astra77astra®-mt77-pcb-fabrication. Astra® MT77 PCB Fabrication. Astra® MT77 materials are a breakthrough, very low-loss dielectric constant (Dk) product for millimeter waveThe main parameters of Isola MT77: Tg=200 °C, Td=360 °C, Dk=3.00, Df=0.0017. Isola Astra MT77 is a low-loss FR-4 process-compatible PCB material