Damascene copper electroplating for on-chip interconnections, a process that we conceived and developed in the early 1990s, makes it possible to fill submicron trenches and vias with copper without creating a void or a seam and has thus proven superior to other technologies of copper deposition. We discuss here the relationship of additives in the plating bath to superfilling, the phenomenon that results in superconformal coverage, and we present a numerical model which accounts for the experimentally observed profile evolution of the plated metal.

Damascene copper electroplating for chip interconnections

Nowadays, application of nanocrystalline nickel-tungsten (Ni-W) alloys is receiving a great interest because they are an efficient replacement for hard chromium coatings owing to their premium hardness, wear, and corrosion properties. Moreover, heat-treated nanocrystalline Ni-W alloys demonstrate proper mechanical properties as well as thermal stability at high temperatures. The current paper reviews different aspects of electrodeposition, microstructure, corrosion, oxidation, wear, and mechanical properties Ni-W alloys and nano/micro composites. Besides, heat treatment effects on properties and thermal stability of these alloys are also reviewed.

Ni-W electrodeposited coatings: Characterization, properties and applications

Theoretical and applied studies of tungsten alloys with iron group metals (Me-W) are being carried out worldwide, in the light of their versatile applications. The aim of this paper is to provide an overview of the works on electrodeposition of tungsten alloys with iron group metals, their properties and applications. There are 221 papers reviewing on the following theoretical and practical topics: chemistry of electrolytes used for electrodeposition, codeposition mechanisms, and properties of electrodeposited tungsten alloys. In addition, the formation of W(VI) and iron group metal (Me) complexes (polytungstates and complexes of Me(II) and W(VI)) with citrates and OH− is analysed based on the published data and the calculated distribution of species as a function of pH (ranged from 1 to 10) is provided for solutions with/without citrates. The adduced data are correlated with the compositions of electrodeposited alloys. Various codeposition models of tungsten with iron group metals described in the literature are critically discussed as well. The peculiarities of the structure of tungsten alloys and their thermal stability, mechanical, tribological, and magnetic properties, corrosion performance, their applications in hydrogen electrocatalysis, template-assisted deposition into recesses (aimed to obtain micro- and nanostructures) are also reviewed and mapped.

Modern trends in tungsten alloys electrodeposition with iron group metals

Corrosion of nanocrystalline Ni–W alloys in alkaline and acidic 3.5 wt.% NaCl solutions

Electroplated chromium coatings have been widely used in the automotive, aerospace, manufacturing industries for applications such as internal combustion engine components, hydraulic cylinders and machine tools. Such coatings exhibit attractive properties such as high hardness and excellent wear resistance. Most coatings of this type are deposited from hexavalent chromium compounds, but there is significant environmental concern over such materials, and replacements are being sought. Alloy electrodeposits including nickel–tungsten, nickel–phosphorus and cobalt–tungsten have been considered as potential materials to replace conventional hard chromium deposits, and it has been shown that cobalt-rich alloys can exhibit much lower friction coefficient and higher wear resistance when compared with nickel-rich alloys. This work examines the tribological behaviour of nanostructured cobalt and cobalt–tungsten alloy electrodeposits sliding against a hard steel counterbody, and compares the behaviour of these couples with that associated with sliding of electrodeposited chromium against the hard steel. The wear rates of the cobalt–tungsten alloy electrodeposits are at least an order of magnitude lower than those of the unalloyed cobalt electrodeposits across the range of loads examined. The wear rate of the cobalt–tungsten is also lower than that of the chromium electrodeposit; moreover, at the highest loads examined, the chromium coating was seen to fail catastrophically by fracture whereas the cobalt–tungsten alloy was able to withstand sliding under the same conditions with little damage. In addition, when sliding against the cobalt–tungsten electrodeposit, the wear rates of the hard steel counterbody were two and three orders of magnitude lower than when sliding against the cobalt and chromium electrodeposits respectively. The results presented in this paper (along with an assessment of the literature concerning nickel and nickel–tungsten electrodeposits) show that electrodeposited cobalt–tungsten coatings are one of the strongest contenders for replacement of chromium electrodeposits that have been identified.

Friction and sliding wear behaviour of electrodeposited cobalt and cobalt-tungsten alloy coatings for replacement of electrodeposited chromium

An alkaline non-cyanide plating solution for copper-plating used on iron and steel base and a preparation method thereof relate to a kind of plating solution. The invention provides the alkaline non-cyanide plating solution for copper-plating used on iron and steel base and the preparation method thereof. The plating solution comprises the following components: main salt, complexing agent, conductive salt, activator, cuprous ion complexing agent, pH stabilizer and brightening agent. The method comprises the following steps: adding complexing agent in water, stirring to dissolve complexing agent, obtaining a solution A; adding main salt in the solution A, stirring to dissolve main salt, obtaining a solution B; adding conductive salt in water, stirring to dissolve conductive salt, obtaininga solution C; mixing the solution B and solution C, adjusting the pH value to 2.0-4.5 with sulfuric acid or sodium hydroxide, obtaining a solution D; adding additive in the solution D, adding water to perform constant volume process and obtaining the alkaline non-cyanide plating solution for copper-plating in the desired volume for use, wherein the additive is activator, cuprous ion complexing agent, pH stabilizer and brightening agent.

Alkaline non-cyanide plating solution for copper-plating used on iron and steel base and preparation method thereof

Trivalent chromium sulfate plating solution and a preparation method thereof relate to a kind of plating solution. The invention provides Trivalent chromium sulfate plating solution and the preparation method. The sulfate plating solution with trivalent chromium comprises the following components: main salt, complexing agent, conductive salt, pH stabilizer, plating solution stabilizer, surfactantand promoting agent. The method comprises the following steps: adding complexing agent in water, stirring to dissolve complexing agent, and obtaining a solution A; adding main salt in the solution A,stirring to dissolve main salt, and obtaining a solution B; adding conductive salt in water, stirring to dissolve conductive salt, obtaining a solution C; mixing the solution B and solution C, adjusting the pH value to 2.0-4.5 with sulfuric acid or sodium hydroxide, and obtaining a solution D; adding additive in the solution D, adding water to perform constant volume process and obtaining the sulfate plating solution with trivalent chromium in the desired volume for use, wherein the additive is pH stabilizer, plating solution stabilizer, surfactant and promoting agent.

Trivalent chromium sulfate plating solution and preparation method thereof

Ni—W alloy was electrodeposited from the electrolyte solution containing sodium tungstate, nickel sulfate and ammonium citrate. The electrodeposition, heat treatment, structure, surface morphology and corrosion resistance in w=0.03 NaCl solution, of Ni—W alloys were studied by means of DSC, XRD, SEM and electrochemical techniques. The results showed that the obtained Ni—W alloy electrodeposit with W weight content (ww=0.471) was presented in more typical nanocrystalline. After heat treatment at 400 C for 1 h, the phase structure of the deposits was not obviously changed whereas the agglomerate for the reunion of tiny grains on deposit surface caused the granule in a more smooth morphology, the microhardness was slightly increased and the corrosion resistance was enhanced.

Electrodeposition, structure and corrosion resistance of nanocrystalline Ni-W alloy

The process of electroless copper plating, using sodium hypophosphite as the reductant and sodium citrate as the chelating agent, was studied using liner sweep voltammetry. The effects of temperature, pH, and concentration of nickel ion on the anodic oxidation of hypophosphite and the cathodic reduction of copper ion were tested. The results indicated that the higher bath temperature accelerated both the anodic and the cathodic processes. The increasing pH value promoted hypophosphite oxidation, whereas it blocked the reduction of the copper ion. The nickel ion not only intensively catalyzed the hypophosphite oxidation but also codeposited with the copper ion to form the Cu-Ni alloy. With regard to its catalytic activity, this alloy enabled the continuation of the electroless copper plating reaction.

Electrochemical study on electroless copper plating using sodium hypophosphite as reductant

The invention relates to electrolyte of an electroplating palladium-nickel alloy, in particular to electrolyte. The invention provides electrolyte which can electroplate bright, compact and needle-hole-free electroplating palladium-nickel alloy with different nickel contents (10 to 40 percent), which comprises major salt, complexing agent, additive, conductive salt and pH stabilizer; the major salt comprises a palladium salt and a nickel salt, calculating at the metal palladium, the content of the palladium salt is 1 to 10 g/L, and the mol ratio of the palladium salt and the nickel slat is 1: 1 to 3; the concentration of the complexing agent is 0.2 to 1.0 mol/L; the content of the additive is 0.01 to 1.0 g/L; the content of the conductive salt is 20 to 100 g/L; and the pH stabilizer is of 20 to 50 g/L boric acid or 30 to 90 g/L pyroborate.

Shukai Xu

Papers

Alkaline non-cyanide plating solution for copper-plating used on iron and steel base and preparation method thereof

Trivalent chromium sulfate plating solution and preparation method thereof

Electrodeposition, structure and corrosion resistance of nanocrystalline Ni-W alloy

Electrochemical study on electroless copper plating using sodium hypophosphite as reductant

Electrolyte of electroplating palladium-nickel alloy