Palladium-nickel alloy electroplating solution

Abstract

The invention relates to a palladium-nickel alloy electroplating solution which comprises 45-55 g / L of tetraammine palladium sulfate, 30-40 g / L of nickel aminosulfonate, 120-160 g / L of ammonium sulfate, 20-40 g / L of urea, 20-30 ml / L of complexing agent, 3-6 ml / L of brightening agent and 1-2 ml / L of wetting agent. And the high-speed continuous plating process specification is as follows: PH is 6.8-7.5, the temperature is 50-60 DEG C, the cathode current density is 20-50A / dm < 2 >, and the anode is a titanium anode. Through pulse electroplating, the alloy plating layer contains 75-85% of palladium and 15-25% of nickel, has excellent electrical properties and corrosion resistance, can completely replace a gold plating layer or a hard gold layer, and saves more than 20% of precious metals. The complexing agents adopted by the invention are divided into two types, wherein the type A is hydroxyethyl and hydroxypropyl compounds of organic amine; and the type B is a macromolecular organic amine polyurea quaternary ammonium salt cationic compound. The brightener adopted by the invention is pyridine, thiazole and imidazole heterocyclic derivatives. Through combined application of the complexing agent and the brightening agent, the technical problem that the palladium content in the palladium-nickel alloy coating is unstable is solved.

Description

Technical Field

[0001] The invention belongs to the field of electronic electroplating, and in particular relates to a palladium-nickel alloy electroplating solution. Background Art

[0002] Palladium-nickel alloy plating (80% palladium and 20% nickel) replaces pure gold plating or hard gold plating, and can meet the quality standards of gold plating in terms of contact resistance, brazing, wear resistance, ductility and corrosion resistance. At the same time, it can save about 25% of precious metals. Therefore, the relative stability of the two metal contents in the palladium-nickel alloy plating is crucial.

[0003] In recent years, with the vigorous development of the electronics industry, the various electrical properties, physical properties and corrosion resistance of electronic components have extremely high requirements. While electronic electroplating is developing rapidly in scale and intelligence, cost reduction and efficiency improvement are also the inevitable choice of the industry. Now that the price of gold is high, the best plating layer to replace gold plating is still palladium-nickel alloy plating.

[0004] The stability of the traditional palladium-nickel alloy electroplating process is insufficient in the following aspects: 1. Most of them use palladium chloride (or palladium chloride ammonia) as the main salt, but its disadvantages are: chloride ions are oxidized into chlorine gas or other chlorates at the anode, which have an oxidizing effect on other organic matter in the plating solution; if the residual chloride ions on the coating are not completely washed away in the water washing tank, the corrosion resistance of the alloy coating will be affected, resulting in failure of the salt spray test. Therefore, tetraammine palladium sulfate is now used as the main salt.

[0005] 2. The traditional process uses nickel chloride or nickel sulfate as nickel salt, which causes the alloy coating to have large internal stress and is prone to cracking. However, the use of nickel sulfamate as nickel salt reduces the internal stress of the coating and makes the coating crystallization more uniform and delicate.

[0006] 3. Traditional processes rarely use organic complexing agents. Instead, they rely mainly on ammonia water to stabilize the plating solution. At 50-60°C, the pH value is high and ammonia water is volatile, making the plating solution unstable. At the same time, the odor is strong and the production environment is poor.

[0007] 4. Traditional processes generally use weaker brighteners such as benzene sulfonate, naphthalene sulfonate, sodium saccharin, sodium sulfonate benzaldehyde, etc. The added amount is large and it is easy to fog. The alloy coating has a high sulfur content and contains more organic matter, which affects the appearance and corrosion resistance of the coating.

[0008] 5. The traditional process has a fatal disadvantage due to the lack of chelating agent: after the newly prepared plating solution has been used for a period of time, or after a week of shutdown, the palladium content in the coating will drop significantly, sometimes to 30-40%. Even if more palladium chloride is added, the palladium content in the coating cannot be increased to about 80%. The plating solution can only be scrapped and the palladium salt recovered, causing great losses.

[0009] In summary, the traditional palladium-nickel alloy electroplating process cannot meet the process stability requirements required for modern intelligent large-scale production. Summary of the invention

[0010] The problem to be solved by the present invention is to provide a palladium-nickel alloy electroplating solution. The palladium-nickel alloy coating produced by the palladium-nickel alloy electroplating solution can not only replace the gold coating and meet the electrical properties and various physical properties of the coating, but also meet the process stability requirements required for modern intelligent large-scale production.

[0011] The technical solution provided by the present invention is: a palladium-nickel alloy electroplating solution, which is composed of: 45-55g / L tetraammine palladium sulfate, 30-40g / L nickel sulfamate, 120-160g / L ammonium sulfate, 20-40g / L urea, 20-40mI / L complexing agent, 3-6mI / L light shell agent, 1-2mI / L wetting agent and the balance of water. The complexing agent is composed of component A, component B and water, component A is a hydroxyethyl or hydroxypropyl compound of an organic amine, and component B is a high molecular weight organic amine polyurea quaternary ammonium salt cationic compound.

[0012] The present invention adopts two types of complexing agents, AB, to stabilize the plating solution. The type A complexing agent refers to hydroxyethyl and hydroxypropyl compounds of ethylenediamine, polyene polyamine, and polyethylene imine substances, such as pentahydroxyethyl diethylenetriamine, tetrahydroxypropyl ethylenediamine, and polyethylene imine hydroxyethyl compounds (molecular weight of about 1500). The addition amount of the type A complexing agent is 5-15g / L, and generally 8-12g / L.

[0013] The B-type complexing agent of the present invention is an organic amine polyurea quaternary ammonium salt cationic compound, and its molecular weight is between 2000-3000. Its structure is as follows: NN dimethyl propylamine or NN dimethyl ethylenediamine reacts with urea to deaminize to generate amine urea N(CH3)2-CH2-CH2-CH2-NHCONH-CH2-CH2-CH2-N(CH3)2, and then reacts with crosslinking agent dichloroethyl ether or dichloroethane to generate a high molecular polyurea quaternary ammonium salt cationic compound. On the basis of screening, the organic amine of the present invention is selected from N,N dimethyl ethylenediamine, and the crosslinking agent is selected from dichloroethane, and it is named as B complexing agent, and its content in the electroplating solution is 3-4g / L.

[0014] Two types of complexing agents, AB, are mixed and used, with the composition of 30-40% of type A, 10-20% of type B, and the rest is water. The amount added to the electroplating solution is 20-40ml / L. Based on long-term experience, the complexing agent consumption is 1500-2000ml / KAH.

[0015] The brightener used in the present invention is a highly polar and highly adsorbent heterocyclic derivative of pyridine, thiazole and imidazole, such as benzyl nicotinate, trigonelline, 2-vinyl-1-pyridinepropanesulfonic acid ylide, trans-3-(3-pyridyl)allylic acid, tetrahydrothiazolidinethione, methylthioimidazole, etc. In the brightener, the total amount of various heterocyclic derivatives is about 15%, and the rest is water. The brightener dosage in the plating solution is 3-6 ml / L.

[0016] According to long-term experience, the consumption of brightener is 300-500ml / KAH.

[0017] The present invention adopts a low-foaming wetting agent, which is composed of 20% sodium monoisooctyl sulfosuccinate, 5% sodium 2-ethylhexyl sulfonate, and the rest water, with an addition amount of 1-2 ml / L and a consumption of 30-40 ml / KAH, so as to make the surface tension lower than 45 millinewtons / meter and reduce the porosity of the coating.

[0018] The palladium-nickel alloy plating layer produced by the palladium-nickel alloy electroplating solution of the present invention can not only replace the gold plating layer, meet the electrical properties and various physical properties of the plating layer, but also meet the process stability requirements required for modern intelligent large-scale production. It meets the electrical properties and various physical properties of the gold plating layer. It can also save about 25% of precious metals. DETAILED DESCRIPTION

[0019] The invention discloses a palladium-nickel alloy electroplating solution, which is composed of 45-55 g / L tetraammine palladium sulfate, 30-40 g / L nickel sulfamate, 120-160 g / L ammonium sulfate, 20-40 g / L urea, 20-40 ml / L complexing agent, 3-6 ml / L light shell agent, 1-2 ml / L wetting agent and the balance of water. The complexing agent is composed of component A, component B and water, component A is a hydroxyethyl or hydroxypropyl compound of an organic amine, and component B is a high molecular weight organic amine polyurea quaternary ammonium salt cationic compound.

[0020] The present invention uses tetraammine palladium sulfate instead of palladium chloride, which prevents chloride ions from being oxidized on the anode to generate chlorine gas or other chlorates, and prevents residual chloride ions from affecting the corrosion resistance of the coating due to subsequent incomplete washing.

[0021] The present invention adopts nickel sulfamate as the nickel salt. In the field of electronic electroplating, the plating layer obtained by using nickel sulfamate is dense and fine, and has better ductility and brazing property.

[0022] The present invention adopts ammonium sulfate as a conductive salt, and its content is 120-160 g / L, and is designed for production operation to maintain a low ammonia content (30-50 g / L) of the plating solution. Under a neutral condition of pH 6.8-7.5, ammonia is not easy to volatilize and lose. At the same time, ammonium sulfate serves as a palladium and nickel coordination source to initially form palladium ammine complex ions and nickel ammine complex ions, thereby avoiding the formation of hydroxide precipitation under neutral conditions.

[0023] The present invention uses urea as a buffer and stabilizer. Urea has a certain reducing property, which is beneficial to the reduction of palladium ammine complex ions; its decomposition products are beneficial to stabilize the pH value of the plating solution. In the existing literature, there is no finding that urea is used as a buffer and stabilizer in palladium nickel electroplating solution. According to long-term experience, the consumption of urea is about 2000g / KAH. (KAH is kiloampere hour, the same below) The present invention adopts two types of complexing agents, AB, to stabilize the plating solution. The type A complexing agent (complexing agent A) refers to hydroxyethyl and hydroxypropyl compounds of ethylenediamine, polyene polyamine, and polyethyleneimine. Such as pentahydroxyethyl diethylenetriamine, tetrahydroxypropyl ethylenediamine, and polyethyleneimine hydroxyethyl compounds (molecular weight of about 1500). This type of substance has a small molecular weight and is easy to form mixed coordination ions with nickel ammine complex ions to inhibit the precipitation of nickel. Because the stability constants of palladium ammonia, nickel ammine complex ions, and many complexing agent ligands cannot be found, they can only be screened through experiments. Experiments have shown that in the mixed ligand system formed by complexing agents such as citrate, tartrate, maleate, disodium EDTA, sodium nitrilotriacetate, HEDP, trisodium thiocyanate, etc., with palladium ammine complex ions and nickel ammine complex ions, palladium has no obvious precipitation advantage. The addition amount of type A complexing agent is 5-15g / L, and generally 8-12g / L is used.

[0024] The class B complexing agent of the present invention is an organic amine polyurea quaternary ammonium salt cationic compound, and its molecular weight is between 2000-3000. Its structure is as follows: NN dimethyl propylamine or NN dimethyl ethylenediamine reacts with urea to generate amine urea N(CH3)2-CH2-CH2-CH2-NHCONH-CH2-CH2-CH2-N(CH3)2, and then reacts with a cross-linking agent dichloroethyl ether or dichloroethylene to generate a high molecular weight polyurea quaternary ammonium salt cationic compound. Based on screening, the organic amine of the present invention is selected from N,N dimethyl ethylenediamine, and the cross-linking agent is selected from dichloroethylene. The complexing agent of type B is named complexing agent B, and its content in the plating solution is 3-4g / L. Complexing agent B has good dispersing ability for the mixed coordination system and can significantly widen the current density distribution range: 1. It increases the upper limit of current density and avoids scorching, peeling and cracking in the high current area; 2. It widens the lower limit of current density, so that the low current density area (deep hole of the workpiece) can be well plated. Complexing agent B ensures the stable operation of high-speed electroplating. The content of type B complexing agent cannot be too high, which will affect the overall current efficiency and pH stability.

[0025] Two types of complexing agents, AB, are mixed and used, with the composition of 30-40% of type A, 10-20% of type B, and the rest is water. The amount added to the electroplating solution is 20-40ml / L. Based on long-term experience, the complexing agent consumption is 1500-2000ml / KAH.

[0026] The brightener used in the present invention is a highly polar and highly adsorbent heterocyclic derivative of pyridine, thiazole and imidazole, such as benzyl nicotinate, fenugreek alkali, 2-vinyl-1-pyridine propane sulfonic acid ylide, trans-3-(3-pyridyl)allylic acid, tetrahydrothiazolidinethione, methylthioimidazole and the like. Conventional phenylsulfonates, naphthalenesulfonates and benzaldehydesulfonates can only plate misty or semi-bright palladium-nickel alloy coatings, and the dosage is very large, generally 5-10 g / L, resulting in a large sulfur content in the coating, and a lot of organic inclusions, which affects the appearance and corrosion resistance of the coating. The brightener used in the present invention can increase cathode polarization, refine grains, and make the alloy coating smooth and bright. In the brightener, the total amount of various heterocyclic derivatives is about 15%, and the rest is water. The brightener dosage in the electroplating solution is 3-6 ml / L.

[0027] According to long-term experience, the consumption of brightener is 300-500ml / KAH.

[0028] The present invention adopts a low-foaming wetting agent, which is composed of 20% sodium monoisooctyl sulfosuccinate, 5% sodium 2-ethylhexyl sulfonate, and the rest water, with an addition amount of 1-2 ml / L and a consumption of 30-40 ml / KAH, so as to make the surface tension lower than 45 millinewtons / meter and reduce the porosity of the coating.

[0029] The present invention uses the above-mentioned palladium-nickel alloy electroplating solution to plate palladium-nickel alloy, comprising the following steps: terminal substrate degreasing, acid activation, electroplating semi-bright sulfamate nickel, electroplating sulfamate nickel-phosphorus alloy, electroplating palladium-nickel alloy, sealing, and drying; using titanium anode as anode, electroplating the treated terminal substrate, and the pH of the electroplating solution is 6.8-7.5. The process specifications are as follows: High-speed palladium-nickel alloy electroplating process specification of the present invention Temperature 50-60℃ PH 6.8-7.5 Anode Insoluble Titanium Anode Cathode current density 20-50A Stirring strong air stirring and liquid flow Deposition rate 20A / dm2 0.9 microns / minute Current efficiency 90~95% Maintenance method: 1. Tetraamminepalladium sulfate, nickel sulfamate, and ammonium sulfate are replenished daily based on analysis results, or at any time based on online monitoring data.

[0030] 2. The temperature and pH value are adjusted according to online monitoring. Dilute sulfuric acid and ammonia water are used to adjust the pH value.

[0031] 3. Complexing agent, brightener, wetting agent and urea should be added according to the kiloampere-hour amount set by the automatic adding machine.

[0032] 4. The control of current depends on the complexity and thickness requirements of the workpiece, and the technicians control it based on experience.

[0033] 5. When the ratio of complexing agent and brightener is out of balance, the Hull cell test should be used to adjust the dosage.

[0034] The performance comparison of the palladium-nickel alloy coating obtained by the present invention and the pure gold coating is shown in Table 1. Table 1 Test items Palladium Nickel Alloy Ordinary hard gold Test equipment and conditions or standards Alloy composition (weight ratio) Palladium 75-85% Nickel 15-25% 99.9% Guangrui EDX fluorescence spectrometer Appearance Silver-white coating Golden yellow coating Visual inspection Shock resistance mΩ 2.5~5 1.5~2 Keithley Resistance Tester Ductility ＞8% Super ASTM489 Hardness (HV) 400-500 110 Microhardness tester Density g / cm³ 11.3~11.6 17 Meddes Density Meter Solderability good very good 260℃ solder bath immersion for 3-5 seconds Corrosion resistance 500 times / 2μm No bottom No bottom Use gold-plated sockets and manually plug and unplug experiments <![CDATA[H2S Resistance Test]]> No color change No color change <![CDATA[Exposed to 1% H2S gas at a temperature of 25°C and a humidity of 90% for 1 hour]]> Neutral salt spray test 24 hours pass 24 hours pass Base material 68 brass, no primer and sealing thickness 4μm It can be seen from the above table that the palladium-nickel alloy coating produced by the present invention can completely replace the gold coating, meet the electrical properties and physical properties of the gold coating, and can also save about 25% of precious metals.

[0035] The following five examples of the present invention are carried out under standard electroplating solution and the same operating specifications, and different combinations of complexing agents and brighteners are tested to obtain various properties of palladium-nickel alloy coatings.

[0036] After the five case experiments were completed, the plating solution was left for 15 days and then the same experiment was repeated. The two alloy coatings were tested at the same time to obtain the best ratio of complexing agent and brightener.

[0037] Standard plating solution Tetraamminepalladium sulfate 50g / L (Metallic Palladium) (20g / L) Nickel sulfamate 34g / L (Metallic Nickel) (8g / L) Ammonium sulfate 130g / L Urea 30g / L Wetting agent 2ml / L pH 7.0 Standard operating conditions Temperature 55℃ Cathode current density 20A / d㎡ Stirring air agitation and liquid flow Anode Titanium anode Cathode 0.3mmx30mmx100mm68 brass sheet The time is 3-5 minutes. It depends on the thickness required by the experiment.

[0038] Current efficiency 90-93% In the following five examples, the preparation of the electroplating solution 1. Add 70% of the set volume of pure water to the plating tank, raise the temperature to about 55°C, and add the meter Calculate the amount of complexing agent A and complexing agent B and stir evenly.

[0039] 2. Add the calculated amount of ammonium sulfate, urea, tetraamminepalladium sulfate and aminosulfonate nickel in sequence and stir to dissolve.

[0040] 3. Finally, add the calculated amount of brightener and wetting agent, and add water to the set volume.

[0041] 4. Use ammonia water and diethyl sulfuric acid to adjust the pH value to within the specified range, and then try plating.

[0042] In the following five examples, the preparation method of complexing agent B is 1. Synthesis of urea-dimethylaminoethane: The molar ratio of N, N-dimethylaminoethylenediamine to urea is 2:1 Add to the reactor, stir while adding, and add nitrogen to the reactor at the same time. Heat to 80-90℃, keep warm for 10 hours, then heat to 120℃ for 2 hours, and recover the ammonia released by the reaction.

[0043] Synthesis of copolymer: urea dimethylaminoethane: 1.2 dichloroethane: water in a molar ratio of 1.1:1:10 Add to the reactor, stirring while adding. Reflux at 80℃ for 10 hours, then add a small amount of molecular weight regulator (nicotinic acid, the amount is about 0.03% of the total weight of the reaction solution), keep warm for 3 hours, detect the molecular weight range (2000-3000), add activated carbon for decolorization after passing the test, and then distill out the excess water.

[0044] The solid content is 50%, which is complexing agent B.

[0045] In the following five examples, the complexing agent B is the same.

[0046] The following five examples are used in the formulation of the wetting agent Sodium monoisooctane sulfonate succinate (Sasol Chemical) 20% Sodium Ethyl Hexyl Sulfonate (BASF) 5% The rest is pure water.

[0047] Example 1: Complexing agent: Complexing agent A: Tetrahydroxypropylethylenediamine 12g / L Complexing agent B 3 / L Brightener: 2-vinyl-1-pyridine propane sulfonic acid Onium salt 300mg / L Methimazole 5mg / L Example 2: Complexing agent: Complexing agent A: Pentahydroxyethyldiethylenetriamine Complexing agent B 4g / L Brightener: Benzyl nicotinate 300mg / L Trigonelline 300mg / L Thiathiazolidine 0.5mg / L Example 3: Complexing agent: Complexing agent A: Pentahydroxyethyldiethylenetriamine 10g / L Complexing agent B 3.5g / L Brightener: trans-3-(3-pyridyl)allylic acid 400 mg / L Thiathiazolidine 0.5g / L Example 4: Complexing agent: Complexing agent A: Tetrahydroxypropylethylenediamine 10g / L Complexing agent B 3.5g / L Brightener: trans-3-(3-pyridine)allylic acid 400 mg / L Methimazole 5mg / L Thiathiazolidine 0.2g / L Example 5: Complexing agent: Complexing agent A: Polyethyleneimine hydroxyethyl compound 10 g / L Complexing agent B 3.5g / L Brightener: trans-3-(3-pyridyl)allylic acid 400mg / L Vinyl-1-pyridinepropane sulfonic acid Onium salt 200mg / L Methimerosal 5mg / L Table 2 Performance of palladium nickel alloy coatings from Example 1 to Example 5 Test items Example 1 Example 2 Example 3 Example 4 Example 5 Alloy composition Pd73.8%Ni26.2% Pd75.6%Ni24.4% Pd78.3%Ni21.7% Pd80.5%Ni19.5% Pd81.7%Ni18.3% Sample after 15 days Pd72.3%Ni27.7% Pd75.2%Ni24.8% Pd77.7%Ni22.3% Pd80.0%Ni20.0% Pd81.5%Ni18.5% Coating appearance Uniform brightness Even brightness slightly dim Good brightness and good vibration Good brightness and good vibration Bright and smooth Sample after 15 days Uniform brightness Uniform bright yellowish Good brightness and smoothness Good brightness and smoothness Bright and smooth Contact resistance mΩ 4.8 5.6 4.6 4.5 4.2 Sample after 15 days 4.6 5.4 4.5 4.5 4.1 Ductility 7.6 7.4 8.2 8.3 8.5 Sample after 15 days 7.6 7.4 8.1 8.3 8.5 Hardness (HV) 460 450 460 490 460 Sample after 15 days 460 440 450 480 450 Density g / cm³ 11.5 11.3 11.4 11.5 11.6 Sample after 15 days 11.5 11.3 11.4 11.5 11.6 Solderability good good good good good Sample after 15 days good good good good good Abrasion resistance: 500 times / 2μm No bottom No bottom No bottom No bottom No bottom Sample after 15 days No bottom No bottom No bottom No bottom No bottom <![CDATA[Anti-H2S experiment, thickness 2 / μm, 1 hour]]> No color change Dim No color change No color change No color change Sample after 15 days No color change Dim No color change No color change No color change Neutral salt spray test thickness 4 / μm 24 hours pass 24 hours pass 24 hours pass 24 hours pass 24 hours pass Sample after 15 days 24 hours pass 24 hours pass 24 hours pass 24 hours pass 24 hours pass Conclusion: 1. Under the action of urea and two types of complexing agents, the palladium-nickel alloy electroplating solution can be used stably for a long time, ensuring the normal operation of high-speed electroplating. A high-quality palladium-nickel alloy coating is obtained, which can completely replace the gold coating.

[0048] 2. Practice has proved that trans-3-(3-pyridyl)allylic acid, 2-vinyl-1-pyridinepropanesulfonic acid ylide, and methylthioimidazole are excellent brighteners with small addition amounts and excellent performance.

Claims

1. A palladium-nickel alloy electroplating solution, which consists of: 45-55 g / L of tetraammine palladium sulfate, 30-40 g / L of nickel sulfamate, 120-160 g / L of ammonium sulfate, 20-40 g / L of urea, 20-30 ml / L of complexing agent, 3-6 ml / L of brightener, 1-2 ml / L of wetting agent, and the balance is water; wherein the complexing agent consists of component A, component B and water, component A is a hydroxyethyl or hydroxypropyl compound of an organic amine; component B is a high molecular weight organic amine polyurea quaternary ammonium salt cationic compound.

2. The palladium-nickel alloy electroplating solution according to claim 1, characterized in that: The weight percentage of component A in the complexing agent is 30-40%, the weight percentage of component B is 10-20%, and the urea content is 20-30g / L.

3. The palladium-nickel alloy electroplating solution according to claim 1 or 2, characterized in that: The component A is a reactant of ethylenediamine, polyene polyamine or polyethyleneimine with ethylene oxide or propylene oxide; the component B is an organic amine polyurea quaternary ammonium salt cationic compound generated by the reaction of ureaamine substances with a crosslinking agent β,β' dichlorodiethyl ether or 1,2 dichloroethane, and its molecular weight is between 2000 and 3000, wherein the ureaamine substances are generated by deamination of dimethylaminopropylamine or dimethylaminoethylenediamine with urea.

4. The palladium-nickel alloy electroplating solution according to claim 3, characterized in that: The component A is tetrahydroxypropylethylenediamine, pentahydroxyethyldiethylenetriamine or polyhydroxyethylpolyethyleneimine with a molecular weight lower than 1500.

5. The palladium-nickel alloy electroplating solution according to claim 1 or 2, characterized in that: The brightener is an aqueous solution of 10-20wt% pyridine, thiazole or imidazole heterocyclic derivatives.

6. The palladium-nickel alloy electroplating solution according to claim 5, characterized in that: The heterocyclic derivative in the brightener is 2-vinyl-1-pyridine propane sulfonic acid ylide, trans-3-(3-pyridyl)allylic acid, trigonelline, tetrahydrothiazolidinethione or methylthioimidazole.

7. The palladium-nickel alloy electroplating solution according to claim 1 or 2, characterized in that: The wetting agent consists of 20 wt % of sodium monoisooctyl sulfosuccinate, 5 wt % of sodium ethylhexyl sulfonate and the remainder of water.