There can be two considerations for Product Life:
1) How long a specific Fair-Rite Part Number will remain ACTIVE and orderable.
For the most part, Fair-Rite will continue to manufacture and sell current parts as long as there is reasonable demand. Parts may become inactive if there are no recent orders over a period of 3 years, these parts may be reactivated if the order quantity justifies and may require non recurring engineering (NRE) charge or higher than usual minimum order quantity (MOQ) in order to reinstate. Aside from the amount of sales, parts could become obsolete if process equipment necessary to produce the part is no longer available or if the specific material type becomes obsolete / no longer manufactured.
2) Expected LIFE TIME after manufacture and failure mode of the part.
Ferrite cores, by themselves not including conductors or other additional materials added, should not fail over time. Ferrites are a type of ceramic made from metal oxides, they will not rust and will not melt unless exposed to temperatures in excess of 1000 degrees C. Ferrites can crack or break due to thermal shock. Ferrites are rather hard and brittle, they can break or crack upon mechanical impact. If the core has a severe crack perpendicular to the magnetic path, it can cause significant reduction in permeability/inductance or impedance. Large pieces chipped off ( > 20% of total volume) can reduce a suppression component’s impedance, chips smaller than this should not cause a significant reduction in impedance. When operated within specified constraints and limitations of the component and material type, there should be no failure in function of its intended performance. Part performance will derate under certain operating conditions.
Specific Considerations by Component Type
When a component is specified for an application, the designer needs to consider limitations of the ferrite material, geometry and winding for expected performance. Ferrite material performance will derate with: temperature, DC bias currents and high AC excitation. At high AC excitation (and power loss): thermal runaway could occur and the extreme temperature swing could cause breakage and cracking of the component.
The Snap-It components with plastic cases are intended for indoor use. The plastic material can degrade with extended exposure to UV, or storage and operation in an environment with temperatures outside the suggested range of 0 – 85ºC. At temperatures below 0ºC: the plastic case becomes brittle and can crack; at temperatures above 85ºC: the plastic case becomes soft and can permanently deform.
Multi-layer chip beads all have a recommended maximum operating current which represents a 35 degree C temperature rise, these parts can endure currents about twice the rated current for short periods of time. The failure mode from overcurrent will be either a short caused by burning within the interior conductors or an open due to burning at the end terminals. The usual consideration of reduced solderability of exposed end terminals due to aging needs to be considered for storage of unused chip beads.
Other Fair-Rite parts which have conductors provided from the factory, for the most part, have a recommended maximum operating current of 5A. In all cases this maximum current represents a limitation for impedance derating when operating in differential mode, the part derates such that there is very little attenuation provided. In terms of an actual failure: the mode would be an open circuit due to the conductor fusing (inversely proportional to the conductor cross sectional area). Another consideration is the possibility of overheating due to the I2R of the conductor causing the ferrite material to heat up beyond the material’s Curie Temperature. Operation above a material’s Curie Temperature will cause the material to lose its magnetic properties. These properties return once the component goes back below Curie temperature. The same concerns for reduced solderability during extended storage times exist for these components as for that of chip beads.
For perminvar materials (Fair-Rite types 61, 67 and 68) the composition and crystal structure, while providing desirable performance attributes, are susceptible to external stresses. Perminvar materials can be irreversibly changed when exposed to high amplitude magnetic fields- both radiated from an external source and through high magnetic excitation via the winding. The failure mode will be a small increase in permeability/inductance and a large increase in losses, especially noticeable at the upper area of the material’s optimal frequency range.