ASTM B799-95(2014)
(Test Method)Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Sulfur-Dioxide 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 inlay or 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 Palladium coatings are sometimes specified as alternatives to gold on electrical contacts and similar electrical component surfaces, both as electrodeposits and as inlay or clad metal. This test method is particularly suitable for determining porosity in palladium coatings, since the reactive atmosphere that is used does not attack the palladium if the specified test conditions are followed. In contrast, palladium coatings are attacked by nitric acid (HNO3) and other strong oxidizing agents, so that Test Method B735 cannot be used for determining the porosity in such coatings.
5.3 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.
5.4 Methods for determining pores on a contact surface are most suitable if they enable the...
SCOPE
1.1 This test method covers equipment and methods for determining the porosity of gold and palladium coatings, 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 which 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 the literature. 2, 3 Other porosity test methods are B735, B741, B798, 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 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. For specific hazards, see Section 6.
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Designation: B799 − 95 (Reapproved 2014)
Standard Test Method for
Porosity in Gold and Palladium Coatings by Sulfurous Acid/
Sulfur-Dioxide Vapor
This standard is issued under the fixed designation B799; 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 2. Referenced Documents
1.1 This test method covers equipment and methods for 2.1 ASTM Standards:
determining the porosity of gold and palladium coatings, B374Terminology Relating to Electroplating
particularly electrodeposits and clad metals used on electrical B542Terminology Relating to Electrical Contacts andTheir
contacts. Use
B735Test Method for Porosity in Gold Coatings on Metal
1.2 This test method is designed to show whether the
Substrates by Nitric Acid Vapor
porosity level is less or greater than some value which by
B741Test Method for Porosity In Gold Coatings On Metal
experience is considered by the user to be acceptable for the
Substrates By Paper Electrography (Withdrawn 2005)
intended application.
B765GuideforSelectionofPorosityandGrossDefectTests
1.3 Avarietyofotherporositytestingmethodsaredescribed
for Electrodeposits and Related Metallic Coatings
2,3
in the literature. Other porosity test methods are B735,
B798Test Method for Porosity in Gold or Palladium Coat-
B741, B798, and B809. An ASTM Guide to the selection of
ings on Metal Substrates by Gel-Bulk Electrography
porosity tests for electrodeposits and related metallic coatings
B809Test Method for Porosity in Metallic Coatings by
is available as Guide B765.
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
1.4 The values stated in SI units are to be regarded as
3. Terminology
standard. The values given in parentheses are for information
3.1 Definitions—Many terms used in this test method are
only.
defined in Terminology B542 and terms relating to metallic
1.5 This standard does not purport to address all of the
coatings are defined in Terminology B374.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to become familiar
3.2.1 corrosion products, n—those reaction products ema-
with all hazards including those identified in the appropriate
nating from the pores that protrude from, or are otherwise
Material Safety Data Sheet (MSDS) for this product/material
attached to, the coating surface after a vapor test exposure.
as provided by the manufacturer, to establish appropriate
safety and health practices, and determine the applicability of
3.2.2 measurement area (or “significant surface”), n—the
regulatory limitations prior to use. For specific hazards, see
surface that is examined for the presence of porosity. The
Section 6.
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.
This test method is under the jurisdiction of ASTM Committee B02 on
3.2.2.1 Discussion—For specification purposes, the signifi-
Nonferrous Metals and Alloys and is the direct responsibility of Subcommittee
cant surfaces or measurement areas are often defined as those
B02.11 on Electrical Contact Test Methods.
Current edition approved Oct. 1, 2014. Published October 2014. Originally
approvedin1988.Lastpreviouseditionapprovein2009asB799–95(2009).DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/B0799-95R14. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
For example see: Nobel, F. J., Ostrow, B. D., and Thompson, D. W., “Porosity Standards volume information, refer to the standard’s Document Summary page on
Testing of Gold Deposits,” Plating, Vol 52, 1965, p. 1001. the ASTM website.
3 5
Krumbien, S. J., “Porosity Testing of Contact Platings,” Proceedings, Connec- The last approved version of this historical standard is referenced on
tors and Interconnection Technology Symposium, Oct. 1987, p 47. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B799 − 95 (2014)
portionsofthesurfacethatareessentialtotheserviceabilityor atmosphere that is used does not attack the palladium if the
functionofthepart,suchasitscontactproperties,orwhichcan specified test conditions are followed. In contrast, palladium
be the source of corrosion products or tarnish films that coatings are attacked by nitric acid (HNO ) and other strong
interfere with the function of the part. oxidizing agents, so thatTest Method B735 cannot be used for
determining the porosity in such coatings.
3.2.3 metallic coatings, n—include platings, claddings, or
other metallic layers applied to the substrate. The coatings can
5.3 In order for these coatings to function as intended,
comprise a single metallic layer or a combination of metallic
porosity, cracks, and other defects in the coating that expose
layers.
base-metal substrates and underplates must be minimal or
absent, except in those cases where it is feasible to use the
3.2.4 porosity, n—the presence of any discontinuity, crack,
contacts in structures that shield the surface from the environ-
orholeinthecoatingthatexposesadifferentunderlyingmetal.
ment or where corrosion inhibiting surface treatments for the
3.2.5 underplate, n—a metallic coating layer between the
deposit are employed. The level of porosity in the coating that
substrate and the topmost layer or layers. The thickness of an
maybetolerabledependsontheseverityoftheenvironmentto
underplate is usually greater that 0.8 µm (30 µin.).
the underplate or substrate, design factors for the contact
deviceliketheforcewithwhichitismated,circuitparameters,
4. Summary of Test Method
and the reliability of contact operation that it is necessary to
4.1 The test method employs concentrated sulfurous acid
maintain. Also, when present, the location of pores on the
(H SO ),whichemitssulfurdioxide(SO )gasaccordingtothe
2 3 2
surface is important. If the pores are few in number and are
equilibrium reaction:
outside of the zone of contact of the mating surfaces, their
H SO 5SO 1H O (1)
presence can often be tolerated.
2 3 2 2
The procedure is similar to one first proposed by Lee and 5.4 Methods for determining pores on a contact surface are
Ternowski. most suitable if they enable their precise location and numbers
tobedetermined.Contactsurfacesareoftencurvedorirregular
4.2 Exposure periods may vary, depending upon the degree
in shape, and testing methods should be suitable for them. In
of porosity to be revealed. Reaction of the gas with a
addition, the severity of porosity-determining tests may vary
corrodable base metal at pore sites produces reaction products
fromprocedurescapableofdetectingallporositytoprocedures
that appear as discrete spots on the gold or palladium surface.
that detect only highly porous conditions.
Individual spots are counted with the aid of a loupe or
low-power stereo microscope.
5.5 Thepresenttestmethodiscapableofdetectingvirtually
all porosity or other defects that could participate in corrosion
4.3 This test method is suitable for coatings containing
reactions with the substrate or underplate. The test is rapid,
95% or more of gold or palladium on substrates of copper,
simple,andinexpensive.Inaddition,itcanbeusedoncontacts
nickel, and their alloys which are commonly used in electrical
having complex geometry such as pin-socket contacts (al-
contacts.
though with deep recesses it is preferred that the contact
4.4 This porosity test involves corrosion reactions in which
structures be opened to permit reaction of the sulfur dioxide
the products delineate defect sites in coatings. Since the
with the interior significant surfaces).
chemistry and properties of these products may not resemble
5.6 Therelationshipofporositylevelsrevealedbyparticular
those found in natural or service environments this test is not
teststocontactbehaviormustbemadebytheuserofthesetests
recommended for prediction of the electrical performance of
through practical experience or by judgment. Thus, absence of
contacts unless correlation is first established with service
porosity in the coating may be a requirement for some
experience.
applications, while a few pores in the contact zone may be
5. Significance and Use acceptable for others.
5.1 Gold coatings are often specified for the contacts of 5.7 This test is considered destructive in that it reveals the
separable electrical connectors and other devices. Electrode-
presence of porosity by contaminating the surface with corro-
posits are the form of gold that is most used on contacts,
sion products and by undercutting the coating at pore sites or
although it is also employed as inlay or clad metal and as at the boundaries of the unplated areas. Any parts exposed to
weldmentsonthecontactsurface.Theintrinsicnobilityofgold
this test shall not be placed in service.
enables it to resist the formation of insulating oxide films that
5.8 This test is intended to be used for quantitative descrip-
could interfere with reliable contact operation.
tions of porosity (such as number of pores per unit area or per
5.2 Palladium coatings are sometimes specified as alterna-
contact) only on coatings that have a pore density sufficiently
tives to gold on electrical contacts and similar electrical
low that the corrosion sites are well separated and can be
component surfaces, both as electrodeposits and as inlay or
readily resolved. As a general guideline this can be achieved
clad metal. This test method is particularly suitable for deter-
for pore densities up to about 100/cm . Above this value the
mining porosity in palladium coatings, since the reactive
testsareusefulforthequalitativedetectionandcomparisonsof
porosity.
5.9 Forthesepurposes,the measurement area,or significant
Lee, F. and Ternowski, M., Proceedings Ninth International Conference on
Electrical Contact Phenomena, Chicago, 1978, p. 215. surface, shall be defined as those portions of the surface that
B799 − 95 (2014)
are essential to the serviceability or function of the par
...
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: B799 − 95 (Reapproved 2009) B799 − 95 (Reapproved 2014)
Standard Test Method for
Porosity in Gold and Palladium Coatings by Sulfurous Acid/
Sulfur-Dioxide Vapor
This standard is issued under the fixed designation B799; 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 methods for determining the porosity of gold and palladium coatings, 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 which 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 the literature. Other porosity test methods are B735, B741,
B798, 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 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. For specific hazards, see Section 6.
2. Referenced Documents
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
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
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”) , 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.
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, 2009Oct. 1, 2014. Published October 2009October 2014. Originally approved in 1988. Last previous edition approve in 20052009 as
B799 – 95 (2005).(2009). DOI: 10.1520/B0799-95R09.10.1520/B0799-95R14.
For example see: Nobel, F. J., Ostrow, B. D., and Thompson, D. W., “Porosity Testing of Gold Deposits,” Plating, Vol 52, 1965, p. 1001.
Krumbien, S. J., “Porosity Testing of Contact Platings,” Proceedings, Connectors and Interconnection Technology Symposium, Oct. 1987, p 47.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’sstandard’s Document Summary page on the ASTM website.
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
B799 − 95 (2014)
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 contact properties, or which can be the source of corrosion products
or tarnish films that interfere with the function of the part.
3.2.3 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.
3.2.4 porosity, n—the presence of any discontinuity, crack, or hole in the coating that exposes a different underlying metal.
3.2.5 underplate, n—a metallic coating layer between the substrate and the topmost layer or layers. The thickness of an
underplate is usually greater that 0.8 μm (30 μin.).
4. Summary of Test Method
4.1 The test method employs concentrated sulfurous acid (H SO ), which emits sulfur dioxide (SO ) gas according to the
2 3 2
equilibrium reaction:
H SO 5 SO 1H O (1)
2 3 2 2
The procedure is similar to one first proposed by Lee and Ternowski.
4.2 Exposure periods may vary, depending upon the degree of porosity to be revealed. Reaction of the gas with a corrodable
base metal at pore sites produces reaction products that appear as discrete spots on the gold or palladium surface. Individual spots
are counted with the aid of a loupe or low-power stereo microscope.
4.3 This test method is suitable for coatings containing 95 % or more of gold or palladium on substrates of copper, nickel, and
their alloys which are commonly used in electrical contacts.
4.4 This porosity test involves corrosion reactions in which the products delineate defect sites in coatings. Since the chemistry
and properties of these products may not resemble those found in natural or service environments this test is not recommended
for prediction of the electrical performance of contacts unless correlation is first established with service experience.
5. 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 inlay or 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 Palladium coatings are sometimes specified as alternatives to gold on electrical contacts and similar electrical component
surfaces, both as electrodeposits and as inlay or clad metal. This test method is particularly suitable for determining porosity in
palladium coatings, since the reactive atmosphere that is used does not attack the palladium if the specified test conditions are
followed. In contrast, palladium coatings are attacked by nitric acid (HNO ) and other strong oxidizing agents, so that Test Method
B735 cannot be used for determining the porosity in such coatings.
5.3 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.
5.4 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.
5.5 The present test method is capable of detecting virtually all porosity or other defects that could participate in corrosion
reactions with the substrate or underplate. The test is rapid, simple, and inexpensive. In addition, it can be used on contacts having
complex geometry such as pin-socket contacts (although with deep recesses it is preferred that the contact structures be opened
to permit reaction of the sulfur dioxide with the interior significant surfaces).
Lee, F. and Ternowski, M., Proceedings Ninth International Conference on Electrical Contact Phenomena, Chicago, 1978, p. 215.
B799 − 95 (2014)
5.6 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 judgment. Thus, absence of porosity in the coating may be a requirement for some applications,
while a few pores in the contact zone may be acceptable for others.
5.7 This test is considered destructive in that it reveals the presence of porosity by contaminating the surface with corrosion
products and by undercutting the coating at pore sites or at the boundaries of the unplated areas. Any parts exposed to this test shall
not be placed in service.
5.8 This test is intended to be used for quantitative descriptions of porosity (such as number of pores per unit area or per contact)
only on coatings that have a pore density sufficiently low that the corrosion sites are well separated and can be readily resolved.
As a general guideline this can be achieved for pore densities up to about 100/cm . Above this value the tests are useful for the
qualitative detection and comparisons of porosity.
5.9 For these purposes, the measurement area
...
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