Current detection device

Abstract

The present invention relates to a current detection device. The current detection device includes a first detection conductor and a second detection conductor. The first detection conductor is connected to a first region, and the second detection conductor is connected to a second region.

Description

Current detection device

[0001] The present invention relates to a current detection device.

[0002] In recent years, as the current used in electronic devices has become larger, there has been active development of so-called power modules, which convert and control power by switching power semiconductors.

[0003] Power modules often use high-heat-dissipation substrates that can handle large currents, such as ceramic substrates called DBC substrates, which are formed by bonding copper directly to an alumina substrate. Components such as power semiconductors and shunt resistors are sometimes mounted directly on copper-plated wiring (bus bars or lead frames).

[0004] JP 2022-066642 A JP 2018-170478 A

[0005] Japanese Patent Application Laid-Open No. 2006-129999 discloses a mounting structure for a shunt resistor device having lead wires arranged between adjacent current-carrying patterns. However, such a mounting structure requires space for the lead wires, which increases the distance between the current-carrying patterns. As a result, it is difficult to achieve a compact mounting structure.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a current detection device that can be made smaller.

[0007] In one aspect, a current detection device is provided, comprising: a resistor having a laminated structure in which a first electrode, a resistive element, and a second electrode are laminated in a thickness direction; a first conductor connected to the first electrode; a second conductor connected to the second electrode; and first and second detection conductors for detecting a voltage, wherein the first detection conductor is connected to a first region on an upper surface of the first electrode or the first conductor, on an opposite side facing an inflow portion of the first conductor, and the second detection conductor is connected to a second region of the second conductor, on a side side of the inflow portion, on a side of the second electrode.

[0008] In one aspect, the first region is a region from the center of the first electrode to the opposing side. In one aspect, the second conductor is a wiring pattern formed on a circuit board, the second electrode and the second conductor are connected by solder, the second conductor has a boundary portion formed in a region along one side of the second electrode, and the second detection conductor is connected to a side of the boundary portion. In one aspect, the boundary portion is a through slit, a non-through slit, an insulating film, or a step formed in the second conductor.

[0009] In one aspect, the boundary portion has a linear portion that extends in a direction perpendicular to one side of the second electrode. In one aspect, the second detection conductor is connected to the inflow portion closer to the boundary portion.

[0010] By connecting the first sensing conductor to the first region and the second sensing conductor to the second region, the current sensing device can be made smaller.

[0011] FIG. 9 is a perspective view showing an embodiment of a resistor. FIG. 10 is a top view showing an embodiment of a power module including a current detection device including a resistor. FIG. 11 is a perspective view showing wires connecting each of a first voltage detection terminal and a second voltage detection terminal to a bus bar and a wiring. FIG. 12 is a view showing an area in the current detection device to which wires are connected. FIG. 13 is a view showing an area in the current detection device to which wires are connected. FIG. 14 is a view showing a relationship between a wire connection position and a temperature coefficient of resistance (TCR). FIG. 15 is a view showing a boundary for preventing solder flow. FIG. 9A is a view showing an example of a boundary. FIG. 9B is a view showing an example of a boundary. FIG. 9C is a view showing an example of a boundary. FIG. 9D is a view showing an example of a boundary. FIG. 16 is a view showing a modified example of a boundary. FIG. 17 is a view showing a boundary for eliminating the influence of TCR. FIG. 18 is a view showing a modified example of a boundary. FIG. 19 is a view showing a modified example of a boundary. FIG. 20 is a view showing a modified example of a boundary. 15A is a diagram showing a modified example of a boundary portion; FIG. 15B is a diagram showing a modified example of a boundary portion; FIG. 15C is a diagram showing another embodiment of a current detection device; FIG. 15D is a diagram showing another embodiment of a current detection device;

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, identical or corresponding components are designated by the same reference numerals, and duplicated descriptions will be omitted. In the multiple embodiments described below, the configuration of an embodiment that is not particularly described is the same as that of other embodiments, and therefore duplicated descriptions will be omitted.

[0013] Fig. 1 is a perspective view showing one embodiment of a resistor. As shown in Fig. 1, the resistor 10 has a laminated structure in which elements are laminated in the thickness direction. The resistor 10 has a plate-shaped first electrode 12 and a plate-shaped second electrode 13, and a plate-shaped resistive element 11 disposed between the first electrode 12 and the second electrode 13.

[0014] The resistor 10 is a shunt resistor with a vertical structure (a laminated structure) used for current detection. In the embodiment shown in Fig. 1, the resistor 11 has a square or rectangular shape, but the shape of the resistor 11 can be designed arbitrarily.

[0015] The material of the first electrode 12 and the second electrode 13 is a highly conductive metal material such as Cu. The material of the resistor 11 is a metal material suitable for current detection, such as a Cu-Ni, Cu-Mn, or Ni-Cr material, or a composite material containing a metal.

[0016] Fig. 2 is a top view showing one embodiment of a power module equipped with a current detection device including a resistor. As shown in Fig. 2, a current detection device 100 is connected to a power module 200. The current detection device 100 includes a plate-shaped bus bar 20 (first conductor). A current to be measured flows through the bus bar 20. The bus bar 20 as the first conductor is connected to the resistor 10 by, for example, soldering. The bus bar 20 is, for example, a U-terminal, V-terminal, or W-terminal of a three-phase AC current.

[0017] 2 , power module 200 includes plate-shaped bus bars 21 and 22. Bus bar 21 is a negative terminal, and bus bar 22 is a positive terminal. Current detection device 100 (or power module 200) includes plate-shaped wiring 23 (second conductor), wiring 24, and wiring 25.

[0018] The wires 23 to 25 are wiring patterns formed on a circuit board, and are, for example, thick copper patterns made of copper. The current to be measured flows through the wire 23. The wire 23, which serves as a second conductor, is connected to the resistor 10 (more specifically, the second electrode 13) by, for example, soldering. In this way, the resistor 10 is connected to the bus bar 20 and the wires 23 in the vertical direction.

[0019] The power module 200 includes one or more power devices 30. The power devices 30 are connected to the wirings 23 to 25 directly or via bonding wires 40. The bonding wires 40 are made of metal (e.g., Au, Ag, Cu, Al, etc.).

[0020] The power module 200 includes a rectangular case 45. The case 45 connects the inside of the case 45 to the outside of the case 45 via the bus bars 20 to 22.

[0021] The power module 200 includes an insulating substrate 26. The insulating substrate 26 is made of, for example, ceramics. In one embodiment, the insulating substrate 26 may be made of a material such as silicon nitride, aluminum nitride, alumina, or zirconia. In one embodiment, the insulating substrate 26 may be made of glass epoxy, polyimide, or Teflon (registered trademark).

[0022] The power module 200 includes a first voltage detection terminal 51 and a second voltage detection terminal 52. A voltage signal for measuring a current is output to the outside via the first voltage detection terminal 51 and the second voltage detection terminal 52.

[0023] The current detection device 100 includes a bonding wire (first detection conductor) 41 and a bonding wire (second detection conductor) 42 for detecting voltage. The first voltage detection terminal 51 is connected to the bus bar 20 via the bonding wire 41. The second voltage detection terminal 52 is connected to the wiring 23 via the bonding wire 42. Hereinafter, the bonding wires 41 and 42 may be simply referred to as the wires 41 and 42.

[0024] 3 is a perspective view showing wires connecting the first and second voltage detection terminals to the busbars and wiring. As shown in FIG. 3, one end of wire 41 serving as a first detection conductor is connected to the upper surface of busbar 20 serving as a first conductor. The other end of wire 41 is connected to first voltage detection terminal 51. One end of wire 42 serving as a second detection conductor is connected to wiring 23 serving as a second conductor. The other end of wire 42 is connected to second voltage detection terminal 52.

[0025] 4 and 5 are diagrams showing regions in the current detection device where wires are connected. Fig. 4 is a front view of the current detection device 100, and Fig. 5 is a plan view of the current detection device 100. Note that the bus bar 20 is not shown in Fig. 5.

[0026] 4 and 5 , the current flowing through the current detection device 100 (see the dotted arrows) flows horizontally in the bus bar 20 and diagonally up and down in the resistor 10. More specifically, the current flowing diagonally up and down flows from the bus bar 20 toward the wiring 23, away from the end edge EC of the wiring 23. The current then flows horizontally in the wiring 23.

[0027] Hereinafter, in this specification, the starting point where the current from the bus bar 20 flows into the resistor 10 is defined as an inflow portion CI, and the ending point where the current flows out of the resistor 10 is defined as an outflow portion CO (see FIGS. 4 and 5).

[0028] As shown in Figures 4 and 5, the current detection device 100 has a first region WBR1 located on the upper surface (connection portion with the first electrode 12) of the bus bar 20 connected to the resistor 10 (more specifically, the first electrode 12), and a second region WBR2 formed on the wiring 23 and located to the side of the resistor 10 (more specifically, the second electrode 13).

[0029] The first region WBR1 is a specific region formed on the bus bar 20 for connecting the wire 41. The second region WBR2 is a specific region formed on the wiring 23 for connecting the wire 42.

[0030] In the present embodiment, the wire 41 is connected to the bus bar 20, but the wire 41 may also be connected to the first electrode 12. In this case, the first region WBR1 is a region formed on the first electrode 12 for connecting the wire 41. In this manner, the first region WBR1 is formed on the bus bar 20 (or the first electrode 12). The specific ranges of the first region WBR1 and the second region WBR2 will be described below.

[0031] 5, the longitudinal direction of the current detection device 100 (more specifically, the resistor 10) is defined as the x-direction, and the direction perpendicular to the x-direction is defined as the y-direction. In this case, the first region WBR1 has a width a extending along the x-direction.

[0032] 5, the width a of the first region WBR1 is half the length of the entire resistor 10 in the x direction. In one embodiment, more preferably, the width a may be one-third the length of the entire resistor 10 in the x direction. Note that the first region WBR1 extends over the entire resistor 10 in the y direction.

[0033] 4 and 5, the first region WBR1 is located on the opposite side of the inlet portion CI. The current detection device 100 (i.e., the busbar 20 and / or the resistor 10) has an opposing side EA located on the opposite side of the inlet portion CI (see FIG. 5), and the first region WBR1 is located on the opposing side EA side. For example, the first region WBR1 is a region from the center of the first electrode 12 to the opposing side EA.

[0034] The wire 41 is connected to the first region WBR1 on the opposing side EA side that faces the inlet portion CI. Therefore, the connection position WBPa of the wire 41 with respect to the first region WBR1 is located at a position spaced apart from the inlet portion CI.

[0035] The second region WBR2 is disposed on a side of the inlet portion CI. More specifically, the current detection device 100 (i.e., the busbar 20 and / or the resistor 10) has a side edge EB disposed on a side of the inlet portion CI (see FIG. 5). The second region WBR2 is disposed on the side of the side edge EB and is located on the side of the second electrode 13. When the current detection device 100 is viewed from above, the side edge EB extends perpendicular to the opposing side EA.

[0036] The current detection device 100 has a width b extending in the x direction from the end edge EC of the wiring 23 to an extension line (not shown) of the opposing edge EA. The second region WBR2 is disposed within the range of the width b. In the embodiment shown in FIG. 5 , the second region WBR2 has a length shorter than the width b, but the second region WBR2 may have a length equal to the width b.

[0037] The wire 42 is connected to the second region WBR2 located on the side edge EB side of the inflow portion CI and on the side of the second electrode 13. Therefore, the connection position WBPb of the wire 42 with respect to the second region WBR2 is located at a position opposite to the outflow portion CO (more specifically, at a position adjacent to the inflow portion CI).

[0038] In this embodiment, the connection position WBPb is located on the inflow portion CI side of the center portion of the wiring 23 in the width b. In another embodiment, the connection position WBPb may be located on the end side EC side of the position of the width b corresponding to the inflow portion CI.

[0039] According to this embodiment, the current detection device 100 is configured such that the wire 41 is connected to the first region WBR1 and the wire 42 is connected to the second region WBR2. The first region WBR1 and the second region WBR2 are disposed adjacent to each other in the y direction (i.e., width direction) perpendicular to the x direction (i.e., longitudinal direction) of the current detection device 100.

[0040] Therefore, compared to the mounting structure disclosed in Patent Document 1, the current detecting device 100 can arrange the connection position WBPa of the wire 41 and the connection position WBPb of the wire 42 closer to each other. As a result, the current detecting device 100 can be made smaller.

[0041] 6 and 7 are diagrams showing the relationship between the wire connection position and the temperature coefficient of resistance (TCR). Fig. 7 shows the TCR when the connection position WBPa of wire 41 is changed from position A1 to A4 and the connection position WBPb of wire 42 is changed from position B1 to B5. Note that TCR is an index that indicates the rate of change in resistance value due to temperature.

[0042] Since the current flows mainly along the current path formed in the current detection device 100 (see the dotted arrows in FIGS. 4 and 5), the current density is high near the current path and decreases with increasing distance from the current path. Therefore, the TCR in the current detection device 100 can be changed by changing the connection position WBPa of the wire 41.

[0043] When the connection position WBPa of the wire 41 is determined to be position A1, the TCR changes in the negative direction compared to the TCR when the connection position WBPa is determined to be on the inflow portion CI side, for example, position A4. Similarly, when the connection position WBPb of the wire 42 is determined to be position B5, the TCR changes in the negative direction compared to the TCR when the connection position WBPb is determined to be on the outflow portion CO side, for example, position B1.

[0044] As is clear from Figures 6 and 7, the TCR can be reduced by determining the connection position WBPa at a position spaced apart from the inlet section CI (more specifically, the first region WBR1) and determining the connection position WBPb at a position spaced apart from the outlet section CO (more specifically, the second region WBR2).

[0045] Although not shown, in one embodiment, the TCR can be further reduced by reducing the distance c (see FIG. 5) between the side edge EB and the connection position WBPb. Therefore, the TCR can be adjusted by moving the connection position WBPb closer to the side edge EB.

[0046] As described above, the wiring 23 is connected to the second electrode 13 by soldering. However, such a connection may cause the solder to wet and spread to the second region WBR2 side (i.e., the solder may flow out) due to the close contact between the resistor 10 and the wiring 23.

[0047] If the solder flows out into the second region WBR2, the solder may interfere with the bonding of the wire 42, and as a result, the current detection device 100 may not be able to obtain sufficient current measurement accuracy. Therefore, in the embodiment shown below, the configuration of the current detection device 100 that can obtain sufficient current measurement accuracy will be described with reference to the drawings.

[0048] 8 is a diagram showing a boundary portion for preventing solder flow. As shown in Fig. 8, the current detection device 100 includes a boundary portion BD formed in the wiring 23 serving as the second conductor. The boundary portion BD is formed in a region Ra along one side (more specifically, side EB) of the second electrode 13.

[0049] The region Ra is formed between the resistor 10 on the wiring 23 and the second region WBR2. The wire 42 as the second detection conductor is connected to the side of the boundary portion BD (i.e., the second region WBR2 adjacent to the region Ra).

[0050] 9A to 9D are diagrams showing an example of a boundary portion. In the embodiment shown in Fig. 9A, the boundary portion BD is an insulating resin member printed on the wiring 23. The boundary portion BD as a resin member is a protrusion extending from above the wiring 23, and corresponds to a barrier that prevents the solder from flowing out.

[0051] 9B , the boundary portion BD is a concave non-through slit formed in the wiring 23. By forming the non-through slit, the solder flows into the non-through slit but does not flow into the second region WBR2. As a result, the non-through slit can prevent the solder from flowing out into the second region WBR2.

[0052] 9C , the boundary portion BD is an insulating film (oxide film) formed on the wiring 23. The boundary portion BD as an insulating film is formed by irradiating a specific portion of the wiring 23 with a laser to oxidize a part of the wiring 23. Such an oxide film is difficult for solder to wet, and therefore prevents the solder from flowing out into the second region WBR2.

[0053] 9D, the boundary portion BD is a through slit formed in the wiring 23. The boundary portion BD as a through slit penetrates all the way to the insulating substrate 26. The through slit prevents the solder from flowing out into the second region WBR2, similar to the non-through slit described with reference to FIG.

[0054] 10 and 11 are diagrams showing modified examples of the boundary portion. In the embodiment shown in Fig. 10, the boundary portion BD has an L-shape when the wiring 23 is viewed from above. More specifically, a portion of the boundary portion BD extends parallel to the x-direction of the resistor 10 and is disposed between the resistor 10 and the second region WBR2. The other portion of the boundary portion BD extends parallel to the y-direction of the resistor 10 and extends in a direction away from the side edge EB.

[0055] In this way, the L-shaped boundary portion BD arranged around the second region WBR2 can prevent solder from flowing out into the second region WBR2. The specific structure (except for the shape) of the boundary portion BD is not particularly limited. For example, the boundary portion BD has the same structure as the structure described with reference to Figures 9A to 9D (i.e., the resin member, the non-penetrating slit, the insulating film, or the penetrating slit).

[0056] In the embodiment shown in FIG. 11 , the boundary portion BD is a convex step (chip, pad) formed on the wiring 23. The second region WBR2 is formed on the boundary portion BD. By forming the second region WBR2 on the convex boundary portion BD, it is possible to prevent solder from contacting the second region WBR2. The boundary portion BD as a step is made of a metal such as copper, and is soldered to the wiring 23. In one embodiment, a coating such as tin may be formed on the surface of the boundary portion BD.

[0057] Indeed, as in the above-described embodiment, providing the boundary portion BD between the resistor 10 and the second region WBR2 can prevent the solder from interfering with the bonding of the wire 41. On the other hand, in order to prevent the solder from flowing out to the connection position WBPb, it is possible to determine the connection position WBPb outside the region where the solder flows out. In other words, it is possible to sufficiently separate the connection position WBPb from the resistor 10.

[0058] However, in this case, the metal (e.g., copper) of the wiring 23 may adversely affect the TCR. Therefore, in the following embodiment, the configuration of a current detection device 100 that can eliminate the effect of the TCR will be described with reference to the drawings.

[0059] 12 is a diagram illustrating a boundary portion for eliminating the influence of TCR. In the embodiment illustrated in FIG. 12, the current detection device 100 includes a boundary portion BD formed in a region Rb of the wiring 23 along one side of the second electrode 13. The wire 42 is connected to the side of the boundary portion BD.

[0060] The region Rb is disposed at a position farther away from the side edge EB of the resistor 10 than the second region WBR2. The boundary portion BD formed in the region Rb extends parallel to the x-direction of the current detection device 100. In this embodiment, the boundary portion BD is a slit (a non-penetrating slit or a penetrating slit) formed in the wiring 23. The formation of the boundary portion BD can improve the TCR.

[0061] 13 is a diagram showing a modified example of the boundary portion. In the embodiment shown in Fig. 13, the boundary portion BD has an L-shape when the wiring 23 is viewed from above. More specifically, a portion of the boundary portion BD extends parallel to the x-direction of the resistor 10 and is disposed between the resistor 10 and the second region WBR2, and another portion of the boundary portion BD extends in the y-direction of the resistor 10 and in a direction close to the side edge EB.

[0062] 14A to 14D are diagrams illustrating modified examples of the boundary portion. In the embodiment illustrated in FIG. 14A, the boundary portion BD extends parallel to the y direction of the resistor 10. The second region WBR2 is adjacent to the boundary portion BD in the x direction. Therefore, the wire 42 is connected to the inflow portion CI side of the boundary portion BD. The boundary portion BD having such a shape can achieve the same effect as the boundary portion BD according to the embodiment illustrated in FIGS. 12 and 13.

[0063] 14B , the boundary portion BD has an L-shape when viewed from above the wiring 23, and a portion of the boundary portion BD extending in the x-direction of the resistor 10 is connected to the end edge EC of the wiring 23. The other portion of the boundary portion BD extends parallel to the y-direction. The second region WBR2 is surrounded by the L-shaped boundary portion BD. Therefore, the wire 42 is connected closer to the inflow portion CI than the boundary portion BD.

[0064] 14C , the boundary portion BD has a U-shape when viewed from above the wiring 23. The U-shaped boundary portion BD is disposed so that its opening (i.e., the portion where no slit is formed) faces the resistor 10. The second region WBR2 is surrounded by the boundary portion BD.

[0065] 14D , the boundary portion BD also has a U-shape. The boundary portion BD is disposed so that its opening faces the end side EC. In this embodiment, the second region WBR2 is also surrounded by the boundary portion BD.

[0066] 15A and 15B are diagrams showing modified examples of the boundary portion. In Fig. 15A, the resistor 10 before being mounted on the wiring 23 is virtually depicted by a dotted line. As shown in Fig. 15A and 15B, the boundary portion BD may have a straight portion that extends to below the resistor 10 when the resistor 10 is mounted on the wiring 23.

[0067] The straight line portion serving as the boundary portion BD extends in a direction perpendicular to one side (i.e., side edge EB) of the second electrode 13 (i.e., parallel to the edge edge EC), and the boundary portion BD is connected to an end surface of the wiring 23. The second region WBR2 is disposed between the boundary portion BD and the edge edge EC. Therefore, the wire 42 is connected to the inflow portion CI side of the boundary portion BD.

[0068] 16 and 17 are diagrams showing other embodiments of the current detection device. In the above-described embodiment, the current detection device 100 includes the bus bar 20 as the first conductor. However, in one embodiment, the current detection device 100 may include a clip terminal 400 (see FIG. 16 ) or a plurality of bonding wires 500 (see FIG. 17 ) instead of the bus bar 20. The plurality of bonding wires 500 are connected to an inlet portion CI as a starting end portion of the current detection device 100.

[0069] According to the present invention, it is possible to make products smaller and lighter, and reduce the amount of material used. This allows the devices used to be smaller and lighter, contributing to a reduction in energy consumption. This invention can contribute to the achievement of Goal 3 "Good health and well-being," Goal 7 "Affordable and clean energy," and Goal 12 "Responsible consumption and production" of the Sustainable Development Goals (SDGs) led by the United Nations.

[0070] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would be obvious to a person skilled in the art, and the technical concept of the present invention may be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims.

[0071] The present invention can be used in a current detection device.

[0072] REFERENCE SIGNS LIST 10 resistor 11 resistive element 12 first electrode 13 second electrode 20 bus bar (first conductor) 21, 22 bus bar 23 wiring (second conductor) 24, 25 wiring 26 insulating substrate 30 power device 40 bonding wire 41 bonding wire (first detection conductor) 42 bonding wire (second detection conductor) 45 case 51 first voltage detection terminal 52 second voltage detection terminal 100 current detection device 200 power module BD boundary EA opposing side EB side EC end side CI inflow portion CO outflow portion WBR1 first region WBR2 second region WBPa connection position WBPb connection position a width b width c distance Ra region Rb region

Claims

1. A current detection device comprising: a resistor having a laminated structure in which a first electrode, a resistive element, and a second electrode are laminated in the thickness direction; a first conductor connected to the first electrode; a second conductor connected to the second electrode; and first and second detection conductors for detecting voltage, wherein the first detection conductor is connected to a first region on the upper surface of the first electrode or the first conductor, on an opposing side facing the inlet portion of the first conductor; and the second detection conductor is connected to a second region of the second conductor, on the side of the inlet portion and located on the side of the second electrode.

2. The current detection device according to claim 1, wherein the first region is a region extending from the center of the first electrode to the opposing side.

3. The current detection device according to claim 1, wherein the second conductor is a wiring pattern formed on a circuit board, the second electrode and the second conductor are connected by solder, the second conductor has a boundary formed in an area along one side of the second electrode, and the second detection conductor is connected to the side of the boundary.

4. The current detection device according to claim 3, wherein the boundary portion is a through slit, a non-through slit, an insulating film, or a step formed in the second conductor.

5. The current detection device according to claim 3, wherein the boundary portion has a straight portion, and the straight portion extends in a direction perpendicular to one side of the second electrode.

6. The current detection device according to claim 5, wherein the second detection conductor is connected closer to the inflow portion than the boundary portion.

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