High-performance VAT Photopolymerization Processes for the Fabrication of Micro-channels and Stubs in sub-THz devices

Electromagnetic (EM) wave filters operating in the 90–300 GHz frequency range require micro-features, such as channels with integrated stubs, having tight dimensional tolerances to ensure minimal insertion loss and high selectivity. Their fabrication can be enabled by Additive Manufacturing (AM), such as VAT Photopolymerization processes (VPP), which offer capabilities for fabricating micro-scale components suitable for high-frequency applications. In this context, this work investigates the suitability of Stereolithography (SLA) for fabricating geometries that characterize sub-THz filters, with widths and lengths ranging between 0.5 and 1 mm, and depths of approximately 0.55 mm. A pre-analysis comparing two SLA systems, i.e., Low Force Stereolithography (LFS) and Low Force Display (LFD) processes, allows the selection of the latter as the most accurate for producing the micro-channels and stubs. Therefore, six final samples are printed with the LFD machine and with high-resolution resins. Visual inspection and dimensional accuracy measurements, performed via confocal microscope, show excellent surface fidelity for micro-features, especially on the top surfaces.