A direct current filter capacitor with an aluminum row elastic welding needle welding structure

Abstract

The application provides a direct current filter capacitor with an elastic welding needle of aluminum row, and relates to the technical field of capacitor manufacturing. The capacitor comprises an insulating shell, a capacitor core accommodated in the shell, an internal aluminum conductive row, and a copper conductive row with an extension terminal outside the shell. The aluminum conductive row is electrically connected with a gold spraying surface of the core, and an elastic welding unit is integrated on the aluminum conductive row. The unit comprises a hollow groove, an elastic welding needle suspended in the groove, and a thin shaft in the middle. The welding needle is press-fit welded on the gold spraying surface through a plurality of welding points. The aluminum row connecting end is butt welded with the copper conductive row. The welding joint is located in the shell and is embedded and sealed by an epoxy resin solidification body. The aluminum conductive row and the copper conductive row are used inside and outside respectively, and the copper-aluminum joint is embedded and sealed, so that the hidden troubles of creep, heating and water vapor erosion under thermal cycle are eliminated. The elastic welding unit provides a mechanical deformation margin for press-fit resistance welding, ensures the welding reliability, and eliminates the soldering cost.

Description

Technical Field

[0001] This invention relates to the field of capacitor manufacturing technology, and more specifically, to a DC filter capacitor with an aluminum busbar elastic welding pin structure. Background Technology

[0002] DC-supported filter capacitors are core components in new energy vehicle controllers, wind power inverter systems, and large-capacity energy storage devices, primarily used for DC-supported filtering of busbar capacitors. In these application areas, especially in large-scale mass production fields such as vehicle controllers, not only are there extremely high reliability requirements for the electrical and mechanical performance of capacitors, but also extremely stringent requirements for controlling their manufacturing costs.

[0003] In traditional DC-supported film capacitor manufacturing processes, the internal conductive network and external output leads are generally designed as a single pure copper busbar. To electrically connect the two ends of the gold-plated metal surfaces of the multiple capacitor cores, the industry typically uses traditional soldering to achieve the mechanical and electrical connection between the copper busbar and the gold-plated surfaces. However, with the continued high prices of global raw metals and increasing pressure to reduce costs, this traditional approach has revealed the following significant technical challenges: First, the manufacturing cost is high. Traditional pure copper busbar materials are expensive, and the soldering process requires a large amount of solder wire. These two material costs account for a very high proportion of the overall cost of capacitors, which severely limits the room for cost reduction when capacitors face fierce market competition.

[0004] Secondly, replacing aluminum busbars faces technological and quality bottlenecks. Although aluminum busbars are much cheaper than copper busbars, making them an excellent low-cost alternative, their non-tin-adhesive surface leads to poor traditional soldering results, sometimes even making them impossible. To address the connection issue between the aluminum busbar and the gold-plated surface of the capacitor core, some manufacturers have proposed laser welding. However, laser welding requires extremely high surface roughness of the gold-plated layer on the capacitor core end face, typically necessitating a secondary mechanical polishing process. To solve the tin adhesion problem, nickel plating has been used, but while this solves the soldering issue, the cost of nickel plating is significant. Furthermore, laser welding demands extremely high precision in the fit between the aluminum busbar and the gold-plated surface. In the three-dimensional assembly space, minute gaps can easily lead to incomplete soldering or overheating, and the welding effect is not visible, resulting in a relatively high overall risk of poor welding quality. More seriously, the instantaneous high heat generated by laser welding can easily burn the thin-film dielectric at the capacitor core end, damaging the capacitor's lifespan.

[0005] Third, there is the risk of environmental failure in the external copper-aluminum heterogeneous transition contact. To reduce costs, replacing the entire internal conductive network and external leads with aluminum busbars would introduce serious engineering defects at external connection points (such as the junctions between capacitors and external IGBT modules). Since the external interfaces are exposed to air for extended periods without epoxy resin or other curing and sealing protection, the copper (external device interface) and aluminum (capacitor leads) are in direct contact. Due to the significant difference in the linear expansion coefficients of aluminum and copper, under the influence of thermal expansion and contraction and alternating temperature loads, creep will occur at the bolted joints over long-term operation, leading to loosening of contacts, increased contact resistance, and severe overheating, compromising the reliability of the external connection. Therefore, copper busbar connections must be retained at the junctions between capacitors and external power devices to ensure the reliability of the external connection. However, an effective method for efficiently, reliably, and with long-term corrosion protection in the structure to achieve a transition connection between the internal aluminum busbar and the external copper busbar remains lacking in the industry.

[0006] Fourth, the equivalent series inductance (ESL) and safety challenges under high-frequency, high-current environments. In high-frequency switching environments (such as high-frequency switching of IGBTs in inverters), the rapid current switching places extremely high demands on the loop inductance of capacitors. If the spatial arrangement of the positive and negative conductive paths is not tight enough, the loop area is too large, or the copper-aluminum transition bypasses the low-inductance multilayer busbar area, a very large equivalent series inductance will be generated. High inductance will induce huge transient voltage spikes during high-frequency switching, which can easily break down the thin-film dielectric inside the capacitor and may also directly damage expensive external power semiconductor devices.

[0007] Therefore, traditional DC-supported capacitors face multiple technical constraints, such as high material costs, difficulty in implementing high-quality welding of low-cost aluminum busbars, easy creep heating due to dissimilar copper and aluminum external connections, and difficulty in controlling high-frequency inductors. Summary of the Invention

[0008] The technical problem to be solved by the present invention is how to ensure the high reliability of electrode solder joints and copper-aluminum heterogeneous transition connection while significantly reducing the material and welding process cost of DC support filter capacitor, and effectively reduce its equivalent circuit inductance. In order to overcome the above-mentioned defects of the prior art, the present invention provides a DC filter capacitor with an aluminum busbar elastic welding pin welding structure.

[0009] This invention provides a DC filter capacitor with an aluminum busbar elastic welding pin structure, comprising an insulating shell and at least one capacitor core housed within the insulating shell, the capacitor core having a gold-plated surface; further comprising: A copper busbar having copper busbar lead-out terminals extending to the outside of the insulating housing and copper busbar connection terminals located inside the insulating housing; An aluminum conductive busbar is located inside the insulating shell and electrically connected to the gold-plated surface. An elastic welding unit is provided on the area corresponding to the gold-plated surface of the aluminum conductive busbar. The elastic welding unit includes a hollow groove opened on the aluminum conductive busbar and an elastic welding pin suspended inside the hollow groove. The side of the elastic welding pin forms a thin shaft with a narrowed lateral width. The elastic welding pin is connected to the aluminum conductive busbar and suspended in the hollow groove. The elastic welding pin has multiple welding points, which are pressed and welded to the gold-plated surface through multiple welding points. The aluminum conductive busbar extends to have an aluminum busbar connecting end, which is attached to and welded to the copper conductive busbar. The welded joint of the two is located inside the insulating shell and is completely embedded and sealed by an epoxy resin solidified body filled inside the insulating shell.

[0010] Compared with existing technologies, the DC filter capacitor with an aluminum busbar elastic welding pin welding structure disclosed in this application has the following advantages: By setting the external connection end as a copper conductive busbar and the internal connection end as an aluminum conductive busbar, the cost of non-ferrous metal materials is significantly reduced while ensuring a highly reliable electrical connection with the external IGBT module; the copper-aluminum welding joint is placed inside the insulating shell and integrally embedded and sealed with epoxy resin solid, avoiding the creep, heating, and oxidation and water vapor corrosion risks caused by the different linear expansion coefficients of copper and aluminum under external thermal cycling; at the same time, the elastic welding unit integrated on the aluminum conductive busbar, using hollow grooves, suspended elastic welding pins and a central thin shaft, provides mechanical deformation margin and fit for pressure resistance welding, increases the number of automated welding pressure points, ensures welding reliability, saves the cost of expensive solder wire and gold-plated surface grinding, and the resistance welding energy is small, with no risk of gold-plated surface burns, achieving a deep integration of high reliability and stringent cost reduction.

[0011] In one possible implementation, the elastic welding needle includes an elastic frame-shaped outline, which is formed by a left longitudinal segment and a right longitudinal segment arranged in a coplanar manner, an upper transverse arch that connects the upper ends of the left longitudinal segment and the right longitudinal segment respectively, and a lower transverse arch that connects the lower ends of the left longitudinal segment and the right longitudinal segment; wherein, the upper end of the upper transverse arch is connected to an aluminum conductive busbar, and the lower end of the lower transverse arch is connected to an aluminum conductive busbar, so that the left longitudinal segment and the right longitudinal segment are suspended in the hollow groove and form a lateral deformation gap with the aluminum conductive busbar.

[0012] Compared with existing technologies, the frame-like outer contour formed by the coplanar parallel left and right longitudinal sections and the transverse arch, combined with the lateral deformation gap, can flexibly absorb and release the thermal expansion and mechanical stress during resistance welding and operation, effectively avoiding stress concentration damage to the capacitor core.

[0013] In one possible implementation, the thin shafts are two in number and are integrally formed in the middle of the left longitudinal segment and the middle of the right longitudinal segment, respectively. The thin shaft in the middle of the left longitudinal segment has a lateral width narrower than the upper and lower halves of the left longitudinal segment, so that the left longitudinal segment can form a flexible structure that can be elastically deformed. The thin shaft in the middle of the right longitudinal segment has a lateral width narrower than the upper and lower halves of the right longitudinal segment, so that the right longitudinal segment can form a flexible structure that can be elastically deformed. The outer lateral sides of both thin shafts form lateral deformation gaps with the aluminum conductive busbar through perforated grooves.

[0014] Compared with existing technologies, the use of symmetrical thin-axis connections with narrower lateral width provides elastic downward sliding displacement for the pressure electrode in automated resistance welding, further improving the uniformity and reliability of the contact surface during multi-point resistance welding.

[0015] In one possible implementation, the elastic frame-shaped outline has two solder points symmetrically distributed above and below each corresponding thin shaft; wherein, the left longitudinal segment has one solder point above and below the connected thin shaft, and the right longitudinal segment has one solder point above and below the connected thin shaft, so that the four solder points form a two-dimensional matrix distribution of pressure welding structure on the gold-plated surface.

[0016] Compared with existing technologies, the four solder points are distributed in a two-dimensional matrix on the upper and lower parts of the thin shaft, ensuring that each capacitor core has a multi-point divergent current path on the gold-plated surface, achieving uniform distribution of current carrying capacity and voltage equalization bonding.

[0017] In one possible implementation, the copper busbar includes a positive copper busbar and a negative copper busbar arranged in a stacked manner. The positive and negative copper busbars are each integrally formed by stamping and bending from a single piece of copper sheet. The positive copper busbar has a positive copper busbar lead-out terminal extending to the outside of the insulating shell, and a plurality of positive copper busbar connection terminals located inside the insulating shell and arranged at lateral intervals. The negative copper busbar has a negative copper busbar lead-out terminal extending to the outside of the insulating shell, and a plurality of negative copper busbar connection terminals located inside the insulating shell and arranged at lateral intervals. The plurality of positive copper busbar connection terminals and the plurality of negative copper busbar connection terminals are arranged side by side in a one-to-one correspondence. The aluminum conductive busbar includes a positive aluminum busbar electrically connected to the gold-plated surface on one side of the capacitor core, and a negative aluminum busbar electrically connected to the gold-plated surface on the other side of the capacitor core; the positive aluminum busbar extends with a positive aluminum busbar connection end, and the negative aluminum busbar extends with a negative aluminum busbar connection end; the positive aluminum busbar connection end is attached to and welded to the positive copper busbar, and the negative aluminum busbar connection end is attached to and welded to the negative copper busbar.

[0018] Compared with existing technologies, the positive and negative copper and aluminum busbars are arranged in a staggered manner in a one-to-one correspondence along the lateral direction, realizing the modular application of flexible welding units in a bipolar symmetrical structure, which greatly simplifies the internal assembly and welding process of multi-core large-capacity filter capacitors.

[0019] In one possible implementation, an insulating isolation component for achieving potential isolation between the two electrodes is also included. The insulating isolation component includes a second insulating plate sandwiched between the positive copper busbar and the negative copper busbar, and a first insulating plate covering the outside of the positive copper busbar, for stacking and fixing the positive copper busbar and the negative copper busbar into a stacked busbar structure.

[0020] Compared with existing technologies, the first and second insulating plates provide compact stacking constraints for the positive and negative copper busbars, achieving highly reliable potential isolation between the electrodes while significantly reducing the distance between the positive and negative plates and lowering the parasitic inductance of the busbar circuit.

[0021] In one possible implementation, both the first insulating plate and the second insulating plate are integrally formed three-dimensional multi-directional bent plate structures, so as to be in contact with the bent surfaces of the positive electrode copper busbar and the negative electrode copper busbar, respectively.

[0022] Compared with existing technologies, the insulation board adopts a one-piece molded three-dimensional multi-directional bending structure, which can fit the complex bending surface of the busbar, greatly improving the inter-electrode creepage distance while optimizing the compactness of the spatial structure.

[0023] In one possible implementation, a fixing plate is further provided on the side of the insulating shell and fixedly connected to the insulating shell. The fixing plate has a buckle on the side facing the negative copper busbar, and one end of the negative copper busbar is locked onto the fixing plate by the buckle.

[0024] Compared with existing technologies, by setting a buckle on one side of the fixed plate to directly fasten and lock the negative copper busbar, the entire stacked busbar assembly can be fastened without bolts. This simplifies the mechanical structure, eliminates the risk of local high-voltage discharge breakdown caused by metal fastening bolts, and significantly improves the vibration and impact resistance of the whole machine.

[0025] In one possible implementation, the upper edge of the insulating shell is fitted with a terminal positioning seat, and multiple isolation baffles are integrally extended upward above the terminal positioning seat. Each isolation baffle is correspondingly inserted between adjacent positive copper busbar connection terminals and negative copper busbar connection terminals to achieve creepage isolation.

[0026] Compared with existing technologies, the multiple isolation baffles above the terminal positioning base provide physical rigid isolation between adjacent and staggered positive and negative copper busbar connection terminals, significantly improving the spatial electrical clearance and anti-arc short-circuit capability at the top of the capacitor.

[0027] In one possible implementation, the gold-plated surface of the capacitor core is a zinc-tin-copper alloy gold-plated layer without solder dielectric, and multiple solder joints are press-welded onto the zinc-tin-copper alloy gold-plated layer.

[0028] Compared with existing technologies, the use of a zinc-tin-copper alloy gold-plated layer without solder medium, combined with direct resistance welding with welding pins, eliminates the cost of solder and reduces the risk of burns due to the low heat energy of resistance welding. This allows for a thinner gold-plated layer, further reducing material costs. Attached Figure Description

[0029] Figure 1 This is a top view of the overall structure of a DC filter capacitor with an aluminum busbar elastic welding pin welding structure according to the present invention; Figure 2 This is a three-dimensional view of a DC filter capacitor with an aluminum busbar elastic welding pin welding structure according to the present invention. Figure 3 This is a three-dimensional structural diagram of the elastic welding unit on the positive and negative aluminum busbars in a DC filter capacitor with an aluminum busbar elastic welding needle welding structure according to the present invention. Figure 4 This is a partial three-dimensional structural diagram of a DC filter capacitor with an aluminum busbar elastic welding pin welding structure according to the present invention; Figure 5 This is a schematic diagram of a partial explosion structure in a DC filter capacitor with an aluminum busbar elastic welding pin welding structure according to the present invention; Figure 6 This is a partial structural schematic diagram from another perspective of a DC filter capacitor with an aluminum busbar elastic welding pin welding structure according to the present invention.

[0030] Explanation of reference numerals in the attached figures: 1-Insulating outer casing; 2-Capacitor core; 21-Gold plating surface; 3-Copper busbar; 31-Copper busbar lead-out terminal; 311-Positive copper busbar lead-out terminal; 312-Negative copper busbar lead-out terminal; 32-Copper busbar connection terminal; 321-Positive copper busbar connection terminal; 322-Negative copper busbar connection terminal; 33-Positive copper busbar; 34-Negative copper busbar; 4-Aluminum busbar; 41-Aluminum busbar connection terminal; 411-Positive aluminum busbar connection terminal; 412-Negative aluminum busbar connection terminal; 42-Positive aluminum busbar; 43-Negative aluminum busbar; 5-Elastic welding unit; 51-Hollowed groove; 52-Elastic welding pin; 521-Left longitudinal section; 522-Right longitudinal section; 523-Upper transverse arch; 524-Lower transverse arch; 53-Thin shaft; 61 - First insulating board; 62 - Second insulating board; 7-Fixing plate; 71-Snap fastener; 8-Terminal positioning base; 81-Isolation baffle; 9- Solder joint. Detailed Implementation

[0031] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0032] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0033] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] See Figures 1-6 As shown in the figure, this application discloses a DC filter capacitor with an aluminum busbar elastic welding pin structure, including an insulating shell 1 and at least one capacitor core 2 housed within the insulating shell 1, the capacitor core 2 having a gold-plated surface 21; and further including: The copper busbar 3 has a copper busbar lead-out terminal 31 extending to the outside of the insulating housing 1 and a copper busbar connection terminal 32 located inside the insulating housing 1. An aluminum conductive busbar 4 is located inside the insulating shell 1 and is electrically connected to the gold-plated surface 21. An elastic welding unit 5 is provided on the aluminum conductive busbar 4 in the area corresponding to the gold-plated surface 21. The elastic welding unit 5 includes a hollow groove 51 opened on the aluminum conductive busbar 4 and an elastic welding needle 52 suspended inside the hollow groove 51. A thin shaft 53 with a narrowed lateral width is formed on the side of the elastic welding needle 52. The elastic welding needle 52 is connected to the aluminum conductive busbar 4 and suspended in the hollow groove 51. Multiple welding points 9 are provided on the elastic welding needle 52, and the needle is pressed and welded to the gold-plated surface 21 through the multiple welding points 9.

[0035] Among them, the aluminum conductive bus 4 extends with an aluminum bus connection end 41, which is attached to and welded to the copper conductive bus 3. The welded joint of the two is located inside the insulating shell 1 and is completely embedded and sealed by the epoxy resin solid body filled in the insulating shell 1.

[0036] By setting the external connection end as a copper conductive busbar 3 and the internal connection end as an aluminum conductive busbar 4, the cost of non-ferrous metal materials is significantly reduced while ensuring a highly reliable electrical connection with the external IGBT module. The copper-aluminum welded joint is placed inside the insulating shell 1 and sealed by an epoxy resin solid, avoiding the creep, heating and oxidation water vapor corrosion risks caused by the different linear expansion coefficients of copper and aluminum under external thermal cycling.

[0037] Meanwhile, the elastic welding unit 5 integrated on the aluminum conductive busbar 4, with its hollow groove 51, suspended elastic welding pins 52 and central thin shaft 53, provides mechanical deformation margin and fit for pressure resistance welding, increases automated welding pressure points, ensures welding reliability, saves the cost of expensive nickel plating and solder wire, and the resistance welding energy is small, and the gold-plated surface 21 does not require mechanical polishing, achieving a deep integration of high reliability and stringent cost reduction.

[0038] like Figure 3 As shown, the elastic welding unit 5 is integrally formed by stamping the main body plate of the aluminum conductive bus 4 directly through a die. It includes: a hollow groove 51 opened on the aluminum conductive bus 4, an elastic welding pin 52 suspended inside the hollow groove 51, and a thin shaft 53 located at the left and right symmetrical center of the elastic welding pin 52.

[0039] The elastic welding needle 52 includes an adaptively deformable elastic frame-shaped outline. This elastic frame-shaped outline is formed by a left longitudinal segment 521 and a right longitudinal segment 522 that are parallel to each other and coplanar in space, an upper transverse arch 523 that connects the upper ends of the left longitudinal segment 521 and the right longitudinal segment 522, and a lower transverse arch 524 that connects the lower ends of the left longitudinal segment 521 and the right longitudinal segment 522.

[0040] The upper end of the arc apex of the upper transverse arch 523 is integrally connected to the main body plate of the aluminum conductive busbar 4, and the lower end of the arc trough of the lower transverse arch 524 is integrally connected to the main body plate of the aluminum conductive busbar 4. Through the above-mentioned double-end fixed and double-side suspended structural design, the longitudinal outer walls of the left longitudinal section 521 and the right longitudinal section 522 maintain a uniform mechanical gap with the inner wall of the groove edge of the hollow groove 51, thereby enabling the longitudinal sections on both sides to undergo elastic flexural deformation outward or inward.

[0041] like Figure 3As shown, there are two thin shafts 53, which are integrally formed in the middle of the left longitudinal segment 521 and the right longitudinal segment 522, respectively. The thin shaft 53 in the middle of the left longitudinal segment 521 has a lateral width narrower than the upper and lower halves of the left longitudinal segment 521, so that the left longitudinal segment 521 can form a flexible structure that can be elastically deformed; the thin shaft 53 in the middle of the right longitudinal segment 522 has a lateral width narrower than the upper and lower halves of the right longitudinal segment 522, so that the right longitudinal segment 522 can form a flexible structure that can be elastically deformed.

[0042] It should be noted that the thin shaft 53 is not an independent component embedded or spanning the frame of the elastic welding pin 52, but rather a variable cross-section shaft segment integrally stamped with the left longitudinal section 521 and the right longitudinal section 522, and with a locally narrowed lateral width. The thin shaft 53 acts as a flexible hinge, enabling the left longitudinal section 521 and the right longitudinal section 522 to undergo elastic micro-oscillation and deformation under pressure.

[0043] Specifically, the lateral width of the thin shaft 53 is limited to be narrower than the main width of the left longitudinal segment 521 and the right longitudinal segment 522, thus making the thin shaft 53 the weakest stiffness area, i.e., the flexible hinge, on the entire elastic frame-like outline. When the electrode indenter of the automated resistance welding equipment applies downward pressure perpendicular to the gold-plated surface 21 to the elastic welding needle 52, the two narrow-width thin shafts 53 can undergo slight torsional and bending deformations. This gives the elastic welding needle 52 the freedom to make small-angle adaptive swings in three-dimensional space, which can compensate for the flatness error and fluctuations during the assembly of the capacitor core 2, ensuring multi-point uniform contact during welding.

[0044] The outer sides of the two thin shafts 53 are also suspended and isolated from the main body of the aluminum conductive busbar 4 through the hollowed-out grooves 51 to prevent external rigid interference when subjected to pressure deformation.

[0045] like Figure 3 and Figure 4 As shown, on the elastic frame-shaped outline, there are two symmetrically distributed solder points 9 above and below each corresponding thin shaft 53, for a total of four solder points 9 on the entire needle. Specifically, the left longitudinal section 521 has one solder point 9 protruding towards the gold-plated surface 21 above and below the thin shaft 53, and the right longitudinal section 522 has one solder point 9 protruding towards the gold-plated surface 21 above and below the thin shaft 53. In the welding process, the resistance welding equipment performs pressure resistance welding on the gold-plated surface 21 of the capacitor core 2 through these four solder points 9.

[0046] These four solder points 9 form a regular two-dimensional matrix distribution of press-welded structure in space. In terms of electrical characteristics, since the solder points 9 are arranged in a two-dimensional matrix, the working current can be divided into four parallel short-path paths from the gold-plated surface 21 and flow into the aluminum busbar, which greatly disperses the single-point current density, thereby significantly reducing the contact resistance and improving the overcurrent carrying capacity and thermal stability during operation.

[0047] like Figure 4 As shown, the aluminum busbar connection end 41 and the copper conductive busbar 3 are tightly stacked in a face-to-face contact manner. The contact interface between the two is formed by laser welding to form multiple fusion welds, thereby rigidly welding and fixing the two together. In actual use, other methods such as friction stir welding, electromagnetic pulse welding, and ultrasonic welding can also be used to achieve high-quality connection of dissimilar metals such as copper and aluminum, thereby improving the mechanical strength and conductivity of the bonding interface.

[0048] Because copper and aluminum have different coefficients of linear expansion, if the joint is exposed to humid air for a long time, it is prone to thermal stress creep during thermal cycling and is also highly susceptible to electrochemical corrosion between dissimilar metals. Therefore, in this embodiment, the welded joints of the positive aluminum busbar connection end 411 and the positive copper busbar 33, and the welded joints of the negative aluminum busbar connection end 412 and the negative copper busbar 34, are both contained within the internal cavity of the insulating shell 1. After the internal welding and capacitor core 2 assembly are completed, an epoxy resin composite is filled into the insulating shell 1 using an automated potting process. This epoxy resin composite completely embeds the welded joints and keeps them in a moisture-sealed state, thereby isolating them from external moisture oxidation and the creep heating hazards caused by thermal cycling stress.

[0049] In this embodiment, the copper busbar 3 includes a positive copper busbar 33 and a negative copper busbar 34 arranged in a stacked manner. The positive copper busbar 33 and the negative copper busbar 34 are respectively formed by stamping and bending a single piece of copper sheet. The positive copper busbar 33 has a positive copper busbar lead-out terminal 311 extending to the outside of the insulating shell 1, and a plurality of positive copper busbar connection terminals 321 located inside the insulating shell 1 and arranged laterally at intervals. The negative copper busbar 34 has a negative copper busbar lead-out terminal 312 extending to the outside of the insulating shell 1, and a plurality of negative copper busbar connection terminals 322 located inside the insulating shell 1 and arranged laterally at intervals. The plurality of positive copper busbar connection terminals 321 and the plurality of negative copper busbar connection terminals 322 are arranged side by side in a one-to-one correspondence.

[0050] The aluminum conductive bus 4 includes a positive aluminum bus 42 electrically connected to the gold-plated surface 21 on one side of the capacitor core 2, and a negative aluminum bus 43 electrically connected to the gold-plated surface 21 on the other side of the capacitor core 2; the positive aluminum bus 42 extends with a positive aluminum bus connection end 411, and the negative aluminum bus 43 extends with a negative aluminum bus connection end 412; the positive aluminum bus connection end 411 is attached to and welded to the positive copper bus 33, and the negative aluminum bus connection end 412 is attached to and welded to the negative copper bus 34.

[0051] The positive and negative copper and aluminum busbars are arranged in a staggered manner along the horizontal axis to realize the modular application of the flexible welding unit 5 in the bipolar symmetrical structure, which greatly simplifies the internal assembly and welding process of the multi-core large-capacity filter capacitor.

[0052] In this embodiment, an insulating isolation component for achieving potential isolation between the two poles is also included. The insulating isolation component includes a second insulating plate 62 sandwiched between the positive copper busbar 33 and the negative copper busbar 34, and a first insulating plate 61 covering the outside of the positive copper busbar 33, so as to stack and fix the positive copper busbar 33 and the negative copper busbar 34 into a stacked busbar structure.

[0053] The first insulating plate 61 and the second insulating plate 62 tightly stack and constrain the positive copper busbar 33 and the negative copper busbar 34, achieving high-reliability potential isolation between the poles while significantly reducing the distance between the positive and negative plates and lowering the parasitic inductance of the busbar circuit.

[0054] The first insulating plate 61 and the second insulating plate 62 are both integrally formed three-dimensional multi-directional bent plate structures, which are respectively attached to the bent surfaces of the positive copper busbar 33 and the negative copper busbar 34. The insulating plates adopt an integrally formed three-dimensional multi-directional bent structure, which can fit the complex bent surface of the busbar, greatly improving the inter-electrode creepage distance while optimizing the compactness of the spatial structure.

[0055] The vehicle environment is accompanied by high-frequency and severe mechanical vibration. In order to prevent metal fatigue fracture at the end of the suspended busbar, this embodiment also includes a fixing plate 7 disposed on the side of the insulating shell 1 and fixedly connected to the insulating shell 1. The fixing plate 7 is provided with a buckle 71 on the side facing the negative copper busbar 34. One end of the negative copper busbar 34 is fastened and limited on the fixing plate 7 by the buckle 71.

[0056] By setting a buckle 71 on one side of the fixed plate 7 to directly fasten and lock the negative copper busbar 34, the boltless fastening of the entire stacked busbar assembly is achieved. This simplifies the mechanical structure, eliminates the risk of local high-voltage discharge breakdown caused by metal fastening bolts, and significantly improves the vibration and impact resistance of the whole machine.

[0057] In this embodiment, a terminal positioning seat 8 is mounted on the upper edge of the insulating shell 1. Multiple isolation baffles 81 are integrally extended upward above the terminal positioning seat 8. Each isolation baffle 81 is inserted between adjacent positive copper busbar connection terminals 321 and negative copper busbar connection terminals 322 to achieve creepage isolation.

[0058] Multiple isolation baffles 81 above the terminal positioning base 8 provide physical rigid isolation between adjacent and intersecting positive copper busbar connection terminals 321 and negative copper busbar connection terminals 322, significantly improving the spatial electrical clearance and anti-arc short-circuit capability at the top of the capacitor.

[0059] In this embodiment, the gold-plated surface 21 of the capacitor core 2 is a zinc-tin-copper alloy gold-plated layer without solder medium, and the solder joints 9 on the aluminum conductive busbar 4 are directly pressure-welded to it by an automated resistance welding device, eliminating the need for solder wire or solder paste in the entire manufacturing process.

[0060] Traditional soldering processes require a large amount of heat input, necessitating an extremely thick gold plating layer as a heat buffer to prevent damage to the thin-film dielectric inside the capacitor core. However, the resistance welding using the elastic soldering pin 52 in this embodiment requires very little instantaneous heat, resulting in a very low risk of burning the gold plating surface 21 of the capacitor core 2. Therefore, in terms of manufacturing process, the deposition thickness of the zinc-tin-copper alloy gold plating layer in this embodiment is significantly reduced by more than 20% compared to the gold plating layer thickness in traditional soldering processes. This saves on soldering costs while further reducing the cost of non-ferrous metal raw materials.

[0061] The beneficial effects of this invention are as follows: through the copper-aluminum combination design, the external connection uses copper busbars to ensure creep resistance and conductivity reliability, while the internal connection uses aluminum busbars to achieve stringent cost reduction. The welding part is embedded in epoxy resin for moisture and oxidation prevention. The uniquely designed frame-shaped elastic welding pins 52 and narrowed thin shafts 53 on the aluminum busbars can provide precise mechanical stress release and micro-oscillation assembly margin for automated pressure bonding resistance welding, ensuring matrix-style pressure equalization bonding of multiple welding points 9, eliminating the high cost of solder wire. Since the resistance welding energy is low and there is no risk of burns, this invention can reduce the thickness of the gold plating layer of the capacitor core 2 by more than 20%, achieving a significant overall cost reduction effect.

[0062] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer", etc., which indicate the direction or positional relationship, are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0063] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0064] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A DC filter capacitor with an aluminum busbar elastic welding pin structure, comprising an insulating shell (1) and at least one capacitor core (2) housed within the insulating shell (1), the capacitor core (2) having a gold-plated surface (21); characterized in that, Also includes: A copper busbar (3) has copper busbar lead-out terminals (31) extending to the outside of the insulating housing (1) and copper busbar connection terminals (32) located inside the insulating housing (1). An aluminum conductive bus (4) is located inside the insulating shell (1) and electrically connected to the gold-plated surface (21). An elastic welding unit (5) is provided on the area of ​​the aluminum conductive bus (4) corresponding to the gold-plated surface (21). The elastic welding unit (5) includes a hollow groove (51) opened on the aluminum conductive bus (4) and an elastic welding needle (52) suspended inside the hollow groove (51). The side of the elastic welding needle (52) forms a thin shaft (53) with a narrowed transverse width. The elastic welding needle (52) is connected to the aluminum conductive bus (4) and suspended in the hollow groove (51). The elastic welding needle (52) is provided with multiple welding points (9) and is pressed and welded to the gold-plated surface (21) through multiple welding points (9). The aluminum conductive bus (4) extends to an aluminum bus connection end (41), which is attached to and welded to the copper conductive bus (3). The welded joint of the two is located inside the insulating shell (1) and is completely embedded and sealed by the epoxy resin solid body filled in the insulating shell (1).

2. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 1, characterized in that: The elastic welding needle (52) includes an elastic frame-shaped outline, which is formed by a left longitudinal section (521) and a right longitudinal section (522) arranged on the same plane, an upper transverse arch (523) that connects the upper ends of the left longitudinal section (521) and the right longitudinal section (522) respectively, and a lower transverse arch (524) that connects the lower ends of the left longitudinal section (521) and the right longitudinal section (522). The upper end of the upper transverse arch (523) is connected to the aluminum conductive bus (4), and the lower end of the lower transverse arch (524) is connected to the aluminum conductive bus (4), so that the left longitudinal section (521) and the right longitudinal section (522) are suspended in the hollow groove (51) and form a lateral deformation gap with the aluminum conductive bus (4).

3. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 2, characterized in that: The thin shaft (53) consists of two shafts, which are integrally formed in the middle of the left longitudinal section (521) and the right longitudinal section (522), respectively. The thin shaft (53) located in the middle of the left longitudinal segment (521) has a lateral width narrower than the upper and lower halves of the left longitudinal segment (521), so that the left longitudinal segment (521) can form a flexible structure that can be elastically deformed; the thin shaft (53) located in the middle of the right longitudinal segment (522) has a lateral width narrower than the upper and lower halves of the right longitudinal segment (522), so that the right longitudinal segment (522) can form a flexible structure that can be elastically deformed; The two thin shafts (53) form a lateral deformation gap with the aluminum conductive busbar (4) through the hollowed-out groove (51) on their outer sides.

4. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 3, characterized in that: The elastic frame-shaped outline has two solder points (9) symmetrically distributed above and below each thin shaft (53); The left longitudinal segment (521) has a solder point (9) above and below the connected thin shaft (53), and the right longitudinal segment (522) has a solder point (9) above and below the connected thin shaft (53), so that the four solder points (9) form a two-dimensional matrix distribution of the pressure welding structure on the gold-plated surface (21).

5. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 1, characterized in that: The copper busbar (3) includes a positive copper busbar (33) and a negative copper busbar (34) arranged in a stacked manner. The positive copper busbar (33) and the negative copper busbar (34) are formed by stamping and bending a single piece of copper sheet. The positive copper busbar (33) has a positive copper busbar lead-out terminal (311) extending to the outside of the insulating shell (1) and a plurality of positive copper busbar connection terminals (321) located inside the insulating shell (1) and arranged laterally at intervals. The negative copper busbar (34) has a negative copper busbar lead-out terminal (312) extending to the outside of the insulating shell (1) and a plurality of negative copper busbar connection terminals (322) located inside the insulating shell (1) and arranged laterally at intervals. The plurality of positive copper busbar connection terminals (321) and the plurality of negative copper busbar connection terminals (322) are arranged in a staggered manner in a one-to-one correspondence. The aluminum conductive bus (4) includes a positive aluminum bus (42) electrically connected to the gold-plated surface (21) on one side of the capacitor core (2), and a negative aluminum bus (43) electrically connected to the gold-plated surface (21) on the other side of the capacitor core (2); the positive aluminum bus (42) extends with a positive aluminum bus connection end (411), and the negative aluminum bus (43) extends with a negative aluminum bus connection end (412); the positive aluminum bus connection end (411) is attached to and welded to the positive copper bus (33), and the negative aluminum bus connection end (412) is attached to and welded to the negative copper bus (34).

6. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 5, characterized in that: It also includes an insulating isolation component for achieving potential isolation between the two poles. The insulating isolation component includes a second insulating plate (62) sandwiched between the positive copper busbar (33) and the negative copper busbar (34), and a first insulating plate (61) covering the outside of the positive copper busbar (33) to stack and fix the positive copper busbar (33) and the negative copper busbar (34) into a stacked busbar structure.

7. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 6, characterized in that: The first insulating plate (61) and the second insulating plate (62) are both integrally formed three-dimensional multi-directional bent plate structures, so as to be in contact with the bent surfaces of the positive electrode copper busbar (33) and the negative electrode copper busbar (34), respectively.

8. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 6, characterized in that: It also includes a fixing plate (7) disposed on the side of the insulating shell (1) and fixedly connected to the insulating shell (1). The fixing plate (7) has a buckle (71) on the side facing the negative electrode copper busbar (34). One end of the negative electrode copper busbar (34) is fastened and limited on the fixing plate (7) by the buckle (71).

9. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 5, characterized in that: The upper edge of the insulating shell (1) is equipped with a terminal positioning seat (8). Multiple isolation baffles (81) are integrally extended upward above the terminal positioning seat (8). Each isolation baffle (81) is inserted between adjacent positive copper busbar connection terminals (321) and negative copper busbar connection terminals (322) to achieve creepage isolation.

10. The DC filter capacitor with an aluminum busbar elastic welding pin structure according to claim 1, characterized in that: The gold-plated surface (21) of the capacitor core (2) is a zinc-tin-copper alloy gold-plated layer without solder medium, and multiple solder points (9) are pressed and welded on the zinc-tin-copper alloy gold-plated layer.

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