ASTM B984-12(2020)e1
(Specification)Standard Specification for Electrodeposited Coatings of Palladium-Cobalt Alloy for Engineering Use
Standard Specification for Electrodeposited Coatings of Palladium-Cobalt Alloy for Engineering Use
ABSTRACT
This specification covers requirements for electrodeposited palladium-cobalt alloy coatings containing approximately 80% of palladium and 20% of cobalt. It also covers composite coatings consisting of palladium-cobalt with a thin gold overplate for applications involving electrical contacts. Palladium and palladium-cobalt remain competitive finishes for high reliability applications. The specification deals with material classification, ordering information, materials and manufacture, coating requirements, sampling, test methods, special government requirements, and other requirements.
SCOPE
1.1 This specification covers requirements for electrodeposited palladium-cobalt alloy coatings containing approximately 80 % of palladium and 20 % of cobalt. Composite coatings consisting of palladium-cobalt with a thin gold overplate for applications involving electrical contacts are also covered. Palladium and palladium-cobalt remain competitive finishes for high reliability applications.
1.2 Properties—Palladium is the lightest and least noble of the platinum group metals (1)2. It has the density of 12 gm per cubic centimeter, specific gravity of 12.0, that is substantially lower than the density of gold, 19.29 gm per cubic centimeter, specific gravity 19.3, and platinum 21.48 gm per cubic centimeter, specific gravity 21.5. The density of cobalt on the other hand is even less than palladium. It is only 8.69 gm per cubic centimeter, specific gravity 8.7. This yields a greater volume or thickness of coating and, consequently, some saving of metal weight and reduced cost. Palladium-cobalt coated surfaces provide a hard surface finish (Test Methods E18), thus decreasing wear and increasing durability. Palladium-cobalt coated surfaces also have a very low coefficient of friction 0.43 compared to hard gold 0.60, thus providing lower mating and unmating forces for electrical contacts (1). Palladium-cobalt has smaller grain size (Test Methods E112), 50 – 150 Angstroms, compared to Hard Gold 200 – 250 Angstroms (1), or 5 – 15 nanometer, compared to hard gold 20 – 25 nanometer (1). Palladium-cobalt has low porosity (Test Method B799) 0.2 porosity index compared to hard gold 3.7 porosity index (1). Palladium-cobalt coated surfaces have high ductility (Practice B489) 3-7 % compared to that of hard gold 1). The palladium-cobalt coated surface is also thermally more stable 395 °C than hard gold 150 °C, and silver 170 °C. The following Table 1 compares the hardness range of electrodeposited palladium-cobalt with other electrodeposited noble metals and alloys (2, 3).
1.3 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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
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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.
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Designation:B984 −12 (Reapproved 2020)
Standard Specification for
Electrodeposited Coatings of Palladium-Cobalt Alloy for
Engineering Use
This standard is issued under the fixed designation B984; 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.
ε NOTE—Editorial changes were made throughout in June 2020.
1. Scope ing Table 1 compares the hardness range of electrodeposited
palladium-cobalt with other electrodeposited noble metals and
1.1 Thisspecificationcoversrequirementsforelectrodepos-
alloys (2, 3).
ited palladium-cobalt alloy coatings containing approximately
TABLE 1 - Hardness of Noble Metals
80% of palladium and 20% of cobalt. Composite coatings
Approximate Hardness (HK )
consisting of palladium-cobalt with a thin gold overplate for
Gold 50–250
applications involving electrical contacts are also covered.
Palladium 75–600
Platinum 150–550
Palladium and palladium-cobalt remain competitive finishes
Palladium-Nickel 300–650
for high reliability applications.
Palladium-Cobalt 500–650
Rhodium 750–1100
1.2 Properties—Palladium is the lightest and least noble of
Ruthenium 600–1300
the platinum group metals (1) . It has the density of 12 gm per
1.3 Units—The values stated in SI units are to be regarded
cubic centimeter, specific gravity of 12.0, that is substantially
asstandard.Nootherunitsofmeasurementareincludedinthis
lower than the density of gold, 19.29 gm per cubic centimeter,
standard.
specific gravity 19.3, and platinum 21.48 gm per cubic
centimeter, specific gravity 21.5. The density of cobalt on the 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
other hand is even less than palladium. It is only 8.69 gm per
cubic centimeter, specific gravity 8.7. This yields a greater responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
volumeorthicknessofcoatingand,consequently,somesaving
of metal weight and reduced cost. Palladium-cobalt coated mine the applicability of regulatory limitations prior to use.
surfacesprovideahardsurfacefinish(TestMethodsE18),thus 1.5 This international standard was developed in accor-
decreasing wear and increasing durability. Palladium-cobalt dance with internationally recognized principles on standard-
coatedsurfacesalsohaveaverylowcoefficientoffriction0.43 ization established in the Decision on Principles for the
compared to hard gold 0.60, thus providing lower mating and Development of International Standards, Guides and Recom-
unmating forces for electrical contacts (1). Palladium-cobalt mendations issued by the World Trade Organization Technical
has smaller grain size (Test Methods E112), 50 – 150 Barriers to Trade (TBT) Committee.
Angstroms, compared to Hard Gold 200 – 250Angstroms (1),
2. Referenced Documents
or5–15nanometer,comparedtohardgold20–25nanometer
(1).Palladium-cobalthaslowporosity(TestMethodB799)0.2
2.1 ASTM Standards:
porosity index compared to hard gold 3.7 porosity index (1).
B183Practice for Preparation of Low-Carbon Steel for
Palladium-cobalt coated surfaces have high ductility (Practice
Electroplating
B489) 3-7% compared to that of hard gold <3% (1). The
B242Guide for Preparation of High-Carbon Steel for Elec-
palladium-cobalt coated surface is also thermally more stable
troplating
395°C than hard gold 150°C, and silver 170°C. The follow-
B254Practice for Preparation of and Electroplating on
Stainless Steel
B281Practice for Preparation of Copper and Copper-Base
This specification is under the jurisdiction of ASTM Committee B08 on
Alloys for Electroplating and Conversion Coatings
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.04 on Precious Metal Coatings.
Current edition approved May 1, 2020. Published June 2020. Originally
approved in 2012. Last previous edition approved in 2012 as B984–12. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/B0984-12R20E01. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this specification. theASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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B984−12 (2020)
B322Guide for Cleaning Metals Prior to Electroplating E18Test Methods for Rockwell Hardness of Metallic Ma-
B343Practice for Preparation of Nickel for Electroplating terials
with Nickel E112Test Methods for Determining Average Grain Size
B374Terminology Relating to Electroplating
3. Terminology
B481Practice for Preparation of Titanium and Titanium
Alloys for Electroplating
3.1 Definitions—Many terms used in this specification are
B482Practice for Preparation of Tungsten and Tungsten
defined in Terminology B374 or B542.
Alloys for Electroplating
3.2 Definitions of Terms Specific to This Standard:
B487Test Method for Measurement of Metal and Oxide
3.2.1 significant surfaces, n—defined as those normally
Coating Thickness by Microscopical Examination of
visible(directlyorbyreflector)oressentialtotheserviceability
Cross Section
or function of the article. Can be the source of corrosion
B488Specification for Electrodeposited Coatings of Gold
products or tarnish films that interfere with the function or
for Engineering Uses
desirable appearance of the article. The significant surfaces
B489Practice for Bend Test for Ductility of Electrodepos-
shall be indicated on the drawings of the parts or by the
ited and Autocatalytically Deposited Metal Coatings on
provision of suitable marked samples.
Metals
3.2.2 underplating, n—a metallic coating layer between the
B499Test Method for Measurement of CoatingThicknesses
basis metal or substrate and the topmost metallic coating. The
by the Magnetic Method: Nonmagnetic Coatings on
thicknessofunderplatingisusuallygreaterthan1µm.Forhigh
Magnetic Basis Metals
energy electrical contact, the thickness may be 2.0 – 4.0 µm.
B507Practice for Design ofArticles to Be Electroplated on
Racks
4. Classification
B542Terminology Relating to Electrical Contacts andTheir
Use
4.1 Orders for articles to be plated in accordance with this
B558Practice for Preparation of Nickel Alloys for Electro-
specification shall specify the plating system, indicating the
plating
basismetal,thethicknessoftheunderplatings,thethicknessof
B567Test Method for Measurement of Coating Thickness
the palladium-cobalt coating, and the grade of the gold
by the Beta Backscatter Method
overplating according to Table 2 and Table 3.
B568Test Method for Measurement of Coating Thickness
5. Ordering Information
by X-Ray Spectrometry
B571Practice for Qualitative Adhesion Testing of Metallic
5.1 In order to make the application of this standard
Coatings
complete, the purchaser needs to supply the following infor-
B602Test Method for Attribute Sampling of Metallic and
mation to the seller in the purchase order or other governing
Inorganic Coatings
document:
B679Specification for Electrodeposited Coatings of Palla-
5.1.1 The name, designation, and date of issue of this
dium for Engineering Use
standard.
B689Specification for Electroplated Engineering Nickel
5.1.2 The coating system including basis metal, thickness
Coatings
class and gold overplate grade (see 4.1 and Tables 1-3).
B697Guide for Selection of Sampling Plans for Inspection
5.1.3 Presence, type, and thickness of underplating (see
of Electrodeposited Metallic and Inorganic Coatings
3.2.2).
B741Test Method for Porosity In Gold Coatings On Metal
5.1.4 Significant surfaces shall be defined (see 3.2.1).
Substrates By Paper Electrography (Withdrawn 2005)
5.1.5 Requirements, if any, for porosity testing (see 9.5);
B748Test Method for Measurement of Thickness of Metal-
5.1.6 Requirement, if any, for bend ductility testing (see
lic Coatings by Measurement of Cross Section with a
9.6);
Scanning Electron Microscope
5.1.7 Sampling plan employed (see Section 8), and
B762Test Method of Variables Sampling of Metallic and
Inorganic Coatings
B765GuideforSelectionofPorosityandGrossDefectTests
A
TABLE 2 Thickness Class
for Electrodeposits and Related Metallic Coatings
Thickness Class Minimum Thickness of Pd-Co (µm)
B799Test Method for Porosity in Gold and Palladium
0.08 0.08
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
0.15 0.15
B809Test Method for Porosity in Metallic Coatings by 0.25 0.25
0.50 0.50
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
0.75 0.75
D1125Test Methods for Electrical Conductivity and Resis-
1.00 1.00
tivity of Water
1.25 1.25
1.5 1.5
D3951Practice for Commercial Packaging
2.5 2.5
3.0 3.0
5.0 5.0
A
The last approved version of this historical standard is referenced on
See X4.1 for specific applications of the various thickness classes.
www.astm.org.
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B984−12 (2020)
A
TABLE 3 Gold Overplate
6.5.2 Palladium-Cobalt Overplating—The electrodeposi-
Grade Type MIL-G- Hardness Thickness
tion process produces mechanically stable Pd-Co films at
45204 (Code) Range 2
currentdensitiesfromlessthan50mA/cm togreaterthan700
1 1 (99.9 % III 90 HK 0.05-0.12
mA/cm . It can produce alloys of 10 to 30 percent Cobalt
Au min) max (A) µm
content.Any desired composition (for example, 20% Co) can
2 2 (99.7 % I 130-200 0.05-0.25
Au min) HK (C) µm
be maintained within 65 percent over a wide range of
A
See Specification B488 and Appendix X1. operating conditions and bath aging.
6.5.3 Plating—Good practice calls for the work to be
electrically connected when entering the bath. A minimum of
0.5 V is suggested. During electroplating it is extremely
important to maintain the voltage, current density, or both
5.1.8 Requirement, if any, for surface coating cleanliness
beneath the value for hydrogen evolution, if possible.
(absence of residual salts). See Appendix X3.
6.5.4 Stress Cracking—Problems associated with the incor-
poration of hydrogen in the palladium-cobalt, which can lead
6. Materials and Manufacture
to stress cracking of the coating, shall be controlled by
6.1 Any process that provides an electrodeposit capable of
choosingplatingbathsandplatingconditionsthatminimizethe
meeting the specified requirements will be acceptable.
H/Pd-Co deposition ratio. The presence of stress-induced
6.2 Substrate: microcracks that penetrate to the underlying substrate or
6.2.1 The surface condition of the basis metal should be underplating can be detected with one of the porosity tests
specifiedandshouldmeetthisspecificationpriortotheplating specified in 9.5.
of the parts. 6.5.5 Gold Overplating—A thin gold overplating after the
6.2.2 Defects in the surface of the basis metal, such as palladium-cobaltcanbeappliedinanapplicationinwhichgold
scratches, porosity, pits, inclusions, roll and die marks, laps, plated electrical connectors are mated together in a contact
cracks, burrs, cold shuts, and roughness may adversely affect pair. This process is necessary to preserve the performance of
the appearance and performance of the deposit, despite the
the contact surface. See Appendix X1 for other reasons for
observance of the best plating practice. Any such defects on using a gold overplate.
significant surfaces should be brought to the attention of the
6.5.6 Residual Salts—For rack and barrel plating
supplier and the purchaser (See Note 1). applications, residual plating salts can be removed from the
6.2.3 Proper preparatory procedures and thorough cleaning
articles by a clean, hot (50 to 100°C) water rinse.Aminimum
of the basis metal are essential for satisfactory adhesion and rinse time of 2.5 min (racks) or 5 min (barrel) is suggested.
performanceofthesecoatings.Thesurfacemustbechemically
Best practice calls for a minimum of three dragout rinses and
clean and continuously conductive, that is, without inclusions onerunningrinsewithdwelltimesof40sineachstationwhen
orothercontaminants.Thecoatingsmustbesmoothandasfree
rack plating and 80 s when barrel plating. Modern high-
of scratches, gouges, nicks, and similar imperfections as velocity impingement type rinses can reduce this time to a few
possible. seconds. This is particularly useful in automatic reel-to-reel
6.2.4 The base materials are to be cleaned and prepared as applications where dwell times are significantly reduced. See
necessary to ensure good Pd-Co plating. The base material Appendix X3.
preparationmaybeaccomplishedinaccordancewithPractices
7. Coating Requirements
B183, B254, B281, B322, B343, B481, B482, and B558, and
Guide B242.
7.1 Coating Composition—The preferred palladium-cobalt
alloy composition should be 80% palladium and 20% cobalt;
NOTE 1—A metal finisher can often remove defects through special
however the palladium (Specification B679) content should
treatments such as grinding, polishing, abrasive blasting, chemical
treatments,andelectropolishing.However,thesemaynotbenormalinthe never be less than 70% and the cobalt should never be more
treatmentstepsprecedingtheplating,andaspecialagreementisindicated.
than 30%.
6.3 Apply the coating after all basis metal preparatory
7.2 Appearance—Palladium-cobalt coatings shall be
treatments and mechanical operations on significant surfaces
smooth,uniformandcontinuousinappearancewithnocracks,
have been completed.
pits,nodules,blisters,roughness,excessiveedgebuildup,areas
of no plating, burned deposits or any other unwanted visible
6.4 Racking:
plating irregularity. The examination should be done with the
6.4.1 Positionpartstoallowfreecirculationofsolutionover
unaided eye and under 10X magnification.
allsurfaces(PracticeB507).Thelocationofrackorwiremarks
in the coating should be agreed upon between the purchaser
7.3 Thickness—Everywhere on the significant surface (see
and supplier.
5.1.4), the thickness of the palladium coating shall be equal to
or exceed the specified thickness. The maximum thickness,
6.5 Plating Process:
however, shall not exceed the drawing tolerance (see Note 3
6.5.1 Nickel Underplating—Thenickelunderplating(Speci-
and Note 2).
fication B689) must be applied before the palladium-cobalt
alloy plating when the product is made from copper or copper
NOTE 2—The coating thickness requirement of this specification is a
alloy. Nickel underplatings are also applied for other reasons.
minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
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