ASTM B628-98(2021)

Standard Specification for Silver-Copper Eutectic Electrical Contact Alloy

ABSTRACT
This specification covers 72% silver-28% copper (eutectic) alloy rod, wire, strip, and sheet material for electrical contacts. The material shall be finished by such operations (cold working, heat treatment, annealing, turning, grinding, or pickling) as are required to produce the prescribed properties. The alloy materials shall conform to the chemical composition and mechanical property requirements. All tests shall be conducted at room temperature.
SCOPE
1.1 This specification covers 72 % silver-28 % copper (eutectic) alloy rod, wire, strip, and sheet material for electrical contacts.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to become familiar with all hazards including those identified in the appropriate Safety Data Sheet (SDS) for this product/material as provided by the manufacturer, to establish appropriate safety, health, and environmental practices, and determine the applicability of regulatory limitations prior to use.  
1.4 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-2021
• ICS: 77.120.99 - Other non-ferrous metals and their alloys
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.05 - Precious Metals and Electrical Contact Materials and Test Methods

Relations

• Refers: ASTM B277-18(2024) - Standard Test Method for Hardness of Electrical Contact Materials
• Effective Date: 01-Apr-2024
• Refers: ASTM B277-95(2012) - Standard Test Method for Hardness of Electrical Contact Materials
• Effective Date: 01-May-2012
• Refers: ASTM B476-01(2012) - Standard Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials
• Effective Date: 01-May-2012
• Refers: ASTM B277-95(2006) - Standard Test Method for Hardness of Electrical Contact Materials
• Effective Date: 01-Jun-2006
• Refers: ASTM B476-01(2006) - Standard Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials
• Effective Date: 01-Jun-2006
• Refers: ASTM B476-01 - Standard Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials
• Effective Date: 10-May-2001
• Refers: ASTM B277-95(2001) - Standard Test Method for Hardness of Electrical Contact Materials
• Effective Date: 15-Aug-1995

Overview

ASTM B628-98(2021): Standard Specification for Silver-Copper Eutectic Electrical Contact Alloy is an internationally recognized standard developed by ASTM International. This specification defines the requirements for 72% silver-28% copper (eutectic) alloys in rod, wire, strip, and sheet form, primarily intended for use in electrical contact applications. Adherence to this standard ensures that the alloy materials supplied exhibit consistent quality, chemical composition, and mechanical properties suitable for demanding electrical and electronic applications.

Key Topics

• Material Composition
  • The alloy consists of 71.0-73.0% silver, balance copper, with tight limits on total impurities (maximum 0.15%).
  • Specific controls on trace elements such as zinc, iron, cadmium, lead, nickel, aluminum, and phosphorus.
• Product Forms
  • Applicable to rod, wire, strip, and sheet for electrical contacts.
• Manufacturing Processes
  • Materials are finished by processes such as cold working, heat treatment, annealing, turning, grinding, or pickling to meet the specified properties.
• Mechanical Properties
  • Tables define minimum and maximum ultimate tensile strength, elongation, and hardness (e.g., Rockwell 30T scale for strip/sheet) for different tempers.
• Testing and Inspection
  • All tests are conducted at room temperature.
  • Includes visual inspection, hardness or tension testing, dimensional verification, and chemical analysis as required by the purchase order.

Applications

The silver-copper eutectic alloy covered by ASTM B628 is widely used for high-performance electrical contacts, where excellent electrical conductivity, mechanical strength, and durability are essential. Typical sectors and product applications include:

• Switchgear and Relays
  • Contact points and arms benefiting from high conductivity and resistance to arc erosion.
• Electric Connectors and Terminals
  • Sheet and strip forms are often used for connectors requiring precision and robust mechanical properties.
• Power Transmission Equipment
  • Components in circuit breakers and industrial relays utilizing rod and wire materials.
• Instrumentation and Control Devices
  • Reliable contact elements in measurement and automation systems.

By specifying ASTM B628-compliant materials, manufacturers and end users ensure reliable performance, safety, and regulatory compliance for components that play vital roles in power distribution and control systems.

Related Standards

For those applying or referencing ASTM B628, it is important to consider the following related documents to ensure full compliance and integration into quality systems:

• ASTM B476: Specification for General Requirements for Wrought Precious Metal Electrical Contact Materials
• ASTM B277: Test Method for Hardness of Electrical Contact Materials
• U.S. Federal Standards (when specified by contract)
  • Fed. Std. No. 102 (Preservation, Packaging, and Packing Levels)
  • Fed. Std. No. 123 (Marking for Shipment - Civil Agencies)
• U.S. Military Standards
  • MIL-STD-129 (Marking for Shipment and Storage)

Keywords: silver-copper alloy, electrical contacts, ASTM B628, eutectic alloy, mechanical properties, precious metal alloy, conductivity, electrical contact material standards

Adopting ASTM B628 as the basis for material selection and procurement helps organizations achieve consistent product quality, interoperability, and long-term reliability in critical electrical contact applications.

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:B628 −98 (Reapproved 2021)
Standard Specification for
Silver-Copper Eutectic Electrical Contact Alloy
This standard is issued under the fixed designation B628; 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.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 3. General Requirements
3.1 SpecificationB476andTestMethodB277shallapplyto
1.1 This specification covers 72% silver-28% copper (eu-
all materials produced to this specification.
tectic) alloy rod, wire, strip, and sheet material for electrical
contacts.
4. Manufacture
1.2 Thevaluesstatedininch-poundunitsaretoberegarded
4.1 Raw materials shall be of such quality and purity that
as standard. The values given in parentheses are mathematical
thefinishedproductwillhavethepropertiesandcharacteristics
conversions to SI units that are provided for information only
prescribed in this specification.
and are not considered standard.
4.2 The material shall be finished by such operations (cold
1.3 This standard does not purport to address all of the
working, heat treating, annealing, turning, grinding, or pick-
safety concerns, if any, associated with its use. It is the
ling) as are required to produce the prescribed properties.
responsibility of the user of this standard to become familiar
5. Chemical Composition
with all hazards including those identified in the appropriate
Safety Data Sheet (SDS) for this product/material as provided 5.1 Materialproducedunderthespecificationshallconform
by the manufacturer, to establish appropriate safety, health, to the requirements as to chemical composition prescribed in
and environmental practices, and determine the applicability Table 1.
of regulatory limitations prior to use.
6. Mechanical Requirements
1.4 This international standard was developed in accor-
6.1 The material shall conform to the mechanical properties
dance with internationally recognized principles on standard-
prescribed in Table 2 or Table 3.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- 6.2 All test specimens shall be full thickness or diameter
mendations issued by the World Trade Organization Technical when practical.
Barriers to Trade (TBT) Committee.
6.3 Alltestsaretobeconductedatroomtemperature,about
68°F (20°C).
2. Referenced Documents
7. Inspection and Testing
2.1 ASTM Standards:
7.1 Material furnished under this specification shall be
B277Test Method for Hardness of Electrical Contact Mate-
inspected by the manufacturer as detailed in the applicable
rials
provisions of Specification B476 and as listed below.
B476Specification for General Requirements for Wrought
7.1.1 Visual inspection at 10×.
Precious Metal Electrical Contact Materials
7.1.2 Temper test (hardness or tension, but not both). A
tensiontestisrecommendedforstripbelow0.030-in.(0.8-mm)
thickness and for wire of any diameter. A tension test is
This specification is under the jurisdiction of ASTM Committee B02 on
preferred when permitted by part size and quantity.
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
7.1.3 Dimensional tests.
B02.05 on Precious Metals and Electrical Contact Materials.
7.1.4 Spectrographic or chemical analysis when indicated
Current edition approved Nov. 1, 2021. Published December 2021. Originally
approved in 1977. Last previous edition approved in 2016 as B628–98(2016). by the purchase order.
DOI: 10.1520/B0628-98R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 8. Keywords
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
8.1 composition; electrical contacts; impurities; precious
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. metals; silver copper alloy
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B628−98 (2021)
A
TABLE 1 Chemical Composition
Element Weight %
Silver 71.0 to 73.0
Copper balance
Total of all impurities 0.15
Zinc 0.06 max
Iron 0.05 max
Cadmium 0.05 max
Lead 0.03 max
Nickel 0.01 max
Aluminum 0.005 max
Phosphorus 0.03 max
Total others 0.06 max
A
Analysis is regularly made for the elements for which specific limits are listed. If,
however, the presence of “other” elements is suspected or indicated in the course
of routine analysis, further analysis shall be made to determine that the total of
these “other” elements and the listed impurities are not in excess o
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