Preparation of direct plated copper ceramic spreader using electroless copper as seed layer

A new activation process for electroless copper plating has been developed, which does not require the use of a palladium-based activation bath as typically employed in the plating industry. The activation bath of the new process described herein is entirely free of palladium and is based on colloidal metallic copper particles, which are nanoscopic in size. This bath can also be readily analysed and controlled. The new copper-based activation bath can be operated in such a way that colloid agglomeration and colloid oxidation are efficiently and effectively suppressed, while electroless copper plating quality and electroless copper bath stability is maintained. In addition, the new activation bath can be operated for several weeks without any detectable deterioration in electroless copper plating performance. Furthermore, acrylonitrile butadiene styrene (ABS) and FR4 coupons treated with the new copper-based colloidal activation bath can be vigorously rinsed with water for several minutes prior to immersion in the electroless copper bath without loss of plating quality. The new activation process performs comparably to an established palladium-based process operated at typical vertical equipment immersion times. Even though the electroless copper plating initiation is somewhat delayed for the new copper-based activation process, the final electroless copper deposit thicknesses are the same for both the new process and the palladium-based reference process. The adhesion of the electroless copper deposit obtained with the copper-based activation process is also similar to that obtained with the palladium-based reference activation system. Moreover, the electroless copper coverage performance of the new copper-based activation process, as determined by the backlight test, is comparable to that of the palladium-based reference process.

Surface modification is an effective method to improve the electrochemical property of hydrogen storage alloy. In order to investigate the influence of process factors of electroless copper (Cu) plating for AB5-type hydrogen storage alloy on Cu coating mass, a novel modeling approach, support vector regression (SVR) combined with particle swarm optimization (PSO), was proposed to construct a mathematical model for prediction of the mass changes of Cu coating over the AB5 hydrogen storage alloy surface based on three factors, including temperature, pH value and Ni2+ concentration. The modeling accuracy and reliability of the created SVR model are validated through leave-one-out cross validation (LOOCV), and compared with those of a second-order polynomial model. The results show that the predicted errors by SVR-LOOCV models are all smaller than those achieved by the second-order polynomial model. The SVR model is further applied to predict the process parameters for the maximum Cu coating mass. These studies suggest that SVR can be used as an effective methodology to assist the design of experiment, and is helpful to precisely control the coating mass via fine adjustment of the process parameters. Key words: Surface modification, electroless copper plating, hydrogen storage alloy, support vector regression, modeling and prediction.

Electroless (ELS) copper plating process has been commonly used for printed circuit board (PCB) metallization. The traditional ELS copper plating process uses tin/palladium colloid or complexed palladium ion as catalysts for ELS copper deposition. But the price of palladium catalyst is much higher than that of gold. Herein, we use complexed copper(II) ion to replace the palladium catalyst in order to greatly reduce the process cost but maintain the performance and the reliability of the complexed copper(II) ion as good as palladium. The synthesis process of the complexed copper ion is simple and its cost, which compared with palladium, is cheap. Especially, they have no oxidation issue because they are not metallic copper nanoparticles but copper(II) ions. Before ELS copper plating, the grafted copper(II) ion that is chemically adsorbed onto the substrate surface is reduced to copper atom, so they can catalyze ELS copper deposition. In this work, we optimize the experimental parameters such as operating temperature, reaction time, copper ion concentration and the pH of the plating solution. After ELS plating process, the backlight test of through holes (THs) of a PCB and the morphology of the ELS copper deposited onto the sidewalls of the THs are evaluated by optical microscope (OM) and scanning electron microscope (SEM), respectively. The thermal reliability of the ELS copper deposition catalyzed by the grafted copper catalyst was examined after copper electroplating using thermal shock in a tin bath at 288℃ for ten seconds and repeated it for 5 times. Results show that it can pass the thermal shock test. Therefore, the application of complexed copper(II) ion as the catalyst of ELS copper plating is expected to replace the expensive palladium for PCB fabrication.

The copper-coated polyester fabric can be used to prepare electromagnetic shielding materials. At present, electroless copper plating mainly using formaldehyde as the reducing agent. But the stability of the bath is poor and it is also volatile and toxic. Using hypophosphite as reducing agent has more advantages for its stability and the plating process does not release any toxic gases. In this paper, The copper-coated polyester fabric was prepared by electroless plating with the sodium hypophosphite as reducing agent. The roughening condition before plating and the deposition process were optimized through orthogonal test. The surface resistances of conductive polyester fabrics, the deposition rate and the coating adhesion were investigated respectively. The optimum roughening conditions obtained are as following: sodium hydroxide concentration of 250g/L; temperature 70 D; time 15min, and the lightweight rate of the plating layer is 0.43% under the experimental conditions. The optimum conditions of electroless copper plating using sodium hypophosphite as reducing agent are: copper sulfate 8g/L; nickel sulfate 1.0g/L; sodium hypophosphite 35g/L; citric acid 20g/L; boric acid 30g/L; pH 9.0; temperature 75D. With these conditions, the deposition rate reaches 1.274g/(m2·min) and the uniform and compact copper layer with excellent electro-conductivity was obtained.

Selective electroless copper plating micro-coil assisted by 248 nm excimer laser

Although electroless copper deposition has been widely used in the electronic industry, the selection of the bath solutions relies still on some empirical rules. This paper provides a further exploration of the bath compositions for electroless copper plating. It was found that the formation of Cu2O in electroless copper plating is associated with the presence of Cu(OH)2 in the bath. A chemical equilibrium calculation was thus made for the avoidance of Cu(OH)2 in an electroless copper bath. Sodium thiosulfate was found to be an effective stabilizer for electroless copper plating. The plating was further optimized based on a statistical design of sorts, namely, Taguchi's approach. Effects of individual components on the plating rate were discussed.

Advanced Ag nanoparticles for the catalyzation of glyoxylic acid oxidation in through-holes electroless copper metallization

The electroless copper plating of textiles, which have been previously printed with a catalyst, is a promising method to selectively metallise them to produce high-reliability e-textiles, sensors and wearable electronics with wide-ranging applications in high-value sectors such as healthcare, sport, and the military. In this study, polyester textiles were ink-jet printed using differing numbers of printing cycles and printing directions with a functionalised copper–silver nanoparticle catalyst, followed by electroless copper plating. The catalyst was characterised using Transmission Electron Microscopy (TEM) and Ultraviolet/Visible (UV/Vis) spectroscopy. The electroless copper coatings were characterised by copper mass gain, visual appearance and electrical resistance in addition to their morphology and the plating coverage of the fibres using Scanning Electron Microscopy (SEM). Stiffness, laundering durability and colour fastness of the textiles were also analysed using a stiffness tester and Launder Ometer, respectively. The results indicated that in order to provide a metallised pattern with the desired conductivity, stiffness and laundering durability for e-textiles, the printing design, printing direction and the number of printing cycles of the catalyst should be carefully optimised considering the textile’s structure. Achieving a highly conductive complete copper coating, together with an almost identical and sufficiently low stiffness on both sides of the textile can be considered as useful indicators to judge the suitability of the process.

Effects of simplified pretreatment process on the morphology of W–Cu composite powder prepared by electroless plating and its sintering characterization

The work is devoted to the study of the effect of various compounds on the stability of electroless copper plating solution containing Trilon B. as a chelating agent. The stability of electroless copper plating solutions was estimated by the accelerated method as the time before the start of intensive decomposition of the solution after the introduction of 0.15 ml of colloidal palladium activator solution heated to 75 °C in 250 ml. As stabilizers, both known, currently used, and newly selected compounds were investigated. Sulfur- and/or nitrogen-containing organic and inorganic compounds such as: sodium diethyldithiocarbamate, 2,2’–dipyridyl, thiosemicarbazide, potassium hexacyanoferrate (III), potassium hexacyanoferrate (II), thiourea, thioglycolic acid, dimethylglyoxime, potassium rhodanide in concentrations in the range of 1 - 50 μmol/l were among the first studied. It is shown that when the stabilizers are contained in the solution at the optimal concentrations set (for each compound), solutions containing sodium diethyldithiocarbamate, thioglycolic acid, thiosemicarbazide, thiourea (in descending order of stabilizing action), i.e. compounds containing a sulfur-carbon bond, have the greatest stability. With this in mind, other sulfur-containing compounds, including heterocyclic ones, were selected and studied as stabilizers: α-lipoic acid, thiamine chloride, methyl orange, nitroso-p-salt, methylene blue and SPADNS (sodium salt of 2-(psulfophenylazo)-1,8- dihydroxynaphthalene-3,6- disulfonic acids). In addition, nitrogen-containing compounds that were not previously used in electroless copper plating solutions as stabilizers were also studied: nicotine, pyridoxine, Janus Green B (8-(4-dimethylaminophenyl) diazenyl-N, N-diethyl-10-phenylphenazine-10-ium-2-amine chloride), nigrosine, however. Solutions of electroless copper plating in the presence of these compounds did not show high stability. It has been established that the most effective, comparable in effect to the stabilizers currently used, are α-lipoic acid and thiamine chloride. The advantages of the latter are their availability and low toxicity. For citation: Solopchuk M.S., Grigoryan N.S., Asnis N.A., Vagramyan T.A., Shmelkova P.O., Bardina O.I. Stabilizers of solutions of chemical copper plating. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 3. P. 100-107. DOI: 10.6060/ivkkt.20236603.6708.

A facile process to fabricate metal coating on PET sheet: Preparation of highly active polymer brush/Ag particle and its application in electroless copper plating

The addition of bis(3-sulphopropyl) disulphide in Cu electroless plating results in Cu superfilling. However, the deposition rate of superfilling copper plating is decreased, which hinders its application for filling Cu into via holes of ultralarge scale integrations. In the present study, the effect of triethanolamine (TEA) on the deposition rate of electroless copper plating was investigated. The deposition rates of electroless plated copper both in traditional and superfilling copper plating were accelerated with an addition of TEA, which was attributed to a decrease in reaction activation energy of a dominant reduction reaction. X-ray diffractometry and atomic force microscopy measurements indicated that with an addition of TEA, the peak intensity ratio /(111)//(200) of electroless plated Cu film was increased and the average surface roughness was decreased.

Improvement of thermal-hydraulic performance of plate heat exchanger by electroless nickel, copper and silver plating

Hydrolysis modification of nitrile groups on acrylonitrile butadiene styrene (ABS) plate surfaces into carboxylic acid groups was investigated to find a new recipe for electroless copper plating of ABS plate surfaces without etching reactions using chromic acid and also without a palladium catalyst. Hydrolysis modification of nitrile groups was successfully conducted in an aqueous sodium hydroxide (NaOH) solution (70 wt %) at 80°C for more than 72 h, and nitrile groups were modified into carboxylic acid groups. The hydrolysis modification was accelerated by the addition of dioxane as a supplement to the aqueous NaOH solution. The modification, when an aqueous mixture solution of NaOH (35 wt %) and dioxane (10 wt %) was used as a reagent, was accomplished at 65°C in 30 min. The hydrolyzed ABS plate surfaces were successfully metalized by electroless copper plating. A silver catalyst, instead of a palladium catalyst, was usable in the electroless copper‐plating process. Adhesion between the deposited copper metal and ABS plate surface was perfect for the Scotch tape test. Consequently, we propose a new recipe for an electroless copper‐plating process without an etching process using chromic acid and without a palladium catalyst. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Electroless copper plating is a vital technique for depositing uniform and conductive copper layers, particularly for fabricating copper-coated polymer microspheres used in anisotropic conductive adhesives. However, achieving high-quality coatings on polymer microspheres remains challenging due to their inherent catalytic inertness and the lack of reliable evaluation metrics. Herein, copper nanoparticles are utilized as catalytic seeds for electroless copper plating on styrene-divinylbenzene (PSDVB) microspheres via a prereduction step using ammonia borane. After tailoring the bath composition and processing conditions, the optimized PSDVB@Cu microspheres with a dense 0.047 μm thick copper layer, 50.60 wt % copper content, and a low resistivity of 6.04 × 10-6 Ω·m can be obtained. Crucially, two novel quantitative indicators, named oxidation degree and densification degree, are introduced to comprehensively assess coating quality. A clear correlation is established among the densification degree, oxidation degree, and electrical performance. Specifically, the microspheres become conductive only when the densification degree exceeds 0.2 and the oxidation degree falls below 3.0. With a densification degree above 0.4 and an oxidation degree below 1.4, the resistivity stabilizes near 10-6 Ω·m. Beyond elucidating a tunable electroless copper plating process, this work provides a quantitative framework for coating assessment, paving the way for the standardized fabrication of high-performance copper-coated microspheres in advanced electronics.