Electrochemical Formation and Accumulation of Cu(I) in Copper Sulfate Electroplating Solution

Abstract

The formation and accumulation of Cu(I) in copper sulfate electroplating solutions are discussed. Using electrolysis, the accumulation of Cu(I) in the plating solutions was also confirmed. The accumulation rate and amount depend on the current density and electrolysis time and the dissolved gases. Cu(I) is present in the aqueous solution as a complex with polyethylene glycol and is gradually consumed by oxidation or disproportionation reactions. In the plating solutions of nanobubbled water, the formation and accumulation rate of Cu(I) was different depending on the dissolved gas species. Our results indicate the possibility of controlling the Cu (I) With the increase in the density of printed circuit boards and the development of through-silicon via (TSV) plating technology, the management of the plating solution during the manufacturing process is crucial to maintain the quality of the product. In copper sulfate electroplating, monovalent copper ions (cuprous ion: Cu(I)) have been identified as one of the main causes of low quality plating such as high roughness and a dull finish on the copper plated surface. On the other hand, it has also been suggested that the formation of stable Cu(I)-complexes is a key process in bottom-up via filling. There have been some studies concerning the behavior and roles of Cu(I) in the plating process; 1-6 however, the analysis of the aqueous solutions used in the plating process has been insufficient. Therefore, accurate measurement of the Cu(I) concentrations in the plating process is required. However, it is challenging to measure and monitor the Cu(I) concentration in the electroplating process because of the instability of Cu(I) in solution and its consequent rapid oxidation. In fact, although there is a large amount of Cu(I) in the plating solution used on electroplating production lines, there is insufficient knowledge concerning the structures of Cu(I)-containing compounds in the plating solutions.The disodium salt of bathocuproinedisulfonic acid (BCS) can be used to quantify the Cu(I) concentration in aqueous solutions. [7][8][9] We have succeeded in optically analyzing the Cu(I) contained in plating solutions by monitoring the absorption of a chelate of Cu(I) with BCS.10-13 Here, we report the formation and accumulation of Cu(I) in copper sulfate electroplating solutions and discuss the relationship of the Cu(I) activity to the electrolysis conditions, such as current density, time, and dissolved gases, based on experiment. These results are important for the control of processing factors such as the concentrations of the Cu(I)-containing compounds in the plating solutions in industrial plating lines. ExperimentalBCS was used for the stable detection of Cu(I) ion in aqueous solution, and its chemical formula is shown in Figure 1. Two molecules of BCS coordinate to one Cu(I) ion to form 1:2 complexes that absorbs visible light at wavelengths between 400 and 550 nm. However, this absorption peak does not appear in the reaction with Cu(II). Therefore, the Cu(I) concent...

Evaluation of Copper Sulfate Electroplating Solution and Film Using a New Method of Fluorescence Measurement

“…The degradation of a plating solution is known to accelerate when excessive current is applied while bubbling nitrogen with a copper plate as the anode and a platinum-copper plate as the cathode. 6,7 In the current experiments, the optimum current for forming a plating film was 0.2 A. If 1.0 A is used, the current is five times higher.…”

“…In previous studies, the current authors successfully developed a simple method for determining the concentration of monovalent copper (Cu(I)) in copper sulfate plating baths via a color reaction. [6][7][8][9] The Cu(I) concentration is determined from the absorbance of a dye (bathocuproinedisulfonic acid, disodium salt (BCS)) that selectively reacts with Cu(I) and a plating sample. Measuring Cu(I) allows evaluation of the degradation of the plating solution and prediction of the increase in surface roughness of the plating film to be produced.…”

Salinity-Induced Changes in Heavy Metal Behavior and Mobility in Semi-Arid Coastal Aquifers: A Comprehensive Review

“…It has transitional properties, which mainly occur in 2 soluble forms in aquatic systems, such as Cu(I) (cuprous ion) and Cu (II) (copper ion), among which Cu (II) is considered the most toxic in nature [145]. Cu is considered the most hazardous part of industrial affluents due to its wide range of applications, including electroplating as CuSO 4 [146], petroleum refining as a catalyst [147], Cu 2 O in paints [148], mining, explosives [149], fertilizers [150], and steel industries [151] around the world. Naturally, Cu is distributed in various rocks and soil in minute amounts in mg/kg levels such as granites (as high as 160 mg/kg) [152], shales (as high as 20-200 mg/kg) [153], sulfate-bearing ores (e.g., chalcopyrite and galena) along with volcanic release [154].…”

Accumulation and Analysis of Cuprous Ions in a Copper Sulfate Plating Solution

“…This increases the uncertainty in the absorbance measurement. To overcome this problem, we developed a method of measuring reaction curves by an injection method 14,15 . The second part shows the measurement of Cu(I) based on the injection method.…”