Fretting corrosion in electrical connectors

Abstract

This thesis studies how fretting corrosion on electrical connector terminals are influenced by fretting as well as evaluating different analysis methods for studying fretting in industry produced electrical connectors. Fretting is a mechanism of degradation that influences surfaces meant to be stationary in regards to each other but due to for example vibrations a small relative movement exists. It is today largely unknown how temperature influence fretting and the methods currently used by Volvo cars to study this phenomenon in electrical connectors is mostly limited to optical microscopy. A vibration rig was used to study the fretting phenomena. But before fretting tests could be done a fixture needed to be made and vibrations levels measured and analysed. Fretting tests where performed for 24h at 100 m/s2 peak amplitude while sweeping from 100-2000 Hz. These tests where done at 8 different temperatures from -40 ◦C to 100 ◦C. Samples were thereafter analysed using optical, scanning electron and light interference microscopy. It was found that temperature affected fretting in three ways. Firstly higher temperature resulted in higher amplitude relative motion between the terminals and larger fretting scar. Secondly temperature was found to influence the surface structure of the fretting scar. For colder temperatures more abrasive deformation was found where as for higher temperature there were more adhesive deformation. Lastly it was found that the plating thickness degraded faster at higher temperature. On another note SEM microscopy was found to be very useful when analysing fretting and provided many insights which would have been hard to achieve with only optical microscopy. The light interference microscopy however was not found useful in this thesis but this was more likely due to the instrument and not the method.