Characterization of Wetting behavior of commercial flux systems by impedance measurement technique

Evaluation of electrochemical migration (ECM) on printed circuit boards (PCB) is becoming increasingly important for the reliability of electronic systems in automobile. This is triggered by the miniaturization of electronic systems and the increasing electrical loads. Consequently the strength of electrical fields is rising. The demand for material solutions that are resistant to combined moisture and electrical loads is growing. There is a strong demand for further analytical methods to characterize the materials with respect to ECM-risks. Up to now, surface resistance (SIR) measurement has been used as the standard method for assessing the ECM-risk. Electrical impedance measurement offers a more sensitive resolution of the condensation process. Thus, the ECM-risk can already be analyzed before the actual occurrence of the failure mechanism. Furthermore, differences in the condensation behavior on different materials can be distinguished by means of the impedance measurement. In this publication, a measurement methodology is presented, that can characterize the dewing behavior of flux systems under high moisture load. Subsequently, the surface topology is analyzed after the test and the electrical reliability is assessed by chronoamperometry (CA).