Copper dissolution

The most serious form of galvanic corrosion occurs in cooling systems that contain both copper and steel alloys. It results when dissolved copper plates onto a steel surface and induces rapid galvanic attack of the steel. The amount of dissolved copper required to produce this effect is small and the increased corrosion is difficult to inhibit once it occurs. A copper corrosion inhibitor is needed to prevent copper dissolution. 

Andersen et al. predicted that similar results would be expected for the corrosion of other multivalent metals oxidizing via lower oxidation states. They also pointed out that their interpretation was consistent with the kinetics of the corrosion of copper in oxygenated HCl solutions. Here the final product is Cu and thus there is no vulnerable intermediate. In consequence, the rate of copper dissolution from either Nj-saturated or 02-saturated HCl solutions was the same at a given potential in conformity with the additivity principle. 

A three-dimensional variation of the theme is offered by the oscillatory behaviour of anodic copper dissolution into a NaCl/KSCN electrolyte mixture.27 This is a complex process involving solid states CuSCN (pKsp = 14.32) and Cu20 or CuOH (pKsp = 14), and CuCl (pKsp = 5.92), and ionic species Cu+, CuCl22, CuCl3, and Cl. Among other plausible schemes,... 

As an illustration, the oscillatory behaviour of anodic copper dissolution discussed in Section III.3, with P elements shown in Table 5, is chosen. The eigenvalue theorem yields three relationships (k= 1,2,3) ... 

Inhibitors form a film on the surface that blocks the dissolution of the substrate. Adsorption of an alkyl-thiol to the surface of the CU3AU alloy resulted in an inaeased surface tension of the gold film this is observed as an increase in the value of <., which depresses dissolution of copper. This behavior resembles inhibition of copper corrosion on a pure copper surface where benzotriazole increases the potential to start significant copper dissolution this was demonstrated by Cruickshank et using in situ AFM. However, when the critical potential for benzotriazole film... 

Copper Dissolution in Alcohol. Copper is believed to be stable to alcohol, at least in bulk, because copper still is used in distillation processes for the production of whisky. However, it was found that the color of copper sols prepared by the gas flow-solution trap method changed from the initial wine red to yellow within 30... 

Gardiner and Casey [65] observed the radicals Of, Of, and MOf, which are formed on various electrode surfaces during oxidation processes on different materials in KOH solutions. Studies of copper dissolution in pyrophosphate [66] resulted in polymeric copper pyrophosphate complexes. 

Another example of a similar rotating disc electrode with an EQCM has been reported by Ritchie et al. [22] for the study of gold and copper dissolution during the electroreduction of oxygen in alkaline cyanide solutions. 

Electrolytes are used in electrochemistry to ensure the current passage in -> electrochemical cells. In many cases the electrolyte itself is -> electroactive, e.g., in copper refining, the copper(II) sulfate solution provides the ionic conductivity and the copper(II) ions are reduced at the - cathode simultaneous to a copper dissolution at the - anode. In other cases of -> electrosynthesis or - electroanalysis, or in case of - sensors, electrolytes have to be added or interfaces between the electrodes, as, e.g., in case of the -> Lambda probe, a high-temperature solid electrolyte. 

Babu and coworkers [26,27] investigated the copper dissolution in the presence of Fe using a copper rotating disk electrode (RDE). The cathodic reaction was separately studied using a platinum rotating disk electrode, while the overall corrosion process was measured on rotating disks. It was... 

Surface polishing can be achieved under certain conditions of electrochemical dissolution, which is a reverse process of electroplating (EP). A simple electrochemical cell is shown in Fig. 10.1. Two metal (e.g., Cu) bars are immersed in an electrolyte. A voltage is applied between the two bars. The one connected to the positive pole of the power supply is anode. The other one is cathode. The positive potential applied to the anode may pump out electrons from copper atoms on the anode surface. As a result, copper dissolution may occur in certain electrolytes. Conversely, copper deposition may occur on the cathode. That is, copper electroplating results when the working electrode is chosen to be cathode, and copper dissolution is accomplished when the working electrode is chosen to be the anode. 

Region I. Minimal etching takes place in this region. Owing to the passivation provided by electrolyte, the copper dissolution is kept at minimal, especially compared to the traditional electropolishing. 

The electrochemical potential is a measure of the driving force (or free energy change) of the oxidation/reduction reactions that occur during metal dissolution. As mentioned, copper dissolution and redeposition may occur by the reduction-oxidation reaction ... 

F ure 4 5 Schematic illustration of the relationship between and [Cu. Increasing [Cu ] increases the reversible potential for copper dissolution, ec,/cu2+ shifts the Cu/Cu oxidation curve, and hence the intersection with the reduction reaction, in the noble direction. Therefore, an increase in [Cu T increases the mixed corrsion potential... 

Figure 4.47 Copper polish rate (independent of titanium) in HjO as a function of Cu(N03)2 concentration. The polish rate decreases with increasing CufNOjlj concentration because the driving force for copper dissolution decreases with increasing Cu activity. (125 mm wafers polished on a Strasbaugh 6CU polisher with 2.5 wt% alumina abrasive, 15 kPa, and 130 cm/sec.)...

In this chapter, we shall first propose a model to explain the removal and planarization mechanisms of copper CMP. Next, we discuss surface layer formation during copper CMP, which is important for planarization, followed by copper dissolution during CMP, which is iii5)ortant to maintain high removal rates. Next a comparison of copper CMP to the Preston equation is made, followed by a discussion of the abrasion mode during copper CMP. Lastly, we investigate the dishing and erosion behavior of copper CMP. 

Figure 7.15 also demonstrates the importance of the NH3 complexing agent in the Cu(N03)2 slurry. Recall from Section 4.6.5 that the copper polish rate decreases when Cu(N03)2 is added to the H2O only slurry. In the H20-only slurry, the increase in Cu ions inhibits dissolution of the abraded material. However, when the Cu(N03)2 is added to the 1 vol% NH4OH slurry, NH3 complexes the Cu " ions from the Cu(N03)2 salt so that the Cu ions do not inhibit copper dissolution. In addition, by complexing the Cu ions, the NH3 drives reaction (7.10) further to the right, increasing the supply of N03 . 

The initial step (eq. 10a) in the proposed mechanism requires adsorption/ binding of the alkyl halide to the metal surface—a process already previously discussed. Anything that might enhance this adsorption should affect the rate and extent of reaction. We have found that o)-bromo-l-alkenes enhanced copper dissolution from alloys (Table V). Comparative studies on brass foil confirmed these observations and also showed that the dissolution of zinc was affected only slightly (Table VI). The compound... 

Figure 2 Cu Polish rate as a function of glycine concentration Figure 4 shows the copper dissolution rate as a function of H2O2 concentration in the presence of 1 wt % glycine. The variation in the open-circuit potential (OCP) measured with respect to SCE at KXK) rpm rotational speed, as measured in an ex situ electrochemical corrosion cell, is also plotted as a function of H2O2 concentration. The copper dissolution rate decreases with increasing peroxide concentration, which is contrary to the expectation. If copper...

Example 5.1 Rate Expression for Copper Dissolution Develop expressions corresponding to equations (5.41-5.46) for the reaction... 

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