CERAMIC CAPACITORS

137

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General characteristics

Page revised 06/20

The capacitor with silver-palladium terminations exhibits a magnetic susceptibility

around three times higher than that of the capacitor with copper terminations. This

means that for a very strong requirement for non-magnetic criteria, the copper ter-

minations are better than the silver-palladium ones;

Both these terminations are suitable for non-magnetic applications as their magne-

tization is always below 0.10 uem.CGS/g.

IV.3. Trimmer Capacitors

On the basis of the 0.10 uem.CGS/g limit previously discussed, the behavior of ceramic

trimmer capacitors could also be studied.

From the above chart, the following points may be deduced:

These three ceramic trimmer capacitors are all suitable for non-magnetic applica-

tions, as their magnetization is always below 0.10 uem.CGS/g;

The AT9402 and AT9410 exhibit very good paramagnetic behavior and are therefore

recommended for applications with a very strong non-magnetic requirement.

IV.4. PERMEABILITY

IV.4.1. Definitions

Some engineers prefer to define the magnetic behavior of a component using its per-

meability. Therefore, an empirical limit above which components are not suitable for

non-magnetic applications seems to have been set at 1.0005 for the relative perme-

ability µR.

This relative permeability could be deduced from our measurements using the following

method:

Mass susceptibility Xg is given by the slope of the Mg = f (H) curve

Volume susceptibility Xv is equal to: Xg x [density]

Relative permeability is finally equal to: 1 + Xv

IV.4.2. Examples

Let’s consider the 501 CHB 4R7 BC we measured previously. From the experimental

curve, we find a mass susceptibility Xg of 10–7 uem.CGS. As our components exhibit

a density around 4, the volume susceptibility Xv is then equal to 4 x 10–7 uem.CGS.

Finally, permeability µR is then equal to 1.0000004, which is well below the theoretical

limit of 1.0005

Even if there is no mass susceptibility Xg for a magnetic component – except at very

low fields but customer’s applications are far above this range – we can run the exercise

for the 501 CHB 4R7 BS studied previously. From the first two dots on the experimen-

tal curve, we find a mass susceptibility Xg of 0.5 x 10–3 uem.CGS. As our components

exhibit a density around 4, the volume susceptibility Xv is then equal to 2 x 10–3 uem.

CGS. Finally, permeability µR is then equal to 1.002, which is, as expected, well above

the theoretical limit of 1.0005

V. CONCLUSIONS

C.N.R.S. and EXXELIA have conducted a comprehensive study of the non-magnetic be-

havior of electronic components. This document describes the results of that study on

multilayer porcelain capacitors and ceramic trimmer capacitors.

It flags up the following points:

The measurements made on magnetic and non-magnetic components enable us to

define a first limit for magnetization of around 0.10 uem.CGS/g above which compo-

nents can no longer be rated as non-magnetic;

All our non-magnetic components – both porcelain capacitors and ceramic trimmer

capacitors – are below this limit and are therefore Magnetism-free Rated. To enable

R&D engineers to quickly distinguish in the EXXELIA portfolio which components

are guaranteed for non-magnetic applications, the following specific logo will be

added to specific series in our Application datasheets:

The above logo certifies that a specific electronic component is Magnetism-free

Rated;

Concerning non-magnetic applications - mainly medical systems -, the best solu-

tion to obtain a very low magnetization ceramic capacitor is to use one with copper

terminations;

The silver leads, made from pure silver, are completely non-magnetic;

Concerning standard applications like telecom, industrial, military or space systems,

as any system induces a magnetic field, the use of non-magnetic components would

rule out magnetic losses and therefore improve the overall performances, particularly

in switch-mode operations.

General Information