  We obtain series expansions of the $q$-scale functions of arbitrary
spectrally negative L\'evy processes, including processes with infinite jump
activity, and use these to derive various new examples of explicit $q$-scale
functions. Moreover, we study smoothness properties of the $q$-scale functions
of spectrally negative L\'evy processes with infinite jump activity. This
complements previous results of Chan et al. [7] for spectrally negative L\'evy
processes with Gaussian component or bounded variation.
