Augusto P. Panella

Contact Physics of Capacitive Interconnects

The resistance and capacitance of a typical multipoint contact interface have been used to assess the impact on high-frequency signal integrity. In the past, it has been shown how fully degraded interfaces could still provide acceptable performance for signal transfers at high data rates. In the case of fully degraded contacts, signals were shown to transfer by capacitive coupling and wave propagation. This paper focuses on the critical parameters of a capacitive-coupled interface. Moreover, the physics of the contact interface is related to contacts that rely on capacitive (as opposed to metallic) coupling and electronic tunneling. These results help define the physics and design requirements for capacitive coupling. In addition, critical performance parameters such as real contact area, film thickness, and the nature of dielectric films are defined for high-frequency signal propagation. This paper provides a contrast between the requirements for high-frequency signal transfer using capacitive coupling and electron tunneling versus traditional metallic contact.

Wave Propagation and High Frequency Signal Transmission across Contact Interfaces

The resistance and capacitance of typical multi-point contact interfaces have been used to assess the impact on high frequency signal integrity. Previous work has reported that the impedance of degraded contact interfaces can affect high frequency signals. Previous work has also related how a contact interface can be treated as a circuit element consisting of a contact resistance in parallel with an effective contact capacitance. It was also stated that further refinement of this technique would help quantify high frequency effects from the multi-point contact impedance. This paper further extends the response of the contact interface to higher frequencies. Specifically, the paper includes research into the relationship of wave propagation relative to contact interface physics. Both transmission line parameters and field effects are used to study the impact of contact geometry and degradation on wave propagation. These effects are quantified and reported in this paper. Moreover, time domain data integrity analysis is used to further qualify the results. It is believed that this study helps provide a basis for further work relating the significance of contact degradation to effective transfer of high-speed packet data.