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Samica 4100 – Samica Capacitor
Mica Paper
DESCRIPTION
Natural mica has long been accepted
as an excellent dielectric for capacitors. Samica paper is reconstituted
natural mica. As such, it offers the outstanding features of natural
mica plus the physical handling advantages of a continuous sheet.
This special combination of properties broadens the potential
use of mica dielectrics in capacitors.
Samica 4100 is made from muscovite or Indian ruby mica of fair
stained or better quality. The mica is reduced to a small controlled
flake-size and is then run through a manufacturing process which
results in a homogeneous continuous flexible pure mica sheet with
uniform electrical properties and in thicknesses from 0.75 to
2.0 mil. This mica paper is suitable for the manufacture of rolled
capacitors.
Samica 4100 capacitor papers are well suited for the following
applications:
- High temperature
- High reliability
- High energy density
- Radiation resistance
The capacitors are widely used in aerospace and military applications
where small size and high reliability are of paramount importance.
They are ideally suited to high voltage, high power, energy storage,
plus forming networks and power filtering applications as well
as electronic uses such as blocking, coupling, high frequency
by-pass and filtering. At typical working voltage stress, energy
densities of 0.5 joules/in3 can readily be achieved. For specialized
applications energy densities as high as 2 joules/in3 have been
obtained.
| PHYSICAL PROPERTIES |
| Samica 4100 (unimpregnated
mica paper) |
| Dielectric Constant: |
4.5 - 5.5 (impregnated) |
| Density: |
1.65 g/cm3 |
| Aqueous Extract Conductivity: |
5 micromhos/cm (max) |
PHYSICAL PROPERTIES OF Samica 4100
| NOMINAL THICKNESS | | MIL | High Limit | Low Limit |
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| NOMINAL THICKNESS | | MM | High Limit | Low Limit |
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YIELD |
MIN. AVERAGE
TENSILE STRENGTH |
MIN. AVERAGE*
ELECTRICAL STRENGTH
Volts 60HZ, RMS |
| 0.7 | +0.1 | -0.05 | 0.0177 | +0.00251 | -0.00127 | 18.1 | 33.5 | 2.0 | 0.356 | 650 |
| 0.9 | +0.05 | -0.15 | 0.0229 | +0.00127 | -0.00381 | 14.0 | 25.9 | 3.0 | 0.534 | 850 |
| 1.3 | +0.15 | -0.15 | 0.0330 | +0.00381 | -0.00381 | 10.4 | 19.2 | 4.0 | 0.712 | 1200 |
| 1.5 | +0.15 | -0.15 | 0.0381 | +0.00381 | -0.00381 | 9.0 | 16.7 | 5.0 | 0.890 | 1400 |
| 2.0 | +0.25 | -0.25 | 0.0508 | +0.00508 | -0.00508 | 6.6 | 12.3 | 5.0 | .890 | 1800 |
*Measured with 2" electrodes, short time.
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DESIGN DATA FOR THE MANUFACTURE
OF Isovolta Inc./US Samica-ISOMICA CAPACITORS - Samica 4100
Samica 4100 can be used for rolled capacitors in much the same manner
as Kraft paper. However, Isovolta Inc./US Samica paper contains
air and must therefore, be impregnated. The characteristics of the
capacitor depend on the impregnant that is used and also the fabrication
technique. Thermosetting polyester or silicone resins are frequently
used because of the desirable features of a solid impregnant.
Liquid impregnants such as petroleum or silicone oils may also be used.
The electric strength of impregnated Samica paper is normally
from 4 to 5 kV/mil DC. Typical working voltage stress is from 1.0
to 1.5 kV/mil DC for high reliability applications. If a small arbor
is used and the capacitor is to be flattened, a few turns of Samica
should be wound before the foils are started. This avoids sharp
radii in the active capacitor area and allows maximum electric strength.
Generally, foil tabs are used because of the difficulty in removing
the excess resin from extended foils.
SUGGESTED PROCESSING
1. Samica 4100, like any high quality capacitor paper, is absorbent
and can be easily contaminated by fingerprints, dust, tobacco smoke
and airborne vapors such as solvents, decomposition products and
the like. Suitable precautions must be taken during storage of the
material as well as during the necessary handling in capacitor fabrication.
2. Samica 4100 can be wound on conventional winding machines with
little difficulty provided that high torque starts and stops are
eliminated. It is also important that sheet alignment be carefully
controlled to prevent edge tearing. A humidity in the range of 40
- 50 percent is recommended, as the tensile strength is at a maximum
in the range.
3. Vacuum drying and impregnation techniques utilized in Kraft paper
capacitor technology are recommended because of the sensitivity
of Samica 4100 to moisture. As in the case in the aforementioned
industry, the best drying conditions will vary with the design of
the capacitor and the type of process equipment being used.
4. Low dielectric constant liquid impregnants such as petroleum and silicone oils, perfluorinated liquids and the like have been used over the useful temperature range of the particular liquid involved. Higher dielectric constant liquids such as the Arocolors and Castor oil, for example, are prone to develop an increased level of dielectric loss at elevated temperatures when operated at the lower frequencies. In order to obtain good results in these cases, extreme care must e exercised to prevent even the slightest exposure to moisture.
5. Completed sections, after impregnation, may be tape wrapped and resin end filled or enclosed in any of the standard hermetically sealed cases normally used with paper and/or film dielectrics.
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