Hermetic plastic packages with applications to ruggedized boards

The feasibility of organic and inorganic deposition providing hermetic circuit boards has been demonstrated . The diffusion barrier is set up by depositing under plasma an inorganic layer instead of an organic layer. SiO₂ was chosen because it is easy to deposit and its properties are well-known. Three layers are necessary: conventional varnish (epoxy or acrylic) as a leveling-off agent, SiO₂ as a diffusion barrier, and parylene deposited under vacuum as a mechanical protective coating for the SiO₂. The board´s hermetic protection is thus deposited in situ and is not obtained by means of a hermetic packaging