astra77astra®-mt77-pcb-fabrication. Astra® MT77 PCB Fabrication. Astra® MT77 materials are a breakthrough, very low-loss dielectric constant (Dk) product for millimeter waveThe Astra MT77 laminate materials from Isola have been desned for commercial RFmicrowave printed circuit desns. They feature a dielectric constant (Dk) that is stable between -40°C