A new method for local electrochemical measurements at PCBs

Corrosion occurs on metallic materials in the presence of moisture and reactive gases, such as H
2
S, SO
2
or NO
2
and is enhanced by different substances like e.g. chlorides. Particularly electronic materials and components are affected, because they are exposed to increasingly harsh environmental conditions, resulting in damage to corrosive media (e.g. off-shore systems, electronic components in engine compartment of automobiles). Especially for the materials and contacts of micro-and power electronic components, corrosion induced processes are significant reliability limiting. Additionally, depending on process parameters, corrosion can also be induced during manufacturing (e.g. nickel corrosion in pad metallization). We developed an innovative method, based on electrochemical measurements by a local measuring cell that allows corrosion sensitivity analyses of typical metallization systems for substrates and electrical contacts in a very short time. In this paper, we present and discuss the results for electrochemical corrosion testing by the new method in correlation to standard reliability tests, like mixed flow gas testing (MFG) and neutral salt spray testing as well as standardized electrochemical testing for metallization systems pf printed circuit boards. High resolution microstructural analyses after standard testing as well as after miniaturized cyclovoltammetric testing are giving evidence for the running corrosion mechanism. The investigations carried out in this study show the application potential of the new local electrochemical test method and the usability for quality inspection of PCBs.