CERAMIC CAPACITORS

18

www.exxelia.com

Taping : dimensions

Page revised 02/21

COMPOSITION

NPO capacitors are produced by using a dielectric made of titanium dioxide

(Ti O2) modified by magnesium oxide Mg O (white ceramics) or a rare earth

oxide, e.g. Nd2 O3 (other NPO ceramics).

As a consequence, these ceramics are non ferro-electric materials with a low

dielectric constant (

εr ≤ 110).

Other additives are used to dope the dielectric constant up to 300. Though der-

ogating from CG class, doped dielectric constant features a linear temperature

drift and a matchless stability compared with class 2 ceramics.

The wide range of possible NPO dielectric compositions enables to use the ma-

terial best suited to the application :

• standard applications,

• high voltage,

• high temperature,

• microwave,

• power capacitors.

«Temperature coefficient» compositions are particularly suitable for imped-

ance matching. These ceramics usually enable to achieve temperature coef-

ficients from 0 to –1 000 ppm/°C. For specific requirements, other coefficients

can be achieved (e.g. –3 300 ppm/°C).

STABILITY

As

εr is low, these dielectrics are extremely stable with only minor changes

under such stresses as :

• temperature,

• voltage,

• frequency.

In addition, they are not affected by piezo-electric phenomena and their dielec-

tric absorption coefficients are low and even non measurable for dielectrics

with the lowest constants.

MECHANICAL PROPERTIES

Class 1 ceramics are the perfect match for metallic electrodes made of Pd or

Ag-Pd alloy and have a high hardness and mechanical toughness making them

resistant to thermal shocks (wave soldering for instance) and to thermal cy-

cling after mounting on substrates having an expansion coefficient close to

the capacitor one.

Ceramic chips meet CECC 32100 and NF C 93133 standards.

CLIMATIC CATEGORIES

Climatic categories are identified by three-digit codes as per NF C 20700 stan-

dard. Coding method is described in table 6.

e.g. : – 55°C + 125°C / 56 days category is identified by code 434.

TEMPERATURE COEFFICIENT

Temperature coefficient kV(ppm/°C)

kV

Tolerances

Code letter

+ 100

± 30

AG

0

± 30

CG

– 33

± 30

HG

– 75

± 30

LG

– 150

± 30

PG

– 220

± 30

RG

– 330

± 60

SH

– 470

± 60

TH

– 750

± 120

UJ

– 1 000

± 250

QK

General Information NPO/COG (Class 1)