Low-stress high-strength electroplating nickel-phosphorus alloy plating solution as well as preparation method and application thereof

Abstract

The invention discloses a low-stress high-strength nickel-phosphorus alloy electroplating solution and a preparation method and application thereof, and belongs to the technical field of nickel electroplating. The plating solution comprises nickel aminosulfonate, lactic acid and / or lactate, phosphorous acid and / or phosphite, saccharin and / or saccharin salt, and a solvent of the plating solution is water; the molar ratio of nickel aminosulfonate to lactic acid and / or lactate is 0.7 < = M nickel aminosulfonate / M lactic acid and / or lactate < = 1, the molar ratio of phosphorous acid and / or phosphite to saccharin and / or saccharin salt is 2 < = M phosphorous acid and / or phosphite / M saccharin and / or saccharin salt < = 8, and the pH value of the plating solution is 3.0-4.5. According to the low-stress high-strength electroplating nickel-phosphorus alloy plating solution as well as the preparation method and the using method thereof, an obtained nickel-phosphorus alloy plating layer is controllable in stress, and the strength of the nickel-phosphorus alloy plating layer is remarkably superior to that of pure nickel and nickel-cobalt alloy plating layers.

Description

Technical Field

[0001] The invention belongs to the technical field of nickel electroplating, and specifically relates to a low-stress and high-strength nickel-phosphorus alloy electroplating solution and a preparation method and application thereof. Background Art

[0002] The technology of replicating optical lenses by electroplating nickel and nickel-based alloys through ultra-precision polished mandrels is one of the most commonly used technical routes in the field of X-ray focusing mirror manufacturing. There are currently two main technical routes for this process internationally, namely electroplating pure nickel replication and electroplating nickel-cobalt replication. Future detection plans require a larger collection area, which needs to be achieved by continuously nesting more and larger focusing mirror lenses. Due to the limitations of rocket carrying capacity and cost, the thickness of the focusing mirror cannot increase linearly with the size, which puts higher requirements on the materials of the electroplated lenses. There are three main requirements for the electroplating manufacturing of X-ray focusing mirrors. First, the internal stress of the coating is very low to ensure that the lens does not deform during the electroplating process; second, the lens strength is very high, which can ensure that the lens withstands stress without plastic deformation during demolding, assembly and transportation, and maintains surface accuracy; third, the current efficiency of the plating solution cannot be too low, and the composition of the plating solution cannot change significantly during the continuous production of the lens, which is easy to control. The existing electroplating pure nickel and nickel-cobalt replication technology is difficult to meet the requirements of lens strength when facing the future manufacturing tasks of thinner and larger X-ray focusing mirrors.

[0003] The strength of nickel-phosphorus alloy is significantly better than that of pure nickel and nickel-cobalt alloy. In the prior art, nickel-phosphorus alloy is usually prepared by chemical plating and electroplating. The chemical plating method cannot be applied to the manufacture of X-ray focusing mirrors that require precise control of stress and thickness due to the uncontrollable composition of the plating solution and the short life of the plating solution. There are two phosphorus sources used in the electroplating of nickel-phosphorus alloy, phosphorous acid and sodium hypophosphite. Sodium hypophosphite is unstable and easily oxidized to phosphite at the anode in the plating solution. Phosphorous acid is very stable and its concentration is easy to control. The concentration of each component in the nickel-phosphorus alloy electroplating solution used in the prior art is 180-250g / L of nickel sulfate, 35-45g / L of nickel chloride, 20-30g / L of nickel carbonate, 25-35ml / L of phosphoric acid, and 30-40g / L of phosphorous acid. Based on this concentration range, a high-phosphorus nickel-phosphorus alloy with a cost lower than that of chemical plating is obtained. However, high concentrations of phosphorous acid will lead to low current efficiency of the plating solution, and the nickel ion concentration will increase rapidly with the use of the plating solution. It is generally believed that the current efficiency is inversely proportional to the phosphorous acid concentration of the plating solution. Therefore, in order to obtain a higher current efficiency when electroplating nickel-phosphorus alloy, the concentration of phosphorous acid in the plating solution cannot be too high. In the prior art, lactic acid is often used as a complexing agent in chemical plating solution to stabilize the plating solution.

[0004] The invention patent application 118360595A discloses a high-phosphorus chemical nickel-phosphorus alloy plating solution and a chemical plating method thereof. The chemical plating solution comprises 25 to 30 g / L nickel sulfate and 20 to 25 g / L lactic acid, and the molar ratio of nickel ions to lactic acid is between 0.3 and 0.5. The invention patent application CN116426990A discloses a nickel-phosphorus alloy electroplating solution and an electroplating method. In the nickel-phosphorus alloy electroplating solution, the plating solution composition includes 15-35 g / L nickel sulfate, 18-38 g / L sodium hypophosphite, and 10-30 ml / L lactic acid. The molar ratio of nickel ions to lactic acid is similar to that of chemical plating solution. Lactic acid mainly plays a role in controlling the free nickel used for reduction in the plating solution. Most of the hypophosphite in the plating solution and the chemical plating solution will be oxidized to phosphite during use. If the molar ratio of nickel ions to lactic acid is higher than 0.5, the plating solution has poor stability and nickel phosphite precipitation is easily precipitated during use. However, at this molar ratio, for the nickel-phosphorus alloy electroplating solution, lactic acid will significantly increase the polarization of nickel ions, and the reduction potential of nickel ions will shift negatively to a large extent, resulting in an increase in the proportion of cathode hydrogen evolution reaction, so the current efficiency of the plating solution is low. Summary of the invention

[0005] In view of the above analysis, the present invention aims to provide a low-stress and high-strength electroplating nickel-phosphorus alloy plating solution and its preparation method and application, providing a stress-controllable and higher-strength nickel-phosphorus alloy material for electroplating replication of large-size and ultra-thin X-ray focusing mirrors.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A low-stress high-strength nickel-phosphorus alloy electroplating solution, comprising nickel sulfamate, lactic acid and / or lactate, phosphorous acid and / or phosphite, saccharin and / or saccharin salt, wherein the solvent of the plating solution is water; the molar ratio of nickel sulfamate to lactic acid and / or lactate is 0.7≤M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐 ≤1, the molar ratio of phosphorous acid and / or phosphorous acid salt to saccharin and / or saccharin salt is 2≤M 亚磷酸和 / 或亚磷酸盐 / M 糖精和 / 或糖精盐 ≤8, the pH value of the plating solution is 3.0-4.5, which can achieve stable low-stress control of the electroplated layer of the plating solution.

[0008] Furthermore, the plating solution also includes boric acid and a wetting agent, the molar concentration of the boric acid is 0.6-0.8 mol / L, and the molar concentration of the wetting agent is 50-500 ppm.

[0009] Furthermore, the molar concentration of the nickel sulfamate is 0.3-0.6 mol / L, the molar concentration of lactic acid and / or lactate is 0.4-0.8 mol / L, the molar concentration of phosphorous acid and / or phosphite is 3.5-25 mmol / L, and the molar concentration of saccharin and / or saccharin sodium is 0.5-9.0 mmol / L.

[0010] Furthermore, the lactate includes one or a mixture of sodium lactate and potassium lactate; the phosphite includes one or a combination of sodium phosphite and potassium phosphite; and the saccharin includes one or a combination of sodium saccharin and potassium saccharin.

[0011] Furthermore, the wetting agent includes one or a mixture of sodium N-lauroyl sarcosinate, sodium lauryl polyoxyethylene ether sulfate, and cetyl trimethyl ammonium bromide.

[0012] A method for preparing the low-stress and high-strength nickel-phosphorus alloy electroplating solution comprises the following steps:

[0013] Step 1, mixing and dissolving nickel sulfamate, lactic acid and / or lactate, boric acid and a wetting agent, and stirring evenly to obtain a nickel sulfamate basic solution;

[0014] Step 2: Dissolve phosphorous acid and / or phosphite, saccharin and / or saccharin salt separately in water and add them to the nickel sulfamate base solution, mix evenly, and then add sulfamate or ammonia water to adjust the pH of the plating solution to the required value to obtain a low-stress and high-strength nickel-phosphorus alloy electroplating solution.

[0015] It should be noted that, in the preparation process of the above-mentioned plating solution, saccharin and / or saccharin salt must be dissolved in water before being added to the plating solution. If the solid is directly added to the plating solution, it will not be completely dissolved.

[0016] An application of the low-stress and high-strength nickel-phosphorus alloy electroplating solution comprises the following steps:

[0017] Step 1, heating the low stress and high strength nickel alloy electroplating solution to 45-60° C.;

[0018] Step 2: The plated part is used as cathode, and the current density range is 0.4~3.0A / dm 2 , electroplating is carried out according to the required coating thickness;

[0019] Step 3: placing a sulfur-containing nickel button or a sulfur-containing nickel ball in a titanium blue as an anode, and the plated workpiece as a cathode, the height of the sulfur-containing nickel button or the sulfur-containing nickel ball in the titanium blue is equal to the height of the cathode plated workpiece, and the ratio of the area of ​​the titanium blue to the area of ​​the cathode plated workpiece is between 3:1 and 1:1;

[0020] Step 4: Before formal electroplating, take out part of the plating solution, use the bent cathode method to measure the stress at different current densities, and perform polynomial fitting on the measured stress value and the current density to obtain the relationship curve between the internal stress of the coating and the current density, so as to determine the zero stress current density;

[0021] Step 5: During the formal electroplating process, a constant current power supply is used to power the electroplating process according to the zero stress current density determined in step 4; the pH of the plating solution is monitored regularly and the amount of aminosulfonic acid or ammonia added is adjusted to maintain the stability of the pH of the plating solution; phosphorous acid and / or phosphites, saccharin and / or saccharin salts are added to the plating solution according to the consumption rate of phosphorous acid and / or phosphites, saccharin and / or saccharin salts to maintain the stability of the internal stress of the coating; lactic acid and / or lactate are added to the plating solution according to the increase rate of nickel ion concentration and the molar ratio of aminosulfonic acid nickel and lactic acid and / or lactate in the initial composition of the plating solution to maintain the stability of the internal stress of the coating.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] a) In the low-stress and high-strength nickel-phosphorus alloy electroplating solution provided by the present invention, lactic acid or lactate plays a key role in achieving low-stress and high-strength nickel-phosphorus alloy electroplating. When phosphorous acid or phosphite is introduced into the simple nickel sulfamate salt plating solution, the coating will show very large tensile stress, which is difficult to offset even with compressive stress additives such as saccharin or saccharin salts. Lactic acid or lactate can change the coordination state of nickel ions when precipitation reaction occurs at the cathode, so that the reduction potential of nickel is significantly negatively shifted to be closer to the reduction potential of phosphorus, thereby significantly reducing the internal stress of the nickel-phosphorus alloy coating, so that the internal stress of the coating can be controlled by using compressive stress additives such as saccharin or saccharin salts. The molar ratio of nickel sulfamate, lactic acid and / or lactate in the plating solution is M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐 When the reduction potential of nickel is greater than that of simple nickel ions, the electroplated coating still exhibits a large tensile stress, which cannot be eliminated by using saccharin or saccharin salts. The molar ratio of nickel sulfamate, lactic acid and / or lactate in the plating solution is 0.7≤M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐 When ≤1, the reduction potential of nickel shifts negatively to close to the reduction potential of phosphorus. At this time, the internal stress of the electroplated coating is small, and saccharin or saccharin salt can be used to control the internal stress of the coating near zero stress; the molar ratio of nickel sulfamate, lactic acid and / or lactate in the plating solution is M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐When the molar ratio is less than 0.7, the reduction potential of nickel is more negative than that of phosphorus, and as the molar ratio decreases, the reduction potential difference increases. At this time, the electroplated coating exhibits a large tensile stress, and the cathode hydrogen evolution is serious, and the current efficiency is low. Moreover, when the concentration of nickel sulfamate and lactic acid or lactate in the plating solution increases or decreases according to the molar ratio set in the initial components, there is no significant effect on the internal stress of the coating within a fairly large concentration range. Therefore, it is only necessary to keep the molar ratio of nickel ions to lactate in the plating solution unchanged to stabilize the internal stress of the coating, thereby realizing the preparation of low-stress electroplated nickel-phosphorus alloy X-ray focusing lens.

[0024] b) In the low stress and high strength nickel-phosphorus alloy electroplating solution provided by the present invention, two grain refiners (phosphorous acid or phosphite, and saccharin or saccharin salt) are used at the same time, and the molar ratio of phosphorous acid and / or phosphite to saccharin and / or saccharin salt is 2≤M 亚磷酸和 / 或亚磷酸盐 / M 糖精和 / 或糖精盐 ≤8, and when the concentration of phosphorous acid and / or phosphite is 3.5-25mmol / L, the brightness and strength of the coating can be improved at the same time, and the obtained coating is bright and uniform, with high mechanical strength and good deformation resistance, as shown in Table 3; when the concentration of phosphorous acid and / or phosphite is less than 3.5mmol / L, the mechanical strength of the coating is improved very little; when the concentration of phosphorous acid and / or phosphite is greater than 25mmol / L, the coating will be transformed into an amorphous state, the brittleness will be enhanced, and the mechanical strength will be deteriorated. The X-ray focusing lens plated by the plating solution of the present invention has significantly better strength than pure nickel and nickel-cobalt alloy.

[0025] c) In the low stress and high strength nickel-phosphorus alloy electroplating solution provided by the present invention, phosphorous acid or phosphite mainly plays the role of doping phosphorus atoms into the nickel lattice, significantly refining the grains and improving the mechanical strength of the coating. At the same time, phosphorous acid or phosphite salts will also cause the tensile stress of the coating to increase significantly. Lactic acid or lactate, and, saccharin or saccharin salts are used as dual stress control agents. When the molar ratio of nickel sulfamate, lactic acid and / or lactate in the plating solution is 0.7≤M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐 ≤1, and the molar ratio of phosphorous acid and / or phosphorous acid salt to saccharin and / or saccharin salt is 2≤M 亚磷酸和 / 或亚磷酸盐 / M 糖精和 / 或糖精盐 When ≤8, it mainly plays the role of offsetting the significantly increased tensile stress caused by phosphorous acid or phosphite and stabilizing the stress change in the coating caused by the change of the plating solution composition, and controlling the average internal stress of the coating near zero stress, so that when the X-ray focusing lens is electroplated, the lens basically does not deform.

[0026] d) In the low-stress high-strength nickel-phosphorus alloy electroplating solution provided by the present invention, the concentration of phosphorous acid or phosphite is low, 3.5-25mmol / L, so the current efficiency is much higher than that of the nickel-phosphorus alloy electroplating in the prior art, between 94% and 96%, and the composition of the plating solution changes very little during use, which is easy to maintain; when the concentration of phosphorous acid or phosphite is greater than 25mmol / L, the current efficiency is low, and the maintenance of the plating solution becomes more difficult. The plating solution of the present invention can continuously and stably electroplate and produce nickel-phosphorus alloy X-ray focusing mirror lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A comparison diagram of the coating states of the plating solutions prepared in Comparative Example 1 and Example 1;

[0028] Figure 2 is a curve diagram showing the relationship between the internal stress and the current density of the coatings prepared in Comparative Example 2 and Example 2;

[0029] Figure 3 X-ray diffraction spectra of the coatings prepared in Comparative Example 2 at different current densities;

[0030] Figure 4 X-ray diffraction spectra of the coatings prepared in Example 2 at different current densities;

[0031] Figure 5 The graph is a relationship between the internal stress and the current density of the coatings prepared in Example 3 and Example 4;

[0032] Figure 6 X-ray diffraction spectra of the coatings prepared in Example 3 at different current densities;

[0033] Figure 7 X-ray diffraction spectra of the coatings prepared in Example 4 at different current densities; DETAILED DESCRIPTION

[0034] The technical solution of the present invention will be clearly and completely described below in conjunction with the drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] The low stress and high strength nickel-phosphorus alloy electroplating solution and its preparation method and application of the present invention are described below in combination with Comparative Examples 1 to 3 and Examples 1 to 3.

[0036] It should be noted that in order to better illustrate the influence of the molar ratio of nickel sulfamate, lactic acid and / or lactate and the molar ratio of saccharin and / or saccharin salt, phosphorous acid and / or phosphite on the internal stress and strength of the coating, comparative examples 1 to 3 and embodiments 1 to 3 use the same preparation method, usage method and the same testing method, and only the specific process parameters are different.

[0037] Comparative Example 1

[0038] The invention discloses a nickel-phosphorus alloy electroplating solution, comprising 0.3 mol / L nickel sulfamate, 5 mmol / L phosphorous acid, 0.8 mmol / L sodium saccharin, 0.65 mol / L boric acid, 200 ppm wetting agent, water as solvent, and pH value of the plating solution being 4.2.

[0039] Comparative Example 2

[0040] An electroplating nickel plating solution comprises 0.3 mol / L nickel sulfamate, 0.4 mol / L lactic acid, 0.65 mol / L boric acid, 200 ppm wetting agent, the solvent is water, and the pH value of the plating solution is 4.2.

[0041] Example 1

[0042] A low-stress and high-strength nickel-phosphorus alloy electroplating solution comprises 0.3 mol / L nickel sulfamate, 0.4 mol / L lactic acid, 5 mmol / L phosphorous acid, 0.8 mmol / L saccharin sodium, 0.65 mol / L boric acid, 200 ppm wetting agent, water as solvent, and pH value of the plating solution is 4.2.

[0043] Example 2

[0044] A low-stress and high-strength nickel-phosphorus alloy electroplating solution comprises 0.3 mol / L nickel sulfamate, 0.4 mol / L lactic acid, 24 mmol / L phosphorous acid, 9 mmol / L sodium saccharin, 0.65 mol / L boric acid, 200 ppm wetting agent, water as solvent, and pH value of the plating solution is 4.2.

[0045] Example 3

[0046] A low-stress high-strength nickel-phosphorus alloy electroplating solution comprises 0.6 mol / L nickel sulfamate, 0.8 mol / L lactic acid, 12 mmol / L phosphorous acid, 3 mmol / L sodium saccharin, 0.65 mol / L boric acid, 200 ppm wetting agent, water as solvent, and pH value of the plating solution is 4.2.

[0047] Example 4

[0048] The invention discloses a nickel-phosphorus alloy electroplating solution, comprising 0.3 mol / L nickel sulfamate, 0.4 mol / L lactic acid, 12 mmol / L phosphorous acid, 3 mmol / L sodium saccharin, 0.65 mol / L boric acid, 200 ppm wetting agent, water as solvent, and pH value of the plating solution is 4.2.

[0049] The contents of the components in the plating solutions of Comparative Examples 1 to 2 and Examples 1 to 4 of the present invention are shown in Table 1.

[0050] Table 1

[0051]

[0052] The preparation method of the plating solution of Comparative Example 1 comprises the following steps:

[0053] Step 1: Add 1500 ml of deionized water into container A, add nickel sulfamate, boric acid and wetting agent according to the component contents under stirring, mix and stir evenly to obtain a nickel sulfamate basic solution;

[0054] Step 2: Weigh phosphorous acid and sodium saccharin according to the component content, dissolve phosphorous acid and sodium saccharin separately in water and add them to the nickel sulfamate base solution, mix and stir evenly, add deionized water to dilute the solution to 2.5L, and adjust the pH to 4.2 by adding aminosulfonic acid (or ammonia water) to the plating solution to obtain 2.5L of plating solution.

[0055] The preparation method of the plating solution of Comparative Example 2 comprises the following steps:

[0056] Step 1: Add 1500 ml of deionized water to container A, add nickel sulfamate, lactic acid, boric acid and wetting agent according to the component content under stirring, mix and stir evenly, add deionized water to dilute the solution to 2.5 L, and adjust the pH to 4.2 by adding aminosulfonic acid (or ammonia water) to the plating solution to obtain 2.5 L of plating solution.

[0057] The method for preparing the low-stress and high-strength nickel-phosphorus alloy electroplating solution of embodiments 1 to 4 of the present invention comprises the following steps:

[0058] Step 1: Add 1500 ml of deionized water into container A, add nickel sulfamate, lactic acid, boric acid and a wetting agent according to the component contents under stirring, mix and stir evenly to obtain a nickel sulfamate basic solution;

[0059] Step 2: Weigh phosphorous acid and sodium saccharin according to the component content, dissolve phosphorous acid and sodium saccharin separately in water, and then add them to the nickel sulfamate base solution, mix and stir evenly, add deionized water to dilute the solution to 2.5L, and adjust the pH to 4.2 by adding an aqueous solution of aminosulfonic acid to the plating solution to obtain 2.5L of plating solution.

[0060] The application of the plating solution of comparative examples 1 to 2 and the low-stress and high-strength electroplating nickel-phosphorus alloy plating solution of embodiments 1 to 4 of the present invention comprises the following steps:

[0061] Step A: heating the low stress and high strength electroplating nickel-phosphorus alloy plating solution at a temperature ranging from 45 to 60° C.;

[0062] Step B: The plated part is used as cathode, and the current density range is 0.4~3.0A / dm 2 , electroplating is carried out according to the required coating thickness;

[0063] Step C: placing a sulfur-containing nickel button or a sulfur-containing nickel ball in a titanium blue as an anode, the height of the sulfur-containing nickel button or the sulfur-containing nickel ball in the titanium blue is equal to the height of the cathode plated piece, and the ratio of the area of ​​the titanium blue to the area of ​​the cathode plated piece is between 3:1 and 1:1;

[0064] Step D: before formal electroplating, take out part of the plating solution, use the bent cathode method to measure the stress at different current densities, and perform polynomial fitting on the measured stress value and the current density to obtain the relationship curve between the internal stress of the coating and the current density, thereby determining the zero stress current density;

[0065] Step E: During the formal electroplating process, a constant current power supply is used to power the electroplating process according to the zero stress current density determined in step D; the pH of the plating solution is monitored regularly and the amount of aminosulfonic acid added is adjusted to maintain the stability of the pH of the plating solution; phosphorous acid and sodium saccharin are added to the plating solution according to the consumption rate of phosphorous acid and sodium saccharin to maintain the stability of the internal stress of the coating; lactic acid is added to the plating solution according to the increase rate of nickel ion concentration and the molar ratio of aminosulfonic acid nickel and lactic acid in the initial composition of the plating solution to maintain the stability of the internal stress of the coating.

[0066] See Table 2 for the process parameters in the methods of use of Comparative Examples 1 to 2 and Examples 1 to 4 of the present invention.

[0067] Table 2 Process parameters in the use methods of comparative examples 1 to 3 and embodiments 1 to 3 of the present invention

[0068] Bath temperature / ℃ Plating time / min <![CDATA[Current density / A / dm 2 > Comparative Example 1 50 60 1.6 Comparative Example 2 50 48～120 0.8～2.0 Example 1 50 60 1.6 Example 2 50 48～120 0.8～2.0 Example 3 50 48～120 0.8～2.0 Example 4 50 48～120 0.8～2.0

[0069] The test methods of Comparative Examples 1 to 2 and Examples 1 to 4 of the present invention are as follows:

[0070] A stress test piece coated with a certain thickness of nickel-phosphorus coating is fixed, and the curvature of the stress test piece is measured using a laser rangefinder, and then the average internal stress of the coating is calculated according to the modified Stony formula, and the obtained stress value is nonlinearly fitted with the corresponding current density to obtain a stress-current density relationship curve, and the current density of the coating when zero stress is obtained; an X-ray diffractometer (XRD) is used to measure the X-ray diffraction spectrum of the coating; a Vickers hardness tester is used to measure the microhardness of the zero stress coating obtained in Comparative Example 2 and Examples 2 to 4, and five points are measured for each sample, and the hardness is averaged, see Table 3. The mass of the plated part before and after electroplating is measured to obtain the actual coating mass, and the actual coating mass is divided by the theoretical coating mass, which is the current efficiency. The current efficiency of the zero stress coating obtained in Comparative Example 2 and Examples 2 to 4 is shown in Table 4.

[0071] Table 3 Microhardness of the zero stress coatings obtained in Comparative Example 2 and Examples 2 to 4.

[0072]

[0073]

[0074] Table 4 Current efficiency of the zero stress coating obtained in Comparative Example 2 and Examples 2 to 4.

[0075] Comparative Example 2 Example 2 Example 3 Example 4 Current efficiency 96.57％ 94.65％ 95.02％ 95.42％

[0076] Comparison of the coating states of the plating solutions prepared in Comparative Example 1 and Example 1 Figure 1 .from Figure 1 It can be seen that the coating electroplated in Comparative Example 1 shows obvious cracking of the coating caused by excessive tensile stress, and the excessive tensile stress of the coating causes the substrate to curl and deform; while the coating electroplated in Example 1 has basically no deformation on the whole test piece, which shows that the stress of the coating is very small, and the coating surface is dense and defect-free, with significant metallic luster and brightness. The composition of the plating solution of Comparative Example 1 and Example 1 is the same except for lactic acid, which shows that lactic acid can significantly reduce the tensile stress of the coating. The relationship curve between the internal stress and current density of the coating prepared in Comparative Example 2 and Example 2 can be found in Figure 2 .from Figure 2 It can be seen that when sodium saccharin and phosphorous acid are introduced into the plating solution at the same time, the internal stress of the coating prepared by the plating solution can be controlled to remain basically unchanged by controlling the ratio of sodium saccharin and phosphorous acid. Figure 3 and Figure 4 .from Figure 3 and Figure 4It can be seen that after sodium saccharin and phosphorous acid are simultaneously introduced into the plating solution, the diffraction peak of the X-ray diffraction spectrum of the coating becomes significantly broadened and the grain size becomes significantly smaller; in Comparative Example 2, the plating solution does not contain sodium saccharin and phosphorous acid, and the crystal plane texture index of the prepared coating does not change with the current density; while in Example 2, the plating solution contains sodium saccharin and phosphorous acid, and the texture index of the (111) crystal plane of the prepared coating increases with the increase of the current density, while the texture index of the (200) crystal plane decreases. The relationship curve between the internal stress and current density of the coatings prepared in Example 3 and Example 4 can be found in Figure 5 .from Figure 5 It can be seen that when the molar ratio of nickel sulfamate and lactic acid in the plating solution is doubled, the internal stress of the coating does not change substantially, and the zero stress current density is 1.6 A / dm 2 The X-ray diffraction spectra of the coatings prepared in Example 3 and Example 4 at different current densities are shown in Figure 6 and Figure 7 .from Figure 6 and Figure 7 It can be seen that when the molar ratio of the concentration of nickel sulfamate and lactic acid in the plating solution is doubled, the texture index of the (111) crystal plane of the coating under different current densities increases, while the texture index of the (200) crystal plane decreases; when the composition of the plating solution remains unchanged, as the current density increases, the texture index of the (111) crystal plane continues to increase, while the texture index of the (200) crystal plane continues to decrease. The microhardness of the zero stress coating obtained in Comparative Example 2 and Examples 2 to 4 is shown in Table 3. As can be seen from Table 3, the microhardness of the zero stress coating prepared in Example 3 and Example 4 is 704HV and 690HV, respectively, which is very similar, indicating that doubling the molar ratio of the concentration of nickel sulfamate and lactic acid has basically no effect on the microhardness of the coating; the microhardness of the zero stress coating prepared in Comparative Example 2 and Example 2 is 271HV and 717HV, respectively, indicating that the simultaneous introduction of saccharin sodium and phosphorous acid into the plating solution significantly improves the resistance to plastic deformation of the coating. The current efficiency of the zero stress coating obtained in Comparative Example 2 and Examples 2 to 4 is shown in Table 4. As can be seen from Table 4, the current efficiency of the plating solution is above 94% as a whole, which is in a relatively high range. The nickel ion concentration increases slowly during the electroplating process, and the plating solution is easy to maintain.

[0077] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A low stress and high strength nickel-phosphorus alloy electroplating solution, characterized in that: The plating solution comprises nickel sulfamate, lactic acid and / or lactate, phosphorous acid and / or phosphorous acid, saccharin and / or saccharin salt, wherein the solvent of the plating solution is water; the molar ratio of nickel sulfamate to lactic acid and / or lactate is 0.7≤M 氨基磺酸镍 / M 乳酸和 / 或乳酸盐 ≤1, the molar ratio of phosphorous acid and / or phosphorous acid salt to saccharin and / or saccharin salt is 2≤M 亚磷酸和 / 或亚磷酸盐 / M 糖精和 / 或糖精盐 ≤8, and the pH value of the plating solution is 3.0-4.

5.

2. The low stress and high strength nickel-phosphorus alloy electroplating solution according to claim 1, characterized in that: The plating solution also includes boric acid and a wetting agent. The molar concentration of the boric acid is 0.6-0.8 mol / L, and the molar concentration of the wetting agent is 50-500 ppm.

3. The low stress and high strength nickel-phosphorus alloy electroplating solution according to claim 1, characterized in that: The molar concentration of the nickel sulfamate is 0.3-0.6 mol / L, the molar concentration of lactic acid and / or lactate is 0.4-0.8 mol / L, the molar concentration of phosphorous acid and / or phosphite is 3.5-25 mmol / L, and the molar concentration of saccharin and / or saccharin sodium is 0.5-9.0 mmol / L.

4. The low stress and high strength nickel-phosphorus alloy electroplating solution according to claim 1, characterized in that: The lactate includes one of sodium lactate and potassium lactate or a mixture of the two; the phosphite includes one of sodium phosphite and potassium phosphite or a combination of the two; the saccharin includes one of sodium saccharin and potassium saccharin or a combination of the two.

5. The low stress and high strength nickel-phosphorus alloy electroplating solution according to claim 2, characterized in that: The wetting agent includes one or a mixture of sodium N-lauroyl sarcosinate, sodium lauryl polyoxyethylene ether sulfate, and cetyl trimethyl ammonium bromide.

6. A method for preparing the low-stress and high-strength nickel-phosphorus alloy electroplating solution according to any one of claims 2 to 5, characterized in that: The following steps are involved: Step 1, mixing and dissolving nickel sulfamate, lactic acid and / or lactate, boric acid and a wetting agent, and stirring evenly to obtain a nickel sulfamate basic solution; Step 2: Dissolve phosphorous acid and / or phosphite, saccharin and / or saccharin salt separately in water and add them to the nickel sulfamate base solution, mix evenly, and then add sulfamate or ammonia water to adjust the pH of the plating solution to the required value to obtain a low-stress and high-strength nickel-phosphorus alloy electroplating solution.

7. An application of the low stress and high strength nickel-phosphorus alloy electroplating solution according to claims 1-5, characterized in that: The following steps are involved: Step 1, heating the low stress and high strength nickel alloy electroplating solution to 45-60° C.; Step 2: The plated part is used as cathode, and the current density range is 0.4~3.0A / dm 2 , electroplating is carried out according to the required coating thickness; Step 3: The sulfur-containing nickel button or sulfur-containing nickel ball is placed in the titanium blue as the anode, and the plated part is used as the cathode; Step 4: Before formal electroplating, take out part of the plating solution, use the bent cathode method to measure the stress at different current densities, and perform polynomial fitting on the measured stress value and the current density to obtain the relationship curve between the internal stress of the coating and the current density, so as to determine the zero stress current density; Step 5: During the formal electroplating process, a constant current power supply is used to power the electroplating process according to the zero stress current density determined in step 4; the pH of the plating solution is monitored regularly and the amount of aminosulfonic acid or ammonia added is adjusted to maintain the stability of the pH of the plating solution; phosphorous acid and / or phosphites, saccharin and / or saccharin salts are added to the plating solution according to the consumption rate of phosphorous acid and / or phosphites, saccharin and / or saccharin salts to maintain the stability of the stress inside the coating; lactic acid and / or lactate are added to the plating solution according to the increase rate of nickel ion concentration and the molar ratio of aminosulfonic acid nickel and lactic acid and / or lactate in the initial composition of the plating solution to maintain the stability of the stress inside the coating.

8. The use according to claim 7, characterized in that: The height of the sulfur-containing nickel button or sulfur-containing nickel ball in the titanium blue is equal to the height of the cathode plated part, and the ratio of the area of ​​the titanium blue to the area of ​​the cathode plated part is between 3:1 and 1:1.

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