Method for manufacturing semiconductor modules, method for manufacturing power converters, semiconductor modules, power converters

Abstract

To suppress the occurrence of shrinkage nests in semiconductor modules by the technology disclosed in this application specification.SOLUTION: A method for manufacturing a semiconductor module relating to the technology disclosed in this application specification is to bond a semiconductor element to the top surface of an insulating substrate, the insulating substrate to which the semiconductor device is bonded is bonded to the base portion via a first solder, the joining of the insulating substrate and the base portion is performed by cooling the first solder while bringing the heated first solder into contact with the insulating substrate and the base portion and applying vibration to the first solder after the temperature of the first solder begins to drop.SELECTED DRAWING: Figure 3

Description

Technical Field

[0005]

[0001] The technology disclosed in this specification relates to a semiconductor module.

Background Art

[0002] Power modules are becoming increasingly popular in all products such as industrial equipment, household appliances, or information terminals, and power modules mounted in electric vehicles or industrial equipment that handle high currents and high voltages require high heat dissipation (for example, refer to Patent Document 1).

[0003] In a power module, if a shrinkage cavity (solidification crack) due to solidification shrinkage of solder occurs at the solder joint between the fin base and the ceramic substrate, it inhibits heat conduction and reduces heat dissipation.

[0004] Also, it is simultaneously required for a power module to be a package form that can be applied to SiC semiconductors, which are likely to become the mainstream in the future in terms of high operating temperature and excellent efficiency.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Semiconductor modules such as power modules are becoming increasingly popular in all scenes such as power generation, power transmission, or regeneration of electric energy, along with the growing awareness of environmental issues.

[0007] In semiconductor modules, ceramic substrates with high insulation and heat dissipation properties are used as insulating substrates because they handle high currents and high voltages. In some cases, ceramic substrates are soldered to fin bases made of aluminum or copper, which have excellent thermal conductivity, to ensure a heat dissipation path.

[0008] Ceramic substrates that mount multiple large semiconductor elements are large substrates with sides of, for example, 30 mm or more and 70 mm or less. When these are soldered to a fin base, shrinkage cavities (solidification cracks) may occur due to the solidification shrinkage of the solder. These shrinkage cavities become unbonded areas, which can hinder heat conduction and reduce heat dissipation.

[0009] The technology disclosed in this specification was developed in consideration of the problems described above, and is a technology for suppressing the occurrence of shrinkage cavities in semiconductor modules. [Means for solving the problem]

[0010] A first aspect of the technology disclosed in this specification is a method for manufacturing a semiconductor module, comprising: bonding a semiconductor element to the upper surface of an insulating substrate; bonding the insulating substrate on which the semiconductor element is bonded to a base portion via a first solder; and cooling the first solder while applying vibration to the first solder after its temperature has begun to decrease, with the heated first solder in contact with the insulating substrate and the base portion. The insulating substrate and the base portion are transported by conveyor rollers while in contact with the heated first solder, and the conveyor rollers include eccentric rollers with offset rotation centers, and the joining of the insulating substrate and the base portion is achieved by cooling the first solder while the insulating substrate and the base portion are transported by the conveyor rollers, and when the first solder is transported by the eccentric rollers after the temperature has started to drop, vibrations generated by the eccentric rollers are applied to the first solder. ru. [Effects of the Invention]

[0011] According to at least the first aspect of the technology disclosed in this specification, supercooling is less likely to occur during the solder solidification process. Therefore, the occurrence of shrinkage cavities can be suppressed.

[0012] Furthermore, the purposes, features, aspects, and advantages related to the technology disclosed in this specification will become even clearer from the detailed description and accompanying drawings provided below. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to an embodiment. [Figure 2] This is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to an embodiment. [Figure 3] This is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to an embodiment. [Figure 4] This is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to an embodiment. [Figure 5] This is a plan view showing an example of the configuration of a power module according to an embodiment. [Figure 6] This figure shows an example of the application of a power module according to the embodiment. [Figure 7] This figure shows another example of the application of the power module according to the embodiment. [Figure 8] This figure shows another example of a power module manufacturing process according to the embodiment. [Figure 9] This is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to an embodiment. [Figure 10] This is a schematic cross-sectional view showing an example of the configuration of a power module as a semiconductor module according to an embodiment. [Figure 11] This is a schematic cross-sectional view showing an example of the configuration of a power module according to an embodiment. [Figure 12] This is a schematic cross-sectional view illustrating another example of the configuration of a power module according to the embodiment. [Figure 13]This is a diagram conceptually showing an example of the configuration of a power conversion system including the power conversion device of the embodiment.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described with reference to the accompanying drawings. In the following embodiments, detailed features and the like are also shown for the purpose of explaining the technology, but these are examples and not all of them are necessarily essential features for the embodiments to be practicable.

[0015] Note that the drawings are shown schematically, and for convenience of explanation, omissions or simplifications of the configuration are made in the drawings as appropriate. Also, the mutual relationships of the sizes and positions of the configurations shown in different drawings are not necessarily accurately described and can be changed as appropriate. Also, in drawings such as a plan view which is not a cross-sectional view, hatching may be added to facilitate understanding of the content of the embodiment.

[0016] In the explanations shown below, the same reference numerals are used to illustrate the same components, and the names and functions thereof are also considered the same. Therefore, detailed explanations thereof may be omitted to avoid duplication.

[0017] Also, in the explanations described in this specification, when a component is described as "comprising", "including" or "having", etc., it is not an exclusive expression excluding the existence of other components, unless otherwise specified.

[0018] Also, in the explanations described in this specification, even when ordinal numbers such as "first" or "second" are used, these terms are used for convenience to facilitate understanding of the content of the embodiment, and the content of the embodiment is not limited to the order or the like that may be caused by these ordinal numbers.

[0019] Furthermore, even if terms such as "top," "bottom," "left," "right," "side," "bottom," "front," or "back" are used in the descriptions of this specification to indicate a specific position or direction, these terms are used for convenience to facilitate understanding of the embodiments and are not related to the actual position or direction in which the embodiments are carried out.

[0020] Furthermore, in the descriptions contained herein, when a "top surface of..." or "bottom surface of..." is used, it includes not only the top surface or bottom surface of the component in question itself, but also the state in which other components are formed on the top surface or bottom surface of the component in question. That is, for example, when it is stated that "B is provided on the top surface of A", this does not preclude the presence of another component "C" between A and B.

[0021] <First Embodiment> The semiconductor module and the method for manufacturing the semiconductor module according to this embodiment will be described below. In the following description, the expression "A and B are electrically connected" means that current can flow bidirectionally between configuration A and configuration B.

[0022] <About the configuration of the semiconductor module> Figures 1 to 4 are schematic cross-sectional views illustrating an example of the manufacturing process for a power module as a semiconductor module according to this embodiment.

[0023] As shown in Figure 1, the semiconductor element 2 is positioned and mounted on the ceramic substrate 10 together with the solder 31. Then, it is soldered in a reflow oven by preheating at 150°C for 90 seconds and main heating at 250°C for 30 seconds. Here, the solder 31 for mounting the semiconductor element 2 is in sheet form, for example, with a thickness of 0.3 mm, and is composed of 96.5% tin, 3% silver, and 0.5% copper, with a melting point of 217°C.

[0024] Semiconductor element 2 is, for example, a silicon diode. In this case, for example, its dimensions are 13 mm in length, 10 mm in width, and 0.2 mm in thickness. Alternatively, semiconductor element 2 is, for example, a silicon insulated gate bipolar transistor (i.e., IGBT). In this case, for example, its dimensions are 13 mm in length, 13 mm in width, and 0.2 mm in thickness.

[0025] The ceramic substrate 10 has a copper surface conductive layer 12 formed on the upper surface of an aluminum nitride substrate 11 by brazing. Additionally, a back surface conductive layer 13 is formed on the lower surface of the aluminum nitride substrate 11 by brazing. Here, the aluminum nitride substrate 11 has a thickness of, for example, 0.64 mm. The surface conductive layer 12 and the back surface conductive layer 13 have a thickness of, for example, 0.8 mm.

[0026] Next, as shown in Figure 2, the base plate 70 and the ceramic substrate 10 on which the semiconductor element 2 is mounted are superimposed via solder 30. A silicone adhesive 81 is applied around the base plate 70, and the case 5, on which the external electrodes 61 and signal electrodes 63 are inserted, is superimposed via the silicone adhesive 81. The external electrodes 61 are joined to the surface conductor layer 12 via solder 32. Here, the base plate 70 is, for example, made of copper and has dimensions of 60 mm in length, 45 mm in width, and 3 mm in thickness. The solder 30 used to superimpose the ceramic substrate 10 on the base plate 70 is in sheet form, for example, 0.4 mm thick, composed of 96.5% tin, 3% silver, and 0.5% copper, with a melting point of 217°C. Case 5, for example, is made of polyphenylene sulfide (i.e., PPS) resin and has dimensions of 60 mm in length, 45 mm in width, and 6 mm in thickness.

[0027] Next, as shown in Figure 3, with the ceramic substrate 10 and the base plate 70 stacked together, the solder 30 is melted in a reflow oven by preheating at 150°C for 90 seconds and then at 250°C for 30 seconds. After that, cooling is started and the temperature of the solder 30 begins to decrease, and the ultrasonic horn 91 is inserted into the opening of the hot plate 90 (cooling plate) inside the reflow oven and applied to the back surface (in contact with the bottom surface) of the base plate 70, and 44kHz ultrasonic waves are applied. As a result, vibrations can be applied to the cooling solder 30. In this process, the silicone adhesive 81 is also hardened by heating, and the case 5 and the base plate 70 are bonded together.

[0028] Next, as shown in Figure 4, the main terminals of the diode and the IGBT, which are semiconductor elements 2, are connected to the surface conductor layer 12 or external electrode 61 of the ceramic substrate 10 by aluminum wires 41, and the gate electrode of the IGBT is connected to the signal electrode 63 by aluminum wires 42. Here, wire 41 has a diameter of, for example, 0.4 mm. Wire 42 has a diameter of, for example, 0.15 mm. The inside of the case 5 is then filled with sealing resin 82 to form a power module. Here, the sealing resin 82 is, for example, an epoxy resin in which silica filler is dispersed.

[0029] In this example, an aluminum nitride substrate 11 was used as the base material for the ceramic substrate 10, but a silicon nitride or alumina substrate may also be used. Furthermore, while copper was used for the surface conductor layer 12 and the back surface conductor layer 13, an aluminum conductor layer can also be used by modifying its surface with nickel plating or the like to allow it to solder. Additionally, a resin-insulated metal substrate or a glass epoxy resin substrate may be used instead of the ceramic substrate 10, provided that the required heat dissipation performance is met.

[0030] Furthermore, although copper was used as the material for the base plate 70, an aluminum or aluminum alloy base plate may also be used. Also, although silicon was used for the diode and IGBT as semiconductor elements 2, wide-bandgap semiconductors such as silicon carbide or gallium nitride may be used.

[0031] Furthermore, while solder 30 and solder 31 were used, they consisted of 96.5% tin, 3% silver, and 0.5% copper with a melting point of 217°C. However, solder materials consisting of 99.3% tin and 0.7% copper with a melting point of 224°C, or solder materials consisting of 95% tin and 5% antimony with a melting point of 240°C may also be used. In addition, a portion of the solder may be replaced with other joining materials such as silver epoxy adhesive, silver sintered material, or brazing material.

[0032] Furthermore, although wires 41 and 42 were made of aluminum, they may also be made of an aluminum alloy containing trace amounts of additives such as iron, or they may be made of copper.

[0033] Furthermore, while Case 5 uses a PPS material, it is possible to improve heat resistance by replacing it with a liquid crystal polymer (LCP) material.

[0034] Furthermore, although copper frames were used for the external electrodes 61 and signal electrodes 63, the external electrodes 61 and signal electrodes 63 may be nickel-plated as appropriate, or replaced with copper alloy or nickel-plated aluminum.

[0035] Furthermore, while an epoxy resin with dispersed silica filler was used as the sealing resin 82, other fillers such as alumina can also be used, and a similar effect can be obtained by mixing epoxy resin with silicone resin. A similar effect can also be obtained by sealing with silicone resin alone.

[0036] Furthermore, in the above method, ultrasonic waves from the ultrasonic horn 91 are applied during the cooling of the solder 30 after heating is complete (after the temperature of the solder 30 has started to decrease). However, when vibration is applied, the bonding state between the ceramic substrate 10 and the base plate 70 becomes unstable, which can reduce the cooling rate and affect productivity. Therefore, by applying ultrasonic waves after the temperature of the solder 30 has dropped after cooling has started and the temperature of the solder 30 has fallen below the melting point (liquidus temperature) of 217°C, the time required for cooling can be shortened, and productivity can be improved.

[0037] Furthermore, the solder 31 used to bond the semiconductor element 2 to the ceramic substrate 10 has a higher melting point than the solder 30 used to bond to the base plate 70, and ultrasonic waves can be applied after the solder 30 has cooled to a temperature lower than its melting point. By doing so, vibrations are applied to the solder 30 while the bond between the semiconductor element 2 and the ceramic substrate 10 is fixed, thereby suppressing the occurrence of misalignment of the semiconductor element 2 relative to the ceramic substrate 10. In this case, the solder 30 can be, for example, 96.5% tin, 3% silver, and 0.5% copper with a melting point of 217°C, and the solder 31 can be, for example, 95% tin and 5% antimony with a melting point of 240°C.

[0038] Figure 5 is a plan view showing an example of the configuration of a power module according to this embodiment. Note that the sealing resin is omitted from the illustration in Figure 5.

[0039] As shown in Figure 5, the surface conductor layer 12 of the ceramic substrate 10 is patterned to function as a 2-in-1 module. The semiconductor element 2 mounted on the upper surface of the ceramic substrate 10 has a main circuit formed by wires 41 and is connected to external electrodes 61. The gate electrode 20g of the semiconductor element 2 is connected to signal electrodes 63 by wires 42, forming a control circuit. While Figure 5 shows a 2-in-1 module as an example, a 1-in-1 module or a 6-in-1 module may also be used.

[0040] Figure 6 shows an example of the application of a power module according to this embodiment. In the example shown in Figure 6, cooling fins 71 are attached to the lower surface of the base plate 70 via thermal conductive grease 83. The cooling fins 71 ensure a heat dissipation path for the semiconductor element 2.

[0041] Figure 7 shows another example of the application of the power module according to this embodiment. In the example shown in Figure 7, a base plate 70p with pin fins 72 is bonded to the case 5 via silicone adhesive 81 and joined to the underside of the ceramic substrate 10 via solder 30. The pin fins 72 are provided on the underside of the base plate 70p. A water cooling jacket 73 is further fastened to the base plate 70p. The base plate 70p and the water cooling jacket 73 enable heat dissipation by water cooling.

[0042] Figure 8 shows another example of the manufacturing process for a power module according to this embodiment. As illustrated in Figure 8, the ultrasonic horn 91 can also be applied to (in contact with) the upper surface of the semiconductor element 2 to vibrate the ceramic substrate 10. As a result, vibration can be applied to the solder 30. Alternatively, the ultrasonic horn 91 may be incorporated into the heating plate 90 to vibrate the heating plate 90 itself.

[0043] <Second Embodiment> A semiconductor module and a method for manufacturing the semiconductor module according to this embodiment will be described. In the following description, components similar to those described in the embodiments described above will be denoted by the same reference numerals, and their detailed descriptions will be omitted as appropriate.

[0044] <About the configuration of the semiconductor module> Figure 9 is a schematic cross-sectional view illustrating an example of a manufacturing process for a power module as a semiconductor module according to this embodiment. Figure 9 particularly shows the process of applying ultrasound.

[0045] As shown in Figure 9, in the process in which the base plate 70 and the ceramic substrate 10 on which the semiconductor element 2 is mounted are joined via solder 30, the reflow oven is a hot air type rather than a hot plate type, and the mechanism for transporting the power module is a conveyor.

[0046] In this case, at least a portion of the conveyor rollers 92 in the conveyor are eccentric rollers, meaning their center of rotation is offset from the center of the roller. Due to this offset, the eccentric rollers vibrate during rotation.

[0047] Because at least a portion of the conveyor rollers 92 are eccentric rollers, vibrations occur in the power modules as they pass over the eccentric rollers during transport. These vibrations in the power modules reduce overcooling of the solder 30 as it cools down after being heated (for example, as shown in Figure 3).

[0048] The eccentric conveyor rollers 92 may be provided only in the area where the solder 30 is cooled. Furthermore, by using a solder 31 that has a higher melting point than the solder 30 used for bonding to the base plate 70, and controlling the transport timing so that the power module enters the area where the conveyor rollers 92 are positioned only after the temperature of the solder 30 has fallen below the melting point of the solder 31, the occurrence of misalignment of the semiconductor element 2 relative to the ceramic substrate 10 can be suppressed. In this case, the solder 30 can be, for example, 96.5% tin, 3% silver, and 0.5% copper with a melting point of 217°C, and the solder 31 can be, for example, 95% tin and 5% antimony with a melting point of 240°C.

[0049] <Third Embodiment> A semiconductor module and a method for manufacturing the semiconductor module according to this embodiment will be described. In the following description, components similar to those described in the embodiments described above will be denoted by the same reference numerals, and their detailed descriptions will be omitted as appropriate.

[0050] <About the configuration of the semiconductor module> Figure 10 is a schematic cross-sectional view showing an example of the configuration of a power module as a semiconductor module according to this embodiment.

[0051] As shown in Figure 10, the base plate 70 and the ceramic substrate 10 on which the semiconductor element 2 is mounted are soldered together via solder 30. Here, the base plate 70 is made of copper, for example, and has dimensions of 60 mm in length, 45 mm in width, and 3 mm in thickness. The solder 30 is in sheet form and has a thickness of, for example, 0.4 mm.

[0052] A silicone adhesive 81 is applied around the ceramic substrate 10, and the ceramic substrate 10 is bonded to a copper lead frame on which an external electrode 61f or signal electrode 63f is formed, via the silicone adhesive 81.

[0053] The main terminals of the diode and IGBT, which are semiconductor elements 2, are connected to the surface conductor layer 12 of the ceramic substrate 10 or the external electrodes 61f of the lead frame by aluminum wires 41. Here, the wires 41 have a diameter of, for example, 0.4 mm.

[0054] Furthermore, the gate electrode of the IGBT and the signal electrode 63f of the lead frame are wire-bonded together by an aluminum wire 42 to form a circuit. Here, the wire 42 has a diameter of, for example, 0.15 mm.

[0055] Then, the transfer mold resin 84 insulates and seals the power module, while exposing one end of the external electrode 61f, one end of the signal electrode 63f, and the back surface of the base plate 70.

[0056] Figure 11 is a schematic cross-sectional view showing an example of the configuration of a power module according to this embodiment. Figure 11 shows the process by which the ceramic substrate 10 and the base plate 70 are soldered together in the configuration shown in Figure 10.

[0057] With the copper lead frame and ceramic substrate 10 bonded together with silicone adhesive 81, the base plate 70 is placed in a recess 90a formed in the hot plate 90 of the reflow oven. Then, in the reflow oven, the solder 30 is melted by preheating at 150°C for 90 seconds and main heating at 250°C for 30 seconds. After that, cooling is started and the ultrasonic horn 91 is brought into contact with the back surface of the hot plate 90 (cooling plate) inside the reflow oven and applied to the back surface of the base plate 70, and 44kHz ultrasonic waves are applied. In this process, the silicone adhesive 81 is also hardened by heating, and the lead frame (external electrode 61f and signal electrode 63f) and the ceramic substrate 10 are bonded together.

[0058] Figure 12 is a schematic cross-sectional view showing another example of the configuration of a power module according to this embodiment. In the example shown in Figure 12, cooling fins 71 are attached to the lower surface of the base plate 70 via thermal conductive grease 83. The cooling fins 71 ensure a heat dissipation path for the semiconductor element 2.

[0059] In this embodiment, a copper lead frame was used, but an alloy or nickel-plated aluminum lead frame may also be used.

[0060] <Fourth Embodiment> A power converter according to this embodiment and a method for manufacturing the power converter will be described below. In the following description, components similar to those described in the embodiments described above will be denoted by the same reference numerals, and their detailed descriptions will be omitted as appropriate.

[0061] <Regarding the configuration of the power converter> This embodiment applies the power module described above to a power converter. The power converter to which it can be applied is not limited to a specific application, but the following description will focus on its application to a three-phase inverter.

[0062] Figure 13 is a conceptual diagram showing an example of the configuration of a power conversion system including the power conversion device of this embodiment.

[0063] As illustrated in Figure 13, the power conversion system comprises a power supply 2100, a power converter 2200, and a load 2300. The power supply 2100 is a DC power supply and supplies DC power to the power converter 2200. The power supply 2100 can be composed of various components, such as a DC grid, a solar cell, or a battery. Alternatively, the power supply 2100 can be composed of a rectifier circuit or an AC-DC converter connected to an AC grid. Furthermore, the power supply 2100 can also be composed of a DC-DC converter that converts DC power output from a DC grid into a predetermined power.

[0064] The power converter 2200 is a three-phase inverter connected between the power supply 2100 and the load 2300. The power converter 2200 converts the DC power supplied from the power supply 2100 into AC power and then supplies this AC power to the load 2300.

[0065] Furthermore, as shown in Figure 13 as an example, the power converter 2200 includes a conversion circuit 2201 that converts DC power to AC power and outputs it, and a control circuit 2203 that outputs a control signal to the conversion circuit 2201 for controlling the conversion circuit 2201.

[0066] Load 2300 is a three-phase motor driven by AC power supplied from power converter 2200. Note that Load 2300 is not limited to a specific application; it is a motor used in various electrical devices, such as hybrid vehicles, electric vehicles, railway vehicles, elevators, or air conditioning equipment.

[0067] The details of the power converter 2200 are described below. The conversion circuit 2201 includes a switching element and a freewheeling diode (not shown here). The switching element performs a switching operation to convert the DC power supplied from the power supply 2100 into AC power, which is then supplied to the load 2300.

[0068] While there are various specific circuit configurations for the conversion circuit 2201, the conversion circuit 2201 according to this embodiment is a two-level three-phase full-bridge circuit and comprises six switching elements and six freewheeling diodes connected in antiparallel to each of the switching elements.

[0069] At least one of the switching elements and freewheeling diodes in the conversion circuit 2201 is fitted with a power module as described in any of the embodiments above. The six switching elements are connected in series in pairs to form upper and lower arms, and each upper and lower arm constitutes the phases of the full bridge circuit (i.e., U phase, V phase, and W phase). The output terminals of each upper and lower arm (i.e., the three output terminals of the conversion circuit 2201) are connected to the load 2300.

[0070] Furthermore, the conversion circuit 2201 includes a drive circuit (not shown here) for driving each switching element. The drive circuit may be built into the power module, which is a semiconductor module, or it may be configured separately from the semiconductor module. The drive circuit generates a drive signal for driving the switching elements of the conversion circuit 2201 and supplies this drive signal to the control electrodes of the switching elements of the conversion circuit 2201. Specifically, based on the control signal output from the control circuit 2203, which will be described later, it outputs a drive signal to turn on the switching element and a drive signal to turn off the switching element to the control electrodes of each switching element.

[0071] When a switching element is kept in the ON state, the drive signal is a voltage signal equal to or greater than the threshold voltage of the switching element (i.e., an ON signal). When a switching element is kept in the OFF state, the drive signal is a voltage signal equal to or less than the threshold voltage of the switching element (i.e., an OFF signal).

[0072] The control circuit 2203 controls the switching elements of the conversion circuit 2201 so that the desired power is supplied to the load 2300. Specifically, it calculates the time that each switching element of the conversion circuit 2201 should be in the ON state (i.e., the ON time) based on the power to be supplied to the load 2300. For example, the conversion circuit 2201 can be controlled by PWM control, which modulates the ON time of the switching elements according to the voltage to be output.

[0073] The control circuit 2203 then outputs a control command (i.e., a control signal) to the drive circuit so that an ON signal is output to the switching element that should be ON at each given time, and an OFF signal is output to the switching element that should be OFF. Based on this control signal, the drive circuit outputs an ON signal or an OFF signal as a drive signal to the control electrode of each switching element.

[0074] In the power converter 2200 according to this embodiment, a power module from any of the embodiments described above is used as the switching element of the conversion circuit 2201, thereby stabilizing the on-resistance after the energizing cycle.

[0075] In this embodiment, an example of applying the power module described above to a two-level three-phase inverter has been described. However, the application examples are not limited to this, and the power module described above can be applied to various power conversion devices.

[0076] Furthermore, although this embodiment describes a two-level power converter, the power module in any of the embodiments described above may also be applied to a three-level or multi-level power converter. In addition, when supplying power to a single-phase load, the power module in any of the embodiments described above may be applied to a single-phase inverter.

[0077] Furthermore, when supplying power to a DC load or the like, the power module described in any of the embodiments above can be applied to a DC-DC converter or an AC-DC converter.

[0078] Furthermore, a power conversion device to which the power module in any of the embodiments described above is applied is not limited to cases where the load described above is an electric motor, but can also be used, for example, as a power supply device for an electrical discharge machine, a laser processing machine, an induction heating cooker, or a non-contact power supply system. In addition, a power conversion device to which the power module in any of the embodiments described above is applied can also be used as a power conditioner in a solar power generation system or an energy storage system.

[0079] <Regarding the manufacturing method of power converters> Next, a method for manufacturing a power conversion device according to this embodiment will be described.

[0080] First, a power module is manufactured using the manufacturing method described in the embodiments described above. Then, a conversion circuit 2201 having the power module is provided as part of the power conversion device. The conversion circuit 2201 is a circuit for converting the input power and outputting it.

[0081] A control circuit 2203 is provided as part of the power conversion device configuration. The control circuit 2203 is a circuit that outputs control signals to the conversion circuit 2201 for controlling the conversion circuit 2201.

[0082] The semiconductor switching elements used in the embodiments described above are not limited to switching elements made of silicon (Si) semiconductors. For example, the semiconductor switching elements may be made of a non-Si semiconductor material with a wider band gap than Si semiconductors.

[0083] Examples of non-Si semiconductor materials, such as wide-bandgap semiconductors, include silicon carbide, gallium nitride-based materials, and diamond.

[0084] Switching elements made of wide-bandgap semiconductors can be used even in high-voltage regions where unipolar operation is difficult with Si semiconductors, and can significantly reduce switching losses that occur during switching operation. Therefore, a large reduction in power loss is possible.

[0085] Furthermore, switching elements made of wide-bandgap semiconductors have low power loss and high heat resistance. Therefore, when constructing a power module with a cooling section, it is possible to miniaturize the heat sink's heat dissipation fins, which in turn enables further miniaturization of the semiconductor module.

[0086] Furthermore, switching elements made of wide-bandgap semiconductors are suitable for high-frequency switching operations. Therefore, when applied to converter circuits that require high frequencies, increasing the switching frequency can also allow for miniaturization of reactors or capacitors connected to the converter circuit.

[0087] Therefore, the same effects can be obtained even when the semiconductor switching element in the embodiments described above is made of a wide-bandgap semiconductor such as silicon carbide.

[0088] <Regarding the effects produced by the embodiments described above> Next, examples of the effects produced by the embodiments described above will be shown. In the following description, the effects will be described based on the specific configurations illustrated in the embodiments described above, but they may be replaced with other specific configurations illustrated in this specification to the extent that similar effects are produced. That is, for convenience, in the following, only one of the corresponding specific configurations may be described as representative, but the specific configuration described as representative may be replaced with another corresponding specific configuration.

[0089] Furthermore, such substitutions may be made across multiple embodiments. That is, the respective configurations exemplified in different embodiments may be combined to produce similar effects.

[0090] According to the embodiment described above, in the method for manufacturing a semiconductor module, a semiconductor element 2 is bonded to the upper surface of an insulating substrate. Here, the insulating substrate corresponds to, for example, a ceramic substrate 10. The ceramic substrate 10 to which the semiconductor element 2 is bonded is then bonded to a base portion via a first solder. Here, the first solder corresponds to, for example, solder 30. The base portion corresponds to, for example, a base plate 70. Here, the bonding of the ceramic substrate 10 and the base plate 70 is performed by bringing the heated solder 30 into contact with the ceramic substrate 10 and the base plate 70, and then cooling the solder 30 while applying vibration to the solder 30 after it has started to cool down.

[0091] With this configuration, supercooling is less likely to occur during the solidification process of the solder 30. Therefore, it is possible to suppress the concentration of solidification shrinkage and the occurrence of large shrinkage cavities that can result from the solder 30 solidifying all at once.

[0092] Unless otherwise specified, the order in which each process is performed can be changed.

[0093] Furthermore, the same effect can be achieved even if other configurations exemplified in this specification are appropriately added to the above configuration, that is, if other configurations in this specification that are not mentioned as above configurations are appropriately added.

[0094] Furthermore, according to the embodiment described above, the ceramic substrate 10 and the base plate 70 are transported by the conveyor roller 92 while in contact with the heated solder 30. Here, the conveyor roller 92 includes an eccentric roller whose rotation center is offset. The bonding between the ceramic substrate 10 and the base plate 70 is achieved by cooling the solder 30 while the ceramic substrate 10 and the base plate 70 are transported by the conveyor roller 92, and then, when the solder 30 is transported by the eccentric roller after the temperature has started to drop, the solder 30 is subjected to vibrations generated by the eccentric roller. With this configuration, it is possible to reduce overcooling of the solder 30 as it is cooled during transport.

[0095] Furthermore, according to the embodiments described above, the bonding between the ceramic substrate 10 and the base plate 70 is achieved by applying vibrations generated by the ultrasonic horn 91, which contacts the lower surface of the base plate 70, to the solder 30 after the temperature has started to decrease, thereby cooling the solder 30. With such a configuration, the degree of freedom in the method of applying vibrations to the solder 30 by the ultrasonic horn 91 is increased.

[0096] Furthermore, according to the embodiments described above, the bonding between the ceramic substrate 10 and the base plate 70 is achieved by cooling the solder 30 while applying vibrations generated by the ultrasonic horn 91, which contacts the upper surface of the semiconductor element 2, to the solder 30 after the temperature has started to decrease. With such a configuration, the degree of freedom in the method of applying vibrations to the solder 30 by the ultrasonic horn 91 is increased.

[0097] Furthermore, according to the embodiments described above, the bonding of the ceramic substrate 10 and the base plate 70 is achieved by cooling the heated solder 30 while it is in contact with the ceramic substrate 10 and the base plate 70, and then applying vibration to the solder 30 after it has fallen below the liquidus temperature (melting point). With this configuration, by shortening the time for applying vibration, the precision of the bonding between the ceramic substrate 10 and the base plate 70 can be improved, thereby improving the productivity of semiconductor modules and suppressing misalignment of the semiconductor elements 2.

[0098] Furthermore, according to the embodiment described above, the semiconductor element 2 is joined to the upper surface of the ceramic substrate 10 via a second solder. Here, the second solder corresponds to, for example, solder 31. The melting point of solder 31 is higher than the melting point of solder 30. With this configuration, since the solder 31 is fixed in place when the solder 30 is vibrated, it is possible to suppress the occurrence of misalignment of the semiconductor element 2 relative to the ceramic substrate 10.

[0099] Furthermore, according to the embodiment described above, the bonding of the ceramic substrate 10 and the base plate 70 is achieved by cooling the heated solder 30 while it is in contact with the ceramic substrate 10 and the base plate 70, and then applying vibration to the solder 30 after it has cooled to a temperature lower than the melting point of the solder 31. With this configuration, since the bonding between the semiconductor element 2 and the ceramic substrate 10 by the solder 31 is fixed while vibration is applied to the solder 30, it is possible to suppress the occurrence of misalignment of the semiconductor element 2 relative to the ceramic substrate 10.

[0100] Furthermore, according to the embodiments described above, the base plate 70 has a fin structure on the side opposite to the side that is joined to the ceramic substrate 10. Here, the fin structure corresponds to at least one of, for example, a cooling fin 71, a pin fin 72, etc. With such a configuration, the fin structure can appropriately secure a heat dissipation path for the semiconductor element 2.

[0101] Furthermore, according to the embodiments described above, the method for manufacturing a power converter includes a semiconductor module manufactured by the above manufacturing method and a conversion circuit 2201 that converts and outputs the input power. A control circuit 2203 is also provided that outputs a control signal to the conversion circuit 2201 for controlling the conversion circuit 2201. With this configuration, supercooling is less likely to occur as the solder 30 cools down. Therefore, it is possible to suppress the occurrence of large shrinkage cavities due to concentrated solidification shrinkage caused by the solder 30 solidifying all at once.

[0102] <Modifications of the embodiments described above> In the embodiments described above, the material, dimensions, shape, relative arrangement, or implementation conditions of each component may also be described, but these are merely examples and not limiting in all aspects.

[0103] Accordingly, countless variations and equivalents not shown are envisioned within the scope of the art disclosed herein. These include, for example, modifications, additions, or omissions of at least one component, as well as the extraction of at least one component from at least one embodiment and its combination with a component from another embodiment.

[0104] Furthermore, in the embodiments described above, if a material name or the like is mentioned without further specification, it is assumed that the material includes other additives, such as alloys, unless otherwise specified, as long as it does not create a contradiction.

[0105] Furthermore, the descriptions in this specification are referenced for all purposes related to the present technology and are not considered to be prior art.

[0106] The various aspects of this disclosure are summarized below as an appendix.

[0107] (Note 1) A semiconductor element is bonded to the upper surface of the insulating substrate. The insulating substrate on which the semiconductor elements are bonded is joined to the base portion via the first solder. The joining of the insulating substrate and the base portion is performed by bringing the heated first solder into contact with the insulating substrate and the base portion, and then cooling the first solder while applying vibration to it after the temperature has started to decrease. A method for manufacturing semiconductor modules.

[0108] (Note 2) The method for manufacturing a semiconductor module as described in Appendix 1, The insulating substrate and the base portion are transported by conveyor rollers while in contact with the heated first solder, respectively. The conveyor rollers include eccentric rollers whose rotation centers are offset, The joining of the insulating substrate and the base portion involves cooling the first solder while the insulating substrate and the base portion are being transported by the conveyor roller, and then, when the first solder is being transported by the eccentric roller after the temperature has started to drop, the first solder is subjected to vibrations generated by the eccentric roller. A method for manufacturing semiconductor modules.

[0109] (Note 3) The method for manufacturing a semiconductor module as described in Appendix 1, The bonding of the insulating substrate and the base portion is achieved by cooling the first solder after the temperature of the first solder has started to decrease, while applying vibrations generated by an ultrasonic horn that contacts the lower surface of the base portion. A method for manufacturing semiconductor modules.

[0110] (Note 4) The method for manufacturing a semiconductor module as described in Appendix 1, The bonding between the insulating substrate and the base portion is achieved by cooling the first solder after the temperature has started to decrease, while applying vibrations generated by an ultrasonic horn that contacts the upper surface of the semiconductor element. A method for manufacturing semiconductor modules.

[0111] (Note 5) A method for manufacturing a semiconductor module as described in any one of the appendices 1 to 4, The joining of the insulating substrate and the base portion is performed by cooling the heated first solder while it is in contact with the insulating substrate and the base portion, and then applying vibration to the first solder after it has fallen below the liquidus temperature. A method for manufacturing semiconductor modules.

[0112] (Note 6) A method for manufacturing a semiconductor module as described in any one of the appendices 1 to 5, The semiconductor element is joined to the upper surface of the insulating substrate via a second solder. The melting point of the second solder is higher than the melting point of the first solder. A method for manufacturing semiconductor modules.

[0113] (Note 7) The method for manufacturing a semiconductor module as described in Appendix 6, The joining of the insulating substrate and the base portion is performed by cooling the heated first solder while it is in contact with the insulating substrate and the base portion, and then applying vibration to the first solder after it has cooled to a temperature lower than the melting point of the second solder. A method for manufacturing semiconductor modules.

[0114] (Note 8) A method for manufacturing a semiconductor module as described in any one of the appendices 1 to 7, The base portion has a fin structure on the side opposite to the side that is joined to the insulating substrate. A method for manufacturing semiconductor modules.

[0115] (Note 9) A semiconductor module manufactured by the manufacturing method described in any one of the appendices 1 to 8, and a conversion circuit that converts the input power and outputs it, A control circuit is provided that outputs a control signal to the conversion circuit for controlling the conversion circuit. A method for manufacturing a power conversion device.

[0116] (Note 10) A semiconductor element bonded to the upper surface of an insulating substrate, The insulating substrate on which the semiconductor elements are bonded comprises a base portion which is bonded via a first solder, The insulating substrate and the base portion are joined by applying vibration to the heated first solder while it is in contact with the insulating substrate and the base portion, and then cooling the first solder after it has started to cool down. Semiconductor module.

[0117] (Note 11) A conversion circuit having the semiconductor module described in Appendix 10, and which converts the input power and outputs it, The system includes a control circuit that outputs a control signal to the conversion circuit for controlling the conversion circuit, Power converter. [Explanation of symbols]

[0118] 2 semiconductor elements, 30 solder, 31 solder, 32 solder, 2200 power converter, 2201 conversion circuit, 2203 control circuit.

Claims

1. A semiconductor element is bonded to the upper surface of an insulating substrate, The insulating substrate on which the semiconductor elements are bonded is joined to the base portion via the first solder. The joining of the insulating substrate and the base portion is performed by bringing the heated first solder into contact with the insulating substrate and the base portion, and then cooling the first solder while applying vibration to it after the temperature has started to decrease. The insulating substrate and the base portion are transported by conveyor rollers while in contact with the heated first solder, respectively. The conveyor rollers include eccentric rollers whose rotation centers are offset, The joining of the insulating substrate and the base portion involves cooling the first solder while the insulating substrate and the base portion are being transported by the conveyor roller, and then, when the first solder is being transported by the eccentric roller after the temperature has started to drop, the first solder is subjected to vibrations generated by the eccentric roller. A method for manufacturing semiconductor modules.

2. A semiconductor element is bonded to the upper surface of an insulating substrate, The insulating substrate on which the semiconductor elements are bonded is joined to the base portion via the first solder. The joining of the insulating substrate and the base portion is performed by bringing the heated first solder into contact with the insulating substrate and the base portion, and then cooling the first solder while applying vibration to it after the temperature has started to decrease. The joining of the insulating substrate and the base portion is performed by cooling the heated first solder while it is in contact with the insulating substrate and the base portion, and then applying vibration to the first solder after it has fallen below the liquidus temperature. A method for manufacturing semiconductor modules.

3. A method for manufacturing a semiconductor module according to claim 2, The bonding of the insulating substrate and the base portion is achieved by cooling the first solder after the temperature of the first solder has started to decrease, while applying vibrations generated by an ultrasonic horn that contacts the lower surface of the base portion. A method for manufacturing semiconductor modules.

4. A method for manufacturing a semiconductor module according to claim 2, The bonding between the insulating substrate and the base portion is achieved by cooling the first solder after the temperature has started to decrease, while applying vibrations generated by an ultrasonic horn that contacts the upper surface of the semiconductor element. A method for manufacturing semiconductor modules.

5. A method for manufacturing a semiconductor module according to claim 1 or 2, The semiconductor element is joined to the upper surface of the insulating substrate via a second solder. The melting point of the second solder is higher than the melting point of the first solder. A method for manufacturing semiconductor modules.

6. A method for manufacturing a semiconductor module according to claim 5, The joining of the insulating substrate and the base portion is performed by cooling the heated first solder while it is in contact with the insulating substrate and the base portion, and then applying vibration to the first solder after it has cooled to a temperature lower than the melting point of the second solder. A method for manufacturing semiconductor modules.

7. A method for manufacturing a semiconductor module according to claim 1 or 2, The base portion has a fin structure on the side opposite to the side that is joined to the insulating substrate. A method for manufacturing semiconductor modules.

8. A semiconductor module manufactured by the manufacturing method described in claim 1 or 2, and provided with a conversion circuit that converts and outputs the input power, A control circuit is provided that outputs a control signal to the conversion circuit for controlling the conversion circuit. A method for manufacturing a power conversion device.

9. A semiconductor element bonded to the upper surface of an insulating substrate, The insulating substrate on which the semiconductor elements are bonded comprises a base portion which is bonded via a first solder, The insulating substrate and the base portion are joined by applying vibration to the heated first solder while it is in contact with the insulating substrate and the base portion, and then cooling the first solder after it has started to cool down. The insulating substrate and the base portion are transported by conveyor rollers while in contact with the heated first solder, respectively. The conveyor rollers include eccentric rollers whose rotation centers are offset, The joining of the insulating substrate and the base portion involves cooling the first solder while the insulating substrate and the base portion are being transported by the conveyor roller, and then, when the first solder is being transported by the eccentric roller after the temperature has started to drop, the first solder is subjected to vibrations generated by the eccentric roller. Semiconductor module.

10. A semiconductor element bonded to the upper surface of an insulating substrate, The insulating substrate on which the semiconductor elements are bonded comprises a base portion which is bonded via a first solder, The insulating substrate and the base portion are joined by applying vibration to the heated first solder while it is in contact with the insulating substrate and the base portion, and then cooling the first solder after it has started to cool down. The joining of the insulating substrate and the base portion is performed by cooling the heated first solder while it is in contact with the insulating substrate and the base portion, and then applying vibration to the first solder after it has fallen below the liquidus temperature. Semiconductor module.

11. A semiconductor module according to claim 9 or 10, and a conversion circuit that converts and outputs the input power, The system includes a control circuit that outputs a control signal to the conversion circuit for controlling the conversion circuit, Power converter.

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