ASTM B942-05
(Guide)Standard Guide for Specification and Quality Assurance for the Electrical Contact Performance of Crimped Wire Terminations
Standard Guide for Specification and Quality Assurance for the Electrical Contact Performance of Crimped Wire Terminations
SIGNIFICANCE AND USE
The purpose of this guide is to provide end-product manufacturers and other users with technical information and methods recommended towards the achievement of successful application of crimped wire terminals.
For any given use, there is generally a choice of terminal types available, employing different mechanical design, materials, and installation tooling. Although terminals available to choose from may be similarly rated, typically according to wire sizes and combinations, their electrical contact performance in the end product may vary substantially. For many applications, the end-product reliability and user safety is substantially influenced by the choice of terminal and the quality of the completed termination. This guidance document contains specialized information on selection, assembly, and quality control of crimped wire terminals, covering aspects considered to be necessary to achieve reliable long-term operation in the intended application. This information is not generally found in commercial literature or textbooks. The methods discussed utilize connection resistance as the primary measure of termination quality, and change of connection resistance with time as the measure of termination deterioration. The methods are based on a foundation of modern electrical contact theory and practice.
SCOPE
1.1 This guide contains practices for specifying and evaluating the electrical contact performance of crimped-type terminations with solid or stranded conductors.
1.2 This guide provides information relevant to the electrical contact performance of a crimped wire termination. It does not cover other aspects of selection and use of crimped terminals.
1.3 The methods discussed in this guide apply only to the wire termination, which is the electrical contact interface between the conductor(s) and the terminal. Other aspects important to terminal evaluation, such as the properties and performance of electrical insulation, the effectiveness of strain relief features, and the quality of contact between the terminal and other electrical circuit elements, are not included.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 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 become familiar with all hazards including those identified in the appropriate Material Safety Data Sheet (MSDS) for this product/material as provided by the manufacturer, to establish appropriate safety and health practices, and determine the applicability of regulatory limitations prior to use.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: B942 – 05
Standard Guide for
Specification and Quality Assurance for the Electrical
Contact Performance of Crimped Wire Terminations
This standard is issued under the fixed designation B942; 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.
1. Scope Environmental Tests
B845 Guide for Mixed Flowing Gas (MFG) Tests for
1.1 This guide contains practices for specifying and evalu-
Electrical Contacts
ating the electrical contact performance of crimped-type ter-
B868 Practice for Contact Performance Classification of
minations with solid or stranded conductors.
Electrical Connection Systems
1.2 This guide provides information relevant to the electri-
B913 Test Method for Evaluation of Crimped Electrical
cal contact performance of a crimped wire termination. It does
Connections to 16-Gauge and Smaller Diameter Stranded
not cover other aspects of selection and use of crimped
and Solid Conductors
terminals.
E122 Practice for Calculating Sample Size to Estimate,
1.3 The methods discussed in this guide apply only to the
With Specified Precision, the Average for a Characteristic
wire termination, which is the electrical contact interface
of a Lot or Process
between the conductor(s) and the terminal. Other aspects
2.2 Other References:
important to terminal evaluation, such as the properties and
UL 486-A Wire connectors and Soldering Lugs for Use
performance of electrical insulation, the effectiveness of strain
With Copper Conductors
relief features, and the quality of contact between the terminal
UL-310 Electrical Quick-Connect Terminals
and other electrical circuit elements, are not included.
1.4 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Many terms related to electrical contacts used in this
standard.
guide are defined in Terminology B542.
1.5 This standard does not purport to address all of the
3.2 Definitions of Terms Specific to This Standard:
safety concerns, if any, associated with its use. It is the
3.2.1 connection resistance, n—the electrical resistance at-
responsibility of the user of this standard to become familiar
tributable to a wire termination over and above that of an
with all hazards including those identified in the appropriate
identical solid metallic structure without pressure contact
Material Safety Data Sheet (MSDS) for this product/material
interfaces. For crimped terminations that are the subject of this
as provided by the manufacturer, to establish appropriate
guide, the connection resistance results from the resistance of
safety and health practices, and determine the applicability of
amultitudeofcontactregionshavingbothfilmandconstriction
regulatory limitations prior to use.
resistance, plus, where stranded wire is involved, an additional
2. Referenced Documents amount due to unequal current distribution among the wire
strands at the termination.
2.1 ASTM Standards:
3.2.2 crimp, v—to establish an electrical and mechanical
B539 Test Methods for Measuring Resistance of Electrical
attachmentbetweenthetwomembersbymechanicallydeform-
Connections (Static Contacts)
ing one contact member around another. In most cases, one
B542 Terminology Relating to Electrical Contacts and
member is a stranded or solid wire, or a group of wires, the
Their Use
other is a hollow cylinder or partial cylinder that is deformed
B827 Practice for Conducting Mixed Flowing Gas (MFG)
around the wire(s).
3.2.3 crimp barrel, crimp tab, n—the portion of the crimp
terminal that is deformed in the crimping operation.
This guide is under the jurisdiction of ASTM Committee B02 on Nonferrous
3.2.4 crimped termination, n—a mechanical and electrical
Metals and Alloys and is the direct responsibility of Subcommittee B02.11 on
Electrical Contact Test Methods.
connection between a conductor, generally a wire, and a
Current edition approved Nov. 1, 2005. Published December 2005. DOI:
component, typically a terminal specifically made for the
10.1520/B0942-05.
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 Underwriters Laboratories (UL), Corporate Progress, 333
the ASTM website. Pfingsten Rd., Northbrook, IL 60062.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
B942 – 05
purpose. The crimped termination is made by compressing 5.4 A crimp termination is conceptually visualized as com-
(crimping) the component (crimp barrel) or tab(s) of the pressed into a virtually solid mass of metal, with wire and
component around the conductor using a tool specifically terminal in intimate contact at the interfaces. Because of an
designed for the purpose. effect generally called “ spring-back,” this is often incorrect.
Spring-back is the elastic recovery of the distorted metal back
3.2.5 crimp terminal, n—a metal component designed to be
electrically and mechanically attached to a wire by deforming towards its original shape. While the crimping dies are closed
on the terminal, the surfaces are in contact. Spring-back then
a portion of the component in a crimping operation to form an
attachment to the wire. The other end of the terminal usually occurs when the crimping die is removed.
has a ring, fork, spade, tab, or related configuration designed to
5.5 If the outer terminal springs back more than the wire
attach to another circuit element. Some crimp terminals termi-
strands,thenthenormalforceandtherealareaofcontactatthe
nate multiple wires within the same crimp barrel.
contact interfaces within the termination are substantially
reduced. When this occurs, there may be little or no residual
4. Significance and Use
compressive force at the contact interfaces within the termina-
tion. This degrades the mechanical integrity of the termination
4.1 The purpose of this guide is to provide end-product
and also makes it more susceptible to corrosive deterioration.
manufacturers and other users with technical information and
Spring-back causes open spaces to develop where intimate
methods recommended towards the achievement of successful
surface-to-surface contact is expected, allowing ingress of
application of crimped wire terminals.
moisture and atmospheric contaminants, thereby accelerating
4.2 Foranygivenuse,thereisgenerallyachoiceofterminal
oxidation and corrosion related deterioration.
types available, employing different mechanical design, mate-
5.6 The selection and setup of the correct die set for the
rials, and installation tooling. Although terminals available to
particular terminal are critical factors. For a given terminal and
choosefrommaybesimilarlyrated,typicallyaccordingtowire
wire fill, there is a narrow range of compression within which
sizes and combinations, their electrical contact performance in
satisfactory results will be obtained. Inadequate crimping
the end product may vary substantially. For many applications,
generally results in shortened service life. Over-crimping may
the end-product reliability and user safety is substantially
also be harmful, due to crack formation in the crimp barrel,
influenced by the choice of terminal and the quality of the
severing of wire strands, or excessive deformation of the wire.
completed termination. This guidance document contains spe-
cializedinformationonselection,assembly,andqualitycontrol 5.7 The typical connection resistance of crimped wire ter-
of crimped wire terminals, covering aspects considered to be minations when initially made will be low, about the same
necessary to achieve reliable long-term operation in the in- order of magnitude as the bulk resistance of the terminal. A
tended application. This information is not generally found in newly-madeterminationof#16AWGstrandedcopperwire,for
commercial literature or textbooks. The methods discussed example, is expected to have a connection resistance of less
-4
utilize connection resistance as the primary measure of termi- than10 V(0.1milliohm).Deteriorationatthemetalliccontact
nation quality, and change of connection resistance with time interfaces within the crimped termination may occur after
as the measure of termination deterioration. The methods are initial installation, causing increasing connection resistance
based on a foundation of modern electrical contact theory and with time in service. Termination deterioration may be due to
practice. oxidation, corrosion, mechanical and/or thermal effects, any of
which may occur within the normal and expected conditions of
5. Connection Resistance Considerations use in a particular application.
5.8 Increasing connection resistance of terminations in a
5.1 Therequiredperformanceofacrimpedwiretermination
particular end-product may influence reliability or safety, or
depends on the application, and it must be determined by the
both, depending on the particular function and current for each
user or end-product manufacturer based on the effect that
crimped termination in the circuit. Within a given product,
connection resistance may have on the reliability or safety, or
there may be crimp terminations having substantially different
both, of the end product. To satisfy the more demanding
reliability and safety requirements.
application requirements, it is necessary to establish adequate
5.8.1 Anexampleisaportableheaterintendedforretailsale
initial metallic contact at the wire-to-connector interface and
maintain that contact over many decades of service without and residential use. There are eight crimped wire terminations
in the unit’s internal wiring that are in series with the heating
maintenance or inspections.
element, which draws 12A.There are also seven crimped wire
5.2 A crimped wire termination is intended to be a perma-
terminations associated with neon indicator lights (less than
nent electrical contact. Current passes through a multitude of
0.01 A), and another four in the heater’s blower motor circuit
contact interfaces among the copper wire strands and from
(1.2 A). (Note: there may be more than one subcircuit
some of the strands to the connector body.
terminated within a single crimp fitting.) The influence of
5.3 In many applications, substantial connection deteriora-
connection resistance on reliability and safety for each of the
tion can be tolerated because there are no harmful conse-
crimped termination types in this example heater is outlined in
quences of increasing connection resistance. Crimp termina-
Table 1. Adverse consequences of connection resistance in-
tion failures in other applications have potentially severe
crease are generally more severe with higher circuit current.
consequences, however, which may be avoided by use of
stringent acceptance criteria and quality control methods that 5.8.2 Asecondexampleisatemperaturesensitivecontrolor
assure high quality connections. safetydevice,onwhichtheeffectiveoperatingsetpointmaybe
B942 – 05
TABLE 1 Example—Crimp Terminations within a Portable Electric Heater
Maximum Allowable
Circuit Application within Maximum Current, No. of Terminals/ Consequence(s) of Exceeding
Connection Resistance,
Heater Assembly Amps No. of Different Types Maximum Allowable Resistance
Ohms
Main power 13.2 2/1 0.005 damage to wire insulation
Heater element power, general 12 4/2 0.005 damage to wire insulation
Temperature limit switch (heater element power) 12 2/1 0.001 offset of trip point, product malfunction
Blower Motor 1.2 2/1 2.0 motor may fail to start
Indicator Lights nil 7/3 >10 000 indicator light malfunction
substantially offset due to self heating (I R) at its wire Connection resistance is a series resistance, and, in a newly-
terminals. For instance, a manually-reset thermal safety device made wire termination, is generally negligible, of the order of
may erroneously trip due to connection heating, causing less than 0.001 V. With time in service, however, or if poorly
malfunction of the product or system in which it is installed. made, connection resistance may exceed 1 V.
5.9 Factors Influencing Connection Resistance:
6.1.1 Relatively high series resistance of one or more crimp
5.9.1 Acceptably low initial resistance of crimp termina-
terminations in a circuit may have an adverse effect on the
tions is very easily achieved. To assure that it will remain
circuit’s functionality. For example, some battery chargers will
acceptably low in the intended application is the greater
malfunction(improperlyregulatethechargingcycle)ifaseries
challenge, since the rate of deterioration ( resistance increase)
resistance of the order of 0.1 V or more is introduced in the
in service is sensitive to many variables of the terminal/wire/
output circuit.
tooling system.
6.1.2 Resistiveheating(I R)atahighresistancetermination
5.9.1.1 Terminal variables include the physical configura-
may have an adverse effect on both the functionality and also
tion, the materials of construction (including plating) and their
on the safety of the product.
properties, and the surface finish.
6.1.2.1 An example of thermally-induced malfunction due
5.9.1.2 Conductor variables include the material, hardness,
to excessive crimp termination resistance is at a manually reset
plating material and thickness, stranding, and surface cleanli-
over-temperature cutout device in a portable electric heater.
ness. If wire strands are to be pre-tinned, it is especially
Normally, with connection resistance of the order of 0.0001 V,
important to specify and control the thickness, since most
at12amps,theI Rheatingfromthetwocrimpterminationson
tinning materials are self-annealing at room temperature. If the
thedevice(0.03W)resultsinanegligibletemperatureincrease
tinning is too thick, loss of contact force due to self-annealing
at its temperature sensing element. If the connection resistance
(or creep/stress relaxation) may result in premature failure.
increases to 0.01 V at one of the terminations, the resulting
5.9.1.3 Tooling variables include selection of the tooling
heatgeneration(1.4W)causessufficienttemperatureriseatthe
(dies and associated crimping tool or machine), its setup, its
over-temperature device to activate it, incorrectly shutting off
operation, and its wear and maintenance.
the heater.
5.10 The rate of deterioration is also influenced by the
6.1.2.2 A safety problem arises if self-heating at a termina-
en
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