Semiconductor module, power conversion device and mobile object

Abstract

The insulating substrate (2) has first and second circuit patterns (4, 5). The semiconductor element (7) has first and second main electrodes (8, 9) respectively connected to the first and second circuit patterns (4, 5) and through which a main current flows. The first lead (12) is soldered to the first circuit pattern (5). The second lead (11) is ultrasonically bonded to the second circuit pattern (4).

Description

Technical Field

[0001] The present invention relates to a power semiconductor module, a power conversion device and a mobile object. Background Art

[0002] In the past, solder bonding was used to bond the terminals in semiconductor modules. However, it is difficult to achieve high-temperature operation of the semiconductor module, and the life relative to thermal cycles is reduced. To solve this problem, ultrasonic bonding is used to bond the terminals in the module (for example, refer to Patent Document 1). In addition, in order to improve the current carrying capacity of the main current path in the module, the application of DLB ​​(Direct Lead Bonding) and the like is promoted instead of wire bonding.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-109880 Summary of the invention

[0004] In semiconductor modules that use ultrasonic bonding for all joints, bonding and current carrying capacity are improved. However, if the chip in the module is damaged for some reason and the internal circuit is short-circuited, a larger overcurrent will flow than in semiconductor modules that use solder bonding, and the scale of damage inside the module may increase.

[0005] The present invention is proposed to solve the above-mentioned problems, and its purpose is to obtain a semiconductor module, a power conversion device and a mobile body that have the ability to cut off overcurrent, can achieve high-temperature operation, and can suppress the reduction of life relative to thermal cycles.

[0006] The semiconductor module involved in the present invention is characterized in that it comprises: an insulating substrate having a first and a second circuit pattern; a semiconductor element having a first and a second main electrode respectively connected to the first and the second circuit patterns and through which a main current flows; a first lead joined to the first circuit pattern by solder; and a second lead joined to the second circuit pattern by ultrasonic wave.

[0007] Effects of the Invention

[0008] In the present invention, the first lead is soldered to the circuit pattern through which the main current flows. When a large current flows due to damage inside the module, the solder melts, and the first lead and the circuit pattern become separated. Thus, the overcurrent can be cut off. In addition, by ultrasonically bonding the second terminal, the solder-bonded portion can be reduced. Thus, high-temperature operation can be achieved, and the reduction in life relative to thermal cycles can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a cross-sectional view showing the semiconductor module according to the first embodiment.

[0010] Figure 2 It is a cross-sectional view showing a semiconductor module according to the second embodiment.

[0011] Figure 3 It is a cross-sectional view showing a semiconductor module according to the third embodiment.

[0012] Figure 4 It is a cross-sectional view showing the bonding of U-shaped leads and the melting of solder.

[0013] Figure 5 It is a cross-sectional view showing a semiconductor module according to a fourth embodiment.

[0014] Figure 6 It is a block diagram showing the configuration of a power conversion system to which the power conversion device according to the fifth embodiment is applied.

[0015] Figure 7 This is a diagram showing a moving object according to the sixth embodiment. DETAILED DESCRIPTION

[0016] A semiconductor module, a power conversion device, and a mobile object according to the embodiments will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and duplicate descriptions may be omitted.

[0017] Implementation Method 1

[0018] Figure 1 1 is a cross-sectional view showing a semiconductor module according to Embodiment 1. An insulating substrate 2 is provided on a base plate 1. A lower surface electrode 3 is provided on the lower surface of the insulating substrate 2, and circuit patterns 4 and 5 are provided on the upper surface of the insulating substrate 2. The lower surface electrode 3 is bonded to the base plate 1 by solder 6.

[0019] A semiconductor element 7 is provided on the circuit pattern 4. Here, the semiconductor element 7 is an IGBT, and a collector electrode 8 is provided on the lower surface, and an emitter electrode 9 and a gate electrode (not shown) are provided on the upper surface. The collector electrode 8 on the lower surface of the semiconductor element 7 is solder-bonded to the circuit pattern 4, or sintered-bonded using Ag nanoparticles or Cu nanoparticles. The emitter electrode 9 on the upper surface of the semiconductor element 7 is connected to the circuit pattern 5 through an Al or Cu wire 10. The collector electrode 8 and the emitter electrode 9 are main electrodes through which the main current flows.

[0020] The lead 11 is ultrasonically bonded to the circuit pattern 4. The lead 12 is bonded to the circuit pattern 5 by solder 13. The main current is led out to the outside of the module through the leads 11 and 12. The housing 14 is provided on the outer periphery of the base plate 1 in a manner surrounding the insulating substrate 2, the semiconductor element 7, and the leads 11 and 12. The interior of the housing 14 is sealed by a sealing material 15.

[0021] In this embodiment, the lead 12 is soldered to the circuit pattern 5 through which the main current flows. When a large current flows due to damage inside the module, the solder 13 melts, and the lead 12 and the circuit pattern 5 become separated. In this separated state, the lead 12 is supported by the housing 14. In addition, since the packaging material 15 is not completely liquid, the packaging material 15 can also support the lead 12 at least for a short time when the overcurrent flows. In this way, the overcurrent can be cut off. In addition, by ultrasonically bonding the lead 11, the solder-bonded portion can be reduced. In this way, high-temperature operation can be achieved, and the reduction in life relative to the thermal cycle can be suppressed.

[0022] In addition, the semiconductor element 7 may be a MOSFET, in which case the collector electrode 8 is a drain electrode and the emitter electrode 9 is a source electrode. In addition, a lead is also connected to the gate electrode of the semiconductor element 7. Such a lead outside the main current path is not soldered to the circuit pattern of the insulating substrate 2, but ultrasonically bonded.

[0023] Implementation Method 2

[0024] Figure 2 1 is a cross-sectional view showing a semiconductor module according to Embodiment 2. The high-voltage side terminal, i.e., the lead 11, is joined to the circuit pattern 4 by solder 13. The low-voltage side terminal, i.e., the lead 12, is joined to the circuit pattern 5 by ultrasonic wave. Since the high-voltage side terminal is soldered, it is possible to cut off not only the overcurrent generated between the high-voltage side terminal and the low-voltage side terminal, but also the overcurrent generated between the high-voltage side terminal and the base plate 1. As a result, a failure mode such as a ground short circuit can be prevented. Other structures and effects are the same as those of Embodiment 1.

[0025] Implementation 3

[0026] Figure 3 1 is a cross-sectional view showing a semiconductor module according to Embodiment 3. A circuit pattern 16 is further provided on the upper surface of the insulating substrate 2. The lead 11 is ultrasonically bonded to the circuit pattern 4, and the lead 12 is ultrasonically bonded to the circuit pattern 5. The emitter electrode 9 of the semiconductor element 7 is connected to the circuit pattern 16 via the wire 10. One end of a U-shaped lead 17 is bonded to the circuit pattern 5 via solder 18, and the other end is ultrasonically bonded to the circuit pattern 16. The other structures are the same as those of Embodiment 1.

[0027] Figure 4 1 is a cross-sectional view showing the bonding of a U-shaped lead and the melting of solder. First, one end of the U-shaped lead 17 is solder-bonded to the circuit pattern 5. In this state, there is a gap 19 between the other end of the lead 17 and the circuit pattern 16. Next, the other end of the lead 17 is ultrasonically bonded to the circuit pattern 16. During this ultrasonic bonding, the lead 17 is plastically deformed to eliminate the gap 19, and residual stress is generated in the lead 17. If the solder 18 melts, one end of the lead 17 is peeled off from the circuit pattern 5 due to the residual stress. In this way, the overcurrent can be cut off.

[0028] Furthermore, the number of solder joints can be reduced by ultrasonically joining the other ends of the lead wires 17. This enables high-temperature operation and reduces the reduction in lifespan due to thermal cycles.

[0029] Implementation 4

[0030] Figure 5 1 is a cross-sectional view showing a semiconductor module according to Embodiment 4. Lead 11 is ultrasonically bonded to circuit pattern 4, and lead 12 is ultrasonically bonded to circuit pattern 5. One end of U-shaped lead 17 is bonded to emitter electrode 9 of semiconductor element 7 by solder 18, and the other end is ultrasonically bonded to circuit pattern 5. The other structures are the same as those of Embodiment 1.

[0031] When the solder 18 melts, one end of the lead 17 is peeled off from the semiconductor element 7 due to the residual stress as in the third embodiment. Thus, the overcurrent can be cut off. In addition, by ultrasonically bonding the other end of the lead 17, the solder bonding portion can be reduced. Thus, high temperature operation can be achieved, and the reduction in life relative to thermal cycles can be suppressed.

[0032] Here, when one end of the lead 17 becomes thicker or a heat sink is bonded to one end of the lead 17, even if the solder 18 melts, the lead 17 will not be peeled off from the semiconductor element 7 due to its weight, and the overcurrent cannot be cut off. In contrast, in the present embodiment, the lead 17 is a metal plate with a constant thickness from one end to the other end. Moreover, one end of the lead 17 is directly bonded to the emitter electrode 9 only via the solder 18, and there is no heat sink or the like between the two. Therefore, the lead 17 and the semiconductor element 7 can be separated when the solder 18 melts.

[0033] In addition, the semiconductor element 7 is not limited to being formed by silicon, and can also be formed by a wide bandgap semiconductor with a larger bandgap than silicon. Wide bandgap semiconductors are, for example, silicon carbide, gallium nitride materials, or diamond. The power semiconductor element formed by such a wide bandgap semiconductor can be miniaturized due to its high voltage resistance and allowable current density. By using the miniaturized element, the semiconductor module assembled with the element can also be miniaturized. In addition, since the element has high heat resistance, the heat sink fins of the radiator can be miniaturized, and the water cooling part can be air-cooled, so the semiconductor module can be further miniaturized. In addition, since the power loss of the element is low and efficient, the semiconductor module can be made efficient.

[0034] The semiconductor element 7 formed of a wide bandgap semiconductor is used at high temperatures. In contrast, by using the structures of the first to fourth embodiments, the semiconductor characteristics can be maintained even when used at high temperatures, the life of the bonding portion of the lead wire can be ensured, and high reliability can be achieved.

[0035] Implementation method 5

[0036] This embodiment applies the semiconductor modules according to the above-mentioned Embodiments 1 to 4 to a power conversion device. The present invention is not limited to a specific power conversion device, but the case where the present invention is applied to a three-phase inverter will be described below as Embodiment 5.

[0037] Figure 6 1 is a block diagram showing the structure of a power conversion system to which the power conversion device according to Embodiment 5 is applied. The power conversion system includes a power supply 100, a power conversion device 200, and a load 300. The power supply 100 is a DC power supply, and supplies DC power to the power conversion device 200. The power supply 100 can be composed of various power supplies, for example, it can be composed of a DC system, a solar cell, a storage battery, or a rectifier circuit or an AC / DC converter connected to an AC system. In addition, the power supply 100 can also be composed of a DC / DC converter that converts the DC power output from the DC system into a specified power.

[0038] The power conversion device 200 is a three-phase inverter connected between the power source 100 and the load 300, and converts the DC power supplied from the power source 100 into AC power, and supplies the AC power to the load 300. The power conversion device 200 includes: a main conversion circuit 201, which converts the DC power into AC power and outputs it; a drive circuit 202, which outputs a drive signal for driving each switching element of the main conversion circuit 201; and a control circuit 203, which outputs a control signal for controlling the drive circuit 202 to the drive circuit 202.

[0039] Load 300 is a three-phase motor driven by AC power supplied from power converter 200. Load 300 is not limited to a specific use, and is a motor mounted on various electrical devices, for example, a motor for hybrid vehicles or electric vehicles, railway vehicles, elevators, or air conditioners.

[0040] The details of the power conversion device 200 are described below. The main conversion circuit 201 has a switching element and a freewheeling diode (not shown), and the DC power supplied from the power supply 100 is converted into AC power and supplied to the load 300 by turning the switching element on and off. The specific circuit structure of the main conversion circuit 201 is various, but the main conversion circuit 201 involved in this embodiment is a 2-level three-phase full-bridge circuit, which can be composed of 6 switching elements and 6 freewheeling diodes respectively connected in reverse parallel to the switching elements. The semiconductor module involved in any of the above-mentioned embodiments 1 to 4 is applied to each switching element of the main conversion circuit 201. The 6 switching elements are connected in series two by two to form an upper and lower bridge arm, and each upper and lower bridge arm constitutes each phase (U phase, V phase, W phase) of the full-bridge circuit. Moreover, the output terminal of each upper and lower bridge arm, that is, the three output terminals of the main conversion circuit 201, is connected to the load 300.

[0041] The drive circuit 202 generates a drive signal for driving the switch element of the main conversion circuit 201, and supplies it to the control electrode of the switch element of the main conversion circuit 201. Specifically, according to the control signal from the control circuit 203 described later, the drive signal for turning the switch element into the on state and the drive signal for turning the switch element into the off state are output to the control electrode of each switch element. When the switch element is maintained in the on state, the drive signal is a voltage signal (on signal) greater than or equal to the threshold voltage of the switch element, and when the switch element is maintained in the off state, the drive signal is a voltage signal (off signal) less than or equal to the threshold voltage of the switch element.

[0042] The control circuit 203 controls the switching elements of the main conversion circuit 201 to supply the desired power to the load 300. Specifically, the time (on time) at which each switching element of the main conversion circuit 201 should be in the on state is calculated based on the power to be supplied to the load 300. For example, the main conversion circuit 201 can be controlled by PWM control that modulates the on time of the switching element corresponding to the voltage to be output. In addition, the control instruction (control signal) is output to the drive circuit 202 so that the on signal is output to the switching element that should be in the on state and the off signal is output to the switching element that should be in the off state at each moment. The drive circuit 202 outputs the on signal or the off signal as a drive signal to the control electrode of each switching element according to the control signal.

[0043] In the power conversion device according to this embodiment, the semiconductor devices according to Embodiments 1 to 4 are used as switching elements of the main conversion circuit 201, so a highly reliable power conversion device can be obtained. In addition, the power consumption of the cooler and the like of the power conversion device can be reduced.

[0044] In this embodiment, an example of applying the present invention to a 2-level three-phase inverter is described, but the present invention is not limited thereto and can be applied to various power conversion devices. In this embodiment, a 2-level power conversion device is used, but a 3-level or multi-level power conversion device may also be used. When power is supplied to a single-phase load, the present invention may also be applied to a single-phase inverter. In addition, when power is supplied to a DC load, the present invention may also be applied to a DC / DC converter or an AC / DC converter.

[0045] In addition, the power conversion device to which the present invention is applied is not limited to the case where the above-mentioned load is an electric motor. For example, it can also be used as a power supply device for an electric discharge machine or a laser processing machine, or an induction heating cooker or a contactless power supply system, and can also be used as a power conditioner for a solar power generation system or a power storage system.

[0046] Implementation 6

[0047] Figure 7 4 is a diagram showing a moving body according to Embodiment 6. Moving body 400 is a railway vehicle having power conversion device 200 according to Embodiment 5. Moving body 400 can move using the output from power conversion device 200. By improving the reliability of power conversion device 200, the reliability of moving body 400 can also be improved. In addition, by reducing the power consumption of power conversion device 200, the maintenance cycle of moving body 400 can be reduced, thereby achieving a longer life. In addition, moving body 400 is not limited to railway vehicles, and may be, for example, a hybrid vehicle, an electric vehicle, an elevator, etc.

[0048] Description of the label

[0049] 2 insulating substrate, 4, 5, 16 circuit pattern, 7 semiconductor element, 8 collector electrode, 9 emitter electrode, 11 lead, 12 lead, 13, 18 solder, 17 lead, 100 power supply, 200 power conversion device, 201 main conversion circuit, 202 drive circuit, 203 control circuit, 300 load, 400 moving body.

Claims

1. A semiconductor module, characterized in that: have: An insulating substrate having first and second circuit patterns; a semiconductor element having first and second main electrodes connected to the first and second circuit patterns, respectively, and through which a main current flows; a first lead connected to the first circuit pattern by solder; and a second lead which is ultrasonically bonded to the second circuit pattern, When the solder melts, the first lead is separated from the first circuit pattern.

2. The semiconductor module according to claim 1, characterized in that It also has a base plate bonded to the lower surface of the insulating substrate, The first lead is a high-voltage side terminal, and the second lead is a low-voltage side terminal.

3. A semiconductor module, characterized in that: have: An insulating substrate having first and second circuit patterns; a semiconductor element having a main electrode connected to one of the first and second circuit patterns and through which a main current flows; as well as A U-shaped lead wire, one end of which is joined to the first circuit pattern by solder, and the other end of which is joined to the second circuit pattern by ultrasonic wave. When the solder melts, one end of the lead is separated from the first circuit pattern.

4. A semiconductor module, characterized in that: have: an insulating substrate having a circuit pattern; a semiconductor element having a main electrode through which a main current flows; and A U-shaped lead wire has one end joined to the main electrode by solder and the other end joined to the circuit pattern by ultrasonic wave. When the solder melts, one end of the lead wire is separated from the main electrode.

5. The semiconductor module according to claim 4, characterized in that The lead wire is a metal plate with a constant thickness from the one end to the other end. The one end of the lead wire is directly joined to the main electrode only via the solder.

6. The semiconductor module according to any one of claims 1 to 5, characterized in that The semiconductor element is formed of a wide bandgap semiconductor.

7. A power conversion device, characterized in that: have: A main conversion circuit comprising the semiconductor module according to any one of claims 1 to 6, wherein the main conversion circuit converts input power and outputs the converted power; as well as a driving circuit that outputs a driving signal for driving the semiconductor module to the semiconductor module; as well as A control circuit outputs a control signal for controlling the drive circuit to the drive circuit.

8. A mobile object, characterized in that: A power conversion device according to claim 7.

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