Preparation method of gradient composite coating gold-silver alloy electroplating structure

Abstract

The invention relates to a preparation method of a gradient composite coating gold-silver alloy electroplating structure. The method comprises the following steps: cleaning a substrate part to remove an oxide layer; an electroplating solution is prepared according to the molar concentration ratio of gold salt to silver salt being 1: 9, 2: 8 or 3: 7, and a gold-silver alloy layer is formed through electroplating under the conditions of specific current density, flow and shaking frequency; transferring to a gold-palladium alloy electroplating bath, and controlling the palladium content to be 0.5-1wt% through an independent palladium salt supplementing system to form a gold-palladium alloy middle layer with the thickness of 0.2 mu m; transferring to a pure gold electroplating bath to form a pure gold outer layer with the thickness of not less than 0.8 mu m; and finally, the workpiece is soaked in an organic solution containing 0.1-0.5 wt% of a benzotriazole derivative to be subjected to grain boundary passivation treatment. The gradient composite coating structure prepared through the method has excellent oxidation resistance and electric contact performance, is low in surface roughness and is suitable for protection of the contact surface of an electronic component.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a gradient composite plated gold-silver alloy electroplated structure. BACKGROUND

[0002] With the rapid development of the electronic industry, the contact performance and reliability of electronic components are constantly improving. Metal plating, as a surface treatment technology for key components such as electronic connectors, switches, and integrated circuit packaging, directly affects the service life and reliability of electronic products. Among various noble metal platings, gold plating is widely used in high-end electronic products due to its excellent electrical conductivity, oxidation resistance, and chemical stability. However, pure gold plating is costly and has low hardness and insufficient wear resistance, limiting its application in certain fields.

[0003] Gold-silver alloy plating, as an important alternative, combines the oxidation resistance of gold and the excellent electrical conductivity of silver, while reducing costs, and has therefore received extensive attention. CN117646259B discloses a method for preparing a gold-silver alloy plating layer by periodically switching between low and high current density intervals to solve the technical problem of random differences in gold content in gold-silver alloy plating layers at different positions caused by photoresist openings.

[0004] However, the gold-silver alloy electroplated structure in the prior art still has some problems. First, traditional gold-silver alloy electroplated layers are prone to oxidation and corrosion during long-term use, especially in sulfur-containing environments, where silver easily reacts with sulfides to form silver sulfide, leading to degradation of the plating layer performance. Second, a single-component gold-silver alloy plating layer cannot simultaneously meet multiple performance requirements such as high electrical conductivity, good oxidation resistance, and wear resistance.

[0005] Therefore, how to develop a gold-silver alloy electroplated structure with stable structure and balanced performance is a technical problem to be solved. SUMMARY

[0006] The purpose of the present application is to solve the above problems in the prior art and provide a preparation method of a gradient composite plated gold-silver alloy electroplated structure, which achieves better oxidation resistance and improves the structural stability of the electroplated layer. This purpose is achieved as follows:

[0007] The application provides a preparation method of a gradient composite plated gold-silver alloy electroplating structure, and has the characteristics that S1, the substrate is cleaned and the oxide layer is removed, a plating solution is prepared according to a molar concentration ratio of gold salt to silver salt of 1:9, 2:8 or 3:7, gold-silver alloy layers are formed by electroplating under the conditions of a current density of 0.2-0.8 ASD, a plating solution flow rate of 10-15 L / min and a substrate shaking frequency of 10-30 Hz for 1000-2400 seconds; S2, the substrate is transferred to a gold-palladium alloy electroplating tank, palladium salt is continuously supplemented into the electroplating tank through an independent palladium salt supplementing system, the palladium content in the deposited gold-palladium alloy layer is 0.5-1 wt%, the current density is controlled to be 0.4-0.7 ASD, and a gold-palladium alloy intermediate layer with a thickness of 0.2 μm is deposited; S3, the product is transferred to a pure gold electroplating tank, electroplating is carried out under the condition of a current density of 0.3-0.6 ASD for 100-400 seconds, a pure gold outer layer with a thickness of not less than 0.8 μm is formed, the workpiece is immersed in an organic solution containing 0.1-0.5 wt% of a benzotriazole derivative, and grain boundary passivation treatment is carried out in a constant temperature tank at 40-60°C, and the stability of the solution temperature is maintained through a constant temperature circulation system.

[0008] Further, the gold salt used in the plating solution is sodium chloroaurate, and the silver salt is silver nitrate.

[0009] Further, the shaking mode of the substrate in the electroplating process is horizontal reciprocating shaking, and the shaking frequency is 20 Hz.

[0010] Further, the gold-silver alloy electroplating solution further contains an organic complexing agent and a surfactant, which are used to improve the uniformity and adhesion of the plated layer.

[0011] Further, the gold-palladium alloy electroplating tank uses a constant current source power supply, and the electroplating process is monitored in real time through an online conductivity and pH monitoring system.

[0012] Further, the molar ratio of gold to palladium in the gold-palladium alloy layer is 9:1 to 4:1.

[0013] Further, the pure gold electroplating solution is a cyanide electroplating system containing sodium chloroaurate, and the plating solution temperature is controlled to be 45-55°C.

[0014] Further, the surface roughness Ra of the pure gold outer layer is not greater than 0.2 μm, so as to improve the oxidation resistance and electrical contact performance.

[0015] Further, the benzotriazole derivative is methyl benzotriazole or hydroxy benzotriazole.

[0016] Further, the duration of the grain boundary passivation treatment is 5-15 minutes.

[0017] Compared with the prior art, the beneficial effects of the present application are: through the gradient composite coating structure design, the effective combination of high conductivity and oxidation resistance is realized, the gold-silver alloy layer provides good conductivity, the gold-palladium alloy intermediate layer enhances the structural stability, and the pure gold outer layer provides excellent oxidation resistance.

[0018] The present application effectively prevents the oxidation corrosion of the coating during use through the grain boundary passivation treatment, and the accurate control of the surface roughness of the pure gold outer layer improves its oxidation resistance and electrical contact performance.

[0019] Through accurate control of the electroplating parameters and additives, the uniformity and adhesion of the coating are improved, and the online monitoring system ensures the stability and controllability of the electroplating process, thereby solving the problem of insufficient structural stability of the electroplating layer in the prior art, so that the prepared gradient composite coating gold-silver alloy electroplating structure can simultaneously meet the requirements of high conductivity and oxidation resistance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a flowchart of a preparation method of a gradient composite coating gold-silver alloy electroplating structure. DETAILED DESCRIPTION

[0021] In order to deepen the understanding of the present application, the present application will be further described in combination with examples and drawings, and the examples are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0022] Example 1

[0023] Please refer to Figure 1 The present application provides a preparation method of a gradient composite coating gold-silver alloy electroplating structure, which comprises the following steps:

[0024] Step 1: immerse the substrate to be electroplated, such as a copper alloy connector, in an alkaline cleaning solution at a temperature of 60℃ for 5 minutes for preliminary cleaning, then rinse with deionized water for 3 times, each time for 30 seconds, then immerse the substrate in a 5% sulfuric acid solution at room temperature for 2 minutes to remove the surface oxide layer, and finally rinse with deionized water for 5 times, each time for 30 seconds, until the pH value approaches neutral, to ensure that the substrate surface is clean and free of contaminants.

[0025] Step two: The plating solution is prepared according to a molar concentration ratio of gold salt to silver salt of 2:8. Specifically, sodium chloroaurate is used as the gold salt, and silver nitrate is used as the silver salt. An organic complexing agent, such as sodium citrate with a concentration of 25 g / L, and a surfactant, such as sodium dodecyl sulfate with a concentration of 0.5 g / L, are added to the plating solution to improve the uniformity and adhesion of the plating layer. The treated substrate is placed in the plating tank, and the current density is set to 0.5 ASD, the plating solution flow rate is 12 L / min, and the substrate is shaken in a horizontal reciprocating manner with a shaking frequency of 20 Hz. The plating is carried out under these conditions for 1800 seconds to form a gold-silver alloy layer with a thickness of about 1.5 μm. During the plating process, the temperature of the plating solution is maintained at 40°C, which is monitored and adjusted in real time by a temperature control system.

[0026] Step three: The substrate with the gold-silver alloy layer is removed from the plating tank, rinsed with deionized water for 3 times, each for 30 seconds, and then transferred to a gold-palladium alloy plating tank. The gold-palladium alloy plating tank uses a constant current source power supply, and the plating process is monitored in real time by an online conductivity and pH monitoring system to ensure the stability of the plating solution. A separate palladium salt supplement system is used to continuously supplement palladium salt to the plating tank, so that the palladium content in the deposited gold-palladium alloy layer is controlled at 0.8 wt%, and the molar ratio of gold to palladium is 7:1. The current density is controlled at 0.5 ASD, the plating solution temperature is 50°C, and the plating time is 600 seconds to form a gold-palladium alloy intermediate layer with a thickness of 0.2 μm.

[0027] Step four: The product with the gold-palladium alloy intermediate layer is removed from the plating tank, rinsed with deionized water for 3 times, each for 30 seconds, and then transferred to a pure gold plating tank. The pure gold plating solution is a cyanide plating system containing sodium chloroaurate, and the plating solution temperature is controlled at 50°C. The plating is carried out at a current density of 0.4 ASD for 250 seconds to form a pure gold outer layer with a thickness of 1.0 μm. By precisely controlling the plating parameters, the surface roughness Ra of the pure gold outer layer is ensured to be not greater than 0.2 μm to improve its oxidation resistance and electrical contact performance.

[0028] Step five: The workpiece with the three-layer plating is removed from the pure gold plating tank, rinsed with deionized water for 5 times, each for 30 seconds, and then immersed in an ethanol solution containing 0.3 wt% of methyl benzotriazole for grain boundary passivation treatment in a constant temperature oven at 50°C for 10 minutes. The temperature stability of the solution is maintained by a constant temperature circulation system, and the temperature fluctuation is controlled within ±1°C. After the passivation treatment is completed, the workpiece is taken out, rinsed with deionized water for 3 times, each for 30 seconds, and then dried in an oven at 60°C for 30 minutes.

[0029] The gradient composite plated gold-silver alloy plating structure prepared by the above steps has excellent corrosion resistance, electrical conductivity and oxidation resistance. The gold-silver alloy layer provides good basic electrical conductivity, the gold-palladium alloy intermediate layer enhances the stability and anti-diffusion ability of the structure, and the pure gold outer layer provides excellent oxidation resistance and contact reliability. The grain boundary passivation treatment further improves the corrosion resistance of the plating layer, prolonging the service life of the product.

[0030] Example two

[0031] A method for preparing a gradient composite plated gold-silver alloy plating structure, comprising the following steps:

[0032] Step one: immerse the substrate to be plated in an alkaline cleaning solution, with a temperature of 65°C and an immersion time of 4 minutes, for preliminary cleaning; then rinse with deionized water for 3 times, each for 30 seconds; then immerse the substrate in a 6% sulfuric acid solution, with a temperature of room temperature and an immersion time of 1.5 minutes, to remove the surface oxide layer; finally, rinse with deionized water for 5 times, each for 30 seconds, until the pH value is close to neutral, to ensure that the substrate surface is clean and free of contaminants.

[0033] Step two: prepare the plating solution according to the molar concentration ratio of gold salt to silver salt as 1:9, specifically using sodium chloroaurate as the gold salt and silver nitrate as the silver salt. Add organic complexing agents, such as 30g / L of EDTA disodium salt, and surfactants, such as 0.8g / L of polyethylene glycol, to the plating solution to improve the uniformity and adhesion of the plating layer. Place the treated substrate in the plating tank, set the current density to 0.3 ASD, the plating solution flow rate to 10 L / min, and the substrate to move in a horizontal reciprocating manner with a shaking frequency of 20 Hz. Under these conditions, electroplate for 2400 seconds to form a gold-silver alloy layer with a thickness of about 2.0 μm. During the plating process, the temperature of the plating solution is maintained at 42°C, which is monitored and adjusted in real time by a temperature control system.

[0034] Step three: remove the substrate with the completed gold-silver alloy layer plating from the plating tank, rinse with deionized water for 3 times, each for 30 seconds; then transfer it to the gold-palladium alloy plating tank. The gold-palladium alloy plating tank uses a constant current source power supply, which is monitored in real time by an online conductivity and pH monitoring system during the plating process to ensure the stability of the plating solution performance. A separate palladium salt supplement system is used to continuously supplement palladium salt to the plating tank, so that the palladium content in the deposited gold-palladium alloy layer is controlled at 0.5wt%, and the molar ratio of gold to palladium is 9:1. The current density is controlled at 0.6 ASD, the plating solution temperature is 48°C, and the plating time is 550 seconds, to deposit a gold-palladium alloy intermediate layer with a thickness of 0.2 μm.

[0035] Step four: The product of the completed gold-palladium alloy interlayer plating is taken out of the plating bath, rinsed with deionized water for 3 times, 30 seconds each time; and then transferred to a pure gold plating bath. The pure gold plating solution is a cyanide plating system containing sodium chloroaurate, and the plating solution temperature is controlled at 48°C. The plating is performed at a current density of 0.5 ASD for 200 seconds to form a pure gold outer layer with a thickness of 0.9 μm. By precisely controlling the plating parameters, the surface roughness Ra of the pure gold outer layer is ensured to be no more than 0.15 μm to improve its oxidation resistance and electrical contact performance.

[0036] Step five: The product of the completed three-layer plating is taken out of the pure gold plating bath, rinsed with deionized water for 5 times, 30 seconds each time; and then the product is immersed in an isopropyl alcohol solution containing 0.2 wt% hydroxybenzotriazole for grain boundary passivation treatment in a constant temperature bath at 45°C for 8 minutes. The temperature stability of the solution is maintained by a constant temperature circulation system, and the temperature fluctuation is controlled within ±1°C. After the passivation treatment is completed, the product is taken out, rinsed with deionized water for 3 times, 30 seconds each time, and then dried in an oven at 55°C for 35 minutes.

[0037] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and all such modifications or replacements should be covered within the scope of the claims of the present application.

Claims

1. A method for preparing a gradient composite gold-silver alloy electroplating structure, characterized in that: The method comprises the following steps: S1, cleaning the substrate, removing the oxide layer, preparing an electroplating solution according to a molar concentration ratio of gold salt to silver salt of 1:9, 2:8 or 3:7, and electroplating for 1000 to 2400 seconds under the conditions of a current density of 0.2 to 0.8 ASD, an electroplating solution flow rate of 10 to 15 L / min, and a substrate shaking frequency of 10 to 30 Hz to form a gold-silver alloy layer; S2, transferring the substrate to a gold-palladium alloy electroplating tank, and continuously replenishing palladium salt into the electroplating tank through an independent palladium salt replenishing system to make the palladium content in the deposited gold-palladium alloy layer The gold-palladium alloy intermediate layer with a thickness of 0.2 μm is deposited at a current density of 0.4 to 0.7 ASD; S3, the product is transferred to a pure gold electroplating tank, electroplated for 100 to 400 seconds at a current density of 0.3 to 0.6 ASD to form a pure gold outer layer with a thickness of not less than 0.8 μm, and the workpiece is immersed in an organic solution containing 0.1 to 0.5 wt% of a benzotriazole derivative, and a grain boundary passivation treatment is performed in a constant temperature bath at 40 to 60° C. The temperature stability of the solution is maintained by a constant temperature circulation system.

2. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The gold salt used in the electroplating solution is sodium chloroaurate, and the silver salt is silver nitrate.

3. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: During the electroplating process, the substrate is shaken in a horizontal reciprocating manner with a shaking frequency of 20 Hz.

4. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The gold-silver alloy electroplating solution also contains an organic complexing agent and a surfactant, which are used to improve the uniformity and adhesion of the plating layer.

5. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The gold-palladium alloy electroplating tank adopts a constant current source power supply, and the electroplating process is monitored in real time by an online conductivity and pH monitoring system.

6. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The molar ratio of gold to palladium in the gold-palladium alloy layer is 9:1 to 4:

1.

7. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The pure gold electroplating solution is a cyanide electroplating system containing sodium chloroaurate, and the plating solution temperature is controlled at 45-55°C.

8. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The surface roughness Ra of the pure gold outer layer is not greater than 0.2 μm, so as to improve its oxidation resistance and electrical contact performance.

9. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The benzotriazole derivative is methylbenzotriazole or hydroxybenzotriazole.

10. The method for preparing a gradient composite gold-silver alloy electroplating structure according to claim 1, characterized in that: The duration of the grain boundary passivation treatment is 5 to 15 minutes.

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