ASTM B735-16

Standard Test Method for Porosity in Gold Coatings on Metal Substrates by Nitric Acid Vapor

SIGNIFICANCE AND USE
5.1 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 clad metal and as weldments on the contact surface. The intrinsic nobility of gold enables it to resist the formation of insulating oxide films that could interfere with reliable contact operation.  
5.2 In order that the nobility of gold be assured, 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. This test method is regarded as severe.  
5.4 The relationship of porosity levels revealed by particular tests to contact behavior must be made by the user of these tests through practical experience or by judgement. Thus, absence of porosity in the coating may be a requirement for some applications, while a few pores on the critical surfaces may be acceptable for another. Such ac...
SCOPE
1.1 This test method covers equipment and procedures for using nitric acid vapor for determining porosity in gold coatings, greater than 0.6 μm (25 μin.) in thickness, particularly electrodeposits and clad metals used on electrical contacts.  
1.2 This test method is designed to show whether the porosity level is less or greater than some value that, by experience, is considered by the user to be acceptable for the intended application.  
1.3 A variety of other porosity testing methods are described in Guide B765 and in the literature.2,3 Other porosity test methods are Test Methods B741, B798, B799, and B809.  
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 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 and health practices, and determine the applicability of regulatory limitations prior to use. Specific precautions are given in Section 8 and 9.4.

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: B735 − 16
Standard Test Method for
Porosity in Gold Coatings on Metal Substrates by Nitric
1
Acid Vapor
This standard is issued under the fixed designation B735; 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 B542Terminology Relating to Electrical Contacts andTheir
Use
1.1 This test method covers equipment and procedures for
B741Test Method for Porosity In Gold Coatings On Metal
using nitric acid vapor for determining porosity in gold
5
Substrates By Paper Electrography (Withdrawn 2005)
coatings,greaterthan0.6µm(25µin.)inthickness,particularly
B765GuideforSelectionofPorosityandGrossDefectTests
electrodeposits and clad metals used on electrical contacts.
for Electrodeposits and Related Metallic Coatings
1.2 This test method is designed to show whether the
B798Test Method for Porosity in Gold or Palladium Coat-
porosity level is less or greater than some value that, by
ings on Metal Substrates by Gel-Bulk Electrography
experience, is considered by the user to be acceptable for the
B799Test Method for Porosity in Gold and Palladium
intended application.
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
1.3 Avarietyofotherporositytestingmethodsaredescribed B809Test Method for Porosity in Metallic Coatings by
2,3
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
in Guide B765 and in the literature. Other porosity test
methods are Test Methods B741, B798, B799, and B809.
3. Terminology
1.4 The values stated in SI units are to be regarded as
3.1 Definitions—Many terms used in this test method are
standard. The values given in parentheses are for information
defined in Terminology B542 and terms relating to metallic
only.
coatings are defined in Terminology B374.
1.5 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 corrosion products, n—those reaction products ema-
responsibility of the user of this standard to become familiar
nating from the pores that protrude from, or are otherwise
with all hazards including those identified in the appropriate
attached to, the coating surface after a vapor test exposure.
Safety Data Sheet (SDS) for this product/material as provided
by the manufacturer, to establish appropriate safety and health
3.2.2 measurement area (or “significant surface”), n—the
practices, and determine the applicability of regulatory limi-
surface that is examined for the presence of porosity. The
tations prior to use.SpecificprecautionsaregiveninSection8
significant surfaces or measurement areas of the part to be
and 9.4.
tested shall be indicated on the drawing of the part or by
provision of suitably marked samples.
2. Referenced Documents
3.2.2.1 Discussion—For specification purposes, the signifi-
4
cant surfaces or measurement areas are often defined as those
2.1 ASTM Standards:
B374Terminology Relating to Electroplating portions of the surface that are essential to the serviceability or
functionofthepart,suchasitscontactproperties,orwhichcan
be the source of corrosion products or tarnish films that
1
This test method is under the jurisdiction of ASTM Committee B02 on
interfere with the function of the part.
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
3.2.3 metallic coatings, n—include platings, claddings, or
B02.11 on Electrical Contact Test Methods.
Current edition approved Oct. 1, 2016. Published October 2016. Originally other metallic layers applied to the substrate. The coating can
approved in 1984. Last previous edition approved in 2011 as B735–06 (2011).
comprise a single metallic layer or a combination of metallic
DOI: 10.1520/B0735-16.
layers.
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.
3.2.4 porosity, n—the presence of any discontinuity, crack,
3
Krumbein,S.J.,PorosityTestingofContactPlatings, Proceedings,Connectors
orholeinthecoatingthatexposesadifferentunderlyingmetal.
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 ----------------------
B735 − 16
3.2
...

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: B735 − 06 (Reapproved 2011) B735 − 16
Standard Test Method for
Porosity in Gold Coatings on Metal Substrates by Nitric
1
Acid Vapor
This standard is issued under the fixed designation B735; 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 method covers equipment and procedures for using nitric acid vapor for determining porosity in gold coatings,
greater than 0.6 μm (25 μin.) in thickness, particularly electrodeposits and clad metals used on electrical contacts.
1.2 This test method is designed to show whether the porosity level is less or greater than some value that, by experience, is
considered by the user to be acceptable for the intended application.
2,3
1.3 A variety of other porosity testing methods are described in Guide B765 and in the literature. Other porosity test methods
are Test Methods B741, B798, B799, and B809.
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 become familiar with all hazards including those identified in the appropriate Material Safety Data
Sheet (MSDS)(SDS) 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. Specific precautions are given in Section 8 and 9.4.
2. Referenced Documents
4
2.1 ASTM Standards:
B374 Terminology Relating to Electroplating
B542 Terminology Relating to Electrical Contacts and Their Use
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 test method 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 measurement area (or “significant surface”), n—the surface that is examined for the presence of porosity. The significant
surfaces or measurement areas of the part to be tested shall be indicated on the drawing of the part or by provision of suitably
marked samples.
1
This test method 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 1984. Last previous edition approved in 20062011 as
B735 – 06.B735 – 06 (2011). DOI: 10.1520/B0735-06R11.10.1520/B0735-16.
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
Krumbein, 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’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 ----------------------
B735 − 16
3.2.2.1 Discussion—
For specification purposes, the significant surfaces or measurement areas are often defined as those portions of the surface that are
essential to the serviceability or function of the part, such as its contac
...