A capacitor assembly that is stable under extreme conditions is provided. More particularly, the assembly includes a capacitor element that is positioned within an interior cavity of a housing. The housing includes a base to which the capacitor element is connected. The housing also includes a lid that contains an outer wall from which extends a sidewall. An end of the sidewall is defined by a lip extending at an angle relative to the longitudinal direction and having a peripheral edge located beyond a periphery of the sidewall. The lip is hermetically sealed to the base. In some cases, the peripheral edge of the lip is also coplanar with an edge of the base. The use of such a lip can enable a more stable connection between the components and improve the seal and mechanical stability of the capacitor assembly, thereby allowing it to better function under extreme conditions.