Electroplated Connections Between Carbon Fiber and Nickel

Carbon has become an attractive material for electronic packaging applications, such as interconnects, because of its low density and reasonable electrical conductivity. One challenge in these applications is overcoming the inherent chemical incompatibility between carbon and metals that limits adhesion. Recently, we explored a new technique for electroplating carbon fibers with nickel. Electroplated carbon fiber tows were soldered to nickel metal tabs using SAC 305 (Sn3Ag0.5Cu). The electroplated nickel was found to be free of microvoids with (Ni,Cu)₃Sn₄ forming as intermetallic compounds (IMCs) in an annular region presumed to be Ni₃Sn₄ at the SAC 305-Ni interface. Mechanical characterization of the carbon fiber–nickel interface revealed bond strengths up to 434 N, which is similar to a 22 gauge high strength copper clad steel. Electrical resistances were found to be as low as 1.1 Ω for a 38.1 mm long connection. Carbon–metal connections prepared using silver epoxy were found to have 80% lower load bearing capacity and 10–20% higher electrical resistance. Battery discharge tests indicated that the carbon connections reduced performance by only 4% compared to conventional copper. The performance drop increased to 7% when the discharge time was increased by 50%, indicating some thermal dependence. The electroplating technique is a fairly simple and inexpensive means of enhancing the wettability of carbon fiber to create scalable carbon-based conductors for low current systems.