Power module

Abstract

The present invention relates to a power module having a current detection function. The power module comprises: a shunt resistor connected to output-side wiring; and an output terminal connected to the shunt resistor. The shunt resistor has a laminated structure in which a resistor and an electrode are laminated. A slit is formed in a side portion of the output-side wiring at a mounting position of the shunt resistor, and a part of the output-side wiring is used as voltage detection wiring.

Description

Power Module

[0001] The present invention relates to a power module having a current detection function.

[0002] In recent years, while currents used in power electronic devices and apparatuses have been increasing, modules called power modules, which perform power conversion and control through switching of power semiconductors, have been actively developed.

[0003] Power modules increasingly use high heat dissipation substrates that allow large currents to pass therethrough, such as a substrate called a DBC substrate formed by a method of directly bonding copper to an alumina substrate. In addition, components such as a power semiconductor and a shunt resistor may be directly mounted on a plate-like wiring (busbar or lead frame) made of a copper plate or the like for use.

[0004] Japanese Patent Application Laid-Open No. 2018-170478 Japanese Patent Application Laid-Open No. 2022-066642

[0005] In a power module provided with a shunt resistor, the characteristic of temperature coefficient of resistance (TCR) is important in order to enable stable current detection without being affected by temperature fluctuations. Note that the temperature coefficient of resistance is an index indicating a rate of change in resistance value due to temperature.

[0006] Accordingly, an object of the present invention is to provide a power module that has a simple structure and can reduce the temperature coefficient of resistance in current detection by a shunt resistor.

[0007] In one embodiment, a power module is provided. The power module comprises a high-potential terminal connected to the high-potential side of a power supply source, a low-potential terminal connected to the low-potential side of the power supply source, an output wiring electrically connected to the high-potential terminal and a first semiconductor, and electrically connected to the first semiconductor, and electrically connected to the low-potential terminal and a second semiconductor, and electrically connected to the second semiconductor, a shunt resistor connected to the output wiring, and an output terminal connected to the shunt resistor. The shunt resistor has a laminated structure in which a resistor and electrodes are stacked, the shunt resistor is mounted on the output wiring and is arranged overlapping in the thickness direction of the shunt resistor between it and the output terminal, and a slit is formed on the side of the output wiring where the shunt resistor is mounted so that a part of the output wiring is used as voltage detection wiring.

[0008] In one embodiment, the slit has an open end on the outer casing of the output wiring and a closed end at a position closer to the shunt resistor than the open end. In another embodiment, the slit is formed on the side of the current path formed between the output terminal and the low-potential terminal.

[0009] According to the above method, the power module has a simple structure and can reduce the temperature coefficient of resistance in current detection using a shunt resistor.

[0010] Figure 1 shows one embodiment of a power module. Figure 2 shows one embodiment of a shunt resistor. Figure 3 shows one embodiment of a power semiconductor. Figure 4 shows one embodiment of a power module comprising a shunt resistor and a power semiconductor. Figure 5 is a circuit diagram showing one embodiment of a power module. Figure 6 is a structural diagram of the power module shown in Figure 4, specifically the P terminal (N terminal) section. Figure 7 is a structural diagram of the shunt resistor section of the power module shown in Figure 4. Figure 8 shows pin terminals and wiring connected to each other by bonding wires. Figure 9A shows a first current path formed between the high-potential side terminal and the output terminal. Figure 9B shows a second current path formed between the output terminal and the low-potential side terminal. Figure 9C shows the distance between the shunt resistor and the slit. Figure 10 shows another embodiment of the slit.

[0011] Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. In the multiple embodiments described below, the configuration of one embodiment that is not specifically described is the same as that of the other embodiments, so redundant descriptions are omitted.

[0012] Figure 1 shows one embodiment of a power module. The power module 1 is a semiconductor module equipped with power semiconductors and has a current detection function using a shunt resistor. As shown in Figure 1, the power module 1 comprises a case 2 that houses the components of the power module 1 (described later), a high-potential side terminal (P terminal) 3 connected to the high-potential side of a power supply source (not shown), a low-potential side terminal (N terminal) 4 connected to the low-potential side of the power supply source, an output terminal 5 connected to a shunt resistor 20 (see Figure 2, described later), and a filler material 10 filled inside the case 2.

[0013] The high-potential terminal 3 and the low-potential terminal 4 are located on one side of the case 2, while the output terminal 5 is located on the other side (opposite side) of the case 2. Furthermore, the power module 1 is equipped with a plurality of pin terminals 6 located between the high-potential terminal 3 and the low-potential terminal 4 and the output terminal 5.

[0014] Figure 2 shows an embodiment of a shunt resistor. The shunt resistor 20 is a component of the power module 1. As shown in Figure 2, the shunt resistor 20 is a resistor having a stacked structure (vertical structure) stacked in the thickness direction. The shunt resistor 20 has plate-shaped first electrodes 22A and second electrodes 22B, and a plate-shaped resistive element 21 disposed between the first electrodes 22A and second electrodes 22B. The size of the shunt resistor 20 is, for example, about 3 mm to 8 mm on each side and about 0.3 mm to 2 mm thick.

[0015] The materials for the first electrode 22A and the second electrode 22B are, for example, highly conductive metallic materials such as Cu, Ni, Al, Ag, and Au. The material for the resistor 21 is, for example, a metallic material suitable for current detection such as Cu-Ni, Cu-Mn, or Ni-Cr, or a composite material made by mixing metal and insulating powders.

[0016] Figure 3 shows one embodiment of a power semiconductor. The power semiconductor 30 is a component of the power module 1. As shown in Figure 3, the power semiconductor 30 has a diode terminal 31 connected to a diode built into the power semiconductor 30, a source 32 as the input terminal for carriers in the transistor, a gate 33 that controls the flow of carriers, and a drain 34 as the output terminal for carriers.

[0017] Figure 4 shows one embodiment of a power module comprising a shunt resistor and power semiconductors. Figure 5 is a circuit diagram showing one embodiment of the power module. In the embodiment shown in Figure 4, the filler material 10 is not shown. The power module 1 comprises four power semiconductors 30A, 30B, 30C, and 30D. The aforementioned power semiconductors 30 are a collective term for power semiconductors 30A, 30B, 30C, and 30D. The number of power semiconductors 30 does not necessarily have to be four; the power module 1 may comprise at least two power semiconductors 30 (see Figure 5).

[0018] The power module 1 includes a first wiring 50A to which the high-potential terminal 3 is connected, a second wiring 50B to which the low-potential terminal 4 is connected, and a third wiring (output wiring) 50C electrically connected to the power semiconductor 30 (in Figure 4, power semiconductor 30A or power semiconductor 30B). Hereinafter in this specification, the first wiring 50A, the second wiring 50B, the third wiring 50C, and the voltage detection wiring 50D may be referred to as wiring 50 without any particular distinction.

[0019] The wiring 50 is arranged on the substrate 40. The substrate 40 is, for example, a ceramic substrate, and the combination of the substrate 40 and the wiring 50 is a DBC (Direct Bonded Copper) substrate.

[0020] Power semiconductors 30A and 30B are arranged on the first wiring 50A and are electrically connected to the third wiring 50C by bonding wire WR. The high-potential terminal 3 is electrically connected to power semiconductors 30A and 30B. Power module 1 does not necessarily need to include both power semiconductors 30A and 30B arranged on the first wiring 50A; it may also have a configuration that includes either power semiconductor 30A or power semiconductor 30B.

[0021] Power semiconductors 30C and 30D are arranged on the third wiring 50C and are electrically connected to the third wiring 50C. Power semiconductors 30C and 30D are electrically connected to the second wiring 50B by bonding wire WR. Therefore, the low-potential terminal 4 and power semiconductors 30C and 30D are electrically connected.

[0022] The shunt resistor 20 is mounted on the third wiring 50C and is positioned between the third wiring 50C and the output terminal 5, overlapping in the thickness direction of the shunt resistor 20. The power module 1 includes a voltage detection wiring 50D located on the side of the third wiring 50C where the shunt resistor 20 is mounted, and a slit SL formed in the voltage detection wiring 50D. The voltage detection wiring 50D constitutes a part of the third wiring 50C.

[0023] The slit SL has an open end SLa located on the outer casing of the third wiring 50C, and a closed end SLb located closer to the shunt resistor 20 than the open end SLa. The slit SL having this configuration is positioned adjacent to the shunt resistor 20. The width of the slit SL is formed to be approximately the same as the width between the wirings, that is, the spacing between the first wiring 50A, the second wiring 50B, and the third wiring 50C.

[0024] The power module 1 includes a voltage detection terminal 6D-1 electrically connected to the voltage detection wiring 50D by a bonding wire WR, and a voltage detection terminal 6D-2 electrically connected to the output terminal 5 by a bonding wire WR.

[0025] The power module 1 includes source common wiring 60A, 60B and source terminals 6A-1, 6A-2 electrically connected to each other by bonding wire WR, gate terminals 6B-1, 6B-2 and gate common wiring 70A, 70B electrically connected to each other by bonding wire WR, a thermistor 80 and a temperature detection terminal 6C electrically connected to the thermistor 80.

[0026] The pin terminal 6 (see Figure 1) is a collective term for the source terminals 6A-1 and 6A-2, the gate terminals 6B-1 and 6B-2, the temperature detection terminal 6C, and the voltage detection terminals 6D-1 and 6D-2. Therefore, in this specification, the source terminals 6A-1 and 6A-2, the gate terminals 6B-1 and 6B-2, the temperature detection terminal 6C, and the voltage detection terminals 6D-1 and 6D-2 may all be referred to as pin terminal 6 without any particular distinction.

[0027] Figure 6 is a structural diagram of the power module shown in Figure 4, and is a structural diagram of the P terminal 3 (N terminal 4) portion. As shown in Figure 6, the high-potential terminal 3 (and the low-potential terminal 4) is fixed to the first wiring 50A (and the second wiring 50B) by solder SD. In addition to solder, the fixing method may also involve a conductive material.

[0028] Figure 7 is a structural diagram of the shunt resistor portion of the power module shown in Figure 4. As shown in Figure 7, the shunt resistor 20 is located between the third wiring 50C and the output terminal 5. The slit SL is located adjacent to the shunt resistor 20 and corresponds to a notch that penetrates the third wiring 50C in the thickness direction.

[0029] As shown in Figure 7 (and Figure 4), the bonding wire WR connected to voltage detection terminal 6D-1 is connected to voltage detection position PA on voltage detection wiring 50D. As shown in Figure 4, the bonding wire WR connected to voltage detection terminal 6D-2 is connected to voltage detection position PB located on output terminal 5 above shunt resistor 20.

[0030] Figure 8 shows pin terminals and wiring connected to each other by bonding wire WR. As shown in Figure 8, the pin terminals 6 and wiring 50 are electrically connected to each other by bonding wire WR.

[0031] Figure 9A shows the first current path formed between the high-potential terminal and the output terminal. Figure 9B shows the second current path formed between the output terminal and the low-potential terminal. Figures 9A and 9B show a simplified configuration of Figure 4. In the embodiment shown in Figure 9A, the first current path is formed from the high-potential terminal 3 through power semiconductors 30A and 30B toward the output terminal 5 (see dotted arrow in Figure 9A). In the embodiment shown in Figure 9B, the second current path is formed from the output terminal 5 through power semiconductors 30C and 30D toward the low-potential terminal 4 (see dotted arrow in Figure 9B).

[0032] As is clear from a comparison of Figures 9A and 9B, the first current path is formed at a position spaced apart from the slit SL, and the shunt resistor 20 is positioned between the first current path and the slit SL. The second current path is formed at a position closer to the slit SL than the first current path. It can be said that the slit SL is positioned on the side of the second current path. Specifically, the slit SL is formed on the side of the second current path which is formed between the output terminal 5 and the low-potential side terminal 4.

[0033] According to this embodiment, by forming a slit SL, the temperature coefficient of resistance in current detection using a shunt resistor can be reduced. In other words, since the current mainly flows along the current path, the current density is high near the current path and decreases as it moves away from the current path. Therefore, by simply forming a slit SL in close proximity to the current path, it is possible to suppress the change in impedance due to the current path and reduce the temperature coefficient of resistance.

[0034] Figure 9C shows the distance between the shunt resistor and the slit. The temperature coefficient of resistance can vary depending on the distance DT between the shunt resistor 20 and the slit SL. For example, when the distance DT is zero, i.e., when the closed end SLb of the slit SL is connected to the shunt resistor 20, the temperature coefficient of resistance can be reduced significantly. In particular, the temperature coefficient of resistance when a first current path is formed is smaller than the temperature coefficient of resistance when a second current path is formed.

[0035] A sample of power module 1 with a distance DT of approximately 0.3 mm was prepared, and the resistance value and temperature coefficient of resistance of the shunt resistor in the sample were measured. The measurement results showed that the resistance value when the second current path was formed was 362 μΩ, and the resistance value when the first current path was formed was 358 μΩ. The difference between these resistance values ​​is 4 μΩ. The temperature coefficient of resistance when the second current path was formed was 24 ppm / °C, and the temperature coefficient of resistance when the first current path was formed was -21 ppm / °C.

[0036] A sample of power module 1 without a slit SL was prepared, and the resistance value and temperature coefficient of resistance of the sample's shunt resistor were measured. The measurement results showed that the resistance value when the second current path was formed was 374 μΩ, and the resistance value when the first current path was formed was 359 μΩ. The difference between these resistance values ​​is 15 μΩ. The temperature coefficient of resistance when the second current path was formed was 230 ppm / °C, and the temperature coefficient of resistance when the first current path was formed was 121 ppm / °C.

[0037] In this way, by forming the slit SL, it is possible to suppress the change in impedance due to the current path, and a significant effect of stabilizing voltage sensing can be confirmed.

[0038] Simulation results confirm that as the distance DT increases, the difference between the first resistance value when the first current path is formed and the second resistance value when the second current path is formed also increases. For example, when the distance DT is zero, the difference between the first and second resistance values ​​is about 3 μΩ, but when the distance DT is 0.8 mm, the difference between the first and second resistance values ​​is about 6 μΩ.

[0039] Figure 10 shows another embodiment of the slit. In the embodiment described above, the slit SL is formed on the side of the second current path (see Figure 9B). In the embodiment shown in Figure 10, the slit SL may be located on the opposite side of the output terminal 5 from the position of the slit SL described with reference to Figure 9B. In other words, the slit SL is formed on the side of the first current path (i.e., in a position closer to the first current path than to the second current path). The slit SL has an L-shape.

[0040] In the embodiment shown in Figure 10, the slit SL is formed in the voltage detection wiring 50D which constitutes a part of the third wiring 50C, and has an open end SLa located on the outer casing of the third wiring 50C and a closed end SLb located adjacent to the shunt resistor 20.

[0041] The embodiments described above are intended to enable persons with ordinary skill in the art to implement the present invention. Various modifications of the above embodiments can be made naturally by those skilled in the art, and the technical idea of ​​the present invention can be applied to other embodiments as well. Therefore, the present invention is not limited to the embodiments described, but is to be interpreted in the broadest sense according to the technical idea defined by the claims.

[0042] According to the present invention, it becomes possible to improve the precision, stability, and miniaturization of power modules. The present invention can contribute to Goal 7 "Affordable and Clean Energy," Goal 9 "Industry, Innovation and Infrastructure," and Goal 12 "Responsible Consumption and Production," which are among the United Nations-led Sustainable Development Goals (SDGs).

[0043] This invention can be used in power modules equipped with a current detection function.

[0044] 1 Power module 2 Case 3 High-potential terminal (P terminal) 4 Low-potential terminal (N terminal) 5 Output terminal 6 Pin terminals 6A-1, 6A-2 Source terminals 6B-1, 6B-2 Gate terminal 6C Temperature detection terminal 6D-1, 6D-2 Voltage detection terminal 10 Filling material 20 Shunt resistor 21 Resistor 22A First electrode 22B Second electrode 30 (30A, 30B, 30C, 30D) Power semiconductor 31 Diode terminal 32 Source 33 Gate 34 Drain 50 Wiring 50A First wiring 50B Second wiring 50C Third wiring (output side wiring) 50D Voltage detection wiring 60A, 60B Common source wiring 70A, 70B Common gate wiring 80 Thermistor WR Bonding wire SL Slit SLa: Open end; SLb: Closed end; PA: Voltage detection position; PB: Voltage detection position; DT: Distance

Claims

1. A power module comprising: a high-potential terminal connected to the high-potential side of a power supply source; a low-potential terminal connected to the low-potential side of the power supply source; an output wiring electrically connected to the high-potential terminal and a first semiconductor, and electrically connected to the first semiconductor, and electrically connected to the low-potential terminal and a second semiconductor, and electrically connected to the second semiconductor; a shunt resistor connected to the output wiring; and an output terminal connected to the shunt resistor, wherein the shunt resistor has a laminated structure in which a resistor and electrodes are stacked; the shunt resistor is mounted on the output wiring and is arranged between it and the output terminal overlapping in the thickness direction of the shunt resistor; and a slit is formed on the side of the output wiring where the shunt resistor is mounted, so that a part of the output wiring is used as voltage detection wiring.

2. The power module according to claim 1, wherein the slit has an open end on the outer casing of the output wiring and a closed end at a position closer to the shunt resistor than the open end.

3. The power module according to claim 1, wherein the slit is formed on the side of the current path formed between the output terminal and the low-potential side terminal.

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