| The metallized type of
construction also makes it possible to produce wound
capacitors with larger capacitance values in small sizes
(~ 0.01μF through 100μF and larger). In the case of M
capacitors, thin layers of aluminium (~ 0.03μm) are
vacuum-deposited on the insulating film as conducting
electrodes. In the case of a breakdown, the short circuit
current causes the thin metal coating to evaporate around the
point of failure, without reducing the quality of the
dielectric. An insulating area is formed, the capacitor
remains intact (self-healing). The
capacitance loss of a few pF which this causes, is of no
importance.
With metallized capacitors, the breakdown
strength of the insulating film can be used to the full.
During the production of the capacitors the weak points are
burnt out. This makes it possible to use the thinnest
insulating films right down to < 1μm in
thickness.
In contrast to the advantages of the small
dimensions and the self-healing properties of metallized
capacitors, there is the disadvantage of a limited current
loading capacity as a result of the thin, vacuum-deposited
metal layers.
Advantage: Construction
with the most favorable capacitance/volume value.
WIMA types with metallized
construction:
|
