CN101838830B - Electrolyte of electroplating palladium-nickel alloy - Google Patents

Abstract

The invention relates to electrolyte of an electroplating palladium-nickel alloy, in particular to electrolyte. The invention provides electrolyte which can electroplate bright, compact and needle-hole-free electroplating palladium-nickel alloy with different nickel contents (10 to 40 percent), which comprises major salt, complexing agent, additive, conductive salt and pH stabilizer; the major salt comprises a palladium salt and a nickel salt, calculating at the metal palladium, the content of the palladium salt is 1 to 10 g/L, and the mol ratio of the palladium salt and the nickel slat is 1: 1 to 3; the concentration of the complexing agent is 0.2 to 1.0 mol/L; the content of the additive is 0.01 to 1.0 g/L; the content of the conductive salt is 20 to 100 g/L; and the pH stabilizer is of 20 to 50 g/L boric acid or 30 to 90 g/L pyroborate.

Description

A kind of electrolytic solution for electroplating palladium-nickel alloy

technical field

The invention relates to an electrolytic solution, in particular to an electrolytic solution for electroplating a palladium-nickel alloy.

Background technique

Gold has excellent corrosion resistance, electrical conductivity and ductility, and is widely used as a finishing metal for electrical contacts and connectors in the electronics industry. The price of gold is expensive, and the search for substitutes for gold plating to save costs has aroused widespread concern. Many properties of palladium are similar to gold, such as corrosion resistance, ductility, etc., and palladium is cheaper, has a lower density, and its application cost is much lower than that of gold. The palladium alloy coating can not only further reduce the cost, but also significantly reduce the hydrogen absorption phenomenon of the pure palladium coating, and improve the ductility, wear resistance, contact resistance and brightness of the palladium coating. Therefore, palladium and its alloys are considered to be the most likely metals or alloys to replace or save gold.

In addition, palladium and its alloys can also be used as the bottom layer, barrier layer, electrical contact coating, and socket coating of high-end decorations, and are widely used in decorative industries, electronics industries, micro-electromechanical processing and other industries.

Palladium and nickel belong to the same family and have similar properties. The thermodynamic stability of palladium-nickel alloy is good. Because nickel is cheap, has good corrosion resistance and low contact resistance, palladium-nickel alloy is currently the most commonly used palladium alloy.

At present, there are very few domestic studies on electroplating palladium-nickel alloys. The focus of foreign research is to achieve the purpose of high-speed electroplating and ammonia-free electroplating through the selection of complexing agents and additives. There is no report on the process technology of electroplating high nickel content and electroplating palladium-nickel alloys with different nickel contents according to requirements; There is no report on the additives that determine the effect.

In the palladium-nickel alloy, the nickel content has a great influence on the properties of the coating. The palladium-nickel alloy coating with different nickel content has different hardness and different thermodynamic stability, and of course it also has different applications. At present, the palladium-nickel alloy coating with a nickel mass content of about 20% has been widely used, but the palladium-nickel alloy with a high nickel mass content has no industrial application.

For the same plating solution, within a certain range of current density, the mass content of nickel in the palladium-nickel alloy coating obtained by electroplating should basically remain unchanged. US Patent No. 4,849,303 pointed out that after adding a small amount of iodide ions to the plating solution, the mass change of nickel in the palladium-nickel alloy coating obtained under different current densities does not exceed 3%.

Contents of the invention

The invention aims to provide a bright, dense and pinhole-free electroplating palladium-nickel alloy electrolytic solution capable of electroplating different nickel mass contents (10%-40%).

The electrolytic solution of the electroplating palladium-nickel alloy of the present invention comprises main salt, complexing agent, additive, conductive salt and pH stabilizer; Said main salt comprises palladium salt and nickel salt, calculates with metal palladium, and the content of palladium salt is 1 ~10g/L, in molar ratio, palladium salt: nickel salt is 1: (1 ~ 3); the concentration of the complexing agent is 0.2 ~ 1.0mol/L; the content of the additive is 0.01 ~ 1.0g/L ; The content of the conductive salt is 20-100g/L; the pH stabilizer is 20-50g/L boric acid or 30-90g/L pyroborate.

The palladium salt can be selected from palladium chloride, dichlorodiammine palladium, dichlorotetraammine palladium, diammonium palladium sulfate, tetraammine palladium sulfate, ammonium nitrite palladium, ammonium nitrate palladium, oxalate diammonia palladium, etc. A sort of.

The nickel salt may be selected from at least one of nickel sulfate, nickel chloride, nickel sulfamate and the like.

The complexing agent can be selected from at least one of ammonia water, ethylenediamine, aminoacetic acid, triethanolamine, ethanolamine, diethylenediamine, triethylenetetramine, citric acid and its salts, tartaric acid and its salts, and the like.

The additive may be selected from at least one of propenylthiourea, nicotinic acid, nicotinamide, pyridinetrisulfonic acid, acrylamide, saccharin, sodium benzenesulfinate, propynyl alcohol, butynediol, and the like.

The conductive salt may be selected from at least one of ammonium chloride, sodium chloride, potassium chloride, sodium sulfate, ammonium sulfate, ammonium nitrate, potassium nitrate and the like.

The conditions for electroplating are: the pH range of the plating solution is 6.5-10; the current density is 0.1-2.0A/dm ² ; the temperature of the plating solution is 20-50°C; during electrolysis, stir at a medium speed; use platinum-plated titanium mesh, graphite , stainless steel, etc. are insoluble anodes, and the area ratio of cathode and anode is 1: (1~3).

The nickel mass content can reach up to 40%.

The electrolytic solution of the present invention, the palladium salt is mainly composed of palladium chloride, palladium dichloride, tetraammine palladium dichloride, palladium diamine sulfate, palladium tetraammine sulfate, palladium ammonium nitrite, palladium ammonium nitrate or palladium diammine oxalate The nickel salt is mainly introduced in the form of nickel sulfate, nickel chloride or nickel sulfamate. The ratio of palladium to nickel content in the plating layer increases with the increase of the ratio of palladium salt to nickel salt in the plating solution, but when the nickel mass content in the plating layer exceeds 40%, the nickel mass content basically no longer increases with the nickel salt content in the plating solution. change with further improvement. The content of the palladium salt (calculated as metal palladium) is 1-10 g/L. The higher the palladium content in the plating solution, the faster the plating speed, but the greater the palladium loss; if the palladium content in the plating solution is too low, palladium must be added frequently, and the maintenance cost will increase. The nickel salt is added according to the molar ratio of palladium salt to nickel salt 1: (1-3).

The electrolytic solution of the present invention, the complexing agent is mainly one of ammonia, ethylenediamine, aminoacetic acid, triethanolamine, ethanolamine, diethylenediamine, triethylenetetramine, citric acid and its salt, tartaric acid and its salt or several. The concentration is 0.2～1.0mol/L. In the electrolyte containing these complexing agents, a bright palladium-nickel alloy coating can be obtained. When using ammonia water as a complexing agent, attention should be paid to properly reducing the temperature and pH value of the plating solution to hinder the volatilization of ammonia water.

The electrolyte of the present invention, the additive is mainly propenylthiourea, nicotinic acid, nicotinamide, pyridine trisulfonic acid, acrylamide, saccharin, sodium benzenesulfinate, sodium dodecylsulfonate, propynyl alcohol or butane One or more of acetylenic diols, the content is 0.01-1.0g/L. Sodium dodecylsulfonate not only acts as a surfactant but also as a brightener, allylthiourea, acrylamide, saccharin, nicotinamide, propynyl alcohol, butynediol, sodium benzenesulfinate, etc. It's a brightener. When the current density is high, it is necessary to add a small amount of nicotinic acid, pyridine trisulfonic acid or nicotinamide. Only when additives are used together can a bright, dense, pinhole-free palladium-nickel alloy coating be obtained.

The electrolytic solution of the present invention, the conductive salt is one or more of ammonium chloride, sodium chloride, potassium chloride, sodium sulfate, ammonium sulfate, ammonium nitrate or potassium nitrate. The content is 20-100g/L.

In the electrolytic solution of the present invention, the pH stabilizer is 20-50 g/L boric acid or 30-90 g/L pyroborate. Within this pH range, the properties of the electrolyte are stable, and the resulting coating has superior performance. When the pH value of the plating solution is low, the coating is white-gray; when the pH value of the plating solution is high, the nickel content in the coating will decrease.

In the electroplating condition of the present invention, the electrolytic solution is weakly alkaline, and the preferred pH range is 6.5-10.

In the electroplating conditions of the present invention, the electroplating is carried out at a current density of 0.1 to 2.0 A/dm ² . When the current density is too high, the nickel content of the coating will decrease. This is because, with the increase of current density, the increase of palladium deposition rate is greater than that of nickel deposition rate. However, for the same plating solution, if the current density is in the range of 0.1-2.0A/ ^dm2 , the nickel mass content of the obtained palladium-nickel alloy coating will not change more than 4%. When the current density is too small, the electrodeposition efficiency decreases and the cost increases.

The electroplating condition of the present invention is that the temperature is 20-50°C. When the temperature is too high, the surface of the coating will be fogged. When the temperature is too low, the nickel mass content in the coating will decrease.

By adjusting the composition of the plating solution and the electroplating conditions, palladium-nickel alloy coatings with different nickel contents can be obtained, and the highest nickel mass content can reach 40%. With the use of additives, palladium-nickel alloy coatings with different nickel contents, bright, dense, and pinhole-free can be obtained.

Detailed ways

Provide below the preparation method of the electrolytic solution of described electroplating palladium-nickel alloy (taking preparation 1 liter as example):

1. Add the main salt palladium salt into a container containing 100mL of deionized water, heat, add ammonia water dropwise, stir, and dissolve to obtain solution A;

2. Add the main salt nickel salt into a container containing 100mL deionized water, heat, stir, and dissolve to obtain solution B;

3. Add complexing agent, conductive salt and pH stabilizer into a container containing 400mL of deionized water, heat, stir, and dissolve to obtain solution C;

4. Add solution A and solution B into solution C, stir evenly to obtain solution D;

5. Add the additive into a container containing 100mL deionized water, heat, stir, and dissolve, then add it to solution D to obtain solution E;

6. Add lye such as ammonia water, sodium hydroxide or potassium hydroxide solution into solution E to make the pH range between 6.5 and 10. Additional deionized water was added to bring the total volume of the solution to 1000 mL.

Example 1

1) The composition of the plating solution and the electroplating conditions are as follows

Dichlorodiammine palladium (calculated as palladium) 2g/L

Nickel sulfate hexahydrate 25g/L

Ammonium chloride 30～50g/L

Boric acid 40～50g/L

Ammonia water 30～60ml/L

Sodium dodecyl sulfonate 0.1～0.5g/L

Propylene Glycol 0.05～0.4g/L

Saccharin 0.1～0.5g/L

pH (adjusted with ammonia water) 6.5～8

Current density 0.5～1A/ ^dm2

Temperature 45℃

Anode Platinized Titanium Mesh

The area ratio of cathode to anode is 1:2

Stir at medium speed during plating.

2) Coating test results: see Table 1, contact resistance evaluation standard: SJ2431-84, the general gold coating contact resistance is less than 0.6mΩ.

Table 1

Example 2

1) The composition of the plating solution and the electroplating conditions are as follows

Tetraammine palladium sulfate (calculated as palladium) 6g/L

Nickel chloride hexahydrate 25g/L

Sodium chloride 30～50g/L

Sodium pyroborate decahydrate 50～80g/L

Ethylenediamine 10～30g/L

Sodium dodecyl sulfonate 0.1～0.5g/L

Niacin 0.05～0.4g/L

Sodium benzenesulfinate 0.05～0.5g/L

pH (adjusted with ammonia water) 6.5～7.5

Current density 1～1.5A/ ^dm2

Temperature 50℃

Anode Graphite

The area ratio of cathode to anode is 1:2

Stir at medium speed during plating.

2) Coating test results: see Table 2.

Table 2

Example 3

1) The composition of the plating solution and the electroplating conditions are as follows

Ammonium palladium nitrite (as palladium) 8g/L

Nickel sulfamate 40g/L

Ammonium sulfate 30～60g/L

Boric acid 30～40g/L

Glycine 15～30g/L

Acrylamide 0.2～0.5g/L

Niacinamide 0.05～0.4g/L

Sodium dodecyl sulfonate 0.05～0.5g/L

pH (adjusted with ammonia water) 7～9

Current density 1～1.5A/ ^dm2

Temperature 30℃

Anode Stainless Steel

The area ratio of cathode to anode is 1:3

Stir at medium speed during plating.

2) Coating test results: see Table 3.

table 3

Example 4

1) The composition of the plating solution and the electroplating conditions are as follows

Diammonium palladium oxalate (calculated as palladium) 10g/L

Nickel sulfate hexahydrate 45g/L

Potassium chloride 30～50g/L

Sodium pyroborate decahydrate 40～80g/L

Potassium citrate 40～60g/L

Butynediol 0.1～0.5g/L

Pyridine trisulfonic acid 0.05～0.2g/L

Sodium dodecyl sulfonate 0.05～0.5g/L

pH (adjusted with ammonia water) 6.5～8

Current density 1～2A/ ^dm2

Temperature 40℃

Anode Stainless Steel

The area ratio of cathode to anode is 1:2

Stir at medium speed during plating.

2) Coating test results: see Table 4.

Table 4

In the present invention, as the mass content of nickel in the coating increases, the hardness and wear resistance of the coating increase significantly, thereby greatly improving its service life as an electrical contact coating. The palladium-nickel alloy coating with high nickel mass content still has low contact resistance and qualified solderability. The coating is bright, dense, and pinhole-free, which fully meets the requirements for application in the electronics industry.

In the present invention, the change of the mass content of nickel is not more than 4% for the coating obtained by the same plating solution in the range of current density of 0.1-2.0A/ ^dm2 .

In the invention, by adjusting the ratio of palladium salt and nickel salt in the plating solution and appropriate process conditions, the mass content of nickel in the obtained palladium-nickel alloy coating can be changed between 10% and 40% according to requirements, and the highest can reach 40%. Moreover, the obtained palladium-nickel alloy coatings with different nickel mass contents all have lower contact resistance, qualified weldability and better wear resistance.

Claims (1)

1. an electrolytic solution for electroplating palladium-nickel alloy, is characterized in that comprising main salt, complexing agent, additive, conductive salt and pH stabilizer; Described main salt comprises palladium salt and nickel salt, calculates with metallic palladium, palladium salt The content of palladium salt is 1～10g/L, and in molar ratio, palladium salt: nickel salt is 1: (1～3); The concentration of described complexing agent is 0.2～1.0mol/L; The content of described additive is 0.01～ 1.0g/L; the content of the conductive salt is 20-100g/L; the pH stabilizer is 20-50g/L boric acid or 30-90g/L pyroborate; The palladium salt is selected from at least one of palladium chloride, dichlorodiammine palladium, dichlorotetraammonia palladium, diammonia palladium sulfate, tetraammine palladium sulfate, ammonia palladium nitrite, ammonia palladium nitrate, and diammonia palladium oxalate ; The nickel salt is selected from at least one of nickel sulfate, nickel chloride, and nickel sulfamate; The complexing agent is selected from at least one of ammonia water, ethylenediamine, aminoacetic acid, triethanolamine, ethanolamine, diethylenediamine, triethylenetetramine, citric acid and its salts, tartaric acid and its salts; The additive is selected from at least one of propenylthiourea, nicotinic acid, nicotinamide, pyridine trisulfonic acid, acrylamide, saccharin, sodium benzenesulfinate, propynyl alcohol, butynediol; The conductive salt is selected from at least one of ammonium chloride, sodium chloride, potassium chloride, sodium sulfate, ammonium sulfate, ammonium nitrate, and potassium nitrate; The preparation method of the electrolytic solution of described electroplating palladium-nickel alloy is as follows: (1) Add the palladium salt into a container containing 100 mL of deionized water, heat, add ammonia water dropwise, stir, and dissolve to obtain solution A; (2) Add nickel salt into a container containing 100 mL of deionized water, heat, stir, and dissolve to obtain solution B; (3) Add complexing agent, conductive salt and pH stabilizer into a container containing 400mL deionized water, heat, stir, and dissolve to obtain solution C; (4) adding solution A and solution B to solution C, stirring evenly to obtain solution D; (5) Add the additive into a container containing 100mL of deionized water, heat, stir, and dissolve, then add it to solution D to obtain solution E; (6) Add lye to solution E to make the pH range 6.5 to 10, add deionized water to make the total volume of the solution 1000mL, and the lye is selected from ammonia water, sodium hydrochloride or hydrochloride potassium chloride solution.