ASTM B700-97(2002)
(Specification)Standard Specification for Electrodeposited Coatings of Silver for Engineering Use
Standard Specification for Electrodeposited Coatings of Silver for Engineering Use
SCOPE
1.1 This specification covers requirements for electrodeposited coatings of silver used for engineering purposes that may be mat, bright, or semibright and are not less than 98% silver purity.
1.2 Coatings of silver covered by this specification are usually employed for solderable surfaces, electrical contact characteristics, high electrical and thermal conductivity, thermocompression bonding, wear resistance of load-bearing surfaces, and special reflectivity.
1.3 In the Appendixes important characteristics of electrodeposited silver coatings are briefly described which must be considered when used in engineering applications, namely electrical conductivity (see Appendix X1), silver migration (see Appendix X2), thickness (see Appendix X3), hardness (see Appendix X4), and atmospheric tarnish (see Appendix X5).
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 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.
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Designation: B 700 – 97 (Reapproved 2002)
Standard Specification for
Electrodeposited Coatings of Silver for Engineering Use
This standard is issued under the fixed designation B 700; 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 343 Practice for Preparation of Nickel for Electroplating
with Nickel
1.1 This specification covers requirements for electrodepos-
B 374 Terminology Relating to Electroplating
ited coatings of silver used for engineering purposes that may
B 481 Practice for Preparation of Titanium and Titanium
be mat, bright, or semibright and are not less than 98 % silver
Alloys for Electroplating
purity.
B 482 Practice for Preparation of Tungsten and Tungsten
1.2 Coatings of silver covered by this specification are
Alloys for Electroplating
usually employed for solderable surfaces, electrical contact
B 487 Test Method for Measurement of Metal and Oxide
characteristics, high electrical and thermal conductivity, ther-
Coating Thicknesses by Microscopical Examination of a
mocompression bonding, wear resistance of load-bearing sur-
Cross Section
faces, and spectral reflectivity.
B 499 Test Method for Measurement of Coating Thick-
1.3 In the Appendixes important characteristics of elec-
nessesbytheMagneticMethod:NonmagneticCoatingson
trodeposited silver coatings are briefly described which must
Magnetic Basis Metals
be considered when used in engineering applications, namely
B 504 Test Method for Measurement of Thickness of Me-
electrical conductivity (see Appendix X1), silver migration
tallic Coatings by the Coulometric Method
(seeAppendixX2),thickness(seeAppendixX3),hardness(see
B 507 Practice for Design ofArticles to be Electroplated on
Appendix X4), and atmospheric tarnish (see Appendix X5).
Racks
1.4 The following hazards caveat pertains only to the test
B 542 Terminology Relating to Electrical Contacts and
methods section of this specification: This standard does not
Their Use
purport to address the safety concerns, if any, associated with
B 567 Test Method for Measurement of Coating Thickness
its use. It is the responsibility of the user of this standard to
by the Beta Backscatter Method
establish appropriate safety and health practices and deter-
B 568 Test Method for Measurement of Coating Thickness
mine the applicability of regulatory limitations prior to use.
by X-Ray Spectrometry
2. Referenced Documents B 571 Test Methods for Adhesion of Metallic Coatings
B 578 Test Method for Microhardness of Electroplated
2.1 ASTM Standards:
Coatings
B 183 Practice for Preparation of Low-Carbon Steel for
B 579 Specification for Electrodeposited Coatings of Tin-
Electroplating
Lead Alloy (Solder Plate)
B 242 Practice for Preparation of High-Carbon Steel for
B 602 Test Method for Attribute Sampling of Metallic and
Electroplating
Inorganic Coatings
B 252 Guide for Preparation of ZincAlloy Die Castings for
B 678 Test Method for Solderability of Metallic-Coated
Electroplating Conversion Coatings
Products
B 253 Guide for Preparation of Aluminum Alloys for Elec-
B 697 Guide for Selection of Sampling Plans for Inspection
troplating
of Electrodeposited Metallic and Inorganic Coatings
B 254 Practice for Preparation of and Electroplating on
B 762 Method of Variables Sampling of Metallic and Inor-
Stainless Steel
ganic Coatings
B 281 Practice for Preparation of Copper and Copper-Base
B 849 Specification for Pre-treatments of Iron or Steel for
Alloys for Electroplating and Conversion Coatings
Reducing the Risk of Hydrogen Embrittlement
B 322 Practice for Cleaning Metals Prior to Electroplating
B 850 Guide for Post-Coating Treatments of Steel for Re-
ducing the Risk of Hydrogen Embrittlement
This specification is under the jurisdiction of ASTM Committee B08 on 4
D 3951 Practice for Commercial Packaging
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.02 on Precious Metal Coatings.
Current edition approved May 10, 1997. Published February 1998. Originally
published as B 700 – 81. Last previous edition B 700 – 90. Annual Book of ASTM Standards, Vol 02.04.
2 4
Annual Book of ASTM Standards, Vol 02.05. Annual Book of ASTM Standards, Vol 15.09.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B 700 – 97 (2002)
stated function of the coating and are acceptable to the purchaser (see
E 1004 Practice for Determining Electrical Conductivity
Appendix X1).
Using the Electromagnetic (Eddy-Current) Method
F 519 Test Method for Mechanical Hydrogen Embrittle-
4.3 Surface Appearance—Specify by Grade in letter code
ment Evaluation of Plating Processes and Service Environ-
as follows:
ments
Grade A, Mat—Electrodeposits without luster, obtained
from electroplating solutions operated without the use of
3. Terminology
brighteners.
3.1 Definitions—Many of the terms used in this specifica-
Grade B, Bright—Electrodeposits obtained by the use of
tion are defined in Terminologies B 374 or B 542.
brighteners in the electroplating bath.
3.2 Definitions of Terms Specific to This Standard:
Grade C, Bright—Electrodeposits obtained by mechanical
3.2.1 rack-plating—an electrodeposition process in which
or chemical polishing of Grade A silver coatings.
articles to be coated are mounted on racks or other fixtures
Grade D, Semibright—Electrodeposits obtained by the use
during the process.
of addition agents in the electroplating bath.
3.2.2 significant surfaces—surfaces that are normally vis-
4.4 Supplementary Surface Treatment—Specifyby Classin
ible, directly or by reflection, or that are essential to the
letter code as follows:
serviceability or function of the article or which can be the
Class N—A finish that has had no supplementary tarnish
source of corrosion products or tarnish films that interfere with
resistant (that is, chromate) treatment (see Appendix X5).
the function or desirable appearances of the article. When
Class S—A finish that has had a supplementary tarnish
necessary, the significant surfaces shall be indicated on the
resistant (that is, chromate) treatment.
drawings of the parts, or by the provisions of suitably marked
samples.
NOTE 2—Class S is not suitable for food service applications.
3.2.2.1 Discussion—Variation in the coating thickness from
point-to-pointonacoatedarticleisaninherentcharacteristicof 5. Ordering Information
electroplating processes. Therefore, the coating thickness will
5.1 To make application of this standard complete, the
have to exceed the specified value at some points on the
purchaser needs to supply the following information to the
significant surfaces to ensure that the thickness equals or
seller in the purchase order or other governing document:
exceeds the specified value at all points. The average coating
5.1.1 Name, designation, and year of issue of this standard.
thickness on the article usually will be greater than that
5.1.2 Type (see 4.2), Grade (see 4.3), Class (see 4.4) and
specified; how much greater is largely determined by the shape
Thickness (see 6.6 and Appendix X3).
of the article (see Practice B 507) and the characteristics of the
5.1.3 Nature of Substrate—If, for example, it is high
electroplating process.Additionally, the average coating thick-
strength steel, the need for stress relief (see 6.3.2.1) and
ness on an article will vary from article to article within a
embrittlement relief (see 6.3.5.1). If it is copper, an undercoat
production lot. If all the articles in a production lot are to meet
is needed (see S1.3) for some applications.
the thickness requirement, the average coating thickness of a
5.1.4 Significant Surfaces (see section 3.2.2).
production lot as a whole will be greater than the average
5.1.5 Appearance (see 6.7).
necessary to ensure that a single article meets requirements.
5.1.6 Underplates (see 6.3.4 and S1.3).
3.2.3 strike or flash—a thin, typically less than 0.25-µm (10
5.1.7 Requirements and methods of testing for one or more
µ-in.) metallic coating layer between metallic coatings to
improve adhesion. of the following: need for and type of test specimens (see 8.1),
thickness (see 6.6, 8.2, and Appendix X3), adhesion (see 6.8
3.2.4 underplating—an application of a metallic coating
layer between the basis metal or substrate and the topmost and 8.3), hardness (see 6.10.1 and 8.7), absence of embrittle-
ment (see 8.4), solderability (see 6.9 and 8.5), spectral reflec-
metallic coating or coatings (see 6.3.4).
tance(see6.10.2and8.8),orelectricalconductivity(see6.10.3
4. Classification and 8.9).
5.1.8 Sampling Plans and QualityAssurance (see Section 7
4.1 Electrodepositedcoatingsofsilvershallbeclassifiedfor
and S1.2).
Type based on minimum purity, Grade whether bright,
semibright, or mat, Class if supplementary surface treatment is
6. Coating Requirements
applied, and thickness in micrometers.
4.2 Purity—Specify by Type as follows:
6.1 Nature of Coating—The coating essentially shall be
Type 1—99.9 % min
silver,consideringthetypespecified,producedbyelectrodepo-
Type 2—99.0 % min
sition from aqueous electrolytes.
Type 3—98.0 % min
6.2 Purity of Coating—The coating shall meet the chemical
composition requirements of the specified type as defined in
NOTE 1—Metallic or organic brighteners used for grain refinement may
be present in the electrodeposit so long as they do not interfere with the 4.2 and measured as described in 8.6.
6.3 Process:
6.3.1 The basis metal shall be subjected to such cleaning
procedures as are necessary to ensure a surface satisfactory for
Annual Book of ASTM Standards, Vol 03.03.
Annual Book of ASTM Standards, Vol 15.03. subsequent electroplating. Materials used for cleaning shall
B 700 – 97 (2002)
NOTE 5—Coated finishes generally perform better in service when the
have no damaging effects on the basis metal resulting in pits,
substrate over which they are applied is smooth and free from torn metal,
intergranular attack, stress corrosion cracking, or hydrogen
inclusions, pores, and other defects. It is recommended that the specifi-
embrittlement.
cations covering the unfinished product provides limits for those defects.
Ametal finisher often can remove defects by means of special treatments
NOTE 3—For basis metal preparations, the following appropriate
such as grinding, polishing, abrasive blasting, chemical treatments, and
ASTM standards are recommended: Practices B 183, B 242, B 252,
electropolishing. However, these are not normal for the treatment steps
B 254, B 281, B 322, B 343, B 481, and B 482, and Guide B 253.
preceding application of the finish. When they are desired, they are the
6.3.2 Preplating Operations—Electroplating shall be ap-
subject of special agreement between the purchaser and the supplier.
plied after all basis metal heat treatments and mechanical
6.8 Adhesion—The silver coatings shall be free of blisters
operations such as forming, machining, and joining of the
and peeled areas indicating poor adhesion when tested in
article have been completed.
accordance with 8.3.
NOTE 4—Silver deposits may be used to facilitate mechanical opera-
NOTE 6—Some applications may require no separation by any me-
tions such as forming and drawing. In these applications, silver is applied
chanical means such as machining or milling through the interface.
before such process steps.
6.9 Solderability—The silver plated surfaces shall produce
6.3.2.1 Stress Relief Treatment—Parts that are made of
solder coatings which shall be bright, smooth, and uniform.At
steels with ultimate tensile strength of 1000 MPa or over
least95 %ofthesamplesurfaceshallshowgoodwettingwhen
(hardness of 31 HRC or greater) that have been machined,
tested as described in 8.5.
ground, cold-formed or cold-straightened subsequent to heat
6.10 Supplementary Requirements:
treatment, may require stress relief heat treatment when speci-
6.10.1 Hardness—Ifahardnessrequirementisspecified,the
fied by the purchaser, the tensile strength to be supplied by the
hardness of the silver coatings shall conform to that specified
purchaser. Specification B 849 may be consulted for a list of
as measured as described in 8.7.
pretreatments that are used widely.
6.10.2 Spectral Reflectance—The spectral reflectance of the
6.3.3 Strike—The final silver coating shall be preceded by a
silver coatings, if required, shall conform to that specified
silver or gold strike for optimum adhesion.
when measured as described in 8.8.
6.3.4 Underplating—A nickel or nickel-alloy intermediate
6.10.3 Electrical Conductivity—The electrical conductivity
layer, at least 1 µm thick, shall be applied before the silver
of the silver coatings, if required, shall conform to that
electroplate when the product being plated is made from
specified when measured as described in 8.9.
copper or copper alloy. Nickel underplatings are also applied
for other reasons.
7. Sampling
6.3.5 Post-Plating Procedures:
7.1 A random sample of the size required by Test Method
6.3.5.1 Embrittlement Relief—Parts that are made of steels
B 602 or Method B 762 shall be selected from the inspection
with ultimate tensile strength of 100 MPa or over (hardness of
lot (see 7.2). The articles in the lot shall be classified as
31 HRC or greater), as well as surface-hardened parts, may
conforming or nonconforming to each requirement according
require post-coating hydrogen embrittlement relief baking
to the criteria of the sampling plans in the chosen method.
when specified by the purchaser, the tensile strength to be
NOTE 7—Test Method B 602 contains four sampling plans, three for
supplied by the purchaser. Specification B 850 may be con-
usewithnondestructivetestmethods;thefourthisforusewithdestructive
sulted for a list of post-treatments that are used widely.
test methods. The three methods for nondestructive tests differ in the
6.4 Surface Appearance—The coating’s surface finish shall
quality level they require of the product. Test Method B 602 requires use
meet the requirements of the specified grade defined in 4.3. of the plan with the intermediate quality level unless the purchaser
specifies otherwise. It is recommended that the purchaser compare the
6.5 Supplementary Post Treatment—The coating shall meet
plans with his needs and state which plan is to be used. If the plans inTest
the requirements of the specified class defined in 4.4.
Method B 602 do not serve the needs, additional ones are given in Guide
6.6 Thickness—The silver coating thickness on significant
B 697 which provides a large number of plans
...
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