Another capacitor question

[Bill Layer]

Hi Kevin,

  How does one figure out what is inside these plastic blobs?
>Thanks in advance,

 Fun question. This requires some messing around, but it's not so difficult
really. The process is one of dissection, and indentification. We will
require samples of both the dilectric and the conductor. So cut up a sample
with your X-acto!

Conductors are either metal foil, or metallized film. The foil may
frequently be identified by color (copper, aluminum) or other basic
physical means, such as stimulating corrosion with acid. The films may be
identified as below.

Insulators are generally paper or plastic films. Mylar can be idntified by
the fact that it is a) metallized and b) very strong in terms of TSI. Other
films (polypro/sty) are much more fragile, and must be differentiated by a
burn test.

Note: burning plastic can give off potentially lethal fumes, so do this
outside and AT YOUR OWN RISK. Polyethyline smells much like candle wax,
polystyrene smells like styrofoam etc. If you don't know how to identify
plastics by smell, get some parts of known composition, then use them as
samples to compare against. When you have determined the compositon, note
whether or not the film is metallized on side or not.

In ceratin metallized film caps (such as the Xicon) my recall is that the
dilectric and conductor are one in the same, since the material can both
conduct and insulate, thus giving greater capacity in a smaller package. 

As for the specifics of this, and also the case types, are there any cap
construction experts out there?


Bill Layer
Sales Technician
<b.layer at vikingelectronics.com>

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