Corona Films
241 Dudley Road
West Townsend, 01474


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Welcome to Corona Films

Corona Films Incorporated is a leading manufacturer of capacitor grade mica paper.  A wide variety of controlled test procedures and over 40 years of experience provide customers with the best mica paper at the lowest possible price.  We specialize in thin sheets from 1/2 mils and any thickness between.


About our Mica Paper Product!

Mica Paper

Mica is used in our capacitor paper because of it's outstanding electrical and thermal properties.  Our mica paper starts out as 100 % muscovite mica.  After cleaning, the mica goes through a special manufacturing process to insure proper flake size and pulp consistency.

Widths: 1/2 inch up to 20 inches, all rolls are slit to order
Shipping: Freight Collect
Returns: By approval of spindles and pads

To confirm phone orders, please fax copy of Purchase Order

Phone: 978-597-6444
Fax: 978-597-5685

Packing List

All information will be presented in a packing list attached to the top box on a skid or the last box on a loose shipment. The packing slip will include code, weight/ square feet, caliper, width, number of rolls per code, box number, and accumulated gross weights in as large an increment as possible under 100 lbs.



Split Spec. Max roll dia. 7.00 in.; Min. roll dia. 4.375 in.; <.0062 width; 3 in. I.D. cores.

The weight samples are dried in an oven or on a hot plate at above 100 degrees C, and weighed on a balance accurate to .01 of a gram. The sheets are labeled front, center, back. The sheets are weighed hot as a group and divided by four for the average. The individual sheets are weighed, the values recorded, and the range calculated. The average value is used on the quality shipping report. The individual values and the range are used for our in-house process control. Weight is a far more accurate measure than caliper. The variables are accurate cutting, the balance, and drying, all controllable variables. Most engineering specifications read and control the average weight in grams / square feet, quality control inspectors have taken a one inch wide strip by 12 feet, weigh it, and say this is the average weight. not so, our values are based on the master roll and the individual 6 inch x 24 inch sheets. If an individual sheet falls outside of a specification that part of the web or the roll is rejected internally. This same reasoning is applied to caliper, however, here we have the standard deviation to estimate the population and the sheet compliance to specification. It is very possible to have a dramatic (.05 mil) change in caliper from one inch to another. this is the result of stacking the deviation 10 times. This is not likely to occur in the actual caliper where four to six rolls across the web are stacked.

Based on the average of (3) six by twenty four inch samples. These are sampled every six inches across the machine.


CF 50

1.75 2.000 2.25
CF 60 2.06 2.305 2.55
CF 70 2.38 2.715 3.05
CF 80 2.73 3.015 3.30
CF 90 3.08 3.440 3.80
CF 120 4.13 4.640 5.15
CF 130 4.55 5.050 5.55
CF 140 4.90 5.300 5.70
CF 150 5.25 5.750 6.25
CF 185 6.48 6.990 7.50
CF 200 7.00 7.600 8.20
CF 300 9.75 10.750 11.75

Tests are based on breaking down 16 two layer test caps at 500 volts/ sec. Rise. The caps are wound on a 1.375 dia. Mandrel. The foil is 1.75 inches by app. 72 inches. The corona film is 2.5 inches wide.

CAT. # TEN. E.B. AV. -KS E.B.

CF 50

1 >1250 1350
CF 60 1 >1800 2050
CF 70 2 >2250 3060
CF 80 2 >2500 3700
CF 90 3 >2500 4400
CF 120 3.5 >2500 5900
CF 130 4 >2500 6500
CF 140 4 >2500 7000
CF 150 4 >2500 7500
CF 185 5 >2500 9250
CF 200 5 >2500 10000
CF 300 5 >2500 10000



The caliper is measured as per ASTM D-374 method C with added techniques. Ten layers are used in all cases. The measurement obtained is a result of the weight of MICA, the surface finish of the sheet, the relative humidity, the acceleration of the drop, the settling time of the anvil, the temperature, plus unknown variables. For quick results, it is best to dry the sheets above 60 degrees C before conditioning at 23 degrees centigrade and 50% RH; this lets the MICA paper come back to the test humidity level rather that dry down to it. Storing the rolls at measuring conditions for 24 to 48 hours prior to testing is an excellent technique. Our procedure is to settle the micrometer on the sheet, lift it off (.3 of a mil) until the sheet can be pulled to the test mark and dropped ( not let down- dropped). The operation is repeated across the sheet; the average calculation and the standard deviation are calculated and recorded with N, the number of readings. The value shown on our quality shipping report is the closest or the same as the outside of the slit roll. Off machine slitting if a 25 lb. master roll the values would be those at the start of the roll. For a 50 lb. master roll the first cut of the slit roll would end at the center of the master roll the second cut would end at the end of that roll. This would be the value on your shipping quality report.


 Average Caliper


Based on test at one inch intervals across each master roll.


CF 50

0.54 0.04 0.025
CF 60 0.61 0.04 0.025
CF 70 0.68 0.04 0.025
CF 80 0.78 0.04 0.030
CF 90 0.88 0.04 0.030
CF 120 1.18 0.05 0.030
CF 130 1.30 0.05 0.030
CF 140 1.40 0.05 0.030
CF 150 1.50 0.06 0.030
CF 185 1.85 0.10 0.035
CF 200 2.00 0.10 0.035
CF 300 2.85 0.20 0.070