ASTM B844-98(2010)
(Guide)Standard Guide for Silver-Tin Oxide Contact Material
Standard Guide for Silver-Tin Oxide Contact Material
SIGNIFICANCE AND USE
The methods for manufacture (proprietary or otherwise) of these materials vary significantly among suppliers, and these methods influence such properties as arc erosion, contact resistance, and tendency to weld in service. Since the performance of contacts in a device depends on numerous factors outside the contact itself (opening speed, closing speed, contact pressure, contact bounce, environmental variations, assembly technique and variations, etc.) this guide cannot ensure performance control in the application. As part of the qualification on initial samples it is recommended that the user electrically test the materials in a functional manner for all devices applicable to the material's use. This guide will provide a means for the contact manufacturer and contact user to reach agreement on the details of material to be supplied for a specific use and how to provide reasonable assurance that future lots will be similar in properties and microstructure to the initial test of sample contacts supplied.
SCOPE
1.1 This standard provides guidelines for users and manufacturers of silver-tin oxide material produced in strip, rod, wire, and part form for electrical contact applications.
1.2 Silver-tin oxide refers to contact material containing silver, tin oxide, and other metal oxide which may be used for either improving the processing or performance of the material.
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 Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: B844 − 98(Reapproved 2010)
Standard Guide for
Silver-Tin Oxide Contact Material
This standard is issued under the fixed designation B844; 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 4. Significance and Use
1.1 This standard provides guidelines for users and manu-
4.1 The methods for manufacture (proprietary or otherwise)
facturers of silver-tin oxide material produced in strip, rod,
ofthesematerialsvarysignificantlyamongsuppliers,andthese
wire, and part form for electrical contact applications.
methods influence such properties as arc erosion, contact
resistance, and tendency to weld in service. Since the perfor-
1.2 Silver-tin oxide refers to contact material containing
mance of contacts in a device depends on numerous factors
silver, tin oxide, and other metal oxide which may be used for
outsidethecontactitself(openingspeed,closingspeed,contact
eitherimprovingtheprocessingorperformanceofthematerial.
pressure, contact bounce, environmental variations, assembly
1.3 This standard does not purport to address all of the
technique and variations, etc.) this guide cannot ensure perfor-
safety concerns, if any, associated with its use. It is the
mance control in the application.As part of the qualification on
responsibility of the user of this standard to become familiar
initial samples it is recommended that the user electrically test
with all hazards including those identified in the appropriate
the materials in a functional manner for all devices applicable
Material Safety Data Sheet (MSDS) for this product/material
to the material’s use. This guide will provide a means for the
as provided by the manufacturer, to establish appropriate
contact manufacturer and contact user to reach agreement on
safety and health practices, and determine the applicability of
the details of material to be supplied for a specific use and how
regulatory limitations prior to use.
to provide reasonable assurance that future lots will be similar
in properties and microstructure to the initial test of sample
2. Referenced Documents
contacts supplied.
2.1 ASTM Standards:
B311 Test Method for Density of Powder Metallurgy (PM)
5. Materials and Manufacture
Materials Containing Less Than Two Percent Porosity
B476 Specification for General Requirements for Wrought 5.1 Various processes may be utilized to produce silver-tin
Precious Metal Electrical Contact Materials oxide contact materials. Internal oxidation of a silver-tin alloy
is a viable method. However, if oxidized at relatively low
NOTE 1—Test Method B311 is applicable to fully dense forms.
pressures, a binary silver-tin alloy develops a stable layer of tin
Specification B476 is applicable to strip, rod, or wire only. Test Method is
oxide at the surface which inhibits further oxidation of the
applicable to forms less than 99 % dense.
material. Because of this phenomenon, usually at least a third
3. Terminology
element (such as indium) is added to the alloy in order to
promoteinternaloxidation.Oxidationmaybecarriedoutunder
3.1 Definitions of Terms Specific to This Standard:
elevated oxygen pressure and also at various temperatures;
3.1.1 lot, n—(usage involving discrete manufactured
oxidation conditions determine size and distribution of the
parts)—all parts of the same form, and dimensions, from the
resultingoxideparticles.Othermanufacturingprocessesutilize
same alloy melt or batch of particulate (if manufactured by
powder metallurgical techniques. Silver- and tin-oxide pow-
consolidation), processed under the same conditions, and
ders may be blended and consolidated by heat or pressure, or
submitted for inspection at the same time.
both, into wire or strip suitable for further processing, or may
be blended and sintered directly into contacts. Methods that
can be used to prepare silver- and tinoxide powder mixtures
This guide is under the jurisdiction of ASTM Committee B02 on Nonferrous
Metals and Alloys and is the direct responsibility of Subcommittee B02.05 on
include either coprecipitation or sequential precipitation of
Precious Metals and Electrical Contact Materials.
silver and tin compounds from aqueous solutions, coating of
Current edition approved Oct. 1, 2010. Published October 2010. Originally
tin-oxide particles by precipitation of silver from an aqueous
approved in 1993. Last previous edition approved in 2004 as B844 – 98 (2004).
DOI: 10.1520/B0844-98R10. solution, and powder atomization of a silver-base alloy fol-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
lowed by internal oxidation of the atomized powder.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
5.1.1 Silver-tin oxide materials are used in various tempers
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. dependent on the attachment and fabrication process utilized.
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B844 − 98 (2010)
5.1.2 For purposes of attachment or device performance, ods to be employed shall be mutually agreed upon between the
silver-tin oxide contact material is often produced with a producer and the user.
conductive or brazable layer of material or backing. Incorpo- 6.2.2 It should be noted that the operating characteristics of
ration of such a layer is often an integral part of the silver-tin silver-tin oxide materials with different additives may be very
oxide manufacturing process. different. Certain operating characteristics such as welding
5.1.3 Silver-tin oxide materials vary from full theoretical resistance, electrical erosion, and others may improve or
density to about 95 % of theoretical density depending on the degrade as a result of additives. As a result of differences in
specific manufacturing period. these materials due to both compositional and processing
5.1.4 The tin-oxide particle size and uniformity in combi- differences, no substitutions in material should be made with-
nation with the contact density and chemical composition (see out operational te
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