1、Designation: B942 101Standard 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 adoption or, in the c
2、ase 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.1NOTEA Summary of Changes was added editorially in January 2011.1. Scope*1.1 This guide contains prac
3、tices for specifying and evalu-ating the electrical 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 u
4、se of crimpedterminals.1.3 The methods discussed 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 eff
5、ectiveness of strainrelief features, and the quality 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 t
6、o address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to become familiarwith all hazards including those identified in the appropriateMaterial Safety Data Sheet (MSDS) for this product/materialas provided by the manufacturer, to es
7、tablish appropriatesafety and health practices, and determine the applicability ofregulatory limitations 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 andTh
8、eir UseB827 Practice for Conducting Mixed Flowing Gas (MFG)Environmental TestsB845 Guide for Mixed Flowing Gas (MFG) Tests forElectrical ContactsB868 Practice for Contact Performance Classification ofElectrical Connection SystemsB913 Test Method for Evaluation of Crimped ElectricalConnections to 16-
9、Gauge and Smaller Diameter Strandedand Solid ConductorsE122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or Process2.2 Other References:3UL 486-A Wire connectors and Soldering Lugs for UseWith Copper ConductorsUL-310 Electrical Q
10、uick-Connect Terminals3. Terminology3.1 Many terms related 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 an
11、identical solid metallic structure without pressure contactinterfaces. 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
12、, an additionalamount due to unequal current distribution 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 w
13、ire, or a group of wires, theother is a hollow cylinder or partial cylinder that is deformedaround the wire(s).1This guide is under the jurisdiction of ASTM Committee B02 on NonferrousMetals and Alloys and is the direct responsibility of Subcommittee B02.11 onElectrical Contact Test Methods.Current
14、edition approved Oct. 1, 2010. Published October 2010. Originallyapproved in 2005. Last previous edition approved in 2005 as B972 - 05. DOI:10.1520/B0942-10E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
15、 ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Underwriters Laboratories Inc. (UL), http:/.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Con
16、shohocken, PA 19428-2959, United States.3.2.3 crimp barrel, crimp tab, nthe portion of the crimpterminal that is deformed in the crimping operation.3.2.4 crimped termination, na mechanical and electricalconnection between a conductor, generally a wire, and acomponent, typically a terminal specifical
17、ly made for thepurpose. The crimped termination is made by compressing(crimping) the component (crimp barrel) or tab(s) of 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
18、 to a wire by deforminga portion of the component in a crimping operation to form anattachment to the wire. The other end 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
19、the same crimp barrel.4. Significance and Use4.1 The purpose of this guide is to provide end-productmanufacturers and other 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 c
20、hoice of terminaltypes available, employing different mechanical design, mate-rials, and installation tooling. Although terminals available tochoose from may be similarly rated, typically according to wiresizes and combinations, their electrical contact performance inthe end product may vary substan
21、tially. For many applications,the end-product reliability and user safety is substantiallyinfluenced by the choice of terminal and the quality of thecompleted termination. This guidance document contains spe-cialized information on selection, assembly, and quality controlof crimped wire terminals, c
22、overing aspects considered to benecessary to achieve reliable long-term operation in the in-tended application. This information is not generally found incommercial literature or textbooks. The methods discussedutilize connection resistance as the primary measure of termi-nation quality, and change
23、of connection resistance with timeas the measure of termination deterioration. The methods arebased on a foundation of modern electrical contact theory andpractice.5. Connection Resistance Considerations5.1 The required performance of a crimped wire terminationdepends on the application, and it must
24、 be determined by theuser or end-product manufacturer based on the effect thatconnection resistance may have on the reliability 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-c
25、onnector interface andmaintain that contact over many decades of service withoutmaintenance or inspections.5.2 A crimped wire 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 t
26、he connector body.5.3 In many applications, substantial connection deteriora-tion can be tolerated because there are no harmful conse-quences of increasing connection resistance. Crimp termina-tion failures in other applications have potentially severeconsequences, however, which may be avoided by u
27、se ofstringent acceptance criteria and quality control methods thatassure high quality connections.5.4 A crimp termination is 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
28、 “spring-back,” this is often incorrect.Spring-back is the elastic recovery of the distorted metal backtowards its original 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
29、 back more than the wirestrands, then the normal force and the real area of contact at thecontact interfaces within the termination are substantiallyreduced. When this occurs, there may be little or no residualcompressive force at the contact interfaces within the termina-tion. This degrades the mec
30、hanical integrity of the terminationand also makes it more susceptible to corrosive deterioration.Spring-back causes open spaces to develop where intimatesurface-to-surface contact is expected, allowing ingress ofmoisture and atmospheric contaminants, thereby acceleratingoxidation and corrosion rela
31、ted deterioration.5.6 The selection and setup of the correct die set for theparticular terminal are critical factors. For a given terminal andwire fill, there is a narrow range of compression within whichsatisfactory results will be obtained. Inadequate crimpinggenerally results in shortened service
32、 life. Over-crimping mayalso be harmful, due to crack formation in the crimp barrel,severing of wire strands, or excessive deformation 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 resista
33、nce of the terminal. Anewly-made termination of #16AWG stranded copper wire, forexample, is expected to have a connection resistance of lessthan 10-4V (0.1 milliohm). Deterioration at the metallic contactinterfaces within the crimped termination may occur afterinitial installation, causing increasin
34、g connection resistancewith time in service. Termination deterioration may be due tooxidation, corrosion, mechanical and/or thermal effects, any ofwhich may occur within the normal and expected conditions ofuse in a particular application.5.8 Increasing connection resistance of terminations in apart
35、icular end-product may influence reliability or safety, orboth, depending on the particular function and current for eachcrimped 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
36、portable heater intended for retail saleand residential use. There are eight crimped wire terminationsin the units internal 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
37、another four in the heaters blower motor circuit(1.2 A). (Note: there may be more than one subcircuitterminated within a single crimp fitting.) The influence ofconnection resistance on reliability and safety for each of thecrimped termination types in this example heater is outlined inB942 1012Table
38、 1. Adverse consequences of connection resistance in-crease are generally more severe with higher circuit current.5.8.2 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 wiretermi
39、nals. For instance, a manually-reset thermal safety devicemay erroneously trip due to connection heating, causingmalfunction 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 a
40、chieved. To assure that it will remainacceptably low in the intended application is the greaterchallenge, since the rate 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 physical configura-tion,
41、 the materials of construction (including plating) and theirproperties, and the surface finish.5.9.1.2 Conductor variables 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 an
42、d control the thickness, since mosttinning materials are self-annealing at room temperature. If thetinning is too thick, 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 associa
43、ted crimping tool or machine), its setup, itsoperation, and its wear and maintenance.5.10 The rate of deterioration is 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 general
44、ly accelerated byhigh temperature and high humidity. Corrosive agents arepresent in the normal atmosphere as well as in specialindustrial and household situations.5.10.2 Temperature variations in service may cause deterio-ration due to differential thermal expansion effects (causingfretting and ther
45、mal ratcheting), while extreme high tempera-ture can result in metallurgical changes (dezincification ofbrass, annealing) and loss of contact force (creep, stressrelaxation). The specific operating conditions in many commonapplications impose harsh thermal conditions, such as in theengine wiring har
46、ness of an automobile, or at the terminal of aheating element.5.10.3 Deterioration may also occur due to mechanicalvibrations (causing fretting) and due to mechanical motionsand stresses that cause conductor strand breakage.6. Specification of Required Crimp TerminationPerformance6.1 The sensitivity
47、 of each particular circuit to connectionresistance of its crimp terminations must be assessed, and amaximum allowable 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
48、V. With time in service, however, or if poorlymade, connection resistance may exceed 1 V.6.1.1 Relatively high series resistance of one or more crimpterminations in a circuit may have an adverse effect on thecircuits functionality. For example, some battery chargers willmalfunction (improperly regul
49、ate the charging cycle) if a seriesresistance of the order of 0.1 V or more is introduced in theoutput circuit.6.1.2 Resistive 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 V,at 12 amps, the I2R heating from the two crimp terminations ont
