Nickel thickness uniformity method and system for thin gold high-corrosion-resistance hard gold process

Abstract

The invention discloses a nickel thickness uniformity method for a thin gold high-corrosion-resistance hard gold process. The nickel thickness uniformity method comprises the following steps: sequentially carrying out oil removal, micro-etching and acid pickling pretreatment on a to-be-electroplated copper base material; a nickel-phosphorus alloy layer is electroplated on the pretreated copper base material through the pulse electroplating technology, the mass percent of phosphorus in the nickel-phosphorus alloy layer is larger than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled to range from 5 micrometers to 15 micrometers; electroplating a hard gold layer on the nickel-phosphorus alloy layer by using a pulse electroplating process, wherein the thickness of the hard gold layer is less than 0.1 mu m; wherein the nickel-phosphorus alloy electroplating layer and the hard gold electroplating layer both adopt a pulse rectifier, and the nickel thickness uniformity is controlled by changing the tank body circulation mode and the baffle plate structure of the electroplating tank. According to the method, the thickness of the gold layer can be obviously reduced on the premise of ensuring the corrosion resistance and the plugging performance, and the thickness of the nickel layer can be uniformly controlled.

Description

Technical Field

[0001] This invention relates to the field of electroplating technology, specifically to a method and system for achieving uniform nickel thickness in a thin gold high corrosion-resistant hard gold process. Background Technology

[0002] In the manufacturing of electronic components such as circuit boards and substrates, electroplating hard gold is commonly used to improve insertion and removal performance, electrical performance, and weather resistance. Current technology typically employs a process of applying a thick layer of pure nickel followed by a thick gold plating (gold thickness ≥ 0.3 μm), but this process has the following problems: (1) Pure nickel layer has poor corrosion resistance and requires a thick gold layer to pass weather resistance tests such as salt spray and nitric acid; (2) The gold layer is thick, resulting in high cost; (3) The nickel layer thickness has poor uniformity, usually 3-70 μm.

[0003] In the existing technology, some researchers have proposed a nickel-phosphorus / platinum / hard gold composite coating structure, which has good corrosion resistance, but uses an expensive platinum layer, making the process complex and costly; other researchers have proposed a high-phosphorus electroless black nickel layer, which has good corrosion resistance, but has a complex structure, including a copper intermediate layer, and is not suitable for substrate electroplating; still other researchers have proposed a multi-layer composite coating structure, which is suitable for aluminum-based packaging shells, but the process is cumbersome, with many types of coatings, and is not suitable for ordinary substrates.

[0004] Therefore, there is an urgent need to develop an electroplating process that is low in cost, has a thin gold layer, good corrosion resistance, and excellent nickel thickness uniformity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and system for achieving uniform nickel thickness in a thin gold high corrosion resistant hard gold process, which addresses the shortcomings of the prior art. This method can significantly reduce the gold layer thickness and achieve uniform control of the nickel layer thickness while ensuring corrosion resistance and insertion / extraction performance.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for ensuring uniform nickel thickness in a thin gold high-corrosion-resistant hard gold process is provided, comprising: The copper substrate to be electroplated is subjected to degreasing, micro-etching and pickling pretreatment in sequence; A nickel-phosphorus alloy layer is electroplated on a pretreated copper substrate using a pulse electroplating process, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15 μm. A hard gold layer is electroplated on the nickel-phosphorus alloy layer using a pulse electroplating process, and the thickness of the hard gold layer is less than 0.1 μm; The nickel-phosphorus alloy layer and the hard gold layer are both plated using a pulse rectifier, and the uniformity of nickel thickness is controlled by changing the circulation mode and baffle structure of the electroplating tank.

[0007] In the above scheme, the change of the circulation method of the electroplating tank includes: adding side circulation on the premise that the original electroplating tank has a bottom circulation design.

[0008] In the above scheme, the increase in side circulation is achieved by adding a side spray device.

[0009] In the above scheme, the side-spraying device uses an array of nozzles with adjustable angle. The step of side-spraying the electroplating solution can enhance the solution circulation capability.

[0010] In the above scheme, changing the baffle structure of the electroplating tank includes using a porous anode baffle; wherein the aperture of the holes in the anode baffle is a gradient design, which can improve the overall uniformity of nickel plating.

[0011] In the above scheme, the average current density in the pulse electroplating process is 2.5 ASD, the pulse frequency is 500 Hz, and the pulse square wave duty cycle is 1:1.

[0012] In the above scheme, the electroplated nickel-phosphorus alloy layer is made of nickel-phosphorus alloy electroplating solution, and the phosphorus content in the nickel-phosphorus alloy electroplating solution is greater than 10%.

[0013] According to another aspect of the present invention, a system is provided for performing the above-described method for achieving nickel thickness uniformity in a thin gold high-corrosion-resistant hard gold process, comprising: The pretreatment unit is used to sequentially perform degreasing, micro-etching and pickling pretreatment on the copper substrate to be electroplated; The first pulse electroplating unit is used to electroplat a nickel-phosphorus alloy layer on a pretreated copper substrate using a pulse electroplating process, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15 μm. The second pulse electroplating unit is used to electroplat a hard gold layer on the nickel-phosphorus alloy layer using a pulse electroplating process, wherein the thickness of the hard gold layer is less than 0.1 μm. The tank circulation system, with a bottom circulation design, is equipped with a side spray device, which uses an array of nozzles with adjustable angle. The baffle structure uses a porous baffle with a gradually changing aperture design.

[0014] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: This invention provides a method for achieving uniform nickel thickness in a thin-layer, highly corrosion-resistant hard gold plating process. This method significantly improves corrosion resistance by replacing the pure nickel layer with a nickel-phosphorus alloy layer. Even when the gold layer thickness is less than 0.1 μm, it can still pass weathering tests such as salt spray and nitric acid tests. The gold layer thickness is greatly reduced, resulting in a significant decrease in cost. Through pulse electroplating and tank structure design, the uniformity of the nickel layer thickness can be controlled within the range of 5~15 μm. The process is simple, does not require the introduction of precious metals such as platinum and palladium, and is suitable for large-scale production. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic flowchart of a method for achieving uniform nickel thickness in a thin gold high corrosion resistant hard gold process according to Embodiment 1 of the present invention.

[0016] Figure 2 This is a schematic diagram of the baffle structure in Embodiment 1 of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0018] It should be understood that the sequence number of each step in the embodiment does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0019] Example 1 This application provides a method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process. Please refer to [link to relevant documentation]. Figure 1 ,include: S1, the copper substrate to be electroplated is subjected to degreasing, micro-etching and pickling pretreatment in sequence.

[0020] In this embodiment, the copper substrate to be electroplated is an incoming copper finger, which is subjected to pretreatments such as degreasing, micro-etching, and pickling in sequence.

[0021] S2, using pulse electroplating process to electroplat a nickel-phosphorus alloy layer on the pretreated copper substrate, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15μm. In this embodiment, a pulse rectifier is used in the electroplating of nickel-phosphorus alloy, and the uniformity of nickel thickness is controlled by changing the tank circulation mode and the design of the baffle structure.

[0022] Specifically, the tank circulation design in this embodiment includes adding a side-spraying electroplating solution step on top of the existing bottom circulation design of the electroplating tank, which can increase the side circulation of the electroplating tank. In this embodiment, the side-spraying of the electroplating solution uses an array of nozzles with adjustable angles to form side circulation of the electroplating solution in the electroplating tank.

[0023] Specifically, in this embodiment, the baffle structure is as follows: Figure 2 As shown, the baffle has an array of rectangular holes in the middle, and the diameter of the holes near the edge of the baffle is larger than that of the inner holes. The specific hole spacing and hole diameter are shown in the figure.

[0024] In this embodiment, the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, specifically, the phosphorus content in the nickel-phosphorus alloy electroplating solution is 23 g / L.

[0025] In this embodiment, the pulse electroplating process has an average current density of 2.5 ASD, a pulse frequency of 500 Hz, and a pulse square wave duty cycle of 1:1.

[0026] S3, a hard gold layer is electroplated on the nickel-phosphorus alloy layer using a pulse electroplating process, and the thickness of the hard gold layer is less than 0.1 μm.

[0027] In this embodiment, the above-described pulse electroplating process is also used to electroplat a hard gold layer.

[0028] Salt spray testing was conducted on the carrier plate samples prepared in this embodiment: The salt spray test chamber was sealed, the temperature was controlled (35±2℃), and the saturation tank temperature was (47±2℃). The samples were placed in a 5% sodium chloride aqueous solution, with the pH adjusted to the neutral range (6.5~7.2) as the spray solution. The test temperature was 35±2℃ for 24 hours, and the pressure was 1 kg / cm². 2 The corrosion level of the carrier plate sample in this embodiment was greater than 9 after testing.

[0029] The carrier plate sample prepared in this embodiment was subjected to nitric acid testing. The sample was placed in nitric acid with a concentration of 70±1%, a temperature of 23±2℃, a relative humidity of >60%, and a duration of 75 minutes. After testing, the number of corrosion points with a diameter D ≤0.05mm in the carrier plate sample of this embodiment did not exceed 2.

[0030] In summary, this embodiment provides a method for achieving uniform nickel thickness in a thin gold high corrosion-resistant hard gold process. This method can significantly reduce the gold layer thickness and achieve uniform control of the nickel layer thickness while ensuring corrosion resistance and insertion / extraction performance.

[0031] Example 2 This application provides a method for ensuring nickel thickness uniformity in a thin-gold, high-corrosion-resistant hard gold process. This method is basically the same as the method in Example 1, except that: In this embodiment, the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, specifically, the phosphorus content in the nickel-phosphorus alloy electroplating solution is 25 g / L.

[0032] Another aspect of this application provides a system for achieving the above-described method for ensuring nickel thickness uniformity in a thin gold high-corrosion-resistant hard gold process, comprising: The pretreatment unit is used to sequentially perform degreasing, micro-etching and pickling pretreatment on the copper substrate to be electroplated; The first pulse electroplating unit is used to electroplat a nickel-phosphorus alloy layer on a pretreated copper substrate using a pulse electroplating process, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15 μm. The second pulse electroplating unit is used to electroplat a hard gold layer on a nickel-phosphorus alloy layer using a pulse electroplating process, and the thickness of the hard gold layer is less than 0.1 μm. The tank circulation system, based on the original bottom circulation design of the electrolytic cell, adds a side spray device, which includes an array of nozzles with adjustable angles. The baffle structure is designed to add multiple holes with gradually varying hole diameters in the electroplating tank.

[0033] It should be noted that, depending on the implementation needs, the various steps described in this application can be broken down into more steps, or two or more steps or parts of the steps can be combined into new steps to achieve the purpose of this invention.

[0034] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for achieving uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process, characterized in that, include: The copper substrate to be electroplated is subjected to degreasing, micro-etching and pickling pretreatment in sequence; A nickel-phosphorus alloy layer is electroplated on a pretreated copper substrate using a pulse electroplating process, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15 μm. A hard gold layer is electroplated on the nickel-phosphorus alloy layer using a pulse electroplating process, and the thickness of the hard gold layer is less than 0.1 μm; The nickel-phosphorus alloy layer and the hard gold layer are both plated using a pulse rectifier, and the uniformity of nickel thickness is controlled by changing the circulation mode and baffle structure of the electroplating tank.

2. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, The change in the circulation method of the electroplating tank includes adding side circulation to the existing bottom circulation design of the electroplating tank.

3. The method for achieving uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 2, characterized in that, The increased side circulation is achieved by adding a side spray device.

4. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 3, characterized in that, The side spray device uses an array of nozzles with adjustable angles.

5. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, Changing the baffle structure of the electroplating tank includes using a porous anode baffle; wherein the aperture of the holes in the anode baffle is a gradient design.

6. The method for achieving uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, The average current density in the pulse electroplating process is 2.5 ASD.

7. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, The pulse frequency in the pulse electroplating process is 500 Hz.

8. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, In the pulse electroplating process, the duty cycle of the pulse square wave is 1:

1.

9. The method for ensuring uniform nickel thickness in a thin-film, high-corrosion-resistant hard gold process according to claim 1, characterized in that, The electroplated nickel-phosphorus alloy layer is applied using a nickel-phosphorus alloy electroplating solution, wherein the phosphorus content in the nickel-phosphorus alloy electroplating solution is greater than 10%.

10. A system for achieving the method for ensuring uniform nickel thickness in the thin gold high corrosion-resistant hard gold process as described in claims 1-9, characterized in that: include: The pretreatment unit is used to sequentially perform degreasing, micro-etching and pickling pretreatment on the copper substrate to be electroplated; The first pulse electroplating unit is used to electroplat a nickel-phosphorus alloy layer on a pretreated copper substrate using a pulse electroplating process, wherein the mass percentage of phosphorus in the nickel-phosphorus alloy layer is greater than 10%, and the thickness of the nickel-phosphorus alloy layer is controlled between 5-15 μm. The second pulse electroplating unit is used to electroplat a hard gold layer on the nickel-phosphorus alloy layer using a pulse electroplating process, wherein the thickness of the hard gold layer is less than 0.1 μm. The tank circulation system is equipped with a side spray device, which uses an array of nozzles with adjustable angle. The baffle structure uses a porous baffle with a gradually changing aperture design.

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