Method for connecting current collector and current sampling module

Abstract

The application relates to the current detection technical field, in particular to a lapping method of a current detection resistor and a conductive sheet and a current sampling module. The lapping method comprises the following steps: providing a circuit board and a current detection resistor, mounting and fixing the current detection resistor in a specified area of the circuit board; providing a conductive sheet, the conductive sheet comprises a first conductive sheet and a second conductive sheet, the first conductive sheet and the second conductive sheet are respectively arranged on the outer side of a first terminal and a second terminal of the current detection resistor and are fixed on the circuit board, and gaps exist between the first conductive sheet and the first terminal and between the second conductive sheet and the second terminal; the gaps are filled with molten solder, the first conductive sheet is welded and connected with the first terminal, the second conductive sheet is welded and connected with the second terminal, a solder layer is formed after the solder is solidified, and the first conductive sheet, the second conductive sheet and the current detection resistor form a conductive path through the solder layer.

Description

Technical Field

[0001] This application relates to the field of current detection technology, specifically to a method for connecting a current sensing resistor and a conductive sheet, and a current sampling module. Background Technology

[0002] Current sensing is fundamental to the functionality of a battery management system (BMS). High-precision and high-reliability current sensing is crucial for battery status monitoring, energy management, and safety protection. With the widespread application of large-capacity battery cells, the charging and discharging currents of battery systems are continuously increasing, placing higher demands on the high-current sensing capabilities of battery management systems.

[0003] Currently, high current detection in battery management systems typically uses a shunt 10. For example... Figure 1 As shown, the existing shunt 10 is generally a three-section structure, consisting of two copper metal terminals 11 and a manganese copper alloy resistor body 12 connected together by welding. During operation, the shunt 10 is connected in series in the main current circuit, and current detection is achieved by measuring the voltage drop across its resistor body 12.

[0004] In the production process of this shunt, the metal terminal 11 and the resistor body 12 are first placed in a first type of fixture, and then welded to the resistor body 12 using a high-energy electron beam. Next, the welded metal terminal 11 and resistor body 12 are transferred to a second type of fixture and placed on a circuit board for further welding. It is evident that the manufacturing of existing shunts requires multiple clamping operations, the use of two different types of fixtures, and the welding between the metal terminal 11 and the resistor body 12 relies on high-energy electron beam welding equipment. The entire production process is complex and involves numerous steps, resulting in a manufacturing cost for the shunt 10 that is far higher than that of ordinary electronic components.

[0005] Furthermore, to achieve the electrical connection between the shunt 10 and the circuit board, existing technologies offer two assembly methods: surface mount technology (SMT) and lead soldering. In the SMT method, the shunt 10, as an irregularly shaped component, exceeds the surface area of ​​the circuit board, requiring a dedicated tray fixture. In the lead soldering method, the upper surface of the circuit board surrounding the shunt 10 is typically occupied by other taller components. To avoid interference, ordinary wave soldering equipment cannot be used due to insufficient solder wave height, necessitating modification to dedicated high-wave equipment. These assembly methods not only increase process complexity and equipment requirements but also further drive up the cost of the shunt 10. Summary of the Invention

[0006] The purpose of this invention is to provide a method for connecting a current sensing resistor and a conductive sheet, which aims to solve the problem of high cost in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for connecting a current-sensing resistor to a conductive sheet, comprising the following steps: S10: Provide a circuit board and a current sensing resistor, and mount and fix the current sensing resistor in a designated area on the front side of the circuit board; S20: Provide a conductive sheet, the conductive sheet including a first conductive sheet and a second conductive sheet, the first conductive sheet and the second conductive sheet are respectively placed outside the first terminal and the second terminal of the current sensing resistor, and fixed on the circuit board, wherein there is a gap between the first conductive sheet and the first terminal and between the second conductive sheet and the second terminal; S30: The gap is filled with molten solder, so that the first conductive sheet is welded to the first terminal and the second conductive sheet is welded to the second terminal. After the solder solidifies, a solder layer is formed. The first conductive sheet, the second conductive sheet and the current sensing resistor form a conductive path through the solder layer.

[0008] In some embodiments, the conductive sheet has a plating layer made of the same material as the solder.

[0009] In some embodiments, in step S30, the solder fills the gap using a wave soldering process.

[0010] In some embodiments, the preheating temperature of the wave soldering process is 140℃~160℃, the overall temperature rise slope is ≤3℃ / second, the welding zone temperature is 270℃~280℃, and the chain conveying speed is 800mm / min~900mm / min.

[0011] In some embodiments, step S10 specifically includes: S11: Print an adhesive layer in a designated area on the circuit board; S12: Attach the current-sensing resistor onto the adhesive layer; S13: The adhesive layer is cured by reflow soldering to fix the current sensing resistor on the circuit board.

[0012] In some embodiments, in step S10, the number of current sensing resistors is several, and the several current sensing resistors are mounted and fixed in parallel in a designated area of ​​the circuit board.

[0013] In some embodiments, there is a spacing of 0.3mm-0.4mm between two adjacent current sensing resistors.

[0014] In some embodiments, step S10 further includes: mounting and fixing a thermistor on the back of the circuit board at a position corresponding to the designated area, the thermistor being used to detect the temperature of the current sensing resistor.

[0015] In some embodiments, the current sensing resistor is a manganese copper alloy current sensing resistor.

[0016] In some embodiments, step S20 specifically includes: The first conductive sheet and the second conductive sheet are respectively positioned on the circuit board to define the gap; A locking structure is used to lock the first conductive sheet and the second conductive sheet onto the circuit board.

[0017] In some embodiments, the solder is tin; in step S20, the gap is 0.7mm-0.9mm.

[0018] In some embodiments, the circuit board is provided with a first pad area and a second pad area, the first conductive sheet has a first soldering portion for soldering to a first terminal, and the second conductive sheet has a second soldering portion for soldering to a second terminal; In step S20, the first terminal and the first solder joint are both located in the first solder pad area, and the second terminal and the second solder joint are both located in the second solder pad area. In step S30, the solder fills the gap while covering the first pad area and the second pad area.

[0019] In some embodiments, in step S20, when the first soldering part and the second soldering part are respectively fixed on the first solder pad area and the second solder pad area, the first solder pad area has a first solder extension area that does not overlap with the first soldering part, and the second solder pad area has a second solder extension area that does not overlap with the second soldering part; the projection of the first solder extension area and the second solder extension area in the thickness direction of the circuit board surrounds the periphery of the first soldering part and the second soldering part, respectively.

[0020] This application also provides a current sampling module, which is made using the above-described method of connecting the current sensing resistor and the conductive sheet.

[0021] In some embodiments, a foolproof structure is provided between the first conductive sheet, the second conductive sheet and the circuit board.

[0022] In some embodiments, at least two positioning structures are provided between the first conductive sheet and the circuit board, and between the second conductive sheet and the circuit board, respectively. The positioning structure includes a positioning hole provided on one of the conductive sheet and the circuit board, and a positioning post provided on the other. The positioning structure between the first conductive sheet and the circuit board and the positioning structure between the second conductive sheet and the circuit board are at least partially misaligned to form the foolproof structure.

[0023] The current generated by the overlapping method of the current sensing resistor and conductive sheet provided by the present invention has the following advantages: In the overlapping method of this application, the current sensing resistor is first fixed to the circuit board, then the conductive sheet is fixed to the circuit board, and finally the gap is filled with molten solder. Throughout the entire operation, the mounting of the current sensing resistor, the fixing of the conductive sheet, and the filling of the molten solder are all completed on the same circuit board. There is no need to transfer semi-finished products between different fixtures; therefore, only one set of fixtures is required to complete all processes, eliminating the cumbersome process of multiple clamping and fixture switching in traditional shunt manufacturing. Furthermore, after the conductive sheet is fixed to the circuit board, the overlapping welding of the two can be directly completed with molten solder, without relying on high-energy electron beam welding equipment, special support fixtures, or modifications to high-energy equipment, thus significantly reducing equipment investment and manufacturing costs.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0025] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are designated as the same elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0026] Figure 1 This is a schematic diagram of the structure of a current splitter in the prior art.

[0027] Figure 2 This is a flowchart illustrating a method for connecting a current-sensing resistor and a conductive sheet according to an embodiment of this application; Figures 3 to 6 This is a schematic diagram of the current sampling module during the manufacturing process in one embodiment of this application.

[0028] Reference numerals: 10, Shunt; 11, Metal terminal; 12, Resistor body; 13, Solder joint; 20, Current sampling module; 21, Circuit board; 211, Designated area; 212, First pad area; 2121, First solder extension area; 213, Second pad area; 2131, Second solder extension area; 22, Current sensing resistor; 23, First conductive sheet; 231, First solder joint; 24, Second conductive sheet; 241, Second solder joint; 25, Gap; 261, Locking pin; 262, Locking hole; 271, Positioning hole; 28, Adhesive layer; 29, Thermistor. Detailed Implementation

[0029] The present invention will now be described in detail with reference to specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0030] It should be noted that, unless otherwise expressly specified and limited, the terms “transfer to,” “insert to,” “away from,” “extend,” “toward,” “insertion,” etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. The terms "installation," "fitting," "connection," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. "Fixing" can be bolted, clipped, or glued. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature. "A plurality" or "several" means two or more. In addition, "and / or" includes any and all combinations of one or more of the related listed items. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Figure 2 A flowchart illustrating the method of connecting the current sensing resistor 22 to the conductive sheet according to an embodiment of this application is shown. The method of connecting the current sensing resistor 22 to the conductive sheet according to an embodiment of this application is used to manufacture a current sampling module 20, which replaces the circuit board 21 and shunt assembly in the prior art. Compared with the prior art, the current sampling module 20 has at least the advantage of low cost.

[0033] Please combine Figures 3 to 5The current sampling module 20 includes a circuit board 21, a current sensing resistor 22, and conductive sheets. The circuit board 21 is a prefabricated board with a designated area 211 pre-planned on its surface for mounting the current sensing resistor 22, preferably located in the middle area of ​​the circuit board 21. The conductive sheets are fixed to the circuit board 21 and include a first conductive sheet 23 and a second conductive sheet 24 respectively arranged outside the first terminal and the second terminal of the current sensing resistor 22. The first conductive sheet 23 and the second conductive sheet 24 are soldered to the first terminal and the second terminal respectively to achieve electrical connection. Specifically, gaps 25 are formed between the first conductive sheet 23 and the first terminal, and between the second conductive sheet 24 and the second terminal. Solder fills the gaps 25 and, after curing, forms a solder layer (not shown), thereby achieving electrical connection between the first conductive sheet 23 and the first terminal, and between the second conductive sheet 24 and the second terminal.

[0034] The current sampling module 20 is installed in the battery module and electrically connected to the battery management system (BMS). It is used to collect the current signal of the battery module in real time and transmit it to the control unit of the battery management system to monitor and manage the charging and discharging status of the battery. During operation, the current sensing resistor 22 can carry a large current of about 200A.

[0035] In this embodiment, the first conductive sheet 23 and the second conductive sheet 24 are fixed to the circuit board 21 by a locking structure. In one example, the locking structure includes a locking pin 261 disposed on the first conductive sheet 23 and the second conductive sheet 24 and a locking hole 262 disposed on the circuit board 21. The locking pin 261 cooperates with the locking hole 262 to lock the circuit board 21 and the conductive sheet.

[0036] In one embodiment, a foolproof structure is provided between the first conductive sheet 23, the second conductive sheet 24 and the circuit board 21 to ensure that the first conductive sheet 23 and the second conductive sheet 24 are installed in the correct orientation at their corresponding positions on the circuit board 21. This prevents misalignment of the conductive sheet and the current sensing resistor 22 due to incorrect installation, which could lead to poor soldering or even a short circuit. This foolproof structure helps improve the assembly reliability of mass production.

[0037] Based on the above embodiments, in order to ensure that the gap 25 does not shift when the conductive sheet is locked on the circuit board 21, at least two positioning structures are provided between the first conductive sheet 23 and the circuit board 21, and between the second conductive sheet 24 and the circuit board 21. The positioning structure specifically includes a positioning hole 271 provided on one of the conductive sheet and the circuit board 21, and a positioning post provided on the other.

[0038] To simplify the structure and reduce costs, the positioning structure between the first conductive sheet 23 and the circuit board 21 and the positioning structure between the second conductive sheet 24 and the circuit board 21 are at least partially misaligned to form a foolproof structure.

[0039] In this embodiment, the misalignment is achieved using different spacings. Specifically, two adjacent positioning structures between the first conductive sheet 23 and the circuit board 21 have a first spacing and form a first foolproof structure; two adjacent positioning structures between the second conductive sheet 24 and the circuit board 21 have a second spacing and form a second foolproof structure. The dimensions of the first spacing and the second spacing are different. In other embodiments, this misalignment can also be achieved using different arrangement positions, such as the first foolproof structure being arranged vertically and the second foolproof structure being arranged horizontally; or, the dimensions of the positioning posts and positioning holes in the first foolproof structure are different from the dimensions of the positioning posts and positioning holes in the second foolproof structure.

[0040] To facilitate understanding of the connection method and the current sampling module 20 in this application, the following is a detailed explanation. Figures 2 to 6 A detailed explanation is provided. The method for connecting the current sensing resistor 22 to the conductive sheet includes the following steps: S10: Provide a circuit board 21 and a current sensing resistor 22, and mount and fix the current sensing resistor 22 in a designated area 211 on the front side of the circuit board 21, see Figure 4 ; S20: A conductive sheet is provided, comprising a first conductive sheet 23 and a second conductive sheet 24. The first conductive sheet 23 and the second conductive sheet 24 are respectively placed outside the first terminal and the second terminal of the current sensing resistor 22 and fixed on the circuit board 21. A gap 25 is provided between the first conductive sheet 23 and the first terminal, and between the second conductive sheet 24 and the second terminal. Figure 5 ; S30: The gap 25 is filled with molten solder, so that the first conductive sheet 23 is welded to the first terminal and the second conductive sheet 24 is welded to the second terminal. After the solder solidifies, a solder layer is formed. The first conductive sheet 23, the second conductive sheet 24 and the current sensing resistor 22 form a conductive path through the solder layer.

[0041] In the above-described overlapping method, the current-sensing resistor 22 is first fixed to the circuit board 21, then the conductive sheet is fixed to the circuit board 21, and finally the gap is filled with molten solder. Throughout the entire operation, the mounting of the current-sensing resistor 22, the fixing of the conductive sheet, and the filling of the molten solder are all completed on the same circuit board 21. There is no need to transfer semi-finished products between different fixtures; therefore, only one set of fixtures is needed to complete all processes, eliminating the cumbersome process of multiple clamping and fixture conversions in traditional shunt manufacturing. Furthermore, after the conductive sheet is fixed to the circuit board 21, the overlapping welding of the two can be directly completed with molten solder, without relying on high-energy electron beam welding equipment, special support fixtures, or modifications to high-wave equipment, thus significantly reducing equipment investment and manufacturing costs. Taking a 280A continuous current-carrying scheme as an example, the manufacturing cost using this overlapping method is reduced by more than 80% compared to the traditional shunt scheme.

[0042] In this overlapping method, the current sensing resistor 22 can be a standard surface mount component. Therefore, "the current sensing resistor 22 can be mounted and fixed on the circuit board 21" can be completed by standard SMT process, which is compatible with existing conventional technology and helps to further simplify the operation process and reduce costs.

[0043] In one alternative embodiment, in step S10, the number of current-sensing resistors 22 is several, and the several current-sensing resistors 22 are mounted and fixed in parallel within a designated area of ​​the circuit board 21. In other embodiments, the sensing resistor may also be a single resistor.

[0044] In practical applications, there is a spacing of 0.3mm-0.4mm between two adjacent current sensing resistors 22 (specifically, 0.3mm, 0.35mm, or 0.4mm). This saves space on the circuit board 21 and ensures thermal balance and uniform current distribution among the resistors. Because manganese-copper alloy has low resistivity and a low temperature coefficient, its resistance changes very little with temperature, exhibiting extremely low temperature drift. It is suitable for operation over a wide temperature range, ensuring long-term stability of current detection. Therefore, in this embodiment, the current sensing resistor 22 is preferably a manganese-copper alloy resistor to ensure stable resistance under high current conditions.

[0045] In an alternative embodiment, step S10 specifically includes: S11: Print adhesive layer 28 in a designated area 211 of circuit board 21. Specifically, for example, place circuit board 21 in an automatic adhesive layer printing machine 28, and print adhesive layer 28 on the mounting position of current sensing resistor 22 on circuit board 21 using a stencil. See [link to documentation]. Figure 3 ; S12: The current sensing resistors 22 are mounted onto the adhesive layer 28. Specifically, for example, the circuit board 21 with the adhesive layer 28 printed on it is conveyed to an automatic placement machine. The automatic placement machine mounts each current sensing resistor 22 at a certain interval in the designated area 211 of the circuit board 21 according to a preset program. See Figure 4 ; S13: The adhesive layer 28 is cured by reflow soldering to fix the current sensing resistor 22 onto the circuit board 21. Specifically, for example, the circuit board 21 with the current sensing resistor 22 mounted is sent into a reflow soldering machine, the peak temperature of the reflow soldering zone is set to 140°C~150°C, and the duration is 60~90 seconds, so that the adhesive layer 28 is completely cured, thereby firmly fixing the current sensing resistor 22 onto the circuit board 21.

[0046] In the specific example above, the current sensing resistor 22 is pre-fixed to the circuit board 21 by printing the adhesive layer 28 and reflow soldering. This prevents the current sensing resistor 22 from shifting due to solder erosion or high-temperature airflow during the subsequent "molten solder filling gap 25" process, ensuring the consistency of the gap 25 between the conductive sheet and the terminals of the current sensing resistor 22, thereby ensuring the quality and reliability of the lap soldering. In practical applications, this adhesive layer can be formed using red glue.

[0047] In an alternative embodiment, step S10 further includes: mounting and fixing a thermistor 29 on the back of the circuit board 21 at a position corresponding to the designated area 211. The thermistor 29 is used to detect the temperature of the current sensing resistor 22. Figure 6 .like Figure 6 As shown in the dashed box, this area is the location on the back of the circuit board 21 corresponding to the designated area 211.

[0048] Specifically, between steps S12 and S13, the following steps are included: mounting a thermistor 29 on the back of the circuit board 21 at a position corresponding to the designated area 211; in step S13, the thermistor 29 and the current sensing resistor 22 are fixed on the circuit board 21 through the same reflow soldering process, and the thermistor 29 is used to detect the temperature of the current sensing resistor 22.

[0049] In this embodiment, the circuit board 21 only carries the sampling signal line and the trace of the thermistor 29. Specifically, the sampling line of the current sensing resistor 22 is led out from the inside of the current sensing resistor 22 pad to ensure the accuracy of the sampling voltage. The circuit board 21 has traces for the thermistor 29, which are electrically connected to the traces through their pads. The traces only transmit the detection signal of the thermistor 29 and do not transmit the main current.

[0050] Since the thermistor 29 is directly mounted to the back of the circuit board 21 in the same reflow soldering process, and the thermistor and current sensing resistor 22 are positioned opposite each other on both sides of the circuit board 21, and because the circuit board 21 is typically thin, the thermal resistance between the thermistor 29 and the current sensing resistor 22 is extremely low. Therefore, the thermistor 29 can accurately reflect the true operating temperature of the current sensing resistor 22 in real time, providing precise input parameters for the temperature compensation algorithm of the battery management system, further improving the accuracy and long-term stability of high-current detection. In a specific example, the thermistor 29 is a negative temperature coefficient (NTC) thermistor 29.

[0051] In an alternative embodiment, step S20 specifically includes: S21: Position the first conductive sheet 23 and the second conductive sheet 24 on the circuit board 21 to define the gap 25. Specifically, for example, place the first conductive sheet 23 and the second conductive sheet 24 on the circuit board 21 respectively. At this time, the positioning post is inserted into the corresponding positioning hole 271 to realize the positioning of the first conductive sheet 23 and the second conductive sheet 24 on the circuit board 21, thereby defining the gap 25 and ensuring that the gap 25 will not change in subsequent processes.

[0052] S22: A locking structure is used to lock the first conductive sheet 23 and the second conductive sheet 24 onto the circuit board 21. In a specific example, the locking pin 261 is screwed into the locking hole 262 to lock the first conductive sheet 23 and the second conductive sheet 24 onto the circuit board 21, thereby ensuring that the conductive sheets will not shift during the subsequent soldering process, ensuring the uniformity of solder filling and the consistency of soldering quality.

[0053] In this embodiment, the solder is tin. In step S20, the gap 25 is selected within the range of 0.7mm-0.9mm to ensure that the solder layer can completely and densely fill the gap 25, forming a reliable metallurgical bond. In other embodiments, the solder can also be a lead-free solder, such as a tin-silver-copper alloy, a tin-copper alloy, or a zinc-aluminum based solder, or other solders with melting points lower than the temperature resistance limits of the conductive sheet and the circuit board. In practical applications, the selection of materials for the solder, conductive sheet, and circuit board can be made according to actual needs and matching conditions such as the melting point of the selected materials.

[0054] It should be noted that, in practical applications, it was found that the size of the gap 25 between the conductive sheet and the terminal of the current sensing resistor 22 has a significant impact on the welding quality. To address this issue, multiple sets of test samples with different gaps 25 (0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, and 1.2mm) were prepared. Except for the gap 25 parameter, all other process conditions remained consistent for each sample. After the samples were fused and solidified, the solder filling was observed under a microscope, and the contact impedance and temperature rise data for each group were tested using an impedance analyzer and a thermal imager. Experimental results show that when the gap 25 is less than 0.7 mm, the solder cannot flow in sufficiently due to the narrow gap, resulting in incomplete solder filling in some samples. When the gap 25 is greater than 0.8 mm, the solder tends to collapse under gravity after filling, leading to uneven solder distribution in the overlap area and a significant increase in contact resistance. When the gap 25 is between 0.7 mm and 0.9 mm (specifically 0.7 mm, 0.8 mm, or 0.9 mm), the solder can fully fill the gap 25 and evenly cover the entire overlap area, resulting in the lowest contact resistance and the smallest temperature rise after welding. Among these, a gap of 0.8 mm yields the best results, with the most complete and dense solder filling, enabling the conductive sheet and the current sensing resistor 22 terminal to be completely welded together.

[0055] In an alternative embodiment, the circuit board 21 is provided with a first pad area 212 and a second pad area 213, the first conductive sheet 23 has a first soldering portion 231 for soldering to a first terminal, and the second conductive sheet 24 has a second soldering portion 241 for soldering to a second terminal.

[0056] In step S20, the first terminal and the first solder part 231 are simultaneously located in the first solder pad area 212, and the second terminal and the second solder part 241 are simultaneously located in the second solder pad area 213. In step S30, the solder fills the gap 25 while simultaneously covering the first pad area 212 and the second pad area 213.

[0057] In this example, by setting the first pad area 212 and the second pad area 213, the solder can be fully filled between the first terminal and the first welded part 231 and between the second terminal and the second welded part 241, avoiding gaps during the welding process, thereby enhancing the welding strength and electrical reliability.

[0058] In a preferred embodiment, in step S20, when the first soldering portion 231 and the second soldering portion 241 are respectively fixed on the first solder pad area 212 and the second solder pad area 213, the first solder pad area 212 has a first solder extension area 2121 that does not overlap with the first soldering portion 231, and the second solder pad area 213 has a second solder extension area 2131 that does not overlap with the second soldering portion 241. Projected along the thickness direction of the circuit board 21, the first solder extension area 2121 and the second solder extension area 2131 respectively surround the periphery of the first soldering portion 231 and the second soldering portion 241. This arrangement allows subsequent solder to fully cover and encapsulate the first soldering portion 231 and the second soldering portion 241, achieving a reliable soldering structure and further enhancing the soldering strength and conductivity reliability between the conductive sheet and the circuit board 21.

[0059] As selected in the previous example, the solder is tin. To ensure that the conductive sheet does not melt during the soldering process, the melting point of the conductive sheet usually needs to be higher than that of the solder. In this embodiment, the material of the conductive sheet is aluminum. To avoid microscopic defects such as porosity and microcracks caused by dissimilar metal welding, in an alternative embodiment, the conductive sheet has a plating layer (not shown), the material of which is the same as that of the solder. During soldering, the solder extends between the plating layer and the current sensing resistor 22.

[0060] It should be noted that, as selected in the previous example, the current sensing resistor 22 is preferably a manganese copper alloy resistor. This current sensing resistor 22 can be a standard component, which can be obtained externally. The terminals of the current sensing resistor 22, as a standard component, are usually surface-treated (e.g., tin-plated) to have good wettability with solder.

[0061] By setting the plating material to be the same as the solder material, microscopic defects such as porosity and microcracks caused by differences in physical properties such as melting point and coefficient of thermal expansion during dissimilar metal welding can be avoided. This helps reduce contact resistance, and the low impedance state is stable and does not drift over time, resulting in high current detection accuracy and good long-term consistency. Simultaneously, it provides a wide, low-thermal-resistance path for heat conduction, allowing heat to be efficiently conducted to the conductive sheet and rapidly dissipated to the surrounding environment, achieving rapid heat dissipation. This reduces the operating temperature rise of the current sensing resistor 22, prevents accelerated solder joint aging due to heat accumulation, and ensures the long-term reliability of the system.

[0062] In this embodiment, after the solder fills the gap, the thickness of the resulting solder layer is much greater than the thickness of the copper foil traces on the circuit board 21 (i.e., the thickness of the first pad area 212 and the second pad area 213). Therefore, the current-carrying cross-sectional area of ​​the solder layer is much larger than that of the copper foil traces. Since the solder layer and the copper foil traces on the circuit board 21 form a parallel path electrically, according to the current distribution principle, the solder layer path with lower impedance will carry most of the main current, while the copper foil traces will only carry a small portion of the current. Therefore, the large current mainly flows through the solder layer between the conductive sheet and the current sensing resistor 22, with only a small portion flowing through the copper foil traces on the circuit board 21. This eliminates the risk of the copper foil on the circuit board 21 overheating and burning due to the large current, further improving the reliability of the system.

[0063] In one alternative embodiment, the thickness of the conductive sheet can be the same as the thickness of the current sensing resistor 22 terminal. In another embodiment, the thickness of the conductive sheet is greater than the thickness of the current sensing resistor 22 terminal. In this example, after the conductive sheet and the current sensing resistor 22 are mounted on the circuit board 21, there is a height difference between the conductive sheet and the current sensing resistor 22. After the solder layer is formed and the solder fills the gap, this height difference is filled by the solder, thereby increasing the height of the solder layer. This further increases the current-carrying cross-sectional area of ​​the solder layer.

[0064] In step S30, solder fills the gap 25 using a wave soldering process. Wave soldering allows solder to simultaneously cover the overlapping areas of multiple current-sensing resistors 22 and conductive sheets, achieving large-area one-time soldering. Furthermore, since the conductive sheet side in this embodiment is an open soldering position, it can be completed using standard wave soldering equipment without requiring any modification to the equipment.

[0065] It should also be noted that wave soldering can reduce microscopic defects such as porosity and microcracks generated during the soldering process, thereby further reducing contact resistance.

[0066] Specifically, the circuit board 21 with the conductive sheet fixed thereon is placed in a wave soldering fixture, with the terminals of the current sensing resistor 22 and the side of the conductive sheet facing downwards so that it can contact the solder waves of the wave soldering. The circuit board 21 is fed into the wave soldering equipment, and the preheating temperature of the wave soldering process is set to 140℃~160℃, the overall temperature rise slope is ≤3℃ / second, the soldering zone temperature is 270℃~280℃, and the chain conveyor speed is 800mm / min~900mm / min. During the wave soldering process, the solder, under the impact of the solder waves, fully fills the gap 25 between the conductive sheet and the terminals of the current sensing resistor 22, and covers the terminal pads of the current sensing resistor 22 and the side of the conductive sheet. After the wave soldering is completed, the solder fills the gap 25 completely without gaps, and the conductive sheet and the terminals of the current sensing resistor 22 are completely soldered together.

[0067] In an alternative embodiment, to ensure a high yield rate, the bonding method further includes the following steps: placing the product welded in step S30 into a test fixture, making electrical contact between the output probe of the current source and the first conductive sheet 23 and the second conductive sheet 24 on the circuit board 21, respectively, and setting the current source output to 50A / 1V; turning on the current source and using a voltage measuring instrument to detect the voltage difference between preset test points across the current sensing resistor 22; if the voltage difference value is within the range of 1.9mV to 1.94mV, it indicates that the welding between the current sensing resistor 22 and the conductive sheet is good, its contact impedance meets the usage requirements, and accurate measurement of large currents can be achieved.

[0068] The above description, in conjunction with specific / preferred embodiments, provides a further detailed explanation of the present invention, but it should not be construed as limiting the specific implementation of the invention to these descriptions. Those skilled in the art will recognize that various modifications and improvements can be made without departing from the concept of the present invention, and all such modifications and improvements fall within the scope of protection of the present invention.

Claims

1. A method for connecting a current-sensing resistor to a conductive sheet, characterized in that, The overlapping method includes the following steps: S10: Provide a circuit board and a current sensing resistor, and mount and fix the current sensing resistor in a designated area on the front side of the circuit board; S20: Provide a conductive sheet, the conductive sheet including a first conductive sheet and a second conductive sheet, the first conductive sheet and the second conductive sheet are respectively placed outside the first terminal and the second terminal of the current sensing resistor, and fixed on the circuit board, wherein there is a gap between the first conductive sheet and the first terminal and between the second conductive sheet and the second terminal; S30: The gap is filled with molten solder, so that the first conductive sheet is welded to the first terminal and the second conductive sheet is welded to the second terminal. After the solder solidifies, a solder layer is formed. The first conductive sheet, the second conductive sheet and the current sensing resistor form a conductive path through the solder layer.

2. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, The conductive sheet has a plating layer, and the plating layer is made of the same material as the solder.

3. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 2, characterized in that, In step S30, the solder fills the gap using a wave soldering process.

4. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 3, characterized in that, The preheating temperature of the wave soldering process is 140℃~160℃, the overall temperature rise slope is ≤3℃ / second, the welding zone temperature is 270℃~280℃, and the chain conveying speed is 800mm / min~900mm / min.

5. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, Step S10 specifically includes: S11: Print an adhesive layer in a designated area on the circuit board; S12: Attach the current-sensing resistor onto the adhesive layer; S13: The adhesive layer is cured by reflow soldering to fix the current sensing resistor on the circuit board.

6. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, In step S10, there are several current sensing resistors, which are mounted and fixed in parallel within a designated area of ​​the circuit board.

7. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 6, characterized in that, There is a spacing of 0.3mm-0.4mm between two adjacent current sensing resistors.

8. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, Step S10 further includes: attaching and fixing a thermistor on the back of the circuit board at a position corresponding to the designated area, the thermistor being used to detect the temperature of the current sensing resistor.

9. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, The current sensing resistor is a manganese copper alloy current sensing resistor.

10. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, Step S20 specifically includes: The first conductive sheet and the second conductive sheet are respectively positioned on the circuit board to define the gap; A locking structure is used to lock the first conductive sheet and the second conductive sheet onto the circuit board.

11. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, The solder is tin; in step S20, the gap is 0.7mm-0.9mm.

12. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 1, characterized in that, The circuit board is provided with a first solder pad area and a second solder pad area. The first conductive sheet has a first soldering part for soldering to a first terminal, and the second conductive sheet has a second soldering part for soldering to a second terminal. In step S20, the first terminal and the first solder joint are both located in the first solder pad area, and the second terminal and the second solder joint are both located in the second solder pad area. In step S30, the solder fills the gap while covering the first pad area and the second pad area.

13. The method for connecting the current-sensing resistor and the conductive sheet as described in claim 12, characterized in that, In step S20, when the first soldering part and the second soldering part are respectively fixed on the first solder pad area and the second solder pad area, the first solder pad area has a first solder extension area that does not overlap with the first soldering part, and the second solder pad area has a second solder extension area that does not overlap with the second soldering part; when projected in the thickness direction of the circuit board, the first solder extension area and the second solder extension area respectively surround the periphery of the first soldering part and the second soldering part.

14. A current sampling module, characterized in that, It is manufactured using the overlapping method of the current sensing resistor and the conductive sheet as described in any one of claims 1 to 13.

15. The current sampling module as described in claim 14, characterized in that, A foolproof structure is provided between the first conductive sheet, the second conductive sheet and the circuit board.

16. The current sampling module as described in claim 15, characterized in that, At least two positioning structures are provided between the first conductive sheet and the circuit board, and between the second conductive sheet and the circuit board, respectively. The positioning structure includes a positioning hole provided on one of the conductive sheet and the circuit board, and a positioning post provided on the other. The positioning structure between the first conductive sheet and the circuit board and the positioning structure between the second conductive sheet and the circuit board are at least partially misaligned to form the foolproof structure.

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