High-brightness pyrophosphate copper plating additive, electrolyte and copper plating method thereof

Abstract

The invention relates to the technical field of copper plating electrolyte, in particular to a high-brightness pyrophosphate copper plating additive, electrolyte and a copper plating method thereof. The high-brightness pyrophosphate copper plating additive comprises the following substances in parts by weight: 15-30 parts of a polyhydroxy compound; 0.5 to 2.5 parts of a sulfur-containing organic compound; 80 to 120 parts of lauryl sodium sulfate; and 5-15 parts of organic phosphonate. The problem that the glossiness of a pyrophosphate copper plating layer is insufficient is solved through the synergistic effect of quaternary components; the polyhydroxy compound and copper ions can form a weak complex, the deposition rate is adjusted, and grains are refined; the sulfur-containing organic compound is adsorbed to a cathode active site, so that the polarization effect of the cathode is enhanced, and transverse growth of crystal grains is inhibited; the organic phosphonate can maintain balance of metal ions in the plating solution, and precipitation caused by excessive consumption of main salt is avoided. Through the synergistic effect of the four components, the concentration of free copper ions can be reduced, longitudinal arrangement of crystal grains is promoted, a mirror surface structure coating is formed, and meanwhile negative effects on the service life of the plating solution are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of copper plating electrolyte, in particular to a high-brightness pyrophosphate copper plating additive, an electrolyte and a copper plating method thereof. BACKGROUND

[0002] Copper is the earliest used metal, even in modern times, copper is one of the indispensable roles in industrial production. In the field of electroplating, copper plating is the most widely used pre-plating layer. In order to improve the adhesion of the plating layer, a layer of copper needs to be plated on the metal workpiece before nickel plating, silver plating and gold plating. The earliest copper plating process is cyanide copper plating. The plating layer obtained by using this process is uniform and dense, has strong adhesion to the substrate, and has good gloss. However, due to the high cost and high toxicity of cyanide, and the difficulty in treating wastewater, this process has been replaced by pyrophosphate copper plating.

[0003] As a typical non-cyanide process, compared with cyanide copper plating, this process does not need to worry about the toxicity of cyanide, and the plating solution composition is simple, the maintenance cost is low, the cost of wastewater treatment is also much lower than that of cyanide copper plating process, and the tolerance to other impurities in the plating solution during electroplating is also high.

[0004] For the above prior art, the inventors found that the disadvantages of pyrophosphate copper plating technology are also obvious. At low current, the deposition rate of copper ions is lower than that of cyanide copper plating, and the preparation efficiency of high-thickness plating layer is low. The plating solution of some processes needs to be heated, which increases the energy consumption cost, and compared with sulfate, the cost of pyrophosphate is higher. In terms of plating layer, the gloss of pure pyrophosphate copper plating layer is not enough, and additional copper plating brightener needs to be added, and the decomposition of the brightener upon heating may also affect the service life of the plating solution. SUMMARY

[0005] In order to improve the defects existing in the prior art, the present application provides a high-brightness pyrophosphate copper plating additive and an application method thereof.

[0006] In a first aspect, the present application provides a high-brightness pyrophosphate copper plating additive, which adopts the following technical scheme: A high-brightness pyrophosphate copper plating additive comprises the following substances by weight: 15-30 parts of a polyhydroxy compound; 0.5-2.5 parts of a sulfur-containing organic compound; 80-120 parts of sodium dodecyl sulfate; and 5-15 parts of an organic phosphonate.

[0007] By the technical scheme, the application solves the problem of insufficient gloss of pyrophosphate copper plating layer through synergistic effect of the four components: the multi-hydroxy compound can form a weak complex with copper ions to regulate the deposition rate and refine the crystal grains; the sulfur-containing organic compound can be adsorbed on the active sites of the cathode to enhance the cathode polarization and inhibit the lateral growth of the crystal grains; the sodium dodecyl sulfate as a surfactant can improve the dispersion capacity of the plating solution and improve the flatness of the plating layer; and the organic phosphonate can maintain the balance of metal ions in the plating solution to avoid precipitation caused by excessive consumption of the main salt. The synergistic effect of the four components can reduce the concentration of free copper ions, promote the vertical arrangement of the crystal grains, form a mirror structure plating layer, and reduce the negative impact on the service life of the plating solution.

[0008] Further, the multi-hydroxy compound includes at least one of glycerol, ethylene glycol, and propylene glycol.

[0009] By the technical scheme, the application limits the specific type of multi-hydroxy compound, and the multi-hydroxy compound such as glycerol has a molecular structure containing multiple hydroxyl groups, which can form a stable weak complex with copper ions through hydrogen bonds to further optimize the nucleation rate in the deposition process; at the same time, such compounds have good water solubility and chemical stability and are not easy to decompose within the temperature range of electroplating, which can ensure the performance consistency of the plating solution during long-term use.

[0010] Further, the sulfur-containing organic compound includes at least one of thiourea, thiosulfate, or mercaptobenzothiazole.

[0011] By the technical scheme, the application limits the sulfur-containing organic compound to at least one of thiourea, thiosulfate, or mercaptobenzothiazole, and introduces a specific sulfur-containing group to enhance the cathode polarization and crystal grain control ability. The sulfur atom in the thiourea compound has a lone pair of electrons, which can be preferentially adsorbed on the high-activity crystal face of the copper crystal to inhibit the growth in that direction, promote the crystal to preferentially orient in the crystal face, and thus form a smooth and bright plating layer; the thiosulfate can act as an auxiliary complexing agent to cooperatively adjust the reduction potential of copper ions with the main salt to avoid side reactions such as hydrogen evolution; and the mercaptobenzothiazole has both adsorption and corrosion inhibition effects, which can reduce the pinholes and sand defects of the plating layer.

[0012] Further, the organic phosphonate includes at least one of hydroxyethylidene diphosphonic acid or amino-trimethylene phosphonic acid.

[0013] By the technical scheme, the organic phosphonate salt molecule contains multiple phosphonic acid groups, can form a stable complex with metal ions in the plating solution, prevents the main salt from precipitating due to excessive consumption, and has strong buffering capacity to the pH value of the plating solution, so that the quality of the plated layer is reduced due to the pH fluctuation in the electroplating process. The hydroxyethylidene diphosphonic acid also has oxidation resistance, can inhibit the oxidation of impurity ions in the plating solution, and prolongs the service life of the plating solution; the aminotrimethylene phosphonic acid can further enhance the cathode polarization through the adsorption of the amino group, and cooperates to refine the grains. The limitation selects the organic phosphonate salt with a specific functional group, so that the additive can maintain high brightness while considering the long-term stability of the plating solution, and solves the technical defect that the traditional brightener is easy to decompose.

[0014] In a second aspect, the application provides a pyrophosphate copper plating electrolyte, comprising the high-brightness pyrophosphate copper plating additive according to any one of the preceding aspects.

[0015] By the technical scheme, the additive is combined with the main salt such as copper pyrophosphate and potassium pyrophosphate to form a complete electroplating system, the additive and the main salt are synergistically optimized, and the best brightness effect can be achieved without additional adjustment; the organic phosphonate salt forms a complex complex system with pyrophosphate, further enhancing the dispersion and leveling ability of the plating solution; at the same time, the stability of the electrolyte is improved, the cost of frequent replacement of the plating solution is reduced, and the production efficiency is improved.

[0016] Further, the mass fraction of the high-brightness pyrophosphate copper plating additive is 0.01-0.2%.

[0017] By the technical scheme, the mass fraction of the additive in the electrolyte is optimized to balance the performance of the plated layer and the stability of the plating solution. Too low an amount of the additive may result in insufficient brightness, and too high an amount of the additive may inhibit the deposition rate due to excessive adsorption, and even cause accumulation of organic impurities. Within the range of 0.01-0.2%, the components of the additive can fully play a synergistic role, ensuring grain refinement and crystal face orientation control, and avoiding precipitation of the main salt or increase in the brittleness of the plated layer.

[0018] Further, the pyrophosphate copper plating electrolyte further comprises the following substances by weight: Copper pyrophosphate 60-80 parts; Potassium pyrophosphate 350-400 parts; Ammonia 2-5 parts.

[0019] By the technical solution, the weight parts of copper pyrophosphate, potassium pyrophosphate and ammonia in the electrolyte are further limited, and the technical effect is to optimize the main salt ratio to match the action mechanism of the additive. The ratio of copper pyrophosphate to potassium pyrophosphate directly affects the stability of complex ions, and ammonia as a pH regulator can maintain the alkaline environment of the plating solution and ensure the complexing activity of organic phosphonate. The limitation of the additive by the synergistic design of the main salt and the additive makes the copper ion reduction potential in the optimal range, promotes the selective adsorption of the additive on the cathode surface, and thus realizes the high brightness and low stress of the plated layer. At the same time, the addition of ammonia can inhibit the hydrolysis of pyrophosphate and reduce the generation of phosphate impurities in the plating solution, prolonging the service life of the plating solution.

[0020] In a third aspect, the application provides a method for copper plating, which adopts the following technical solution: A method for copper plating applies a pyrophosphate copper plating electrolyte.

[0021] By the technical solution, the product claim is converted into an implementable process scheme, and by applying the additive and the electrolyte in combination to the copper plating process, the preparation of a high-brightness plated layer can be directly realized without the need for additional addition of other brighteners. The advantage of this method is that it simplifies the step of adjusting the additive multiple times in the existing process, improves the production efficiency; at the same time, the stability of the electrolyte makes the process parameters easy to control, reducing the dependence on the skills of the operators.

[0022] Further, the copper plating parameters include: plating temperature 40-45℃, current density 0.5-2A / dm 2 , plating time 20-40min.

[0023] By the technical solution, the application further improves the quality of the plated layer by optimizing the process conditions. The temperature range ensures the activity of each component of the additive, avoiding decomposition of sulfur-containing compounds at high temperature or slow deposition rate at low temperature; the selection of current density matches the cathodic polarization effect of the additive, which can refine the grain size while ensuring the deposition efficiency; the plating time is adjusted according to the thickness requirement of the plated layer to ensure adaptability in different application scenarios.

[0024] In summary, the application has the following beneficial effects: First, the application effectively solves the problem of insufficient gloss of pyrophosphate copper plating layer through multi-component synergistic effect. The sulfur-containing organic compound in the additive preferentially adsorbs on the cathode active site, enhances the cathode polarization effect, inhibits the lateral growth of crystal grains and promotes the vertical arrangement; the polyhydroxy compound forms a weak complex with copper ions, refines the crystal grains and reduces the deposition overpotential; sodium dodecyl sulfate improves the plating solution dispersion ability and reduces the roughness defects caused by uneven surface tension. The three synergistically promote the copper crystal to preferentially orient to the crystal face, form a mirror surface structure plating layer, and at the same time reduce the surface concave-convex caused by the stress of the crystal grains, realize the synchronous improvement of the brightness and flatness of the plating layer, and meet the application requirements of high decorative plating layer.

[0025] Second, the application can form a stable complex with free metal ions in the plating solution through the organic phosphonate component, avoid the precipitation of copper pyrophosphate due to excessive consumption, maintain the balance of the main salt concentration; the weak complexing property of the polyhydroxy compound adjusts the reduction rate of copper ions, prevents the decomposition of the plating solution caused by sudden local concentration change; the sulfur-containing organic compound is stable in chemical properties within the electroplating temperature range and is not easy to decompose to produce impurity ions. The above effects collectively inhibit the aging of the plating solution, reduce the production interruption caused by frequent replacement of the plating solution, reduce the wastewater treatment cost, prolong the service life of the plating solution compared with the traditional process, and significantly improve the economic efficiency of industrial production.

[0026] Third, the application can maintain a high deposition efficiency at a low current density by regulating the cathode polarization and nucleation rate, solve the technical bottleneck of traditional pyrophosphate copper plating “slow deposition at low current”, the additive forms a complex complexing system with pyrophosphate to improve the dispersion ability of the plating solution; the process does not need high temperature heating, reduces the energy consumption of the sulfuric acid plating copper process which needs heating. In addition, the additive has high tolerance to pH value change of the plating solution, can work stably in a wide range of pH, reduces the quality defects caused by parameter fluctuation, and improves the process stability and industrialization adaptability. DETAILED DESCRIPTION

[0027] The application will be further described in detail below in combination with examples.

[0028] Example 1 A high-brightness pyrophosphate copper plating additive, comprising the following substances: 15 g of glycerol, 0.5 g of thiourea, 80 g of sodium dodecyl sulfate, and 5 g of hydroxyethylidene diphosphonic acid.

[0029] A copper plating electrolyte comprising the following substances: 60 g of copper pyrophosphate, 350 g of potassium pyrophosphate, 2 g of ammonia water, 0.2 g of high-brightness pyrophosphate copper plating additive, and 1 L of deionized water.

[0030] A copper plating method comprising the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40-45℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after the electroplating time of 20 min, washing and drying.

[0031] Example 2 A high-brightness pyrophosphate copper plating additive includes the following substances: 22g of glycerol, 1.5g of thiourea, 100g of sodium dodecyl sulfate, and 10g of hydroxyethylidene diphosphonic acid.

[0032] A copper plating electrolyte includes the following substances: 60g of copper pyrophosphate, 350g of potassium pyrophosphate, 2g of ammonia, 0.2g of high-brightness pyrophosphate copper plating additive, and 1L of deionized water.

[0033] A copper plating method includes the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after the electroplating time of 20-40 min, washing and drying.

[0034] Example 3 A high-brightness pyrophosphate copper plating additive includes the following substances: 30g of glycerol, 2.5g of thiourea, 120g of sodium dodecyl sulfate, and 15g of hydroxyethylidene diphosphonic acid.

[0035] A copper plating electrolyte includes the following substances: 60g of copper pyrophosphate, 350g of potassium pyrophosphate, 2g of ammonia, 0.2g of high-brightness pyrophosphate copper plating additive, and 1L of deionized water.

[0036] A copper plating method includes the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after the electroplating time of 20 min, washing and drying.

[0037] Example 4 A high-brightness pyrophosphate copper plating additive includes the following substances: 22g of glycerol, 1.5g of thiourea, 100g of sodium dodecyl sulfate, and 10g of hydroxyethylidene diphosphonic acid.

[0038] A copper plating electrolyte includes the following substances: 70g of copper pyrophosphate, 375g of potassium pyrophosphate, 3g of ammonia, 0.2g of high-brightness pyrophosphate copper plating additive, and 1L of deionized water.

[0039] A copper plating method includes the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after 20min of electroplating, washing and drying.

[0040] Example 5 A high-brightness pyrophosphate copper plating additive comprises the following substances: 22g of glycerol, 1.5g of thiourea, 100g of sodium dodecyl sulfate, and 10g of hydroxyethylidene diphosphonic acid.

[0041] A copper plating electrolyte comprises the following substances: 80g of copper pyrophosphate, 400g of potassium pyrophosphate, 5g of ammonia water, 0.2g of high-brightness pyrophosphate copper plating additive, and 1L of deionized water.

[0042] A copper plating method comprises the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after 20min of electroplating, washing and drying.

[0043] Example 6 A high-brightness pyrophosphate copper plating additive comprises the following substances: 22g of glycerol, 1.5g of thiourea, 100g of sodium dodecyl sulfate, and 10g of hydroxyethylidene diphosphonic acid.

[0044] A copper plating electrolyte comprises the following substances: 70g of copper pyrophosphate, 375g of potassium pyrophosphate, 3g of ammonia water, 0.2g of high-brightness pyrophosphate copper plating additive, and 1L of deionized water.

[0045] A copper plating method comprises the following steps: The steel piece is placed in the electroplating tank, and the copper plating electrolyte is added. The electroplating temperature is 40℃, the current density is 0.5A / dm 2 The copper plating treatment is completed after 20min of electroplating, washing and drying.

[0046] Comparative Example 1 In comparative example 1, the high-brightness pyrophosphate copper plating additive is not added in the copper plating solution, and the remaining preparation steps and parameters are the same as those in example 1.

[0047] Performance detection The copper plating layers prepared in examples 1-6 and comparative example 1 are detected, and the detection standards are as follows: 1. Gloss: Measured by a 60° angle gloss meter, the unit is gloss unit (GU), refer to the standard "GB / T9754-2007 Paints and varnishes without metallic pigments - Determination of specular gloss at 20°, 60° and 85°".

[0048] 2. Coating appearance: Visually observe and record defects (pinholes, roughness, cracks, etc.), referring to the appearance assessment requirements in the standard "GB / T12334-1990 Definitions and general rules for thickness measurement of metals and other inorganic coatings", and divide them into "excellent (no defects), good (minor defects), poor (obvious defects)".

[0049] 3. Main salt retention rate: After 50 hours of continuous electroplating, the copper pyrophosphate concentration in the plating solution is determined by EDTA titration method, and the concentration retention rate (%) is calculated to reflect the stability of the plating solution.

[0050] 4. Adhesion: The cross-cut test (cross-cut spacing 1mm) was used, with reference to the standard "GB / T9286-1998 Cross-cut test for paint and varnish films", and the rating was from 0 (best, no peeling) to 5 (worst, large-area peeling).

[0051] 5. Microhardness: measured using a Vickers hardness tester (load 100g), unit: HV, refer to the standard "GB / T4340.1-2009 Metallic Materials Vickers Hardness Test Part 1: Test Method".

[0052] The test results are shown in Table 1 below: Table 1 Performance test table

[0053] From the comparison of the results of Examples 1-6 and Comparative Example 1, it can be found that: Comparing Examples 1-6 with Comparative Example 1, Comparative Example 1 does not add a high-brightness pyrophosphate copper plating additive. From the appearance of the coating, the examples have no obvious defects, while Comparative Example 1 has pinholes and hemp sand due to the absence of the additive, indicating that the additive can suppress surface defects.

[0054] The main salt retention rate of Examples 1-6 reached 85-90%, which is much higher than that of the comparative example, reflecting the effect of the additive on improving the stability of the plating solution and reducing the precipitation of the main salt.

[0055] The glossiness of Examples 1-6 is significantly higher than that of Comparative Example 1, indicating that the additive can effectively improve the brightness of the coating. Among them, Example 4 has the highest glossiness due to the optimal ratio of the main salt and the additive.

[0056] The above data further illustrate that the technical scheme of the present application solves the problem of insufficient gloss of pyrophosphate copper plating layer through synergistic effect of the four components: the polyhydroxy compound can form a weak complex with copper ions to regulate the deposition rate and refine the crystal grains; the sulfur-containing organic compound is adsorbed on the active sites of the cathode to enhance the cathode polarization and inhibit the lateral growth of the crystal grains; the sodium dodecyl sulfate as a surfactant can improve the dispersion capacity of the plating solution and increase the flatness of the plated layer; and the organic phosphonate can maintain the balance of metal ions in the plating solution to avoid precipitation caused by excessive consumption of the main salt. The synergistic effect of the four components can reduce the concentration of free copper ions, promote the vertical arrangement of the crystal grains, form a mirror surface structure plated layer, and reduce the negative impact on the service life of the plating solution.

[0057] The present application has been described in detail with reference to specific embodiments and illustrative examples, but these are not to be construed as limiting the present application. Those skilled in the art understand that various equivalent substitutions, modifications or improvements can be made to the technical scheme of the present application and its embodiments without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The scope of protection of the present application is subject to the appended claims.

[0058] All publications, patent applications, patents and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present specification, including definitions, will control.

[0059] When the specification derives materials, substances, methods, steps, devices or components, etc. with the word head "known to those skilled in the art", "prior art" or similar terms, the objects derived by the word head cover those commonly used in the art at the time of the present application, but also include those not commonly used at present, but will be recognized as suitable for similar purposes in the art.

[0060] In the context of the present specification, except for the explicitly stated content, any matter or matter not mentioned is directly applicable to those known in the art without any change.

Claims

1. A high-brightness pyrophosphate copper plating additive, characterized in that: The composition includes the following materials in parts by weight: 15-30 parts of polyol; 0.5-2.5 parts of sulfur-containing organic compounds; 80-120 parts of sodium lauryl sulfate; 5-15 parts of organic phosphonate.

2. A high-brightness pyrophosphate copper plating additive according to claim 1, characterized in that: The polyol comprises at least one of glycerol, ethylene glycol and propylene glycol.

3. A high-brightness pyrophosphate copper plating additive according to claim 1, characterized in that: The sulfur-containing organic compound includes at least one of thiourea, thiosulfate or mercaptobenzothiazole.

4. A high-brightness pyrophosphate copper plating additive according to claim 1, characterized in that: The organic phosphonate includes at least one of hydroxyethylidene diphosphonic acid or aminotrimethylphosphonic acid.

5. A pyrophosphate copper plating electrolyte comprising the high-brightness pyrophosphate copper plating additive according to any one of claims 1 to 4.

6. A pyrophosphate copper plating electrolyte according to claim 5, characterized in that: The mass fraction of the high-brightness pyrophosphate copper plating additive is 0.01-0.2%.

7. A pyrophosphate copper plating electrolyte according to claim 5, characterized in that: The pyrophosphate copper plating electrolyte further comprises the following substances in parts by weight: 60-80 parts of copper pyrophosphate; 350-400 parts of potassium pyrophosphate; 2-5 parts of ammonia water.

8. A copper plating method, characterized in that: The pyrophosphate copper plating electrolyte according to any one of claims 5 to 7 is used.

9. A copper plating method according to claim 8, characterized in that: The copper plating parameters include: electroplating temperature 40-45°C, current density 0.5-2A / dm2, and electroplating time 20-40min.

Images