High-temperature-resistant and oxidation-resistant non-porous vehicle shunt and processing technology

Abstract

The application provides a high-temperature-resistant and oxidation-resistant non-porous vehicle shunt with the following structure, which comprises a resistance alloy and end bases connected at both ends of the resistance alloy; the end bases are uniformly covered with a nickel plating layer by adopting an electroplating dark nickel process, and a solder pad area is arranged at a position of the end base close to the resistance alloy for soldering a PCB; the nickel plating layer of the solder pad area is reduced in thickness by adopting a laser etching method; the end bases are integrated non-porous red copper end bases which are directly soldered to a vehicle-mounted copper bar by a laser soldering method; the dark nickel plating process of the application effectively avoids the problems of discoloration and tin aggregation of the plating layer caused by high temperature of an SMT furnace, the integrated non-porous structure of the end bases increases the flow area, and the flow capacity and heat dissipation efficiency are significantly improved; the end bases are directly laser soldered to the vehicle-mounted copper bar, which can eliminate the contact resistance, improve the measurement accuracy, and has higher connection strength than screw locking, strong anti-vibration capacity, adaptation to a complex vibration environment of a vehicle, and avoidance of loosening in long-term use.

Description

Technical Field

[0001] This invention relates to the field of splitter technology, specifically to a high-temperature resistant, oxidation-resistant, non-porous automotive splitter and its processing technology. Background Technology

[0002] In new energy vehicles and energy storage equipment, the accuracy and stability of the battery management system are crucial. A shunt is a device used to measure direct current. It consists of a resistor alloy and terminal blocks connected to both ends of the resistor alloy. It is made based on the principle that a voltage is generated across a resistor when direct current flows through it. It is commonly used to detect the main circuit current of the battery management system. The current value can be accurately calculated by measuring the sampling voltage of the resistor.

[0003] Existing shunts generally employ a surface-mount tin plating process, followed by PCB mounting via an SMT (Surface Mount Technology) oven. Through-holes are created at both ends of the shunt (current terminals), and the shunt is connected to the vehicle's copper busbars using screws. These shunts often present the following technical problems during application: 1. The tin plating layer is prone to discoloration and solder buildup in the high-temperature environment of the SMT oven, affecting the product's appearance and performance stability; 2. The through-hole design at both ends occupies effective conductive / heat dissipation area, limiting current carrying capacity and heat dissipation efficiency; 3. Screw fastening introduces contact resistance, reducing the shunt's measurement accuracy, and the fastening process is cumbersome; 4. Screw connections have poor mechanical stability and are prone to loosening under long-term vehicle vibration, affecting reliability. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a high-temperature resistant, oxidation-resistant, non-porous automotive splitter with stable performance and reliable use, as well as a processing technology.

[0005] The technical solution of this invention is to provide a high-temperature resistant, oxidation-resistant, non-porous automotive splitter with the following structure: It includes a resistance alloy and end bases connected to both ends of the resistance alloy; the end bases are uniformly covered with a nickel plating layer, and the end bases are provided with a pad area near the resistance alloy for PCB board soldering. The nickel plating layer thickness of the pad area is lower than the nickel plating layer thickness of other areas of the end bases.

[0006] Preferably, the end base is an integrated, non-porous copper end base.

[0007] This invention also provides a processing technology for a high-temperature resistant, oxidation-resistant, non-porous automotive splitter, comprising the following steps: S1. The two ends of the resistance alloy are welded to the end base to form a shunt; S2. The surface of the shunt is nickel-plated using a dark nickel electroplating process. S3. Use laser etching to perform rectangular etching on the entire surface area of ​​the resistance alloy and the end base pad area; S4. Solder and mount the PCB board onto the pad area of ​​the end base.

[0008] Preferably, the nickel plating thickness in step S2 is 5-10 μm to ensure that the nickel plating layer uniformly covers the surface of the distributor, without any missing plating or pinhole defects, thereby improving the temperature resistance and oxidation resistance.

[0009] Preferably, in step S3, the nickel plating on the surface of the resistance alloy is completely stripped off, and the nickel plating in the end base pad area is partially stripped off.

[0010] Preferably, the nickel plating thickness retained in the end base pad area is 0.5-1.5 μm.

[0011] As a preferred option, the relevant parameters for laser etching using a laser lifter are: speed 1800-2200mm / s, power 2-3w, and frequency 20-30kHz.

[0012] Preferably, the end base in step S1 is an integrated non-porous copper end base, which is directly welded to the vehicle-mounted copper busbar by laser welding to ensure that there are no false welds or cracks, and that the welding strength meets the vehicle vibration requirements.

[0013] With the above structure, the high-temperature resistant, oxidation-resistant, non-porous automotive splitter and its processing technology of the present invention have the following advantages compared with the prior art: 1. Improved Product Performance: The dark nickel plating process effectively avoids plating discoloration and tin buildup caused by high temperatures in SMT ovens, improving temperature resistance to over 260℃, significantly enhancing oxidation resistance, and extending plating lifespan; the integrated, non-porous structure of the terminal base increases the current flow area, improving current flow capacity by approximately 20% and heat dissipation efficiency by approximately 10%; the direct laser welding of the terminal base to the automotive copper busbar eliminates contact resistance, significantly improving shunt measurement accuracy, with measurement errors controlled within ±0.5%.

[0014] 2. Improved connection and mechanical structure: The end base is directly welded to the vehicle copper busbar by laser welding, which has a higher connection strength than screw fastening, strong vibration resistance, and is suitable for the complex vibration environment of the vehicle, avoiding loosening after long-term use; the holeless structure of the end base can simplify the product structure and improve the product assembly efficiency.

[0015] 3. Cost optimization: Eliminating the need for screw fastening and other processes reduces material consumption and lowers processing and assembly costs; improved plating stability reduces product defect rates and lowers subsequent maintenance costs; welding efficiency is higher than screw fastening, improving production efficiency and further reducing mass production costs; matte tin plating is more expensive than dark nickel plating, and matte tin is soft and prone to scratches, while dark nickel is harder and can effectively prevent these scratches. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the structure of the present invention.

[0017] Figure 2 This is a schematic diagram of the shunt structure of the present invention after patch mounting.

[0018] Figure 3 This is a comparison diagram of the current splitter of the present invention and a conventional current splitter.

[0019] Explanation of reference numerals in the attached figures: 1. Resistance alloy, 2. Terminal base, 21. Pad area, 3. PCB board. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] like Figures 1-3 As shown, the present invention discloses a high temperature resistance, oxidation resistance, and non-porous automotive shunt: including a resistance alloy 1 and end bases 2 connected to both ends of the resistance alloy 1; the end bases 2 are uniformly covered with a nickel plating layer, and a pad area 21 is provided on the end bases 2 near the resistance alloy 1 for soldering of the PCB board 3. The nickel plating layer thickness of the pad area 21 on the end bases 2 is lower than the nickel plating layer thickness of other areas of the end bases 2.

[0022] Among them, end base 2 is an integrated non-porous copper end base, which is directly welded to the vehicle copper busbar by laser welding.

[0023] This invention also discloses a processing technology for a high-temperature resistant, oxidation-resistant, non-porous automotive splitter, comprising the following steps: First, the two ends of the resistance alloy are welded to an integrated non-porous copper end base bundle to form a shunt.

[0024] Then, the surface of the shunt is nickel-plated using a dark nickel electroplating process; the nickel plating thickness is 5-10μm, preferably 10μm; during the dark nickel electroplating process, it is necessary to ensure that the nickel plating layer uniformly covers the surface of the shunt, without any missing plating or pinhole defects, in order to improve the temperature resistance and oxidation resistance.

[0025] Next, a rectangular etching method was used to etch the entire surface area of ​​the resistance alloy and the end base pad area. The nickel plating on the surface of the resistance alloy was completely removed, and the nickel plating in the end base pad area was partially removed, with the remaining nickel plating thickness in the end base pad area being 0.5-1.5μm. The relevant parameters for laser etching using the laser stripping machine were: speed 2200mm / s, power 3W, and frequency 30kHz.

[0026] Finally, the PCB board is soldered and mounted on the pad area of ​​the terminal base, and the integrated non-porous copper terminal is directly soldered to the vehicle copper busbar using laser welding to ensure that there are no poor solder joints or cracks, and that the welding strength meets the vehicle vibration requirements.

[0027] Conventional shunts typically employ a matte tin plating process. The shunt often serves as the substrate, requiring subsequent PCB mounting in an SMT (Surface Mount Technology) oven. Furthermore, the matte tin plating layer is prone to discoloration and tin buildup under the high temperatures of the SMT oven. This invention, however, utilizes a dark nickel plating process, effectively avoiding the discoloration and tin buildup issues caused by the high temperatures of the SMT oven. It also improves temperature resistance to over 260°C, significantly enhances oxidation resistance, and extends the plating's lifespan.

[0028] Conventional shunts require an insulating material to be wrapped around the middle during electroplating. However, since the electroplating solution is liquid, even with the insulating material, it can still seep in, leading to spreading and uncontrollable edge curvature, significantly affecting the product's appearance and performance. Because the insulating material covers the intermediate resistance alloy, it may cause copper exposure at the product's terminals. Therefore, the width of the insulating material needs to be 2mm narrower than the width of the intermediate resistance alloy to ensure good electroplating at the product's terminals. However, this inevitably results in tin layer spreading onto the intermediate resistance alloy, impacting both product performance and appearance. This invention, however, performs nickel plating on the entire shunt surface during electroplating, and then uses laser etching to perform rectangular etching on the surface area of ​​the resistance alloy, removing the spreading nickel plating layer. This simultaneously improves product performance and appearance consistency, reduces product defect rates, and lowers subsequent maintenance costs. Matte tin plating is more expensive than dark nickel plating, and matte tin is soft and prone to scratches, while dark nickel, being harder, effectively prevents these scratches.

[0029] After the invention was changed to electroplating dark nickel, although the risk of polytin or tin whiskers in the later stage was eliminated, the average resistance temperature coefficient of the shunt increased sharply due to the influence of the plating layer in the pad area, and the customer could not calibrate it. Therefore, it is necessary to increase the area of ​​laser peeling to reduce the plating thickness in the pad area, thereby improving the TCR of the product.

[0030] Conventional shunts have through holes at both current terminals (terminal bases) and are connected to the vehicle's copper busbar using screws. This through-hole design occupies valuable conductive / heat dissipation area, limiting current carrying capacity and heat dissipation efficiency. The screw-fastening process is cumbersome and introduces contact resistance, reducing the shunt's measurement accuracy and causing poor mechanical stability due to long-term vehicle vibration, leading to loosening and affecting reliability. In contrast, the terminal base of this invention features an integrated, hole-free structure, increasing the current carrying area by approximately 20% and heat dissipation efficiency by approximately 10%. The terminal base is directly laser-welded to the vehicle's copper busbar, eliminating contact resistance and significantly improving shunt measurement accuracy, with measurement errors controlled within ±0.5%. Furthermore, laser welding offers higher strength than screw fastening, providing stronger vibration resistance and adapting to the complex vibration environment of vehicles, preventing loosening over time. The hole-free structure of the terminal base also simplifies the product structure, improves assembly efficiency, eliminates the need for screw fastening, reduces material consumption, and lowers processing and assembly costs.

[0031] The following tests were conducted on the same specifications of the dark nickel-plated product of this application and the existing tin-plated product: Temperature resistance and oxidation resistance test: The dark nickel plating product of this application and the existing tin plating product were placed in the same SMT oven and kept at the same temperature for the same time. The tin layer of the existing tin plating product showed obvious discoloration and tin accumulation. The dark nickel plating product of this application did not discolor, did not peel off, and had a smooth surface. After salt spray test (neutral salt spray, 96h), the dark nickel plating layer of this application showed no rust and met the oxidation resistance standard.

[0032] Overcurrent and heat dissipation test: Under the same operating conditions, with an ambient temperature of 25°C and the same current, the surface temperature of the product of this application is about 10°C lower than that of the existing product, and the heat dissipation effect is significantly improved.

[0033] Accuracy and contact resistance testing: The contact resistance of existing screw-attached products is slightly higher than that of the laser-welded products of this application; the contact resistance of the products of this application is lower, which can reduce the temperature rise of the overall circuit of the client.

[0034] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-temperature resistant, oxidation-resistant, non-porous automotive shunt, comprising a resistance alloy (1) and end bases (2) connected to both ends of the resistance alloy (1); characterized in that, The end base (2) is uniformly covered with a nickel plating layer. The end base (2) is provided with a pad area (21) near the resistor alloy (1) for soldering the PCB board (3). The nickel plating layer thickness of the pad area (21) is lower than the nickel plating layer thickness of other areas of the end base (2).

2. The high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 1, characterized in that, The end base (2) is an integrated non-porous copper end base.

3. A processing method for the high-temperature resistant, oxidation-resistant, non-porous automotive splitter as described in claim 1 or 2, characterized in that, Includes the following steps: S1. The two ends of the resistance alloy are welded to the end base to form a shunt; S2. The surface of the shunt is nickel-plated using a dark nickel electroplating process. S3. Use laser etching to perform rectangular etching on the entire surface area of ​​the resistance alloy and the end base pad area; S4. Solder and mount the PCB board onto the pad area of ​​the end base.

4. The processing technology of a high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 3, characterized in that, The nickel plating thickness in step S2 is 5-10 μm.

5. The processing technology of a high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 4, characterized in that, In step S3, the nickel plating on the surface of the resistance alloy is completely stripped off, and the nickel plating in the end base pad area is partially stripped off.

6. The processing technology of a high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 5, characterized in that, The thickness of the nickel plating retained in the end base pad area is 0.5-1.5μm.

7. The processing technology of a high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 3 or 6, characterized in that, The relevant parameters for laser etching using a laser stripping machine are: speed 1800-2200mm / s, power 2-3w, and frequency 20-30kHz.

8. The processing technology of a high-temperature resistant, oxidation-resistant, non-porous automotive splitter according to claim 3, characterized in that, In step S1, the end base is an integrated non-porous copper end base, which is directly welded to the vehicle-mounted copper busbar by laser welding.

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