JP6129090B2 - Power module and method for manufacturing power module - Google Patents

Description

  The present invention relates to a power module used in every situation from power generation and transmission to efficient use and regeneration of energy.

  Power modules are spreading in various products from industrial equipment to home appliances and information terminals. For automobile equipment, high productivity and high reliability that are compatible with a wide variety of products are required along with miniaturization and weight reduction. Moreover, as a power semiconductor element mounted on the power module, a SiC (silicon carbide) power semiconductor element having a high operating temperature and excellent efficiency is likely to become a mainstream in the future. For this reason, the power module is also required to be in a package form applicable to a SiC power semiconductor element.

  In Patent Document 1, a clad material, which is a flat thin plate made of two layers of aluminum and copper, is used, and this clad material is formed in an arch shape on the surface electrode of the power semiconductor element, so that the external lead electrode There has been proposed a power semiconductor module that is soldered and has a back electrode of a power semiconductor element connected to another external extraction electrode. The clad material formed in an arch shape functions as a buffer in the thickness direction that relieves stress applied from the upper surface of the power semiconductor element in the double-sided cooling structure of the power semiconductor element.

JP 2011-216822 A (0013 stage, 0024 stage to 0029 stage, FIG. 1)

  The power module has a feature that a power semiconductor element that handles a high voltage and a large current is mounted. In order to form an electric circuit that handles a large current, the power module has a diameter of 0.5 mm with respect to the electrode on the surface of the power semiconductor element. Generally, an electric circuit is formed by wiring a plurality of wires such as thick aluminum. On the other hand, for the purpose of improving productivity and the like, power modules that join an electrode plate (lead frame) to an electrode formed on the surface of a power semiconductor element by direct soldering or the like are becoming widespread. Due to recent global warming countermeasures, environmental issues such as resource saving and energy, power modules are being applied to various products, and in order to cope with large currents, the cross-sectional area of the electrode plate May need to be increased.

  Normally, the electrodes of the power semiconductor element are made of aluminum, but the electrodes of the power semiconductor element and the electrode plate are connected by soldering. Therefore, Ni (nickel) / Au (gold) or Cu is used as the electrode of the power semiconductor element. It was necessary to metallize with (copper), and it was necessary to add a long process such as vapor deposition and sputtering. Also, a ceramic substrate (linear thermal expansion coefficient is about 5 ppm / K for aluminum nitride and about 7 ppm / K for alumina) often used as an insulating substrate for these power modules, and copper for the electrode plate (linear thermal expansion coefficient is 17 ppm / K). ), The solder joint between the power semiconductor element and the electrode plate is damaged by thermal stress, and there is a concern that a problem such as peeling or fracture occurs. In particular, in the case of SiC power semiconductor elements, which are expected to become popular due to their high efficiency in the future, it becomes possible to operate up to a higher temperature than conventional Si (silicon) power semiconductor elements. Problems may become apparent.

  In the power semiconductor module of Patent Document 1, the stress applied from the upper surface of the power semiconductor element is relaxed by a clad material that is a flat thin plate composed of two layers of aluminum and copper. In Patent Document 1, by setting the thickness of the clad material to 0.2 mm or less, the ultrasonic frequency is easily transmitted to the bonding interface, and can be reliably connected to the upper surface of the power semiconductor element. However, in the case of a power semiconductor element that handles a larger current, since the cladding material is formed in an arch shape, the cladding material and the electrode of the power semiconductor element are joined only in a small area. In order to ensure, it is necessary to thicken the cladding material. Therefore, a large force is required for ultrasonic bonding, and there is a problem that damage to the power semiconductor element due to ultrasonic bonding is increased.

  It is also conceivable that the flat clad material used for connecting one electrode is cut after the long clad material is ultrasonically bonded to the electrode of the power semiconductor element. Further, in the case of a power semiconductor element that handles a large current, the clad material becomes thick as described above, and it is necessary to apply a large force to cut the clad material, and it is thick without damaging the power semiconductor element. It is impossible to cut the clad material on the power semiconductor element. Therefore, when using an arch-like cladding material as in Patent Document 1, a manufacturing method in which a long cladding material is cut after being ultrasonically bonded to an electrode of a power semiconductor element cannot be applied.

  The present invention has been made in order to solve the above-described problems. Instead of the surface metallization process in the electrode of the conventional power semiconductor element, the flexible metal foil is replaced with the electrode of the power semiconductor element and the electrode plate. In the meantime, the bonding period of the electrode plate is shortened and the damage during the bonding to the power semiconductor element is suppressed, and the thermal stress generated at the connecting portion between the power semiconductor element and the electrode plate is reduced. The purpose is to obtain a power module that can be reduced.

A power module of the present invention includes a power semiconductor element mounted on an insulating substrate, an electrode plate having a plurality of openings disposed above the power semiconductor element, and a main electrode and an electrode plate between the power semiconductor element. The metal foil is divided into a first metal layer that is flat and flexible, and a plurality of small metal layers that are highly bondable to the electrode plate and that are a plurality of small metal layers. A flat metal plate disposed on the surface of the metal layer, the metal foil is ultrasonically bonded to the main electrode on the back surface of the first metal layer , and the electrode plate has a plurality of openings. The electrode plate is disposed above the main electrode of the power semiconductor element so that each portion is above the plurality of small metal layers, and the electrode plate is a surface of the metal foil opposite to the back surface of the metal foil. Gold which is the surface where the small metal layer in the metal layer and the first metal layer is not disposed And a back surface of the electrode plate opposite to the foil surface, the side surface of the opening, characterized in that joined to the metal foil surface by the bonding material.

According to the power module of the present invention, the metal foil is divided into a flat plate-like first metal layer having flexibility and a plurality of small metal layers having high bondability to the electrode plate, A planar second metal layer disposed on the surface of the metal layer, and the electrode plate of the power semiconductor element so that the plurality of openings are above the plurality of small metal layers, respectively. is disposed above the main electrode, the back surface of the metal foil are joined at a planar large area to the main electrode of the power semiconductor device, a surface of a metal foil, a plurality of small metallic layer and the first metal layer The metal foil surface, which is the surface on which the small metal layer is not disposed, is bonded to the back surface of the opposing electrode plate and the side surface of the opening by a bonding material, thereby shortening the bonding period of the electrode plate and power semiconductor Suppresses damage to the element, and power semiconductor element Thermal stress can be reduced resulting in the connection portion of the electrode plate.

It is a cross-sectional schematic diagram of the power module by Embodiment 1 of this invention. It is a figure which shows the electrode plate of FIG. It is a figure which shows arrangement | positioning of the clad ribbon and an electrode plate above the power semiconductor element of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a cross-sectional schematic diagram of the power module by Embodiment 2 of this invention. It is a figure which shows arrangement | positioning of the clad ribbon and an electrode plate above the power semiconductor element of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a figure which shows the manufacture process of the power module of FIG. It is a cross-sectional schematic diagram of the power module by Embodiment 3 of this invention. It is a figure which shows the manufacturing process of the power module of FIG. It is a cross-sectional schematic diagram of the power module by Embodiment 4 of this invention. It is a figure which shows the manufacture process of the power module of FIG.

Embodiment 1 FIG.
FIG. 1 is a schematic cross-sectional view of a power module according to Embodiment 1 of the present invention. 2 is a view showing the electrode plate of FIG. 1, and FIG. 3 is a view showing the arrangement of the clad ribbon and the electrode plate above the power semiconductor element of FIG. The power module 50 includes a power semiconductor element 1, a ceramic substrate 2 that is an insulating substrate on which the power semiconductor element 1 is mounted, a clad ribbon 3 that is a flat metal foil, and a solder 8 that is a bonding material. And an electrode plate 7 connected to. The resin mold type power module is manufactured by joining the above members inside a case (not shown), and finally pouring a resin for insulation sealing and heating and curing. Note that the electrode plate 7 in FIG. 3 is indicated by a broken line.

  The ceramic substrate 2 includes an alumina base 21 having a thickness of 0.635 mm and conductor layers 22 and 23 having a thickness of 0.4 mm formed on the front and back surfaces of the alumina base 21, respectively. The conductor layers 22 and 23 are made of copper. The power semiconductor element 1 is, for example, a Si diode, and has an outer dimension of 12 mm × 12 mm and a thickness of 0.3 mm. The main electrode 11 of the power semiconductor element 1 is made of aluminum, and its outer dimension is 11 mm × 11 mm. The power semiconductor element 1 is bonded to the conductor layer 22 of the ceramic substrate 2 by solder 5.

  The clad ribbon 3 in FIGS. 1 and 3 is a metal foil having an aluminum layer 32 and a copper layer 31 which are two types of metal layers and cut from a long ribbon having a width of 10 mm. The thickness of the aluminum layer 32 that is the first metal layer is 0.2 mm, and the thickness of the copper layer 31 that is the second metal layer is 0.05 mm. The width of the clad ribbon 3 is the length between the upper and lower sides of the clad ribbon 3 shown in FIG. In FIG. 1 and FIG. 3, the outer dimension of the clad ribbon 3 is 10 mm × 10 mm. The electrode plate 7 is made of copper, has a thickness of 1 mm, a width of 10 mm, and a length of 50 mm. The electrode plate 7 has an opening 71 having a diameter of 2 mm. The number of openings 71 is, for example, nine.

  A method for manufacturing the power module 50 will be described with reference to FIGS. 1 and 4 to 6. 4, FIG. 5, and FIG. 6 are diagrams showing a manufacturing process of the power module of FIG. The power module 50 becomes the final shape of FIG. 6 through the intermediate state of FIGS. The power semiconductor element 1 is joined to the conductor layer 22 of the ceramic substrate 2 with solder 5 (power semiconductor element mounting step). As shown in FIG. 4, the clad ribbon 3 is planarly positioned on the main electrode 11 of the power semiconductor element 1 bonded to the conductor layer 22 of the ceramic substrate 2 and is ultrasonically applied by the ultrasonic bonding tool 4 to be bonded. The part 33 is formed (metal foil joining step). The clad ribbon 3 and the main electrode 11 of the power semiconductor element 1 are joined by the joining portion 33. The metal foil joining process is a process of joining the clad ribbon 3 on the main electrode 11 of the power semiconductor element 1 in a plane.

  As shown in FIG. 5, only the copper layer 31 is completely cut by using the cutter 6, stopped and torn in the middle of the aluminum layer 32, and the clad ribbon 3 is put on the power semiconductor element 1 as shown in FIG. Cut (metal foil cutting step). The cutter 6 includes a mechanical type. Finally, as shown in FIG. 1, the electrode plate 7 having the opening 71 is mounted, and the solder 8 is supplied through the opening 71 to solder the clad ribbon 3 and the electrode plate 7 (electrode plate). Joining process).

  In the power module 50 according to the first embodiment, the flexible clad ribbon 3 is joined with the main electrode 11 and the electrode plate 7 of the power semiconductor element 1 interposed therebetween, so that the surface metallization process on the electrodes of the conventional power semiconductor element is performed. Can be made unnecessary, and the joining period of the electrode plate 7 can be shortened as compared with the prior art. The conventional surface metallization process for electrodes of power semiconductor elements includes vapor deposition, sputtering, plating, etc., all of which require environmental measures such as cleaning liquids, and the construction period of the joining process between the power semiconductor elements and the electrode plate is long. However, the power module 50 of the first embodiment can solve this problem.

  Further, the power module 50 according to the first embodiment is different from a conventional arch-shaped configuration even when a large current is handled, and the flexible clad ribbon 3 is formed into a flat plate with the main electrode of the power semiconductor element 1. 11 is bonded to the power semiconductor element 1 with a large area, unlike the conventional case, it is not necessary to increase the cross-sectional area of the clad ribbon 3, and damage at the time of bonding to the power semiconductor element 1 can be reduced as compared with the conventional case. Can be suppressed. In the power module 50 of the first embodiment, the flexible clad ribbon 3 has a large area with respect to the main electrode 11 with the main electrode 11 and the electrode plate 7 of the power semiconductor element 1 interposed between them in a flat plate shape. Since they are joined, unlike the conventional case, the thermal stress generated at the connecting portion between the power semiconductor element 1 and the electrode plate 7 can be reduced.

  In the power module 50 according to the first embodiment, the electrode plate 7 has the opening 71, and the opening 71 and the clad ribbon 3 superimposed on the clad ribbon 3 are soldered. The solder 8 can be supplied, and it is possible to easily confirm the strengthening of the solder joint and the formation of the solder joint by forming the fillet which is the solder part protruding from the opening 71. In addition, by forming the solder fillet, it is possible to suppress the crack progress accompanying the thermal stress.

  In the clad ribbon 3 of the first embodiment, the first metal layer bonded to the main electrode 11 of the power semiconductor element 1 is the aluminum layer 32, and the second metal layer bonded to the electrode plate 7 is the copper layer 31. Since the metal foil is formed by superimposing the copper layer 31 on the upper part of the aluminum layer 32, the flexible aluminum layer 32 is used on the main electrode 11 side so that the power semiconductor element 1 and the electrode plate 7 can be connected to each other. Such thermal stress can be suppressed. Further, by making the thickness of the copper layer 31 smaller than that of the aluminum layer 32, damage can be suppressed when the ribbon is cut on the power semiconductor element 1. Further, since the electrode plate 7 has a plurality of openings 71, the solder 8 can be supplied from the plurality of openings 71, and a solder joint is formed uniformly with respect to the electrode plate 7, so that the solder is in one place. It is possible to suppress the occurrence of current distribution due to uneven soldering without being concentrated.

  Although the clad ribbon 3 (copper aluminum clad ribbon) having the copper layer 31 and the aluminum layer 32 is used here, the main electrode 11 of the power semiconductor element 1 has a sufficient thickness, and damage due to ultrasonic bonding is taken into consideration. If it is not necessary, the same effect can be obtained by using a copper ribbon that is a metal foil of only the copper layer 31. Moreover, although the clad ribbon of the aluminum layer 32 and the copper layer 31 having a predetermined thickness was used as the clad ribbon 3, other metals (magnesium, tin, indium) having the same flexibility as aluminum, and other than copper Even if it is a combination of metals excellent in solderability (joinability) such as nickel, the same effect can be obtained.

  Regarding the thickness of the clad ribbon 3, if the aluminum layer 32 is 0.05 mm or more, it can be cut without damaging the main electrode 11 of the power semiconductor element 1, such as sizing the cutter 6, and can be up to about 1 mm thick. Good ultrasonic bonding and cutting are possible. If one copper layer 31 is 0.001 mm or more, the copper layer 31 can remain without being diffused with respect to normal soldering. The aluminum layer 32 can be ultrasonically bonded and cut on the power semiconductor element 1 as long as it is 0.2 mm or less. Regarding the thickness ratio between the aluminum layer 32 and the copper layer 31, it is considered that ultrasonic bonding is easier when the copper layer 31 is thinner than the aluminum layer 32, rather than 1: 1.

  Here, an alumina ceramic substrate is used as the ceramic substrate 2, but the same effect can be obtained with a ceramic substrate such as aluminum nitride or silicon nitride. Further, although copper is used for the conductor layers 22 and 23, the same effect can be obtained by using a ceramic substrate having an aluminum conductor layer. Although a diode is used as the power semiconductor element 1, it can be incorporated in an IGBT (Insulated Gate Bipolar Transistor) with the same configuration. Although the copper electrode plate 7 is used, the same effect can be obtained even when an aluminum plate or a CIC (copper copper clad material) plate is used.

  Here, solder was used for joining the power semiconductor element 1 and the ceramic substrate 2 or joining the power semiconductor element 1 and the electrode plate 7, but a conductive adhesive in which an Ag (silver) filler is dispersed in an epoxy resin, The same effect can be obtained by using a bonding material such as a low-temperature fired bonding material using Ag nanoparticles. In particular, for conductive adhesives, there is a concern about the increase in electrical resistance due to the natural oxide film of aluminum, but copper oxide is porous and brittle, so it is difficult to achieve electrical resistance. Resistance can be suppressed.

  Here, the copper layer 31 is completely cut by the cutter 6 and the aluminum layer 32 is torn off. However, the clad ribbon 3 can be similarly cut even if the copper layer 31 is cut halfway through the plate thickness. It becomes possible to reduce damage to the power semiconductor element 1. The ultrasonic bonding tool 4 is applied to a plurality of places and a plurality of bonding portions 33 are provided. However, the same effect can be obtained even if the entire surface is bonded at once by the ultrasonic bonding tool 4 having a large area. Moreover, although the electrode plate 7 having the opening 71 above the ultrasonic bonding location is used here, the positional relationship thereof is not limited thereto.

  The power semiconductor element 1 may be a general element based on a silicon wafer, but in the present invention, the band gap is wider than silicon carbide (SiC), gallium nitride (GaN) -based material, or silicon such as diamond. A so-called wide band gap semiconductor material can be applied. The power semiconductor element 1 is not limited to the diode and the IGBT described above, and can be mounted with a switching element such as a MOSFET (Metal Oxide Semiconductor Field-Effect-Transistor). For example, when silicon carbide (SiC), a gallium nitride (GaN) -based material, or diamond is used for the power semiconductor element 1 that functions as a switching element or the power semiconductor element 1 that functions as a rectifying element, it has been conventionally used. Since the power loss is lower than that of an element formed of silicon (Si), the power module 50 can be highly efficient. In addition, since the withstand voltage is high and the allowable current density is high, the power module 50 can be downsized. Furthermore, since the wide band gap semiconductor element has high heat resistance, it can operate at high temperature, and the cooling fin can be downsized and the water cooling part can be cooled by air. Miniaturization is possible.

  As described above, the power module 50 according to the first embodiment includes the power semiconductor element 1 mounted on the insulating substrate (ceramic substrate 2), the electrode plate 7 disposed above the power semiconductor element 1, and the power semiconductor element. 1 is provided with a metal foil (clad ribbon 3) disposed between the main electrode 11 and the electrode plate 7, and the metal foil (clad ribbon 3) has a flat plate shape, and the back surface of the metal foil (clad ribbon 3). Is ultrasonically bonded to the main electrode 11, and the electrode plate 7 is bonded to the surface opposite to the back surface of the metal foil (cladding ribbon 3) by a bonding material (solder 8). The foil (cladding ribbon 3) can be bonded to the main electrode 11 and the electrode plate 7 of the power semiconductor element 1 in a large area in a planar manner, shortening the bonding period of the electrode plate 7 and suppressing damage to the power semiconductor element 1. , Thermal stress can be reduced resulting in the connection portion between the word semiconductor element 1 and the electrode plate 7.

  In addition, the manufacturing method of the power module 50 according to the first embodiment includes a power semiconductor element 1 mounted on an insulating substrate (ceramic substrate 2), an electrode plate 7 disposed above the power semiconductor element 1, and a power semiconductor element. A power module manufacturing method for manufacturing a power module 50 including a flat metal foil (cladding ribbon 3) disposed between a main electrode 11 and an electrode plate 7, wherein the power semiconductor element 1 is insulated. The power semiconductor element mounting step to be mounted on the substrate (ceramic substrate 2) and the metal foil (cladding ribbon 3) longer than the main electrode 11 are arranged in a plane with respect to the main electrode 11 of the power semiconductor element 1, and A metal foil joining process for forming a joint 33 in which the back surface of the metal foil (cladding ribbon 3) is ultrasonically joined to the main electrode 11, and the metal foil (cladding ribbon 3) A metal foil cutting step for cutting above the semiconductor element 1, and an electrode plate 7 is mounted on the surface opposite to the back surface of the metal foil (clad ribbon 3), and a bonding material (on the surface of the metal foil (clad ribbon 3)) And an electrode plate joining step for joining by solder 8), so that the metal foil (clad ribbon 3) can be joined to the main electrode 11 and the electrode plate 7 of the power semiconductor element 1 in a large area in a plane. In addition to shortening the joining period of the electrode plate 7, it is possible to suppress damage to the power semiconductor element 1 and reduce the thermal stress generated at the connection portion between the power semiconductor element 1 and the electrode plate 7.

Embodiment 2. FIG.
7 is a schematic cross-sectional view of a power module according to Embodiment 2 of the present invention, and FIG. 8 is a diagram showing the arrangement of the clad ribbon and electrode plate above the power semiconductor element of FIG. The power module 50 according to the second embodiment includes the clad ribbon 3 having the copper pattern 35 that is a metal layer divided into a plurality of small copper layers 36 that are small metal layers. Different from 50. Note that the electrode plate 7 in FIG. 8 is indicated by a broken line. In the following, the description will be centered on parts different from the first embodiment.

  The power semiconductor element 1 and the ceramic substrate 2 are the same as those in the first embodiment. In the clad ribbon 3 of the second embodiment, as shown in FIG. 8, the copper pattern 35 is divided into, for example, nine small copper layers 36. The distance between the small copper layers 36 is 1 mm. The clad ribbon 3 in FIGS. 7 and 8 is a metal foil having an aluminum layer 32 and a copper pattern 35 which are two kinds of metal layers and cut from a long ribbon having a width of 10 mm. The thickness of the aluminum layer 32 is 0.2 mm, and the thickness of the small copper layer 36, that is, the thickness of the copper pattern 35 is 0.05 mm. The width of the clad ribbon 3 is the length between the upper and lower sides of the clad ribbon 3 shown in FIG. 7 and 8, the outer dimension of the clad ribbon 3 is 10 mm × 10 mm. The electrode plate 7 is made of copper, has a thickness of 1 mm, a width of 10 mm, and a length of 50 mm. The electrode plate 7 has an opening 71 having a diameter of 2 mm. The number of openings 71 is nine, which is the same as the number of small copper layers 36.

  A method for manufacturing the power module 50 of the second embodiment will be described with reference to FIGS. 7 and 9 to 11. 9, FIG. 10 and FIG. 11 are diagrams showing a manufacturing process of the power module of FIG. The power module 50 according to the second embodiment becomes the final shape shown in FIG. 7 through the intermediate state shown in FIGS. 9, 10, and 11. The power semiconductor element 1 is joined to the conductor layer 22 of the ceramic substrate 2 with solder 5 (power semiconductor element mounting step). As shown in FIG. 9, the clad ribbon 3 is planarly positioned on the main electrode 11 of the power semiconductor element 1 bonded to the conductor layer 22 of the ceramic substrate 2, and the ultrasonic bonding tool 4 is positioned at the position of the small copper layer 36. Is applied with ultrasonic waves to form the joint 33 (metal foil joining step). The clad ribbon 3 and the main electrode 11 of the power semiconductor element 1 are joined by the joining portion 33. The metal foil joining process is a process of joining the clad ribbon 3 on the main electrode 11 of the power semiconductor element 1 in a plane.

  As shown in FIG. 10, the cutter 6 is used to stop and tear the aluminum layer 32 in the portion where the small copper layer 36 is not present, and the clad ribbon 3 is cut on the power semiconductor element 1 as shown in FIG. (Metal foil cutting step). The cutter 6 includes a mechanical type. Finally, as shown in FIG. 7, the electrode plate 7 having the opening 71 is mounted, the solder 8 is supplied through the opening 71, and the clad ribbon 3 and the electrode plate 7 are soldered (electrode plate). Joining process).

  The power module 50 of the second embodiment can obtain the same effects as those of the first embodiment. In the power module 50 of the second embodiment, since the copper pattern 35 is divided into a plurality of small copper layers 36, the power semiconductor element 1 is cut by cutting only the flexible aluminum layer 32 in the metal foil cutting step. Can be reduced as compared with the first embodiment. Further, since the electrode plate 7 has a plurality of openings 71, the solder 8 can be supplied from the plurality of openings 71, and a solder joint is formed uniformly with respect to the electrode plate 7, so that the solder is in one place. It is possible to suppress the occurrence of current distribution due to uneven soldering without being concentrated.

  Here, a clad ribbon having a predetermined thickness of an aluminum layer 32 and a copper pattern 35 is used as the clad ribbon 3, but other metals (magnesium, tin, indium) having the same flexibility as aluminum and other than copper are used. Even if it is a combination of metals having excellent solderability such as nickel, the same effect can be obtained.

  Regarding the thickness of the clad ribbon 3, if the aluminum layer 32 is 0.05 mm or more, it can be cut without damaging the main electrode 11 of the power semiconductor element 1, such as sizing the cutter 6, and can be up to about 1 mm thick. Good ultrasonic bonding and cutting are possible. On the other hand, if the copper pattern 35 is 0.001 mm or more, the copper pattern 35 can remain without being diffused with respect to normal soldering. The aluminum layer 32 can be ultrasonically bonded and cut on the power semiconductor element 1 as long as it is 0.2 mm or less. Regarding the thickness ratio between the aluminum layer 32 and the copper pattern 35, it is considered that ultrasonic bonding is easier when the copper pattern 35 is thinner than the aluminum layer 32, rather than 1: 1.

  Here, the cutter 6 cuts the aluminum layer 32 halfway and tears the aluminum layer 32. However, the clad ribbon 3 can be similarly cut even if only the surface layer of the aluminum layer 32 is cut. It is possible to reduce damage to the semiconductor element 1. The ultrasonic bonding tool 4 is applied to a plurality of locations, and a plurality of bonding portions 33 are provided. However, the ultrasonic bonding tool 4 having a large area covering the plurality of small copper layers 36 at a time can be used under the plurality of small copper layers 36. The same effect can be obtained even if the parts are joined at once. Moreover, although the electrode plate 7 having the opening 71 above the ultrasonic bonding location is used here, the positional relationship thereof is not limited thereto.

Embodiment 3 FIG.
FIG. 12 is a schematic cross-sectional view of a power module according to Embodiment 3 of the present invention, and FIG. 13 is a diagram showing a manufacturing process of the power module of FIG. In the second embodiment, the ultrasonic bonding tool 4 is applied on the copper pattern 35 and bonded. However, as shown in FIG. 13, the power module 50 of the third embodiment avoids the small copper layer 36. It is possible to suppress deformation of the copper pattern 35 by performing bonding at the portion of the aluminum layer 32 that is easily bonded, which is a gap portion of the small copper layer 36. In addition, the power module 50 according to the third embodiment can suppress the occurrence of soldering defects due to the deformation of the copper pattern 35 in the electrode plate joining step by suppressing the deformation of the copper pattern 35. it can. In FIG. 13, the right side of the clad ribbon 3 is omitted.

Embodiment 4 FIG.
14 is a schematic cross-sectional view of a power module according to Embodiment 4 of the present invention, and FIG. 15 is a diagram showing a manufacturing process of the power module of FIG. The power module 50 of the fourth embodiment is different from that of the second embodiment in that the clad ribbon 3 has a V-shaped groove 37 in the gap portion of the small copper layer 36. The power module 50 of the fourth embodiment is an example in which the clad ribbon 3 has a copper pattern 35 divided into a plurality of small copper layers 36 and a V-shaped groove 37 in a gap portion between the small copper layers 36. . As shown in FIGS. 14 and 15, the power module 50 according to the fourth embodiment is configured so that the clad ribbon 3 is formed into a power semiconductor element by providing a V-shaped groove 37 in advance on a portion of the clad ribbon 3 where the small copper layer 36 is not present. After joining to one main electrode 11, it can be cut without using the cutter 6 simply by pulling with an appropriate force, and damage to the power semiconductor element 1 by the cutter 6 can be avoided.

  Similar to the third embodiment, the power module 50 according to the fourth embodiment avoids the small copper layer 36 and joins at the portion of the aluminum layer 32 that is easily joined, which is a gap portion of the small copper layer 36. By doing so, deformation of the copper pattern 35 can be suppressed. In addition, by suppressing the deformation of the copper pattern 35, it is possible to suppress the occurrence of soldering defects accompanying the deformation of the copper pattern 35 in the electrode plate bonding step.

  It should be noted that the present invention can be combined with each other within the scope of the invention, and each embodiment can be modified or omitted as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Power semiconductor element, 2 ... Ceramic substrate, 3 ... Cladding ribbon (metal foil), 7 ... Electrode board, 8 ... Solder, 11 ... Main electrode, 31 ... Copper layer, 32 ... Aluminum layer, 33 ... Joint part, 35 ... Copper pattern, 36 ... Small copper layer, 37 ... Groove, 50 ... Power module, 71 ... Opening.

Claims (12)

A power semiconductor element mounted on an insulating substrate, an electrode plate having a plurality of openings disposed above the power semiconductor element, and disposed between the main electrode and the electrode plate of the power semiconductor element A power module with metal foil,
The metal foil is
A first metal layer that is flat and flexible;
A flat second metal layer disposed on the surface of the first metal layer, having high bondability to the electrode plate and divided into a plurality of small metal layers;
In the metal foil, the back surface of the first metal layer is ultrasonically bonded to the main electrode,
The electrode plate is disposed above the main electrode of the power semiconductor element so that the plurality of openings are respectively above the plurality of small metal layers ,
The electrode plate is a metal foil surface opposite to the back surface of the metal foil, and is a metal surface on which the small metal layers in the plurality of small metal layers and the first metal layer are not disposed. A power module , wherein a back surface of the electrode plate facing the foil surface and a side surface of the opening are bonded to the metal foil surface by a bonding material. Said second metal layer, the power module according to claim 1, wherein the thickness is equal to or thinner than the first metal layer. The metal foil, the power module according to claim 1 or 2, characterized in that the rear surface of the small metal layer is disposed region is ultrasonically bonded to said main electrode. The power module according to claim 1 or 2, wherein the metal foil is ultrasonically bonded to the main electrode at a back surface in a gap region where the small metal layer is not disposed. The metal foil, the in the gap region in which the small metal layer is not disposed, the power module according to claim 1, any one of 4, characterized in that it comprises a groove. The power module according to any one of claims 1 to 5 , wherein the power semiconductor element is formed of a wide band gap semiconductor material. The power module according to claim 6, wherein the wide band gap semiconductor material is any one of silicon carbide, a gallium nitride-based material, and diamond. A power semiconductor element mounted on an insulating substrate, an electrode plate having a plurality of openings disposed above the power semiconductor element, and disposed between the main electrode and the electrode plate of the power semiconductor element A power module manufacturing method for manufacturing a power module having a flat metal foil,
The metal foil is
A first metal layer that is flat and flexible;
A flat second metal layer disposed on the surface of the first metal layer, having high bondability to the electrode plate and divided into a plurality of small metal layers;
A power semiconductor element mounting step of mounting the power semiconductor element on the insulating substrate;
The metal that forms the joint in which the metal foil that is longer than the main electrode is disposed in a plane with respect to the main electrode of the power semiconductor element and the back surface of the metal foil is ultrasonically bonded to the main electrode A foil joining process;
Cutting the metal foil above the power semiconductor element in a gap region where the small metal layer is not disposed ; and
The electrode plate is opposite to the back surface of the metal foil such that the plurality of openings are respectively disposed above the plurality of small metal layers and above the main electrode of the power semiconductor element. Mounted on the metal foil surface that is the side, supplying the bonding material from the plurality of openings,
The back surface of the electrode plate facing the metal foil surface, which is the surface of the plurality of small metal layers and the surface where the small metal layer in the first metal layer is not disposed, and the side surface of the opening, method of manufacturing a power module characterized in that it comprises a, and the electrode plate bonding step of bonding to the metal foil surface by the bonding material. Before Symbol metal foil, the in the gap region in which the small metal layer is not disposed, it has a groove,
The method for manufacturing a power module according to claim 8 , wherein the metal foil cutting step cuts the metal foil in the groove. In the metal foil bonding step, the back surface of the metal foil in the area where the small metal layer is arranged, according to claim 8 or 9, characterized in that to form a joint that is ultrasonically bonded to said main electrode Method of manufacturing the power module. In the metal foil bonding step, the back surface of the metal foil in the gap region in which the small metal layer is not disposed, according to claim 8, characterized in that to form a joint that is ultrasonically bonded to said main electrode or 9 The manufacturing method of the power module as described in 2. A power semiconductor element mounted on an insulating substrate; an electrode plate disposed above the power semiconductor element; and a flat metal foil disposed between the main electrode of the power semiconductor element and the electrode plate. A power module manufacturing method for manufacturing a power module comprising:
A power semiconductor element mounting step of mounting the power semiconductor element on the insulating substrate;
The metal that forms the joint in which the metal foil that is longer than the main electrode is disposed in a plane with respect to the main electrode of the power semiconductor element and the back surface of the metal foil is ultrasonically bonded to the main electrode A foil joining process;
A metal foil cutting step of cutting the metal foil above the power semiconductor element;
A method of manufacturing a power module, comprising: an electrode plate bonding step of mounting the electrode plate on a surface opposite to the back surface of the metal foil and bonding the electrode plate to the surface of the metal foil with a bonding material.

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