Copper Plating Bath Research Articles

Advancements in Analyzing Organic Additives in Electroplating Baths: A Focus on Electrochemical Impedance Spectroscopy (EIS) Coupled with Distribution of Relaxation Times (DRT)

Organic additives play a crucial role in upholding the quality of metallic coatings within commercial electroplating baths. However, their effectiveness diminishes over time due to degradation and drag-out. Continuous monitoring and precise dosing are imperative to uphold optimal concentration levels, preserving both technical integrity and aesthetic appeal. Traditional chromatographic techniques are impractical for routine industrial analysis due to the complex formulation and synergistic effects of various additives. Electrochemical methods, such as the Hull cell test and Cyclic Voltammetric Stripping (CVS) measurements, are commonly employed to adjust additive concentrations based on their impact on the electrodeposition process. Although widely utilized, the Hull cell test relies on trial and error and operator experience, providing only qualitative assessments. CVS, which measures changes in the rate of copper deposition to reflect additive concentration, may not be universally suitable for all electroplating baths due to their varying complexities.Prior Electrochemical Impedance Spectroscopy (EIS) investigations on copper plating baths have qualitatively linked impedance changes with aging [1]. Our objective was to quantify additives using EIS. To achieve this, experimental data were analyzed in terms of resistive and capacitive components to calculate the distribution of relaxation times (DRT) via Lasso regression [2]. The resulting data were subjected to multivariate analysis to address this challenge.The promising outcomes [3] render this method highly appealing in both industrial and academic contexts. Its application in the galvanic field is particularly advantageous for gaining insights into the function of individual additives, their interactions, and the aging process of plating baths.Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2023 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile".

Electrochemical spectroscopic analysis of additives in copper plating baths by DRT and multivariate approach

The concentration of additives of a copper electroplating bath with a complex matrix are quantified using electrochemical impedance spectroscopy (EIS). The Experimental data were processed to calculate the distribution of relaxation times (DRT) using Lasso regression and the results were fed to a multivariate analysis to overcome this challenge. The complex nature of electroplating bath matrices, often containing various organic additives, poses challenges for traditional analytical methods. The proposed approach enables the direct measurement of additive behavior within the bath, regardless their chemical composition. This method offers distinct advantages over conventional techniques, such as chromatography, Hull cell test and cyclic voltametric stripping (CVS).

Analysis of Quadrol Additives in Pyrophosphate Copper-Plating Bath by Use of Boron-Doped Diamond Electrode

Analysis of Quadrol Additives in Pyrophosphate Copper-Plating Bath by Use of Boron-Doped Diamond Electrode

Hybrid Membrane Technology for Acid Recovery from Wastewater in Coated Steel Wire Production: A Pilot Scale Study.

In the present study, the problem of sulfuric acid recycling from spent copper plating solution was solved using a hybrid membrane technology, including diffusion dialysis and electrodialysis. A real solution from the production of copper-coated steel wire, containing 1.45 mol/L of sulfuric acid, 0.67 mol/L of ferrous sulfate and 0.176 mol/L of copper sulfate, was processed. Diffusion dialysis with anion-exchange membranes was used to separate sulfuric acid and salts of heavy metals. Then, purified dilute sulfuric acid was concentrated by electrodialysis. The energy consumption for sulfuric acid electrodialysis concentration at a current density of 400 A/m2 was 162 W·h/mol, with a current efficiency of 16%. After processing according to the hybrid membrane scheme, the solution contained 1.13 mol/L sulfuric acid, 0.077 mol/L ferrous sulfate and 0.022 mol/L copper sulfate. According to established requirements, the solution of a copper plating bath had to contain from 0.75 to 1.25 M sulfuric acid, 0.16-0.18 M of copper sulfate and ferrous sulfate not more than 0.15 M. The resulting acid solution with a small amount of ferrous sulfate and copper sulfate could be used to prepare a copper plating bath solution.

Recent Advances in Electrodeposition of Copper Ultrathin Films on Cobalt Substrate

As the miniaturization trend in integrated circuits fabrication continues, alternative liner materials in copper interconnects have been actively explored. Cobalt has been widely investigated and employed due to its low resistance at nanoscales, integration compatibility, as well as benefit of improving copper electromigration resistance. However, direct electrodeposition of copper onto cobalt remains less explored due to the stability issue of cobalt in acidic copper damascene process. Subsequent processes of copper seeding and copper electroplating face increasing technical difficulties when widths and aspect ratios of electro-fill features become more challenging.Direct electrodeposition of copper on cobalt has been explored in acidic and alkaline chemistries, both of which were formulated by MacDermid Alpha Semiconductor Solutions. In both cases, well-adherent, nearly-pinhole-free, and ultrathin Cu has been successfully electrodeposited onto cobalt substrate with less than 10% cobalt loss. SEM images in Figure 1 imply uniform dispersion of copper on cobalt. XRF and ICP analysis confirm that the thinnest copper films deposited could be no thicker than 2 nm. Corrosion test in acidic copper plating bath shows that an ultrathin copper layer of thickness less than 2 nm can effectively suppress cobalt dissolution by a factor of three in comparison to non-coated bare cobalt.This work could pave the avenue towards direct copper electrodeposition onto cobalt liner in semiconductor manufacturing for advanced technology nodes. Figure 1. Top-down SEM images. (left) As-received cobalt substrate; (center) Cu of 2 nm nominal thickness electrodeposited on cobalt from an acidic solution; (right) Cu of 2 nm nominal thickness electrodeposited on cobalt from an alkaline solution. All three images have the same scale and scale bars are 200 nm. Figure 1

Direct electroless plating of conductive thermoplastics for selective metallization of 3D printed parts

Electroless plating is a promising approach for metallizing plastic 3D printed parts, but current approaches rely on surface activation with expensive precious metal catalysts such as palladium. In this work, we demonstrate conductive composite filaments loaded with metal or other conductive particulate can be electrolessly plated directly, without prior activation, with exposed particles serving as nucleation sites. Several commercially available filaments based on different particulate loading were plated, with both carbon black and copper particulate shown to nucleate in an electroless copper plating bath. Flash ablation metallization, the use of a flash of high energy white light to ablate the polymer on the surface and expose a higher density of metal particulate, was also shown to accelerate the plating process. Selective plating was then achieved through use of a dual extruder 3D printer to define conductive composite regions for plating on a non-conducting thermoplastic. Trace resistances were reduced by as much as five orders of magnitude after copper plating. A toroidal inductor was printed and shown to drop in resistance from 24 kΩ before to 2.3 Ω after plating, with post-plating inductance and quality factor 315 nH and 10.3 respectively. A 555 timer circuit demonstrator was also plated.

INVESTIGATION OF ENHANCING THE PERFORMANCE AND DEPOSITION CHARACTERISTICS OF COPPER (II) METHANE SULPHONATE SALT COMPLEXED WITH DMANNITOL BATH

The performance of the eco-friendly D-Mannitol electroless copper plating bath with additives has been investigated. D-Mannitol produces a lower plating rate which has been improved using exaltants viz., polyethylene glycol 600, oxalic acid and malonic acid. The performance of the bath shows improvement gravimetrically and by polarization studies. The surface morphology studies are also interpreted.

Effects of Plasma Treatment as a Surface Preparation Step on Copper Plating

The continuous electrolytic copper plating process traditionally includes degreasing and acid baths before copper plating baths. These baths add difficult-to-control parameters to the process. Besides they contain various alkaline chemicals and acids that are harmful to the environment. The plasma surface treatment is a controllable alternative surface cleaning method which is used in various fields. Also it can be used for surface activation to improve plating performance. Another important aspect of the plasma process is its environmental friendliness. It has a high potential to make plating preparation stages environmentally friendly and efficient. In this study a plasma surface treatment system is attached on a traditional copper plating line which is used for cold rolled low carbon steel sheets. It was determined that plasma surface treatment had a positive effect on the quality of copper plating.

Detection of Organic Additives in Copper Plating Bath Using Voltammetric Methods That Involve a Screen-printed Nano-Au Electrode

Three electrochemical methods used to detect organic additives, A, B and C, in acidic plating baths. Cyclic voltammetric stripping (CVS) is used in industry to detect the concentration of organic additives indirectly by measuring the effect of commercial organic additives on the rate of copper deposition. This study directly determines the concentration of organic additives on a screen-printed nano-Au electrode at high potential using three different electrochemical methods: linear scanning voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The results show that the response currents for the three electrochemical methods exhibit a linear relationship with the concentration of organic additives. The nano-Au electrode is the most sensitive device for the detection of organic additive B using LSV.

Electrochemical sensor based on 1,8-dihydroxyanthraquinone adsorbed on a glassy carbon electrode for the detection of [Cu(CN)3](aq)2− in alkaline cyanide copper plating baths waste

This work reports the fabrication of a novel electrochemical sensor for the detection of the complex ion [ Cu ( CN ) 3 ] ( aq ) 2− , one of the main components of the effluents from cyanide alkaline copper plating baths. This sensor was prepared by using a surface modified glassy carbon (GC) electrode with 1,8-dihydroxyantroquinone (1,8-DHAQ). It was characterized by electrochemical impedance, Raman spectroscopy and UV–Visible spectroscopy. The electrochemical detection of [ Cu ( CN ) 3 ] ( aq ) 2− was performed by differential pulse voltammetry. The 1,8-DHAQ/GC electrochemical sensor exhibits good reproducibility and a linear range of 5.50 × 10 −7 –3.81 × 10 −6 mol L −1 , with a detection limit (LOD) of 1.20 × 10 −6 mol L −1 , quantification limit (LOQ) of 3.97 × 10 −6 mol L −1 , and robustness to interfering Cl − , NO 3 − , SO 4 2− y CO 3 2− ions. Finally, a DFT approach suggests an almost parallel orientation of the bis(1,8-dihydroxyanthraquinone) over a graphene domain of the glassy carbon surface, as well as the noncovalent nature of the interactions involved. Development of the 1,8-DHAQ/GC sensor for the electrochemical detection of the copper cyanide complex [Cu(CN) 3 ] 2− evaluated by RAMAN spectroscopy and Differential Pulse Voltammetry. • Copper cyanide complexes are pollutants, their control is of vital importance. • The GC surface was modified with 1,8-DHAQ by spontaneous adsorption. • Electrochemical determination of [Cu(CN) 3 ] (aq) 2− by Differential Pulse Voltammetry. • Decrease in the electrochemical signal of 1,8-DHAQ by [Cu(CN) 3 ] (aq) 2− interaction. • The 1,8-DHAQ/GC sensor allows [Cu(CN) 3 ] (aq) 2− detection at low concentrations.

Effects of accelerator in a copper plating bath on interfacial microstructure and mechanical properties of SAC305/Cu solder joints

An accelerator, 3-(2-benzthiazolylthio)-1-propanesulfonsaure (ZPS), was used and formulated with a suppressor (polyethylene glycol, PEG) and chloride ions (Cl−) in electroplated Cu plating solution containing electrolytes (Cu sulfate and sulfuric acid) to prepare the Cu films. The preferred orientation of Cu film transformed from (200) to (220) with the addition of ZPS in plating solution containing (PEG and Cl−). The addition of ZPS in basic plating solution promoted the growth of Cu grains and increased the surface roughness of Cu film. The root mean square roughness of Cu film increased from 206.9 to 230.8 nm with increasing ZPS concentration. The impurity elements of electroplated Cu film were O, C, Cl, and S elements. With the further increase in ZPS, the number of void within Cu3Sn layer obviously reduced, improving the stability of the electroplated Cu solder joints subjected to thermal aging.

Cyclic Voltammetric Stripping (CVS) for the measurement of additives in electro Copper plating baths

Cyclic Voltammetric Stripping (CVS) for the measurement of additives in electro Copper plating baths

Novel Method for Detection of Organic Additives in Copper Plating Baths

Appropriate organic additives, including accelerators, inhibitors and leveling additives, are essential in the copper plating process of printed circuit boards to achieve defect-free filling effect. The fluctuation of organic additives would cause product defects and reduce manufacturing efficiency resulting in increasing additional cost. Therefore, it is very important to control the quality of electroplating. Development of sensors that detect the concentration of organic additives is indispensable. At present, the concentration of organic additives can only be measured by offline sampling in industry. An indirect cyclic voltammetry stripping (CVS) are often used to detect the concentration of organic additives based on the stripping peak of copper. This study attempts to measure the organic additives directly at high applied potential by using three different electrochemical methods, including linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The results show that the response current values of the three electrochemical methods have a good linear relationship with the concentration of the organic additives. The sensitivity of the electrode by LSV is the highest. There are two proper potentials to detect the additives by SWV. However, the detection potentials of the three organic additives are quite close. If these organic additives should be accurately identified separately, the electrode would need to be further modified.

Electroless Deposition on Three Substrates: Brass Washers, Cicada Exoskeletons, and Beetles

This laboratory experiment showcases electroless deposition, an autocatalytic reduction process performed in aqueous solution containing a metal ion in the presence of a reducing agent yielding a coherent metal film. One set of experiments has been performed by second-semester general chemistry students in a 3 h lab session. After preparing an electroless nickel plating bath, they first plate a brass washer with nickel for 10 min at 85 °C. Using weight gain data for their brass washer along with its surface area, the thickness of the nickel coating is determined. The same electroless nickel plating bath is then used to plate a pretreated cicada exoskeleton with nickel. The three-step pretreatment procedure deposits Pd(s) nanoparticles on a nonconducting exoskeleton made of chitin, transforming it into a conducting substrate. A second set of experiments has been performed by upper-class chemistry majors. They (1) explore the reproducibility in weight gain when plating brass washers with nickel for 10, 20, 30, and 40 min time intervals, (2) plate beetles with nickel, and (3) plate cicada exoskeletons with copper using an electroless copper plating bath recipe they find in the literature. Weight gain data and photos of the plated cicada exoskeletons and beetles accompany this article. The nickel-plated brass washers and cicada exoskeletons were examined with XRF spectrometry. This analysis demonstrates that the nickel coating is not pure nickel but rather an alloy containing phosphorus.

New Cyanide-Free Alkaline Electrolyte for the Electrodeposition of Cu-Zn Alloys Using Glutamate as Complexing Agent

Glutamate is a potential replacement of cyanide in alkaline electrolytes due to its capability to form complexes with bivalent metal ions. Since promising results were achieved with copper and zinc plating baths, and the use of cyanide implies environmental and safety disadvantages, it was decided to study the possibility of codepositing these two metals using sodium glutamate as complexing agent. Electrochemical processes involved in electrodeposition of copper and zinc individually as well as in solutions containing both metal ions were studied utilising cyclic voltammetry. Cu-Zn deposits obtained at different current densities from solutions of different composition were characterized by SEM and EDS. It was concluded that the system has a normal behavior, according to Brenner's classification, since the more noble metal is deposited preferentially. The plating bath containing 30% molar of Cu2+ was selected to continue the studies of the system.

Practical Research on Electroless Copper Plating Technology on Ceramic Surface

Deposited electroless copper layer on ceramic matrix by using formaldehyde reduction copper plating system to complete DPC seed layer. Used orthogonal experiment, single factor analysis and other methods to optimize solution parameters, the optimum parameters of electroless copper plating bath are as follows: Cu SO 4 8g/L, C 4 H 4 O 6 KNa·4H 2 O 40g/L, HCHO 10g/L, temperature 35 ℃and time 30min respectively. Adopted scotch tape, microstructure, composition analysis, temperature cycling test and a variety of other test methods to comprehensively analyze the performance of the electroless copper layer, it turned out that electroless copper has fine electrical and mechanical performance.

Influence of Temperature on Peculiarities of Electroless Copper Deposition

The industrial electroless copper plating solutions containing formaldehyde as reducing agent are known from the middle of the last century and are widespread in the practice up to now. They are widely used in electronics for deposition of metallic copper layers on semiconductors or dielectrics (silicon wafers, resins etc.). Since such kind solutions are alkaline (formaldehyde is strong enough reducing agent for Cu(II) only in alkaline solutions), ligands are needed for preventimg of formation of Cu(OH)2 precipitate and binding Cu(II) into complexes Ethylenediaminetetraacetic acid (EDTA) is one of the most widely used ligand in alkaline electroless copper plating baths due to its perfect chelating properties. The possible solution equilibria in alkaline Cu(II)-EDTA-formaldehyde solutions are discussed in details. The data on use of EDTA in electroless copper plating as a Cu(II) ligand are enough wide-ranging, but, it is worth noting that practically all data are obtained at room or higher temperature. Therefore in this work copper coatings were deposited from alkaline formaldehyde-containing solutions, using EDTA as Cu(II) ligand at temperatures, mainly lower than room temperature. The experiments were carried out in electroless plating solutions at pH 12.0 - 13.0 and 5 - 30 °C temperature during 0.5 and 1h (Fig. 1). The thickness of the compact copper coatings obtained under optimal operating conditions in 1 h can reach ca. 4 μm, depending on the pH and temperature. The maximum values of plating rate are reaching at pH 12.5 at all investigated temperatures. The real surface areas (R f) of deposited copper coatings vary widely, i. e. from ca. 3.1 up to 39.3. The maximum R f values were obtained at pH 12.0 for investigated temperatures. The anodic formaldehyde oxidation measurements were carried out in formaldehyde solution at pH 12.5. It was found, that the rate of formaldehyde anodic oxidation depends on conditions of the formation of copper coatings – the highest rate of HCHO oxidation was determined on the surface’s electrolessly obtained at 5 °C and pH 13.0. Acknowledgment This research was funded by a Grant (No. LAT-12/2016) from the Research Council of Lithuania.

Water reclamation and chemicals recovery from a novel cyanide-free copper plating bath using electrodialysis membrane process

One of the industrial concerns is to change procedures into sustainable and cleaner processes. In electroplating, researches have been developed to replace toxic materials for safer alternatives. Cyanide salts are toxic compounds used as complexing agents in alkaline baths. This work focused in a cyanide-free copper alkaline bath developed for copper coating onto zinc alloys. Electrodialysis was evaluated to obtain a concentrated solution from a model rinsing water and simultaneously to treat the effluent for further reuse. Membrane properties after electrodialysis were analyzed, before and after cleaning procedures. Deposition tests were performed using electrolytes containing the recycled inputs and the coatings were analyzed. As results, a solution 5 to 6 times more concentrated than the initial one was obtained. The average demineralization was 90% and the percent extraction of ions was higher than 80%. Interactions between the organic acid and the exchange groups may affect membrane properties. Nevertheless, FTIR analyses and the applied cleaning procedures showed that bonds between phosphorus and quaternary amine may be reversible. Both cleaning procedures presented similar performance and partially restored the membrane properties. The concentrate could be added to the copper bath to compensate eventual drag-out losses without affecting the quality of the coatings.

A Thermodynamic Study of Adsorption of Benzyl Viologen and Polyethylene Glycol and Their Displacement by 3-Mercapto-1-Propanesulfonate during Copper Electrodeposition

In copper-plating baths for filling of submicron features, a combination of additives regulates the distribution of deposition rate, and in the proper concentrations produces superconformal filling. The present study is built on the competitive adsorption model of superconformal filling in which an adsorbed suppressor, in this instance benzyl viologen or polyethylene glycol, is displaced from the surface by the accelerant 3-mercapto-1-propane sulfonic acid (MPS) during copper electrodeposition. The change in deposition current after progressive additions of suppressor or accelerant was used to determine the surface coverage of each additive as a function of its concentration in solution and of temperature. The data were fitted to the Langmuir isotherm, and the free energy and enthalpy of adsorption or displacement were determined. It was shown that adsorption of PEG or BV is a spontaneous exothermic process, and the displacement of PEG or BV by MPS is a spontaneous endothermic process. Although the suppressors form stronger bonds with the surface, the accelerant displaces them due to the resulting increase in surface-excess entropy.

Electrochemical Analysis of Aged Copper Plating Bath in Wafer Level Packaging (Part 1)

Abstract Copper electroplating processes are widely used in semiconductor manufacturing, particularly during the packaging stage [1]. Copper deposition is used to build various structures including TSV, RDL, Pillars, and Micro and Mega Bumps. Those processes utilize plating solutions that contain inorganic components and organic additives [2]. During the electroplating process, the additives can partially transform into compounds that are so-called breakdown products. The presence of such breakdown products can interfere with the electrochemical analysis of organic additives. This article presents results of plating tests that show the influence of freshly produced breakdown products on analysis of organic additives. In addition, several options to eliminate this effect are presented.