Silver-plated terminal part and silver-plated surface treatment method for improving pull-off force in ultrasonic welding

Abstract

The application discloses a silver-plated part surface treatment method for improving ultrasonic welding pull-off force, which comprises the following steps: 1) electroplating bright silver on a copper alloy base material, wherein the silver plating layer has a hardness HV≤150, and a silver-plated part is obtained; and 2) performing protection treatment on the surface of the silver-plated part, and a part to be welded is obtained; after the protection treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. The application has the beneficial effect that the application reduces the comprehensive hardness of the plating layer and selects a protection method after silver plating to reduce the surface tension of the plating layer, avoids the sliding of welding friction and the excessive thickness of the protection agent film layer, and prevents too much heterogeneous substance from being left on the welding surface, so that the welding strength is improved.

Description

Technical Field

[0001] This invention relates to the field of silver-plated terminal parts processing, and in particular to a surface treatment method for silver-plated parts to improve pull-out force during ultrasonic welding, and silver-plated terminal parts. Background Technology

[0002] Due to the excellent conductivity of silver-plated copper alloy substrates, silver-plated copper alloy terminals are widely used in new energy products. The connection between silver-plated contacts and copper wires mainly involves traditional crimping and ultrasonic welding. Ultrasonic welding offers advantages such as low welding resistance, resulting in superior temperature rise performance compared to traditional crimping. Furthermore, ultrasonic welding has a high tolerance for wire diameter and wire thickness variations; minor changes in material properties have no impact on the weld, and terminal dimensional tolerances are negligible—all advantages lacking in traditional crimping. Additionally, ultrasonically welded wire harnesses exhibit minimal impact on resistance and tensile strength under long-term external vibration, while traditional crimping suffers from continuously increasing resistance and decreasing tensile strength. Therefore, ultrasonic welding is increasingly replacing traditional crimping for contact components and wire harness connections in new energy vehicles.

[0003] Currently, end-users and secondary end-users of new energy products often specify silver plating requirements for terminals based on factors such as insertion / removal performance, sulfur resistance, and salt spray resistance. However, there is a lack of in-depth research on which plating layers and post-protection methods are effective for components used in ultrasonic welding applications. This has led to limitations in the development of ultrasonically welded silver-plated terminals, such as those for 80mm terminals. 2 The pull-out force after ultrasonic welding fluctuates between 1 and 4 kN for conductor cross-sectional area. However, according to QC / T29106-2014 Technical Specifications for Automotive Wiring Harnesses, the pull-out force between crimped and ultrasonically welded wires and terminals is within the range of 50-120 mm² conductor cross-sectional area. 2 The standard only specifies a minimum pull-out force of 2.7KN, but end customers have requested a stable pull-out force of ≥5KN. There is currently no effective surface treatment process to meet the requirement for direct welding of plated parts.

[0004] To achieve a pull-out force of ≥5KN, end customers typically remove the silver plating layer in the ultrasonic welding area through machining and milling before directly welding the copper alloy substrate and copper wire. Although this achieves the pull-out force of ≥5KN, it significantly impacts production efficiency and increases processing costs. Furthermore, the milling process must be completed as soon as possible to avoid copper oxidation and other quality risks. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a surface treatment method for silver-plated parts and silver-plated terminal parts for improving pull-out force in ultrasonic welding.

[0006] The objective of this invention is achieved through the following technical solution: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. This invention reduces the overall hardness of the coating and reduces the surface tension of the coating by screening the protection method after silver plating, thereby avoiding welding friction slippage and excessive foreign substances remaining on the welding surface due to excessively thick protective agent film, thus ensuring improved welding strength; Electroplating bright silver directly in the ultrasonic welding area, without nickel plating as a base, helps ensure that the coating is in a relatively soft state. This reduces the hardness of the coating, allowing for greater plastic deformation of the welded parts during subsequent ultrasonic welding. Simultaneously, the friction during ultrasonic welding acts on the lower-hardness coating surface, increasing the friction coefficient and frictional heat. This softens and enhances the interface material, increasing the activity of metal atoms in mutual diffusion. As a result, a metallurgical diffusion layer or vortex-like mechanical interlock is formed at the joint interface. Therefore, the ultrasonic welding quality at the joint can be improved, with the optimal quality reaching ≥7KN. Since the main purpose of post-silver plating treatment is to ensure its resistance to sulfidation and salt spray, traditional protective treatment for silver-plated parts mainly involves immersion in oil-based or water-based protective agents. However, because these agents contain organic lubricating components that reduce friction, the surface tension of the plating layer increases, resulting in a lower surface friction coefficient, which is detrimental to the increase of frictional heat. In addition, the film layer formed by traditional protective agents is relatively thick, which increases the presence of dissimilar non-metallic substances at the welding interface, thus affecting the reliability of welding strength. The present invention provides a protective treatment method for the surface of silver-plated parts, forming an inorganic film with a thickness of approximately 10 nm and an organic film with a thickness of approximately 10-50 nm. In contrast, the organic film thickness formed by traditional thick-film water-based post-protective agents is 150-500 nm. The silver plating post-treatment method selected in this invention avoids the thick film layer from isolating the silver and copper atoms, reducing the lubrication effect of the protective film layer, and preventing frictional slippage during ultrasonic welding, thus ensuring welding strength from two aspects. In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 50~120mm². 2 When the hardness of the silver plating layer HV≤100, the pull-out force is ≥7KN; when the hardness of the silver plating layer is 100<HV≤130, 7KN>pull-out force is ≥5KN; when the hardness of the silver plating layer is 130<HV≤150, 5KN>pull-out force is ≥3KN. The cross-sectional area of ​​the parts to be welded is 50–120 mm². 2If a hard silver plating layer with a hardness higher than HV>130 is used, it will be detrimental to ensuring that the pull-out force of the parts after ultrasonic welding remains at a high value. However, if the hardness of the hard layer is 130<HV≤150, the pull-out force of the parts after ultrasonic welding can also be ≥3KN, meeting the requirements of QC / T29106-2014 automotive wiring harness technical conditions. The lowest hardness of conventional bright silver plating layer is HV=80~90. When the hardness of the hard layer is HV≤100, the pull-out force of the parts after ultrasonic welding can reach a high value, with a pull-out force ≥7KN. If the thickness of the silver plating layer is ≤3μm, it will be detrimental to ensuring the corrosion protection of the copper alloy substrate. Therefore, the thickness of the silver plating layer only needs to be ≥3μm, and the thickness can be appropriately selected under the premise of cost consideration. Step 1) When electroplating dark nickel first and then bright silver, the hardness of the dark nickel plating layer is HV=130~200, and the thickness of the dark nickel plating layer is 0.5~1μm. Due to environmental and corrosion resistance requirements, some companies require nickel plating before silver plating. However, the nickel layer will increase the overall hardness of the plating layer. Therefore, dark nickel, which has the lowest hardness among nickels, is selected, with a hardness of HV=130~200. At the same time, for silver-plated parts that require nickel plating as a base, Watt's nickel plating system can be used for nickel plating as a base. By adopting a local shielding method, the thickness of the nickel layer on the ultrasonic welding surface can be controlled at 0.5~1μm to avoid excessive increase in the overall hardness of the plating layer due to excessive nickel plating thickness. At the same time, the increase in hardness caused by the nickel plating layer can be further offset by selecting the thickness and hardness of the hardness layer. In step 1), a dark nickel layer is plated before bright silver plating. When the hardness of the silver plating layer HV≤100, the thickness of the silver plating layer is ≥5μm; when the hardness of the silver plating layer 100<HV<130, the thickness of the silver plating layer is ≥8μm. For parts that require nickel plating as a base, a silver plating system with a silver plating layer hardness HV≤100 is adopted in the soldering area. An increase in the thickness of the silver layer of more than 5μm can offset the hardness increase caused by the nickel plating layer, thereby helping to reduce the overall hardness of the overall plating layer. However, if the hardness of the hard layer is 100<HV<130, the thickness of the silver plating layer must reach more than 8μm to effectively offset the hardness problem caused by the increase in the nickel plating layer. The protective treatment in step 2) adopts one or a combination of trivalent chromium electrolytic passivation protection or immersion in a nano-aqueous protective agent. Both trivalent chromium electrolytic passivation and nano-aqueous protective agents are beneficial in protecting the silver plating while reducing the surface tension of the plating, so that the dyne value of the plating can reach 34-38. In the preferred post-protection treatment method of the present invention, the inorganic nanofilm formed by trivalent chromium electrolytic passivation has no lubricating effect and the film is very thin, about 10 nm. The nano-aqueous protective agent contains relatively few lubricating components and the nano-aqueous film is thinner than that of conventional thick-film water-based protective agents.

[0007] In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40-50℃, a pH value of 5.8-6.5, a current density of 2-4 ASD, and electrolytic passivation is performed for 2-4 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1-2.5 g / L Cr2(SO4)3·xH2O and 10-20 g / L formic acid; compared with immersion coating with oil-based or water-based protective agents, trivalent chromium electroplating protective agent passivates the surface of the silver plating layer, thereby slowing down the discoloration rate of the silver plating layer due to corrosion reactions with oxygen, sulfur, etc.; at the same time, the electrolyte is selected as trivalent chromium sulfate combined with formic acid, which helps to ensure that the friction coefficient of the passivation protective layer meets the requirements and avoids slippage during welding; The nano-aqueous protective agent comprises, by weight, 30-45 parts of alkyl thiol, 15-25 parts of p-dimethylaminobenzamide derivative, 25-35 parts of penetrant, 120-180 parts of emulsifier, and 0.005-0.01 parts of nanoparticles, with the remainder being water; the nanoparticles have a particle size of 20-80 nm; the nano-aqueous protective agent facilitates the formation of chemical bonds with silver molecules to simultaneously form a protective film of nanoscale thickness, thereby blocking corrosion from air, water, and sulfides; simultaneously, the nanoscale thickness of the protective film can prevent corrosion of the copper wire and silver layer during ultrasonic welding. Friction and slippage during use; In this invention, the penetrant is one or more of sulfated castor oil, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, sodium alkyl succinate sulfonate, and sodium α-alkenyl sulfonate; the emulsifier is one or more of polyoxyethylene octylphenylphenol ether, nonylphenol polyoxyethylene ether, octylphenol polyoxyethylene ether, dibenzyl biphenol polyoxypropylene polyoxyethylene ether, and sorbitol ester; the nanomaterial is a non-metallic nanomaterial with a particle size of 20-80 nm; the selection of a nanomaterial particle size of 20-80 nm is beneficial for controlling the surface tension of the silver plating layer after it is applied to the silver plating layer. After ultrasonic welding, a protective oil is applied to the insertion and extraction contact area. Since the hardness of the plating layer decreases, its wear resistance decreases, affecting its insertion and extraction life. Preferably, after ultrasonic welding, a perfluoropolyether oil post-treatment agent is applied to the insertion and extraction contact area to ensure that the insertion and extraction life is not significantly reduced, maintaining 6000-8000 cycles. If the insertion and extraction contact area is not treated with protective oil, the insertion and extraction life is reduced to 500-3000 cycles. The protective oil is a perfluoropolyether oil. Perfluoropolyether oil is commonly used as a lubricant for mechanical components. It has flexibility, a low glass transition temperature, and an extremely wide co-liquid temperature range. On the other hand, due to the strong electron-withdrawing effect of fluorine, the polymer does not exhibit ether properties, thus it has excellent heat resistance, chemical stability, oxidation stability, and complete non-flammability. When it is applied as a protective agent to the insertion and extraction contact area, it was found that the insertion and extraction life was not significantly reduced and could be maintained at 6000 to 8000 cycles. The present invention also provides a silver-plated copper alloy terminal part for ultrasonic welding, which is prepared by the above-mentioned silver plating surface treatment method.

[0008] The present invention has the following advantages: 1. This invention reduces the overall hardness of the coating and reduces the surface tension of the protective agent by screening the protection method after silver plating, thereby avoiding welding friction slippage and excessive residue of foreign substances on the welding surface due to excessively thick protective agent film, thus ensuring improved welding strength; 2. Direct electroplating of bright silver in the ultrasonic welding area, without nickel plating as a base, helps to ensure that the hardness of the coating is relatively soft. This reduces the hardness of the coating, which increases the plastic deformation of the surface of the welded parts during subsequent ultrasonic welding. At the same time, the friction during ultrasonic welding acts on the surface of the coating with lower hardness. Due to the lower hardness, the friction coefficient increases, leading to increased frictional heat. This softens and enhances the interface material, and increases the activity of metal atoms in mutual diffusion. As a result, a metallurgical diffusion layer or vortex-shaped mechanical interlock is formed at the joint interface. Therefore, the ultrasonic welding quality at the joint can be improved, with the best reaching ≥7KN. 3. Since the post-treatment of silver plating is mainly to ensure its resistance to sulfidation and salt spray, traditional protective treatment of silver-plated parts mainly uses immersion coating with oil-based or water-based protective agents. For silver-plated parts used in new energy applications, considering the cost of protective agents, conventional water-based protective agents are generally chosen. However, because these contain organic lubricating components that reduce friction, the surface tension of the plating layer increases, resulting in a lower surface friction coefficient, which is detrimental to the increase of frictional heat. Furthermore, the film formed by traditional water-based protective agents is relatively thick, leading to an increase in dissimilar non-metallic substances at the welding interface, which is detrimental to the reliability of welding strength. This invention provides protection for the surface of silver-plated parts. The treatment method involves selecting an inorganic nanofilm formed by trivalent chromium electrolytic passivation, which has no lubricating effect and is very thin, around 10 nm. In contrast, a nano-aqueous protective agent is chosen because it contains relatively less lubricating components and its film thickness is thinner than conventional post-film water-based protective agents. This avoids the thick film layer isolating silver and copper atoms, reducing the lubricating effect of the protective film and preventing frictional slippage during ultrasonic welding, thus ensuring welding strength from two aspects. Simultaneously, salt spray testing guarantees no corrosion for 240 hours, and its resistance to sulfide discoloration reaches 3% potassium sulfide, remaining stable and unchanged for over 3 minutes. 4. The reduced hardness of the coating will decrease its wear resistance and affect its insertion and removal life. To address this, after ultrasonic welding, a perfluoropolyether oil post-treatment agent can be applied to the insertion and removal contact area. This will ensure that the insertion and removal life is not significantly reduced and can be maintained at 6,000 to 8,000 cycles. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0010] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0011] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0012] Example 1: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤130, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 50~120mm². 2 When the hardness of the silver plating layer HV≤100, the pull-out force is ≥7KN; when the hardness of the silver plating layer is 100<HV≤130, 7KN>pull-out force is ≥5KN; when the hardness of the silver plating layer is 130<HV≤150, 5KN>pull-out force is ≥3KN. Step 1) When electroplating dark nickel first and then bright silver, the hardness of the dark nickel plating is HV=130~200, and the thickness of the dark nickel plating is 0.5~1μm; In step 1), a dark nickel layer is plated before electroplating bright silver. When the hardness of the silver plating HV≤100, the thickness of the silver plating is ≥5μm; when the hardness of the silver plating is 100<HV<130, the thickness of the silver plating is ≥8μm. The protective treatment in step 2) adopts one of the following methods or a combination of two: trivalent chromium electrolytic passivation protection or immersion in a nano-aqueous protective agent. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40-50℃, a pH value of 5.8-6.5, a current density of 2-4 ASD, and electrolytic passivation for 2-4 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1-2.5 g / L Cr2(SO4)3·xH2O and 10-20 g / L formic acid; The nano-aqueous protective agent comprises, by weight, 30-45 parts of alkyl thiol, 15-25 parts of p-dimethylaminobenzamide derivative, 25-35 parts of penetrant, 120-180 parts of emulsifier, and 0.005-0.01 parts of nanoparticles, with the remainder being water; the nanoparticles have a particle size of 20-80 nm. After the parts to be welded are ultrasonically welded, a protective oil is also applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil.

[0013] Example 2: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 80mm². 2 The hardness of the silver plating is HV≤100. The protection treatment employs trivalent chromium electrolytic passivation protection. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40°C, a pH value of 5.8, a current density of 2ASD, and electrolytic passivation for 2 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1 g / L Cr2(SO4)3·xH2O and 10 g / L formic acid; After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥7KN.

[0014] Example 3: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating dark nickel and then bright silver on a copper alloy substrate, with the hardness of the silver plating layer HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38; In step 1), the silver plating thickness is ≥3μm, and the cross-sectional area of ​​the part to be welded is 80mm². 2 ; In step 1), the hardness of the dark nickel plating is HV=130~200, the thickness of the dark nickel plating is 0.5~1μm, the hardness of the silver plating is HV≤100, and the thickness of the silver plating is ≥5μm; The protection treatment employs trivalent chromium electrolytic passivation protection. The specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 50°C, a pH value of 6.5, a current density of 4ASD, and electrolytic passivation for 4 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 2.5 g / L Cr2(SO4)3·xH2O and 20 g / L formic acid; After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥5KN.

[0015] Example 4: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. Step 1) Silver plating thickness ≥ 3μm; cross-sectional area of ​​the part to be welded is 80mm². 2 The hardness of the silver plating is HV≤100. The protective treatment involves immersion in a nano-aqueous protective agent. The nano-aqueous protective agent, by weight, comprises 30 parts of alkyl thiol, 15 parts of p-dimethylaminobenzamide derivative, 25 parts of penetrant, 120 parts of emulsifier, and 0.005 parts of nanoparticles, with the remainder being water. The nanoparticles have a particle size of 50 nm. After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥7KN.

[0016] Example 5: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 80mm². 2 The hardness of the silver plating is 100 < HV ≤ 130. The protection treatment employs trivalent chromium electrolytic passivation protection. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40°C, a pH value of 5.8, a current density of 2ASD, and electrolytic passivation for 2 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1 g / L Cr2(SO4)3·xH2O and 10 g / L formic acid; After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥5KN.

[0017] Example 6: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38. In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 80mm². 2 The hardness of the silver plating is 130 < HV ≤ 150. The protection treatment employs trivalent chromium electrolytic passivation protection. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40°C, a pH value of 5.8, a current density of 2ASD, and electrolytic passivation for 2 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1 g / L Cr2(SO4)3·xH2O and 10 g / L formic acid; After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥3KN.

[0018] Example 7: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating dark nickel and then bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded; after the protective treatment in step 2), the dyne value of the plating layer on the part to be welded is 34-38; In step 1), the silver plating thickness is ≥3μm, and the cross-sectional area of ​​the part to be welded is 80mm². 2 ; In step 1), the hardness of the dark nickel plating layer is HV=130~200, the thickness of the dark nickel plating layer is 0.5~1μm, and when the hardness of the silver plating layer is 100<HV<130, the thickness of the silver plating layer is ≥8μm. The protective treatment employs a nano-aqueous protective agent; the nano-aqueous protective agent, by weight, comprises 30 parts of alkyl thiol, 15 parts of p-dimethylaminobenzamide derivative, 25 parts of penetrant, 120 parts of emulsifier, and 0.005 parts of nanoparticles, with the remainder being water; the nanoparticles have a particle size of 50 nm. After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥5KN.

[0019] Example 8: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating dark nickel and then bright silver on a copper alloy substrate, with the hardness of the silver plating layer HV≤150, to obtain silver-plated parts; 2) performing a protective treatment on the surface of the silver-plated parts to obtain the parts to be welded. After the protective treatment in step 2), the dyne value of the coating on the workpiece to be welded is 34-38; In step 1), the silver plating thickness is ≥3μm, and the cross-sectional area of ​​the part to be welded is 80mm². 2 ; In step 1), the hardness of the dark nickel plating is HV=130~200, and the thickness of the dark nickel plating is 0.5~1μm; the hardness of the silver plating is HV≤100, and the thickness of the silver plating is ≥5μm. The protective treatment employs a combination of trivalent chromium electrolytic passivation protection and immersion in a nano-aqueous protective agent. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 45°C, a pH value of 6.0, a current density of 3ASD, and electrolytic passivation for 3 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 2.0 g / L Cr2(SO4)3·xH2O and 15 g / L formic acid; The nano-aqueous protective agent comprises, by weight, 40 parts of alkyl thiol, 20 parts of p-dimethylaminobenzamide derivative, 30 parts of penetrant, 150 parts of emulsifier, and 0.008 parts of nanoparticles, with the remainder being water; the nanoparticles have a particle size of 50 nm. After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the part after ultrasonic welding is ≥5KN.

[0020] Example 9: A surface treatment method for silver-plated parts to improve pull-out force in ultrasonic welding, comprising the following steps: 1) electroplating bright silver on a copper alloy substrate, wherein the hardness of the silver plating layer is HV≤150, to obtain a silver-plated part; 2) performing a protective treatment on the surface of the silver-plated part to obtain a part to be welded. After the protective treatment in step 2), the dyne value of the coating on the workpiece to be welded is 34-38; In step 1), the silver plating thickness is ≥3μm; the cross-sectional area of ​​the part to be welded is 80mm². 2 The hardness of the silver plating is HV≤100. The protective treatment employs a combination of trivalent chromium electrolytic passivation protection and immersion in a nano-aqueous protective agent. In step 2), the specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 45°C, a pH value of 6.0, a current density of 3ASD, and electrolytic passivation for 3 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 2.0 g / L Cr2(SO4)3·xH2O and 15 g / L formic acid; The nano-aqueous protective agent comprises, by weight, 40 parts of alkyl thiol, 20 parts of p-dimethylaminobenzamide derivative, 30 parts of penetrant, 150 parts of emulsifier, and 0.008 parts of nanoparticles, with the remainder being water; the nanoparticles have a particle size of 50 nm. After the parts to be welded are ultrasonically welded, a protective oil is applied to the insertion and extraction contact area. The protective oil is a perfluoropolyether oil; In this embodiment, the pull-out force of the ultrasonically welded part is ≥7KN.

[0021] Comparative Example 1: Copper alloy terminal parts were treated using the same method as in Example 7, except that hard silver was selected for silver plating; the hard silver plating hardness was HV=170, and the hard silver plating thickness was 3μm; the cross-sectional area of ​​the silver-plated solder joint was 80mm². 2 The pull-out force after ultrasonic welding is ≥1.5KN.

[0022] Comparative Example 2: The same method as in Example 7 was used, except that a conventional thick-film water-based post-protective agent was selected for the silver-plated parts; the agent thickness was ≥0.1 micrometers; and the cross-sectional area of ​​the silver-plated welded parts was 80 mm². 2The pull-out force after ultrasonic welding is ≥5KN. Combining the results of Comparative Example 1 and Comparative Example 2, it can be seen that the most significant factor affecting the pull-out force after ultrasonic welding is the overall hardness of the coating, followed by the post-treatment method. Reducing the coating hardness and appropriately selecting the post-treatment method, allowing both to work together, is beneficial for maximizing the pull-out force.

[0023] Comparative Example 3: The same method as in Example 7 was used, except that after ultrasonic welding, no protective oil was applied to the insertion / removal contact area; the cross-sectional area of ​​the silver-plated welded part was 80 mm². 2 The lifespan of the insertion / removal area is 500-3000 cycles. Multiple experiments revealed that not applying protective oil to the insertion / removal contact area after ultrasonic welding affects the lifespan of the area. This indicates that applying protective oil helps ensure that a decrease in plating hardness does not significantly impact the insertion / removal lifespan.

[0024] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 surface treatment method for silver-plated parts to improve pull-out force during ultrasonic welding, characterized in that, The process includes the following steps: 1) Electroplating bright silver onto a copper alloy substrate, with a silver plating hardness of HV≤150, to obtain a silver-plated part; 2) Protecting the surface of the silver-plated part to obtain the part to be welded. After the protective treatment in step 2), the dyne value of the plating on the workpiece to be welded is 34-38, and the thickness of the silver plating in step 1) is ≥3μm; the cross-sectional area of ​​the workpiece to be welded is 50-120mm². 2 When the hardness of the silver plating layer HV≤100, the pull-out force ≥7KN; when the hardness of the silver plating layer 100<HV≤130, 7KN>pull-out force ≥5KN; when the hardness of the silver plating layer 130<HV≤150, 5KN>pull-out force ≥3KN; the protective treatment in step 2) adopts one or a combination of trivalent chromium electrolytic passivation protection or immersion in a nano-aqueous protective agent, wherein the nano-aqueous protective agent, by weight, includes 30-45 parts of alkyl thiol, 15-25 parts of p-dimethylaminobenzamide derivative, 25-35 parts of penetrant, 120-180 parts of emulsifier, and 0.005-0.01 parts of nanoparticles, with the remainder being water; the particle size of the nanoparticles is 20-80nm; The specific operation of trivalent chromium electrolytic passivation is as follows: the silver-plated parts are placed in a trivalent chromium electroplating protective agent at a temperature of 40-50℃, a pH value of 5.8-6.5, a current density of 2-4 ASD, and electrolytic passivation for 2-4 minutes; after electrolytic passivation, the parts are cleaned and dried; the trivalent chromium electroplating protective agent includes 1-2.5 g / L Cr2(SO4)3•xH2O and 10-20 g / L formic acid; After steps 1) and 2), the inorganic film thickness formed on the surface of the silver-plated part is 10 nm, and the organic film thickness is 10-50 nm.

2. The surface treatment method for improving the pull-out force of silver-plated parts for ultrasonic welding according to claim 1, characterized in that, In step 1), a dark nickel layer is plated before electroplating bright silver. The hardness HV of the dark nickel plating layer is 130-200, and the thickness of the dark nickel plating layer is 0.5-1μm.

3. The surface treatment method for improving the pull-out force of silver-plated parts for ultrasonic welding according to claim 2, characterized in that, In step 1), a dark nickel layer is plated before electroplating bright silver. When the hardness of the silver plating HV≤100, the thickness of the silver plating is ≥5μm; when the hardness of the silver plating 100<HV<130, the thickness of the silver plating is ≥8μm.

4. The surface treatment method for improving the pull-out force of silver-plated parts for ultrasonic welding according to claim 1, characterized in that, After the parts to be welded are ultrasonically welded, a protective oil is also applied to the insertion and extraction contact area.

5. The surface treatment method for improving the pull-out force of silver-plated parts for ultrasonic welding according to claim 4, characterized in that, The protective oil is a perfluoropolyether oil.

6. A silver-plated copper alloy terminal part for ultrasonic welding, characterized in that: It is prepared by the surface treatment method of silver-plated parts according to any one of claims 1 to 5.