ASTM B545-97(2004)e1
(Specification)Standard Specification for Electrodeposited Coatings of Tin
Standard Specification for Electrodeposited Coatings of Tin
ABSTRACT
This specification covers the requirements for electrodeposited tin coatings applied to metallic articles to provide a low contact resistance surface, to protect against corrosion, to facilitate soldering, to provide anti-galling properties, and to be a stop-off coating in the nitriding of high-strength steels. This specification does not cover hot-dipped tin or other non-electrodeposited coatings, and mill products. Coatings shall be grouped into six service classes, which is based on the minimum thickness and severity of service required for the coating, and three surface appearance types, which is based on the type electroplating process employed. The surface appearance types are matte tin electrodeposits, bright tin electrodeposits, and flow-brightened electrodeposits. Coatings shall be sampled, tested and conform accordingly to specified requirements as to appearance, purity, local and mean thickness, integrity (including gross defects, mechanical damage, and porosity), adhesion, solderability, and hydrogen embrittlement relief.
SCOPE
1.1 This specification covers the requirements for electrodeposited (electroplated) coatings of tin applied to metallic articles. Tin coatings are used to provide a low contact-resistance surface, to protect against corrosion (see ), to facilitate soldering, to provide anti-galling properties, and to be a stopoff coating in the nitriding of high-strength steels.
1.2 Some corrosion can be expected from tin coatings exposed outdoors. In normal indoor exposure, tin is protective on iron, steel, nickel, copper, and their alloys. Corrosion can be expected at discontinuities in the coating (such as pores) due to galvanic couples formed between the tin and the underlying metal through the discontinuities, especially in humid atmospheres. Porosity increases as the coating thickness decreases, so that minimum thicknesses must be specified for each application. Parts coated with tin can be assembled safely in contact with iron and steel, tin-coated aluminum, yellow chromated zinc, cadmium, and solder coatings. (See for oxidation and corrosion properties.)
1.3 This specification applies to electroplated coatings of not less than 99 % tin (except where deliberately alloyed for special purposes, as stated in ) obtained from any of the available tin electroplating processes (see ).
1.4 This specification does not apply to hot-dipped tin or other non-electrodeposited coating; it also does not apply to mill products. For mill products, refer to Specifications A 623 or A 623M.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6This 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
Relations
Buy Standard
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.
´1
Designation: B545 – 97 (Reapproved 2004)
Standard Specification for
Electrodeposited Coatings of Tin
This standard is issued under the fixed designation B545; 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.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—The warning note in S4.1 was editorially updated in April 2004.
1. Scope 2. Referenced Documents
1.1 This specification covers the requirements for electrode- 2.1 ASTM Standards:
posited (electroplated) coatings of tin applied to metallic A623 Specification for Tin Mill Products, General Require-
articles. Tin coatings are used to provide a low contact- ments
resistance surface, to protect against corrosion (see 1.2), to A623M Specification for Tin Mill Products, General Re-
facilitatesoldering,toprovideanti-gallingproperties,andtobe quirements [Metric]
a stopoff coating in the nitriding of high-strength steels. B32 Specification for Solder Metal
1.2 Some corrosion can be expected from tin coatings B183 Practice for Preparation of Low-Carbon Steel for
exposed outdoors. In normal indoor exposure, tin is protective Electroplating
oniron,steel,nickel,copper,andtheiralloys.Corrosioncanbe B242 Guide for Preparation of High-Carbon Steel for Elec-
expected at discontinuities in the coating (such as pores) due to troplating
galvanic couples formed between the tin and the underlying B246 Specification for Tinned Hard-Drawn and Medium-
metal through the discontinuities, especially in humid atmo- Hard-Drawn Copper Wire for Electrical Purposes
spheres. Porosity increases as the coating thickness decreases, B281 Practice for Preparation of Copper and Copper-Base
so that minimum thicknesses must be specified for each Alloys for Electroplating and Conversion Coatings
application. Parts coated with tin can be assembled safely in B320 Practice for Preparation of Iron Castings for Electro-
contact with iron and steel, tin-coated aluminum, yellow plating
chromated zinc, cadmium, and solder coatings. (See X5.2 for B322 Guide for Cleaning Metals Prior to Electroplating
oxidation and corrosion properties.) B374 Terminology Relating to Electroplating
1.3 This specification applies to electroplated coatings of B487 Test Method for Measurement of Metal and Oxide
not less than 99 % tin (except where deliberately alloyed for CoatingThicknessbyMicroscopicalExaminationofCross
special purposes, as stated in X6.3) obtained from any of the Section
available tin electroplating processes (see 4.3). B499 Test Method for Measurement of Coating Thick-
1.4 This specification does not apply to hot-dipped tin or nessesbytheMagneticMethod:NonmagneticCoatingson
other non-electrodeposited coating; it also does not apply to Magnetic Basis Metals
mill products. For mill products, refer to Specifications A623 B504 Test Method for Measurement of Thickness of Me-
or A623M. tallic Coatings by the Coulometric Method
1.5 The values stated in SI units are to be regarded as the B507 Practice for Design ofArticles to Be Electroplated on
standard. The values given in parentheses are for information Racks
only. B542 Terminology Relating to Electrical Contacts and
1.6 This standard does not purport to address all of the Their Use
safety concerns, if any, associated with its use. It is the B558 Practice for Preparation of NickelAlloys for Electro-
responsibility of the user of this standard to establish appro- plating
priate safety and health practices and determine the applica- B567 Test Method for Measurement of Coating Thickness
bility of regulatory limitations prior to use. by the Beta Backscatter Method
B568 Test Method for Measurement of Coating Thickness
This specification is under the jurisdiction of ASTM Committee B08 on
Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee
B08.08.04 on Soft Metals. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2004. Published April 2004. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
´1
approved in 1971. Last previous edition approved in 1997 as B545 – 97 . DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/B0545-97R04E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
B545 – 97 (2004)
by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic
Class Minimum Thickness Typical Applications
Coatings
A 2.5 µm (100 µin.) Mild service conditions, particularly where the
B602 Test Method for Attribute Sampling of Metallic and
significant surface is shielded from the atmo-
Inorganic Coatings
sphere (as in electronic connector housings). To
provide corrosion and tarnish resistance where
B659 Guide for Measuring Thickness of Metallic and Inor-
greater thicknesses may be detrimental to the
ganic Coatings
mechanical operation of the product (for ex-
B678 Test Method for Solderability of Metallic-Coated ample, small electrical spring contacts and re-
lays). Class A is often used for tin coatings that
Products
are not to be soldered, but must function as
B697 Guide for Selection of Sampling Plans for Inspection
low-resistance electrical contact surfaces.
of Electrodeposited Metallic and Inorganic Coatings B 5 µm (200 µin.) Mild service conditions with less severe require-
ments than Class C (below). Applications are
B762 Test Method of Variables Sampling of Metallic and
as follows: precoating on solderable basis met-
Inorganic Coatings
als to facilitate the soldering of electrical com-
ponents; as a surface preparation for protective
B765 Guide for Selection of Porosity and Gross Defect
painting; for antigalling purposes; and as a sto-
Tests for Electrodeposits and Related Metallic Coatings
poff in nitriding. Also found on baking pans after
B809 Test Method for Porosity in Metallic Coatings by
reflow.
C 8 µm (320 µin.), Moderate exposure conditions, usually indoors,
Humid Sulfur Vapor (“Flowers-of-Sulfur”)
(10 µm (400 µin.) but more severe than Class B. Examples are
B849 Specification for Pre-Treatments of Iron or Steel for
for steel substrates) electrical hardware (such as cases for relays
Reducing Risk of Hydrogen Embrittlement
and coils, transformer cans, screened cages,
chassis, frames, and fittings) and for retention
B850 Guide for Post-Coating Treatments of Steel for Re-
of the solderability of solderable articles during
ducing the Risk of Hydrogen Embrittlement
storage.
B851 Specification forAutomated Controlled Shot Peening
D 15 µm (600 µin.) Severe service, including exposure to damp-
(20 µm (800 µin.) ness and mild corrosion from moderate indus-
of Metallic Articles Prior to Nickel, Autocatalytic Nickel,
for steel substrates) trial environments. Examples are fittings for gas
or Chromium Plating, or as Final Finish
meters, automotive accessories (such as air
D3951 Practice for Commercial Packaging cleaners and oil filters), and in some electronic
applications.
E 30 µm (0.0012 in.) Very severe service conditions, including el-
3. Terminology
evated temperatures, where underlying metal
3.1 Definitions—Many of the terms used in this specifica-
diffusion and intermetallic formation processes
are accelerated. Thicknesses of 30 to 125 µm
tion are defined in Terminology B374 or B542, B374, and
(0.0012 to 0.005 in.) may be required if the
B542.
coating is subjected to abrasion or is exposed
3.1.1 rack-plating—an electrodeposition process in which to slowly corrosive liquids or corrosive atmo-
spheres or gases. Thicker coatings are used for
articles to be coated are mounted on racks or other fixtures
water containers, threaded steel couplings of oil
during the process.
drilling strings, and seacoast atmospheres.
3.1.2 significant surface—that portion of the surface of a Coatings subject to mild etchants are included.
F 1.5 µm (60 µin.) Similar to Class A, but for shorter-term contact
coated article at which the coating is required to meet all of the
applications and short shelf-life requirements,
requirements of the coating specification for that article;
subject to purchaser approval.
significant surfaces are usually those that are essential to the
4.3 Surface Appearance Type (Electroplating Process):
serviceability or function of the article, or that can be a source
4.3.1 Matte Tin Electrodeposits—Coatings with a matte
of corrosion products or tarnish films that interfere with the
appearance are obtained from tin plating baths (stannate,
function or desirable appearance of the article; significant
sulfate, methylsulfonate, and fluoborate) used without the
surfaces shall be indicated on the drawings of the parts or by
addition of any brightening agents. However, all matte baths
the provision of suitably marked samples.
(except for stannate baths) do require the addition of grain-
3.1.3 undercoating (see 3.1.4)—also called an underplate in
refiners, and often of other additives in order to produce the
the electronics industry.
desired matte finish.
3.1.4 underplating—application of a metallic coating layer
4.3.2 Bright Tin Electrodeposits—Bright coatings are ob-
between the basis metal or substrate and the topmost metallic
tained when proprietary brightening agents are used in specific
coating or coatings. The thickness of such an undercoating is
bright tin plating baths.
usually greater than 0.8 µm (30 µin.). This is in contrast to
4.3.3 Flow-Brightened Electrodeposits—Flow-brightened
strikes or flashes, whose thicknesses are generally much
coatings are obtained by heating the matte coating above the
smaller.
melting point of tin for a few seconds, followed by quenching;
palm oil and hydrogenated oils and fats are used as heat-
4. Classification
transfer medium at a temperature of 260 6 8°C (500 6 14°F),
4.1 General—Orders for articles to be plated in accordance
but other heating methods also are in use, such as hot air. The
with this specification shall specify the service class (4.2) (and
maximum thickness for flow-brightening is, in most cases,
underplating, if required), indicating the severity of service
approximately 8 µm (300 µin.); thicker coatings tend to dewet.
required for the coating. Other coatings variations, such as
The shape of the part is also a factor; flat surfaces dewet more
surface appearance type (4.3) or alloy composition (Appendix
readily than wires or rounded shapes.
X6), are optional.
4.2 Service Class: NOTE 1—Terms commonly used in soldering, such as dewet, are
´1
B545 – 97 (2004)
described in soldering textbooks (1) or reviews of solderability testing NOTE 3—Specification of the coating thickness in terms of the mean is
(2). Some examples are given in Appendix X6. normally made when the coated articles are small and relatively simple,
such as connector pins and terminals.
5. Ordering Information
NOTE 4—Thickness of electrodeposited coatings varies from point to
point on the surfaces of a product (see Practice B507). The thickness is
5.1 In order to make the application of this specification
less in interior corners and holes. Such surfaces are normally exempt from
complete, the purchaser must supply the following information
the thickness requirement. If the full thickness is required on these
to the seller in the purchase order and drawings:
surfaces,theelectroplaterwillhavetousespecialtechniquesthatprobably
5.1.1 Title,ASTM designation number, and year of issue of
will increase the cost of the process.
this specification;
NOTE 5—When articles are plated by mass plating techniques (such as
barrelplating),suchmeasurementmethodsas“stripandweigh”or“weigh
5.1.2 Deposit by classification (4.1), including thickness or
before and after plating” may be used to determine the mean thickness.
service class (4.2);
5.1.3 Composition and metallurgical condition of the sub-
6.6 Adhesion—Adhesion of the coating shall be tested by
strate to be coated (6.1);
one of the methods given inAppendix X2. The coating should
5.1.4 Additional underplating, if required (6.8);
adhere to the basis metal when subjected to the agreed test;
5.1.5 Surface-appearance type (for example, matte, flow-
flaking or blistering of the coating is to be taken as evidence of
brightened, or bright), if required (4.3 and 6.2);
unsatisfactory adhesion.
5.1.6 Location of significant surfaces (3.1.2);
6.7 Integrity of the Coating:
5.1.7 Hydrogen embrittlement relief, if required (Supple-
6.7.1 Gross Defects/Mechanical Damage—Coatings shall
mentary Requirement S2); and
be free of visible mechanical damage and similar gross defects
5.1.8 Any other items needing agreement (for example,
whenviewedatupto43magnification.Forsomeapplications,
6.5.2 and 8.5).
this requirement may be relaxed to allow for a small number of
such defects (per unit area), especially if they are outside of or
6. Coating Requirements
on the periphery of significant surfaces (also see 6.7.2).
6.1 Substrate—The metal substrate shall be subjected to
6.7.2 Porosity—Almostallas-platedelectrodepositscontain
such surface preparation, cleaning, and electroplating proce-
some porosity. The amount of porosity in the coating that may
dures as are necessary to yield deposits with the desired
betolerabledependsontheseverityoftheenvironmentthatthe
quality.
article is likely to encounter during service or storage. If the
pores are few in number, or away from significant surfaces,
NOTE 2—Careful preparation of metal surfaces is necessary in order to
assure good adhesion and quality. For suitable methods, see Practices their presence can often be tolerated. Such acceptance (or
B183, B242, B281, B320, B322, and B558. Also see 6.6.
pass-fail) criteria, if required, should be part of the product
specification for the particular article or coating requiring the
6.2 Electroplating shall be applied after all basis metal heat
porosity test. See 8.5 for porosity testing.
treatments and mechanical operations have been completed.
6.8 Underplating:
6.3 Appearance—Tin coatings shall have the characteristic
6.8.1 For tin coatings in Class A and Class F (4.2) that will
appearance, including surface texture (4.3), for the process
not be exposed to solder temperatures (especially those that
used. The appearance shall be uniform throughout, insofar as
must function as electrically conductive surfaces), a nickel
the basis metal will permit.They shall be adherent and visually
underplate or undercoating of at least 1.3 µm (50 µin.) shall be
freeofblisters,pits,peeledar
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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.
´1
Designation: B 545 – 97 (Reapproved 2004)
Designation:B545–97
Standard Specification for
Electrodeposited Coatings of Tin
This standard is issued under the fixed designation B 545; 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.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Paragraphs 1.3 and 4.1 were editorially corrected in March 2001.
—The warning note in S4.1 was editorially updated in April 2004.
1. Scope
1.1 Thisspecificationcoverstherequirementsforelectrodeposited(electroplated)coatingsoftinappliedtometallicarticles.Tin
coatings are used to provide a low contact-resistance surface, to protect against corrosion (see 1.2), to facilitate soldering, to
provide anti-galling properties, and to be a stopoff coating in the nitriding of high-strength steels.
1.2 Some corrosion can be expected from tin coatings exposed outdoors. In normal indoor exposure, tin is protective on iron,
steel, nickel, copper, and their alloys. Corrosion can be expected at discontinuities in the coating (such as pores) due to galvanic
couples formed between the tin and the underlying metal through the discontinuities, especially in humid atmospheres. Porosity
increases as the coating thickness decreases, so that minimum thicknesses must be specified for each application. Parts coated with
tin can be assembled safely in contact with iron and steel, tin-coated aluminum, yellow chromated zinc, cadmium, and solder
coatings. (See X5.2 for oxidation and corrosion properties.)
1.3 This specification applies to electroplated coatings of not less than 99 % tin (except where deliberately alloyed for special
purposes, as stated in X6.3) obtained from any of the available tin electroplating processes (see 4.3).
1.4 This specification does not apply to hot-dipped tin or other non-electrodeposited coating; it also does not apply to mill
products. For mill products, refer to Specifications A 623 or A 623M.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
A 623 Specification for Tin Mill Products, General Requirements
A 623M Specification for Tin Mill Products, General Requirements (Metric) [Metric]
B32 Specification for Solder Metal
B 183 Practice for Preparation of Low-Carbon Steel for Electroplating
B 242 Practice for Preparation of High-Carbon Steel for Electroplating
B 246 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical Purposes
B 281 Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
B 320 Practice for Preparation of Iron Castings for Electroplating
B 322 Practice for Cleaning Metals Prior to Electroplating
B 374 Terminology Relating to Electroplating
B 487 Test Method for Measurement of Metal and Oxide Coating Thicknesses by Microscopical Examination of a Cross
Section
B 499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic
Basis Metals
B 504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
This specification is under the jurisdiction ofASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.08.04 on
Light Metals.
Current edition approved Oct. 10, 1997. Published February 1998. Originally published as B545–71. Last previous edition B545–92.on Soft Metals.
´1
Current edition approved April 1, 2004. Published April 2004. Originally approved in 1971. Last previous edition approved in 1997 as B 545 – 97 .
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 01.06.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
B 545 – 97 (2004)
B545–97
B 507 Practice for Design of Articles to be Electroplated on Racks
B 542 Terminology Relating to Electrical Contacts and Their Use
B 558 Practice for Preparation of Nickel Alloys for Electroplating
B 567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B 568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B 571 Test Methods for Adhesion of Metallic Coatings Practice for Qualitative Adhesion Testing of Metallic Coatings
B 602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B 659 Guide for Measuring Thickness of Metallic and Inorganic Coatings
B 678 Test Method for Solderability of Metallic-Coated Products
B 697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B 762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
B 765 Guide to the for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
B 809 Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
B 849 Specification for Pre-Treatments of Iron or Steel for Reducing the Risk of Hydrogen Embrittlement
B 850 Specification for Post-Coating Treatments of Iron or Steel for Reducing the Risk of Hydrogen Embrittlement
B 851 Specification for Automated Controlled Shot Peening of Metallic Articles Prior to Nickel, Autocatalytic Nickel, or
Chromium Plating, or as a Final Finish
D 3951 Practice for Commercial Packaging
3. Terminology
3.1 Definitions—Many of the terms used in this specification are defined in Terminology B 374 or B 542.
3.1.1 rack-plating—an electrodeposition process in which articles to be coated are mounted on racks or other fixtures during
the process.
3.1.2 significant surface—that portion of the surface of a coated article at which the coating is required to meet all of the
requirementsofthecoatingspecificationforthatarticle;significantsurfacesareusuallythosethatareessentialtotheserviceability
or function of the article, or that can be a source of corrosion products or tarnish films that interfere with the function or desirable
appearance of the article; significant surfaces shall be indicated on the drawings of the parts or by the provision of suitably marked
samples.
3.1.3 undercoating (see 3.1.4)—also called an underplate in the electronics industry.
3.1.4 underplating—application of a metallic coating layer between the basis metal or substrate and the topmost metallic
coating or coatings. The thickness of such an undercoating is usually greater than 0.8 µm (30 µin.). This is in contrast to strikes
or flashes, whose thicknesses are generally much smaller.
4. Classification
4.1 General—Orders for articles to be plated in accordance with this specification shall specify the service class (4.2) (and
underplating, if required), indicating the severity of service required for the coating. Other coatings variations, such as surface
appearance type (4.3) or alloy composition (Appendix X6), are optional.
4.2 Service Class:
Class Minimum Thickness Typical Applications
A 2.5 µm (100 µin.) Mild service conditions, particularly where the
significant surface is shielded from the atmo-
sphere (as in electronic connector housings). To
provide corrosion and tarnish resistance where
greater thicknesses may be detrimental to the
mechanical operation of the product (for ex-
ample, small electrical spring contacts and re-
lays). Class A is often used for tin coatings that
are not to be soldered, but must function as
low-resistance electrical contact surfaces.
B 5 µm (200 µin.) Mild service conditions with less severe require-
ments than Class C (below). Applications are
as follows: precoating on solderable basis met-
als to facilitate the soldering of electrical com-
ponents; as a surface preparation for protective
painting; for antigalling purposes; and as a sto-
poff in nitriding. Also found on baking pans after
reflow.
´1
B 545 – 97 (2004)
B545–97
C 8 µm (320 µin.), Moderate exposure conditions, usually indoors,
(10 µm (400 µin.) but more severe than Class B. Examples are
for steel substrates) electrical hardware (such as cases for relays
and coils, transformer cans, screened cages,
chassis, frames, and fittings) and for retention
of the solderability of solderable articles during
storage.
D 15 µm (600 µin.) Severe service, including exposure to damp-
(20 µm (800 µin.) ness and mild corrosion from moderate indus-
for steel substrates) trial environments. Examples are fittings for gas
meters, automotive accessories (such as air
cleaners and oil filters), and in some electronic
applications.
E 30 µm (0.0012 in.) Very severe service conditions, including el-
evated temperatures, where underlying metal
diffusion and intermetallic formation processes
are accelerated. Thicknesses of 30 to 125 µm
(0.0012 to 0.005 in.) may be required if the
coating is subjected to abrasion or is exposed
to slowly corrosive liquids or corrosive atmo-
spheres or gases. Thicker coatings are used for
water containers, threaded steel couplings of oil
drilling strings, and seacoast atmospheres.
Coatings subject to mild etchants are included.
F 1.5 µm (60 µin.) Similar to Class A, but for shorter-term contact
applications and short shelf-life requirements,
subject to purchaser approval.
4.3 Surface Appearance Type (Electroplating Process):
4.3.1 Matte Tin Electrodeposits—Coatings with a matte appearance are obtained from tin plating baths (stannate, sulfate,
methylsulfonate,andfluoborate)usedwithouttheadditionofanybrighteningagents.However,allmattebaths(exceptforstannate
baths) do require the addition of grain-refiners, and often of other additives in order to produce the desired matte finish.
4.3.2 Bright Tin Electrodeposits—Bright coatings are obtained when proprietary brightening agents are used in specific bright
tin plating baths.
4.3.3 Flow-Brightened Electrodeposits—Flow-brightened coatings are obtained by heating the matte coating above the melting
point of tin for a few seconds, followed by quenching; palm oil and hydrogenated oils and fats are used as heat-transfer medium
at a temperature of 260 6 8°C (500 6 14°F), but other heating methods also are in use, such as hot air. The maximum thickness
for flow-brightening is, in most cases, approximately 8 µm (300 µin.); thicker coatings tend to dewet. The shape of the part is also
a factor; flat surfaces dewet more readily than wires or rounded shapes.
NOTE 1—Terms commonly used in soldering, such as dewet, are described in soldering textbooks (1) or reviews of solderability testing (2). Some
examples are given in Appendix X6.
5. Ordering Information
5.1 In order to make the application of this specification complete, the purchaser must supply the following information to the
seller in the purchase order and drawings:
5.1.1 Title, ASTM designation number, and year of issue of this specification;
5.1.2 Deposit by classification (4.1), including thickness or service class (4.2);
5.1.3 Composition and metallurgical condition of the substrate to be coated (6.1);
5.1.4 Additional underplating, if required (6.8);
5.1.5 Surface-appearance type (for example, matte, flow-brightened, or bright), if required (4.3 and 6.2);
5.1.6 Location of significant surfaces (3.1.2);
5.1.7 Hydrogen embrittlement relief, if required (Supplementary Requirement S2); and
5.1.8 Any other items needing agreement (for example, 6.5.2 and 8.5).
6. Coating Requirements
6.1 Substrate—Themetalsubstrateshallbesubjectedtosuchsurfacepreparation,cleaning,andelectroplatingproceduresasare
necessary to yield deposits with the desired quality.
NOTE2—Careful preparation of metal surfaces is necessary in order to assure good adhesion and quality. For suitable methods, see Practices B183,
B242, B281, B320, B322, and B558 2—Careful preparation of metal surfaces is necessary in order to assure good adhesion and quality. For suitable
methods, see Practices B 183, B 242, B 281, B 320, B 322, and B 558. Also see 6.6.
6.2 Electroplating shall be applied after all basis metal heat treatments and mechanical operations have been completed.
6.3 Appearance—Tin coatings shall have the characteristic appearance, including surface texture (4.3), for the process used.
The appearance shall be uniform throughout, insofar as the basis metal will permit. They shall be adherent and visually free of
Annual Book of ASTM Standards, Vol 02.04.
The boldface numbers in parentheses refer to the list of references at the end of this specification.
´1
B 545 – 97 (2004)
B545–97
blisters, pits, peeled areas, cracks, nodules, and unplated areas. They shall not be stained or discolored. Flow-brightened coatings
shall be free of dewetted areas and beads. All surfaces shall be substantially free of grease or oil used in the flow-brightening
process.
6.4 All tin-coated articles shall be clean and undamaged. When necessary, preliminary samples showing the finish shall be
supplied to and approved by the purchaser. Where a contact mark is inevitable, its location shall be subject to agreement between
the supplier and the purchaser.
6.5 Thickness of Coatings—Tin coatings on articles shall conform to the thickness requirements specified in 4.2 as to the
minimum thickness on significant surfaces.
6.5.1 Local Thickness—The thickness values specified in 4.2 are the minimum local thicknesses measured by one or more of
the methods given in Practice B 659 at any number of desired spots on the significant surface.
6.5.2 Mean Thickness—When specified by the purchaser, instead of being a local minimum requirement, the thickness
requirement can be a minimum (arithmetic) mean thickness.
NOTE 3—Specification of the coating thickness in terms of the mean is normally made when the coated articles are small and relatively simple, such
as connector pins and termin
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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.
´1
Designation: B 545 – 97 (Reapproved 2004)
Designation:B545–97
Standard Specification for
Electrodeposited Coatings of Tin
This standard is issued under the fixed designation B 545; 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.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Paragraphs 1.3 and 4.1 were editorially corrected in March 2001.
—The warning note in S4.1 was editorially updated in April 2004.
1. Scope
1.1 Thisspecificationcoverstherequirementsforelectrodeposited(electroplated)coatingsoftinappliedtometallicarticles.Tin
coatings are used to provide a low contact-resistance surface, to protect against corrosion (see 1.2), to facilitate soldering, to
provide anti-galling properties, and to be a stopoff coating in the nitriding of high-strength steels.
1.2 Some corrosion can be expected from tin coatings exposed outdoors. In normal indoor exposure, tin is protective on iron,
steel, nickel, copper, and their alloys. Corrosion can be expected at discontinuities in the coating (such as pores) due to galvanic
couples formed between the tin and the underlying metal through the discontinuities, especially in humid atmospheres. Porosity
increases as the coating thickness decreases, so that minimum thicknesses must be specified for each application. Parts coated with
tin can be assembled safely in contact with iron and steel, tin-coated aluminum, yellow chromated zinc, cadmium, and solder
coatings. (See X5.2 for oxidation and corrosion properties.)
1.3 This specification applies to electroplated coatings of not less than 99 % tin (except where deliberately alloyed for special
purposes, as stated in X6.3) obtained from any of the available tin electroplating processes (see 4.3).
1.4 This specification does not apply to hot-dipped tin or other non-electrodeposited coating; it also does not apply to mill
products. For mill products, refer to Specifications A 623 or A 623M.
1.5 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.6 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.
2. Referenced Documents
2.1 ASTM Standards:
A 623 Specification for Tin Mill Products, General Requirements
A 623M Specification for Tin Mill Products, General Requirements (Metric) [Metric]
B32 Specification for Solder Metal
B 183 Practice for Preparation of Low-Carbon Steel for Electroplating
B 242 Practice for Preparation of High-Carbon Steel for Electroplating
B 246 Specification for Tinned Hard-Drawn and Medium-Hard-Drawn Copper Wire for Electrical Purposes
B 281 Practice for Preparation of Copper and Copper-Base Alloys for Electroplating and Conversion Coatings
B 320 Practice for Preparation of Iron Castings for Electroplating
B 322 Practice for Cleaning Metals Prior to Electroplating
B 374 Terminology Relating to Electroplating
B 487 Test Method for Measurement of Metal and Oxide Coating Thicknesses by Microscopical Examination of a Cross
Section
B 499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic
Basis Metals
B 504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
This specification is under the jurisdiction ofASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.08.04 on
Light Metals.
Current edition approved Oct. 10, 1997. Published February 1998. Originally published as B545–71. Last previous edition B545–92.on Soft Metals.
´1
Current edition approved April 1, 2004. Published April 2004. Originally approved in 1971. Last previous edition approved in 1997 as B 545 – 97 .
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 01.06.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
´1
B 545 – 97 (2004)
B545–97
B 507 Practice for Design of Articles to be Electroplated on Racks
B 542 Terminology Relating to Electrical Contacts and Their Use
B 558 Practice for Preparation of Nickel Alloys for Electroplating
B 567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B 568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B 571 Test Methods for Adhesion of Metallic Coatings Practice for Qualitative Adhesion Testing of Metallic Coatings
B 602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B 659 Guide for Measuring Thickness of Metallic and Inorganic Coatings
B 678 Test Method for Solderability of Metallic-Coated Products
B 697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
B 762 Test Method of Variables Sampling of Metallic and Inorganic Coatings
B 765 Guide to the for Selection of Porosity and Gross Defect Tests for Electrodeposits and Related Metallic Coatings
B 809 Test Method for Porosity in Metallic Coatings by Humid Sulfur Vapor (“Flowers-of-Sulfur”)
B 849 Specification for Pre-Treatments of Iron or Steel for Reducing the Risk of Hydrogen Embrittlement
B 850 Specification for Post-Coating Treatments of Iron or Steel for Reducing the Risk of Hydrogen Embrittlement
B 851 Specification for Automated Controlled Shot Peening of Metallic Articles Prior to Nickel, Autocatalytic Nickel, or
Chromium Plating, or as a Final Finish
D 3951 Practice for Commercial Packaging
3. Terminology
3.1 Definitions—Many of the terms used in this specification are defined in Terminology B 374 or B 542.
3.1.1 rack-plating—an electrodeposition process in which articles to be coated are mounted on racks or other fixtures during
the process.
3.1.2 significant surface—that portion of the surface of a coated article at which the coating is required to meet all of the
requirementsofthecoatingspecificationforthatarticle;significantsurfacesareusuallythosethatareessentialtotheserviceability
or function of the article, or that can be a source of corrosion products or tarnish films that interfere with the function or desirable
appearance of the article; significant surfaces shall be indicated on the drawings of the parts or by the provision of suitably marked
samples.
3.1.3 undercoating (see 3.1.4)— also called an underplate in the electronics industry.
3.1.4 underplating—application of a metallic coating layer between the basis metal or substrate and the topmost metallic
coating or coatings. The thickness of such an undercoating is usually greater than 0.8 µm (30 µin.). This is in contrast to strikes
or flashes, whose thicknesses are generally much smaller.
4. Classification
4.1 General—Orders for articles to be plated in accordance with this specification shall specify the service class (4.2) (and
underplating, if required), indicating the severity of service required for the coating. Other coatings variations, such as surface
appearance type (4.3) or alloy composition (Appendix X6), are optional.
4.2 Service Class:
Class Minimum Thickness Typical Applications
A 2.5 µm (100 µin.) Mild service conditions, particularly where the
significant surface is shielded from the atmo-
sphere (as in electronic connector housings). To
provide corrosion and tarnish resistance where
greater thicknesses may be detrimental to the
mechanical operation of the product (for ex-
ample, small electrical spring contacts and re-
lays). Class A is often used for tin coatings that
are not to be soldered, but must function as
low-resistance electrical contact surfaces.
B 5 µm (200 µin.) Mild service conditions with less severe require-
ments than Class C (below). Applications are
as follows: precoating on solderable basis met-
als to facilitate the soldering of electrical com-
ponents; as a surface preparation for protective
painting; for antigalling purposes; and as a sto-
poff in nitriding. Also found on baking pans after
reflow.
´1
B 545 – 97 (2004)
B545–97
C 8 µm (320 µin.), Moderate exposure conditions, usually indoors,
(10 µm (400 µin.) but more severe than Class B. Examples are
for steel substrates) electrical hardware (such as cases for relays
and coils, transformer cans, screened cages,
chassis, frames, and fittings) and for retention
of the solderability of solderable articles during
storage.
D 15 µm (600 µin.) Severe service, including exposure to damp-
(20 µm (800 µin.) ness and mild corrosion from moderate indus-
for steel substrates) trial environments. Examples are fittings for gas
meters, automotive accessories (such as air
cleaners and oil filters), and in some electronic
applications.
E 30 µm (0.0012 in.) Very severe service conditions, including el-
evated temperatures, where underlying metal
diffusion and intermetallic formation processes
are accelerated. Thicknesses of 30 to 125 µm
(0.0012 to 0.005 in.) may be required if the
coating is subjected to abrasion or is exposed
to slowly corrosive liquids or corrosive atmo-
spheres or gases. Thicker coatings are used for
water containers, threaded steel couplings of oil
drilling strings, and seacoast atmospheres.
Coatings subject to mild etchants are included.
F 1.5 µm (60 µin.) Similar to Class A, but for shorter-term contact
applications and short shelf-life requirements,
subject to purchaser approval.
4.3 Surface Appearance Type (Electroplating Process):
4.3.1 Matte Tin Electrodeposits—Coatings with a matte appearance are obtained from tin plating baths (stannate, sulfate,
methylsulfonate,andfluoborate)usedwithouttheadditionofanybrighteningagents.However,allmattebaths(exceptforstannate
baths) do require the addition of grain-refiners, and often of other additives in order to produce the desired matte finish.
4.3.2 Bright Tin Electrodeposits—Bright coatings are obtained when proprietary brightening agents are used in specific bright
tin plating baths.
4.3.3 Flow-Brightened Electrodeposits—Flow-brightenedcoatingsareobtainedbyheatingthemattecoatingabovethemelting
point of tin for a few seconds, followed by quenching; palm oil and hydrogenated oils and fats are used as heat-transfer medium
at a temperature of 260 6 8°C (500 6 14°F), but other heating methods also are in use, such as hot air. The maximum thickness
for flow-brightening is, in most cases, approximately 8 µm (300 µin.); thicker coatings tend to dewet. The shape of the part is also
a factor; flat surfaces dewet more readily than wires or rounded shapes.
NOTE 1—Terms commonly used in soldering, such as dewet, are described in soldering textbooks (1) or reviews of solderability testing (2). Some
examples are given in Appendix X6.
5. Ordering Information
5.1 In order to make the application of this specification complete, the purchaser must supply the following information to the
seller in the purchase order and drawings:
5.1.1 Title, ASTM designation number, and year of issue of this specification;
5.1.2 Deposit by classification (4.1), including thickness or service class (4.2);
5.1.3 Composition and metallurgical condition of the substrate to be coated (6.1);
5.1.4 Additional underplating, if required (6.8);
5.1.5 Surface-appearance type (for example, matte, flow-brightened, or bright), if required (4.3 and 6.2);
5.1.6 Location of significant surfaces (3.1.2);
5.1.7 Hydrogen embrittlement relief, if required (Supplementary Requirement S2); and
5.1.8 Any other items needing agreement (for example, 6.5.2 and 8.5).
6. Coating Requirements
6.1 Substrate—Themetalsubstrateshallbesubjectedtosuchsurfacepreparation,cleaning,andelectroplatingproceduresasare
necessary to yield deposits with the desired quality.
NOTE 2—Careful preparation of metal surfaces is necessary in order to assure good adhesion and quality. For suitable methods, see Practices B 183,
B 242, B 281, B 320, B 322, and B 558. Also see 6.6.
6.2 Electroplating shall be applied after all basis metal heat treatments and mechanical operations have been completed.
6.3 Appearance—Tin coatings shall have the characteristic appearance, including surface texture (4.3), for the process used.
The appearance shall be uniform throughout, insofar as the basis metal will permit. They shall be adherent and visually free of
Annual Book of ASTM Standards, Vol 02.04.
The boldface numbers in parentheses refer to the list of references at the end of this specification.
´1
B 545 – 97 (2004)
B545–97
blisters, pits, peeled areas, cracks, nodules, and unplated areas. They shall not be stained or discolored. Flow-brightened coatings
shall be free of dewetted areas and beads. All surfaces shall be substantially free of grease or oil used in the flow-brightening
process.
6.4 All tin-coated articles shall be clean and undamaged. When necessary, preliminary samples showing the finish shall be
supplied to and approved by the purchaser. Where a contact mark is inevitable, its location shall be subject to agreement between
the supplier and the purchaser.
6.5 Thickness of Coatings—Tin coatings on articles shall conform to the thickness requirements specified in 4.2 as to the
minimum thickness on significant surfaces.
6.5.1 Local Thickness—The thickness values specified in 4.2 are the minimum local thicknesses measured by one or more of
the methods given in Practice B 659 at any number of desired spots on the significant surface.
6.5.2 Mean Thickness—When specified by the purchaser, instead of being a local minimum requirement, the thickness
requirement can be a minimum (arithmetic) mean thickness.
NOTE 3—Specification of the coating thickness in terms of the mean is normally made when the coated articles are small and relatively simple, such
as connector pins and terminals.
NOTE 4—Thickness of electrodeposited coatings varies from point to point on the surfaces of a product (see Practice B 507). The thickness is less in
interior corners and holes. S
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.