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.

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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