Polymer dielectrics are widely used in micro-electro-mechanical systems (MEMS) and electronic packaging. Fully curing polymer dielectrics can require lengthy cure cycles. Microwave-induced reactions and curing can occur at temperatures lower than convective heating systems due to localized energy absorption, resulting in faster thermal curing of polymer dielectrics. In this study, the epoxy-based cross-linking and curing of a negative-tone photosensitive polynorbornene (PNB) dielectric by variable-frequency microwave (VFM) processing was investigated as a function of cure time and cure temperature. In additional, the feasibility of curing the polymer in air compared to traditional nitrogen ambient curing was studied. The chemical changes occurring during the cross-linking of the polymer and the effect of processing conditions on the degree of cross-linking in cured films were monitored by Fourier transform infrared spectroscopy (FTIR). FTIR studies show that the chemical structure of VFM-cured PNB films is the same as thermally-cured films. The results also show that rapid curing of PNB by VFM in as little as five minutes is feasible. Further, a significantly higher rate of chemical conversion can be achieved by VFM processing at temperatures lower than conventional thermal curing. The properties of the cured films were studied by comparing the chemical, mechanical, and electrical properties of VFM-cured films to those of the thermally-cured films. The VFM-cured films showed comparable or improved properties compared to the thermally-cured films. The VFM-cured films exhibited higher hardness, higher reduced modulus, and a lower degree of swelling compared to the thermally-cured samples. The residual stress and dielectric constant of VFM-cured films were slightly higher than those of the conventionally-cured films.