ASTM B679-98

Standard Specification for Electrodeposited Coatings of Palladium for Engineering Use

SCOPE
1.1 Purity -This specification covers requirements for electrodeposited palladium coatings containing at least 99.7 mass % of palladium metal.
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 hardness range of electrodeposited palladium compares favorably with the other electroplated noble metals and their alloys.  
1.3 The values stated in SI units are the preferred values. Values provided in parentheses are for information only.
1.4 The following hazards caveat pertains only to the test methods section of this specification: This standard does not purport to address all of the safety problems, 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: 09-Mar-1998
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: B08 - Metallic and Inorganic Coatings
• Drafting Committee: B08.04 - Precious Metal Coatings

Relations

• Replaced By: ASTM B679-98(2004)e1 - Standard Specification for Electrodeposited Coatings of Palladium for Engineering Use
• Effective Date: 01-Apr-2004
• Referred By: ASTM B984-12(2020)e1 - Standard Specification for Electrodeposited Coatings of Palladium-Cobalt Alloy for Engineering Use
• Effective Date: 10-Mar-1998
• 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: 10-Mar-1998
• Referred By: ASTM B866-95(2018) - Standard Test Method for Gross Defects and Mechanical Damage in Metallic Coatings by Polysulfide Immersion
• Effective Date: 10-Mar-1998

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: B 679 – 98
Standard Specification for
Electrodeposited Coatings of Palladium for Engineering
Use
This standard is issued under the fixed designation B 679; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope B 254 Practice for Preparation of and Electroplating on
Stainless Steel
1.1 This specification covers requirements for electrodepos-
B 281 Practice for Preparation of Copper and Copper-Base
ited palladium coatings containing at least 99.7 mass % of
Alloys for Electroplating and Conversion Coatings
palladium metal. Composite coatings consisting of palladium
B 322 Practice for Cleaning Metals Prior to Electroplating
with a thin gold overplate for applications involving electrical
B 374 Terminology Relating to Electroplating
contacts are also covered.
B 487 Test Method for Measurement of Metal and Oxide
1.2 Properties—Palladium is the lightest and least noble of
Coating Thickness by Microscopical Examination of a
the platinum group metals. It has a specific gravity of 12.0,
Cross Section
which is substantially less than gold (19.3) and platinum
B 488 Specification for Electrodeposited Coatings of Gold
(21.5). This yields a greater volume or thickness of coating
for Engineering Use
and, consequently, some saving of metal weight accompanied
B 489 Practice for Bend Test for Ductility of Electrodepos-
by a small sacrifice in corrosion resistance and reflectivity. The
ited and Autocatalytically Deposited Metal Coatings on
following table compares the hardness range of electrodepos-
Metals
ited palladium with other electrodeposited noble metals and
2 B 499 Test Method for Measurement of Coating Thick-
alloys (1,2).
nesses by the Magnetic Method: Nonmagnetic Coatings on
Approximate Hardness (HK )
Magnetic Basis Metals
Gold 50–250
Palladium 75–600
B 507 Practice for Design of Articles to Be Electroplated on
Platinum 150–550
Racks
Palladium-Nickel 300–650
B 542 Terminology Relating to Electrical Contacts and
Rhodium 750–1100
Ruthenium 600–1300
Their Use
B 558 Practice for Preparation of Nickel Alloys for Electro-
1.3 The values stated in SI units are the preferred values.
plating
Values provided in parentheses are for information only.
B 567 Test Method for Measurement of Coating Thickness
1.4 This standard does not purport to address all of the
by the Beta Backscatter Method
safety concerns, if any, associated with its use. It is the
B 568 Test Method for Measurement of Coating Thickness
responsibility of the user of this standard to establish appro-
by X-Ray Spectrometry
priate safety and health practices and determine the applica-
B 571 Test Methods for Adhesion of Metallic Coatings
bility of regulatory limitations prior to use.
B 602 Test Method for Attribute Sampling of Metallic and
2. Referenced Documents
Inorganic Coatings
B 689 Specification for Electroplated Engineering Nickel
2.1 The following standards form a part of this specification
Coatings
to the extent referenced herein:
B 697 Guide for Selection of Sampling Plans for Inspection
2.2 ASTM Standards:
of Electrodeposited Metallic and Inorganic Coatings
B 242 Practice for Preparation of High-Carbon Steel for
B 741 Test Methods for Porosity in Gold Coatings on Metal
Electroplating
Substrates by Paper Electrography
B 748 Test Method for Measurement of Thickness of Me-
tallic Coatings by Measurement of a Cross-Section with a
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
Scanning Electron Microscope
B08.08.02 on Precious Metal Coatings.
B 762 Method of Variables Sampling of Metallic and Inor-
Current edition approved March 10, 1998. Published November 1998. Last
ganic Coatings
previous edition B 679 – 80. Originally published as B 679 – 91.
The boldface numbers in parentheses refer to the list of references at the end of
this specification.
Annual Book of ASTM Standards, Vol 02.05.
Annual Book of ASTM Standards, Vol 03.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B679–98
A
TABLE 2 Gold Overplate
B 799 Test Method for Porosity in Gold and Palladium
Coatings by Sulfurous Acid/Sulfur-Dioxide Vapor Thickness
Grade Type MIL-G-45204 Hardness (Code)
Range
B 809 Test Method for Porosity in Metallic Coatings by
0 No Overplate . . . . . . . . .
Humid Sulfur Vapor (Flowers of Sulfur)
1 1 (99.9 % Au min) III 90 HK max (A) 0.05-0.12 μm
4 25
D 3951 Standard Practice for Commercial Packaging
2 2 (99.7 % Au min) I 130-200 HK (C) 0.05-0.25 μm
A
See Specification B 488 and Appendix X1
3. Terminology
3.1 Definitions—Many terms used in this specification are
defined in Terminology B 374 or B 542.
6.2.1 The surface condition of the basis metal should be
3.2 Definitions of Terms Specific to This Standard:
specified and should meet this specification prior to the plating
3.2.1 underplating—a metallic coating layer between the
of the parts.
basis metal or substrate and the topmost metallic coating. The
6.2.2 Defects in the surface of the basis metal, such as
thickness of an underplating is usually greater than 1 μm (40
scratches, porosity, pits, inclusions, roll and die marks, laps,
μin.), in contrast to a strike or flash.
cracks, burrs, cold shuts, and roughness may adversely affect
the appearance and performance of the deposit, despite the
4. Classification
observance of the best plating practice. Any such defects on
4.1 Orders for articles to be plated in accordance with this
significant surfaces should be brought to the attention of the
specification shall specify the plating system, indicating the
supplier and the purchaser.
basis metal, the thickness of the underplatings, the thickness of
6.2.3 Clean the basis metal as necessary to ensure a satis-
the palladium coating, and the grade of the gold overplating
factory surface for subsequent electroplating in accordance
according to Tables 1 and 2.
with Practices B 183, B 242, B 254, B 281, B 322, B 343,
B 481, B 482 and B 558.
5. Ordering Information
6.2.4 Proper preparatory procedures and thorough cleaning
5.1 In order to make the application of this standard
of the basis metal are essential for satisfactory adhesion and
complete, the purchaser needs to supply the following infor-
performance of these coatings. The surface must be chemically
mation to the seller in the purchase order or other governing
clean and continuously conductive, that is, without inclusions
document:
or other contaminants. The coatings must be smooth and as free
5.1.1 The name, designation, and date of issue of this
of scratches, gouges, nicks, and similar imperfections as
standard.
possible.
5.1.2 The coating system including basis metal, thickness
NOTE 1—A metal finisher can often remove defects through special
class and gold overplate grade (see 4.1 and Tables 1 and 2).
treatments such as grinding, polishing, abrasive blasting, chemical treat-
5.1.3 Presence, type, and thickness of underplating (see
ments, and electropolishing. However, these may not be normal in the
3.2.3).
treatment steps preceding the plating, and a special agreement is indicated.
5.1.4 Significant surfaces shall be defined (see 3.2.2).
6.3 Apply the coating after all basis metal preparatory
5.1.5 Requirements, if any, for porosity testing (see 9.5):
treatments and mechanical operations on significant surfaces
5.1.6 Requirement, if any, for bend ductility testing (see
have been completed.
9.6):
6.4 Racking:
5.1.7 Sampling plan employed (see Section 8), and
6.4.1 Position parts to allow free circulation of solution over
5.1.8 Requirement, if any, for surface coating cleanliness
all surfaces. The location of rack or wire marks in the coating
(absence of residual salts). See Appendix X3.
should be agreed upon between the producer and supplier.
6. Manufacture 6.5 Plating Process:
6.5.1 Nickel Underplating—Apply a nickel underplating
6.1 Any process that provides an electrodeposit capable of
before the palladium when the product is made from copper or
meeting the specified requirements will be acceptable.
copper alloy. Nickel underplatings are also applied for other
6.2 Substrate:
reasons. See Appendix X2.
NOTE 2—In certain instances where high frequency analog signals are
A
TABLE 1 Thickness Class
employed, such as wave guides, the magnetic properties of nickel may
Thickness Class Minimum Thickness of Pd (μm)
attenuate the signal. Palladium itself is non-ferromagnetic.
0.08 0.08
6.5.2 Strikes—Standard practice calls for a gold or palla-
0.15 0.15
0.25 0.25
dium strike to follow any underplate or substrate (other than
0.50 0.50
silver or platinum) immediately prior to applying the palla-
0.75 0.75
dium.
1.00 1.00
1.25 1.25
6.5.3 Plating—Good practice calls for the work to be
1.5 1.5
electrically connected when entering the bath. A minimum of
2.5 2.5
0.5 V is suggested. During electroplating it is extremely
3.0 3.0
5.0 5.0
important to maintain the voltage, current density, or both
A
See Appendix X4 for specific applications of the various thickness classes. beneath the value for hydrogen evolution. (See 7.2)
B679–98
6.5.4 Stress Cracking—Problems associated with the incor- 7.5.1 Gross Defects/Mechanical Damage—The coatings
poration of hydrogen in the palladium, which can lead to stress shall be free of visible mechanical damage and similar gross
cracking of the coating, shall be controlled by choosing plating defects when viewed at magnifications up to 103. For some
baths and plating conditions that minimize the H/Pd deposition applications this requirement may be relaxed to allow for a
ratio. (3) The presence of stress-induced microcracks that small number of such defects (per unit area), especially if they
penetrate to the underlying substrate or underplating can be are outside of or on the periphery of the significant surfaces.
detected with one of the porosity tests specified in 9.5. See 7.5.2 and 6.5.4.
6.5.5 Gold Overplating—Apply a thin gold overplating 7.5.2 Porosity—Almost all as-plated electrodeposits contain
after the palladium in any application in which palladium some porosity, and the amount of porosity to be expected for
plated electrical connectors are mated together in a contact any one type of coating will increase with decreasing the
pair. This process is necessary to preserve the performance of thickness of that particular coating type. The amount of
the contact surface. See Appendix X1 for other reasons for porosity in the coating that may be tolerable depends on the
using a gold overplate. severity of the environment that the article is likely to
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 applica-
particular article or coating requiring the porosity test. See 9.5.
tions, residual plating salts can be removed from the articles by
NOTE 5—Extensive reviews of porosity and porosity testing can be
a clean, hot (50 to 100°C) water rinse. A minimum rinse time
found in the literature (4, 5)
of 2.5 min (racks) or 5 min (barrel) is suggested. Best practice
calls for a minimum of three dragout rinses and one running
8. Sampling
rinse with dwell times of 40 s in each station when rack plating
8.1 The sampling plan used for the inspection of a quality of
and 80 s when barrel plating. Modern high-velocity impinge-
the coated articles shall be as agreed upon between the
ment type rinses can reduce this time to a few seconds. This is
purchaser and the supplier.
particularly useful in automatic reel-to-reel applications where
dwell times are significantly reduced. See Appendix X3.
NOTE 6—Usually, when a collection of coated articles, the inspection
lot (see 8.2), is examined for compliance with the requirements placed on
the articles, a relatively small number of the articles—the sample—is
7. Coating Requirements
selected at random and is inspected. The inspection lot is then classified as
7.1 Nature of Coating—The palladium deposit shall have
complying or not complying with the requirements based on the results of
minimum purity of 99.7 mass %.
the inspection of the sample. The size of the sample and the criteria of
7.2 Appearance—Palladium coatings shall be coherent, compliance are determined by the application of statistics. The procedure
is known as sampling inspection. Test Method B 602, Guide B 697, and
continuous, and have a uniform appearance to the extent that
Method B 762 contain sampling plans that are designed for the sampling
the nature of the basis metal and good commercial practices
inspection of coatings.
permit.
Test Method B 602 contains four sampling plans, three for use with tests
7.3 Thickness—Everywhere on the significant surface (see
that are non-destructive and one when they are destructive. The buyer and
5.1.4), the thickness of the palladium coating shall be equal to
seller may agree on the plan or plans to be used. If they do not, Test
or exceed the specified thickness. The maximum thickness, Method B 602 identifies the plan to be used.
Guide B 697 provides a large number of plans and also gives guidance
however, shall not exceed the drawing tolerance.
in the selection of a plan. When Guide B 697 is specified, the buyer and
NOTE 4—The coating thickness requirement of this specification is a
seller need to agree on the plan to be used.
minimum requirement; that is, the coating thickness is required to equal or
Method B 762 can be used only for coating requirements that have a
exceed the specified thickness everywhere on the significant surfaces
numerical limit, such as coating thickness. The test must yield a numerical
while conforming to all maximum thickness tolerances given in the
value and certain statistical requirements must be met. Method B 762
engineering drawing. Variation in the coating thickness from point to point
contains several plans and also gives instructions for calculating plans to
on a coated article is an inherent characteristic of electroplating processes.
meet special needs. The buyer and the seller may agree on the plan or
Therefore, the coating thickness will
...