ASTM D748-18
(Specification)Standard Specification for Natural Block Mica and Mica Films Suitable for Use in Fixed Mica-Dielectric Capacitors
Standard Specification for Natural Block Mica and Mica Films Suitable for Use in Fixed Mica-Dielectric Capacitors
ABSTRACT
This specification covers the electrical, visual, and physical properties of natural blocks and films made from mica that are suitable for use in fixed mica-dielectric capacitors. The materials under this specification are of three forms and four classes. Samples should be taken and tested according to the test methods prescribed here. All samples should adhere to the specified values of conducting path, Q value, dielectric constant, weight loss on heating, thickness uniformity, temperature coefficient of capacitance and retrace, and amount of air inclusions, waves, cracks, tears, pin holes, stones, buckles, and ridges.
SIGNIFICANCE AND USE
4.1 The properties included in this specification are those required to identify the types of natural block mica and mica films (cut and uncut) suitable for use in the manufacture of fixed mica-dielectric capacitors. It is possible that other requirements will be necessary to identify particular characteristics. These will be added to the specification as their inclusion becomes generally desirable, and the necessary test data and methods become available. It is possible that natural block mica and mica films that do not conform to the requirements of this specification for capacitor use are capable of meeting the requirements for other critical electrical insulation purposes.
4.2 The system of classifying electrical quality of natural block and mica films (cut and uncut) covered by this specification is based on a combination of electrical and physical properties, and visual qualities specified herein, which the mica must possess. This system differs radically from past practices and previous concepts of mica quality for capacitor use. The electrical classification system does not discriminate against the presence of spots and stains in even first quality electrically selected mica, provided the mica conforms to specific and physical requirements. Appreciable amounts of air inclusions and waviness also are permitted in all electrical quality classes, provided the mica meets specific electrical and physical requirements. Mica meeting these requirements is acceptable without regard to color or origin. However, mica meeting these electrical and physical requirements but having lower visual quality than that meeting the requirements for the visual quality classification is not considered generally as desirable.
4.3 In capacitor fabrication, one or more pieces of cut film or block mica having lower than required electrical and physical properties will possibly prevent meeting the end requirements of the capacitor. It is therefore required that each piece of block ...
SCOPE
1.1 This specification covers natural block mica2 and mica films (cut and uncut) suitable for use in the manufacture of fixed mica-dielectric capacitors, based on electrical, visual, and physical properties as determined by tests specified herein.
1.2 The values stated in inch-pound units are to be regarded as standard.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D748 −18
Standard Specification for
Natural Block Mica and Mica Films Suitable for Use in Fixed
1
Mica-Dielectric Capacitors
This standard is issued under the fixed designation D748; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* films (cut and uncut) suitable for use in the manufacture of
2
fixed mica-dielectric capacitors. It is possible that other re-
1.1 This specification covers natural block mica and mica
quirements will be necessary to identify particular character-
films (cut and uncut) suitable for use in the manufacture of
istics.Thesewillbeaddedtothespecificationastheirinclusion
fixedmica-dielectriccapacitors,basedonelectrical,visual,and
becomes generally desirable, and the necessary test data and
physical properties as determined by tests specified herein.
methods become available. It is possible that natural block
1.2 The values stated in inch-pound units are to be regarded
mica and mica films that do not conform to the requirements of
as standard.
this specification for capacitor use are capable of meeting the
1.3 This international standard was developed in accor-
requirements for other critical electrical insulation purposes.
dance with internationally recognized principles on standard-
4.2 The system of classifying electrical quality of natural
ization established in the Decision on Principles for the
block and mica films (cut and uncut) covered by this specifi-
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical cation is based on a combination of electrical and physical
properties,andvisualqualitiesspecifiedherein,whichthemica
Barriers to Trade (TBT) Committee.
must possess. This system differs radically from past practices
2. Referenced Documents
and previous concepts of mica quality for capacitor use. The
3
2.1 ASTM Standards:
electrical classification system does not discriminate against
D149 Test Method for Dielectric Breakdown Voltage and
the presence of spots and stains in even first quality electrically
Dielectric Strength of Solid Electrical Insulating Materials
selected mica, provided the mica conforms to specific and
at Commercial Power Frequencies
physical requirements. Appreciable amounts of air inclusions
D351 Classification for Natural Muscovite Block Mica and
and waviness also are permitted in all electrical quality classes,
Thins Based on Visual Quality
provided the mica meets specific electrical and physical
D1082 Test Method for Dissipation Factor and Permittivity
requirements. Mica meeting these requirements is acceptable
(Dielectric Constant) of Mica
without regard to color or origin. However, mica meeting these
electrical and physical requirements but having lower visual
3. Terminology
qualitythanthatmeetingtherequirementsforthevisualquality
3.1 For definitions pertaining to this specification see Clas-
classification is not considered generally as desirable.
sification D351.
4.3 In capacitor fabrication, one or more pieces of cut film
4. Significance and Use
or block mica having lower than required electrical and
physical properties will possibly prevent meeting the end
4.1 The properties included in this specification are those
requirements of the capacitor. It is therefore required that each
required to identify the types of natural block mica and mica
piece of block (cut) or film (cut or uncut), or both, be tested for
the electrical requirements and inspected for the visual require-
1
This specification is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of ments listed in this specification.
Subcommittee D09.01 on Electrical Insulating Products.
Current edition approved March 15, 2018. Published March 2018. Originally
5. Forms
approved in 1943. Last previous edition approved in 2014 as D748 – 14. DOI:
10.1520/D0748-18.
5.1 This specification covers the following three forms of
2
Coutlee, K. G., “Electrical Quality Classification of Raw Mica by a Rapid,
natural mica, suitable for use in the manufacture of mica-
Direct-Reading Test Method,” Proceedings, ASTM, Vol 46, 1946, p. 1486.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
dielectric capacitors:
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1.1 Form 1—Full-knife trimmed natural block mica 0.007
Standards volume information, refer to the standard’s Documen
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D748 − 14 D748 − 18
Standard Specification for
Natural Block Mica and Mica Films Suitable for Use in Fixed
1
Mica-Dielectric Capacitors
This standard is issued under the fixed designation D748; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
2
1.1 This specification covers natural block mica and mica films (cut and uncut) suitable for use in the manufacture of fixed
mica-dielectric capacitors, based on electrical, visual, and physical properties as determined by tests specified herein.
1.2 The values stated in inch-pound units are to be regarded as standard.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
3
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D351 Classification for Natural Muscovite Block Mica and Thins Based on Visual Quality
D1082 Test Method for Dissipation Factor and Permittivity (Dielectric Constant) of Mica
2.2 ASTM Adjuncts:
Test electrodes
Grid test electrodes
3. Terminology
3.1 For definitions pertaining to this specification see Classification D351.
4. Significance and Use
4.1 The properties included in this specification are those required to identify the types of natural block mica and mica films
(cut and uncut) suitable for use in the manufacture of fixed mica-dielectric capacitors. It is possible that other requirements will
be necessary to identify particular characteristics. These will be added to the specification as their inclusion becomes generally
desirable, and the necessary test data and methods become available. It is possible that natural block mica and mica films that do
not conform to the requirements of this specification for capacitor use are capable of meeting the requirements for other critical
electrical insulation purposes.
4.2 The system of classifying electrical quality of natural block and mica films (cut and uncut) covered by this specification is
based on a combination of electrical and physical properties, and visual qualities specified herein, which the mica must possess.
This system differs radically from past practices and previous concepts of mica quality for capacitor use. The electrical
classification system does not discriminate against the presence of spots and stains in even first quality electrically selected mica,
provided the mica conforms to specific and physical requirements. Appreciable amounts of air inclusions and waviness also are
permitted in all electrical quality classes, provided the mica meets specific electrical and physical requirements. Mica meeting these
1
This specification is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of Subcommittee
D09.01 on Electrical Insulating Products.
Current edition approved Nov. 1, 2014March 15, 2018. Published December 2014March 2018. Originally approved in 1943. Last previous edition approved in 20112014
as D748 – 00 (2011).D748 – 14. DOI: 10.1520/D0748-14.10.1520/D0748-18.
2
Coutlee, K. G., “Electrical Quality Classification of Raw Mica by a Rapid, Direct-Reading Test Method,” Proceedings,ASTM, Vol 46, 1946, p. 1486.
3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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D748 − 18
requirements is acceptable without regard to color or origin. However, mica meeting these electrical and physical requirements but
having lower visual quality than that meeting the requirements for the visual quality classification is not considered generally as
desirable.
4.3 In capacitor fabrication, one or more pieces of cu
...
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