Corrosion-resistant terminal and manufacturing method thereof

Abstract

The invention provides a corrosion-resistant terminal and a manufacturing method thereof, and belongs to the technical field of electric connectors. The copper-based porous anchoring layer and the nickel-phosphorus compact barrier layer are arranged between the copper alloy matrix and the outer contact layer, so that a coating system has a synergistic effect in structure and function. The copper-based porous anchoring layer improves the mechanical bonding strength between the plating layer and the substrate through a controlled microporous structure of the copper-based porous anchoring layer, and relieves interface stress concentration caused by thermal cycle and mechanical load, so that the cracking and stripping risks of the plating layer are reduced; the nickel-phosphorus compact barrier layer has excellent compactness and barrier performance, so that a corrosion medium is effectively inhibited from permeating to a matrix along microdefects, and the probability of corrosion occurrence is remarkably reduced; and the non-through pore structure of the copper-based composite porous anchoring layer avoids rapid permeation of a corrosive medium, and the synergistic effect of the two-layer structure remarkably reduces the occurrence risks of pitting corrosion and corrosion under an interface.

Description

Technical Field

[0001] This invention relates to the field of electrical connector technology, and in particular to a corrosion-resistant terminal and its manufacturing method. Background Technology

[0002] Connector terminals, as precision electrically conductive components, are widely used in electronic equipment, automobiles, aerospace, and other fields. Their performance directly affects the reliability and stability of electrical connections. Currently, terminal-type electrical connection components typically use copper or copper alloys as the base material. This is because copper alloys possess both excellent conductivity and mechanical strength, meeting the dual requirements of electrical transmission and structural support.

[0003] In actual service, terminals are exposed to complex environments for extended periods, making them susceptible to severe corrosion. Copper alloy substrates are prone to oxidation in humid environments and corrosive media, forming an oxide layer. They may also experience localized corrosion phenomena such as pitting and crevice corrosion. This corrosion can significantly increase the contact resistance of the terminals, and in severe cases, even cause electrical connection failure.

[0004] Currently, to improve the corrosion resistance of terminals, existing technologies often pursue increased coating density. However, this approach struggles to balance corrosion resistance, interfacial bonding reliability, and long-term service stability. Excessive coating density can exacerbate interfacial stress concentration, making coating failure more likely under complex operating conditions. Conversely, reducing coating density to alleviate stress fails to effectively block corrosive media, resulting in inadequate corrosion resistance.

[0005] Therefore, there is an urgent need to develop a new type of terminal that can effectively improve the corrosion resistance and structural reliability of the terminal without sacrificing conductivity and contact performance. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a corrosion-resistant terminal that achieves a synergistic improvement in corrosion resistance, interface bonding reliability, and electrical contact performance by constructing a multi-layer composite plating structure, thereby solving the problems of easy corrosion and plating peeling of terminals under complex working conditions in the prior art. At the same time, this invention will also provide a method for manufacturing the corrosion-resistant terminal.

[0007] To achieve the above and other related objectives, the present invention provides the following technical solutions: In a first aspect, the present invention provides a corrosion-resistant terminal comprising a substrate formed of a copper alloy, wherein a copper-based porous anchoring layer, a nickel-phosphorus dense barrier layer, and a noble metal contact layer are sequentially disposed on the surface of the substrate from the inside to the outside.

[0008] Furthermore, the substrate is made of brass, copper, or tin bronze, preferably C1100 copper or QSn6.5-0.1 tin bronze.

[0009] Furthermore, the surface roughness of the substrate needs to be controlled within Ra0.1-0.3μm to ensure the bonding effect of subsequent coatings.

[0010] Furthermore, the copper-based porous anchoring layer is formed on the surface of the copper alloy terminal substrate by composite electrodeposition, and has a controlled distribution of micropores inside, which are mainly non-through holes (blind holes) or low-connectivity holes.

[0011] Furthermore, the copper-based porous anchoring layer has a thickness of 5-15 μm, a microporosity of 3%-6%, and a micropore connectivity of ≤5%. If the microporosity is less than 3%, the mechanical interlocking effect with the nickel-phosphorus layer cannot be guaranteed; if the microporosity is greater than 6%, it will lead to a decrease in the strength of the anchoring layer itself, and the pores will be easily filled by corrosive media.

[0012] Wherein, the microporosity refers to the percentage of the pore area in the metallographic cross-section of the copper-based porous anchoring layer to the total cross-sectional area of ​​the anchoring layer. Preferably, a metallographic cross-section is prepared along the coating thickness direction of the terminal sample. After mounting, grinding, and polishing, at least five fields of view are randomly selected under a 500–2000x microscope or scanning electron microscope. The pore area is then segmented into a binarized image, and the area fraction is calculated. The average value is taken as the microporosity.

[0013] The micropore connectivity rate refers to the percentage of the total area of ​​pores that can form connected channels in the aforementioned cross-sectional image. "Connected channels" include: pores that are interconnected to form continuous channels, or pores that are connected to the outer surface of the anchoring layer and extend continuously along the thickness direction. A micropore connectivity rate ≤ 5% indicates that the anchoring layer pores are mainly non-penetrating blind pores or low-connectivity pores, making it difficult to form penetrating permeation channels.

[0014] Furthermore, the nickel-phosphorus dense barrier layer is formed by chemical plating, with a thickness of 8-20 μm, a phosphorus content of 8%-12% (medium phosphorus system), a porosity of ≤0.5%, and a pinhole rate of ≤0.3 pins / cm², and is used to prevent corrosive media from penetrating into the substrate.

[0015] Wherein: the porosity of the nickel-phosphorus dense barrier layer refers to the percentage of the area of ​​pores (including micropores, voids, and shrinkage cavities) in the metallographic cross-sectional image of the nickel-phosphorus dense barrier layer to the cross-sectional area of ​​the dense barrier layer. Preferably, after completing step S3, a metallographic cross-section is prepared along the coating thickness direction of the terminal sample. After mounting, grinding, and polishing, at least 5 fields of view are randomly selected under a 500–2000x optical microscope or scanning electron microscope. The pore area is binarized and the area fraction is calculated. The average value is taken as the porosity. The porosity ≤ 0.5% indicates that the volume fraction of pores inside the nickel-phosphorus layer is extremely low, which can provide a continuous and dense barrier channel.

[0016] The pinhole rate of the nickel-phosphorus dense barrier layer refers to the number of penetrating defects (pinholes / through-holes) per unit area that can lead to substrate exposure or allow corrosive media to reach the substrate, measured in units per cm². Preferably, the pinhole rate is determined using a colorimetric / electrochemical indicator method: after cleaning and drying the sample surface following step S3 with deionized water, an indicator solution is applied to a specified area (e.g., 1 cm²) or a short-term electrochemical colorimetric reaction is performed to induce localized colorimetric reactions or localized hydrogen evolution reactions at the penetrating defects; subsequently, the colorimetric or reaction points are counted under a 50–200x optical microscope, and the pinhole rate is calculated; to improve statistical reliability, it is preferable to randomly select at least three 1 cm² statistical areas on the same sample surface and take the average value. A pinhole rate ≤ 0.3 pinholes / cm² indicates that the number of penetrating defects is controlled, effectively inhibiting corrosive media from reaching the substrate through pinholes and causing pitting or sub-interface corrosion.

[0017] Furthermore, the precious metal contact layer is a gold layer or a silver layer. If it is a gold layer, the thickness is 0.3-1.0 μm (soft gold system, Vickers hardness HV≤120); if it is a silver layer, the thickness is 1.0-3.0 μm (cyanide-free system), used to provide stable electrical contact performance.

[0018] The above structure enables the copper-based porous anchoring layer to improve the bonding strength between the plating system and the copper alloy substrate (cross-cut test ≥ 4B grade) and buffer thermal stress, the nickel-phosphorus dense barrier layer to inhibit the inward propagation of corrosive media along plating defects, and the contact functional layer to ensure the conductivity (contact resistance ≤ 5mΩ) and contact reliability of the terminals.

[0019] A second aspect of the present invention provides a method for manufacturing a corrosion-resistant terminal as described above, comprising the following steps: S1. Pre-treat the substrate surface; S2. On the pretreated substrate surface, a copper-based porous anchoring layer is deposited by composite electrodeposition. During the composite electrodeposition process, copper-tin alloy powder is introduced into the electrodeposition solution and deposited with pulsed current or pulsed reverse current. The particle size, concentration and electrodeposition parameters of the copper-tin alloy powder are controlled to form micropores with non-through holes or low interconnection holes in the copper-based porous anchoring layer. S3. A nickel-phosphorus dense barrier layer is deposited on the surface of the copper-based porous anchoring layer using a chemical plating process. S4. On the surface of the nickel-phosphorus dense barrier layer, a gold or silver layer is deposited by electroplating to form a noble metal contact layer.

[0020] In step S1, the pretreatment includes sequentially performing degreasing and cleaning, oxide film removal, and surface activation treatment on the substrate surface. Specifically: Degreasing and cleaning include: immersing the substrate in an alkaline degreasing solution at 50-60℃ for 5-15 minutes, followed by ultrasonic-assisted cleaning (200-300W) to remove oil stains from the substrate surface. The alkaline degreasing agent consists of: 15-25g / L sodium hydroxide, 20-30g / L sodium carbonate, 10-15g / L trisodium phosphate, and 2-5g / L surfactant. The surfactant can be fatty alcohol polyoxyethylene ether.

[0021] The oxide film removal process includes: immersing the substrate in a micro-etching solution at room temperature for 10-30 seconds, followed by rinsing with deionized water 3-4 times. The micro-etching solution consists of 50-80 mL / L sulfuric acid and 30-50 mL / L hydrogen peroxide.

[0022] The surface activation treatment includes immersing the washed substrate in a 5-10 vol% sulfuric acid solution at room temperature for 30-60 seconds to activate the substrate surface, and then immediately rinsing it with deionized water to avoid secondary oxidation.

[0023] In step S2, the electrodeposition solution system is a cyanide-free sulfate system, which includes: 200-250 g / L copper sulfate, 50-80 g / L sulfuric acid, 50-100 mg / L chloride ions, and 1-3 mL / L brightener; the copper-tin alloy powder has a tin content of 10%-15%, a particle size of 0.2-1.5 μm, and a concentration of 8-15 g / L in the electrodeposition solution; before deposition, the electrodeposition solution is ultrasonically dispersed for 30 min (power 300 W) to ensure uniform dispersion.

[0024] The composite electrodeposition process includes: placing the pretreated substrate as the cathode into the electrodeposition tank, using a copper anode as the anode (e.g., a soluble copper anode consisting of a phosphor bronze plate or phosphor bronze ball loaded into a titanium basket), and applying a pulsed or reversed pulse current to perform electrodeposition, so as to form a microporous structure dominated by non-through holes or low-through-holes in the copper-based porous anchoring layer.

[0025] Pulse current parameters: Current density 1-3 A / dm 2 The pulse frequency is 500-2000Hz, the duty cycle is 30-60%, the deposition temperature is 25-40℃, and the deposition time is 15-40min.

[0026] Pulse reversal current parameters: Forward current density 2-4 A / dm 2 Reverse current density 0.5-1 A / dm 2 The pulse frequency is 500-1000Hz, the duty cycle is 30%-50%, the reversal period is 5-10s, the deposition temperature is 25-35℃, and the deposition time is 15-30min.

[0027] The periodic variation of pulsed current or pulsed reverse current causes periodic fluctuations in the instantaneous overpotential and concentration polarization at the cathode interface, thereby inducing the initiation and uniform dispersion of microscale vacancies within the deposition layer; simultaneously, the pulse intermittent phase promotes Cu² + Diffusion replenishment and re-nucleation facilitate the spatially discrete distribution of pores, inhibiting the continuous extension of pores along the thickness direction to form through channels. When pulsed reverse current is used, the reverse current selectively dissolves and levels local protrusions and weakly bonded areas on the deposition surface during the reverse cycle, reducing the probability of pores "connecting in series along the thickness direction," thus making the pore structure dominated by non-through blind pores or low-connectivity pores. After introducing copper-tin alloy powder, the powder forms dispersed heterogeneous nucleation and local shielding effects on the cathode surface, changing the local electric field and nucleation rate, causing pores to preferentially form discretely around the powder and be restricted by the subsequent copper deposition, further reducing the probability of pore-to-pore connectivity and regulating the pore morphology.

[0028] By adjusting the pulse frequency, duty cycle, and deposition time, the microporosity can be controlled within the range of 3%–6%. By adjusting the pulse reversal conditions (including forward current density, reverse current density, and reversal period), pore penetration and pore-to-pore connectivity are suppressed, so that the micropore connectivity rate is stably controlled at ≤5%. Furthermore, the concentration of copper-tin alloy powder is combined to synergistically regulate the pore spatial distribution and pore morphology, so as to balance the mechanical interlocking effect and the anti-permeability requirement.

[0029] The resulting copper-based porous anchoring layer has a thickness of 5-15 μm and a microporosity controlled at 3%-6%. The pores are primarily non-penetrating blind or low-connectivity pores. This porous structure allows for mechanical interlocking with the subsequent nickel-phosphorus dense barrier layer, improving interfacial bonding stability. It also prevents corrosive media from rapidly penetrating the substrate through through-pores, thus reducing the risk of pitting and sub-interfacial corrosion. The anchoring layer exhibits good compatibility with the copper alloy substrate in terms of material composition and thermal expansion behavior, effectively mitigating interfacial stress concentration caused by thermal cycling and mechanical loads.

[0030] In step S3, before chemical plating, the copper-based porous anchoring layer is pre-activated. The pre-activation treatment includes immersing the copper-based porous anchoring layer in a 1-5 vol% dilute hydrochloric acid or dilute sulfuric acid solution at room temperature for 10-30 seconds to remove the transient oxide film on the surface of the copper-based porous anchoring layer, followed by rinsing with deionized water.

[0031] In step S3, the composition of the chemical plating solution includes: nickel sulfate 20-30 g / L, sodium hypophosphite 30-40 g / L, sodium citrate 15-25 g / L, sodium acetate 10-15 g / L, and stabilizer (thiourea) 0.5-1 mg / L.

[0032] Electroless plating parameters: plating bath temperature 85-90℃, pH value 4.8-5.2, deposition time 20-40 min, continuous stirring during deposition (speed 100-200 r / min). After deposition, rinse 3 times with deionized water and keep warm at 120-150℃ for 30 min to improve coating density and adhesion.

[0033] In step S4, a surface activation treatment is performed before depositing the noble metal contact layer. The surface activation treatment includes immersing the surface in a 1–5 vol% dilute sulfuric acid or dilute hydrochloric acid solution at room temperature for 10–30 seconds to remove the transient oxide film. The surface is then rinsed with deionized water and immediately proceeds to the noble metal deposition step.

[0034] In step S4, select the appropriate precious metal coating type according to the usage scenario: If a gold plating layer is selected (suitable for frequent insertion / removal and high-reliability scenarios): an electroplating process is used, with a sulfite-based plating solution comprising: potassium gold cyanide 2-5 g / L, sodium sulfite 50-80 g / L, and trisodium citrate 20-30 g / L; current density 0.5-1 A / dm³. 2 At a temperature of 40-50℃ and a deposition time of 5-15 min, a soft gold layer with a thickness of 0.3-1.0 μm is obtained.

[0035] If a silver layer is chosen (suitable for low-cost, low-to-medium frequency plug-in / plug-out scenarios): a cyanide-free electroplating process is used, with a thiosulfate system as the plating solution, consisting of 10-15 g / L silver nitrate, 80-120 g / L sodium thiosulfate, 5-10 mL / L ammonia, and 0.1-0.3 g / L stabilizer; current density 1-2 A / dm³. 2 At a temperature of 25-35℃ and a deposition time of 10-30 min, a silver layer with a thickness of 1.0-3.0 μm is obtained.

[0036] After deposition, rinse three times with deionized water and dry at 60-80℃ for 10 minutes to ensure that there is no residual plating solution on the coating surface.

[0037] As described above, the corrosion-resistant terminal and its manufacturing method of the present invention have the following beneficial effects: 1. This invention achieves a synergistic effect in both structure and function of the plating system by setting a copper-based porous anchoring layer and a nickel-phosphorus dense barrier layer between the copper alloy substrate and the outer contact layer. The copper-based porous anchoring layer, through its controlled microporous structure, improves the mechanical bonding strength between the plating and the substrate and alleviates interfacial stress concentration caused by thermal cycling and mechanical loads, thereby reducing the risk of plating cracking and peeling. The nickel-phosphorus dense barrier layer possesses excellent density and barrier properties, effectively inhibiting the penetration of corrosive media into the substrate along micro-defects and significantly reducing the probability of downward corrosion. The gold or silver contact functional layer added on this basis ensures the conductivity and contact stability of the terminal without compromising the protective effect. Therefore, this invention can significantly improve the corrosion resistance life and long-term service reliability of terminals in complex environments such as high humidity and heat, and salt spray.

[0038] 2. The composite electrodeposition, electroless nickel-phosphorus plating, and precious metal electroplating processes used in this invention are all mature and controllable industrial-grade processes. No new special equipment is required. They can be implemented simply by adjusting the parameters on the existing terminal manufacturing production line. The process costs are low, the production efficiency is high, and they are suitable for large-scale industrial production. Attached Figure Description

[0039] Figure 1 The diagram shown is a structural schematic of the corrosion-resistant terminal disclosed in this invention.

[0040] Component designation explanation: 1. Matrix; 2. Copper-based porous anchoring layer; 3. Nickel-phosphorus dense barrier layer; 4. Noble metal contact layer. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0042] All samples used QSn6.5-0.1 tin bronze (size: 50mm × 10mm × 2mm) as the copper alloy substrate, with a surface roughness controlled at Ra = 0.2μm. The examples were prepared according to the technical solution of this invention, while the comparative examples were prepared using conventional processes or schemes lacking key structures / parameters.

[0043] Example 1 This embodiment provides a corrosion-resistant terminal, comprising a substrate 1 formed of a copper alloy. From the inside out, the surface of the substrate is sequentially disposed a copper-based porous anchoring layer 2, a nickel-phosphorus dense barrier layer 3, and a noble metal contact layer 4 (gold layer). The copper-based porous anchoring layer has a thickness of 10.5 μm, a microporosity of 4.2%, and a micropore connectivity of 2.0%. The nickel-phosphorus dense barrier layer has a thickness of 14 μm, a phosphorus content of 10.2%, a porosity of 0.18%, and a pinhole rate of 0.10 pinholes / cm². 2 The precious metal contact layer is a gold layer with a thickness of 0.65 μm.

[0044] Its manufacturing method includes the following steps: S1. Substrate surface pretreatment: Degreasing and cleaning include: placing the substrate in an alkaline degreasing solution (sodium hydroxide 20g / L, sodium carbonate 25g / L, trisodium phosphate 12g / L, surfactant 3g / L), immersing it at 55℃ for 8 minutes, and then ultrasonically assisted cleaning (power 250W) to remove oil stains from the surface of the substrate. The oxide film removal process includes: placing the substrate in a micro-etching solution (60 mL / L sulfuric acid and 40 mL / L hydrogen peroxide), immersing it at room temperature for 20 seconds, and rinsing it three times with deionized water; The surface activation treatment includes immersing the washed substrate in a 10 vol% dilute sulfuric acid solution for 40 seconds at room temperature to activate the substrate surface, and then immediately rinsing it with deionized water to avoid secondary oxidation.

[0045] S2. Preparation of copper-based porous anchoring layer by composite electrodeposition: The pretreated substrate is placed in the electrodeposition tank as the cathode, and a copper anode is used as the anode. Electrodeposition is performed by applying a pulsed reverse current. Electrodeposition solution: 220 g / L copper sulfate, 60 g / L sulfuric acid, 80 mg / L chloride ions, 2 mL / L brightener; with 12 g / L copper-tin alloy powder (12% Sn content). Pulse reversal parameters: Forward current density 3.0 A / dm 2 0.8A / dm in reverse 2 Frequency 800Hz, duty cycle 40%, inversion period 7s, temperature 30℃, time 22min.

[0046] The obtained copper-based porous anchoring layer has a thickness of 10.5 μm, a microporosity of 4.2%, and a micropore connectivity of 2.0%.

[0047] S3. Preparation of a dense nickel-phosphorus barrier layer by electroless plating: Pre-activation treatment: Immerse in a 2 vol% dilute sulfuric acid solution at room temperature for 20 seconds, then rinse thoroughly with deionized water; Chemical plating solution: Nickel sulfate 25g / L, sodium hypophosphite 35g / L, sodium citrate 20g / L, sodium acetate 12g / L, thiourea 0.8mg / L; Chemical plating parameters: 85℃, pH 5.0, 30 min, stirring at 150 r / min; rinsed with water 3 times, then kept at 120℃ for 30 min.

[0048] The obtained nickel-phosphorus dense barrier layer has a thickness of 14 μm, a phosphorus content of 10.2%, a porosity of 0.18%, and a pinhole rate of 0.10 pins / cm. 2 .

[0049] S4. Preparation of noble metal contact layer: The electroplating process is employed, with the gold plating solution consisting of potassium gold cyanide 3.5 g / L, sodium sulfite 65 g / L, and trisodium citrate 25 g / L. Electroplating parameters: 0.8A / dm 2 , 45℃, 10min.

[0050] The thickness of the obtained gold layer was 0.65 μm.

[0051] Example 2 This embodiment provides a corrosion-resistant terminal, comprising a substrate formed of a copper alloy. From the inside out, the surface of the substrate is sequentially formed with a copper-based porous anchoring layer, a nickel-phosphorus dense barrier layer, and a noble metal contact layer (silver layer). The copper-based porous anchoring layer has a thickness of 12.2 μm, a microporosity of 5.4%, and a micropore connectivity of 3.8%. The nickel-phosphorus dense barrier layer has a thickness of 11.5 μm, a phosphorus content of 9.0%, a porosity of 0.26%, and a pinhole rate of 0.20 pins / cm². 2 The noble metal contact layer is a silver layer with a thickness of 2.1 μm.

[0052] Its manufacturing method includes the following steps: S1. Substrate surface pretreatment: Degreasing and cleaning include: placing the substrate in an alkaline degreasing solution (sodium hydroxide 20g / L, sodium carbonate 25g / L, trisodium phosphate 12g / L, surfactant 3g / L), immersing it at 55℃ for 8 minutes, and then ultrasonically assisted cleaning (power 250W) to remove oil stains from the surface of the substrate. The oxide film removal process includes: placing the substrate in a micro-etching solution (60 mL / L sulfuric acid and 40 mL / L hydrogen peroxide), immersing it at room temperature for 20 seconds, and rinsing it three times with deionized water; The surface activation treatment includes immersing the washed substrate in a 10 vol% dilute sulfuric acid solution for 40 seconds at room temperature to activate the substrate surface, and then immediately rinsing it with deionized water to avoid secondary oxidation.

[0053] S2. Preparation of copper-based porous anchoring layer by composite electrodeposition: The pretreated substrate is placed in the electrodeposition tank as the cathode, and a copper anode is used as the anode. Electrodeposition is performed by applying a pulsed reverse current. Electrodeposition solution: copper sulfate 240 g / L, sulfuric acid 70 g / L, chloride ion 60 mg / L, brightener 1.5 mL / L; powder 10 g / L (Sn content 10%). Pulse parameters: Current density 2.0 A / dm 2 Frequency 1500 Hz, duty cycle 50%, temperature 32℃, time 28 min.

[0054] The obtained copper-based porous anchoring layer has a thickness of 12.2 μm, a microporosity of 5.4%, and a micropore connectivity of 3.8%.

[0055] S3. Preparation of a dense nickel-phosphorus barrier layer by electroless plating: Pre-activation treatment: Immerse in a 2 vol% dilute sulfuric acid solution at room temperature for 20 seconds, then rinse thoroughly with deionized water; Electroless plating solution: Nickel sulfate 22 g / L, sodium hypophosphite 32 g / L, sodium citrate 18 g / L, sodium acetate 10 g / L, thiourea 0.6 mg / L; Chemical plating parameters: 86℃, pH 5.1, 25 min, stirring at 120 r / min; 130℃ for 30 min.

[0056] The obtained nickel-phosphorus dense barrier layer has a thickness of 11.5 μm, a phosphorus content of 9.0%, a porosity of 0.26%, and a pinhole rate of 0.20 pins / cm. 2 .

[0057] S4. Preparation of noble metal contact layer: The electroplating process is employed, with the following silver electroplating solution: silver nitrate 12 g / L, sodium thiosulfate 100 g / L, ammonia water 7 mL / L, and stabilizer 0.2 g / L. Electroplating parameters: 1.5 A / dm 2 30℃, 18 min.

[0058] The thickness of the obtained silver layer was 2.1 μm.

[0059] Example 3 This embodiment provides a corrosion-resistant terminal, comprising a substrate formed of a copper alloy. From the inside out, the surface of the substrate is sequentially formed with a copper-based porous anchoring layer, a nickel-phosphorus dense barrier layer, and a noble metal contact layer (gold layer). The copper-based porous anchoring layer has a thickness of 9.3 μm, a microporosity of 3.6%, and a micropore connectivity of 1.4%. The nickel-phosphorus dense barrier layer has a thickness of 18.5 μm, a phosphorus content of 11.5%, a porosity of 0.12%, and a pinhole rate of 0.06 pins / cm². 2 The precious metal contact layer is a gold layer with a thickness of 0.55 μm.

[0060] Its manufacturing method includes the following steps: S1. Substrate surface pretreatment: Degreasing and cleaning include: placing the substrate in an alkaline degreasing solution (sodium hydroxide 20g / L, sodium carbonate 25g / L, trisodium phosphate 12g / L, surfactant 3g / L), immersing it at 55℃ for 8 minutes, and then ultrasonically assisted cleaning (power 250W) to remove oil stains from the surface of the substrate. The oxide film removal process includes: placing the substrate in a micro-etching solution (60 mL / L sulfuric acid and 40 mL / L hydrogen peroxide), immersing it at room temperature for 20 seconds, and rinsing it three times with deionized water; The surface activation treatment includes immersing the washed substrate in a 10 vol% dilute sulfuric acid solution for 40 seconds at room temperature to activate the substrate surface, and then immediately rinsing it with deionized water to avoid secondary oxidation.

[0061] S2. Preparation of copper-based porous anchoring layer by composite electrodeposition: The pretreated substrate is placed in the electrodeposition tank as the cathode, and a copper anode is used as the anode. Electrodeposition is performed by applying a pulsed reverse current. Electrodeposition solution: copper sulfate 210 g / L, sulfuric acid 55 g / L, chloride ion 90 mg / L, brightener 2.5 mL / L; powder 15 g / L (Sn content 15%). Pulse inversion parameters: Forward 3.5 A / dm 2 1.0 A / dm (reverse) 2 Frequency 600 Hz, duty cycle 35%, inversion period 5 s, temperature 28℃, time 20 min.

[0062] The obtained copper-based porous anchoring layer has a thickness of 9.3 μm, a microporosity of 3.6%, and a micropore connectivity of 1.4%.

[0063] S3. Preparation of a dense nickel-phosphorus barrier layer by electroless plating: Pre-activation treatment: Immerse in a 2 vol% dilute sulfuric acid solution at room temperature for 20 seconds, then rinse thoroughly with deionized water; Electroless plating solution: Nickel sulfate 30 g / L, sodium hypophosphite 40 g / L, sodium citrate 25 g / L, sodium acetate 15 g / L, thiourea 1.0 mg / L; Chemical plating parameters: 90℃, pH 4.9, 35 min, stirring at 180 r / min; 150℃ for 30 min.

[0064] The obtained nickel-phosphorus dense barrier layer has a thickness of 18.5 μm, a phosphorus content of 11.5%, a porosity of 0.12%, and a pinhole rate of 0.06 pins / cm². 2 .

[0065] S4. Preparation of noble metal contact layer: The electroplating process is employed, with the gold plating solution consisting of potassium gold cyanide 3.5 g / L, sodium sulfite 65 g / L, and trisodium citrate 25 g / L. Electroplating parameters: 0.6A / dm 2 , 40℃, 12min.

[0066] The thickness of the obtained gold layer was 0.55 μm.

[0067] Comparative Example 1 This comparative example provides a terminal comprising a substrate formed of a copper alloy. From the inside out, the surface of the substrate is sequentially disposed a copper-based anchoring layer, a nickel-phosphorus dense barrier layer, and a noble metal contact layer (silver layer). The copper-based anchoring layer has a thickness of 11.8 μm, a microporosity of 2.0%, and a micropore connectivity of 12.5%. The nickel-phosphorus dense barrier layer has a thickness of 11.2 μm, a phosphorus content of 9.1%, a porosity of 0.62%, and a pinhole rate of 1.10 pins / cm². 2 The noble metal contact layer is a silver layer with a thickness of 2.1 μm.

[0068] The manufacturing method of this comparative example differs from that of Example 2 only in that: S2. Still use copper sulfate / sulfuric acid system electrodeposition solution (copper sulfate 220g / L, sulfuric acid 60g / L, chloride ion 80mg / L, brightener 2mL / L), but do not add copper-tin alloy powder, and use DC constant current deposition (without pulse / pulse reversal). Take the other conditions as similar to those in Example 2, with current density and time, so that the thickness is comparable.

[0069] Performance testing The terminals manufactured in Examples 1-3 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 1.

[0070] Table 1. Performance Test Results

[0071] Test results show that in Comparative Example 1, the removal of key controls for powder composite and pulse / reverse led to a significant increase in connectivity, Ni-P pinhole rate, premature salt spray failure, and a significant deterioration in contact resistance after salt spray exposure. In contrast, this invention, by creating an anchoring layer with high microporosity but low connectivity, and by promoting a Ni-P layer with "low porosity and low pinhole rate," significantly extends salt spray corrosion resistance life, improves coating adhesion, and maintains low and stable contact resistance even in corrosive environments. In summary, this invention achieves a synergistic effect in both structure and function by incorporating a copper-based porous anchoring layer and a nickel-phosphorus dense barrier layer between the copper alloy substrate and the outer contact layer. The copper-based porous anchoring layer, through its controlled microporous structure, enhances the mechanical bond strength between the coating and the substrate and alleviates interfacial stress concentration caused by thermal cycling and mechanical loads, thereby reducing the risk of coating cracking and peeling. The nickel-phosphorus dense barrier layer possesses excellent density and barrier properties, effectively inhibiting the penetration of corrosive media along micro-defects into the substrate and significantly reducing the probability of under-interface corrosion. Furthermore, the non-penetrating pore structure of the copper-based composite porous anchoring layer prevents rapid penetration of corrosive media. The synergistic effect of the two layers significantly reduces the risk of pitting corrosion and under-interface corrosion. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0072] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A corrosion-resistant terminal, characterized in that, It includes a substrate formed of a copper alloy, wherein a copper-based porous anchoring layer, a nickel-phosphorus dense barrier layer and a noble metal contact layer are sequentially disposed on the surface of the substrate from the inside to the outside; The copper-based porous anchoring layer contains micropores, primarily non-through or low-connectivity pores, with a micropore rate of 3%-6% and a micropore connectivity rate of ≤5%. The nickel-phosphorus dense barrier layer has a porosity of ≤0.5% and a pinhole rate of ≤0.3 pinholes / cm². 2 .

2. The corrosion-resistant terminal according to claim 1, characterized in that, The thickness of the copper-based porous anchoring layer is 5-15 μm; the thickness of the nickel-phosphorus dense barrier layer is 8-20 μm; the noble metal contact layer is a gold layer or a silver layer, the thickness of the gold layer is 0.3-1.0 μm, and the thickness of the silver layer is 1.0-3.0 μm.

3. The corrosion-resistant terminal according to claim 1, characterized in that, The plating adhesion of the terminals meets the requirements of cross-cut test grade ≥4B, and the contact resistance is ≤5mΩ.

4. A method for manufacturing a corrosion-resistant terminal as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Pre-treat the substrate surface; S2. On the pretreated substrate surface, a copper-based porous anchoring layer is deposited by composite electrodeposition. During the composite electrodeposition process, copper-tin alloy powder is introduced into the electrodeposition solution and deposited with pulsed current or pulsed reverse current to form micropores with non-through holes or low interconnection holes in the copper-based porous anchoring layer. S3. A nickel-phosphorus dense barrier layer is deposited on the surface of the copper-based porous anchoring layer using a chemical plating process. S4. On the surface of the nickel-phosphorus dense barrier layer, a gold or silver layer is deposited by electroplating to form a noble metal contact layer.

5. The manufacturing method according to claim 4, characterized in that, In step S1, the pretreatment includes sequentially performing degreasing and cleaning, oxide film removal, and surface activation treatment on the substrate surface.

6. The manufacturing method according to claim 4, characterized in that, In step S2, the electrodeposition solution comprises: 200-250 g / L copper sulfate, 50-80 g / L sulfuric acid, 50-100 mg / L chloride ions, and 1-3 mL / L brightener; the concentration of copper-tin alloy powder in the electrodeposition solution is 8-15 g / L, and the tin content in the copper-tin alloy powder is 10%-15%.

7. The manufacturing method according to claim 4, characterized in that, Pulse current parameters: Current density 1-3 A / dm 2 Pulse frequency 500-2000Hz, duty cycle 30-60%, deposition temperature 25-40℃, deposition time 15-40min; Pulse reversal current parameters: Forward current density 2-4 A / dm 2 Reverse current density 0.5-1 A / dm 2 The pulse frequency is 500-1000Hz, the duty cycle is 30%-50%, the reversal period is 5-10s, the deposition temperature is 25-35℃, and the deposition time is 15-30min.

8. The manufacturing method according to claim 4, characterized in that, In step S3, the electroless plating solution includes: nickel sulfate 20-30 g / L, sodium hypophosphite 30-40 g / L, sodium citrate 15-25 g / L, sodium acetate 10-15 g / L, and stabilizer (thiourea) 0.5-1 mg / L.

9. The manufacturing method according to claim 4, characterized in that, Parameters for electroless plating: plating solution temperature 85-90℃, pH value 4.8-5.2, deposition time 20-40min, continuous stirring during deposition; After deposition, rinse three times with deionized water and keep warm at 120-150℃ for 30 minutes.

10. The manufacturing method according to claim 4, characterized in that, In step S4, when depositing the gold layer: an electroplating process is used, the plating solution system is a sulfite system, the composition of which includes: potassium gold cyanide 2-5 g / L, sodium sulfite 50-80 g / L, trisodium citrate 20-30 g / L; the current density is 0.5-1 A / dm³. 2 At a temperature of 40-50℃ and a deposition time of 5-15 min, a soft gold layer with a thickness of 0.3-1.0 μm is obtained. When depositing a silver layer: a cyanide-free electroplating process is used, and the plating solution system is a thiosulfate system, consisting of 10-15 g / L silver nitrate, 80-120 g / L sodium thiosulfate, 5-10 mL / L ammonia, and 0.1-0.3 g / L stabilizer; the current density is 1-2 A / dm³. 2 At a temperature of 25-35℃ and a deposition time of 10-30 min, a silver layer with a thickness of 1.0-3.0 μm is obtained.

Images