Layer-by-layer polymer stereolithography fabrication for three-dimensional RF components

Stereolithography (SL) is used innovatively to build high aspect ratio, complicated structures for RF components embedded inside of a package. The layer-by-layer additive laser-based process creates truly three-dimensional structures as opposed to more common two and a half dimension processes such as LTCC. High frequency embedded resonators are fabricated by the SL process to study the fabrication tolerance, effect of imperfections, and metal loss. The dimensional tolerance of this process is found to be 0.187%, which closely matches the variation in the measured resonators´ frequencies, 0.156%. The unloaded Q of the resonators is measured at 3005. As an example application of the three-dimensional fabrication process, a two-pole filter made from SL process is demonstrated with an insertion loss of only 0.287 dB for a 1.83% BW centered at 19.522 GHz. The low-loss performance of the structures indicates that the laser-based process is suitable for the integration of high frequency and high-Q three-dimensional structures within a package.