ASTM B920-16

Standard Practice for Porosity in Gold and Palladium Alloy Coatings on Metal Substrates by Vapors of Sodium Hypochlorite Solution

SIGNIFICANCE AND USE
5.1 Palladium and gold coatings are often specified for the contacts of separable electrical connectors and other devices. Electrodeposits are the form of gold that is most used on contacts, although it is also employed as inlay or clad metal and as weldments on the contact surface. The intrinsic nobility of gold and palladium alloys enables it to resist the formation of insulating oxide films that could interfere with reliable contact operation.  
5.2 In order for these coatings to function as intended, porosity, cracks, and other defects in the coating that expose base-metal substrates and underplates must be minimal or absent, except in those cases where it is feasible to use the contacts in structures that shield the surface from the environment or where corrosion inhibiting surface treatments for the deposit are employed. The level of porosity in the coating that may be tolerable depends on the severity of the environment to the underplate or substrate, design factors for the contact device like the force with which it is mated, circuit parameters, and the reliability of contact operation that it is necessary to maintain. Also, when present, the location of pores on the surface is important. If the pores are few in number and are outside of the zone of contact of the mating surfaces, their presence can often be tolerated.  
5.3 Methods for determining pores on a contact surface are most suitable if they enable their precise location and numbers to be determined. Contact surfaces are often curved or irregular in shape, and testing methods should be suitable for them. In addition, the severity of porosity-determining tests may vary from procedures capable of detecting all porosity to procedures that detect only highly porous conditions.  
5.4 The present test practice is capable of detecting virtually all porosity or other defects that could participate in corrosion reactions with the substrate or underplate. In addition, it can be used on contacts having comp...
SCOPE
1.1 This test practice covers equipment and methods for revealing the porosity of gold and palladium coatings, particularly electrodeposits and clad metals used on electrical contacts.  
1.2 This test practice is suitable for coatings containing gold or 75 % by mass of palladium on substrates of copper, nickel, and their alloys, which are commonly used in electrical contacts.  
1.3 A variety of full porosity testing methods is described in the literature.2,3 These porosity Test Methods are B735, B741, B798, B799, and B809. An ASTM Guide to the selection of porosity tests for electrodeposits and related metallic coatings is available as Guide B765.  
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.  
1.5 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 establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazards, see Section 6.

General Information

• Status: Historical
• Publication Date: 30-Sep-2016
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B02 - Nonferrous Metals and Alloys
• Drafting Committee: B02.11 - Electrical Contact Test Methods

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B920 − 16
Standard Practice for
Porosity in Gold and Palladium Alloy Coatings on Metal
1
Substrates by Vapors of Sodium Hypochlorite Solution
This standard is issued under the fixed designation B920; 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.
1. Scope B735Test Method for Porosity in Gold Coatings on Metal
Substrates by Nitric Acid Vapor
1.1 This test practice covers equipment and methods for
B741Test Method for Porosity In Gold Coatings On Metal
revealing the porosity of gold and palladium coatings, particu-
5
Substrates By Paper Electrography (Withdrawn 2005)
larly electrodeposits and clad metals used on electrical con-
B765GuideforSelectionofPorosityandGrossDefectTests
tacts.
for Electrodeposits and Related Metallic Coatings
1.2 Thistestpracticeissuitableforcoatingscontaininggold
B798Test Method for Porosity in Gold or Palladium Coat-
or 75% by mass of palladium on substrates of copper, nickel,
ings on Metal Substrates by Gel-Bulk Electrography
and their alloys, which are commonly used in electrical
B799Test Method for Porosity in Gold and Palladium
contacts.
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
1.3 Avarietyoffullporositytestingmethodsisdescribedin B809Test Method for Porosity in Metallic Coatings by
2,3
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
the literature. These porosity Test Methods are B735, B741,
B798, B799, and B809. An ASTM Guide to the selection of
3. Terminology
porosity tests for electrodeposits and related metallic coatings
is available as Guide B765.
3.1 Definitions—Many terms used in this practice are de-
fined in Terminology B542 and terms relating to metallic
1.4 The values stated in SI units are to be regarded as
coatings are defined in Terminology B374.
standard. The values given in parentheses are for information
only.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 corrosion products, n—those reaction products ema-
1.5 This standard does not purport to address all of the
nating from the pores that protrude from, or are otherwise
safety concerns, if any, associated with its use. It is the
attached to, the coating surface after a vapor test exposure.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
3.2.2 metallic coatings, n—include platings, claddings, or
bility of regulatory limitations prior to use. For specific
other metallic layers applied to the substrate. The coatings can
hazards, see Section 6.
comprise a single metallic layer or a combination of metallic
layers.
2. Referenced Documents
3.2.3 porosity, n—the presence of any discontinuity, crack,
4
2.1 ASTM Standards:
orholeinthecoatingthatexposesadifferentunderlyingmetal.
B374Terminology Relating to Electroplating
3.2.4 underplate, n—a metallic coating layer between the
B542Terminology Relating to Electrical Contacts andTheir
substrate and the topmost layer or layers. The thickness of an
Use
underplate is usually greater than 0.8 µm (30 µin.).
1
ThispracticeisunderthejurisdictionofASTMCommitteeB02onNonferrous
4. Summary of Practice
Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on
Electrical Contact Test Methods.
4.1 The test practice employs a solution of sodium
Current edition approved Oct. 1, 2016. Published October 2016. Originally
hypochlorite, a material readily available as household bleach.
approved in 2001. Last previous edition approved in 2011 as B920–01(2011).
The test is recommended primarily as a qualitative means for
DOI: 10.1520/B0920-16.
2
For example see: Nobel, F. J., Ostrow, B. D., and Thompson, D. W., “Porosity assessing the plating quality in electrical connectors and is
Testing of Gold Deposits,” Plating, Vol 52, 1965, p. 1001.
desirable because it uses readily available reagents and equip-
3
Krumbien, S J., Porosity Testing of Contact Platings, Proceedings, Connectors
mentandisextremelyinexpensive,simple,andfast.Inthetest,
and Interconnection Technology Symposium, Oct. 1987, p. 47.
4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B920 − 16
thecoatedpartstobeevaluatedaresuspendedaboveasolution fromprocedurescapable
...

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: B920 − 01 (Reapproved 2011) B920 − 16
Standard Practice for
Porosity in Gold and Palladium Alloy Coatings on Metal
1
Substrates by Vapors of Sodium Hypochlorite Solution
This standard is issued under the fixed designation B920; 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
1.1 This test practice covers equipment and methods for revealing the porosity of gold and palladium coatings, particularly
electrodeposits and clad metals used on electrical contacts.
1.2 This test practice is suitable for coatings containing gold or 75 % by mass of palladium on substrates of copper, nickel, and
their alloys, which are commonly used in electrical contacts.
2,3
1.3 A variety of full porosity testing methods is described in the literature. These porosity Test Methods are B735, B741,
B798, B799, and B809. An ASTM Guide to the selection of porosity tests for electrodeposits and related metallic coatings is
available as Guide B765.
1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.
1.5 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 establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For specific hazards, see Section 6.
2. Referenced Documents
4
2.1 ASTM Standards:
B374 Terminology Relating to Electroplating
B542 Terminology Relating to Electrical Contacts and Their Use
B735 Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor
5
B741 Test Method for Porosity In Gold Coatings On Metal Substrates By Paper Electrography (Withdrawn 2005)
B765 Guide for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
B798 Test Method for Porosity in Gold or Palladium Coatings on Metal Substrates by Gel-Bulk Electrography
B799 Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
B809 Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
3. Terminology
3.1 Definitions—Many terms used in this practice are defined in Terminology B542 and terms relating to metallic coatings are
defined in Terminology B374.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 corrosion products, n—those reaction products emanating from the pores that protrude from, or are otherwise attached to,
the coating surface after a vapor test exposure.
3.2.2 metallic coatings, n—include platings, claddings, or other metallic layers applied to the substrate. The coatings can
comprise a single metallic layer or a combination of metallic layers.
1
This practice is under the jurisdiction of ASTM Committee B02 on Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on Electrical
Contact Test Methods.
Current edition approved Oct. 1, 2011Oct. 1, 2016. Published October 2011October 2016. Originally approved in 2001. Last previous edition approved in 20062011 as
ε1
B920 – 01 (2006)(2011). . DOI: 10.1520/B0920-01R011.10.1520/B0920-16.
2
For example see: Nobel, F. J., Ostrow, B. D., and Thompson, D. W., “Porosity Testing of Gold Deposits,” Plating, Vol 52, 1965, p. 1001.
3
Krumbien, S J., Porosity Testing of Contact Platings, Proceedings, Connectors and Interconnection Technology Symposium, Oct. 1987, p. 47.
4
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
5
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B920 − 16
3.2.3 porosity, n—the presence of any discontinuity, crack, or hole in the coating that exposes a different underlying metal.
3.2.4 underplate, n—a metallic coating layer between the substrate and the topmost layer or layers. The thickness of an
underplate is usually greater than 0.8 μm (30 μin.).
4. Summary of Practice
4.1 The
...