ASTM B520-93(2007)
(Specification)Standard Specification for Tin-Coated, Copper-Clad Steel Wire for Electronic Application
Standard Specification for Tin-Coated, Copper-Clad Steel Wire for Electronic Application
ABSTRACT
This specification covers tin-coated, copper-clad steel wires for electronic applications. The four classes of steel wires considered here are: hard-drawn wires with 30% nominal conductivity (Class T30HS); annealed wires with 30% nominal conductivity (Class T30A); hard-drawn wires with 40% nominal conductivity (Class T40HS); and annealed wires with 40% nominal conductivity (Class T40A). Specimens shall go through tests and shall adhere to specified requirements for dimensions, electrical resistivity, tensile strength, and coating continuity and adherence.
SCOPE
1.1 This specification covers tin-coated copper-clad steel wire for electronic application.
1.2 Four classes of tin-coated copper-clad steel wire are covered as follows:
1.2.1 Class T30HS Nominal 30 % conductivity, hard-drawn,
1.2.2 Class T30A - Nominal 30 % conductivity, annealed,
1.2.3 Class T40HS Nominal 40 % conductivity, hard-drawn, and
1.2.4 Class T40A - Nominal 40 % conductivity, annealed.
1.3 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate. The values given in parentheses are for information only.
The following safety hazards caveat pertains only to the test method portion, 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. (Warning-Consideration should be given to toxicity and flammability when selecting solvent cleaners.)
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Designation:B520 −93(Reapproved 2007)
Standard Specification for
Tin-Coated, Copper-Clad Steel Wire for Electronic
Application
This standard is issued under the fixed designation B520; 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.
1. Scope B258 Specification for Nominal Diameters and Cross-
SectionalAreasofAWGSizesofSolidRoundWiresUsed
1.1 This specification covers tin-coated copper-clad steel
as Electrical Conductors
wire for electronic application.
B452 Specification for Copper-Clad Steel Wire for Elec-
1.2 Four classes of tin-coated copper-clad steel wire are
tronic Application
covered as follows:
2.3 National Institute of Standards and Technology:
1.2.1 Class T30HS— Nominal 30 % conductivity, hard-
NBS Handbook 100 Copper Wire Tables
drawn,
1.2.2 Class T30A—Nominal 30 % conductivity, annealed,
3. Ordering Information
1.2.3 Class T40HS— Nominal 40 % conductivity, hard-
3.1 Orders for material under this specification shall include
drawn, and
the following information:
1.2.4 Class T40A—Nominal 40 % conductivity, annealed.
3.1.1 Quantity of each size.
1.3 The values stated in inch-pound units are to be regarded
3.1.2 Wire size (see 5.3 and Table 1),
as the standard. The metric equivalents of inch-pound units
3.1.3 Class of wire (see 1.2),
may be approximate. The values given in parentheses are for
3.1.4 Package size and shipping (see 7.1.7 and Section 9),
information only.
packaging inspection if required (see 9.3.3),
1.4 The following safety hazards caveat pertains only to the 3.1.5 Special package marking, if required, and
test method portion, Section 6, of this specification:This 3.1.6 Place of inspection (see 9.1).
standard does not purport to address all of the safety concerns,
4. Material
if any, associated with its use. It is the responsibility of the user
of this standard to establish appropriate safety and health
4.1 Thebasismaterialshallconsistofcopper-cladsteelwire
practices and determine the applicability of regulatory limita-
conforming to the product description, quality and specifica-
tions prior to use.(Warning—Consideration should be given
tion requirements of Specification B452.
to toxicity and flammability when selecting solvent cleaners.)
4.2 Thetin-coatedwireshallconsistofthebasiswirecoated
2. Referenced Documents with tin. The tin used for coating shall be commercially pure
(Note 1). For purposes of this specification, the tin shall be
2.1 The following documents of the issue in effect on date
considered“ commercially pure” if the total of other elements,
of material purchase form a part of this specification to the
exclusive of copper, does not exceed 1 %. Notwithstanding the
extent referenced herein:
previoussentence,chemicalanalysisofthetincoatingorofthe
2.2 ASTM Standards:
tin used for coating shall not be required under this specifica-
B193 Test Method for Resistivity of Electrical Conductor
tion.Adequacyofthetincoatingisassuredbythecontinuityof
Materials
coating and adherence of coating requirements (see 5.4 and
5.5). The quality of the tin-coated wire shall be such that the
This specification is under the jurisdiction of ASTM Committee B01 on
finished product meets the properties and requirements in this
Electrical Conductors and is the direct responsibility of Subcommittee B01.06 on
specification.
Composite Conductors.
Current edition approved Oct. 1, 2007. Published October 2007. Originally
NOTE 1—It is necessary that the coating of the tin on the wire be
´1
approved in 1970. Last previous edition approved in 2002 as B520 – 70 (2002)
continuous. The test in the sodium polysulfide is for the purpose of
DOI: 10.1520/B0520-93R07.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available from National Institute of Standards and Technology (NIST), 100
the ASTM website. Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http://www.nist.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B520−93 (2007)
TABLE 1 Wire Sizes TABLE 2 Resistivity, max at 20°C
Diameter Cross-Sectional Area at 20°C (68°F) Class of Nominal Diameter, in.
V·mm /m
Wire (mm)
2 2
in. mm cmil in. mm
T30HS 0.0720 (1.829) to 0.06743
0.0720 1.8129 5180 0.00407 2.63
0.0201 (0.511) incl (0.067427)
0.0641 1.6128 4110 0.00323 2.08
and under 0.0201 (0.511) to 0.07315
0.0571 1.450 3260 0.00256 1.65
0.0113 (0.287) incl (0.073148)
0.0508 1.290 2580 0.00203 1.31
T30A under 0.0113 (0.287) to 0.07642
0.0453 1.151 2050 0.00161 1.04
0.0031 (0.079) incl (0.076423)
0.0403 1.024 1620 0.00128 0.823
T40HS 0.0720 (1.829) to 0.04874
0.0359 0.912 1290 0.00101 0.653
0.0201 (0.511) incl (0.048742)
0.0320 0.813 1020 0.000804 0.519
and under 0.0201 (0.511) to 0.05162
0.0285 0.724 812 0.000638 0.412
0.0113 (0.287) incl (0.051618)
0.0253 0.643 640 0.000503 0.324
T40A under 0.0113 (0.287) to 0.05328
0.0226 0.574 511 0.000401 0.259
0.0031 (0.079) incl (0.053280)
0.0201 0.511 404 0.000317 0.205
0.0179 0.455 320 0.000252 0.162
0.0159 0.404 253 0.000199 0.128
copper bar 1 cm in cross section.Acomplete discussion of this subject is
0.0142 0.361 202 0.000158 0.102
contained in NBS Handbook 100. The use of five significant figures in
0.0126 0.320 159 0.000125 0.0804
expressing resistivity does not imply the need for greater accuracy of
0.0113 0.287 128 0.000100 0.0647
measurement than that specified in Test Method B193. The use of five
0.0100 0.254 100 0.0000785 0.0507
significant figures is required for complete reversible conversion from one
0.0089 0.226 79.2 0.0000622 0.0401 set of resistivity units to another.
0.0080 0.203 64.0 0.0000503 0.0324
5.3 Dimensions and Permissible Variations—The wire sizes
0.0071 0.180 50.4 0.0000396 0.0255
0.0063 0.160 39.7 0.0000312 0.0201
shall be expressed as the diameter of the wire in decimal
0.0056 0.142 31.4 0.0000246 0.0159
fractions of an inch to the nearest 0.0001 in. (0.003 mm) (Note
0.0050 0.127 25.0 0.0000196 0.0127
3). For diameters under 0.0100 in. (0.254 mm), the wire shall
0.0045 0.114 20.2 0.0000159 0.0103 not vary from the specified diameter by more than plus 0.0003
0.0040 0.102 16.0 0.0000126 0.00811
in. (0.008 mm) and minus 0.0001 in. (0.003 mm) and for
0.0035 0.089 12.2 0.00000962 0.00621
diameters of 0.0100 in. (0.254 mm) and over, the wire shall not
0.0031 0.079 9.61 0.00000755 0.00487
vary from the specified diameter by more than plus 3 % and
minus 1 %, expressed to the nearest 0.0001 in. (0.003 mm).
determining whether or not the wire carries a continuous envelope of pure
NOTE 3—The values of the wire diameters in Table 1 are given to the
tin. The thickness of the tin coating is necessarily varied. Under the same
nearest 0.0001 in. (0.003 mm) and correspond to the standard sizes given
conditions of tinning, the coating on all sizes of wire, excepting on fine
inSpecificationB258.Theuseofgagenumberstospecifywiresizesisnot
wire, is approximately the same. The coating on fine wire is in general
recognized in this specification because of the possibility of confusion.An
relatively heavier than that on coarse wire. It is not, therefore, correct to
excellent discussion of wire gages and related subjects is contained in
apply a larger number of cycles in the test on coarse wire than is applied
“Copper Wire Tables” NBS Handbook 100.
to fine wire. It is probable that one cycle of the dip test would be sufficient
5.4 Continuity of Coating—The tin coating shall be continu-
to discover defects in tinned wire, but in order to make certain that no
partially covered spots may escape attention, provision has been made for
ous. The continuity of coating on the wire shall be determined
two cycles. It has been found that the tin coating on copper wire consists
on representative samples taken before stranding or insulating.
of two parts, an envelope of pure tin on the outside, with an intermediate
The continuity of tinning shall be determined by the hydro-
layer of copper-tin alloy. This tin alloy, as well as the amount of tin
chloric acid-sodium polysulfide test in accordance with 6.2.
present, has an effect on the resistivity of the wire. Since the relative
amount of tin coating and alloy is greater on the small wire than it is on
5.5 Adherence of Coating—The tin coating shall be firmly
the coarser wire, the resistivity of the wire increases as the size decreases.
adherent to the surface of the copper-clad steel wire. The
This also accounts for the decrease in elongation due to tinning soft wire.
adherence of coating on the wire shall be determined on
5. General Requirements representative samples taken before stranding or insulating.
The adherence of coating shall be determined by the wrapping
5.1 Tensile strength and elongation of the tin-coated wire
and immersion test in accordance with 6.3.
shallconformtotherequirementsofSpecificationB452forthe
applicable size and class of copper-clad steel wire. 5.6 Joints—Necessary joints in the wire and rods prior to
final coating and drawing shall be made in accordance with
5.2 Resistivity—Theelectricalresistivityatatemperatureof
good commercial practice. Joints made after coating shall not
20°C shall not exceed the values prescribed in Table 2. See
be allowed to remain in the final product.
Note 2 for calculating electrical resistance.
5.7 Finish—The coating shall consist of a smooth, continu-
NOTE2—Relationshipsthatmaybeusefulinconnectionwiththevalues
ouslayer,firmlyadherenttothesurfaceofthecopper.Thewire
of electrical resistivity prescribed in this specification are shown in Table
2 2
shall be bright and free from all imperfections not consistent
3. Resistivity units ⁄58 Ω·mm /m and 0.15328 Ω · g/m at 20°C are
respectively the international equivalent of volume and weight resistivity
with good commercial practice.
of annealed copper equal to 100 % conductivity. The latter term means
that a copper wire1min length and weighing 1 g would have a resistance
6. Test Methods
of 0.15328Ω. This is equivalent to a resistivity value of 875.20Ω·lb/mile
6.1 For tensile strength, elongation, resistivity, dimensional
2,whichsignifiestheresistanceofacopperwire1mileinlengthweighing
1 lb. It is also equivalent, for example, to 1.7241 µΩ/cm of length of a measurement and the quality of the basis wire, the latest issue
B520−93 (2007)
TABLE 3 Equivalent Resistivity Values
Volume Resistivity Equivalents at 20°C
Conductivity
Class and Size, in. (mm) Volume Mass
at 20°C
2 2 2
% IACS V·mm /m V·c mil/ft µV·in. µV·cm V·lb/mile V·g/m
T30A and T30HS 0.0720
25.570 0.067427 40.56 2.6546 6.7427 3137.9 0.54953
(1.829) to 0.0201 (0.511)
Under 0.0201 (0.511) to
23.570 0.073148 44.00 2.8799 7.3148 3404.1 0.59616
0.0113 (0.287)
Under 0.0113 (0.287) to
22.560 0.076423 45.97 3.0088 7.6423 3556.5 0.62285
0.0031 (0.079)
T40A and T40HS 0.0720
35.372 0.048742 29.32 1.9190 4.8742 2268.3 0.39725
(1.829) to 0.0201 (0.511)
Under 0.0201 (0.511) to
33.401 0.051618 31.05 2.0322 5.1618 2402.2 0.42069
0.0113 (0.287)
Under 0.0113 (0.287) to
32.359 0.053280 32.05 2.0977 5.3280 2479.5 0.43423
0.0031 (0.079)
of Specification B452 shall apply and the tests shall be sulfur (in excess of 250 g/L of solution) to provide complete
performed on the tin-coated wire. saturation, as shown by the presence in the solution of an
excess of sulfur after the solution has been allowed to stand for
6.2 Continuity of Coating:
at least 24 h. The test solution shall be made by diluting a
6.2.1 Specimens:
portion of the concentrated solution with distilled water to a
6.2.1.1 Length of Specimens—Test specimens shall each
specific gravity of 1.142 at 15.6°C (60°F). The sodium poly-
have a length of about 6 in. (150 mm). They shall be tagged or
sulfide test solution should have sufficient strength to blacken
marked to correspond with the coil, spool, or reel from which
thoroughly a piece of clean untinned copper wire in 5 s. A
they were cut.
portion of the test solution used for testing samples shall not be
6.2.1.2 Treatment of Specimens—The specimens shall be
considered to be exhausted until it fails to blacken a piece of
thoroughly cleaned by immersion in a suitable organic solvent
clean copper as described above.
such as benzene, ether, or trichloroethylene for at least 3 min,
then removed and wiped dry with a clean, soft cloth.
NOTE 4—It is important that the polysulfide solution be of proper
(Warning—See1.4.)Thespecimensthuscleanedshallbekept composition and strength at the time of test. A solution which is not
saturated with sulfur or which has been made from decomposed sodium
wrapped in a clean, dry cloth until tested. That part of the
sulfide crystals may give a false indication of failure. Therefore, the
specimen to be immersed in the test solution shall not be
requirement that the solution be tested by observing its blackening effect
handled. Care shall be taken to avoid abrasion by the cut ends.
on a bright copper wire is significant. Significant also is the requirement
6.2.2 Special Solutions:
that the solution be saturated with sulfur by allowing the solution to stand
6.2.2.1 Hydrochloric Acid Solution (sp gr 1.088)— at least 24 h after preparation.Attention is called also to the necessity for
the use of sodium sulfide which has not deteriorated through exposure to
Commercial HCl (sp gr 1.12) shall be diluted with distilled
air; and if exposure has occurred, the crystals should be tested for purity.
water to a specific gravity of 1.088 measured at 15.6°C (60°F).
The “Standard Reagents Tests” of the American Chemical Society are
Aportion of HCl solution having a volume of 180 mLshall be
useful in this connection.
considered to be exhausted when the number of test specimens
6.2.3 Procedure:
prescribed in Table 4 of a size as indicated in 6.2.3 have been
6.2.3.1 Immersion of Specimens—Immerse a length of at
immersed in it for two cycles.
least 4 ⁄2 in. (115 mm) from each of the clean specimens, in
6.2.2.2 Sodium Polysulfide Solution (sp gr 1.142) (Note
accordance with the following cycles, in test solutions main-
4)—A concentrated solution shall be made by dissolving
tained at a temperature between 15.6 and 21°C (60 and 70°F):
sodium sulfide cp crystals in distilled water until the solution is
(1) immerse the specimen for 1 min in the HCl solution
saturatedatabout21°C(70°F),andaddingsufficientflowersof
described in 6.2
...
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