Plating layer structure, conductive terminal, preparation method of conductive terminal, electric connector and application of electric connector

Abstract

The invention discloses a coating structure, a conductive terminal, a preparation method of the conductive terminal, an electric connector and application of the electric connector, the coating structure sequentially comprises a copper coating, a palladium coating, a silver coating and a gold coating, the thickness of the silver coating is 80-200 mu, and the thickness of the gold coating is 1-10 mu; according to the plating layer structure, the nickel element is completely abandoned, and the sensitization risk of a traditional nickel plating layer is fundamentally eliminated; and the binding force between the copper plating layer and the silver plating layer can be remarkably enhanced through the palladium plating layer. The silver plating layer is adopted as the middle layer, and silver is low in hardness, easy to deform and higher in plasticity, so that the plating layer is effectively prevented from cracking in the compression test process, and the electrical contact stability is remarkably improved. And the gold plating layer is adopted as the outermost layer, so that the gold appearance requirement of the electric connector is met, and the electrical contact stability in the long-term use process is ensured. Therefore, according to the plating layer structure, the nickel element sensitization risk is eliminated, and meanwhile the appearance requirement, cost control, corrosion resistance and good electrical contact stability are considered.

Description

Technical Field

[0001] This invention belongs to the field of electrical connector technology, specifically relating to the field of conductive terminal plating technology, and particularly to a plating structure, conductive terminal and its preparation method, electrical connector and its application. Background Technology

[0002] With the rapid development of electronic technology, electrical connectors are widely used in electronic products to facilitate the exchange of information and data with external devices. Electrical connectors generally consist of an insulating body and conductive terminals for conduction. To meet the requirements of signal transmission and stable conductivity, it is necessary to ensure stable mating between the electrical connector and its mating connector, preventing poor conductivity and corrosion of the conductive terminals, which could lead to poor contact between the conductive terminals of the electrical connector and the mating connector. However, existing electronic products inevitably come into contact with sweat during actual use, and sweat contains various ions such as sodium ions. These components can create an electrochemical corrosion environment at the connector interface, leading to problems such as poor contact and signal attenuation in consumer electronics. To solve this problem, the industry typically electroplats a protective film on the conductive terminals to isolate corrosion, especially in the field of medical electronics. Such protective films not only need to have excellent corrosion resistance but also must meet special requirements for long-term skin contact (such as low allergenicity).

[0003] In the development of protective film technology, the industry has developed multi-layer electroplated protective film combination schemes. The first scheme uses a combination of copper (Cu) + nickel (Ni) + gold (Au), where the nickel layer, as an intermediate layer, effectively enhances the hardness and corrosion resistance of the coating. However, nickel is a common allergenic metal that easily triggers skin allergic reactions, a characteristic that makes it unsuitable for environmental protection requirements and application standards in the medical electronics field. To avoid the allergenicity problem of nickel, the second scheme adopts a nickel-free design, namely a combination structure of substrate + copper (Cu) + copper-tin-zinc (CuSnZn) + gold (Au). Although this solves the allergy problem, the high hardness and poor ductility of the CuSnZn alloy make it prone to coating cracking during subsequent compression, ultimately leading to a decrease in corrosion resistance. The third scheme uses a combination of copper (Cu) + silver (Ag) + gold (Au) + platinum (Pt) / rhodium (Rh). This structure significantly improves the wear resistance and oxidation resistance of the coating by adding a precious metal layer; however, its complex process requirements and high cost make it difficult to apply on a large scale in the cost-sensitive consumer electronics field.

[0004] Therefore, there is an urgent need for a plating structure, conductive terminals and their preparation methods, electrical connectors and their applications to address the shortcomings of existing technologies. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a plating structure, a conductive terminal and its preparation method, an electrical connector and its application. This plating structure completely eliminates the risk of nickel sensitization while taking into account appearance requirements, cost control, corrosion resistance and good electrical contact stability.

[0006] To achieve the above objectives, the first aspect of the present invention provides a coating structure comprising, in sequence, a copper coating, a palladium coating, a silver coating, and a gold coating, wherein the thickness of the silver coating is 80~200μ" and the thickness of the gold coating is 1~10μ".

[0007] Compared to existing technologies, this invention completely eliminates the use of nickel (Ni), fundamentally eliminating the sensitization risk of traditional nickel plating. The plating structure of this invention is particularly suitable for medical electronic devices and wearable products that come into prolonged contact with the skin (such as smart bracelets and VR headsets). The palladium (Pd) plating, as a transition layer, not only possesses excellent biocompatibility and corrosion resistance but also significantly enhances the bonding force between the copper (Cu) plating and the silver (Ag) plating, thereby improving the overall stability and electrical contact stability of the plating structure. Using a silver (Ag) plating as the intermediate layer, silver's low hardness, high variability, and greater plasticity result in excellent performance in post-process stress applications (such as riveting and dotting), effectively preventing cracking during compression testing and significantly improving electrical contact stability. Using a gold (Au) plating as the outermost layer not only meets the gold appearance requirements of electrical connectors but also ensures excellent conductivity and oxidation resistance, guaranteeing electrical contact stability during long-term use. Therefore, the coating structure of the present invention completely eliminates the risk of nickel sensitization while taking into account appearance requirements, cost control, corrosion resistance and good electrical contact stability.

[0008] Furthermore, the thickness of the copper plating layer of the present invention is less than or equal to 200 μ". Specifically, the thickness of the copper plating layer may be, but is not limited to, 200 μ", 150 μ", 100 μ", 50 μ", or 25 μ".

[0009] Furthermore, the thickness of the palladium coating of the present invention is greater than or equal to 5 μ". Specifically, the thickness of the palladium coating may be, but is not limited to, 5 μ", 8 μ", 12 μ", 15 μ", 18 μ", 21 μ", 25 μ", or 30 μ".

[0010] Furthermore, the thickness of the silver plating layer of the present invention can specifically be, but is not limited to, 80 μ", 100 μ", 120 μ", 150 μ", 180 μ", 190 μ", and 200 μ". During the research process, the inventors of the present invention discovered that if the thickness of the silver plating layer is <80 μ", stress concentration during compression testing can easily lead to cracking of the plating structure; if the thickness of the silver plating layer is >200 μ", the softness of silver reduces the structural rigidity. Therefore, by controlling the thickness of the silver plating layer within the range of 80~200 μ", the silver plating layer can effectively disperse stress through plastic flow during compression deformation, preventing cracks from propagating to the outer gold plating layer and maintaining the overall structural stability, thereby significantly improving electrical contact stability. Preferably, the thickness of the silver plating layer is 100~150 μ".

[0011] Furthermore, the thickness of the gold plating layer in this invention can be, but is not limited to, 1 μ", 3 μ", 5 μ", 7 μ", or 10 μ". During processing, the silver plating layer, due to its low hardness, easily forms micropores on its surface. When the thickness of the gold plating layer is 1~10 μ", the gold plating layer can completely cover the micropores of the silver plating layer, thereby forming a dense metal barrier, preventing the penetration of corrosive media such as sweat, further improving corrosion resistance, and thus ensuring electrical contact stability during long-term use. Preferably, the thickness of the gold plating layer is 2~7 μ".

[0012] Accordingly, a second aspect of the present invention provides a conductive terminal comprising a substrate and the aforementioned plating structure formed on the substrate, wherein a copper plating layer is located between the substrate and a palladium plating layer. This conductive terminal has a gold-colored appearance, low allergenicity, good corrosion resistance, and stable electrical contact.

[0013] Furthermore, the substrate of the present invention is one of nickel-based alloys, copper alloys, and titanium alloys.

[0014] Accordingly, a third aspect of the present invention provides a method for preparing a conductive terminal, comprising the steps of: S1. Pretreatment of the substrate; S2. Activate the substrate; S3. A copper plating layer is deposited on the surface of the substrate after step S2. S4. Plate a palladium plating layer onto the surface of the copper plating layer; S5. Plate a layer of silver onto the surface of the palladium plating layer; S6. Apply a gold plating layer to the surface of the silver plating layer; S7. Post-processing is performed after step S6.

[0015] Further, the pretreatment in step S1 includes: (1) ultrasonic vibration treatment with acid desiccant; (2) rinsing with water; (3) dehydration; (4) replacing with new acid desiccant and repeating the above steps (1) to (3); (5) ultrasonic vibration treatment with degreasing solution, followed by rinsing with water and dehydration treatment.

[0016] Furthermore, the present invention employs electroplating methods to plate copper, palladium, silver, and gold. The specific electroplating processes are well known to those skilled in the art, and therefore will not be described in detail here.

[0017] Furthermore, the post-processing in step S7 includes: sequentially performing surface sealing, water washing, and drying.

[0018] Accordingly, a fourth aspect of the present invention provides an electrical connector, including a housing, within which conductive terminals for conducting electricity or transmitting signals are installed. The conductive terminals are the conductive terminals mentioned above or conductive terminals prepared by the aforementioned method. This electrical connector exhibits low allergenicity, good corrosion resistance, and excellent electrical contact stability.

[0019] Accordingly, a fifth aspect of the present invention provides an application of the aforementioned electrical connector in wearable products.

[0020] Furthermore, wearable products can include, but are not limited to, watches, wristbands, Bluetooth headsets, and VR devices. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the conductive terminal in Example 1.

[0022] Figure 2 This is a schematic diagram of the conductive terminal in Comparative Example 1.

[0023] Figure 3 The images are SEM images of the conductive terminals of Example 1 after 10,000 compression tests were performed continuously at different magnifications.

[0024] Figure 4 The images are SEM images of the conductive terminals of Example 2 after 10,000 compression tests were performed continuously at different magnifications. Detailed Implementation

[0025] To better illustrate the purpose, technical solution, and beneficial effects of this invention, the invention will be further described below in conjunction with specific embodiments and accompanying drawings. It should be noted that the methods described below are further explanations of this invention and should not be construed as limiting it.

[0026] Example 1 This embodiment provides an electrical connector, which includes a housing and conductive terminals for conducting electricity or transmitting signals are installed inside the housing.

[0027] Please refer to Figure 1 The conductive terminal 12 in this embodiment includes a substrate 121 and a plating structure formed on the substrate 121. The plating structure consists of a copper plating layer 122, a palladium plating layer 123, a silver plating layer 124, and a gold plating layer 125 in sequence. The copper plating layer 122 is located between the substrate 121 and the palladium plating layer 123. The substrate 121 is a copper alloy. The thickness of the copper plating layer 122 is 180 μ", the thickness of the palladium plating layer 123 is 10 μ", the thickness of the silver plating layer 124 is 100 μ", and the thickness of the gold plating layer 125 is 2 μ".

[0028] The method for preparing the conductive terminal 12 in this embodiment includes the following steps: S1. The substrate 121 is subjected to ultrasonic vibration treatment with acid degreasing solution, rinsed with water and dehydrated. Then, the substrate is subjected to ultrasonic vibration treatment with acid degreasing solution, rinsed with water and dehydrated. Then, the substrate is subjected to ultrasonic vibration treatment with degreasing solution, rinsed with water and dehydrated. The acid degreasing solution is an acidic degreasing agent produced by the manufacturer Zhenbo Hardware Chemical, and the degreasing solution is a degreasing powder product produced by the manufacturer Zhenbo Hardware Chemical. S2. The substrate 121 is subjected to ultrasonic vibration and water rinsing with 50g / L of organic weak acid, and then subjected to ultrasonic vibration treatment, water rinsing and dehydration with 20% sulfuric acid. S3. Electroplating gold onto the surface of the substrate after step S2 to form a copper plating layer 122. S4. Electroplating palladium onto the surface of copper plating layer 122 to form a palladium plating layer 123; S5. Electroplating silver onto the surface of palladium plating 123 to form a silver plating layer 124; S6. Electroplating gold onto the surface of the silver plating layer 124 to form a gold plating layer 125; S7. After step S6, perform sealing, washing, and drying.

[0029] Example 2 Example 2 is basically the same as Example 1, except that the thickness of the copper plating layer 122 is 150 μ", the thickness of the palladium plating layer 123 is 15 μ", the thickness of the silver plating layer 124 is 150 μ", and the thickness of the gold plating layer 125 is 6 μ".

[0030] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the thickness of the silver plating layer 124 is 50 μm.

[0031] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that the thickness of the gold plating layer 125 is 0.6 μm.

[0032] Comparative Example 3 Please refer to Figure 2 Comparative Example 3 is basically the same as Example 1, except that: in addition to the gold plating layer 125', Comparative Example 3 also includes a platinum-ruthenium alloy plating layer 126' with a thickness of 15 μm; after step S6 of the method for preparing the conductive terminal 12' of Comparative Example 3, a platinum-ruthenium alloy is electroplated on the surface of the gold plating layer 125' to form a platinum-ruthenium alloy plating layer 126'.

[0033] The corrosion resistance of the conductive terminals of Examples 1-2 and Comparative Examples 1-3 was tested by salt spray test; the test results are shown in Table 1.

[0034] Salt spray test conditions: In a specific salt spray test chamber, a salt solution containing (5±0.5)% sodium chloride and with a pH value of 6.5~7.2 is sprayed through a spray device, allowing the salt spray to settle onto the test specimen. After 120 hours, the sample is immersed in tap water below 38℃ for five minutes, and the NaCl deposits on the sample surface are removed with a soft brush. After natural recovery at room temperature, the surface condition of the sample is observed. No damage, deformation, oxidation, discoloration, or other abnormalities indicate that the corrosion resistance is qualified. The appearance color of the conductive terminals after the salt spray test is also recorded. The test chamber temperature should be (35±2)℃, humidity greater than 95%, and the mist drop rate 1~2mL / 80cm. 2 / hr, nozzle pressure is 78.5~137.3kPa (0.8~1.4kgf / cm). 2 ).

[0035] The lifetime of the conductive terminals in Examples 1-2 and Comparative Examples 1-3 was tested using lifetime testing. The test results are shown in Table 2 and... Figures 3-4 As shown.

[0036] Life test: Before testing, the elastic force and contact resistance values ​​of the test samples were measured and recorded. The samples were then installed in a spring life tester and subjected to 10,000 compression tests at a test speed of 10 mm / s and a test stroke of 0.55 mm. After the test, the samples were checked for abnormalities such as compression deformation, needle shrinkage, or spring breakage, and the elastic force and contact resistance values ​​were remeasured. The judgment criteria are as follows: Appearance: No defects such as needle shrinkage, spring deformation, or loss of compression function are allowed; Performance: The elastic force value must be between 35g and 55g (at a working height of 3.45 mm), and the contact resistance value must be ≤200 mΩ (at a working height of 3.45 mm). If both of the above requirements are met, it is judged as "OK"; if any one fails to meet the requirements, it is judged as "NG". Simultaneously, a scanning electron microscope was used to observe the surface of the products after the tests in Examples 1 and 2, and the results are as follows. Figures 3-4 As shown, from Figures 3-4 As can be seen, after 10,000 compression tests, there are no cracks on the product surface.

[0037] Table 1

[0038] Table 2

[0039] A comparison of Example 1 and Comparative Example 1 shows that when the thickness of the silver plating layer is controlled within the range of 80~200 μm, the silver plating layer can effectively disperse stress through plastic flow during compression. This prevents cracks from propagating to the outer gold plating layer and maintains the stability of the overall structure, thereby significantly improving the electrical contact stability of the product during use. Furthermore, if the silver plating layer is thin (less than 80 microinches), a large number of micropores exist on the surface. Even with an outer gold plating layer, these pores can become channels for corrosive media to penetrate, thus corroding the substrate. Specifically, when the substrate is a copper alloy, the corrosion products will appear as a copper-green color on the workpiece surface, indicating that the substrate has been corroded.

[0040] Comparing Example 1 and Comparative Example 2, it can be seen that during the processing, the silver plating layer is prone to forming micropores on its surface due to its low hardness. When the thickness of the gold plating layer is 1~10μ", the gold plating layer can completely cover the micropores on the 80~200μ" thick silver plating layer, thereby forming a dense metal barrier, preventing the penetration of corrosive media such as sweat, further improving corrosion resistance, and thus ensuring the electrical contact stability during long-term use.

[0041] Comparing Example 1 and Comparative Example 3, it can be seen that although introducing a platinum-ruthenium alloy coating on the outside of the gold coating can further improve the corrosion resistance, the hardness of the rhodium-platinum alloy is much higher than that of the gold coating. This hardness difference will produce obvious stress concentration during continuous compression, which will damage the plasticity of the silver coating. As a result, it is easy to cause poor electrical contact stability after 10,000 compression tests.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A coating structure, characterized in that, The coating consists of a copper plating layer, a palladium plating layer, a silver plating layer, and a gold plating layer, in that order. The thickness of the silver plating layer is 80~200μ", and the thickness of the gold plating layer is 1~10μ".

2. The coating structure as described in claim 1, characterized in that, The thickness of the copper plating layer is less than or equal to 200 μm.

3. The coating structure as described in claim 1, characterized in that, The thickness of the palladium coating is greater than or equal to 5 μm.

4. The coating structure as described in claim 1, characterized in that, The thickness of the silver plating layer is 100~150μ".

5. The coating structure as described in claim 1, characterized in that, The thickness of the gold plating layer is 2~7μ".

6. A conductive terminal, characterized in that, The invention includes a substrate and a plating structure as described in any one of claims 1 to 5 formed on the substrate, wherein the copper plating is located between the substrate and the palladium plating.

7. The conductive terminal as described in claim 6, characterized in that, The substrate is one of nickel-based alloys, copper alloys, and titanium alloys.

8. The method for preparing a conductive terminal as described in claim 7, characterized in that, step include: S1. Pretreatment of the substrate; S2. Activate the substrate; S3. A copper plating layer is deposited on the surface of the substrate after step S2. S4. A palladium plating layer is deposited on the surface of the copper plating layer; S5. A silver plating layer is deposited on the surface of the palladium plating layer; S6. Plate a gold plating layer onto the surface of the silver plating layer; S7. Post-processing is performed after step S6.

9. An electrical connector, comprising a housing, wherein conductive terminals for conducting electricity or transmitting signals are mounted within the housing, characterized in that, The conductive terminal is a conductive terminal as described in any one of claims 6 to 7 or a conductive terminal prepared by the method described in claim 8.

10. An application of an electrical connector in wearable products, characterized in that, The electrical connector is the electrical connector as described in claim 9.

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