Adapted strategies for dew condensation testing to evaluate the reliability of lead free surface finishes

The advancing usage of electronic devices combined with the progressive trend of miniaturization and increasing functionalities, especially in automotive applications, sets high demands on reliability assurance. As complexity of systems and loads at mission location rise, suitable test strategies are needed, which provide expressive statements about products' reliability. In this article the influence of high humidity and dew condensation on current lead free surface finishes for electronic systems is examined under different climatic loads. Therefore special test patterns with the surface metallizations tin, silver, nickel/gold and Organic Solderability Preservative (OSP) were stressed with a static and two cyclic temperature-humidity test profiles. Both fault times of the different materials and efficiency of the applied test were evaluated with different criteria. In order to investigate fault times, failure mechanisms and evaluation criteria a high precise measurement chain was conceived, to continuously monitor the designed specimens while testing. During the tests both static and sporadic failures with and without optical evidence could be revealed. Depending on climatic profile and used evaluation criterion, the failure times and number of occurred failures varied. According to climatic load and inspected line/space width, the considered materials showed great differences in reliability.