4. Limitations of plastic packaging

4.1 Water permeability

The first defect attributed to plastic housings is their permeability to water, or even sealing defects between the resin and metal conductors, whereas hermetic housings totally isolate the semiconductor from the outside environment. The moisture permeability of resins allows water to reach the surface of semiconductors, leading to severe corrosion of the metallized areas on early versions of plastic housings, which caused serious problems in US military equipment subjected to tropical environments in the early 1970s. This setback...