High-efficiency welding structure of lithium battery pack and preparation method thereof

Abstract

This invention provides a high-efficiency welding structure for lithium battery packs, including a cell array, a PCB motherboard, and a protection board unit. The PCB motherboard has cell positioning through-holes for inserting cells into modules. Annular power pads at both ends of the through-holes are used for welding to the cells. A pre-fabricated main power copper foil circuit within the board enables series and parallel connection of the cells. A single-string voltage acquisition trace is also pre-fabricated, converging to a 9-pin female connector on the board. The female connector is connected to the protection board via a male connector, achieving transmission without a separate acquisition harness. This invention frees up internal space in the battery pack, increases volumetric energy density, eliminates the risk of short circuits due to harness wear, eliminates the need for additional insulation protection structures, further simplifies assembly processes, and eliminates manual harness welding, significantly improving efficiency and reducing costs, while enhancing product reliability and ease of operation and maintenance.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a high-efficiency welding structure for lithium battery packs and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, lithium-ion batteries, with their advantages of high energy density, long cycle life, and low self-discharge rate, have been widely used in many fields such as power tools, two-wheeled electric vehicles, small energy storage devices, home photovoltaic energy storage, and AGV industrial vehicles. Among them, cylindrical power lithium batteries have become the mainstream choice for small and medium power lithium battery packs due to their high degree of standardization, good cell consistency, flexible series and parallel combination, and high safety redundancy. In the manufacturing process of cylindrical lithium battery packs, the series and parallel welding of cells and the single-string voltage acquisition signal transmission are core processes, and their process solutions directly determine the production efficiency, manufacturing cost, and long-term reliability of the lithium battery pack.

[0003] Currently, the industry commonly uses a distributed harness acquisition scheme for series-parallel welding and voltage acquisition of cylindrical lithium battery packs. Its core structure and process flow are as follows: First, multiple individual battery cells are arranged and fixed according to a preset series-parallel ratio. The positive and negative electrodes of the cells are then laser-welded or resistance-welded using nickel sheets or metal busbars to complete the series-parallel electrical connection of the cells, forming a battery module. Subsequently, a corresponding number of independent voltage acquisition harnesses are used according to the number of battery strings. Each acquisition harness is manually welded, with one end attached to the busbar of the corresponding battery string and the other end attached to the acquisition terminal of the battery protection board (BMS), ultimately achieving the acquisition and transmission of voltage signals for a single battery string. Existing technologies also have some improved solutions, such as pre-crimping the acquisition harnesses to terminals and then plugging them into the busbars. However, this still requires manual arrangement of the harnesses, terminal insertion, and fixing, and does not fundamentally change the core architecture of the distributed harness acquisition scheme.

[0004] Therefore, existing general solutions have the following technical problems in mass production applications: 1. Low production efficiency, making it difficult to adapt to large-scale mass production: The main circuit of battery cell series and parallel connection and the voltage acquisition circuit are separated. The acquisition harness requires multiple manual processes, which account for a high proportion of labor time. It is impossible to achieve fully automated continuous production, and the capacity increase is severely limited.

[0005] 2. High overall manufacturing costs: The welding of wire harnesses requires professionally certified welders, resulting in high labor costs; additional materials such as wire harnesses, terminals, and insulation accessories need to be purchased, and the rework costs caused by the high defect rate of manual welding result in high overall manufacturing costs.

[0006] 3. Poor product reliability and safety hazards: The defect rate of manually welded data acquisition lines is generally ≥5% in the industry, and problems such as false welding, incorrect welding, and missing welding are prone to occur. At best, it will cause abnormal voltage acquisition and malfunction of the protection board. At worst, it will lead to safety accidents such as overcharging and over-discharging of the battery cells and thermal runaway. Flexible wire harnesses are prone to falling off due to vibration after long-term use, and batch consistency and long-term reliability cannot be guaranteed.

[0007] 4. High difficulty in operation and maintenance: Welding operation has a high professional threshold and the training period for personnel is long; there is no standardized universal design for the acquisition wire harness, and the interchangeability of different specifications of products is poor; after-sales service requires troubleshooting each wire harness individually, and the maintenance operation is complicated and costly.

[0008] 5. Insufficient space utilization and insulation safety: A large number of scattered wire harnesses occupy the internal space of the battery pack, reducing the volumetric energy density; the wire harnesses are prone to wear and tear, which can cause short circuits, requiring additional insulation protection structures, further increasing assembly costs and processes.

[0009] In summary, developing a high-efficiency welding structure for lithium battery packs that can eliminate the manual welding and acquisition of wire harnesses, significantly improve production efficiency, reduce manufacturing costs, and enhance product reliability has become an urgent need in the industry. Summary of the Invention

[0010] In view of this, the present invention provides a high-efficiency welding structure for lithium battery packs and a method for preparing the same. The technical solution of the present invention is as follows: A high-efficiency welding structure for lithium battery packs includes a cell array, a PCB motherboard, and a protection board unit, characterized in that: The PCB motherboard has cell positioning through holes that correspond one-to-one with each individual cell in the cell array. Each individual cell is vertically inserted into the cell positioning through hole to form a battery module. On the PCB motherboard, annular power pads are provided at both ends of the axial direction of each cell positioning through hole. The positive and negative poles of the inserted individual cell are respectively bonded to the corresponding annular power pads. The PCB motherboard has a pre-fabricated main power copper foil circuit. Each individual cell is electrically connected in a preset series-parallel relationship through the main power copper foil circuit. The PCB motherboard also has multiple single-string voltage acquisition copper foil traces prefabricated inside, which match the number of battery module strings. The first end of each single-string voltage acquisition copper foil trace is electrically connected to the ring power pad corresponding to the corresponding battery cell. The ends of each single-string voltage acquisition copper foil trace are gathered and electrically connected to the signal pins of the 9-pin female connector. The 9-pin female connector is fixedly soldered to the surface of the PCB motherboard. The 9PIN female connector is connected to the acquisition interface of the protection board unit via a matching 9PIN male ribbon cable, enabling the transmission of a single string voltage signal from the battery module from the PCB motherboard to the protection board unit without an independent acquisition harness.

[0011] In this invention, the main body includes a cell array, a PCB motherboard, and a protection board unit, which together constitute a complete electrical system of a lithium battery pack. The cell array is the core of energy storage, the PCB motherboard is the core carrier for realizing the series and parallel electrical connection of the cells and the voltage acquisition signal transmission, and the protection board unit is the core control component for realizing the charging and discharging protection of the battery pack and voltage acquisition and monitoring. The three components replace the existing distributed architecture through an integrated design.

[0012] The cell positioning through-holes on the PCB motherboard correspond one-to-one with individual cells, enabling precise self-positioning and rapid assembly of individual cells. Through the clearance fit between the through-holes and the outer diameter of the cell, radial positioning is achieved upon vertical insertion, eliminating the need for custom-made soldering fixtures. Furthermore, the directional arrangement of the through-holes standardizes the polarity and series / parallel arrangement sequence of the cells, preventing reverse installation and significantly improving the efficiency and accuracy of cell assembly.

[0013] The annular power pads set at both ends of the axial direction of the battery cell positioning through hole can achieve reliable welding and bonding between the battery cell electrode surface and the PCB motherboard. The annular structure can completely wrap the welding area of ​​the battery cell electrode surface, ensuring maximum welding contact area and reducing contact internal resistance. After the positive and negative electrode surfaces of the battery cell are welded to the corresponding pads after insertion, the electrical connection of the battery cell in the preset series and parallel relationship can be directly realized through the main power copper foil circuit pre-fabricated in the PCB motherboard. This replaces the independent nickel sheet / bus structure of the existing technology, integrates the main power circuit inside the PCB motherboard, and realizes the integrated and standardized design of the battery cell series and parallel structure.

[0014] The pre-fabricated single-string voltage acquisition copper foil traces within the PCB motherboard replace the independent acquisition wire harnesses of existing technologies, enabling in-board insulated transmission of single-string voltage signals. The first end of the trace is directly connected to the ring power pad of the corresponding string cell, allowing direct pickup of the voltage signal of the corresponding string cell. The last end is connected to the signal pin of the 9-pin female connector, achieving centralized and standardized output of multiple string voltage acquisition signals. All acquisition traces are prefabricated during the PCB production stage, eliminating the need for subsequent manual soldering and wiring.

[0015] The 9PIN female connector connects to the acquisition interface of the protection board unit via a matching 9PIN male ribbon cable, achieving standardized signal conversion. All single-string voltage signals can be transmitted from the PCB motherboard to the protection board unit simply by plugging in the connector, truly realizing signal transmission without independent acquisition cable harnesses and completely eliminating the manual soldering process for acquisition cables.

[0016] Furthermore, the PCB motherboard is made of UL94V0 flame-retardant FR-4 fiberglass board, the copper thickness of the main power copper foil circuit is ≥2 ounces, the copper thickness of the single-string voltage acquisition copper foil trace is ≥1 ounce, and the surface of the PCB motherboard pads is treated with immersion gold process.

[0017] In this invention, the PCB motherboard uses UL94V0 flame-retardant FR-4 fiberglass board. This substrate has excellent insulation, mechanical strength, and flame-retardant properties, which can meet the safety requirements of battery packs. The copper thickness of the main power copper foil circuit is ≥2 ounces, which can ensure that the main power circuit has sufficient overcurrent capacity and reduce temperature rise and power consumption during high-current charging and discharging. The copper thickness of the single-string voltage acquisition copper foil trace is ≥1 ounce, which can ensure the stability of the acquisition signal transmission and reduce signal attenuation. The surface of the PCB motherboard pads is treated with immersion gold, which can improve the oxidation resistance and welding reliability of the pads, avoid the problem of cold solder joints caused by pad oxidation, and ensure the long-term stability of cell welding and connector welding.

[0018] Furthermore, the annular power pad and the electrode surface of the individual cell are connected by laser ring welding to form a continuous closed welding fusion layer; the main power copper foil circuit includes parallel unit traces and series unit traces. The positive and negative annular power pads of multiple individual cells in the same parallel group are electrically connected through parallel unit traces. Multiple groups of parallel units are electrically connected sequentially through series unit traces to form a series circuit with a preset number of series.

[0019] In this invention, a continuous closed welding fusion layer is formed between the annular power pad and the electrode surface of the individual cell through laser ring welding. This ensures a reliable circumferential electrical connection between the cell electrode surface and the pad, avoiding excessive contact resistance and overheating caused by localized poor soldering. The main power copper foil circuit is divided into parallel unit traces and series unit traces. The parallel unit traces are used to connect multiple cells in the same group in parallel, improving the capacity and discharge capability of the battery pack. The series unit traces are used to connect multiple groups of parallel cells in series, improving the rated voltage of the battery pack. Through the two types of traces pre-fabricated on the board, different series and parallel battery pack designs can be flexibly adapted. No external hardware structure needs to be adjusted; only the PCB layout needs to be modified to complete the product changeover.

[0020] Furthermore, each of the single-string voltage acquisition copper foil traces has a safety insulation gap reserved between it and the main power copper foil circuit inside the PCB motherboard; the PCB motherboard has a foolproof positioning hole that matches the positioning post of the 9PIN female connector, and the 9PIN female connector is oriented and installed through the positioning post and the foolproof positioning hole, and its pins from 1 to 9 are defined as the total negative terminal B- of the battery module, the positive terminals B1-B7 of the first to seventh strings of cells, and the total positive terminal B+ of the battery module.

[0021] In this invention, a safety insulation gap is reserved between the single-string voltage acquisition copper foil trace and the main power copper foil circuit. The core function is to avoid electromagnetic interference from the large current of the main power circuit on the acquired signal, while ensuring the insulation safety between the high and low voltage circuits and avoiding the risk of short circuit. The foolproof positioning hole on the PCB motherboard matches the positioning post of the 9PIN female connector, which can realize the directional installation of the 9PIN female connector and avoid the signal reversal problem caused by the female connector being installed backwards. The 9PIN female connector pins are standardized and can be adapted to the industry-standard 7-string lithium battery protection board acquisition interface, realizing the standardized and universal design of the connector, ensuring the complete interchangeability of products of the same specification, and avoiding the risk of reverse connection during insertion.

[0022] Furthermore, the PCB motherboard is provided with a total positive power pad and a total negative power pad that are electrically connected to the total positive and total negative terminals of the main power copper foil circuit, respectively. The total positive power pad and the total negative power pad are electrically connected to the power circuit of the protection board unit through copper pillars or power cables.

[0023] In this invention, the total positive power pad and the total negative power pad on the PCB motherboard are the core nodes for the total power output of the battery pack. They are electrically connected to the total positive and total negative terminals of the main power copper foil circuit, respectively, and can directly output the total voltage and charging / discharging current of the battery pack. The two power pads are electrically connected to the corresponding power circuit of the protection board unit through copper pillars or power cables, which can realize the on / off control of the charging / discharging circuit of the battery pack and the overcurrent, overvoltage, and undervoltage protection of the protection board unit, forming a complete battery protection system. At the same time, this connection method can flexibly adapt to protection boards of different specifications without modifying the main structure of the PCB motherboard.

[0024] Through extensive inventive experimentation, the inventors of this application have creatively adopted a wireless acquisition architecture of "integrated acquisition circuit within the PCB motherboard + centralized 9-pin standardized female connector." All single-string voltage acquisition traces are prefabricated inside the PCB motherboard, and the acquisition link is optimized to "cell electrode surface → PCB ring power pad → in-board insulating copper foil trace → 9-pin female connector → standardized finished cable plug-in protection board," eliminating all independent acquisition wire bundles and fundamentally eliminating the manual soldering process for acquisition wires. Simultaneously, this invention integrates the main power series-parallel circuit and the single-string voltage acquisition circuit onto the same PCB motherboard, simultaneously achieving the series-parallel electrical connection of the cells and the voltage acquisition signal transmission through in-board wiring. A single laser soldering of the ring power pads at both ends of the cell and the PCB board simultaneously enables the main power circuit to conduct and the acquisition point to conduct, solving the problem of separate soldering of two structures and redundant processes in existing technologies.

[0025] In addition, this invention uses an industry-standard 9PIN female connector to centrally transfer the acquired signals, with pre-defined and standardized pin definitions and a foolproof positioning hole design on the PCB board to completely eliminate the risk of reverse connection; at the same time, it uses standardized finished cable plug-in connection, which does not require any on-site soldering, and can be used immediately. Different batches and products of the same specifications are completely interchangeable.

[0026] This invention also provides a method for preparing a high-efficiency welding structure for lithium battery packs, characterized by comprising the following steps: S1. PCB motherboard prefabrication: Based on the series and parallel number of the battery module and the specifications of the battery cells, complete the layout design of the PCB motherboard, and simultaneously complete the integrated wiring of the main power copper foil circuit and the single-string voltage acquisition copper foil trace; after the PCB motherboard is manufactured, the 9-pin female connector is mounted and soldered to the corresponding pads of the PCB motherboard. After continuity testing, it is confirmed that there are no open circuits or short circuits in the circuits inside the board, and the prefabricated PCB motherboard is obtained. S2. Cell pre-assembly: After sorting individual cells for consistency and cleaning the electrode surfaces, according to the polarity markings on the PCB motherboard, the individual cells are vertically inserted into the cell positioning through holes on the PCB motherboard one by one, so that the positive and negative electrode surfaces of the cells are in contact with the corresponding annular power pads, thus completing the pre-assembly of the battery module. S3. Integrated welding: The pre-assembled battery module is fixed to the welding fixture. The laser welding process is used to perform ring welding on the annular power pads at both ends of the PCB motherboard and the corresponding electrode surface of the battery cell. The series and parallel electrical connection between the battery cell and the main power copper foil circuit is completed in one step. At the same time, the conduction of each single string voltage acquisition copper foil trace and the corresponding battery cell is realized simultaneously. There is no independent acquisition wire harness welding process throughout the process. S4. Protection board docking: Prefabricate a finished ribbon cable with a 9-pin male connector, plug one end of the ribbon cable into the acquisition interface of the protection board unit, and plug the other end into the 9-pin female connector on the PCB motherboard. At the same time, connect the positive and negative terminals of the PCB motherboard to the power circuit of the protection board unit to complete the electrical assembly. S5. Packaging and Testing: Perform functional tests on the battery modules completed by the electrical assembly. After passing the tests, package them into a flame-retardant shell and put them into storage after completing the final inspection of the finished product.

[0027] The preparation method of this invention is fully adaptable to automated mass production. The main power circuit and the acquisition circuit are integrated and wired in advance through the PCB motherboard prefabrication stage. Subsequent processes do not require any welding of acquisition wire harnesses, completely eliminating the dependence on manual welding. Each step is linked to the next, forming a complete standardized production process.

[0028] Furthermore, in step S1, the 9PIN female connector is mounted by an SMT placement machine and then soldered and fixed by reflow soldering. The peak temperature of the reflow soldering is 245±5℃, and the holding time in the constant temperature zone is 60s-90s. After soldering, an ICT continuity test is performed.

[0029] In this invention, the 9-pin female connector is mounted using an SMT placement machine, which enables standardized control of mounting accuracy and avoids positional deviations caused by manual mounting. The peak reflow soldering temperature is controlled at 245±5℃, and the constant temperature zone is maintained for 60s-90s. These process parameters ensure full solder fusion while preventing high-temperature damage to the PCB motherboard and connectors. After soldering, the solder climb height of the 9-pin female connector pins meets the standard, resulting in excellent soldering reliability. After soldering, an ICT continuity test is performed to accurately detect open and short circuit defects in the circuitry within the board, ensuring that the electrical performance of each prefabricated PCB motherboard is qualified.

[0030] Furthermore, in step S2, the standard for cell consistency sorting is that the voltage difference of individual cells in the same batch is ≤5mV and the internal resistance difference is ≤2mΩ; after the individual cells are inserted, they achieve self-positioning through the cell positioning through hole, without the need for additional auxiliary clamps for fixation.

[0031] In this invention, the cell consistency sorting adopts the standard of voltage difference ≤5mV and internal resistance difference ≤2mΩ, which can ensure that the voltage and internal resistance performance of cells in the same batch are highly matched, avoid the problem of overcharging and over-discharging of single cells during battery pack use, and improve the cycle life and safety of battery pack use. After the cells are inserted, they are self-positioned through the cell positioning through holes, without the need for additional auxiliary fixtures, which can significantly reduce tooling costs and improve the efficiency of cell insertion, enabling rapid pre-assembly of single modules.

[0032] Furthermore, in step S3, the laser welding is performed using a fiber laser welding machine with process parameters of laser power 150W-300W and welding speed 30mm / s-50mm / s; after welding is completed, the internal resistance test of the main power circuit and the continuity test of the single-string voltage acquisition trace are performed simultaneously.

[0033] In this invention, a fiber laser welding machine is used for laser welding, equipped with a laser power of 150W-300W and a welding speed of 30mm / s-50mm / s. These process parameters ensure that the welding penetration reaches the standard while avoiding damage to the battery cell due to excessive laser power. After welding, a continuous closed weld bead is formed, free from defects such as incomplete welding, explosion points, and missing welds. After welding, the internal resistance test of the main power circuit and the continuity test of the single-string voltage acquisition line are performed simultaneously, which can detect welding defects in real time, remove defective products, and ensure batch consistency of welding quality.

[0034] Furthermore, in step S4, the finished ribbon cable with the 9-pin male connector is a standardized prefabricated component, which is matched with the 9-pin female connector and the protection board acquisition interface in a foolproof manner, and the insertion process does not require manual soldering. In step S5, the functional tests include single-string voltage acquisition accuracy test, charge and discharge protection function test, and insulation withstand voltage test.

[0035] In this invention, the finished ribbon cable with a 9-pin male connector is a standardized prefabricated component, which is matched with the 9-pin female connector and the protection board acquisition interface in a foolproof manner, completely eliminating the risk of incorrect insertion. The insertion process does not require manual soldering, which greatly shortens the single module docking time. The functional test in step S5 covers single string voltage acquisition accuracy test, charge and discharge protection function test, and insulation withstand voltage test, which can comprehensively verify the acquisition performance, protection performance and safety performance of the battery pack, ensuring that the products leaving the factory meet the usage requirements.

[0036] This invention employs a full PCB hard-connection design, completely eliminating the inherent defects of traditional wire harnesses, such as susceptibility to vibration and pulling, and poor contact. It ensures stable signal transmission and strong anti-interference capabilities. The number of manually soldered joints is significantly reduced, fundamentally lowering the risk of poor soldering, incorrect soldering, and missing solder joints, resulting in a product defect rate that is orders of magnitude lower than traditional solutions. All electrical connections and data acquisition traces are prefabricated during the PCB production stage, unaffected by individual differences in manual operation, ensuring excellent consistency in circuit resistance and data acquisition accuracy within the same batch of products. The use of standardized flame-retardant substrate and insulation spacing design, combined with a battery cell insulation protection structure, eliminates the short-circuit safety hazards caused by the messy arrangement of traditional wire harnesses. It also integrates overcurrent protection and temperature acquisition functions to improve the safety protection system.

[0037] This invention adopts fully automated production. The PCB motherboard is prefabricated using standardized SMT assembly and reflow soldering. The battery cell insertion can be completed by an automated insertion machine. The welding uses a fiber laser machine for fully automated circumferential welding. There are no core processes that must be completed manually, completely eliminating the dependence on professional welders and enabling fully automated, large-scale mass production.

[0038] The beneficial effects of this invention are as follows: 1. Production efficiency is greatly improved; the manual wire harness-related processes are eliminated, reducing the production time of a single module and increasing the unit capacity of a single line, enabling rapid mass production. 2. Significantly reduced overall manufacturing costs: No professional welding personnel are required, the proportion of manual labor hours is greatly reduced, and the labor cost per module is significantly reduced; a large number of wire harness-related auxiliary materials such as acquisition wire harnesses, wiring terminals, and heat shrink tubing are eliminated, resulting in a significant reduction in overall material costs, while the product defect rate is also greatly reduced.

[0039] 3. Effectively ensure product reliability and consistency: The full PCB hard connection design eliminates the defects of traditional wire harness detachment and poor contact, and the acquisition signal is stable; it greatly reduces manual soldering points, significantly reducing the risk of poor soldering and product defect rate; the pre-fabricated wiring in the board ensures excellent batch consistency; the standardized insulation and flame retardant design eliminates the hidden danger of wire harness short circuits, improves product safety, and solves the core pain points of poor reliability and high safety risks of existing technologies.

[0040] 4. Improved ease of operation and maintenance: No welding is required throughout the process, which greatly reduces the difficulty and cost of maintenance and solves the problems of high operating threshold and difficult after-sales maintenance of existing technologies.

[0041] 5. Enhanced space utilization and insulation safety: The structure design without distributed acquisition harnesses frees up installation space inside the battery pack, optimizes the cell layout, and significantly improves the volumetric energy density of the battery pack. At the same time, it eliminates the risk of short circuits caused by harness wear and tear at the source, eliminating the need for additional insulation protection structures, further simplifying the assembly process and reducing the cost of supporting materials. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a structure according to an embodiment of the present invention. Detailed Implementation

[0043] The technical solutions will now be clearly and completely described in conjunction with embodiments of the present invention. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example 1

[0044] A high-efficiency welding structure for lithium battery packs includes a cell array, a PCB motherboard, and a protection board unit, characterized in that: The PCB motherboard has cell positioning through holes that correspond one-to-one with each individual cell in the cell array. Each individual cell is vertically inserted into the cell positioning through hole to form a battery module. On the PCB motherboard, annular power pads are provided at both ends of the axial direction of each cell positioning through hole. The positive and negative poles of the inserted individual cell are respectively bonded to the corresponding annular power pads. The PCB motherboard has a pre-fabricated main power copper foil circuit. Each individual cell is electrically connected in a preset series-parallel relationship through the main power copper foil circuit. The PCB motherboard also has multiple single-string voltage acquisition copper foil traces prefabricated inside, which match the number of battery module strings. The first end of each single-string voltage acquisition copper foil trace is electrically connected to the ring power pad corresponding to the corresponding battery cell. The ends of each single-string voltage acquisition copper foil trace are gathered and electrically connected to the signal pins of the 9-pin female connector. The 9-pin female connector is fixedly soldered to the surface of the PCB motherboard. The 9PIN female connector is connected to the acquisition interface of the protection board unit via a matching 9PIN male ribbon cable, enabling the transmission of a single string voltage signal from the battery module from the PCB motherboard to the protection board unit without an independent acquisition harness.

[0045] Furthermore, the PCB motherboard is made of UL94V0 flame-retardant FR-4 fiberglass board, the copper thickness of the main power copper foil circuit is ≥2 ounces, the copper thickness of the single-string voltage acquisition copper foil trace is ≥1 ounce, and the surface of the PCB motherboard pads is treated with immersion gold process.

[0046] Furthermore, the annular power pad and the electrode surface of the individual cell are connected by laser ring welding to form a continuous closed welding fusion layer; the main power copper foil circuit includes parallel unit traces and series unit traces. The positive and negative annular power pads of multiple individual cells in the same parallel group are electrically connected through parallel unit traces. Multiple groups of parallel units are electrically connected sequentially through series unit traces to form a series circuit with a preset number of series.

[0047] Furthermore, each of the single-string voltage acquisition copper foil traces has a safety insulation gap reserved between it and the main power copper foil circuit inside the PCB motherboard; the PCB motherboard has a foolproof positioning hole that matches the positioning post of the 9PIN female connector, and the 9PIN female connector is oriented and installed through the positioning post and the foolproof positioning hole, and its pins from 1 to 9 are defined as the total negative terminal B- of the battery module, the positive terminals B1-B7 of the first to seventh strings of cells, and the total positive terminal B+ of the battery module.

[0048] Furthermore, the PCB motherboard is provided with a total positive power pad and a total negative power pad that are electrically connected to the total positive and total negative terminals of the main power copper foil circuit, respectively. The total positive power pad and the total negative power pad are electrically connected to the power circuit of the protection board unit through copper pillars or power cables. Example 2

[0049] A method for fabricating a high-efficiency welding structure for a lithium battery pack, characterized by comprising the following steps: S1. PCB motherboard prefabrication: Based on the series and parallel number of the battery module and the specifications of the battery cells, complete the layout design of the PCB motherboard, and simultaneously complete the integrated wiring of the main power copper foil circuit and the single-string voltage acquisition copper foil trace; after the PCB motherboard is manufactured, the 9-pin female connector is mounted and soldered to the corresponding pads of the PCB motherboard. After continuity testing, it is confirmed that there are no open circuits or short circuits in the circuits inside the board, and the prefabricated PCB motherboard is obtained. S2. Cell pre-assembly: After sorting individual cells for consistency and cleaning the electrode surfaces, according to the polarity markings on the PCB motherboard, the individual cells are vertically inserted into the cell positioning through holes on the PCB motherboard one by one, so that the positive and negative electrode surfaces of the cells are in contact with the corresponding annular power pads, thus completing the pre-assembly of the battery module. S3. Integrated welding: The pre-assembled battery module is fixed to the welding fixture. The laser welding process is used to perform ring welding on the annular power pads at both ends of the PCB motherboard and the corresponding electrode surface of the battery cell. The series and parallel electrical connection between the battery cell and the main power copper foil circuit is completed in one step. At the same time, the conduction of each single string voltage acquisition copper foil trace and the corresponding battery cell is realized simultaneously. There is no independent acquisition wire harness welding process throughout the process. S4. Protection board docking: Prefabricate a finished ribbon cable with a 9-pin male connector, plug one end of the ribbon cable into the acquisition interface of the protection board unit, and plug the other end into the 9-pin female connector on the PCB motherboard. At the same time, connect the positive and negative terminals of the PCB motherboard to the power circuit of the protection board unit to complete the electrical assembly. S5. Packaging and Testing: Perform functional tests on the battery modules completed by the electrical assembly. After passing the tests, package them into a flame-retardant shell and put them into storage after completing the final inspection of the finished product.

[0050] Furthermore, in step S1, the 9PIN female connector is mounted by an SMT placement machine and then soldered and fixed by reflow soldering. The peak temperature of the reflow soldering is 245±5℃, and the holding time in the constant temperature zone is 60s-90s. After soldering, an ICT continuity test is performed.

[0051] Furthermore, in step S2, the standard for cell consistency sorting is that the voltage difference of individual cells in the same batch is ≤5mV and the internal resistance difference is ≤2mΩ; after the individual cells are inserted, they achieve self-positioning through the cell positioning through hole, without the need for additional auxiliary clamps for fixation.

[0052] Furthermore, in step S3, the laser welding is performed using a fiber laser welding machine with process parameters of laser power 150W-300W and welding speed 30mm / s-50mm / s; after welding is completed, the internal resistance test of the main power circuit and the continuity test of the single-string voltage acquisition trace are performed simultaneously.

[0053] Furthermore, in step S4, the finished ribbon cable with the 9-pin male connector is a standardized prefabricated component, which is matched with the 9-pin female connector and the protection board acquisition interface in a foolproof manner, and the insertion process does not require manual soldering. In step S5, the functional tests include single-string voltage acquisition accuracy test, charge and discharge protection function test, and insulation withstand voltage test. Example 3

[0054] A high-efficiency welding structure for lithium battery packs includes a cell array, a PCB motherboard, and a protection board unit, characterized in that: The PCB motherboard has cell positioning through holes that correspond one-to-one with each individual cell in the cell array. Each individual cell is vertically inserted into the cell positioning through hole to form a battery module. On the PCB motherboard, annular power pads are provided at both ends of the axial direction of each cell positioning through hole. The positive and negative poles of the inserted individual cell are respectively bonded to the corresponding annular power pads. The PCB motherboard has a pre-fabricated main power copper foil circuit. Each individual cell is electrically connected in a preset series-parallel relationship through the main power copper foil circuit. The PCB motherboard also has multiple single-string voltage acquisition copper foil traces prefabricated inside, which match the number of battery module strings. The first end of each single-string voltage acquisition copper foil trace is electrically connected to the ring power pad corresponding to the corresponding battery cell. The ends of each single-string voltage acquisition copper foil trace are gathered and electrically connected to the signal pins of the 9-pin female connector. The 9-pin female connector is fixedly soldered to the surface of the PCB motherboard. The 9PIN female connector is connected to the acquisition interface of the protection board unit via a matching 9PIN male ribbon cable, enabling the transmission of a single string voltage signal from the battery module from the PCB motherboard to the protection board unit without an independent acquisition harness.

[0055] Furthermore, the PCB motherboard uses UL94V0 flame-retardant FR-4 double-sided fiberglass board with a thickness of 1.6mm~2.0mm; the copper thickness of the main power copper foil circuit is ≥2 ounces, the copper thickness of the single-string voltage acquisition copper foil trace is ≥1 ounce, and the surface of the PCB motherboard's pads is treated with immersion gold; the diameter of the cell positioning through-hole is 0.1mm larger than the outer diameter of the corresponding individual cell, with a diameter tolerance of ±0.05mm; an insulating gasket is fitted at the contact position between the individual cell and the PCB motherboard, and the insulating gasket is sandwiched between the cell's metal shell and the copper foil of the PCB motherboard; The inner diameter of the annular power pad is 0.2 mm larger than the diameter of the corresponding cell positioning through hole, and the outer diameter of the annular power pad is 2 mm larger than the diameter of the corresponding cell positioning through hole. The annular power pad and the electrode surface of the individual cell are connected by laser ring welding to form a continuous closed welding fusion layer, and the welding fusion layer has a penetration depth ≥ 0.2 mm. The main power copper foil circuit includes parallel unit traces and series unit traces. The positive and negative annular power pads of multiple individual cells in the same parallel group are electrically connected through parallel unit traces. Multiple groups of parallel units are electrically connected sequentially through series unit traces to form a series circuit with a preset number of series.

[0056] Furthermore, each of the single-string voltage acquisition copper foil traces has a safety insulation gap of ≥0.5mm between it and the main power copper foil circuit inside the PCB motherboard; the line width of each single-string voltage acquisition copper foil trace is ≥0.3mm; and the insulation gap between adjacent acquisition traces is ≥0.2mm. The 9-pin female connector uses a through-hole type with a pin pitch of 2.54mm or 3.96mm, a rated voltage of ≥300V, a rated current of ≥5A, and a contact resistance of ≤20mΩ. The pins of the 9-pin female connector, from 1 to 9, are defined as follows: battery module total... The battery module consists of the following components: negative electrode B-, positive electrode B1 of the first battery cell, positive electrode B2 of the second battery cell, positive electrode B3 of the third battery cell, positive electrode B4 of the fourth battery cell, positive electrode B5 of the fifth battery cell, positive electrode B6 of the sixth battery cell, positive electrode B7 of the seventh battery cell, and the overall positive electrode B+ of the battery module. The PCB motherboard has anti-foolproof positioning holes that match the positioning posts of the 9-pin female connector. The 9-pin female connector is oriented and installed by the cooperation of the positioning posts and anti-foolproof positioning holes. The pins of the 9-pin female connector are fixed to the corresponding pads on the PCB motherboard by a solder fusion layer formed by SMT reflow soldering.

[0057] Furthermore, the PCB motherboard is provided with a total positive power pad and a total negative power pad, which are electrically connected to the total positive and total negative terminals of the main power copper foil circuit, respectively. The total positive power pad and the total negative power pad are electrically connected to the corresponding power circuit of the protection board unit through copper pillars or power cables. The PCB motherboard is also pre-fabricated with an overcurrent fuse pad and an NTC temperature sensor pad. The overcurrent fuse is connected in series on the total positive path of the main power copper foil circuit. The acquisition end of the NTC temperature sensor is attached to the surface of the battery cell. The signal pin of the NTC temperature sensor is electrically connected to the reserved pin of the 9PIN female connector through the traces in the PCB motherboard. It also includes a flame-retardant shell, which is made of UL94V0 grade ABS or PC engineering plastic. The flame-retardant shell has a screwless fixing slot that matches the battery module. The assembled battery module is snapped and fixed in the fixing slot. The flame-retardant shell has openings that correspond to the output interface of the PCB motherboard. Example 4

[0058] A method for fabricating a high-efficiency welding structure for a lithium battery pack, characterized by comprising the following steps: S1. PCB Motherboard Prefabrication: Based on the series and parallel number of the battery module and the specifications of the battery cells, the schematic diagram and layout design of the PCB motherboard are completed. The layout design simultaneously completes the integrated routing of the main power copper foil circuit and the single-string voltage acquisition copper foil trace. After the PCB motherboard is manufactured, the 9-pin female connector is mounted to the corresponding pad on the PCB motherboard using an SMT pick and place machine. The 9-pin female connector is then soldered and fixed by reflow soldering. After soldering, an ICT continuity test is performed to confirm that there are no open circuits or short circuits in the main power circuit and the single-string voltage acquisition copper foil trace within the board, thus obtaining the prefabricated PCB motherboard. S2. Cell Pre-processing and Assembly: Individual cells are sorted by voltage and internal resistance to select those that are consistent and qualified within the same batch. After cleaning the cell electrode surfaces, insulating gaskets are installed at the contact points between the cell and the PCB motherboard. According to the polarity markings on the PCB motherboard, individual cells are vertically inserted into the cell positioning through holes on the PCB motherboard one by one, so that the positive and negative electrode surfaces of the cell are completely attached to the corresponding annular power pads, thus completing the pre-assembly of the battery module. S3. Integrated Series-Parallel Welding: The pre-assembled battery module is fixed to a special welding fixture. Laser welding process is used to perform ring welding on the annular power pads at both ends of the PCB motherboard and the positive and negative electrode surfaces of the corresponding cells. The series-parallel electrical connection between the cells and the main power copper foil circuit of the PCB motherboard is completed in one step. At the same time, the conduction of each single string voltage acquisition copper foil trace and the corresponding cell is realized simultaneously. There is no welding process for independent acquisition wire harnesses throughout the process. S4. Protection board without solder joints: Prefabricated finished ribbon cable with 9-pin male connector, one end of the finished ribbon cable is pre-plugged into the acquisition interface of the protection board unit, the 9-pin male connector of the finished ribbon cable is plugged into the 9-pin female connector on the PCB motherboard, and the total positive and total negative terminals of the PCB motherboard are electrically connected to the power circuit of the protection board unit to complete the electrical assembly of the battery module. S5. Packaging and Finished Product Inspection: Perform full-function testing on the battery modules after the electrical assembly is completed. After passing the test, package the battery modules into a flame-retardant shell, complete the final inspection of the finished product, and put them into storage.

[0059] Furthermore, in step S1, the reflow soldering process parameters are: peak temperature 245±5℃, constant temperature zone holding time 60s-90s, and the solder climb height of the 9PIN female connector pins after soldering is ≥2 / 3 of the pin diameter; in step S2, the cell sorting standard is: voltage difference of individual cells in the same batch ≤5mV, internal resistance difference ≤2mΩ, and the cell electrode surface is cleaned by wiping with a lint-free cloth to remove oil and dust, ensuring that the soldering surface is free of impurities.

[0060] Furthermore, in step S2, after the individual battery cell is vertically inserted into the battery cell positioning through hole, self-positioning is achieved through the gap fit between the through hole and the battery cell, without the need for additional auxiliary fixtures for fixation, and the pre-assembly time of a single module is ≤30s; in step S3, the laser welding adopts a fiber laser welding machine, and the process parameters are: laser power 150W-300W, welding speed 30mm / s-50mm / s, circumferential welding circle number is 1 circle, and the weld point after welding has no defects such as false weld, explosion point, or missing weld.

[0061] Furthermore, in step S3, after laser welding is completed, the battery module is immediately subjected to circuit testing. Simultaneously, the internal resistance test of the main power copper foil circuit and the continuity test of the single-string voltage acquisition copper foil trace are completed to ensure that the internal resistance of the circuit is consistent with ≤5mΩ and that there are no open circuit or short circuit defects in the acquisition trace. In step S4, the finished ribbon cable with 9PIN male connector is a prefabricated standardized part. The male connectors at both ends of the ribbon cable are matched one-to-one with the acquisition interface of the protection board and the 9PIN female connector. There is no manual welding operation during the insertion process, and the single module docking time is ≤10s.

[0062] Furthermore, in step S4, after the electrical assembly is completed, a full-function test is performed on the battery module. The test items include single-string voltage acquisition accuracy test, charge and discharge protection function test, charge and discharge cycle test, and insulation withstand voltage test to ensure that the battery module functions normally.

[0063] Furthermore, in step S5, when the battery module is packaged, screwless snap-fit ​​fixing is achieved through the fixing slot inside the flame-retardant shell. The shell is packaged by ultrasonic welding or screw fastening. After the packaging is completed, an appearance inspection and a final capacity inspection are carried out. After passing the inspection, the module is labeled and put into storage.

[0064] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0065] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. It should be noted that any technical features not described in detail in this invention can be implemented using any existing technology.

Claims

1. A high-efficiency welding structure for a lithium battery pack, comprising a cell array, a PCB motherboard, and a protection board unit, characterized in that: The PCB motherboard has cell positioning through holes that correspond one-to-one with each individual cell in the cell array. Each individual cell is vertically inserted into the cell positioning through hole to form a battery module. On the PCB motherboard, annular power pads are provided at both ends of the axial direction of each cell positioning through hole. The positive and negative poles of the inserted individual cell are respectively bonded to the corresponding annular power pads. The PCB motherboard has a pre-fabricated main power copper foil circuit. Each individual cell is electrically connected in a preset series-parallel relationship through the main power copper foil circuit. The PCB motherboard also has multiple single-string voltage acquisition copper foil traces prefabricated in it, which match the number of battery modules. The first end of each single-string voltage acquisition copper foil trace is electrically connected to the ring power pad corresponding to the corresponding battery cell. The ends of each single-string voltage acquisition copper foil trace are gathered and electrically connected to the signal pins of the 9-pin female connector. The 9-pin female connector is fixedly soldered to the surface of the PCB motherboard. The 9PIN female connector is connected to the acquisition interface of the protection board unit via a matching 9PIN male connector cable, enabling the transmission of a single string voltage signal from the battery module from the PCB motherboard to the protection board unit without an independent acquisition harness.

2. The high efficiency welding structure of lithium battery pack according to claim 1, characterized in that, The PCB motherboard is made of UL94V0 flame-retardant FR-4 fiberglass board, the copper thickness of the main power copper foil circuit is ≥2 ounces, and the copper thickness of the single-string voltage acquisition copper foil trace is ≥1 ounce.

3. The high efficiency welding structure of lithium battery pack according to claim 1, characterized in that, The annular power pads and the electrode surfaces of individual cells are connected by laser ring welding to form a continuous closed welding fusion layer; the main power copper foil circuit includes parallel unit traces and series unit traces. The positive and negative annular power pads of multiple individual cells in the same parallel group are electrically connected through parallel unit traces. Multiple groups of parallel units are electrically connected sequentially through series unit traces to form a series circuit with a preset number of series.

4. The high efficiency welding structure of lithium battery pack according to claim 1, characterized in that, Each single-string voltage acquisition copper foil trace has a safety insulation gap reserved between it and the main power copper foil circuit inside the PCB motherboard; the PCB motherboard has a foolproof positioning hole that matches the positioning post of the 9PIN female connector. The 9PIN female connector is oriented and installed through the positioning post and the foolproof positioning hole. Its pins from 1 to 9 are defined as the total negative terminal B- of the battery module, the positive terminals B1-B7 of the first to seventh strings of cells, and the total positive terminal B+ of the battery module.

5. The high efficiency welding structure of lithium battery pack according to claim 1, characterized in that, The PCB motherboard is provided with a total positive power pad and a total negative power pad that are electrically connected to the total positive and total negative terminals of the main power copper foil circuit, respectively. The total positive power pad and the total negative power pad are electrically connected to the power circuit of the protection board unit through copper pillars or power cables.

6. A method of producing a high-efficiency welding structure of a lithium battery pack according to any one of claims 1 to 5, characterized by, Includes the following steps: S1. PCB motherboard prefabrication: Based on the series and parallel number of the battery module and the specifications of the battery cells, complete the layout design of the PCB motherboard, and simultaneously complete the integrated wiring of the main power copper foil circuit and the single-string voltage acquisition copper foil trace; after the PCB motherboard is manufactured, the 9-pin female connector is mounted and soldered to the corresponding pads of the PCB motherboard. After continuity testing, it is confirmed that there are no open circuits or short circuits in the circuits inside the board, and the prefabricated PCB motherboard is obtained. S2. Cell pre-assembly: After sorting individual cells for consistency and cleaning the electrode surfaces, according to the polarity markings on the PCB motherboard, the individual cells are vertically inserted into the cell positioning through holes on the PCB motherboard one by one, so that the positive and negative electrode surfaces of the cells are in contact with the corresponding annular power pads, thus completing the pre-assembly of the battery module. S3. Integrated welding: The pre-assembled battery module is fixed to the welding fixture. The laser welding process is used to perform ring welding on the annular power pads at both ends of the PCB motherboard and the corresponding electrode surface of the battery cell. The series and parallel electrical connection between the battery cell and the main power copper foil circuit is completed in one step. At the same time, the conduction of each single string voltage acquisition copper foil trace and the corresponding battery cell is realized simultaneously. There is no independent acquisition wire harness welding process throughout the process. S4. Protection board docking: Prefabricate a finished ribbon cable with a 9-pin male connector, plug one end of the ribbon cable into the acquisition interface of the protection board unit, and plug the other end into the 9-pin female connector on the PCB motherboard. At the same time, connect the positive and negative terminals of the PCB motherboard to the power circuit of the protection board unit to complete the electrical assembly. S5. Packaging and Testing: Perform functional tests on the battery modules completed by the electrical assembly. After passing the tests, package them into a flame-retardant shell and put them into storage after completing the final inspection of the finished product.

7. The production method according to claim 6, wherein In step S1, the 9PIN female connector is mounted by an SMT placement machine and then soldered and fixed by reflow soldering. The peak temperature of the reflow soldering is 245±5℃, and the holding time in the constant temperature zone is 60s-90s. After soldering, an ICT continuity test is performed.

8. The preparation method according to claim 6, characterized in that, In step S2, the standard for cell consistency sorting is that the voltage difference of individual cells in the same batch is ≤5mV and the internal resistance difference is ≤2mΩ; after the individual cells are inserted, they achieve self-positioning through the cell positioning through hole, without the need for additional auxiliary clamps for fixation.

9. The preparation method according to claim 6, characterized in that, In step S3, the laser welding is performed using a fiber laser welding machine with process parameters of laser power 150W-300W and welding speed 30mm / s-50mm / s. After welding is completed, the internal resistance test of the main power circuit and the continuity test of the single-string voltage acquisition trace are performed simultaneously.

10. The method of claim 6, wherein, In step S4, the finished ribbon cable with a 9-pin male connector is a standardized prefabricated component, which is matched with the 9-pin female connector and the protection board acquisition interface in a foolproof manner, and there is no manual soldering operation during the insertion process; in step S5, the functional test includes single string voltage acquisition accuracy test, charge and discharge protection function test, and insulation withstand voltage test.

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