Title (English) Ceramic Dielectric Capacitors Classes I, II, III and IV - Part I: Characteristics and Requirements
Document type: Standard
Publication date: 2002-11
Abstract EIA-198-1-F of this standard provides means to characterize ceramic capacitors electrically and mechanically by use of type designators. In addition, this section outlines dielectric classifications, marking specifications and test sequences. Dielectric classification There are four major classifications of ceramic dielectrics, with class I being the least variable with temperature and voltage, and class IV being the most variable. Class I dielectrics are typically used in applications requiring the tightest tolerance. Class I Components of this type are temperature compensating ceramic dielectrics, fixed capacitors of a type suited for resonant circuit applications or other applications where high Q and stability of capacitance characteristics are required. (See table 1.) Class II Components of this classification are fixed, ceramic dielectric capacitors of a type suited for bypass and decoupling application or for frequency discriminating circuits where Q and stability of capacitance characteristics are not of major importance. This classification is further defined as those capacitors having temperature characteristics A through S (see table 3). Class II ceramic dielectrics exhibit a predictable change with time and voltage. Compensation for the aging effect is made by referencing capacitance limits to a future time deemed to be most useful to the buyer; 1,000 hours is normally chosen, but other arrangements may be negotiated between the buyer and seller. Voltage will also cause a temporary capacitance change, and the test sequence should be such that capacitance measurements are not affected by previous voltage tests. The aging rate of a dielectric is essentially constant over many decades of time, i.e., 10 h to 100 h, 100 h to 1,000 h, 1,000 h to 10,000 h, etc., when measured from the time of the last heat of depolarization in manufacture. Restoration of the original capacitance at time of manufacture will occur on heating to 150 oC for one hour, after which normal aging will again commence. Capacitors measured prior to 24 hours may exhibit temporarily high capacitance values that will age downward. Class III Components herein standardized are fixed ceramic dielectric capacitors of a type specifically suited for use in electronic circuits for bypass, decoupling or other applications in which dielectric losses, high insulation resistance and capacitance stability are not of major consideration. This classification is identical to that of class II, except that it is restricted to those capacitors having temperature characteristics T through V (table 3). Class IV This classification is restricted to those components utilizing reduced titanate or barrier layer type construction,. While basically fitting the descriptions of class II and class III, certain other electrical differences can be noted, as described in EIA-198-3-F of this specification.
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Original language English