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10/06

Multilayer ceramic capacitors

Cautions and warnings

Notes on the selection of ceramic capacitors

In the selection of ceramic capacitors, the following criteria must be considered:

1. Depending on the application, ceramic capacitors used to meet high quality requirements should

at least satisfy the specifications to AEC-Q200. They must meet quality requirements going

beyond this level in terms of ruggedness (e.g. mechanical, thermal or electrical) in the case of

critical circuit configurations and applications (e.g. in safety-relevant applications such as ABS

and airbag equipment or durable industrial goods).

2. At the connection to the battery or power supply (e.g. clamp 15 or 30 in the automobile) and at

positions with stranding potential, to reduce the probability of short circuits following a fracture,

two ceramic capacitors must be connected in series and/or a ceramic capacitor with integrated

series circuit should be used. The MLSC from EPCOS contains such a series circuit in a single

component.

3. Ceramic capacitors with the temperature characteristics Z5U and Y5V do not satisfy the require-

ments to AEC-Q200 and are mechanically and electrically less rugged than C0G or X7R/X8R

ceramic capacitors. In applications that must satisfy high quality requirements, therefore, these

capacitors should not be used as discrete components (see the chapter “Effects on mechanical,

thermal and electrical stress”, point 1.4).

4. For ESD protection, preference should be given to the use of multilayer varistors (MLV) (see the

chapter “Effects on mechanical, thermal and electrical stress”, point 1.4).

5. An application-specific derating or continuous operating voltage must be considered in order to

cushion (unexpected) additional stresses (see the chapter “Reliability”).

The following should be considered in circuit board design

1. If technically feasible in the application, preference should be given to components having an

optimal geometrical design.

2. At least FR4 circuit board material should be used.

3. Geometrically optimal circuit boards should be used, ideally those that cannot be deformed.

4. Ceramic capacitors must always be placed a sufficient minimum distance from the edge of the

circuit board. High bending forces may be exerted there when the panels are separated and dur-

ing further processing of the board (such as when incorporating it into a housing).

5. Ceramic capacitors should always be placed parallel to the possible bending axis of the circuit

board.

6. No screw connections should be used to fix the board or to connect several boards. Compo-

nents should not be placed near screw holes. If screw connections are unavoidable, they must

be cushioned (for instance by rubber pads).