Corrosion of Cu Under Highly Corrosive Environments

Cu corrosion in mixed flowing gases has been widely studied. However, most of these studies have been carried out using conditions, which were designed for accelerated tests simulating North America and Western Europe. More and more equipment is being deployed to emerging markets such as APAC (Asia Pacific and China), Eastern Europe, and the Middle East, where they are subjected to much more corrosive environments than those typically seen in North America and Western Europe. There is a need to understand the corrosive conditions in the emerging markets and come up with an accelerated test for products to be deployed in those conditions. 

The Mixed Flowing Gas (MFG) test accelerates corrosion, allowing us to mimic long exposure in the natural environment in a reasonable time in the laboratory. The composition of the mixed flowing gas is aimed to simulate exposure to natural environmental pollutants and other reactive agents. Cu coupons are often used to characterize the mixed flowing gas chamber and the field conditions, which allow one to establish a correlation between the MFG test and aging in the field. Furthermore, Cu metallization is an integral part of any electronics and is often the site prone to corrosion attack. In this work, we investigated the corrosion products on test Cu coupons exposed to harsh conditions by a combination of several analytical techniques. 

This work allowed us to establish a procedure for quantifying corrosion products and led to insights about corrosion mechanisms for copper in highly corrosive environments. Results showed that the corrosion of copper in the highly corrosive MFG testing condition (containing H2S, SO2, Cl2 and NO2) leads mainly to the formation of copper sulphide (Cu2S) at the exposed surface, with the presence of a thin, buried cuprous oxide (Cu2O) layer sandwiched between Cu2S and copper substrate. The thickness of the corrosion products is found to increase linearly with the exposure time.