Capacitor aging characteristics (2): What is the difference between a Class I capacitor and a Class II capacitor?
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A. A Class I capacitor* (C0G, C0H, C0K, etc.) is made from ceramic materials that are not sensitive to temperature changes, thus the capacitance value of a capacitor measured at a low temperature (example -25°C) will not significantly vary from the same capacitor measured at a higher temperature (ex. 75°C).
EIA refers to these as “temperature compensating,” and are measured in ppm/°C.
These capacitors typically have low capacitance values because of the ceramic material used to manufacture them but they exhibit nearly perfect capacitance stability regardless of their temperature, making them an excellent choice for applications in which frequency control is needed such as in radio or television tuners. An example of such is found below:

C0G = +/-30PPM over a temperature range of -55 to +85°C

A Class II capacitor2 (X7R, Y5V, Z5U) is made from ceramic materials that are derived from a barium titanate base which is temperature sensitive. Thus the various temperature classifications stating the extent of the sensitivity over a given temperature range. These capacitors allow for larger capacitance values in the small surface mount packages.

Examples of Class II Temperature Characteristics3 are below.
     X7R = +/-15% over a temperature range of -55 to+125°C
     Y5V = +/-22%, 82% over a range of -30 to+85°C
     Z5U = +/-22%, 56% over a range of +10 to+85°C

Additionally, capacitors made from barium titanate bases (Class II, III, and IV) are ferroelectric and therefore susceptible to “aging” in which a capacitor’s ability to hold capacitance will decrease over time if left in an unheated and/or uncharged state. Class I capacitors are not ferroelectric and therefore do not age.

*EIA-198-D, Page I-1

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