (side surface portion 62w) is bent upward, the rigidity of the electrode lead 62 is increased without increasing the resistance of the current path from the element electrode. Since it can be kept low, it is possible to obtain a highly reliable power semiconductor device 1 that can handle high temperatures and high currents.

  As described above, according to the power semiconductor device 1 according to the first to third embodiments, the circuit board (ceramic substrate 2) and the electrode (element electrode: for example, the emitter electrode 3e) are formed on one surface, and the like. A power semiconductor element 3 whose surface is bonded to a circuit board (ceramic substrate 2), an electrode lead 62 whose one end is bonded to an element electrode and whose other end (terminal portion 62c) is electrically connected to the outside, and an electrode lead And a sealing body 7 for sealing the power semiconductor element 3 together with a portion bonded to the element electrode 62, and the electrode lead 62 has a bonding surface portion with the element electrode and the other end side (terminal portion 62c). In order to form a parallel circuit of the metal plates (621, 623, 625) connected from one side to the other end side, and the metal plates (621, 623, 625) between the other end side (terminal portion 62c) and the element electrode, Metal plate (621 623, 625) using conductive material (metal plates 622, 624) bonded to the surface on the opposite side of the bonding surface portion of the metal plates (621, 623, 625) using a bonding material (for example, solder) having a lower elastic modulus. , Copper stranded wire 62t, and solder layer 62s), the rigidity can be kept low without increasing the resistance of the current path from the element electrode of the electrode lead 62. A highly reliable power semiconductor device 1 corresponding to the current can be obtained.

  Further, if the joint surface portion with the element electrode is curved so that the outer side from the center is away from the device electrode, an effect of dispersing the joint stress concentrated on the end portion of the joint surface can be expected.

  In each of the above-described embodiments, the power semiconductor element 3 has been described using an example of SiC, which is a wide band gap semiconductor material. However, it goes without saying that the present invention can also be applied to a general element using silicon. . However, when using SiC, gallium nitride (GaN) -based materials, or a so-called wide band gap semiconductor material having a wide band gap compared to silicon such as diamond, high current tolerance, and high temperature operation are assumed. A particularly remarkable effect appears. This is because the thickness (cross-sectional area) required for the electrode lead is increased, the rigidity is increased, the operating temperature is increased, the displacement due to the difference in linear expansion coefficient is increased, and the need to relieve stress increases. It is. Furthermore, by using the ceramic substrate 2 from the viewpoints of high temperature and high heat dissipation, the difference in linear expansion coefficient with the metal member becomes larger, and the necessity for relaxing the stress increases.

  For this reason, as in each embodiment of the present invention, the effect of stress relaxation by the configuration that does not increase the mechanical rigidity even if the area on the current path is maintained becomes significant. That is, the life of the solder joint 4t between the electrode lead 62 and the power semiconductor element 3 can be extended, and a useful structure for a wide band gap semiconductor can be provided.

1: power semiconductor device 2: ceramic substrate (circuit board) 3: power semiconductor element 4b, 4t: solder joint (joint) 5: control wiring member 6: power wiring member 7 : Sealed body, 8: Case, 9: Adhesive, 61: Lead terminal, 62: Electrode lead, 621, 623, 625: Metal plate, 622, 624: Metal plate (second metal plate),
62a: communication hole, 62c: terminal part, 62k: thick part, 62n: thin part, 62s: solder layer (conductive member), 62t: copper stranded wire (conductive member).

Claims (10)

A circuit board;
An electrode is formed on one surface and the other surface is joined to the circuit board, a power semiconductor element,
An electrode lead having one end joined to the electrode and the other end electrically connected to the outside;
A sealing body for sealing the power semiconductor element together with a portion bonded to the electrode of the electrode lead,
The electrode lead has a joint surface with the electrode and forms a parallel circuit between the metal plate connected from the other end side to the one end side and the metal plate between the other end side and the electrode. And a conductive member bonded to a surface opposite to the bonding surface portion of the metal plate using a bonding material having a lower elastic modulus than the metal plate.   The power semiconductor device according to claim 1, wherein the conductive member is a second metal plate continuous from the other end side to the one end side.   The power semiconductor device according to claim 2, wherein a thickness of the metal plate is thicker than a thickness of the second metal plate.   4. The power semiconductor device according to claim 2, wherein the second metal plate has a free portion that is separated from the metal plate on the one end side. 5.   The power semiconductor device according to claim 2, wherein the second metal plate and the metal plate are plate members having the same shape.   6. The power semiconductor device according to claim 2, wherein the electrode lead is formed with a communication hole communicating with an opposite surface in the joint surface portion. 7.   The power semiconductor device according to claim 1, wherein the conductive member is a stranded wire.   8. The power semiconductor device according to claim 1, wherein the joint surface portion is curved so that an outer side from a center is separated from the electrode. 9.   The power semiconductor device according to any one of claims 1 to 8, wherein the power semiconductor element is formed of a wide band gap semiconductor material.   10. The power semiconductor device according to claim 9, wherein the wide band gap semiconductor material is any one of silicon carbide, gallium nitride-based material, and diamond.

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