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. SiO/sub 2/ 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, SiO/sub 2/ as a diffusion barrier, and parylene deposited under vacuum as a mechanical protective coating for the SiO/sub 2/. The board's hermetic protection is thus deposited in situ and is not obtained by means of a hermetic packaging. >