MEMS switch contact behavior

Electrical contacts with micrometer-scale dimensions are required in applications such as switching and packaging. RF MEMS switches are expected to improve efficiency and reduce power consumption of wireless communications devices, while flip-chip and related packaging methods promise reduced size and improved integration of packaged IC and MEMS devices. Both applications require low contact resistance; switching also demands stable behavior over many billions of cycles without sticking. Despite considerable progress in understanding microscale contacts, adhesion and rising contact resistance continue to cause switch failure. In particular, while many researchers have reported switch failure due to a sudden rise in contact resistance, the science behind this phenomenon is not well-understood. MEMS switches rely on achieving good electrical contact at forces up to 1,000 times smaller than those used for macro-scale switch contacts. As a result, they often suffer from poor reliability and low power handling capability. However, their excellent performance makes them extremely attractive for many RF applications, from radar to communications. My research studies the behavior of these contacts to allow design and operation of switches with longer life and larger power handling capability.

My research has focused on two areas, related to the dominant failure modes for MEMS switches. First, I have investigated the tendency for contact resistance to increase as the switches are cycled. In connection with this, I have studied contact heating and its application to the control of contact resistance. Second, I have explored the factors affecting adhesion of the contacts. My doctoral dissertation presents significant experimental data and computer modeling exploring these topics. I am now continuing to perform research in more depth in these areas.