Properties of Plastic Materials and How They Relate to Device Failure Mechanisms

The investigation has been primarily concerned with a search for factors pertinent to mechanisms of failure in microdiode values which entailed design and screening evaluation of various experimental and analytical approaches. The data produced by this effort was reviewed for applicability to these components to verify postulated hypotheses. The interesting results of the program include: 1. The discovery of ammonia in a phenolic molding compound used by a diode manufacturer. Further work revealed that ammonia contamination produced increased and erratic reverse currents and was more pronounced in the presence of moisture. 2. The revelation of the presence of ammonia and other deficiencies in this molding compound induced the manufacturer to investigate other compounds and substitute a better one. 3. The elevated temperature resistivities of coatings were a measure of the performance of these materials as protective systems over diodes under elevated temperature test conditions. 4. In some plastic compounds, a correlation was found between elevated temperature resistivities and water extract resistivities. 5. Teflon, an inert coating with a very high elevated temperature resistivity and high water extract resistivity, was demonstrated to have superior performance under elevated temperature reverse bias and high humidity reverse bias test conditions. 6. The resistivity of water extracts of evaporants was found to be an effective means of indicating the amount of ionic and other conductive impurities in plastic materials.