Overview

Part 9 of the IEC 60384 series applies to fixed capacitors with ceramic dielectric with a specified temperature coefficient (Class 2) for applications in electronic equipment, including capacitors without supply leads. This standard specifies the preferred rated values and properties for the described type of capacitor, selects the appropriate quality assessment procedures, tests and measurement methods from IEC 60384, and specifies general requirements for operating characteristics. In detail specifications that refer to this sectional specification, the severity of tests and requirements shall be at least as stringent as those defined in this specification; less severe tests and requirements are not permitted. The standard does not apply to fixed surface mount multilayer capacitors of ceramic dielectric; capacitors for radio interference suppression are not included; these are covered by IEC 60384-14. Class 2 fixed capacitors with ceramic dielectric are capacitors with a dielectric of high dielectric constant for screening and coupling or for selective circuits where low losses and high stability of the capacitance value are of secondary importance. The ceramic dielectric is characterized by non-linear capacitance change in the category temperature range. In clause 2 the preferred ratings and properties are discussed, that is the preferred properties and the preferred ratings. Clause 3 describes the quality assessment procedures, in particular the primary manufacturing stage, structurally similar components, confirmed test reports for approved lots, type approval and qualification approval. For single-layer capacitors, the primary manufacturing stage is the metallization of the dielectric to form the electrodes; for multi-layer capacitors, it is the first joint firing of electrodes and ceramic bodies. Clause 4 describes the test and measurement procedures, namely special pretreatment, visual inspection and dimensional control, electrical tests, temperature characteristics of the capacitance, resistance of the terminals, resistance to soldering heat and solderability, and others. The normative Annex A deals with the ageing of the capacitance in fixed capacitors with Class 2 ceramic dielectric. Most Class 2 dielectrics used in ceramic capacitors are ferroelectric and show a ferroelectric Curie temperature. Above this temperature, the dielectric has a highly symmetrical cubic crystal structure, while below the Curie temperature, the crystal structure is less symmetrical. Although this phase transition is very sharp in single crystals, in practical ceramic materials it often extends over a finite temperature range. In all cases, however, it is linked to a maximum in the curve of the capacitance value over temperature. Under the influence of the thermal movement, the ions in the crystal lattice need a longer time after cooling the dielectric below the Curie temperature to take up layers with lower potential energy. This results in the phenomenon of capacitance aging, with the capacitor reducing its capacity uniformly. However, when the capacitor is heated to a temperature above the Curie temperature, ageing takes place, that is the loss of capacitance due to ageing is reversed and ageing begins again when the capacitor cools down. During the first hour after cooling below the Curie temperature, the decrease in capacitance is not well defined, but after this time it follows a logarithmic law that can be expressed using an ageing constant. The aging constant can be specified by the manufacturer for a particular dielectric, or it can be determined by de-aging the capacitor and measuring the capacitance value at two specified times after that. The responsible committee is DKE/K 611 "Kondensatoren" ("Condensers") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Document: references other documents

Responsible national committee

DKE/K 611 - Kondensatoren