With applications in the aerospace, military, and commercial sectors, MEMS switches have a large potential market. Compared to current solid state RF technologies such as Field Effect Transistor switches and PIN diodes, RF MEMS switches generally have lower insertion loss (0.1 dB up to 100 GHz), higher isolation (because of lower off-state capacitances of 2-4 fF at 0.1-60 GHz), lower power consumption (10-100 nJ per switching cycle), and higher linearity. However, the greatest flaw of this maturing technology is reliability, especially when hot switched. æIn the switch environment, the switch contact may experience either of two switching modes. Cold switching refers to the application of an electrical signal across the switch only when the contact is fully closed. Hot switching refers to the application of a signal while the switch is being opened and closed. Compared to cold switching, hot switching leads to shorter contact lifetimes. Currently, there are four categories of material transfer mechanisms postulated to account for damage in hot switched micro-contacts: field evaporation, field emission, arc/pseudo-arc transfer, and ohmic heating/bridge transfer. Experiments on micro-fabricated contact specimen are conducted using a customized SPM-based testing system. Using qualitative (SEM micrographs) and quantitative (a novel volume measurement technique) data this poster will explore, describe, and attempt to explain the contact damage in MEMS contacts under various hot and cold switching conditions. Specifically, polarity-dependent material transfer is explored, leading edge hot switching damage is compared to trailing edge hot switching damage, and the electrical behavior upon making/breaking of contact is explored.