Periodic Reverse Current Research Articles

Periodic reverse electrodeposition of (1 1 1)-oriented nanotwinned Cu in small damascene SiO2 vias

It is quite challenging to electrodeposit (111)-oriented nanotwinned Cu in small damascene SiO2 vias because of the existence of the sidewalls of the vias. However, by tailoring electroplating waveforms and temperatures, one can overcome this difficulty. Fine pitch nanotwinned Cu (NT-Cu) with high ratio of (111) surface grains were fabricated using periodic reverse (PR) electrodeposition in damascene SiO2 vias. The PR electroplating parameters for via-filling were adjusted by tuning duty cycle and electrolyte temperatures. The PR current may remove randomly oriented nuclei caused by the sidewall-growing front. Thus, the bottom-up filling of the highly (111)-oriented NT-Cu was achieved. (111) surface ratios greater than 85% and 50% were obtained in 10-µm and 2-µm vias in diameter, respectively. Besides, a mathematical model was proposed to predict the (111) surface ratio of the ultra-fine pitch vias fabricated by PR electrodeposition. This investigation offers a new route to the development of NT-Cu interconnects for ultra-fine pitch packaging.

The effect of dissolution by periodic reverse current on the microstructure of bamboo-shaped porous anodic alumina

• Periodic reverse current with small amplitude can promote the growth of the porous layer. • Periodic reverse current has the effect of pore expansion. • The water reduction speed increases during the reverse voltage stage. • The ions driven by the electric field change with the direction of current. • H+ (H2O) and OH− are the main ions that move in the reverse voltage stage. In this paper, the effects of a cyclic anodizing method with the introduction of periodic reverse current are reported. The effects of the periodic reverse current on the microstructure of bamboo-shaped porous anodic alumina (PAA) film are investigated using positive and negative current triangular waveforms. The results of the experiment showed that when the reverse current in each current cycle was I D ' = -5 mA, the growth velocity was the fastest. The analysis found that the introduction of the periodic reverse current was beneficial to increasing the growth velocity of the porous anodic alumina film and had the additional effect of pore expansion. However, with any further increase of the periodic reverse current, the growth velocity of the porous anodic alumina film gradually decreased, and the period length showed a decreasing trend. The main reason for this phenomenon is that in a larger reverse voltage phase, the ions driven by the electric field are mainly H + (H 2 O) and OH − . Then the reaction that occurs is mainly dissolution. With large pore size and adjustable period length, this porous anodic alumina film can be used as a template for the synthesis of nanomaterials, which have practical significance for the synthesis of nanodevices.

Strategy of periodic reverse current electrolysis to synthesize Ferrate(VI): Enhanced yield and removal of sulfachloropyridazine

A strategy of periodic reverse current (PRC) electrolysis in the electrochemical synthesis of ferrate(VI) (FeVIO42-) was developed to alleviate the problem of anode passivation to increase the yield. The use of a cyclic reverse controller in the PRC electrolysis improved the space–time yield of ferrate(VI), demonstrated by carrying out experiments under different polarity switching frequencies (23.1 – 163.6 times per hour), electrolyte flow rates (20–60 rad), and electrolyte concentrations (8–16 mol/L NaOH). At a switching frequency of 112.5 times per hour in 12 mol/L NaOH at an electrolyte flow rate of 60 rad, the available current density increased from 56.6 mA/cm2 (DC electrolysis alone) to 73.2 mA/cm2 (cyclic reverse current electrolysis), and the concentration of ferrate(VI) increased from 0.16 mol/L to 0.28 mol/L. The formation rate of ferrate(VI) under the non-passivated state of the electrode was established. The comparison of the experimentally obtained ferrate(VI) concentrations with the expected levels from the rate equation allows the estimation of the degree of passivation of the electrode which aids in minimizing passivation of the anode in the long-term production of high yield ferrate(VI). The prepared ferrate(VI) successfully removed sulfachloropyridazine (SCP), a sulfonamide antibiotic, in water.

Effect of Humidity on Selective Surface of Solar Absorber Plates

Selective layers Al2O3-Ni were prepared by electrochemical way applying anodic oxidation of aluminium and electrolytical colouring. Anodic oxidation of aluminium was realised in sulphuric resp. phosphoric acid and colouring was carried out under periodic reverse current using different colouring electrolytes on nickel basis. The selective layers were studied and analysed with diverse methods before and after exposition to humidity effect. A way of the selective layer preparation is decisive to the final reaction with humidity and so to degradation of the material.

Void-Free Copper Filling of Through Silicon Via by Periodic Pulse Reverse Electrodeposition

In this work, the Cu electrodeposition was carried out for the filling of through silicon via (TSV) using an additive-free Cu electrolyte and periodic pulse reverse (PPR) current. It was attempted to understand the filling mechanism by PPR plating and then to explore a potential solution for void-free filling in easy electrolytes. The filling results showed that the void size was continually reduced as decreasing current density. A void-free filling was obtained at low current density. During the Cu growth process, a “V” shape filling structure occurred at the upper of the via and the ratio of this structure increased with the decrease of current density. The electrochemical analyzes results demonstrated that at low current density, the potential during forward deposition was more uniform along the depth, and during reverse pulse the potential difference between the shallow and deep location was larger than that at high current density. This result implied that at low current density the reverse pulse played a strong suppression effect that contributed to the “V” shape growth. A competitive growth model between the bottom reversed “V” structure and the upper “V” structure was proposed to explain the void-free filling mechanism in PPR plating process.

Cu filling of TSV using various current forms for three‐dimensional packaging application

PurposeThe purpose of this paper is to overview the effect of electroplating current wave forms on Cu filling of through‐silicon‐vias (TSV) for three‐dimensional (3D) packaging.Design/methodology/approachThe paper takes the form of a literature review.FindingsEffective TSV technology for 3D packaging involves various processes such as via formation, filling with conductive material, wafer thinning, and chip stacking. Among these processes, high‐speed via filling without defect is very important for applying the TSV process to industry with a lower production cost. In this paper, the effects of various current forms on Cu electroplating of TSV such as direct current (DC), pulse current (PC), pulse reverse current (PRC), and periodic pulse reverse current (PPR) are described in detail including recent studies.Originality/valueTSV is a core technology for high density 3D packaging. This paper overviews the recent studies of various current forms on Cu‐filling of TSV.

Periodic reverse current electrodeposited nickel pigmented anodised aluminium

Aluminium anodically oxidised in sulphuric acid electrolyte was pigmented by an electrolytic colouring process with the use of alternating and periodic reverse current. The applied pigmentation electrolytes were based on nickel. The study reports on resistance against humidity of a selective Ni–Al2O3 layer. The samples before and after testing were analysed and compared. The quality of the coating, optical properties and influence of humidity on morphology and composition of the coatings were investigated. The influence of moisture on the quality of the selective Ni–Al2O3 layer is comparable to the commercial solar absorber type.

Pulse nickel electrolytic colouring process of anodised aluminium

The influence of frequencies of periodic reverse current on the morphology of nickel-pigmented aluminium finishes has been studied. The pigmentation of the anodised aluminium was realised by electrolytic colouring in electrolytes with additives and in additives-free electrolytes. Additives-free electrolytes generally provide advantageous quality of pigmentation with regular and homogenous nickel morphology on the aluminium substrate at all applied frequencies. The presence of 5-sulphophtalic acid additive strongly influences the deposit quality. The deposits obtained from nickel sulphate electrolytes at all used frequencies with the use of periodic reverse current with citrate acid and sulphosuccinic acid additives provide the similar poor quality of colouring under studied plating conditions.

Effect of frequency on pulse electrolytic colouring process of anodised aluminium

The influence of frequencies of periodic reverse current on the quality of pigmented aluminium finishes has been studied. Pigmentation was realised by electrolytic colouring with the use of alternating and periodic reverse current (AC and PRC). The applied pigmentation nickel based electrolytes were prepared with and without the use of a complexing agent. Parameters of colour space were measured by spectrocolorimetry. Stripping was carried out in chrome–phosphorous acid to remove the coating of aluminium oxide prepared by anodic oxidation on aluminium. The content of nickel on the treated surface was determined by AAS and XRF analysis and the morphology of the stripped surface was investigated by SEM. A frequency of 50 Hz provided the high quality of the pigmented finishes under the test conditions for electrolytes containing a complexing agent. A frequency of 30 Hz was found to be suitable for pigmentation with electrolytes containing no complexing agent. The results for electrolytes without a complexing agent could be explained by the fact that longer deposition time is necessary to incorporate the nickel particles at a frequency of 30 Hz.

Effect of plating mode and complexing agent on morphology of pigmented anodic alumina coatings

The influence of periodic reverse current and complexing agents (citrate acid, 5-sulphoisophthalic acid) on the morphology of stripped pigmented aluminium finishes has been studied. Pigmentation was realised by electrolytic colouring with usage of alternating and periodic reverse current. The applied pigmentation electrolytes, based on nickel, were prepared with and without usage of a complexing agent. Parameters of colour space were measured by spectrocolorimetry. Stripping was carried out in chromic phosphorous acid to remove the coating of aluminium oxide prepared by anodic oxidation on aluminium. The thickness and mass of the stripped coating were tested and related to stripping time. The content of nickel on the stripped surface was determined by energy dispersive X-ray analysis and morphology of the stripped surface by SEM. In the complexing agent free electrolyte, the use of periodic reverse current improved deposit morphology. The presence of complexing agents generally improved deposit quality over that obtained in complexing agent free electrolytes by alternating current electrolytic pigmentation. Under the test conditions of PRC electrolytic colouring with citric acid, the complexing agent electrolyte negatively influences the colouring of anodic alumina. Periodic reverse current pigmentation was found to yield macroscopically and microscopically highly arranged deposit morphology on the stripped aluminium finishes.

Residual stresses of Ni alloy electrodeposits containing low levels of Fe, P, and B

The effects of process parameters including the alloying elements, additive, pH, temperature and current types on the residual stresses of Ni alloys electrodeposited from a Ni sulfamate bath were investigated using a method involving a flexible bent strip. From the results, it was believed that the residual stresses of the Ni alloy deposits initially depended on a hydride then the alloying elements with increasing levels of those concentrations in the solutions. As the pH of the electrolytes changed from 1 to 3.5, the residual stresses in the deposits varied directly and intensively with the concentration of the NH4 in the solution. By increasing the temperature of the electrolytes from 50 °C to 70 °C, the tensile stresses in the deposits were decreased by the lower hydride that resulted from the decline in the hydrogen evolution reaction. The measured stress values with the current types showed a decrease in the order of the direct current, the pulse current (PC) and the periodic reverse current (PRC). The compactness of the deposit produced by the PC and the increased oxide and decreased hydride during the reverse pulse current of the PRC appeared to degenerate the tensile stresses.

玉野製錬所における銅製錬（日比共同製錬（株））

Tamano Smelter of Hibi Kyodo Smelting Co., Ltd.started its operation in January 1972, employing FSFE (Flash Smelting Furnace with Furnace Electrodes) for smelting and PRC (Periodic Reverse Current) for refining.Its original production capacities were 101, 000 tonnes per year of anode copper and 84, 000 tonnes per year of electrolytic copper.Tamano Smelter has steadily increased production capacity, improved productivity and reduced production cost.The production capacities of anode copper and electrolytic copper have been increased to 226, 300 and 161, 000 tonnes per year, respectively.This paper describes the production capacity expansions, energy saving and the other technical improvements and developments for the last 10 years.

ChemInform Abstract: Zinc Electrowinning Under Periodical Reverse Current (PRC). Behavior of the Cathode and Effects of Lead Impurities.

AbstractZinc electrowinning under PRC is carried out in acidic zinc sulfate solution containing 0.3‐15 mg/l Pb2+.

Zinc Electrowinning under Periodical Reverse Current (PRC): Behavior of the Cathode and Effects of Lead Impurities

Laboratory‐scale experiments of zinc electrowinning under periodical reverse current (PRC) were carried out in acidic sulfate solutions. To study the effects of lead impurities on the zinc cathode, 0.3–15 mg/l of lead were added to the electrolyte. A square wave of current was used to produce the PRC. Current densities of 500 and 1500 A/m2 were investigated under both direct current and PRC. In the case of PRC, the direct and reverse pulses had respective durations of 100s and 0.1–1.0s. The current density of the reverse pulse was set at half the value of the direct pulse. Comparisons were made with conventional dc electrolysis. The presence of 5 mg/l of lead lowered the current efficiency in dc from 94.1 to 93.2%, while in PRC it raised it from 93.2 to 97.6%, using a reverse pulse duration of 0.1s. Correlation between the current efficiencies and the presence of the crystallographic plane (101) was also observed. It suggests that lead in the zinc deposit and the use of PRC influence the crystallographic growth of the zinc deposit. The presence of plane (101) increases the oyerpotential of hydrogen evolution on zinc, and this results in a higher current efficiency. A way of obtaining the beneficial plane is to use PRC and lead in the electrolyte together.

Effect of nickel in zinc electrowinning under periodical reverse current

The effects of nickel impurities were investigated during the electrowinning of zinc in acidic media using periodical reverse current (PRC) along with anodic potential current response and cathodic current efficiency. The chemical and structural characteristics of the cathode deposit were also determined using nickel concentrations of 3, 5 and 10 mg l−1 in sulphuric acid (200 gl−1 H2SO4) containing 60 gl−1 of zinc. The cathodic current efficiency drop caused by nickel was less detrimental in PRC than DC. It was found that the morphology of the deposit plays an important role in the redissolution process caused by impurities. The levelling effect caused by PRC decreases the rate of zinc redissolution, which results in an increase of current efficiency. However for concentrations equal to or greater than 10 mgl−1, the levelling effect caused by PRC is no longer dominant. On the anode nickel did not affect the overpotential of the lead-silver electrode in PRC or DC modes.

Electrorefining of high silver content gold bullion using pulsating currents

High silver contents (>7%) in gold bullion markedly influence electrolytic refining processes. The silver chloride precipitate, formed on the anodic surface, give rise to lower process efficiencies, explained by chloride ion oxidation to the detriment of the gold dissolution reaction. In this study the use of pulsating currents on the electrorefining of a 17.1% silver-gold bullion was investigated. Periodic Reverse Current (PRC) and Asymmetric Alternate Current (AAC) parameters were varied as well as the hydrochloric acid concentration in the electrolyte. The initial laboratory results were confirmed in pilot scale at the Brazilian Mint facilities.

パルスめっきの応用 単一めっき

The application of pulse electrolysis to single metal deposition is reviewed. In comparison with deposits obtained from DC electrolysis, those obtained by pulse electrolysis with pulsed current (PC), periodic reverse current (PR) and asymmetric alternating current (AAC) show a far wider range of change in such properties as hardness, porosity and ductility. Each of the plating parameters-cathodic peak current density ip, on-time Ton, off-time Toff, anodic peak current density iap- strongly influences the properties of the deposits. A high ip, which results in smaller grain size and greater brightness has the effect of increasing hardness relating to structual modification. This is due to the high overpotential that developes along with high ip. A short Ton results in the formation of uniform thin diffusion layers that produce smooth deposits. A long Toff controls the morphology of the deposits because it is during Toff that the recovery of ion concentration, the dissolution and recrystallization of deposits, and the adsorption of anions and surfactants occur. While ductile but soft deposits have been obtained by pulse plating with an iap in additive-free baths, it seems fairly well established that the use of pulse plating parameters that result in grain refinement will also lead to a reduction in porosity of deposits as well as increase in ductility.Pulse electrolysis appears to have great potential for obtaining electrodeposits with a wide range of properties.

ChemInform Abstract: Zinc Electrowinning under Periodical Reverse Current (PRC). Behavior of the Anode and Energy Consumption.

AbstractLaboratory scale electrolysis of Zn has been performed using both conventional dc and new PRC techniques and demonstrates the beneficial effect of PRC electrowinning with respect to current efficiency, specific energy consumption, and productivity.

Zinc Electrowinning under Periodical Reverse Current (PRC): Behavior of the Anode and Energy Consumption

Laboratory‐scale experiments of zinc electrowinning under periodical reverse current (PRC) were carried out in acidic sulfate solution. Direct current densities between 500 and 1500 A/m2 with a direct duration pulse of 100s and a reverse duration pulse of 0.1–1.0s were investigated. The reverse current density was set at half the value of the direct current density. Comparisons were made with conventional dc electrolysis. The specific energy consumption under PRC electrowinning was found to be 2.49 kWh/kg at 500 A/m2, with a cell voltage of 3.00V. Anode potential transients were studied in order to characterize the anodic reactions involved during current reversal. It was found that the reactions proceeding at the lead‐silver electrode during current reversal are dependent upon the reverse charge density. For a reverse charge density beyond 125 C/m2, the layer is reduced to , which may be detrimental to the process. Indeed, in such a case, potential decay curves show that the surface of the anode becomes denser and, thus, the oxygen overpotential rises for a given current density. A lesser value of the reverse charge density was proven to be highly beneficial and was related to the desorption of shielding chemical species such as and . These results allow the use of PRC with a longer duration of the reverse current, which in the past was the drawback of PRC electrolysis. Complementary results with longer reverse times and smaller reverse current densities have confirmed the proposed mechanisms and showed a beneficial effect on the specific energy consumption of the process. A 24h experiment was conducted with these parameters showing the potential applicability of this technique. Nevertheless, more studies are needed on the effects of industrial additives such as permanganates, animal glue, etc., before the use of PRC can be implemented on a full‐size scale.

Fundamental aspects of pulsating current metal electrodeposition VII: The comparison of current density distributions in pulsating current and periodic reverse current electrodeposition of metals

A comparison was made of current density distributions on macroprofiles in pulsating current and periodic reverse current electrodeposition. It was shown that a better distribution was obtained in electrodeposition with a periodic reverse current.