1、Designation: B942 10 (Reapproved 2015)Standard Guide forSpecification and Quality Assurance for the ElectricalContact Performance of Crimped Wire Terminations1This standard is issued under the fixed designation B942; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide contains practices for specifying and evalu-ating the electri
3、cal contact performance of crimped-type ter-minations with solid or stranded conductors.1.2 This guide provides information relevant to the electri-cal contact performance of a crimped wire termination. It doesnot cover other aspects of selection and use of crimpedterminals.1.3 The methods discussed
4、 in this guide apply only to thewire termination, which is the electrical contact interfacebetween the conductor(s) and the terminal. Other aspectsimportant to terminal evaluation, such as the properties andperformance of electrical insulation, the effectiveness of strainrelief features, and the qua
5、lity of contact between the terminaland other electrical circuit elements, are not included.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, ass
6、ociated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateSafety Data Sheet (SDS) for this product/material as providedby the manufacturer, to establish appropriate safety and healthpractices, and determ
7、ine the applicability of regulatory limi-tations prior to use.2. Referenced Documents2.1 ASTM Standards:2B539 Test Methods for Measuring Resistance of ElectricalConnections (Static Contacts)B542 Terminology Relating to Electrical Contacts and TheirUseB827 Practice for Conducting Mixed Flowing Gas (M
8、FG)Environmental TestsB845 Guide for Mixed Flowing Gas (MFG) Tests for Elec-trical ContactsB868 Practice for Contact Performance Classification ofElectrical Connection SystemsB913 Test Method for Evaluation of Crimped ElectricalConnections to 16-Gauge and Smaller Diameter Strandedand Solid Conductor
9、sE122 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or Process2.2 Other References:3UL 486-A Wire connectors and Soldering Lugs for Use WithCopper ConductorsUL-310 Electrical Quick-Connect Terminals3. Terminology3.1 Many terms rel
10、ated to electrical contacts used in thisguide are defined in Terminology B542.3.2 Definitions of Terms Specific to This Standard:3.2.1 connection resistance, nthe electrical resistance at-tributable to a wire termination over and above that of anidentical solid metallic structure without pressure co
11、ntactinterfaces. For crimped terminations that are the subject of thisguide, the connection resistance results from the resistance ofa multitude of contact regions having both film and constrictionresistance, plus, where stranded wire is involved, an additionalamount due to unequal current distribut
12、ion among the wirestrands at the termination.3.2.2 crimp, vto establish an electrical and mechanicalattachment between the two members by mechanically deform-ing one contact member around another. In most cases, onemember is a stranded or solid wire, or a group of wires, theother is a hollow cylinde
13、r or partial cylinder that is deformedaround the wire(s).3.2.3 crimp barrel, crimp tab, nthe portion of the crimpterminal that is deformed in the crimping operation.1This guide is under the jurisdiction of ASTM Committee B02 on NonferrousMetals and Alloys and is the direct responsibility of Subcommi
14、ttee B02.11 onElectrical Contact Test Methods.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 2005. Last previous edition approved in 2010 as B972 101. DOI:10.1520/B0942-10R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cu
15、stomer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Underwriters Laboratories Inc. (UL), http:/.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
16、19428-2959. United States13.2.4 crimped termination, na mechanical and electricalconnection between a conductor, generally a wire, and acomponent, typically a terminal specifically made for thepurpose. The crimped termination is made by compressing(crimping) the component (crimp barrel) or tab(s) of
17、 thecomponent around the conductor using a tool specificallydesigned for the purpose.3.2.5 crimp terminal, na metal component designed to beelectrically and mechanically attached to a wire by deforminga portion of the component in a crimping operation to form anattachment to the wire. The other end
18、of the terminal usuallyhas a ring, fork, spade, tab, or related configuration designed toattach to another circuit element. Some crimp terminals termi-nate multiple wires within the same crimp barrel.4. Significance and Use4.1 The purpose of this guide is to provide end-productmanufacturers and othe
19、r users with technical information andmethods recommended towards the achievement of successfulapplication of crimped wire terminals.4.2 For any given use, there is generally a choice of terminaltypes available, employing different mechanical design,materials, and installation tooling. Although term
20、inals avail-able to choose from may be similarly rated, typically accordingto wire sizes and combinations, their electrical contact perfor-mance in the end product may vary substantially. For manyapplications, the end-product reliability and user safety issubstantially influenced by the choice of te
21、rminal and thequality of the completed termination. This guidance documentcontains specialized information on selection, assembly, andquality control of crimped wire terminals, covering aspectsconsidered to be necessary to achieve reliable long-termoperation in the intended application. This informa
22、tion is notgenerally found in commercial literature or textbooks. Themethods discussed utilize connection resistance as the primarymeasure of termination quality, and change of connectionresistance with time as the measure of termination deteriora-tion. The methods are based on a foundation of moder
23、nelectrical contact theory and practice.5. Connection Resistance Considerations5.1 The required performance of a crimped wire terminationdepends on the application, and it must be determined by theuser or end-product manufacturer based on the effect thatconnection resistance may have on the reliabil
24、ity or safety, orboth, of the end product. To satisfy the more demandingapplication requirements, it is necessary to establish adequateinitial metallic contact at the wire-to-connector interface andmaintain that contact over many decades of service withoutmaintenance or inspections.5.2 A crimped wir
25、e termination is intended to be a perma-nent electrical contact. Current passes through a multitude ofcontact interfaces among the wire strands and from some of thestrands to the connector body.5.3 In many applications, substantial connection deteriora-tion can be tolerated because there are no harm
26、ful conse-quences of increasing connection resistance. Crimp termina-tion failures in other applications have potentially severeconsequences, however, which may be avoided by use ofstringent acceptance criteria and quality control methods thatassure high quality connections.5.4 A crimp termination i
27、s conceptually visualized as com-pressed into a virtually solid mass of metal, with wire andterminal in intimate contact at the interfaces. Because of aneffect generally called “spring-back,” this is often incorrect.Spring-back is the elastic recovery of the distorted metal backtowards its original
28、shape. While the crimping dies are closedon the terminal, the surfaces are in contact. Spring-back thenoccurs when the crimping die is removed.5.5 If the outer terminal springs back more than the wirestrands, then the normal force and the real area of contact at thecontact interfaces within the term
29、ination are substantiallyreduced. When this occurs, there may be little or no residualcompressive force at the contact interfaces within the termina-tion. This degrades the mechanical integrity of the terminationand also makes it more susceptible to corrosive deterioration.Spring-back causes open sp
30、aces to develop where intimatesurface-to-surface contact is expected, allowing ingress ofmoisture and atmospheric contaminants, thereby acceleratingoxidation and corrosion related deterioration.5.6 The selection and setup of the correct die set for theparticular terminal are critical factors. For a
31、given terminal andwire fill, there is a narrow range of compression within whichsatisfactory results will be obtained. Inadequate crimpinggenerally results in shortened service life. Over-crimping mayalso be harmful, due to crack formation in the crimp barrel,severing of wire strands, or excessive d
32、eformation of the wire.5.7 The typical connection resistance of crimped wire ter-minations when initially made will be low, about the sameorder of magnitude as the bulk resistance of the terminal. Anewly-made termination of #16AWG stranded copper wire, forexample, is expected to have a connection re
33、sistance of lessthan 10-4 (0.1 milliohm). Deterioration at the metalliccontact interfaces within the crimped termination may occurafter initial installation, causing increasing connection resis-tance with time in service. Termination deterioration may bedue to oxidation, corrosion, mechanical and/or
34、 thermal effects,any of which may occur within the normal and expectedconditions of use in a particular application.5.8 Increasing connection resistance of terminations in aparticular end-product may influence reliability or safety, orboth, depending on the particular function and current for eachcr
35、imped termination in the circuit. Within a given product,there may be crimp terminations having substantially differentreliability and safety requirements.5.8.1 An example is a portable heater intended for retail saleand residential use. There are eight crimped wire terminationsin the units internal
36、 wiring that are in series with the heatingelement, which draws 12 A. There are also seven crimped wireterminations associated with neon indicator lights (less than0.01 A), and another four in the heaters blower motor circuit(1.2 A). (Note: there may be more than one subcircuitterminated within a si
37、ngle crimp fitting.) The influence ofconnection resistance on reliability and safety for each of theB942 10 (2015)2crimped termination types in this example heater is outlined inTable 1. Adverse consequences of connection resistance in-crease are generally more severe with higher circuit current.5.8
38、.2 Asecond example is a temperature sensitive control orsafety device, on which the effective operating set point may besubstantially offset due to self heating (I2R) at its wireterminals. For instance, a manually-reset thermal safety devicemay erroneously trip due to connection heating, causingmalf
39、unction of the product or system in which it is installed.5.9 Factors Influencing Connection Resistance:5.9.1 Acceptably low initial resistance of crimp termina-tions is very easily achieved. To assure that it will remainacceptably low in the intended application is the greaterchallenge, since the r
40、ate of deterioration (resistance increase)in service is sensitive to many variables of the terminal/wire/tooling system.5.9.1.1 Terminal variables include the physicalconfiguration, the materials of construction (including plating)and their properties, and the surface finish.5.9.1.2 Conductor variab
41、les include the material, hardness,plating material and thickness, stranding, and surface cleanli-ness. If wire strands are to be pre-tinned, it is especiallyimportant to specify and control the thickness, since mosttinning materials are self-annealing at room temperature. If thetinning is too thick
42、, loss of contact force due to self-annealing(or creep/stress relaxation) may result in premature failure.5.9.1.3 Tooling variables include selection of the tooling(dies and associated crimping tool or machine), its setup, itsoperation, and its wear and maintenance.5.10 The rate of deterioration is
43、also influenced by theenvironmental and mechanical conditions of the application.5.10.1 Deterioration due to corrosion and oxidation canoccur in ordinary environment, and is generally accelerated byhigh temperature and high humidity. Corrosive agents arepresent in the normal atmosphere as well as in
44、 specialindustrial and household situations.5.10.2 Temperature variations in service may cause deterio-ration due to differential thermal expansion effects (causingfretting and thermal ratcheting), while extreme high tempera-ture can result in metallurgical changes (dezincification ofbrass, annealin
45、g) and loss of contact force (creep, stressrelaxation). The specific operating conditions in many commonapplications impose harsh thermal conditions, such as in theengine wiring harness of an automobile, or at the terminal of aheating element.5.10.3 Deterioration may also occur due to mechanicalvibr
46、ations (causing fretting) and due to mechanical motionsand stresses that cause conductor strand breakage.6. Specification of Required Crimp TerminationPerformance6.1 The sensitivity of each particular circuit to connectionresistance of its crimp terminations must be assessed, and amaximum allowable
47、connection resistance must be specified.Connection resistance is a series resistance, and, in a newly-made wire termination, is generally negligible, of the order ofless than 0.001 . With time in service, however, or if poorlymade, connection resistance may exceed 1 .6.1.1 Relatively high series res
48、istance of one or more crimpterminations in a circuit may have an adverse effect on thecircuits functionality. For example, some battery chargers willmalfunction (improperly regulate the charging cycle) if a seriesresistance of the order of 0.1 or more is introduced in theoutput circuit.6.1.2 Resist
49、ive heating (I2R) at a high resistance terminationmay have an adverse effect on both the functionality and alsoon the safety of the product.6.1.2.1 An example of thermally-induced malfunction dueto excessive crimp termination resistance is at a manually resetover-temperature cutout device in a portable electric heater.Normally, with connection resistance of the order of 0.0001 ,at 12 amps, the I2R heating from the two crimp terminations onthe device (0.03 W) results in a negligible temperature increaseat its temperature sensing element. If the connection resi
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