A two-step electroplating nickel-phosphorus alloy performance improvement process for neodymium iron boron

Abstract

The invention discloses a two-step electroplating nickel-phosphorus alloy performance improvement process method for NdFeB, comprising the following steps: S101, pre-treating a NdFeB substrate, and coating the surface of the pre-treated NdFeB substrate with a copper layer; S102, placing the NdFeB substrate coated with the copper layer in a first electroplating nickel-phosphorus solution for pre-plating nickel-phosphorus, and forming a first nickel-phosphorus alloy layer on the outer surface of the copper layer; S103, placing the NdFeB substrate coated with the first nickel-phosphorus alloy layer in a second electroplating nickel-phosphorus solution for thickening nickel-phosphorus, and forming a second nickel-phosphorus alloy layer on the outer surface of the first nickel-phosphorus alloy layer; the concentration of the first electroplating nickel-phosphorus solution is lower than that of the second electroplating nickel-phosphorus solution, and the pH value of the first electroplating nickel-phosphorus solution is higher than that of the second electroplating nickel-phosphorus solution, and the first electroplating nickel-phosphorus solution with a low concentration and a high pH value can greatly reduce the corrosion of the copper layer to form a uniform coating; the second electroplating nickel-phosphorus solution with a high concentration and a low pH value has a fast plating speed and is convenient for thickening the nickel-phosphorus coating.

Description

Technical Field

[0001] The invention relates to the technical field of neodymium iron boron magnet electroplating, and in particular to a two-step electroplating nickel-phosphorus alloy performance improvement process method for neodymium iron boron. Background Art

[0002] NdFeB substrate has extremely high magnetic energy product, and also has excellent magnetic properties such as high coercivity, high coercivity temperature coefficient and high saturation magnetic induction intensity. However, since the NdFeB substrate contains about 35% rare earth elements by mass, these rare earth elements are extremely active and easily oxidized and corroded, which affects its performance and service life. Therefore, it is necessary to form NdFeB magnets after protective coating treatment on the surface of NdFeB substrate, so that NdFeB magnets can achieve the advantages of high cost performance and good mechanical properties.

[0003] Electroplating is a commonly used surface treatment method. During the electroplating process, the plating metal or other insoluble materials serve as the anode, and the workpiece to be plated serves as the cathode. The cations of the plating metal are reduced on the surface of the workpiece to be plated to form a plating layer. The density and protective performance of the plating layer are particularly important for the NdFeB substrate. Electroplating of nickel-phosphorus alloy is one of the plating types with excellent performance. It has the advantages of fast deposition speed, high current efficiency, strong corrosion resistance, good wear resistance, and little effect on magnetic properties. It is often used in electroplating of NdFeB substrates. In the prior art, in order to give full play to the best performance of NdFeB magnets, cyanide-free alkaline copper is generally electroplated on the NdFeB substrate first, and then nickel-phosphorus alloy is electroplated on the outer surface of the copper layer. Under normal circumstances, the plating solution used for electroplating nickel-phosphorus alloy needs to maintain a low pH to stabilize the phosphorus content of the plating layer. However, the nickel-phosphorus solution with a low pH will corrode the copper layer when it first contacts the copper layer, which will cause the corrosion resistance of the plated NdFeB magnet to decrease, and the product performance will be greatly reduced. Summary of the invention

[0004] The purpose of the present invention is to provide a two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB, and the technical problem to be solved is to improve the corrosion resistance of NdFeB magnets after electroplating.

[0005] To achieve the above-mentioned purpose, the solution of the present invention is: a two-step electroplating nickel-phosphorus alloy performance improvement process method for neodymium iron boron, comprising the following steps;

[0006] S101, pre-treating the NdFeB substrate, wherein the surface of the pre-treated NdFeB substrate is plated with a copper layer;

[0007] S102, placing the NdFeB substrate coated with the copper layer in a first nickel-phosphorus electroplating solution for pre-plating nickel-phosphorus, so as to form a first nickel-phosphorus alloy layer on the outer surface of the copper layer;

[0008] S103, placing the NdFeB substrate coated with the first nickel-phosphorus alloy layer in a second nickel-phosphorus electroplating solution to thicken the nickel-phosphorus, and forming a second nickel-phosphorus alloy layer on the outer surface of the first nickel-phosphorus alloy layer;

[0009] The chemical components in the first nickel-phosphorus electroplating solution are the same as the chemical components in the second nickel-phosphorus electroplating solution, and the concentration of each chemical component in the first nickel-phosphorus electroplating solution is lower than the concentration of the corresponding chemical component in the second nickel-phosphorus electroplating solution, so that the concentration of the first nickel-phosphorus electroplating solution is lower than the concentration of the second nickel-phosphorus electroplating solution, and the pH value of the first nickel-phosphorus electroplating solution is higher than the pH value of the second nickel-phosphorus electroplating solution.

[0010] Furthermore, the first nickel-phosphorus electroplating solution consists of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water, wherein water is a solvent, and the second nickel-phosphorus electroplating solution consists of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water, wherein water is a solvent.

[0011] Furthermore, in step S102, the mass concentration of each chemical component in the first nickel-phosphorus electroplating solution is as follows:

[0012] Nickel sulfate: 200-240g / L;

[0013] Sodium citrate: 45-65g / L;

[0014] Sodium hypophosphite: 20-30g / L;

[0015] Orthophosphate: 15-25g / L;

[0016] The temperature of pre-plating nickel-phosphorus is 60-70°C, pH: 3.1-3.3; the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ;

[0017] The thickness d of the first nickel-phosphorus alloy layer NIP1 =0.5~2.5 microns.

[0018] Furthermore, in step S103, the mass concentration of each chemical component in the second nickel-phosphorus electroplating solution is as follows:

[0019] Nickel sulfate: 360-440g / L;

[0020] Sodium citrate: 70-100g / L;

[0021] Sodium hypophosphite: 40-50g / L;

[0022] Orthophosphate: 35-45g / L;

[0023] The temperature of thickened nickel-phosphorus is 60-70°C, pH: 2.7-2.9, the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ;

[0024] The thickness d of the second nickel-phosphorus alloy layer NIP2 =1~10 microns.

[0025] Furthermore, in step S102, the NdFeB substrate that has been pre-plated with nickel-phosphorus is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution, and the activation time is 5-50 seconds at room temperature.

[0026] Further, the pre-treatment process of S101 includes the following steps:

[0027] S601: Activate the NdFeB substrate in an activation solution, wherein the activation solution is 0.5-2% hydrofluoric acid, and the activation time is 5-50 seconds at room temperature;

[0028] S602: placing the activated NdFeB substrate in a first electroplating copper solution for pre-copper plating to form a first copper layer on the outer surface of the NdFeB substrate;

[0029] S603: washing the pre-copper-plated NdFeB substrate in ultrapure water for 5-15 seconds at room temperature;

[0030] S604: placing the washed NdFeB substrate in a second copper electroplating solution for thickening copper plating to form a second copper layer on the outer surface of the first copper layer;

[0031] S605: The thickened copper-plated NdFeB substrate is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution. The activation time is 5-50 seconds at room temperature.

[0032] Furthermore, in step S602, the mass concentration of each chemical component in the first copper electroplating solution is as follows:

[0033] Copper ion: 1.5-2.5g / L;

[0034] HEDP: 80-150g / L;

[0035] Potassium carbonate: 20-80g / L;

[0036] Potassium hydroxide: 20-100g / L;

[0037] Organic amine compounds: 0.001-10g / L;

[0038] The temperature of pre-plating copper is 10-25℃, pH: 9-12; the anode is phosphor copper anode or oxygen-free copper anode. If barrel plating is used, the current density is 0.1-0.3A / dm 2 ; If rack plating is used, the current density is 0.2~1.0A / dm 2 ;

[0039] The thickness of the first copper layer d cu1 =0.5~2.5 microns.

[0040] Furthermore, in step S604, the mass concentration of each chemical component in the second copper electroplating solution is as follows:

[0041] Copper ion: 6-12g / L;

[0042] HEDP: 80-200g / L;

[0043] Potassium carbonate: 20-80g / L;

[0044] Potassium hydroxide: 20-100g / L;

[0045] Brightener: 5~15ml / L;

[0046] Auxiliary agent: 5~15ml / L;

[0047] The temperature of thick copper plating is 40-60 o C, pH: 8-10; the anode is phosphor copper anode or oxygen-free copper anode; if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ;

[0048] The thickness of the second copper layer d cu2 =1.5~2.5 microns.

[0049] Furthermore, the copper ions are obtained by dissolving a copper-containing inorganic salt during solution preparation, and the copper-containing inorganic salt is selected from at least one of copper sulfate, copper acetate, and copper carbonate.

[0050] After adopting the above scheme, the beneficial effect of the present invention is that: the first nickel-phosphorus alloy layer is formed by electroplating with the first nickel-phosphorus electroplating solution, and the second nickel-phosphorus alloy layer is formed by electroplating with the second nickel-phosphorus electroplating solution, the types of chemical components in the first nickel-phosphorus electroplating solution are the same as the types of chemical components in the second nickel-phosphorus electroplating solution, wherein water is used as a solvent, the concentration of the first nickel-phosphorus electroplating solution is lower than the concentration of the second nickel-phosphorus electroplating solution, the pH value of the first nickel-phosphorus electroplating solution is higher than the pH value of the second nickel-phosphorus electroplating solution, and electroplating is first performed with the first nickel-phosphorus electroplating solution with a low concentration and a high pH value, which can greatly reduce the corrosion of the copper layer, so that the difference between the edge thickness and the middle thickness of the neodymium iron boron substrate forming the first nickel-phosphorus alloy layer is small, the thickness at each location is more balanced, and the plating speed is slower, the coating is denser and more uniform, and on this basis, the second nickel-phosphorus electroplating solution with a high concentration and a low pH value is used for electroplating to increase the plating speed and the coating thickness, so as to thicken the nickel-phosphorus and improve the overall coating quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a flow chart of the electroplating process of the prior art.

[0052] Figure 2 It is a flow chart of the electroplating process of the present invention.

[0053] Figure 3 It is a schematic diagram of the sampling point locations of S1 and S5 in the present invention.

[0054] Figure 4 It is a comparison diagram of the appearance of the product after electroplating of Example 1 and the comparative example.

[0055] Figure 5 It is a comparison diagram of Example 1 and the comparative example after a 72-hour neutral salt spray test after the electroplating was completed.

[0056] Figure 6 It is a comparison table of technical experimental parameters between Example 1 and Comparative Example. DETAILED DESCRIPTION

[0057] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] The present invention provides a two-step electroplating nickel-phosphorus alloy performance improvement process for neodymium iron boron, comprising the following steps:

[0059] S101, pre-treating the NdFeB substrate, wherein the surface of the pre-treated NdFeB substrate is plated with a copper layer;

[0060] S102, placing the NdFeB substrate coated with the copper layer in a first nickel-phosphorus electroplating solution for pre-plating nickel-phosphorus, so as to form a first nickel-phosphorus alloy layer on the outer surface of the copper layer;

[0061] S103, placing the NdFeB substrate coated with the first nickel-phosphorus alloy layer in a second nickel-phosphorus electroplating solution to thicken the nickel-phosphorus, and forming a second nickel-phosphorus alloy layer on the outer surface of the first nickel-phosphorus alloy layer;

[0062] Among them, the first nickel-phosphorus electroplating solution is composed of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water, and the second nickel-phosphorus electroplating solution is composed of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water. The chemical components in the first nickel-phosphorus electroplating solution are the same as the chemical components in the second nickel-phosphorus electroplating solution, that is, the raw materials in the first nickel-phosphorus electroplating solution and the second nickel-phosphorus electroplating solution are the same, wherein water is used as a solvent, nickel sulfate is used as a main salt, and sodium hypophosphite and orthophosphate are additives; the pH value of the first nickel-phosphorus electroplating solution is higher than that of the second nickel-phosphorus electroplating solution; the first nickel-phosphorus electroplating solution has a low main salt concentration and a high pH value, which can greatly reduce the corrosion of the copper layer to form a uniform and uniformly thick first nickel-phosphorus alloy layer, while the second nickel-phosphorus electroplating solution has a high main salt concentration, a low pH value, and a fast plating speed, which can facilitate the thickening of nickel-phosphorus, and increase the thickness of the plating layer on the basis of the first nickel-phosphorus alloy layer, without affecting the copper layer; in other embodiments, the chemical components in the first nickel-phosphorus electroplating solution and the second nickel-phosphorus electroplating solution can also be composed of other components, but are not limited to this.

[0063] It is a prior art to plate a copper layer on the surface of an NdFeB substrate. Specifically, the NdFeB substrate can be placed in a solution such as a cyanide-free alkali copper electroplating solution or a copper pyrophosphate electroplating solution, and electroplated under certain process conditions to form a copper plating layer on the surface of the NdFeB substrate. In this specific embodiment, the NdFeB substrate is first activated and washed with water, and then the NdFeB substrate is placed in a first copper electroplating solution for pre-copper plating to form a first copper layer. The NdFeB substrate with the first copper layer is then placed in a second copper electroplating solution for thickening copper plating to form a second copper layer on the outer surface of the first copper layer, and finally the copper layer is formed. The first copper electroplating solution is composed of copper ions, HEDP, potassium carbonate, potassium hydroxide, organic amine compounds and water; the second copper electroplating solution is composed of copper ions, HEDP, potassium carbonate, potassium hydroxide, a brightener, an auxiliary agent and water.

[0064] The pre-treatment process in the step S101 comprises the following steps:

[0065] S601: Activate the NdFeB substrate in an activation solution, wherein the activation solution is 0.5-2% hydrofluoric acid, and the activation time is 5-50 seconds at room temperature;

[0066] S602: placing the activated NdFeB substrate in a first electroplating copper solution for pre-copper plating to form a first copper layer on the outer surface of the NdFeB substrate;

[0067] S603: washing the pre-copper-plated NdFeB substrate in ultrapure water for 5-15 seconds at room temperature;

[0068] S604: placing the washed NdFeB substrate in a second copper electroplating solution for thickening copper plating to form a second copper layer on the outer surface of the first copper layer;

[0069] S605: The thickened copper-plated NdFeB substrate is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution. The activation time is 5-50 seconds at room temperature.

[0070] Preferably, in the step S102, the mass concentration of each chemical component in the first nickel-phosphorus electroplating solution is as follows:

[0071] Nickel sulfate: 200-240g / L;

[0072] Sodium citrate: 45-65g / L;

[0073] Sodium hypophosphite: 20-30g / L;

[0074] Orthophosphate: 15-25g / L;

[0075] The temperature of pre-plating nickel-phosphorus is 60-70°C, pH: 3.1-3.3; the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ;

[0076] The thickness d of the first nickel-phosphorus alloy layer NIP1 =0.5~2.5 microns.

[0077] Preferably, in the step S103, the mass concentration of each chemical component in the second nickel-phosphorus electroplating solution is as follows:

[0078] Nickel sulfate: 360-440 g / L;

[0079] Sodium citrate: 70-100g / L;

[0080] Sodium hypophosphite: 40-50g / L;

[0081] Orthophosphate: 35-45g / L;

[0082] The temperature of thickened nickel-phosphorus is 60-70°C, pH: 2.7-2.9, the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ;

[0083] The thickness d of the second nickel-phosphorus alloy layer NIP2 =1~10 microns.

[0084] Preferably, in the step S602, the mass concentration of each chemical component in the first copper electroplating solution is as follows:

[0085] Copper ion: 1.5-2.5g / L;

[0086] HEDP: 80-150g / L;

[0087] Potassium carbonate: 20-80g / L;

[0088] Potassium hydroxide: 20-100g / L;

[0089] Organic amine compounds: 0.001-10g / L;

[0090] The temperature of pre-plating copper is 10-25℃, pH: 9-12; the anode is phosphor copper anode or oxygen-free copper anode. If barrel plating is used, the current density is 0.1-0.3A / dm 2 ; If rack plating is used, the current density is 0.2~1.0A / dm 2 Among them, the organic amine compounds are triethylenediamine and diethylenetriamine, which can make the appearance of the electroplated products uniform and consistent after addition. HEDP, as a complexing agent, can form a stable complex with metal ions. Its full name is hydroxyethylidene diphosphonic acid.

[0091] The thickness of the first copper layer d cu1 =0.5~2.5 microns.

[0092] Preferably, in the step S604, the mass concentration of each chemical component in the second copper electroplating solution is as follows:

[0093] Copper ion: 6-12g / L;

[0094] HEDP: 80-200g / L;

[0095] Potassium carbonate: 20-80g / L;

[0096] Potassium hydroxide: 20-100g / L;

[0097] Brightener: 5~15ml / L;

[0098] Auxiliary agent: 5~15ml / L;

[0099] The temperature of thick copper plating is 40-60 o C, pH: 8-10; the anode is phosphor copper anode or oxygen-free copper anode; if barrel plating is used, the current density is 0.5-2.0A / dm 2; If rack plating is used, the current density is 0.5~4.0A / dm 2 Among them, the brightener is tin dioxide, which improves the ability of the product surface to reflect light, and the auxiliary agent is butynediol;

[0100] The thickness of the second copper layer d cu2 =1.5~2.5 microns.

[0101] Focus on combination Figure 2 As shown, between step S102 and step S102, the NdFeB substrate coated with the first nickel-phosphorus alloy layer needs to be activated to improve the surface coating bonding strength and make the surface layer of the NdFeB substrate more uniform, so as to facilitate the subsequent thickening nickel-phosphorus process. The NdFeB substrate pre-plated with nickel-phosphorus in step S102 is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution, and the activation time is 5-50 seconds at room temperature.

[0102] It also includes post-processing the NdFeB substrate that forms the second nickel-phosphorus alloy layer after the S103 step, placing the NdFeB substrate coated with the second nickel-phosphorus alloy layer in ultrapure water, and washing it at room temperature for 5-15 seconds, where ultrapure water is water with almost no impurities except water molecules; then packing the NdFeB substrate in a PVC box with mesh, putting it in a drying oven and blowing it downwards, and finally inspecting it before shipping.

[0103] The copper ions used in step S602 and S604 are obtained by dissolving a copper-containing inorganic salt during solution preparation, and the copper-containing inorganic salt is selected from at least one of copper sulfate, copper acetate, and copper carbonate.

[0104] Embodiment one:

[0105] A two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB, the substrate workpiece is a NdFeB sheet with a size of 4mm×6mm×0.3mm, where 0.3mm is the thickness of the product, the NdFeB substrate to be electroplated is placed in an electroplating tank for electroplating, and a steel ball and a plating sheet are used for plating, focusing on combining Figure 2 As shown, the following steps are included:

[0106] (1) Activate the NdFeB substrate in an activation solution containing 0.5-2% hydrofluoric acid and the activation time is 5-50 seconds at room temperature;

[0107] (2) placing the activated NdFeB substrate in a first electroplating copper solution for pre-copper plating to form a first copper layer on the outer surface of the NdFeB substrate, wherein the mass concentration of each chemical component in the first electroplating copper solution is as follows:

[0108] Copper ion: 2g / L;

[0109] HEDP: 135 g / L;

[0110] Potassium carbonate: 50g / L;

[0111] Potassium hydroxide: 60g / L;

[0112] Organic amine compounds: 5g / L,

[0113] The pre-plating temperature is 19°C, pH: 10.4; the anode is oxygen-free copper anode, roller plating is adopted, and the current density is 0.2A / dm 2 ; Wherein the thickness of the first electroplated copper layer is d cu1 = 1.5 microns; focus on combination Figure 6 As shown in the figure, a 300S impulse current is applied during the pre-copper plating process, and the current density of the impulse current is about 0.25A / dm 2 , first quickly plate a layer of copper on the NdFeB substrate to prevent corrosion of the substrate, and then apply a current density of 0.2A / dm 2 The electroplating time is 5700S, and the thickness of the first electroplated copper layer is d cu1 = 1.5 μm;

[0114] (3) Wash the pre-copper-plated NdFeB substrate in ultrapure water for 5-15 seconds at room temperature;

[0115] (4) placing the washed NdFeB substrate in a second copper electroplating solution for thickening copper plating to form a second copper layer on the outer surface of the NdFeB substrate, wherein the mass concentration of each chemical component in the second copper electroplating solution is as follows:

[0116] Copper ion: 9.5g / L;

[0117] HEDP: 150g / L;

[0118] Potassium carbonate: 55g / L;

[0119] Potassium hydroxide: 35g / L;

[0120] Brightener: 8ml / L;

[0121] Auxiliary agent: 7ml / L;

[0122] The temperature of thick copper plating is 50℃; pH: 8.8; roller plating is adopted, and the current density is 0.3A / dm 2 ; The electroplating time is 6600S, and the thickness of the second electroplated copper layer formed is d cu2 =2.5 microns.

[0123] (5) Activate the thickened copper-plated NdFeB substrate using 0.5-2% sulfuric acid as the activation solution, and the activation time is 5-50 seconds at room temperature.

[0124] (6) placing the activated NdFeB substrate in a first electroplating nickel-phosphorus solution for pre-plating nickel-phosphorus, and forming a first nickel-phosphorus alloy layer on the outer surface of the second electroplating copper layer, wherein the mass concentration of each chemical component in the first electroplating nickel-phosphorus solution is as follows:

[0125] Nickel sulfate: 220g / L;

[0126] Sodium citrate: 55g / L;

[0127] Sodium hypophosphite: 25g / L;

[0128] Orthophosphate: 20g / L;

[0129] The pre-plating temperature of nickel-phosphorus is 65°C, pH: 3.2, the anode is an electrolytic nickel block anode, and the roller plating is adopted, and the current density is 0.3A / dm 2 The electroplating time is 2400S, and the thickness of the first nickel-phosphorus alloy layer formed is d NIP1 =1.2 μm.

[0130] (7) Placing the NdFeB substrate coated with the first nickel-phosphorus alloy layer in a second nickel-phosphorus electroplating solution to thicken the nickel-phosphorus, and forming a second nickel-phosphorus alloy layer on the outer surface of the first nickel-phosphorus alloy layer, wherein the mass concentration of each chemical component in the second nickel-phosphorus electroplating solution is as follows:

[0131] Nickel sulfate: 440g / L;

[0132] Sodium citrate: 100g / L;

[0133] Sodium hypophosphite: 45g / L;

[0134] Orthophosphate: 40g / L;

[0135] The temperature of thickened nickel-phosphorus is 65°C, pH: 2.9; the anode is an electrolytic nickel block anode, using barrel plating, and the current density is 0.3A / dm 2 ; The electroplating time is 4200S, and the thickness of the second nickel-phosphorus alloy layer is d NIP2 =1.8 μm.

[0136] The NdFeB substrate forming the second nickel-phosphorus alloy layer is post-processed: the NdFeB substrate thickened with nickel-phosphorus is placed in ultrapure water and washed for 5-15 seconds at room temperature; then the NdFeB substrate is packed in a PVC box with mesh and placed in a drying oven to be blown downwards.

[0137] Comparative Example

[0138] The difference from Example 1 is that the pre-nickel-phosphorus plating process is missing. Figure 1 As shown, it is referred to as single-layer nickel-phosphorus electroplating process; then focus on Figure 6It can be seen that the electroplating time of the thickened nickel-phosphorus in the comparative example is 5400S, while the electroplating time of the thickened nickel-phosphorus in the first embodiment is 4200S; in this way, nickel-phosphorus layers with the same thickness are formed.

[0139] Focus on combination Figure 3 As shown, S1 is the thickness at the edge sampling point of the NdFeB product, S5 is the thickness at the middle sampling point of the NdFeB product, and the edge-to-center ratio is expressed as S1 / S5. The smaller the edge-to-center ratio is, the closer the edge thickness and the middle thickness of the NdFeB product are, and the product quality and performance are better. If the edge-to-center ratio is larger, it means that the edge thickness and the middle thickness of the NdFeB product are very different, which means that the copper layer is corroded to different degrees and the product quality is poor.

[0140] The results of Example 1 and Comparative Example are shown in Table 1 and Table 2:

[0141] Table 1: In Example 1, 5 sample blocks are randomly selected for measurement to obtain the edge-to-center ratio data table of each sample block:

[0142]

[0143] Table 2: Randomly select 5 samples from the comparison ratio and measure to obtain the edge-to-center ratio data of each sample:

[0144]

[0145] The data comparison between Table 1 and Table 2 shows that, under the premise of consistent electroplating conditions, the fluctuation range of the edge-to-center ratio of the NdFeB product after the single-layer nickel-phosphorus electroplating process in the comparative example is 1.33-1.51, and the fluctuation range of the edge-to-center ratio of the NdFeB product after the two-step nickel-phosphorus alloy electroplating process in Example 1 is 1.25-1.31. Compared with the two, the edge-to-center ratio of each sample block in the comparative example has a large fluctuation range and a high value, indicating that the difference between the edge thickness and the middle thickness of the product is large, and the plating thickness is uneven, indicating that different degrees of corrosion are produced in various parts of the copper layer, resulting in uneven thickness of the nickel-phosphorus plating layer formed, and a large fluctuation range; after the two-step nickel-phosphorus alloy electroplating process, the edge-to-center ratio of each sample block becomes smaller, the fluctuation range is small, the difference between the middle and edge thickness of the sample block is small, and the product performance is better.

[0146] At the same time, focus on Figure 4 As shown, it can be seen that the product appearance in the comparative example is greatly different and the color is uneven; the appearance of the product in Example 1 is more uniform, the difference is small, and the appearance quality is better.

[0147] Focus on combination Figure 5As shown, 32 pieces of NdFeB products in Example 1 and Comparative Example were randomly selected and subjected to a 72-hour neutral salt spray test experiment. The experiment used a 5% sodium chloride saline solution, the pH value of the solution was adjusted to a neutral range (6-7), the test temperature was constant at 35°C ± 2°C, the relative humidity was between 95% and 98%, and the sedimentation rate of the salt spray should be between 1 and 2 ml / 80cm²·h. It can be seen that the 32 pieces of NdFeB products in Example 1 have uniform appearance and have passed the 72-hour neutral salt spray test experiment, while the 32 pieces of NdFeB products in the comparative example have obvious color difference in appearance, and 3 pieces have failed the 72-hour neutral salt spray test experiment.

[0148] Embodiment 2: A two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB, compared with Embodiment 1, the difference is that the process parameters of the first electroplating nickel-phosphorus solution in the pre-nickel-phosphorus plating process are different, as follows:

[0149] The activated NdFeB substrate is placed in a first nickel-phosphorus electroplating solution for pre-plating nickel-phosphorus, and a first nickel-phosphorus alloy layer is formed on the outer surface of the second electroplated copper layer, wherein the mass concentration of each chemical component in the first nickel-phosphorus electroplating solution is as follows:

[0150] Nickel sulfate: 240g / L;

[0151] Sodium citrate: 60g / L;

[0152] Sodium hypophosphite: 30g / L;

[0153] Orthophosphate: 25g / L;

[0154] The current density of the first nickel-phosphorus alloy layer during the barrel plating process was 0.3A / dm 2 The anode is an electrolytic nickel block anode. The temperature of the first electroplating nickel-phosphorus solution is 65°C, pH: 3.2; the electroplating time is 2400S, and the thickness of the first nickel-phosphorus alloy layer formed is d NIP1 =1.2 μm.

[0155] Table 3: In Example 2, 5 sample blocks are randomly selected for measurement to obtain the edge-to-center ratio data table of each sample block:

[0156]

[0157] The edge-to-center ratio of each sample block in Example 2 fluctuates in the range of 1.24-1.29, the edge-to-center ratio of each sample block is balanced, the fluctuation range is small, and the thickness difference between the middle and edge of the sample block is small; it indicates that the two-step process of pre-plating nickel-phosphorus and thickening nickel-phosphorus can effectively reduce the corrosion of the copper layer. When pre-plating nickel-phosphorus, a first electroplating nickel-phosphorus solution with a low main salt content and a high pH value is used, which can greatly reduce the corrosion of the copper layer, and the plating speed is slower, the coating is denser, the coating is more uniform, and the edge-to-center ratio is more balanced. On this basis, when thickening nickel-phosphorus, a second electroplating nickel-phosphorus solution with a high main salt content and a lower pH value is used to increase the plating speed and coating thickness, which can improve the overall coating quality of the product and make the nickel-phosphorus alloy layer more uniform.

[0158] The above description is only a preferred embodiment of the present invention and is not a limitation on the design of this case. Any equivalent changes made based on the design key of this case shall fall within the protection scope of this case.

Claims

1. A two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB, characterized in that : Includes the following steps; S101, pre-treating the NdFeB substrate, wherein the surface of the pre-treated NdFeB substrate is plated with a copper layer; S102, placing the NdFeB substrate coated with the copper layer in a first nickel-phosphorus electroplating solution for pre-plating nickel-phosphorus, so as to form a first nickel-phosphorus alloy layer on the outer surface of the copper layer; S103, placing the NdFeB substrate coated with the first nickel-phosphorus alloy layer in a second nickel-phosphorus electroplating solution to thicken the nickel-phosphorus, and forming a second nickel-phosphorus alloy layer on the outer surface of the first nickel-phosphorus alloy layer; The chemical components in the first nickel-phosphorus electroplating solution are the same as the chemical components in the second nickel-phosphorus electroplating solution, and the concentrations of the chemical components in the first nickel-phosphorus electroplating solution are respectively lower than the concentrations of the corresponding chemical components in the second nickel-phosphorus electroplating solution, so that the concentration of the first nickel-phosphorus electroplating solution is lower than the concentration of the second nickel-phosphorus electroplating solution, and the pH value of the first nickel-phosphorus electroplating solution is higher than the pH value of the second nickel-phosphorus electroplating solution; The first electroplating nickel-phosphorus solution is composed of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water, wherein water is a solvent, and the second electroplating nickel-phosphorus solution is composed of nickel sulfate, sodium citrate, sodium hypophosphite, orthophosphate and water, wherein water is a solvent; In the step S102, the mass concentration of each chemical component in the first nickel-phosphorus electroplating solution is as follows: Nickel sulfate: 200-240g / L; Sodium citrate: 45-65g / L; Sodium hypophosphite: 20-30g / L; Orthophosphate: 15-25g / L; The temperature of pre-plating nickel-phosphorus is 60-70°C, pH: 3.1-3.3; the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ; The thickness d of the first nickel-phosphorus alloy layer NIP1 = 0.5~2.5 μm; In the step S103, the mass concentration of each chemical component in the second nickel-phosphorus electroplating solution is as follows: Nickel sulfate: 360-440g / L; Sodium citrate: 70-100g / L; Sodium hypophosphite: 40-50g / L; Orthophosphate: 35-45g / L; The temperature of thickened nickel-phosphorus is 60-70°C, pH: 2.7-2.9, the anode is an electrolytic nickel block anode, if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ; The thickness d of the second nickel-phosphorus alloy layer NIP2 =1~10 microns.

2. The two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB according to claim 1 is characterized in that : The NdFeB substrate pre-plated with nickel-phosphorus in step S102 is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution, and the activation time is 5-50 seconds at room temperature.

3. The two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB according to claim 1 is characterized in that The pre-treatment process of S101 comprises the following steps: S601: Activate the NdFeB substrate in an activation solution, wherein the activation solution is 0.5-2% hydrofluoric acid, and the activation time is 5-50 seconds at room temperature; S602: placing the activated NdFeB substrate in a first electroplating copper solution for pre-copper plating to form a first copper layer on the outer surface of the NdFeB substrate; S603: washing the pre-copper-plated NdFeB substrate in ultrapure water for 5-15 seconds at room temperature; S604: placing the washed NdFeB substrate in a second copper electroplating solution for thickening copper plating to form a second copper layer on the outer surface of the first copper layer; S605: The thickened copper-plated NdFeB substrate is placed in an activation solution for activation. The activation solution uses 0.5-2% sulfuric acid as the activation solution. The activation time is 5-50 seconds at room temperature.

4. The two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB according to claim 3 is characterized in that In the step S602, the mass concentration of each chemical component in the first copper electroplating solution is as follows: Copper ion: 1.5-2.5g / L; HEDP: 80-150g / L; Potassium carbonate: 20-80g / L; Potassium hydroxide: 20-100g / L; Organic amine compounds: 0.001-10g / L; The temperature of pre-plating copper is 10-25℃, pH: 9-12; the anode is phosphor copper anode or oxygen-free copper anode. If barrel plating is used, the current density is 0.1-0.3A / dm 2 ; If rack plating is used, the current density is 0.2~1.0A / dm 2 ; The thickness of the first copper layer d cu1 =0.5~2.5 microns.

5. The two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB according to claim 3 is characterized in that : In the step S604, the mass concentration of each chemical component in the second copper electroplating solution is as follows: Copper ion: 6-12g / L; HEDP: 80-200g / L; Potassium carbonate: 20-80g / L; Potassium hydroxide: 20-100g / L; Brightener: 5~15ml / L; Auxiliary agent: 5~15ml / L; The temperature of thick copper plating is 40-60 o C, pH: 8-10; the anode is phosphor copper anode or oxygen-free copper anode; if barrel plating is used, the current density is 0.5-2.0A / dm 2 ; If rack plating is used, the current density is 0.5~4.0A / dm 2 ; The thickness of the second copper layer d cu2 =1.5~2.5 microns.

6. The two-step electroplating nickel-phosphorus alloy performance improvement process for NdFeB according to claim 4 or 5, characterized in that : The copper ions are obtained by dissolving a copper-containing inorganic salt during solution preparation, and the copper-containing inorganic salt is selected from at least one of copper sulfate, copper acetate, and copper carbonate.

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