The EIA Class 2 dielectric materials are ceramic dielectric materials used in ceramic capacitors. In comparison with the EIA Class 1 dielectrics they tend to have very poor temperature drift, high dependence of capacitance on applied voltage, high voltage coefficient of dissipation factor, high frequency coefficient of dissipation, and problems with aging due to gradual change of crystal structure. Aging causes gradual exponential loss of capacitance and decrease of dissipation factor.
The EIA Class 2 dielectrics in general are usually based on formulas with high content of barium titanate (BT), possibly mixed with other dielectric electroceramics. Due to its piezoelectric properties, they are subject to microphonics. Other oxides added can be the same as used for Class 1 ceramics.
EIA X7R is designed for capacitors with capacity ranging typically between 3300 pF to 0.33 µF (SMT: 100 pF to 10 µF), 10% tolerance. Good for non-critical coupling, filtering, transient voltage suppression, and timing applications. Has high dielectric constant. It is an EIA Class 2 dielectric. Its tolerance over a temperature range of -55 to +125 °C is ±15%.
Y5P and Y5V are other such class 2 ceramics, with temperature range of -30 to +85 °C and wide capacitance change with temperature of ±10% or +22/-82%. Usually used for capacitances between 150 pF and 2 nF (SMT: 10 nF and 10 µF).
Z5U (EIA) or 2E6 (IEC code) — typical for 2.2 nF to 2.2 µF, 20%. Good for bypass, coupling applications. Low price and small size, low temperature stability.
Other commonly used materials are Y5P (2B4 in IEC specs), Y5U, and Z5U (2E5).
The EIA three-character code is derived from the low and high temperature limit, and the range of capacitance change.
|X: -55 °C||4: +65 °C||A: ±1.0%|
|Y: -30 °C||5: +85 °C||B: ±1.5%|
|Z: +10 °C||6: +105 °C||C: ±2.2%|
|7: +125 °C||D: ±3.3%|
|8: +150 °C||E: ±4.7%|
|9: +200 °C||F: ±7.5%|
|T: +22% -33%|
|U: +22% -56%|
|V: +22% -82%|