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Discussions about conductive materials often begin with whether a new material can match copper’s conductivity. Though it’s relevant if conductivity is the sole concern, in practice it never is the case. In applications such as signal cables for aerospace and defense, EMI shielding in cable assemblies, and high-cycle flex cables in robotics, conductivity is one of several important factors — essential, but not sufficient.

An often-overlooked question is whether copper has been used in applications where its density of 8,960 kg per cubic meter was accepted as an unavoidable cost, simply because no lighter material could meet all required performance criteria. Such applications exist, and mass-normalized metrics provide a clear method to identify them.