Busbar and method for manufacturing a busbar

Abstract

To provide a bus bar capable of suppressing occurrence of partial discharge, and a manufacturing method of the bus bar.SOLUTION: In a bus bar, a P bus bar, an insulation layer and an N bus bar are laminated in this order, and in a predetermined end, an end of one of the P bus bar and the N bus bar is coated with a resin. In the bus bar, the P bus bar or the N bus bar is at least partially exposed in a portion from an end of the other P bus bar or N bus bar to the insulation layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a bus bar and a method for manufacturing the bus bar.

Background Art

[0002] In a hybrid electric vehicle or the like, an electric drive system is mounted in addition to a conventional engine. In this electric drive system, DC power supplied from a battery is converted into AC power by an inverter device, and power is supplied to a motor or the like. [[ID=?]] [[ID=?]]

[0003] [[ID=?]] The inverter device includes a switching module including a switching element such as an IGBT (Insulated Gate Bipolar Transistor), a switching control circuit for controlling the switching element, a smoothing capacitor for smoothing DC power supplied from the battery to the switching element, and further includes a bus bar for electrically connecting the switching module and the smoothing capacitor. In order to connect the P terminal and the N terminal of the switching module and the positive electrode and the negative electrode of the smoothing capacitor, a P bus bar and an N bus bar are provided as bus bars, respectively. [[ID=?]] [[ID=?]]

[0004] [[ID=?]] The inverter device of a hybrid electric vehicle or the like performs high-speed on / off control by a switching element such as an IGBT. However, if the inductance of the circuit board and wiring is large, a surge voltage is generated when the switching element is turned on or off, which may cause malfunction or damage of the switching element. Therefore, prevention of malfunction and damage of the switching element by reducing the surge voltage is required. [[ID=?]] [[ID=?]]

[0005] [[ID=?]] For example, in Patent Document 1, a capacitor serving as a snubber circuit is configured by interposing a high dielectric between a pair of bus bars. By providing this snubber circuit, it is said that the surge voltage applied to the switching element during the switching operation is absorbed, and destruction of the switching element can be suppressed. [[ID=?]] [[ID=?]]

[0006] [[ID=?]] It should be noted that there are some consecutive tags with no content in the original text which seem to be formatting or placeholder remnants. I've left them as they are in the translation for consistency with the original. Also, the tags with "?" in the translation are the ones that originally had consecutive tags with no content between lines 13 - 15 and 17 - 19. If there's more context or specific requirements regarding these, it would help in providing a more accurate translation.Furthermore, Patent Document 2 discloses a manufacturing method for interposing a high dielectric material between a pair of busbars. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2003-319665 [Patent Document 2] Patent No. 4905254 [Overview of the project] [Problems that the invention aims to solve]

[0008] To reduce inductance, shortening the distance between busbars is effective. Also, in order to electrically connect the power supply terminals supplied from the battery via a smoothing capacitor, and the P and N terminals of the switching element to the busbars using metal wiring such as wire bonding, it is necessary to expose the metal parts of the busbars. However, if the distance between busbars is narrowed, electric field concentration is likely to occur at the exposed metal parts at the ends of the busbars, making partial discharge more likely when high voltage is applied. Therefore, the present disclosure aims to provide a busbar having a region where a portion of the metal is partially exposed and wiring can be connected, a short distance between busbars, and the ability to suppress the occurrence of partial discharge, as well as a method for manufacturing a busbar. [Means for solving the problem]

[0009] Specific means for solving the above problems include the following embodiments.

[0010] <1> The P busbar, insulating layer, and N busbar are stacked in this order. A busbar in which, at a predetermined end, one end of either a P busbar or an N busbar is coated with resin, and at least a portion of the P busbar or N busbar from the other end to the insulating layer is exposed. <2> The distance from the end of the resin-coated P-busbar or N-busbar to the end of the resin coating is 0.1 mm or more. <1> The bus bar as described. <3> The thickness of the insulating layer is thinner than the thickness of the P busbar and the N busbar. <1> or <2> The bus bar as described. <4> The insulating layer contains an inorganic filler. <1> ~ <3> A bus bar as described in any one of the items. <5> The insulating layer includes a woven fabric or a nonwoven fabric. <1> ~ <4> A bus bar as described in any one of the items. <6> The woven or nonwoven fabric contains glass fibers, <5> The bus bar as described. <7> The process involves preparing two metal plates to be a P busbar and an N busbar, staggering the positions of the ends of the two metal plates at a predetermined end, and arranging them opposite each other with a gap between them, A step of injecting resin material into the gap between the opposing metal plates such that at a predetermined end, one end of the metal plate is covered with the resin, and the other end of the metal plate is not covered with the resin, including, <1> ~ <6> A method for manufacturing a bus bar as described in any one of the items. <8> The process further includes curing the injected resin material. <7> A method for manufacturing a bus bar as described above. <9> A process of preparing a resin plate containing resin material, and two metal plates that will become a P busbar and an N busbar, The process of arranging metal plates on both sides of the resin plate such that the edge of the resin plate is located inside the edge of one metal plate and outside the edge of the other metal plate, A step of applying pressure and heating from the outside of the metal plate to melt both surfaces of the resin plate, including, <1> ~ <6> A method for manufacturing a bus bar as described in any one of the items. <10> The process further includes heating the resin plate, whose two surfaces have melted, to cure the resin material. <9> A method for manufacturing a bus bar as described above. [Effects of the Invention]

[0011] The present disclosure can provide a bus bar capable of suppressing the occurrence of partial discharge and a method for manufacturing the bus bar.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic plan view of a part including a predetermined end portion in an example of a bus bar. [Figure 2] It is a schematic cross-sectional view showing the A-A cross-section of FIG. 1. [Figure 3] It is a schematic cross-sectional view for explaining a method for manufacturing a bus bar by transfer molding. [Figure 4] It is a schematic cross-sectional view for explaining a method for manufacturing a bus bar by compression molding.

Modes for Carrying Out the Invention

[0013] Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, its components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention. In the present disclosure, the term "step" includes, in addition to a step independent of other steps, the step even if it cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the numerical range indicated by "~" in the present disclosure, the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in each test.

[0014] In the present disclosure, each component in the resin material may contain a plurality of corresponding substances. In the present disclosure, the term "layer" includes cases where the layer is formed not only over the entire area observed but also only in a part of the area when observing the area where the layer exists. In the present disclosure, the term "lamination" indicates stacking layers, and two or more layers may be joined, or two or more layers may be detachable.

[0015] Specific examples of the bus bar of the present disclosure will be described while referring to the drawings, but the embodiments are not limited thereto. Also, the sizes of the members in each figure are conceptual, and the relative relationships of the sizes between the members are not limited thereto. In each figure, the same or corresponding parts are given the same reference numerals, and redundant descriptions are omitted.

[0016] <Bus bar> In the bus bar of the present disclosure, a P bus bar, an insulating layer, and an N bus bar are laminated in this order. At a predetermined end, one end of the P bus bar and the N bus bar is resin-coated, and at least a part of the surface facing the insulating layer from the end of the other P bus bar or N bus bar is not resin-coated. The region where the other P bus bar or N bus bar is not resin-coated is a region where the bus bar is exposed, and thus it is a region (also referred to as a "wiring connection region") where ultrasonic bonding such as wire bonding or ribbon bonding, metal welding such as spot welding, laser welding, or TIG welding can be performed between a power supply element such as a smoothing capacitor and the bus bar and a switching element such as an IGBT and the bus bar.

[0017] Note that in the present disclosure, "exposed" means that no insulating layer is provided, and it includes the exposed state even when an oxide film exists on the surface of the bus bar due to oxidation of the surface of the metal constituting the bus bar.

[0018] Figure 1 is a schematic plan view of a portion of an example busbar, including a predetermined end. Figure 2 is a schematic cross-sectional view showing section AA of Figure 1. As shown in the cross-sectional view of Figure 2, the P busbar 10 and the N busbar 12 are provided opposite each other, and an insulating layer 20 is provided in the gap between the P busbar 10 and the N busbar 12. At the predetermined end where wiring connections such as wire bonding and ribbon bonding are performed, as shown in Figure 1, in the plan view from the P busbar 10 side, the P busbar 10 and the insulating layer 20 are partially open, and the N busbar 12 is exposed. This exposed area of ​​the N busbar 12 becomes the wiring connection area of ​​the N busbar 12. By providing this wiring connection area, the P busbar 10 and the N busbar 12 can be wired together from the same side (in the case of Figure 1, from the upper surface of the P busbar 10 side).

[0019] Furthermore, since the edges of the P busbar 10 are covered with the insulating layer 20 at the opening described above, the lower insulating layer 20 is visible as a border in the plan view of Figure 1 as seen from the P busbar 10 side. Here, it became clear that partial discharge from the busbar occurs mostly from the ends of the busbar (especially the corners where the side surface and the opposing surface intersect). This is thought to be because the electric field is concentrated at the ends of the busbar, especially at the corners. Therefore, by covering the ends of the busbar, including the corners, with the insulating layer 20, the occurrence of partial discharge is effectively suppressed. Since the occurrence of partial discharge is suppressed, it is possible to shorten the gap distance between the P busbar 10 and the N busbar 12, thereby making the busbar more compact and reducing its inductance.

[0020] The distance D from the end X of the P busbar 10 to the end Y of the resin coating is preferably 0.1 mm or more. Furthermore, from the viewpoint of minimizing the mounting space in the automobile, the distance D is preferably 1.5 mm or less, and more preferably 1.0 mm or less.

[0021] The thickness H of the insulating layer 20 is preferably thinner than the thickness of the P busbar 10 and N busbar 12. By reducing the thickness of the insulating layer 20, it is possible to ensure high current flow to the P busbar 10 and N busbar 12 while reducing the overall thickness and making the device more compact. Furthermore, the distance S and T of the wiring connection area where the N busbar is exposed are not particularly limited, as they can be designed by the number of wire bonds, ribbon bonds, etc.

[0022] Figures 1 and 2 show a configuration in which the end of the P busbar 10 is covered with an insulating layer 20 while having an opening, and the N busbar 12 is exposed through that opening. However, the P busbar 10 and the N busbar 12 may be swapped.

[0023] Furthermore, although Figures 1 and 2 illustrate predetermined ends, other ends may have a similar configuration. Furthermore, at other ends, the P busbar 10 and N busbar 12 may be swapped. In other words, at a given end, the end of the P busbar 10 has an opening, so both the P busbar 10 and N busbar 12 are wired and connected from the P busbar 10 side (the top side in Figure 1), while at other ends, the end of the N busbar 12 has an opening, so both the P busbar 10 and N busbar 12 are wired and connected from the N busbar 10 side (the bottom side in Figure 1).

[0024] The P busbar 10 and N busbar 12 may be metal plates. Examples of metal plate materials include copper, nickel-plated copper, and aluminum, but are not particularly limited. The metal plate may be flat and may have partially bent portions. The edges of the metal plate at predetermined ends may have a taper in the thickness direction.

[0025] The insulating layer 20 can be any insulating material, and it is preferable that it contains a resin. The resin may be either a thermoplastic resin or a thermosetting resin. From the viewpoint of improving heat resistance, a thermosetting resin is preferable. Examples of resins include polyphenylene sulfide (PPS) resin, polybutylene terephthalate (PBT) resin, polyimide (PI) resin, polyamide (PA) resin, epoxy resin, phenolic resin, etc. It is preferable to select a resin whose coefficient of thermal expansion is as close as possible to the coefficient of thermal expansion of the P busbar 10 and N busbar 12.

[0026] The insulating layer 20 may contain inorganic fillers, woven fabrics, or nonwoven fabrics. The strength of the insulating layer 20 is increased by the inclusion of inorganic fillers, woven fabrics, or nonwoven fabrics. The woven fabrics and nonwoven fabrics may be composed of inorganic or organic materials. When the insulating layer 20 contains inorganic fillers, inorganic woven fabrics, or inorganic nonwoven fabrics, it becomes possible to bring the thermal expansion coefficient of the insulating layer 20 closer to that of the P busbars 10 and N busbars 12.

[0027] The inorganic filler can be any type, including silica filler and alumina filler. The woven or nonwoven fabric can be a nonwoven fabric containing glass fiber, nylon fiber, aramid fiber, polyester fiber, polypropylene fiber, etc. These can also be used as prepregs impregnated with various resins.

[0028] The end of the insulating layer 20 at a predetermined end may have a taper in the thickness direction.

[0029] <How to manufacture a bus bar> The method for manufacturing the busbar may be any method that makes it possible to form the above configuration, and examples include compression molding and transfer molding. In transfer molding, resin is injected between two metal plates. In compression molding, a resin plate is prepared in advance, and the resin plate is placed between the two metal plates that make up the P busbar and N busbar, and then heated and pressed together.

[0030] (Transfer molding) The method for manufacturing busbars by transfer molding is: The process involves preparing two metal plates to be a P busbar and an N busbar, staggering the positions of the ends of the two metal plates at a predetermined end, and arranging them opposite each other with a gap between them, A step of injecting resin material into the gap between the opposing metal plates such that at a predetermined end, one end of the metal plate is covered with the resin, and the other end of the metal plate is not covered with the resin, Includes.

[0031] As shown in Figure 3, a pair of metal plates 10 and 12 are placed facing each other inside the mold 30 at a predetermined distance apart. At this time, the edges X of metal plate 10 are positioned inside the edges Z of metal plate 12 at a predetermined end, and a gap D is provided between the edge X of metal plate 10 and the mold 30. Furthermore, a recess corresponding to the thickness of metal plate 12 is provided in the mold 30, and the edge Z of metal plate 12 is placed in this recess, thereby covering the metal plate 12 from edge Z to a predetermined distance S with the mold 30.

[0032] Next, resin material is injected between the metal plates 10 and 12 using a transfer method. At this time, the resin is injected so that it reaches the gap D, so that the edges of metal plate 10 are covered with resin. On the other hand, since the edges Z of metal plate 12 are covered by the mold 30 up to the gap S, the portion at the gap S is not covered with resin and remains exposed.

[0033] The resin material contains resin and may also contain inorganic fillers. If the injected resin material contains thermosetting resin, it is further heated to cure it.

[0034] As shown in Figure 3(B), the mold 30 may be inclined from the gap D to the spacing S so that the formed insulating layer 20 has a taper in the thickness direction. This may make it easier to remove the material from the mold.

[0035] (Compression molding) The method for manufacturing busbars by compression molding is: A process of preparing a resin plate containing resin material, and two metal plates that will become a P busbar and an N busbar, The process of arranging metal plates on both sides of the resin plate such that the edge of the resin plate is located inside the edge of one metal plate and outside the edge of the other metal plate, A step of applying pressure and heating from the outside of the metal plate to melt both surfaces of the resin plate, Includes.

[0036] First, a resin sheet 20 containing resin material is prepared in advance. The resin sheet 20 may be molded from resin alone, or it may also contain inorganic fillers. Alternatively, it may be a prepreg in which resin is impregnated into an inorganic woven or nonwoven fabric. The prepreg may also contain inorganic fillers.

[0037] Next, as shown in Figure 4(A), metal plates 10 and 12, which will become the P busbar and N busbar, are placed on both sides of the resin plate 20 such that the end Y of the resin plate 20 is located inside the end Z of the metal plate 12 and outside the end of the metal plate 10. At this time, a gap D is provided between the end X of the metal plate 10 and the end Y of the resin plate 20, and a gap S is provided between the end Z of the metal plate 12 and the end Y of the resin plate 20.

[0038] Next, as shown in Figure 4(B), pressing substrates are placed on the outer surfaces of the metal plates 10 and 12, respectively, and the metal plates are heated and pressurized appropriately from the outside. At this time, as shown in Figure 4(C), the molten resin seeps into the space between the resin plate 20 and the pressing substrate around the edge of the metal plate 10, so the edge of the metal plate 10 is covered with resin. On the other hand, the area with a gap S at the edge Z of the metal plate 12 is not in contact with the resin plate 20, and therefore is not covered with resin and remains exposed.

[0039] Furthermore, as with compression molding, if the resin contained in the resin plate 20 is a thermosetting resin, it is further heated to cure it.

[0040] <Applicable> The busbar can be applied to an inverter device. The inverter device comprises a switching module including switching elements, a switching control circuit for controlling the switching elements, a smoothing capacitor for smoothing the DC power supplied to the switching elements, and the busbar of this disclosure for electrically connecting the switching module and the smoothing capacitor. As the switching elements, IGBTs (Insulated Gate Bipolar Transistors) and the like can be used. [Examples]

[0041] The present invention will be described in detail below with reference to the following examples, but the present invention is not limited to these examples.

[0042] [Example 1] A resin laminate was prepared by placing epoxy resin sheets on both sides of an epoxy resin-containing prepreg. Then, 1 mm thick copper plates were placed on both sides of the resin laminate. At this time, the copper plates were offset so that the spacing D was 0.5 mm, and the spacings S and T were 10 mm each, thereby obtaining a copper-coated laminate. A substrate was placed on both outer sides of the copper-coated laminate, and it was heated at 180°C for 3 minutes while applying pressure from the outside of the substrate to obtain a busbar. The thickness of the insulating layer in the obtained busbar was 0.2 mm, the epoxy resin had spread to the area of ​​spacing D, and the tip of one of the copper plates was covered with epoxy resin.

[0043] To simulate the application of the obtained busbars to an inverter device, the insulation characteristics of the P-busbar and N-busbar were evaluated when a high voltage equivalent to a surge voltage was applied. Specifically, an AC voltage (50Hz) was applied to the exposed metal parts of the P-busbar and N-busbar, and the discharge charge was measured. The results showed that the discharge charge was less than 5pC (picocoulombs) up to an applied voltage of 2500V, confirming that no partial discharge occurred. The electric field analysis of the tip of the copper plate covered with epoxy resin showed that the maximum electric field strength was 10.3MV / m.

[0044] [Comparative Example 1] A busbar was obtained in the same manner as in Example 1, except that no external pressure was applied to the copper-plated laminate. In the obtained busbar, the epoxy resin did not flow into the portion of the gap D, and the tip portion of the copper plate was not covered with epoxy resin. When the P busbar and N busbar were subjected to a high voltage equivalent to the surge voltage in the same manner as in Example 1, the insulation characteristics were evaluated, and a partial discharge occurred at an applied voltage of 1600V. Electric field analysis of the tip portion of the copper plate not covered with epoxy resin showed a maximum electric field strength of 13.5 MV / m. It is presumed that the partial discharge occurred because the electric field was more concentrated at the tip portion of the copper plate than in Example 1. [Explanation of symbols]

[0045] 10 P busbar (metal plate), 12 N busbar (metal plate), 20 insulating layer (resin), 30 mold

Claims

1. The P busbar, insulating layer, and N busbar are stacked in this order. A method for manufacturing busbars, wherein at a predetermined end, one end of a P-busbar and an N-busbar is covered with resin, and at least a portion of the P-busbar or N-busbar from the other end to the insulating layer is exposed. The process involves preparing two metal plates that will become the P busbar and the N busbar, staggering the positions of the ends of the two metal plates at predetermined ends, and arranging them facing each other inside the mold with a gap between them, A step of injecting resin material into the gap between the opposing metal plates by a transfer method such that at a predetermined end, the end of one metal plate is covered with the resin, and the end of the other metal plate is not covered with the resin. Includes, A method for manufacturing a busbar, wherein the mold is provided with a recess corresponding to the thickness of the other metal plate, and the end of the other metal plate is placed in the recess.

2. A method for manufacturing a bus bar according to claim 1, further comprising the step of curing the injected resin material.

3. The P busbar, insulating layer, and N busbar are stacked in this order. A method for manufacturing busbars, wherein at a predetermined end, one end of a P-busbar and an N-busbar is coated with resin, and at least a portion of the P-busbar or N-busbar from the other end to the insulating layer is exposed. A step of preparing a resin plate containing a resin material, and two metal plates that will become the P busbar and the N busbar, The process of arranging metal plates on both sides of the resin plate such that the edge of the resin plate is located inside the edge of one metal plate and outside the edge of the other metal plate, A method for manufacturing a busbar, comprising the step of applying pressure to the outside of the metal plate and heating it to melt both surfaces of the resin plate.

4. A method for manufacturing a busbar according to claim 3, further comprising the step of further heating the resin plate whose two surfaces have melted to harden the resin material.

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