Stanley J. Wallace

An investigation of the contact behavior of electric distributed filament contacts

The findings of a preliminary experimental investigation into the contact behavior of nonmetallic, distributed filament contacts (DFCs) are reported. The study was designed to probe the effects of numerous fibrous micro-contacts upon the electro-mechanical behaviors of composite contacts and to compare the resultant behaviors with conventional metal contacts. Four composite materials, representing the variables of interest to this study, were processed into electrical contacts by two novel manufacturing methods. Static and dynamic tests reveal that DFC contact resistances can saturate at a level of as low as 10 g, and that DFC contact stability is, similar to that of metals, dependent upon the contact loads and the contact surface hardness, but nearly independent of the properties of the carbon fibers. The results suggest that it is possible to tailor DFC electro-mechanical characteristics over a range that is not possible with monolithic contact materials by the judicious selection of matrix resin, fiber loading, and surface microstructures.

Carbon Fiber-Based Grid Array Interconnects

This paper presents a new type of grid array electrical interconnect that uses carbon fiber as the conductive medium. Characterization of the electrical properties suggest that carbon fiber-based interconnects can be applied across different packaging levels, such as semiconductor die to substrate, integrated circuit package-to-board and board-to-board interconnections. Multiple interconnect contacts have been integrated to provide multiple interconnections within a single assembly. Each interconnect contact consists of a large number of carbon fibers which can act cooperatively to provide a high degree of reliability and predictability to the interconnect function. An optional metal coating, such as nickel, copper, aluminum or gold, can be applied over the carbon fibers to enhance conductivity and solderability. These novel interconnects can be joined to conventional circuitry by several techniques including pressure/physical contact, solder, and conductive adhesives (U.S. Patent 007 220 131).

A Statistical Mechanical Model of Electrical Carbon Fiber Contacts

This paper presents a model for electrical carbon fiber contacts. In the model, a statistically distributed fiber length was considered at contact surfaces. A technique of dealing with this kind of contact surfaces with statistically determined, or specifically undeterminable, geometry was developed. The results were compared with the experimental data obtained previously. Also, the contact behaviors of electrical carbon fiber contacts were discussed and some specific contact properties, which were also observed experimentally, were clarified. A contact resistance decreasing rate was defined in a logarithmic-logarithmic scale coordinate. A constant-rate contact region was identified. The objective of this research is to provide a theoretical basis for the contact surface designs of electrical connectors.