All Apollo modules are precision multi-layer printed circuit boards made of vibration absorbing foiled material with uniform dielectric permittivity over the surface and enhanced 70 μm copper foil tracks. The PCBs are covered with an antistatic mask, all the vias and pads are immersion gold plated.
Such a solution enables to optimize the conductor’s topology with the view to minimize radiated interference and boosting the intrinsic noise immunity. All the conductors in the digital block, clock signals, data streams and synchronization are engineered to ensure the minimal emission and reflections in the circuit. The DAC ICs masterclock circuits are implemented as a closed pseudo waveguide matching structures in the inner PCB layers. A further increase of noise immunity is achieved by sectoral grounding polygons in a separate board layer and optimal power line tracks.