Study on the corrosion behavior of metallic copper in aqueous solutions of HN03 and HC1 and the corrosion inhibiting effects of N and S

摘要

Metallic copper is used in microelectronics because of its superb electrical and thermal conductivity in form of bond wires, heat sinks or lead frames. In the production process these components are normally embedded into a polymer which is known not to be entirely free of water. This can lead to corrosion reactions and local changes in the pH value, especially if a potential is applied, and can ultimately lead to failure of the device. In this process, the effect of anions, e.g. Cr, NO_3~-, which are present from former production steps, is not fully researched. Therefore, this work centers on copper and its passivation in aqueous environments including chloride ions at neutral and acid pH value. Additionally, the environmentally friendly and therefore so-called 'green' inhibitor cysteine was tested in reference to inhibition efficiency and critical concentration in some of the tested solutions. The study was performed at room temperature (25 °C) and the inhibitor was tested in varying concentrations. Measurements were done using a three electrode set-up with copper metal as a working electrode, platinum as a counter electrode and silver chloride as a reference electrode. On this set-up three different kinds of measurement were conducted: (i) Potentionamic polarization measurement, (ii) linear polarization resistance (LPR) and (iii) electrochemical impedance spectroscopy (EIS). The potentiostatic polarization measurement was done from -200 mV vs ocp up to +200 mV vs. ocp. The LPR was measured with an amplitude of 10 mV and a scanning rate of 1 mV/s. The EIS was measured from 0.1 to 65 000 Hz with an amplitude of 10 mV. Furthermore, imaging techniques like optical microscopy and scanning electron microscopy (SEM) were performed to visualize the surface of metallic copper after immersion in the corrosive solution.