Electroless Cobalt Plating Research Articles

Acceleration Mechanism of Triethanolamine in Electroless Bath for Pure Cobalt Deposition

The utilization of hydrazine as a reducing agent in the electroless cobalt bath is indispensable for the application of pure cobalt film fabrication in ultra-large-scale integration (ULSI). However, the deposition rate using the ordinary coating bath is relatively low. After conducting numerous experiments in this study, we have made a groundbreaking discovery: the deposition rate of electroless plating pure cobalt bath can be significantly increased from less than 1.0 μ·h−1 to more than 5.0 μ·h−1 by adding triethanolamine (TEA) as an accelerator. This remarkable finding greatly enhances the practical value of the electroless cobalt plating bath and enables its application in microholes filling of cobalt interconnect lines below 10 nm. According to the results of linear sweep voltammetry and mixed potential theory, the addition of TEA essentially forms [Co(C6H5O7)(TEA)2]2 2− complex with more feasible reductivity than that of the [Co(C6H5O7)(H2O)]2 2− in the ordinary plating bath and the cobalt center is favorable to be released under the electroless reduction attack to the unstably strong steric hindrance of TEA, which significantly increases the reduction current of Co(II) ions. After the further optimization of pH, temperature and annealing process, not only does resistivity decrease to 12.1 μΩ·cm, but also the surface morphology and crystallinity improve significantly. Therefore, an applicable electroless cobalt plating protocol with a moderate deposition rate is obtained.

Study on cobalt coating on ZTA particles by electroless plating and impact-abrasive wear behavior of ZTAp reinforced iron matrix composite

The electroless cobalt plating modification of ZTAp (Zirconia toughened alumina particle) surface and the impact-abrasive wear behavior of ZTAp and NbCp(Niobium carbide particle) reinforced Fe60 matrix composites (ZTAp-NbCp/Fe60) were investigated. Cobalt was deposited on the ZTAp surface by electroless plating (modified ZTAp) to strengthen the interface bonding between ZTAp and matrix. Both composites reinforced with modified ZTAp and unmodified ZTAp were prepared through vacuum sintering, and their impact-abrasive wear performance testing under different impact energy were carried out with MLD-10 impact-abrasive wear tester. The results showed that the optimal conditions to coat cobalt on the ZTAp surface included of: initial pH value of plating solution was 9, the concentration of NaH2PO2.H2O, and C4H4Na2O6.2H2O was 0.25 mol/L and 0.8 mol/L respectively. The impact-abrasive wear-resistant performance of the modified ZTAp reinforced Fe60 matrix composite was significantly enhanced by more than 35% than the unmodified ZTAp reinforced composite under high energy impact condition. Cobalt and liquid iron had good wettability, and the interface strength significantly increased. During the sintering process, cobalt diffused at the interface, thus leading to a significant binding force between ZTAp and the iron matrix interface. This study suggested that the modified ZTAp could have a better and longer protective effect than unmodified ZTAp on the matrix.

Microwave sintering of TiCN-based cermets prepared from electroless Co-coated (Ti, W, Mo, V)CN powders

In this study, the densification and microstructure evolution of microwave sintered (Ti, W, Mo, V)CN–30 wt%Co cermets, which was prepared from electroless cobalt-coated submicron (Ti, W, Mo, V)CN powders, were investigated. The microwave sintering of mechanical milled powders as well as the conventional sintering of mechanical milled powders and Co-coated (Ti, M)CN powders was conducted as a comparison. Experimental results indicate that a slight densification is observed at sintering temperature of ≤1100 °C followed by a sharp shrinkage at the temperature range of 1200–1350 °C due to the substantial formation of liquid phase at 1200 °C. The 98.5% densification is obtained at 1375 °C. Moreover, the samples sintered at 1375 °C for 10 min have the microstructure with fine and homogeneous grains of about 700 nm. Compared to mechanical milling, electroless cobalt plating suppresses coalescence of neighboring grain at the solid-state sintering stage, thereby inhibiting grain growth. The mechanical properties of samples sintered at different temperatures for varied holding time were also discussed.

Electrochemical properties of NiO/Co–P nanocomposite as anode materials for lithium ion batteries

NiO/Co–P nanocomposite is prepared by an electroless cobalt plating technique. The as-prepared composite is characterized by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. SEM and TEM images reveal that the NiO particles are about 200 nm in size, which are modified by Co–P nanoparticles of about 30 nm. The electrochemical properties as anode materials for lithium ion batteries are examined by cyclic voltammetry (CV) and discharge–charge tests. The results show that, compared with the bare NiO without electroless cobalt plating, NiO/Co–P nanocomposite exhibits a smaller polarization and a better rate capability, which is attributed to the Co–P nanoparticles.

EFFECT OF DIFFERENT PRETREATMENTS TO ELECTROLESS NICKEL OR COBALT PLATING ON HOLLOW MICROSPHERES

Different pretreatment methods for electroless nickel and cobalt plating are demonstrated and compared in the present investigation. The surface morphologies of the nickel or cobalt deposits are investigated by scanning electron microscopy (SEM), and the chemical compositions of the coatings are analyzed by energy-dispersive X-ray spectroscopy (EDX). Method of single-step pretreatment is selected as the optimized method for electroless nickel plating process, while improved two-step sensitization-activation and single-step pretreatment methods can be selected for electroless cobalt plating. It can be found that the content of free Co is much lower compared to electroless Ni plating.

Surface-modified micrometre nickel hollow spheres and their microwave characteristics

To improve the magnetic properties, nickel hollow spheres (NHSs) were surface-modified with a cellular Co structure by a facile electroless cobalt plating route. The microstructures and properties of the modified NHSs were characterized by field emission scanning electron microscopy, x-ray diffraction, Brunauer–Emmett–Teller specific surface area and a vibrating sample magnetometer. Microwave properties were evaluated by mixing NHSs with polyvinyl butyral as coaxial samples. The SEM images showed that the NHSs were coated by the Co cellular films, which not only increased the specific surface area but also enhanced the coercivity and magnetization. Also, the modified NHSs composites presented low RL min values below −30 dB at thicknesses between 1.0 and 2.0 mm, and exhibited a broad absorption bandwidth ΔW at ‘thin’ thickness.

Controllable fabrication of monodisperse Co–B hollow microspheres

Monodisperse cobalt–boron (Co–B) hollow microspheres were fabricated by a facile and controllable method. In this method, cobalt hydroxide (Co(OH) 2) colloids were used as templates, then electroless cobalt plating was carried out on the surface of Co(OH) 2 colloids, finally Co–B hollow microspheres were obtained by adding complexing agent to dissolve the core. The products were characterized by SEM, TEM, XRD and BET, and the results showed that the as-prepared Co–B hollow microspheres have good monodispersity, spherical shape and large BET surface area. The method proposed can be extended to obtain other metal or alloyed hollow microsperes.

Spatially Selective Electroless Deposition of Cobalt on Oxide Surfaces Directed by Microcontact Printing of Dendrimers

We describe a simple method for the fabrication of arbitrary submicrometer patterns of cobalt on a nonconducting surface with wet chemical methods and microcontact printing (μCP). A hydroxyl-terminated dendrimer is transferred from a stamp to the surface. The thickness of the dendrimer layer can be tuned by varying the concentration of the dendrimer ink solution. These dendrimer molecules act as host molecules. The guests, palladium ions, sorb into the layer and act as nucleation centers for electroless cobalt plating. We produced cobalt structures down to several hundred nanometers lateral size and up to several tens of nanometer thickness with high spatial selectivity. The printed dendrimers are cage-like molecules with well-defined chemical groups; hence, they can selectively bind guest molecules (here palladium complexes) when the latter possess chemical groups that favor a host−guest interaction. Printing dendrimers therefore points toward a more general method to create patterns with chemical functionality.

Fabrication of a dense La 0.2Sr 0.8CoO 3−δ/CoO composite membrane by utilizing the electroless cobalt plating technique

Fabrication of dense ceramic electrolyte membranes on porous supports is a key step towards performing gas separations (H 2 or O 2) through the electrochemical pathway. This research develops an approach by making use of the electroless plating method for the preparation of metal-ceramic composite membrane, which is used as the precursor to a metal-oxide composite membrane. As a model of the composite membrane, metallic cobalt is incorporated into a powder-packed layer of La 0.2Sr 0.8CoO 3−δ (LSCO-80), which is pre-coated on a porous MgO disk. When this composite membrane is subjected to sintering at 1000 °C in air, an interpenetrating laminar structure consisting of CoO and LSCO-80 phases is formed according to the cross-section EDX profiles. The oxidation of Co during sintering causes a structure expansion, which exerts a compressive stress on LSCO-80 phase, thus effectively buffering a tensile stress applied by the support. As a result, the composite membrane LSCO-80/CoO can achieve almost gas-tight at ambient temperature.

Surface modification of spherical nickel hydroxide for nickel electrodes

Electroless cobalt plating on spherical nickel hydroxide is tested in order to improve the conductivity of Ni(OH) 2 and the capacity of the electrode. The factors affecting the process of electroless cobalt plating are cobalt solution, temperature and pH, etc. The effects have been examined and the optimum process parameters have been obtained. The nickel hydroxide electrode which is made by nickel hydroxide deposited cobalt has excellent performance, the results showing that electroless cobalt plating on the surface of spherical nickel hydroxide particles is an effective method for modifying electrodes.

溶媒抽出法による無電解コバルトめっき廃液処理

The application of solvent extraction to the treatment of electroless cobalt plating wastewater has been investigated. In the treatment of caustic and ammoniacal alkaline plating wastewaters, TOMAC is favorable to the extraction of cobalt and citrate ion, and the separation from hypophosphite ion and phosphite ion. The extraction of hypophosphite ion from alkaline solutions with TOMAC is suppressed by loading the organic phase with phosphite ion, and the separation efficiency of phosphite ion and hypophosphite ion in the alkaline region is improved using the mixed extractants of TOMAC and phosphine oxides such as CYANEX 923.

The effect of dissolved oxygen on the deposition process in electroless cobalt plating

This paper describes the effect of dissolved oxygen on the deposition process in electroless cobalt solutions. In ammonia alkaline solutions, the deposition rate decreases as the dissolved oxygen content increases. The dissolved oxygen mainly affects the nucleation rate, and affects the growth rate only slightly.

無電解めっき小型磁気ディスクの高密度化

An advanced electroless cobalt plating bath has been developed for increasing the recording density of 3.5″ hard disks, and its properties and magnetic film were analyzedBased on an investigation of many chelate agents of a plating bath, high coercivity and stability was obtained, and it was possible to obtain high S* and output by adding specific salts to the bath, while the addition of zinc resulted in low noise media having fine cristaliteThe use of a plating bath adjusted to an Hc of 1100Oe made it possible to achieve storage capacities of 40MB on 35″ disks

特集／湿式法による磁気記録媒体 無電解Ｃｏ長手記録媒体

特集／湿式法による磁気記録媒体 無電解Ｃｏ長手記録媒体

無電解コバルトめっきにおける低温浴の研究

The deposition characteristics of a low temperature electroless cobalt plating bath and the magnetic properties of the deposited cobalt films have been investigated. The optimum bath composition and operating conditions were found to be; cobalt sulfate 0.1M, sodium hypophosphite 0.2M, sodium pyrophosphate 0.4M, ammonium sulfate 0.5M, bath pH10.5 (adjusted with ammonia), operating temperature 60°C. The magnetic properties of deposited films were improved when they were deposited from low temperature bath. Therefore, this type of bath was suitable to the low temperature bath for magnetic plating. The phosphorous content of Co-P films deposited from these baths was relatively high compared with that from other type of bath due to co-deposition of phosphorous from the pyrophosphate anion in the solution

ピロりん酸ナトリウムを錯化剤とする無電解コバルト‐ニッケル‐りん合金めっき浴

The relation between plating conditions and some properties of films deposited from an electroless cobalt-nickel-phosphorous alloy plating bath with pyrophosphate as a complexing agent was investigated. 1) Preferable plating conditions were obtained in 0.1M of cobalt sulfate+nickel sulfate, 0.4M of sodium pyrophosphate, 0.5M of ammonium sulfate, and 0.2M of sodium hypophosphite at pH 10.5 (adjusted with ammonia) and at 70°C. Under the above conditions, relatively high deposition rate and bath stability were obtained. 2) A film of the composition desired in the ratio of nickel to cobalt was obtained by controlling the ratio of the concentration of nickel to cobalt in the bath. The content of phosphorus in this alloy films varied in the range of 3-4%. 3) Addition of nickel to the electroless cobalt plating film below 20% improved the magnetic property of the film. 4) The magnetic property of the film was affected by the change in its structure parameters such as grain size and anisotropy caused by the addition of nickel.

Electroless Cobalt Deposition from Acid Baths

An acid electroless cobalt plating bath was developed which utilizes di‐methylamine borane (DMAB) as the reducing agent and which provides bright deposits at over 13 μm/hr at 70°C. The bath, slightly modified, is also usable at room temperature for deposition on palladium‐activated nonconductors. Additions of even small quantities of hypophosphite to the DMAB bath resulted in failure to achieve deposition; the effect of hypophosphite additions on the single electrode potentials was determined and the results discussed. Electroless cobalt‐boron deposits were found superior, in some respects, to electroless nickel‐phosphorus for providing protection for steel against corrosive attack. A double layer deposit of electroless nickel plus electroless cobalt topcoat provided more effective protection for steel than either deposit, alone, of the same total thickness. Chromating treatments were found effective for retarding the tendency for tarnishing of cobalt during salt exposure. The magnetic properties of some electroless cobalt‐boron deposits were determined; the coercivity was considerably lower than that of electroless cobalt‐phosphorus deposits.

A New Technique for Investigating the Electrochemical Behavior of Electroless Plating Baths and the Mechanism of Electroless Nickel Plating

The electrochemical potential of electroless nickel and electroless cobalt plating baths can be altered by the addition of a variety of chemical compounds to the baths. At the same time, the metal‐to‐phosphorus ratio in the deposit is altered. This behavior has been studied for a series of baths using typical accelerators including thiourea, glycine, and formate; each of these represents a different type of accelerator characteristic. A Tafel‐like behavior was observed to apply for the deposition of nickel (or cobalt) and also for the deposition of phosphorus. Therefore, given a suitable reference point, the plating rate and metal‐to‐phosphorus ratio can be predicted from the measured potential. A model based on a modified hydride mechanism is proposed for the electroless deposition of nickel‐phosphorus. With the help of this model, the hydrogen evolved during deposition can be quantitatively accounted for.

A New Technique for Investigating the Electrochemical Behaviour of Electroless Plating Baths and the Mechanism of Electroless Nickel Plating

The electrochemical potential of electroless nickel and electroless cobalt plating baths can be altered by the addition of a variety of chemical compounds to the baths. At the same time the metal-t...

アンモニアアルカリ性無電解コバルトメッキ膜の磁性に及ぼすメッキ条件の影響

Effects of pH, temperature, and composition of bath on magnetic properties of deposited films were studied for two sorts of ammoniacal alkaline electroless cobalt plating baths.The results obtained were as follows.(1) The films deposited from ammoniacal alkaline baths had the maximum flux density (Bs) of about 9, 000 gauss, coercive force (Hc) of 200 oersted, and squareness of 0.5-0.7 in general. The variations in the above values of films depending upon plating conditions were found to be less than those of films deposited from caustic alkaline baths reported in the previous paper.(2) In general, citrate bath (A-C type) was stable and gave films of higher squareness. However, the magnetic properties of these deposits greatly depended upon pH and concentration of complexing agents.(3) Tartrate bath (A-T type) was less stable than citrate bath and generally gave films of lower squareness. However, the dependence of coercive force of these films upon the bath conditions such as pH and concentration of complexing agents was little.(4) The difference in the effects of plating conditions of the both baths on the magnetic properties of films was systematically explained by each characteristics of the baths.