X2 rated capacitors such as the F862 Series are required to achieve a stable performance during operational life while meeting safety requirements. The metallized film dielectric is a key factor with regards to the safety aspect. For example, the polypropylene dielectric provides excellent self-healing characteristics. However, improvements were necessary to maintain stability in high temperature and high humidity environments. KEMET recognized this challenges and researched materials that would produce more robust parts for extreme applications. As a result, improvements to all of the major capacitor components have been implemented, including the metallization layer, the film used as the dielectric, the resin which fills the package, and the box (or case).
With these changes, the F862 offers very high capacitance stability while still meeting ENEC, CUL and CQC international safety requirements.