Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating

doi:10.21203/rs.3.rs-4291415/v1

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Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating

https://doi.org/10.21203/rs.3.rs-4291415/v1

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published 21 Jul, 2024

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Electroless nickel-phosphorus (Ni-P) plating is a widely used surface treatment method due to its excellent corrosion and wear resistance properties. However, the inertness of copper to hypophosphite oxidation necessitates a palladium activation process for the preparation of Ni-P coating on copper. In this study, we present a convenient approach for the deposition of a cobalt layer on copper using galvanic replacement, facilitated by the special complexing ability of iodide. The results demonstrated that the actual potential of copper could be adjusted to be lower than that of cobalt in a solution containing 8 mol/L NaI, enabling the deposition of a cobalt layer on copper in 15 minutes at 90°C. Furthermore, the deposition rate of the cobalt layer was found to increase with the concentration of CoCl₂ in the NaI solution. Importantly, the Ni-P coating obtained through cobalt layer activation exhibited morphology, structure, and corrosion resistance, friction resistance similar to the Ni-P coating obtained using the common palladium activation. Therefore, the cobalt layer prepared on copper through galvanic replacement may serve as a viable alternative to palladium for activating electroless Ni-P plating.

cobalt

galvanic replacement

electroless Ni-P plating

activation

corrosion resistance

tribology performance

The surface treatment process plays a key role in printed circuit board (PCB) reliability as the copper circuit is prone to be oxidated and corroded ^{[1, 2]}. Electroless nickel electroless palladium immersion gold (ENEPIG) is commonly used as the ideal surface treatment process of PCB for its advantages of good flatness, solderability, corrosion and wear resistance ^{[3, 4]}. The ENEPIG process mainly uses the electroless plating method to prepare nickel-phosphorus (Ni-P) coating on the surface of copper circuits first, and then uses galvanic replacement plating or electroless plating to deposit palladium and gold coatings on the Ni-P coating to further improve the corrosion resistance, wear resistance and solderability ^{[5, 6]}.

Electroless Ni-P plating can’t proceed on copper circuits in PCB unless an activation process is conducted on copper first owing to the high energy potential barrier of copper to the oxidation of hypophosphite ^{[7, 8]}. Depositing palladium film on copper circuits by galvanic replacement is commonly adopted as the activation process for PCB owing to the excellent activation ability of palladium ^[9]. However, because the copper circuit in PCB becomes finer and the space between copper circuits is narrower, it is easy to generate Ni-P coatings outside the copper circuits, that is, the phenomenon of overflow plating, resulting in PCB failure due to short circuits ^{[10, 11]}. The reason is that the palladium activation process can lead to the activation of the polymer substrate between the copper circuits, and Ni-P coating will be deposited outside the copper circuits ^{[12, 13]}. In addition, the rising price of palladium leads to the increasingly high cost of the palladium activation process. Therefore, it is needed to develop a low-cost, high-activity, and easy-to-scale palladium-free activation treatment for PCB copper circuits.

In addition to palladium, cobalt can significantly reduce the catalytic oxidation potential of hypophosphite ^{[14, 15]}, and therefore it also has a good activation ability for electroless Ni-P and Co-P plating. Lin et al. reduced cobalt ions adsorbed on the surface of polypyrrole membrane using sodium borohydride, and then prepared a Ni-Sn-P coating on the surface of polypyrrole membrane by cobalt-activated electroless plating, which significantly improved the hydrophilic separation of the membrane by improving its hydrophilicity significantly ^[16]. Zhang et al. prepared Co activators on WC powders by soaking WC powders in a mixed solution of cobalt sulfate heptahydrate and sodium hypophosphite and then heat treated at 220°C, and then achieved electroless cobalt plating on their surface ^{[17, 18]}. Xu et al. used the ion-exchange reaction to chelate Co²⁺ or Ni²⁺ cations on the modified Tencel fabric samples and then prepared Co and Ni activators using potassium borohydride solution reduction^{[19, 20]}. They compared the activation ability of Co and Ni to deposit Co-Ni-P coating on Tencel fabric surfaces, and the comparison study revealed that the Co-Ni-P plating prepared using Co as the activator has better conductivity and magnetic properties ^[19] .

The above research indicated that cobalt had a good activation ability for electroless Ni-P coating, but how to prepare cobalt activation layer on copper surface efficiently becomes a problem. Galvanic replacement is one of the convenient methods to prepare metal nanostructures and layers ^{[20, 21]}. However, since the standard electrode potential of cobalt (Co_2+/Co, − 0.277 V) is lower than that of copper (Cu_2+/Cu, 0.337 V), galvanic replacement deposition of cobalt on copper is generally not possible ^[22].

According to the Nernst equation, the actual potential of a metal varies with ion concentration, complexing agent, and temperature. The change in actual potential may reverse the direction of replacement deposition. For example, tin and nickel could be obtained on copper by galvanic replacement when using particular complexing agents ^{[23, 24]}. In this work, we achieved the galvanic replacement deposition of cobalt on the copper based on the fact that a high concentration of iodine ions in the solution could significantly reduce the actual potential of copper ^[25]. With a fixed concentration of NaI, the concentration of cobalt ions had a significant effect on the replacement deposition of cobalt on copper. The cobalt layer obtained by galvanic replacement was able to act as an activator to initiate the electroless Ni-P plating on copper. The morphology, structure, corrosion resistance, and tribology performance of the Ni-P coating obtained on the as-prepared cobalt layer and common palladium layer were characterized to compare the activation ability of the cobalt layer and palladium layer prepared on copper by galvanic replacement. The results showed that the cobalt layer had comparable activation ability for electroless Ni-P plating, and it could serve as an alternative to palladium for activating electroless Ni-P plating.

2.1. Preparation of cobalt and palladium lays on copper

Pure copper substrates (99.9%) were first ultrasonically cleaned in hydrochloric acid solution (5 wt.%) for 5 min to remove surface oxides and contaminants, then washed with deionized water and alcohol. The cobalt immersion plating solutions containing 0.05, 0.1, 0.2, 0.4, and 0.8 mol/L CoCl₂ were prepared by adding CoCl₂·6H₂O in 8 mol/L NaI solution. The cleaned copper substrates were then immersed into the above solutions separately, and the immersion plating of cobalt layers on copper was carried out at 90°C for 15 min. For comparison, the conventional palladium layer was prepared on copper substrates by immersion plating in a solution containing 15 g/L NH₄Cl and 1 g/L PdCl₂ with a pH value of 2.5 for 1 min at 20°C.

2.2. Preparation of Ni-P plating on cobalt and palladium layers

The copper substrates with cobalt or palladium immersion layer were placed in acidic or alkaline electroless Ni-P plating baths to prepare Ni-P coating: the commercial acidic plating bath (Atotech 1151, pH = 4.5); the alkaline plating bath containing 50 g/L C₆H₅O₇(NH₄)₃, 10 g/L NH₄Cl, 30 g/L NiSO₄·6H₂O and 20 g/L NaH₂PO₂·H₂O (pH = 10.5, adjusted by 40 g/L NaOH solution). The deposition temperature was 85°C and the deposition time was 30 min. After the deposition process, complete and bright Ni-P coatings were obtained on both cobalt and palladium layers. The weight gain of Ni-P coating was used to evaluate the deposition rate of electroless Ni-P plating.

2.3. Characterization of the samples

The surface morphology of cobalt layers and Ni-P coatings on cobalt or palladium layers were characterized by scanning electron microscope (FIB-SEM, Crossbeam 540, Zeiss). The elemental composition of the cobalt layers and Ni-P coatings were determined by energy dispersive X-ray spectrometry (EDS, Oxford) and X-ray photoelectron spectrometry (XPS, ESCALAB 250Xi, Thermo Fisher Scientific). The structure of Ni-P coatings was characterized by X-ray diffractometer (XRD, Empyrean, Panalytical) with a grazing angle of 1°. The thickness of the Ni-P coating was determined by optical microscopy (Olympus, PD73).

2.4. Electrochemical measurements

Electrochemical experiments were performed using an electrochemistry workstation (µAutolab Ш, Metrohm). An Ag/AgCl electrode (in saturated KCl solution) and a Pt plate (1×1 cm²) were used as reference and counter electrodes, respectively. To evaluate the possibility of replacement deposition of cobalt on copper, the open circuit potential (OCP) of pure copper and cobalt sheets in 0.4 mol/L CoCl₂·6H₂O aqueous solution, 8 mol/L NaI solution or 8 mol/L NaI solution containing 0.4 mol/L CoCl₂·6H₂O were measured at room temperature. To evaluate the corrosion resistance of Ni-P coatings activated by cobalt and palladium layers, potentiodynamic polarization tests were performed in a 3.5 wt.% NaCl solution with a scan rate of 5 mV/s after 30 min of OCP measurements.

2.5. Tribological performance test

Before the friction experiment, the surface of the sample was wiped with a dust-free cloth, and the counterface balls was ultrasonically cleaned in ethanol for 5 min to remove surface impurities, and then dried with a hair dryer. Then, the sample and the counterface balls were installed and fixed. When conducting the experiment, three experiments were performed on the same sample under the same conditions, and the three experimental results data were averaged to draw the friction curve. After the friction experiment, the wear track of the Ni-P coatings was first cleaned by ultrasonic in ethanol for 5 min to remove the wear debris on the surface, and then cleaned and dried with deionized water, and then observed by the optical microscope (Olympus, PD73).

3.1. Deposition of cobalt layer on copper by galvanic replacement

As shown in Fig. 1a, the actual potential of cobalt sheet in 0.4 mol/L CoCl₂ solution was − 0.427 V, which was lower than that of copper sheet (− 0.163 V), complying with the metal activity series. Therefore, it was impossible to deposit a cobalt layer on copper by galvanic replacement in CoCl₂ solution. However, the actual potential of copper sheet significantly decreased to − 0.610 V in 8 mol/L NaI solution, while the actual potential of cobalt sheet slightly increased to − 0.195 V. The actual potential of cobalt sheet was higher than that of copper sheet in high concentration NaI solution. That was mainly because of the strong copper complexation and weak cobalt complexation ability of I⁻. In addition, the actual potential of cobalt sheet (− 0.173 V) was still higher than that of copper sheet (− 0.577 V) in 8 mol/L NaI solution containing 0.4 mol/L CoCl₂, indicating that copper was likely to react with cobalt ions in this solution. The special complexation ability of I⁻ made the deposition of cobalt layer on copper by galvanic replacement possible.

The effect of cobalt ion concentration in NaI solution on depositing cobalt layers on the copper substrate by galvanic replacement was explored. The morphological, compositional and structural characterization results shown in Fig. 2 indicated that the cobalt ion concentration had a significant effect on the galvanic replacement reaction rate between copper substrate and cobalt ions in NaI solution. When the concentration of cobalt ion was 0.05 mol/L, a cobalt layer could be obtained on copper, but there were several cracks and pores, which was the typical phenomenon of galvanic replacement deposition. The cobalt layer was mainly composed of nanoparticles with a size of less than 100 nm, suggesting the fast nucleation process of galvanic replacement reaction. The cobalt content in the sample was 7.23 at.%, indicating that only little cobalt could be deposited on the copper surface. When the concentration of cobalt ion increased to 0.1 mol/L and 0.2 mol/L, the cobalt content in the sample increased to 11.43 at.% and 12.28 at.%, and relatively complete cobalt layers could be obtained. However, there were still a few pores in the cobalt layers. When the concentration of cobalt ions continued to raise to 0.4 mol/L and 0.8 mol/L, complete cobalt layers could be obtained on copper and the cobalt content was increased to 17.06 at.% and 19.72 at.%, respectively. The galvanic replacement deposition rate of cobalt layer was increased with the increase of CoCl₂ concentration in the NaI solution. It could also be found that there was some content of iodine element (less than 1 at.%) in all samples, which was generated owing to the high concentration of iodide in the deposition solution.

The diffraction pattern for the cobalt layer obtained from the solution containing 0.4 mol/L Co²⁺ was shown in Fig. 2f. It can be found that there were obvious diffraction peaks of the copper substrate at 43.5°, 50.4°, 74.0°, 89.9° and 95.6° because of the limited thickness of cobalt layer. In addition, the diffraction peak of the cobalt layer at 44.4° was overlayed with the diffraction peak of copper substrate at 43.5°. The diffraction peaks of the cobalt layer at 51.6° was overlayed with the diffraction peak of the copper substrate at 50.4°.

The XPS survey showed the existence of Co, Cu, and I elements in the cobalt layer, which was in good agreement with the EDS analysis results. Figure 3a and 3b presented the high-resolution 2p spectra in the Co (2p) and I (2p) regions for the as-prepared Co layer from the solution containing 0.4 mol/L Co²⁺. The peaks appearing at 780.5 eV and 796.6 eV in Fig. 3a were attributed to Co2p3/2 and Co2p1/2, respectively, which corresponded well to metallic Co, confirming the replacement deposition of cobalt on copper. The satellite peaks at 786.2 eV and 804.5 eV and the corresponding oscillation peaks could be attributed to divalent cobalt owing to the oxidation of cobalt. The distinct I3d5/2 and I3d3/2 peaks at 619.0 eV and 630.7 eV presented in Fig. 3b indicated that partial iodide was generated in the cobalt layers during the replacement deposition of cobalt on copper.

Figure 4a and 4d show the cross-sectional morphology of the cobalt layer. It can be found that a thin cobalt layer with a thickness of about 200 nm had been deposited on the copper substrate, as verified by the element distribution map shown in Fig. 4b and 4c. An obvious interface and some pore defects could be found between the cobalt layer and copper substrate. The pore defects were generated owing to the result of obvious corrosion of the copper substrate caused by the galvanic replacement reaction between the copper substrate and cobalt ions. The cobalt layer was deposited on copper according to the following reactions:

Anodic reaction: Cu + 2I⁻ → [CuI₂]⁻ + e⁻ (1)

Cathodic reaction: Co²⁺ + 2e⁻ → Co (2)

Copper was eroded in the high concentration I⁻ solution and [CuI₂]⁻ was generated because of the strong complexing ability of iodide to copper. Meanwhile, the cobalt ions could be reduced to cobalt and form a compact cobalt layer on copper substrate. This reaction process could be roughly illustrated by Fig. 5.

In order to verify the activation ability of deposited cobalt lay to electroless Ni-P plating, the cobalt layers on copper obtained from 8 mol/L NaI solutions with different Co²⁺ concentrations were immersed in the acidic and alkaline electroless Ni-P plating baths, respectively. Figure 6a shows the weight gain of Ni-P coatings obtained on cobalt layer from acidic or alkaline electroless Ni-P plating bath at 90°C for 30 min. It can be seen that there was no Ni-P coating on the cobalt layer obtained from 0.05 mol/L and 0.1 mol/L CoCl₂ owing to the limited cobalt deposition. When the CoCl₂ concentration increased to 0.2 mol/L, obvious Ni-P could be obtained from both acidic and alkaline electroless plating bath. The weight gain of Ni-P coating (26 mg) in alkaline electroless plating bath was higher than that (14 mg) in acidic electroless plating bath. With the increasing of CoCl₂ concentration in the deposition solution, the weight gain of Ni-P coatings from alkaline electroless plating bath was firstly increased to 36 mg and then decreased to 30 mg. However, the weight gain of Ni-P coating from acidic electroless plating bath was relatively stable. The above results suggested that the sufficient cobalt layer had enough activation ability to initiate electroless Ni-P plating.

The morphology, composition and performance of Ni-P coating on cobalt layer obtained from solution containing 0.4 mol/L was characterized and compared with the Ni-P coating on the traditional palladium layer.

3.2 Morphology, composition of Ni-P coatings on cobalt and palladium layers

As shown in Fig. 7, the acidic Ni-P coating obtained on both cobalt and palladium layers was homogeneous and dense, and the EDS results indicated that the phosphorus content in the Ni-P coatings were 19.80 at.% and 18.80 at.%, respectively. The phosphorus content in the Ni-P coating by cobalt layer activation was a little higher than that of the Ni-P coating by palladium layer activation. The crystal structures of the acidic Ni-P coatings prepared on the surfaces of the nickel and palladium layers were characterized by XRD, and it was observed that the acidic Ni-P coating on the surface of the cobalt and palladium layers had similar structures and both were semi-amorphous. There was a main broad peak with 2θ angular range of about 37–55° which corresponds to the nickel plane.

The detailed composition of the acidic Ni-P coatings on cobalt and palladium layers obtained from acidic electroless plating solution were analyzed by XPS, and the high-resolution spectra of Ni and P elements were shown in Fig. 8. It can be found that both Ni-P coatings showed similar nickel and phosphorus spectra, indicating comparable activation ability of cobalt and palladium.

As shown in the Ni 2p spectra (Fig. 8a and Fig. 8c), most of the cobalt corresponded to nickel metal with binding energies of 851.8 eV and 868.9 eV. Also, there were two other major peaks at 855.5 eV and 873.3 eV and their nearby satellite peaks at binding energies of 858.5 eV and 875.9 eV. This indicated the presence of other nickel-containing compounds due to the oxidation and phosphorylation of nickel ^[26]. The spectra of phosphorus (Fig. 8b and Fig. 8d) expressed that the peaks at 128.6 eV and 129.4 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating ^[27]. In addition, the peak positioned at 132.0 eV could be recognized as the hypophosphites or phosphorus in its intermediate chemical states as the solid solution in Ni-P coatings. The binding energy of the two peaks of phosphorus in the Ni-P coating activated by the cobalt layer was lower than that of the phosphorus peak in the Ni-P coating activated by the palladium layer, which might be due to the fact that the phosphorus content in the Ni-P coating activated by the cobalt layer was higher than that in the Ni-P coating activated by the palladium layer.

As shown in Fig. 9, the surface morphology of the Ni-P coatings on cobalt and palladium layers obtained from alkaline electroless plating solution indicated both Ni-P coatings were uniform and dense. The phosphorus content of Ni-P coating activated by the cobalt layer was 7.50%, which was lower than the phosphorus content of Ni-P coating activated by the traditional palladium layer (9.14%). The crystal structures of the Ni-P coatings on cobalt and palladium layers were characterized by XRD, and the two Ni-P coatings had a similar amorphous structure. There was an obvious broad peak between 44.4° and 51.6° could be indexed to the combination of (111) and (200) planes. The other weak and broad peaks at 76.1° and 92.1° could be indexed to (220) and (311) plane of nickel.

Figure 10 presents the XPS spectra of Ni-P coatings on cobalt layer and palladium layer obtained from alkaline electroless plating solution, and it can be found that the Ni2p and P2p fine spectra of Ni-P coating activated by cobalt and palladium layers are similar, indicating that the activation capacities of cobalt and palladium are equivalent. From the Ni2p fine spectra (Fig. 10a and Fig. 10c), it can be seen that most of the elemental nickel in the Ni-P coating corresponded to metallic nickel with binding energies of 852.00 eV and 869.1 eV, respectively. Also, the remaining two main peaks at 855.6 eV and 873.4 eV, respectively, as well as the nearby satellite peaks at 858.3 eV and 874.8 eV, indicated that other nickel-containing compounds were generated during the oxidation and phosphorylation of nickel in the alkaline Ni-P coating. The spectra of phosphorus (Fig. 10b and 10d) show that the peaks at 129.0 eV and 129.8 eV corresponded to P2p3/2 and P2p1/2 of phosphorus in the Ni-P plating, while the other peaks of phosphorus at ~ 132.4 eV were more heterogeneous, with a variety of phosphorus oxides produced during the electroless plating of Ni-P and the oxidation of the surface in air.

It can be seen from the cross-sectional morphology of Ni-P coatings on cobalt and palladium layers that all the coatings were compact and bonded well to the copper substrate. Both the Ni-P coatings obtained from the acidic electroless plating bath were thicker than the coatings obtained from the alkaline electroless plating bath. The Ni-P coating on cobalt layer obtained from acidic electroless plating bath had a thickness of 14.6 µm, which was smaller than the Ni-P coating on palladium layer with a thickness of 15.4 µm. The thickness of Ni-P coating on cobalt layer obtained from alkaline electroless plating bath (6.7 µm) was also lower than that of Ni-P coating on palladium layer under the same reaction conditions and reaction time. Although the smaller thickness of Ni-P coatings on cobalt layer suggested that the activation ability of cobalt layer was a littler weaker than that of palladium layer, cobalt layer could still serve as the activation layer to initiate electroless Ni-P plating.

3.3 Corrosion and tribological performance of Ni-P coating on cobalt and palladium layers

The corrosion resistance of Ni-P coatings on cobalt and palladium layers obtained from acidic and alkaline electroless plating bath were compared by electrochemical methods in 3.5 wt.% NaCl solutions. As shown in Fig. 12a, compared with Ni-P coating on palladium layer with the corrosion potential (E_corr) of − 0.483 V and the corresponding corrosion current density (i_corr) of 0.94 µA·cm^− 2, the E_corr of Ni-P coating on cobalt layer was decreased to − 0.519 V, and its i_corr was increased to 1.63 µA·cm^− 2. The corrosion resistance of Ni-P coating on cobalt layer was a little weaker than that of Ni-P coating on palladium layer. As shown in Fig. 12b, compared with Ni-P coating on palladium layer obtained from alkaline electroless plating bath with the corrosion potential (E_corr) of − 0.568 V and the corresponding corrosion current density (i_corr) of 1.64 µA·cm^− 2, the E_corr of Ni-P coating on cobalt layer was increased to − 0.564 V, and its i_corr was decreased to 1.16 µA·cm^− 2. The above results indicated that Ni-P coating on cobalt and palladium layer exhibited similar corrosion resistance, indicating that the activation ability of cobalt and palladium is comparable.

The dynamic friction coefficients of the Ni-P coatings measured in reciprocating mode are shown in Fig. 13a and 13b. From Fig. 13a, it can be seen from the friction curves of the acidic Ni-P coating activated by cobalt and palladium that the friction coefficients began stable after the 1000 s wear period, and the friction coefficient after stabilization was 0.178. The friction coefficients of the Ni-P coatings obtained from acidic bath were basically the same, indicating that cobalt and palladium had the same activation effect. From Fig. 13b, it can be seen that the friction curves of cobalt and palladium activated Ni-P coatings obtained from alkaline bath. The friction coefficient of cobalt activated Ni-P coatings remained stable throughout the friction period, and the friction coefficient after stabilization was 0.038. While the friction coefficient of palladium activated Ni-P coating increased slowly and steadily throughout the friction period. From Fig. 13c and 13d, it was obvious that the both cobalt and palladium activated Ni-P coating obtained from acidic bath was severely worn, and an obvious wide wear tract could be found. As can be seen from Fig. 13e and 13f, the wear of Ni-P coatings obtained from alkaline bath showed a smaller wear, and the wear tracks were narrow and discontinuous. Although the palladium activated Ni-P coating showed a little slighter were when compared with the cobalt activated Ni-P coating, the cobalt and palladium activated acidic and alkaline Ni-P coating had similar tribological performance.

In this study, a cobalt layer was deposited on a copper substrate using galvanic replacement from a high concentration of sodium iodide solution containing cobalt chloride. The presence of a high concentration of iodide ions reduces the actual potential of the copper substrate, enabling cobalt ions to react with the substrate and form a cobalt layer on the copper surface. The deposition rate of the cobalt layer was observed to increase with increasing CoCl₂ concentration in the NaI solution. Nickel-phosphorus (Ni-P) coatings could be obtained on the cobalt and palladium layers using acidic and alkaline electroless plating baths. The obtained Ni-P coatings exhibited similar morphology, composition, structure, corrosion resistance, and tribological performance. This finding suggests that the cobalt layer deposited on copper by galvanic replacement can serve as a viable alternative to palladium for activating electroless Ni-P plating on copper substrates. The results of this study also highlight the potential use of galvanic replacement to deposit less noble metallic films.

Author Contribution

Guanqun Hu: Investigation, Visualization. Rupeng Li: Investigation, Visualization. Wanda Liao: Investigation, Visualization. Changning Bai: Investigation, Visualization, Writing - review & editing. Xingkai Zhang: Conceptualization, Funding acquisition, Supervision, Writing - original draft. Qiuping Zhao: Supervision, Writing - review & editing. Junyan Zhang: Supervision, Writing - review & editing.

Acknowledgement

This work was supported by National Natural Science Foundation of China [U22A20180]; Industrial Technology Development Program [JCKY2021130B038]; Lanzhou Youth Science and Technology Talent Innovation Project [2023-QN-82].

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Huang H, Xiao Q, Wang J, Yu X, Wang H, Zhang H, Chu P (2017) Black phosphorus: a two-dimensional reductant for in situ nanofabrication. Npj 2d Mater Appl 1(1):20. https://doi.org/10.1038/s41699-017-0022-6

No competing interests reported.

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published 21 Jul, 2024

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Cobalt layer prepared on copper using galvanic replacement as an alternative to palladium for activating electroless Ni-P plating

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Journal Publication

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Abstract

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1. Introduction

2. Materials and methods

2.1. Preparation of cobalt and palladium lays on copper

2.2. Preparation of Ni-P plating on cobalt and palladium layers

2.3. Characterization of the samples

2.4. Electrochemical measurements

2.5. Tribological performance test

3. Results and discussion

3.1. Deposition of cobalt layer on copper by galvanic replacement

3.2 Morphology, composition of Ni-P coatings on cobalt and palladium layers

3.3 Corrosion and tribological performance of Ni-P coating on cobalt and palladium layers

4. Conclusions

Declarations

Author Contribution

Acknowledgement

References

Additional Declarations

Status:

Journal Publication

Version 1