ASTM B679-98(2009)

Standard Specification for Electrodeposited Coatings of Palladium for Engineering Use

ABSTRACT
This specification establishes the requirements for electrodeposited palladium coatings for use in engineering applications. This specification also covers composite coatings of palladium with a thin gold overplate for applications involving electrical contacts. The plating system shall indicate the basis metal involved, thickness of the underplates, thickness of the palladium coating, and grade of the gold overplate. Coatings shall be sampled, tested, and conform accordingly to specified requirements as to purity, appearance, thickness, dutility, adhesion (to be examined either by bend, heat, or cutting test), and integrity (gross defects, mechanical damage, and porosity).
SCOPE
1.1 This specification covers requirements for electrodeposited palladium coatings containing at least 99.7 mass % of palladium metal. Composite coatings consisting of palladium with a thin gold overplate for applications involving electrical contacts are also covered.
1.2 Properties—Palladium is the lightest and least noble of the platinum group metals. It has a specific gravity of 12.0, which is substantially less than gold (19.3) and platinum (21.5). This yields a greater volume or thickness of coating and, consequently, some saving of metal weight accompanied by a small sacrifice in corrosion resistance and reflectivity. The following table compares the hardness range of electrodeposited palladium with other electrodeposited noble metals and alloys (1,2).
  Approximate Hardness (HK25) Gold50–250 Palladium75–600 Platinum150–550 Palladium-Nickel300–650 Rhodium750–1100 Ruthenium600–1300
1.3 The values stated in SI units are the preferred values. Values provided in parentheses are for information only.
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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Aug-2009
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.04 - Precious Metal Coatings

Relations

• Replaces: ASTM B679-98(2004)e1 - Standard Specification for Electrodeposited Coatings of Palladium for Engineering Use
• Effective Date: 01-Sep-2009
• Referred By: ASTM B866-95(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
• Effective Date: 01-Sep-2009
• Referred By: ASTM B877-96(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by the Phosphomolybdic Acid (PMA) Method
• Effective Date: 01-Sep-2009
• Referred By: ASTM B984-12(2020)e1 - Standard Specification for Electrodeposited Coatings of Palladium-Cobalt Alloy for Engineering Use
• Effective Date: 01-Sep-2009

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:B679 −98(Reapproved2009)
Standard Specification for
Electrodeposited Coatings of Palladium for Engineering
Use
This standard is issued under the fixed designation B679; 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 Thisspecificationcoversrequirementsforelectrodepos- 2.1 Thefollowingstandardsformapartofthisspecification
ited palladium coatings containing at least 99.7 mass % of to the extent referenced herein:
palladium metal. Composite coatings consisting of palladium 3
2.2 ASTM Standards:
with a thin gold overplate for applications involving electrical
B183Practice for Preparation of Low-Carbon Steel for
contacts are also covered.
Electroplating
1.2 Properties—Palladium is the lightest and least noble of B242Guide for Preparation of High-Carbon Steel for Elec-
the platinum group metals. It has a specific gravity of 12.0, troplating
which is substantially less than gold (19.3) and platinum B254Practice for Preparation of and Electroplating on
(21.5). This yields a greater volume or thickness of coating Stainless Steel
and, consequently, some saving of metal weight accompanied B281Practice for Preparation of Copper and Copper-Base
byasmallsacrificeincorrosionresistanceandreflectivity.The Alloys for Electroplating and Conversion Coatings
following table compares the hardness range of electrodepos- B322Guide for Cleaning Metals Prior to Electroplating
ited palladium with other electrodeposited noble metals and B343Practice for Preparation of Nickel for Electroplating
alloys (1,2). with Nickel
B374Terminology Relating to Electroplating
Approximate Hardness (HK )
Gold 50–250
B481Practice for Preparation of Titanium and Titanium
Palladium 75–600
Alloys for Electroplating
Platinum 150–550
B482Practice for Preparation of Tungsten and Tungsten
Palladium-Nickel 300–650
Rhodium 750–1100
Alloys for Electroplating
Ruthenium 600–1300
B487Test Method for Measurement of Metal and Oxide
1.3 The values stated in SI units are the preferred values.
Coating Thickness by Microscopical Examination of
Values provided in parentheses are for information only.
Cross Section
B488Specification for Electrodeposited Coatings of Gold
1.4 This standard does not purport to address all of the
for Engineering Uses
safety concerns, if any, associated with its use. It is the
B489Practice for Bend Test for Ductility of Electrodepos-
responsibility of the user of this standard to establish appro-
ited and Autocatalytically Deposited Metal Coatings on
priate safety and health practices and determine the applica-
Metals
bility of regulatory limitations prior to use.
B499Test Method for Measurement of CoatingThicknesses
by the Magnetic Method: Nonmagnetic Coatings on
This specification is under the jurisdiction of ASTM Committee B08 on
Magnetic Basis Metals
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.04 on Precious Metal Coatings.
Current edition approved Sept. 1, 2009. Published November 2009. Originally
ε1 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
approved in 1980. Last previous edition approved in 2004 as B679–98(2004) .
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
DOI: 10.1520/B0679-98R09.
Standards volume information, refer to the standard’s Document Summary page on
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
the ASTM website.
this specification.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B679−98(2009)
A
TABLE 1 Thickness Class
B507Practice for Design ofArticles to Be Electroplated on
Thickness Class Minimum Thickness of Pd (µm)
Racks
0.08 0.08
B542Terminology Relating to Electrical Contacts andTheir
0.15 0.15
Use
0.25 0.25
B558Practice for Preparation of Nickel Alloys for Electro-
0.50 0.50
0.75 0.75
plating
1.00 1.00
B567Test Method for Measurement of Coating Thickness
1.25 1.25
by the Beta Backscatter Method
1.5 1.5
2.5 2.5
B568Test Method for Measurement of Coating Thickness
3.0 3.0
by X-Ray Spectrometry
5.0 5.0
B571Practice for Qualitative Adhesion Testing of Metallic
A
See Appendix X4 for specific applications of the various thickness classes.
Coatings
B602Test Method for Attribute Sampling of Metallic and
A
Inorganic Coatings
TABLE 2 Gold Overplate
B689Specification for Electroplated Engineering Nickel
Thickness
Grade Type MIL-G-45204 Hardness (Code)
Coatings Range
0 No Overplate . . . . . . . . .
B697Guide for Selection of Sampling Plans for Inspection
1 1 (99.9 % Au min) III 90 HK max (A) 0.05-0.12 µm
of Electrodeposited Metallic and Inorganic Coatings
2 2 (99.7 % Au min) I 130-200 HK (C) 0.05-0.25 µm
B741Test Method for Porosity In Gold Coatings On Metal
A
See Specification B488 and Appendix X1.
Substrates By Paper Electrography (Withdrawn 2005)
B748Test Method for Measurement of Thickness of Metal-
lic Coatings by Measurement of Cross Section with a
Scanning Electron Microscope
5.1.1 The name, designation, and date of issue of this
B762Test Method of Variables Sampling of Metallic and
standard.
Inorganic Coatings
5.1.2 The coating system including basis metal, thickness
B765GuideforSelectionofPorosityandGrossDefectTests
class and gold overplate grade (see 4.1 and Tables 1 and 2).
for Electrodeposits and Related Metallic Coatings
5.1.3 Presence, type, and thickness of underplating (see
B799Test Method for Porosity in Gold and Palladium
3.2.1).
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor
5.1.4 Significant surfaces shall be defined (see 3.1).
B809Test Method for Porosity in Metallic Coatings by
5.1.5 Requirements, if any, for porosity testing (see 9.5):
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
5.1.6 Requirement, if any, for bend ductility testing (see
D1125Test Methods for Electrical Conductivity and Resis-
9.6):
tivity of Water
5.1.7 Sampling plan employed (see Section 8), and
D3951Practice for Commercial Packaging
5.1.8 Requirement, if any, for surface coating cleanliness
(absence of residual salts). See Appendix X3.
3. Terminology
3.1 Definitions—Many terms used in this specification are
6. Manufacture
defined in Terminology B374 or B542.
6.1 Any process that provides an electrodeposit capable of
3.2 Definitions of Terms Specific to This Standard:
meeting the specified requirements will be acceptable.
3.2.1 underplating—a metallic coating layer between the
6.2 Substrate:
basis metal or substrate and the topmost metallic coating. The
6.2.1 The surface condition of the basis metal should be
thickness of an underplating is usually greater than 1 µm (40
specified and should meet this specification prior to the plating
µin.), in contrast to a strike or flash.
of the parts.
4. Classification 6.2.2 Defects in the surface of the basis metal, such as
scratches, porosity, pits, inclusions, roll and die marks, laps,
4.1 Orders for articles to be plated in accordance with this
cracks, burrs, cold shuts, and roughness may adversely affect
specification shall specify the plating system, indicating the
the appearance and performance of the deposit, despite the
basismetal,thethicknessoftheunderplatings,thethicknessof
observance of the best plating practice. Any such defects on
the palladium coating, and the grade of the gold overplating
significant surfaces should be brought to the attention of the
according to Tables 1 and 2.
supplier and the purchaser.
5. Ordering Information
6.2.3 Clean the basis metal as necessary to ensure a satis-
factory surface for subsequent electroplating in accordance
5.1 In order to make the application of this standard
with Practices B183, B254, B281, B322, B343, B481, B482,
complete, the purchaser needs to supply the following infor-
and B558, and Guide B242.
mation to the seller in the purchase order or other governing
6.2.4 Proper preparatory procedures and thorough cleaning
document:
of the basis metal are essential for satisfactory adhesion and
performanceofthesecoatings.Thesurfacemustbechemically
The last approved version of this historical standard is referenced on
www.astm.org. clean and continuously conductive, that is, without inclusions
B679−98(2009)
orothercontaminants.Thecoatingsmustbesmoothandasfree 7. Coating Requirements
of scratches, gouges, nicks, and similar imperfections as
7.1 Nature of Coating—The palladium deposit shall have
possible.
minimum purity of 99.7 mass %.
NOTE 1—A metal finisher can often remove defects through special
7.2 Appearance—Palladium coatings shall be coherent,
treatments such as grinding, polishing, abrasive blasting, chemical
continuous, and have a uniform appearance to the extent that
treatments,andelectropolishing.However,thesemaynotbenormalinthe
the nature of the basis metal and good commercial practices
treatmentstepsprecedingtheplating,andaspecialagreementisindicated.
permit.
6.3 Apply the coating after all basis metal preparatory
treatments and mechanical operations on significant surfaces
7.3 Thickness—Everywhere on the significant surface (see
have been completed. 5.1.4), the thickness of the palladium coating shall be equal to
or exceed the specified thickness. The maximum thickness,
6.4 Racking:
however, shall not exceed the drawing tolerance.
6.4.1 Positionpartstoallowfreecirculationofsolutionover
all surfaces. The location of rack or wire marks in the coating
NOTE 4—The coating thickness requirement of this specification is a
should be agreed upon between the producer and supplier. minimumrequirement;thatis,thecoatingthicknessisrequiredtoequalor
exceed the specified thickness everywhere on the significant surfaces
6.5 Plating Process:
while conforming to all maximum thickness tolerances given in the
6.5.1 Nickel Underplating—Apply a nickel underplating
engineeringdrawing.Variationinthecoatingthicknessfrompointtopoint
before the palladium when the product is made from copper or
onacoatedarticleisaninherentcharacteristicofelectroplatingprocesses.
Therefore, the coating thickness will have to exceed the specified value at
copper alloy. Nickel underplatings are also applied for other
some points on the significant surfaces to ensure that the thickness equals
reasons. See Appendix X2.
or exceeds the specified value at all points. Hence, in most cases, the
NOTE 2—In certain instances where high frequency analog signals are
average coating thickness on an article will be greater than the specified
employed, such as wave guides, the magnetic properties of nickel may value; how much greater is largely determined by the shape of the article
attenuate the signal. Palladium itself is non-ferromagnetic.
(see Practice B507) and the characteristics of the plating process.
In addition, the average coating thickness on articles will vary from
6.5.2 Strikes—Standard practice calls for a gold or palla-
article to article within a production lot. Therefore, if all of the articles in
dium strike to follow any underplate or substrate (other than
aproductionlotaretomeetthethicknessrequirement,theaveragecoating
silver or platinum) immediately prior to applying the palla-
thicknessfortheproductionlotasawholewillbegreaterthantheaverage
dium. necessary to assure that a single article meets the requirement.
6.5.3 Plating—Good practice calls for the work to be
7.4 Adhesion—The palladium coatings shall be adherent to
electrically connected when entering the bath. A minimum of
the substrate, when tested by one of the procedures summa-
0.5 V is suggested. During electroplating it is extremely
rized in 9.4.
important to maintain the voltage, current density, or both
7.5 Integrity of the Coating:
beneath the value for hydrogen evolution. (See 7.2)
7.5.1 Gross Defects/Mechanical Damage—The coatings
6.5.4 Stress Cracking—Problems associated with the incor-
shall be free of visible mechanical damage and similar gross
porationofhydrogeninthepalladium,whichcanleadtostress
defects when viewed at magnifications up to 10×. For some
crackingofthecoating,shallbecontrolledbychoosingplating
applications this requirement may be relaxed to allow for a
bathsandplatingconditionsthatminimizetheH/Pddeposition
small number of such defects (per unit area), especially if they
ratio (3) . The presence of stress-induced microcracks that
are outside of or on the periphery of the significant surfaces.
penetrate to the underlying substrate or underplating can be
See 7.5.2 and 6.5.4.
detected with one of the porosity tests specified in 9.5.
7.5.2 Porosity—Almostallas-platedelectrodepositscontain
6.5.5 Gold Overplating—Applyathingoldoverplatingafter
some porosity, and the amount of porosity to be expected for
the palladium in any application in which palladium plated
any one type of coating will increase with decreasing the
electrical connectors are mated together in a contact pair. This
thickness of that particular coating type. The amount of
processisnecessarytopreservetheperformanceofthecontact
porosity in the coating that may be tolerable depends on the
surface. See Appendix X1 for other reasons for using a gold
severity of the environment that the article is likely to
overplate.
encounter during service or storage. If the pores are few in
NOTE 3—When using Type 1 gold, the thickness of the gold overplate
number, or away from the significant surfaces, their presence
shall not exceed 0.12 µm (5 µin.) due to increased risk of degrading
can often be tolerated. Acceptance or pass-fail criteria, if
durability and increasing the coefficient of friction.
required, shall be part of the product specification for the
6.5.6 Residual Salts—For rack and barrel plating
particulararticleorcoatingrequiringtheporositytest.See9.5.
applications, residual plating salts can be removed from the
NOTE 5—Extensive reviews of porosity and porosity testing can be
articles by a clean, hot (50 to 100°C) water rinse.Aminimum
found in the literature (4, 5).
rinse time of 2.5 min (racks) or 5 min (barrel) is suggested.
Best practice calls for a minimum of three dragout rinses and
8. Sampling
onerunningrinsewithdwelltimesof40sineachstationwhen
8.1 Thesamplingplanusedfortheinspectionofaqualityof
rack plating and 80 s when barrel plating. Modern high-
the coated articles shall be as agreed upon between the
velocity impingement type rinses can reduce this time to a few
purchaser and the supplier.
seconds. This is particularly useful in automatic reel-to-reel
applications where dwell times are significantly reduced. See
NOTE 6—Usually, when a collection of coated articles, the inspection
Appendix X3. lot (see
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