ASTM F79-69(2019)

Standard Specification for Type 101 Sealing Glass

ABSTRACT
This specification covers Type 101 sealing glass for use in electronic applications. The glass shall have a finish that ensures smooth, even surfaces and freedom from cracks, checks, bubbles, and other laws of a character detrimental to the strength or life of the component or device for which its use is intended. Different test methods shall be performed in order to determine the following properties of the sealing glass: softening point, annealing point, thermal expansion coefficient, contraction coefficient, and bead seal.
SCOPE
1.1 This specification covers Type 101 sealing glass for use in electronic applications.  
Note 1: This specification is primarily intended to consider glass as most generally used, this is, glass in its transparent form as normally encountered in fabricating electronic devices. X1.3 lists sealing metals and alloys that are compatible with this glass. Type 101 glass in other forms such as powdered, crushed, sintered, fibrous, etc. are excluded. The requirements of this specification, as applied to these forms, must be established in the raw glass prior to its conversion.  
1.2 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.

General Information

• Status: Published
• Publication Date: 31-Oct-2019
• ICS: 21.140 - Seals, glands
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaces: ASTM F79-69(2015) - Standard Specification for Type 101 Sealing Glass
• Effective Date: 01-Nov-2019
• Refers: ASTM C336-71(2020) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Aug-2020
• Refers: ASTM F14-80(2019) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-Nov-2019
• Refers: ASTM C598-93(2019) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Aug-2019
• Refers: ASTM C338-93(2019) - Standard Test Method for Softening Point of Glass
• Effective Date: 01-Aug-2019
• Refers: ASTM E228-11(2016) - Standard Test Method for Linear Thermal Expansion of Solid Materials With a Push-Rod Dilatometer
• Effective Date: 01-Sep-2016
• Refers: ASTM F144-80(2015) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-May-2015
• Refers: ASTM C336-71(2015) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-May-2015
• Refers: ASTM F14-80(2015) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-May-2015
• Refers: ASTM C598-93(2013) - Standard Test Method for Annealing Point and Strain Point of Glass by Beam Bending
• Effective Date: 01-Oct-2013
• Refers: ASTM C338-93(2013) - Standard Test Method for Softening Point of Glass
• Effective Date: 01-Oct-2013
• Refers: ASTM F14-80(2010) - Standard Practice for Making and Testing Reference Glass-Metal Bead-Seal
• Effective Date: 01-Apr-2010
• Refers: ASTM F144-80(2010) - Standard Practice for Making Reference Glass-Metal Sandwich Seal and Testing for Expansion Characteristics by Polarimetric Methods
• Effective Date: 01-Apr-2010
• Refers: ASTM C336-71(2010) - Standard Test Method for Annealing Point and Strain Point of Glass by Fiber Elongation
• Effective Date: 01-Apr-2010
• Refers: ASTM E29-08 - Standard Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
• Effective Date: 01-Oct-2008

Overview

ASTM F79-69(2019), Standard Specification for Type 101 Sealing Glass, defines the requirements and properties for Type 101 sealing glass as used in electronic applications. Developed by ASTM International, this standard ensures Type 101 glass meets strict quality requirements, including surface finish, chemical composition, and physical and electrical properties. Its primary focus is transparent Type 101 glass intended for forming hermetic glass-to-metal seals in electronic devices. Adherence to this specification is essential for manufacturers and end users who demand reliable performance and durability in electronic assemblies where glass seals are critical.

Key Topics

• Material Scope: The standard applies specifically to Type 101 glass in its transparent form and excludes other physical forms such as powdered, crushed, or sintered glass. Any requirements for these alternate forms must be confirmed prior to conversion.
• Quality Criteria: Type 101 sealing glass must have a smooth, even surface, and be free of cracks, checks, bubbles, and similar flaws that would negatively impact the glass or device lifecycle.
• Chemical Composition: The glass typically contains silica, alumina, soda, potash, lead oxide, and may have controlled amounts of antimony trioxide, arsenic trioxide, and halogens.
• Physical Properties: Precision requirements for softening point, annealing point, thermal expansion coefficient, and contraction coefficient are established to ensure compatibility with other seal materials.
• Electrical Properties: Table 2 of the standard provides typical values for volume resistivity, dielectric constant, dissipation factor, and loss index, all critical for electrical insulation performance.

Applications

ASTM F79-69(2019) is essential in industries where hermetic sealing of electronic components is required to ensure device integrity and longevity. Main uses include:

• Electronic Device Fabrication: Ensures reliable glass-to-metal seals in vacuum tubes, diodes, transistors, sensors, and other sealed electronic assemblies.
• Glass-to-Metal Sealing: Specifies thermal expansion compatibility with common metals and sealing alloys such as platinum, titanium, Dumet wire, and various nickel-iron alloys, enabling durable joints that withstand thermal cycling and environmental exposure.
• Electrical Insulation: Provides precise standards for the electrical resistivity and dielectric properties of sealing glass, supporting assemblies that require both sealing and electrical insulation.
• Quality Assurance: Used by manufacturers and quality control labs to validate incoming material batches, confirm supplier compliance, and certify finished electronic components.

Related Standards

Several ASTM standards are referenced within ASTM F79-69(2019) to support testing and compliance:

• ASTM C336 and ASTM C598: Test methods for determining annealing point and strain point of glass.
• ASTM C338: Test method for softening point of glass.
• ASTM E228: Test method for measuring thermal expansion and contraction coefficients.
• ASTM D150 and ASTM D257: Methods for evaluating AC loss characteristics, dielectric constant, and electrical resistance of insulating materials.
• ASTM F14, F140, F144: Practices for making and testing glass-metal seals to verify sealing performance and expansion compatibility.
• ASTM F29, F30, F31: Specifications for metals and alloys commonly used in glass-to-metal seals with Type 101 glass.

Practical Value

Compliance with ASTM F79-69(2019) ensures that Type 101 sealing glass used in high-reliability electronic applications meets global quality expectations for hermeticity, durability, and electrical performance. The standard supports manufacturers, designers, and quality engineers in producing components and devices that withstand demanding environments, reducing the risk of failure due to inadequate seals or insulating properties. By following this standard, organizations leverage best practices for material selection, process control, and product validation in the competitive electronics industry.

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:F79 −69 (Reapproved 2019)
Standard Specification for
Type 101 Sealing Glass
This standard is issued under the fixed designation F79; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope F140 Practice for Making Reference Glass-Metal Butt Seals
and Testing for Expansion Characteristics by Polarimetric
1.1 This specification covers Type 101 sealing glass for use
Methods
in electronic applications.
F144 Practice for Making Reference Glass-Metal Sandwich
NOTE 1—This specification is primarily intended to consider glass as
Seal and Testing for Expansion Characteristics by Polari-
most generally used, this is, glass in its transparent form as normally
metric Methods
encounteredinfabricatingelectronicdevices.X1.3listssealingmetalsand
alloys that are compatible with this glass. Type 101 glass in other forms
3. Ordering Information
such as powdered, crushed, sintered, fibrous, etc. are excluded. The
requirements of this specification, as applied to these forms, must be
3.1 Orders for material under this specification shall include
established in the raw glass prior to its conversion.
the following information:
1.2 This international standard was developed in accor-
3.1.1 Form,
dance with internationally recognized principles on standard-
3.1.2 Type of glass,
ization established in the Decision on Principles for the
3.1.3 Dimensions,
Development of International Standards, Guides and Recom-
3.1.4 Marking and packaging, and
mendations issued by the World Trade Organization Technical
3.1.5 Certification (if required).
Barriers to Trade (TBT) Committee.
4. Chemical Composition
2. Referenced Documents
4.1 The typical chemical composition of this glass is as
2.1 ASTM Standards:
follows (Note 2):
C336 Test Method for Annealing Point and Strain Point of
Major Constituents Weight %
Glass by Fiber Elongation
C338 Test Method for Softening Point of Glass
Silica (SiO ) 56.0
Alumina (Al O)1.5
2 3
C598 Test Method for Annealing Point and Strain Point of
Soda (Na O) 4.0
Glass by Beam Bending
Potash (K O) 8.5
D150 Test Methods forAC Loss Characteristics and Permit-
Lead oxide (PbO) 29.0
tivity (Dielectric Constant) of Solid Electrical Insulation
Antimony trioxide (Sb O ) 1.0, max
2 3
D257 Test Methods for DC Resistance or Conductance of
Arsenic trioxide (As O ) 1.0, max
2 3
Insulating Materials
Halogens 0.2, max
E29 Practice for Using Significant Digits in Test Data to
Determine Conformance with Specifications
NOTE 2—Major constituents may be adjusted to give the desired
electricalandphysicalpropertiestotheglass.However,nochangeshallbe
E228 Test Method for Linear Thermal Expansion of Solid
made that alters any of these properties without due notification of, and
Materials With a Push-Rod Dilatometer
approval by, the user.
F14 Practice for Making and Testing Reference Glass-Metal
Bead-Seal
5. Physical Properties
5.1 The material shall conform to the physical properties
prescribed in Table 1. For electrical properties see Table 2 and
This specification is under the jurisdiction of ASTM Committee C14 on Glass
and Glass Products and is the direct responsibility of Subcommittee C14.04 on its Footnote A.
Physical and Mechanical Properties.
Current edition approved Nov. 1, 2019. Published November 2019. Originally
6. Workmanship, Finish, and Appearance
approved in 1967. Last previous edition approved in 2015 as F79 – 69 (2015). DOI:
10.1520/F0079-69R19.
6.1 The glass shall have a finish that ensures smooth, even
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
surfaces and freedom from cracks, checks, bubbles, and other
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
flaws of a character detrimental to the strength or life of the
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. component or device for which its use is intended.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F79−69 (2019)
TABLE 1 Physical Requirements
A A
Property ASTM Test Method Condition Value
Softening point C338 sec 7.1 630 ± 10 °C
Annealing point C336 or C598 sec 7.2 435 ±10°C
Thermal expansion coefficient E228 sec 7.3 8.95 ± 0.20 ppm/°C
0to300 °C
Contraction coefficient E228 sec 7.4 10.10 ± 0.20 ppm/°C
(annealing point minus
15 to 30 °C)
A
Test methods and conditions are detailed in the appropriately referenced section of this specification.
A
TABLE 2 Electrical Properties
mal contraction curve and calculate the mean coefficient of
ASTM Test
linear thermal contraction between a point 15 °C below the
Property Condition Value (Typical)
Method
annealing point and 30 °C in accordance with Procedure B of
B
Volume resistivity (dc) D257 25 °C log R (Ω·cm) 17.0
Test Method E228.
250 °C log R (Ω·cm) 9.9
350 °C log R (Ω·cm) 7.8
7.5 Bead Seal Test—Thethermalcontractionmatchbetween
the glass and a sealing alloy may be determined by preparing
B
Dielectric constant (1 MHz) D150 20 °C 6.7
Dissipation factor (1 MHz) D150 20 °C 0.0014 and testing an assembly in accordance
...