Novel nickel sheet structure and method for welding lithium battery cell and PCM

Abstract

The invention aims to provide a novel nickel sheet structure and a method for welding a lithium battery cell and PCM (Pulse Code Modulation). The device comprises a nickel sheet body (1), a bending part (2) is arranged in the middle of the nickel sheet body (1), the bending part (2) forms a preset bending angle, the nickel sheet body (1) is divided into an SMT pasting surface (3) and a laser welding surface (4) which are staggered with each other through the bending part (2), the SMT pasting surface (3) is used for conducting SMT pasting connection with a bonding pad of a PCM (5), and the laser welding surface (4) is used for conducting laser welding on the bonding pad of the PCM (5). The laser welding surface (4) is used for carrying out laser welding with a tab (7) of a lithium battery cell (6), and the preset bending angle is an angle which enables the PCM and the cell to form a convex buffer structure after entering a shell; the method comprises the following steps of SMT, laser welding, welding spot detection and in-shell assembly. The method is applied to the technical field of battery welding.

Description

Technical Field

[0001] This invention relates to the field of battery welding technology, specifically to a novel nickel sheet structure for welding lithium battery cells to PCM and a method for welding lithium battery cells to PCM. Background Technology

[0002] In the production process of lithium batteries (especially lithium polymer batteries), the connection between the cell and the PCM (battery protection board) typically uses nickel sheets as intermediate connectors and is fixed by laser welding. Laser welding is widely used in this process due to its high welding efficiency and high weld strength. However, existing laser welding technology and its supporting nickel sheet structure still have significant shortcomings, making it difficult to meet the high reliability and low cost production requirements of lithium batteries. First, existing nickel sheets are mostly planar or simple L-shaped structures, and there is no effective buffer structure after the cell and nickel sheet are welded. When the battery is subjected to drop impact or vibration, the weld between the cell tab and the nickel sheet is prone to breakage due to stress concentration. If an additional cell buffer structure is designed to achieve the buffer function, it will not only increase the cost of the parts, but may also affect the alignment accuracy of laser welding due to the buffer structure occupying welding space, thereby reducing the welding quality.

[0003] Secondly, the existing welding process suffers from poor weld point inspection convenience. After the cell tabs are welded to the nickel sheets, the tabs are often covered or obscured by the nickel sheets. Traditional visual inspection can only observe a single surface of the weld, and cannot simultaneously detect whether there are defects such as incomplete welds or perforations on both sides. This results in some hidden weld defects flowing into subsequent processes, affecting the overall reliability of the battery.

[0004] Furthermore, for some designs that use L-shaped nickel sheets, a nickel sheet folding process needs to be added before welding to accommodate the assembly positions of the PCM and the battery cell. This process not only increases the number of production steps and labor costs, but may also cause the nickel sheet to deform due to stress during the folding process, further affecting the welding accuracy.

[0005] Finally, during SMT assembly of planar nickel sheets with PCMs, solder tends to creep along the nickel sheet surface to the laser welding surface, causing contamination. This contaminated surface leads to uneven energy reflection during laser welding, resulting in incomplete solder joints or burn-through, reducing welding reliability and increasing the defect rate.

[0006] Therefore, there is an urgent need for a new nickel sheet structure and a matching welding method that can solve the problems of insufficient buffering, inconvenient testing, high cost, and solder creep, so as to improve the reliability and production efficiency of welding lithium battery cells to PCM. Summary of the Invention

[0007] This invention aims to address the shortcomings of existing technologies by providing a novel nickel sheet structure and a method for welding lithium battery cells to PCM.

[0008] The technical solution adopted in this invention is a novel nickel sheet structure for welding lithium battery cells to PCM. The novel nickel sheet structure includes a nickel sheet body with a bent portion in the middle. The bent portion forms a preset bending angle. The nickel sheet body is configured with mutually staggered SMT mounting surfaces and laser welding surfaces through the bent portion. The SMT mounting surfaces are used for SMT mounting connection with the pads of the PCM, and the laser welding surfaces are used for laser welding with the tabs of the lithium battery cell. The preset bending angle is the angle that allows the PCM and the cell to form a raised buffer structure after being installed in the casing.

[0009] Furthermore, the bottom of the nickel sheet body is provided with support feet.

[0010] Furthermore, the support foot is provided in two symmetrically distributed on both sides of the bottom of the nickel sheet body. The height of the support foot is adapted to the support requirements of the nickel sheet body during SMT placement, so as to prevent the nickel sheet body from tipping over during the SMT placement process.

[0011] Furthermore, the surface of the laser-welded surface is provided with an anti-oxidation coating.

[0012] A method for welding lithium battery cells to PCM using the above-mentioned novel nickel sheet structure, the method comprising the following steps: S1, SMT placement: Apply solder paste to the SMT placement surface while preventing solder from creeping onto the laser welding surface. Design suitable pads on the PCM and perform placement and soldering operations between the SMT placement surface and the pads on the PCM. S2. Laser welding: The nickel sheet body is held in a welding fixture so that the laser welding surface is in contact with the electrode tab of the lithium battery cell, and the laser welding surface and the electrode tab are at the same level. The laser welding equipment is started to perform welding. S3. Welding point inspection: After welding is completed, keep the nickel sheet body and the tab in the clamping state in the welding fixture, transfer the welding fixture to the welding point inspection process, and inspect the front and back of the welded area with a visual inspection device to determine whether there are defects such as false welding or perforation. S4. Casing Assembly: If the solder joint inspection is qualified, the PCM with the welded nickel sheet body and the lithium battery cell will be installed into the casing as a whole. The bent part of the nickel sheet body and the welded part between the nickel sheet body and the electrode tab will together form a raised buffer structure after installation.

[0013] Furthermore, in step S1, the area of ​​the pads on the PCM is the same as the area of ​​the SMT mounting surface of the nickel sheet body, and the distance between the edge of the pads on the PCM and the edge of the laser welding surface of the nickel sheet body is not less than 1mm to prevent solder from creeping.

[0014] Furthermore, in step S3, the visual inspection device includes at least two CCD cameras, corresponding to the front and back of the weld, respectively; the shooting area of ​​the CCD camera covers the entire weld point, and the image comparison algorithm is used to determine whether the weld point meets the quality requirements.

[0015] Furthermore, in step S4, the height of the raised buffer structure formed by the bent portion of the nickel sheet body is 0.5 to 2 mm.

[0016] The beneficial effects of this invention are as follows: In this invention, the nickel sheet body is provided with a bending part with a preset bending angle. After the PCM and the battery cell are installed in the casing, a raised buffer structure will naturally form. When the battery is dropped or impacted, the raised structure will be deformed first to absorb the impact energy and prevent the battery cell tab and the nickel sheet from breaking due to stress concentration. This significantly improves the battery's durability and impact resistance.

[0017] Secondly, the nickel sheet body of the present invention clearly distinguishes between the staggered SMT mounting surface and the laser welding surface, and the pads on the PCM are designed according to the SMT mounting surface and have reserved isolation distance. When mounting SMT, the solder only flows on the SMT mounting surface and will not crawl to the laser welding surface, thus avoiding the problems of cold solder joints and solder burn-through caused by welding surface contamination. Therefore, the reliability of laser welding is guaranteed and the defect rate is reduced.

[0018] Furthermore, this invention uses a welding fixture to fix the nickel sheet and the battery cell tab. After welding, the fixture can be transferred to the inspection process without disassembling it. The two CCD cameras of the visual inspection equipment can take pictures of the front and back of the weld respectively, which can comprehensively detect defects such as incomplete welding and perforation, and prevent hidden defective products from flowing into subsequent processes, thereby improving the controllability of welding quality.

[0019] Finally, the nickel sheet body of the present invention directly achieves the buffering function through the bending part, without the need for additional design of the battery cell buffer structure; at the same time, the L-shaped nickel sheet folding process is eliminated, reducing production steps and parts costs. Therefore, while improving product performance, production costs are reduced and production efficiency is improved. Attached Figure Description

[0020] Figure 1 This is a simplified structural diagram of the novel nickel sheet structure. Figure 2 This is a schematic diagram of the overall structure of the battery after welding; Figure 3 This is a simplified flowchart of the method of the present invention. Detailed Implementation

[0021] like Figures 1-3As shown, this invention discloses a novel nickel sheet structure for welding lithium battery cells to PCM. It includes a nickel sheet body 1 with a bending portion 2 in the middle. The bending portion 2 forms a preset bending angle. The nickel sheet body 1 is divided into an SMT mounting surface 3 and a laser welding surface 4, which are staggered by the bending portion 2. The SMT mounting surface 3 is used for SMT mounting connection with the pads of the PCM 5, and the laser welding surface 4 is used for laser welding with the tabs 7 of the lithium battery cell 6. The preset bending angle is the angle at which a raised buffer structure can be formed after the PCM and the cell are installed in the casing.

[0022] Specifically, the bottom of the nickel sheet body 1 is provided with a support foot 8.

[0023] The support feet 8 are provided in two symmetrically distributed on both sides of the bottom of the nickel sheet body 1. The height of the support feet 8 is adapted to the support requirements of the nickel sheet body during SMT placement, so as to prevent the nickel sheet body 1 from tipping over during the SMT placement process.

[0024] The surface of the laser welding surface 4 is provided with an anti-oxidation coating.

[0025] A method for welding lithium battery cells to PCM using the novel nickel sheet structure described above, the method comprising the following steps: S1, SMT placement: Apply solder paste to the SMT placement surface 3 while preventing solder from creeping onto the laser welding surface 4. Design suitable pads on the PCM5 and perform placement and soldering operations on the SMT placement surface 3 and the pads on the PCM. S2. Laser welding: The nickel sheet body 1 is held in a welding fixture so that the laser welding surface 4 is in contact with the electrode tab of the lithium battery cell, and the laser welding surface 4 and the electrode tab 7 are on the same horizontal plane. The laser welding equipment is started to perform welding. S3. Welding point inspection: After welding is completed, keep the nickel sheet body 1 and the tab 7 in the clamping state in the welding fixture, transfer the welding fixture to the welding point inspection process, and use visual inspection equipment to inspect the front and back of the weld to determine whether there are defects such as false welding or perforation. S4. Casing Assembly: If the solder joint inspection is qualified, the PCM with the welded nickel sheet body and the lithium battery cell will be installed into the casing as a whole. The bent part of the nickel sheet body and the welded part between the nickel sheet body and the electrode tab will together form a raised buffer structure after installation.

[0026] Specifically, in step S1, the area of ​​the pads on the PCM is the same as the area of ​​the SMT mounting surface of the nickel sheet body, and the distance between the edge of the pads on the PCM and the edge of the laser welding surface of the nickel sheet body is not less than 1mm to prevent solder from creeping.

[0027] In step S3, the visual inspection device includes at least two CCD cameras, corresponding to the front and back of the weld, respectively; the shooting area of ​​the CCD camera covers the entire weld point, and the image comparison algorithm is used to determine whether the weld point meets the quality requirements.

[0028] In step S4, the height of the raised buffer structure formed by the bent portion of the nickel sheet body is 0.5 to 2 mm.

[0029] In this invention, when assembling the welded assembly, the PCM with the welded nickel sheet body and the battery cell are placed into the battery casing. At this time, the bent portion of the nickel sheet body and the welded portion formed by welding the nickel sheet body to the electrode tabs naturally form a raised buffer structure due to the constraint of the casing. After assembly, a drop test is performed from a height of 1.2m, allowing the battery cell to fall freely onto a cement ground. After the test, the battery cell electrode tabs are disassembled and inspected, and no solder joints have fallen off, proving that the buffer structure is effective.

[0030] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel nickel sheet structure for welding lithium battery cells to PCM, characterized in that, The device includes a nickel sheet body (1), which has a bending portion (2) in the middle. The bending portion (2) forms a preset bending angle. The nickel sheet body (1) is divided into an SMT mounting surface (3) and a laser welding surface (4) that are staggered from each other through the bending portion (2). The SMT mounting surface (3) is used to connect with the pads of the PCM (5) via SMT mounting. The laser welding surface (4) is used to perform laser welding with the tabs (7) of the lithium battery cell (6). The preset bending angle is the angle at which the PCM and the battery cell can form a raised buffer structure after being installed in the casing.

2. The novel nickel sheet structure according to claim 1, characterized in that, The nickel sheet body (1) is provided with a support foot (8) at the bottom.

3. The novel nickel sheet structure according to claim 2, characterized in that, The support foot (8) is provided in two parts, and the two support feet (8) are symmetrically distributed on both sides of the bottom of the nickel sheet body (1). The height of the support foot (8) is adapted to the support requirements of the nickel sheet body during SMT placement, so as to prevent the nickel sheet body (1) from tipping over during the SMT placement process.

4. The novel nickel sheet structure according to claim 1, characterized in that, The surface of the laser welding surface (4) is provided with an anti-oxidation coating.

5. A method for welding lithium battery cells to PCM using the novel nickel sheet structure as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: S1, SMT placement: Apply solder paste to the SMT placement surface (3) while preventing solder from creeping onto the laser welding surface (4). Design suitable pads on the PCM (5) and perform placement and soldering operations on the SMT placement surface (3) and the pads on the PCM. S2. Laser welding: The nickel sheet body (1) is held in a welding fixture so that the laser welding surface (4) is in contact with the electrode tab of the lithium battery cell and the laser welding surface (4) and the electrode tab (7) are on the same horizontal plane. The laser welding equipment is started to perform welding. S3. Welding point inspection: After welding is completed, keep the nickel sheet body (1) and the tab (7) in the clamping state in the welding fixture, transfer the welding fixture to the welding point inspection process, and inspect the front and back of the welded area with a visual inspection device to determine whether there are defects such as false welding or perforation. S4. Housing assembly: If the solder joint inspection is qualified, the PCM with the nickel sheet body welded on it and the lithium battery cell are installed into the housing as a whole. The bent part of the nickel sheet body and the welded part formed after the nickel sheet body is welded to the electrode tab together form a raised buffer structure after installation.

6. The method for welding lithium battery cells to PCM according to claim 5, characterized in that, In step S1, the area of ​​the pads on the PCM is the same as the area of ​​the SMT mounting surface of the nickel sheet body, and the distance between the edge of the pads on the PCM and the edge of the laser welding surface of the nickel sheet body is not less than 1mm to prevent solder from creeping.

7. The method for welding lithium battery cells to PCM according to claim 5, characterized in that, In step S3, the visual inspection device includes at least two CCD cameras, corresponding to the front and back of the weld, respectively; the shooting area of ​​the CCD camera covers the entire weld point, and the image comparison algorithm is used to determine whether the weld point meets the quality requirements.

8. The method for welding lithium battery cells to PCM according to claim 5, characterized in that, In step S4, the height of the raised buffer structure formed by the bent portion of the nickel sheet body is 0.5 to 2 mm.

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