Influence of Parameters and Regimes of the Electrodeposition on Hardness of Copper Coatings

Abstract

Correlation among morphological, structural and hardness characteristics of electrodeposited copper coatings is presented in this review paper. Cu coatings were produced applying constant galvanostatic (DC) and pulsating current (PC) regimes on hard silicon (Si(111)) and brass substrates. The parameters of the electrochemical deposition which include the kinds of electrolyte and cathode, the coating thickness and the electrolyte stirring, as well as the parameters defining PC regime, such as the average current density and the current density amplitude, were analyzed. Morphology and structure of Cu coatings were examined by scanning electron microscope (SEM), atomic force microscope (AFM) and by X-ray diffraction (XRD), while hardness was examined by Vickers microindentation. The coatings of Cu on both Si(111) and brass cathodes belong to “soft film (coating) on hard substrate” composite hardness system, and the Chicot–Lesage (C–L) composite hardness model was applied to estimate a hardness of the Cu coatings. Analyzing the examined parameters and regimes of electrodeposition, the critical relative indentation depth (RID)c of 0.14 has been defined by the C–L model. Based on done analyses, it is shown that this RID value, separating a zone where measured hardness corresponds to the coating hardness and a zone where it is necessary to apply the C–L model to determine an absolute hardness of the Cu coatings, has an universal character for the electrolytically produced Cu coatings on Si(111) and brass substrates.

Mechanical Properties of Electrolytically Produced Copper Coatings Reinforced with Pigment Particles

“…The values of these coefficients of different Cu deposits are presented in Table 3. The TC(hkl) and RTC(hkl) coefficient values for the (220) crystal plane were considerably larger than 1 and 25%, respectively, which represent the limiting values for the existence of the preferred orientation in Cu coatings [55,65,66].…”

“…The dependencies of the composite hardness (H c ) as well as the absolute hardness of the coatings calculated by the C-L CHM (H coat ) on the relative indentation depth (RID) are shown in Figure 9a and 9b, respectively. The RID is defined as a quotient between a depth of indentation (h) and a thickness of coating (δ), i.e., RID = h/δ [55, 66,67]. An indentation depth is related to diagonal size as h = d/7 [65][66][67].…”

“…The RID is defined as a quotient between a depth of indentation (h) and a thickness of coating (δ), i.e., RID = h/δ [55, 66,67]. An indentation depth is related to diagonal size as h = d/7 [65][66][67]. To estimate the absolute hardness of the deposits by the C-L CHM, it is necessary to know the hardness of the substrate and a parameter known as Meyer's composite index, calculated for every coating under consideration.…”

“…Using the C-L CHM model, a critical relative indentation depth (RID) c of 0.14 has been established [51,66,68]. When (RID) c < 0.14, H coat > H c , and the deposit hardness corresponds to the measured (composite) hardness.…”