1、Designation: B 542 07Standard Terminology Relating toElectrical Contacts and Their Use1This standard is issued under the fixed designation B 542; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 The terms included in this list are those that are peculiarto electric contacts or general terms that have a specificmeaning when related to e
3、lectric contacts. The definitions wereprepared assuming that the reader has a general knowledge ina physical science but is unfamiliar with the terminology of theliterature of electric contacts.2. Significance and Use2.1 The terms in this standard are used in standards andliterature related to elect
4、ric contacts, materials for electriccontacts and test methods for evaluating electric contacts.These terms may be difficult to locate in a general purposedictionary or the definition in such a dictionary may not coverthe meaning applied in the field of electric contacts.3. Terminologya-spotthe areas
5、 of two mating contacts through whichcurrent flows from one contact to the other.activationa process in which contamination of the surface ofcontacts causes arcing at lower than usual voltage or arcingpersists at lower than usual current, or both. For example,palladium contacts operated in an organi
6、c vapor producearcs at voltage and current less than the minimum arcingvoltage and current because of the presence of carbon on thecontact surfaces.anode fallthe potential difference between the anode and theelectrical discharge plasma.anodic (anode) material transfersee material transfer.arc discha
7、rgea self-sustaining, high current density, hightemperature discharge, uniquely characterized by a cathodefall nearly equal to the ionization potential of the gas orvapor in which it exists.arc, anodethe arc that occurs at less than a critical electrodespacing (see arc, cathode), and results in anod
8、e materialloss.arc, cathodethe arc that occurs at greater than a criticalelectrode spacing (see arc, anode), and results in cathodematerial loss.arc, shortesta limiting state of an arc in which the total arcvoltage approaches the sum of the cathode and anode falls.blowoutthe displacement and lengthe
9、ning of an arc tofacilitate its extinction. The blowout effect can be achievedby a magnetic field, air blast, etc.brusha sliding contact member consisting of one or moresliders (see sliders).cathode fallthe potential difference between the cathode andthe electric discharge plasma.cathodic (cathode)
10、material transfersee material transfer.constriction resistancethe increase in resistance arisingfrom a change in current density distribution. In electriccontacts it is that portion of contact resistance resulting fromthe convergence of current into the a-spots.contact, n(a) a generic term that appl
11、ies to a device or partof a device and that has the capability of completing orinterrupting the flow of an electrical signal in a circuit, (b)may also be used with modifiers such as: electrical contact,arcing contact, noble metal contact, separable contact, etc.contact, adjcontact area, the part of
12、an electrical device thatis actually touching and where the electrical signal isexpected to pass. Contact member, one of the electrical pathparts that can make or break an electrical path.contact, arcingan electrical contact whose primary mode ofwearout occurs on the contacting surfaces as a result
13、of anarc formed between separating or closing contact pairs.contact bouncethe unwanted operation of contacts immedi-ately following intentional operation.contact(s), buttinga type of contacts in which the directionof the motion of the moving contact is perpendicular to thecontact faces. The contacts
14、 close and open with no appre-ciable sliding or rolling action.contact chatterthe unwanted operation of contacts resultingfrom external forces operating on them. For example,vibration may cause contacts to open and close or “chatter.”contact-closing forcethe transient force between contactsduring cl
15、osure. At the first instant of closure this force iszero. It then builds up to a maximum value dependent on theforces and inertia of the contact system and finally stabilizesat the static contact force.1This terminology is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys a
16、nd is the direct responsibility of SubcommitteeB02.91 on Editorial and Terminology.Current edition approved May 1, 2007. Published May 2007. Originallyapproved in 1932. Last previous edition approved in 2004 as B 542 04.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoho
17、cken, PA 19428-2959, United States.contact, compositea contact made of two or more distinctmaterials or alloys bonded to each other. For example, acontact with a facing of a precious metal bonded to abase-metal backing.contact forcethe force to close, maintain, or open contacts.See also insertion fo
18、rce, withdrawal force, and normalforce.contact noisea varying voltage across a pair of electriccontacts due to conditions at their interface.contact, non-arcingmating electrical contact surfaces thatdo not experience wearout due to arc erosion that is oppositeof arcing contacts.contact, pitteda cont
19、act that has numerous discrete hollowsin its surface.contact pressurethe force per unit area of physical contactbetween two contacts. This term is frequently but improperlyused when contact force is meant. The area of physicalcontact is usually difficult to determine and quite differentfrom the appa
20、rent area of contact.contact resistancethe resistance to current flow offered bythe contact interface, comprising the sum of the constrictionresistance plus the film resistance.NOTE 1In a practical measurement, correction must be made for bulkresistance consisting of contact material, lead wires, et
21、c.contact, screwa contact fabricated with an external threadfor attachment to a support member or for adjustment.contact, slidingan electric contact which is expected to doits primary function during sliding.contact, solida monolithic contact member.contact, springa contact system in which one piece
22、 ofmaterial is used for both the driving spring and electriccontact.contact, statican electric junction designed for infrequentseparation and connection.contacts, wipingcontacts that have some sliding motionduring opening or closing.contact wiperelative tangential motion between contactingsurfaces t
23、hat occurs during the normal course of contactclosure.corona (discharge)a self-sustaining discharge characterizedby highly asymmetrical electric fields with the result thationization predominantly occurs near the electrode with thehigher potential gradient.crimp, vto establish an electrical and mech
24、anical attachmentbetween the two members by mechanically deforming onecontact member around another. In most cases, one memberis a stranded or solid wire, or a group of wires, the other isa hollow cylinder or partial cylinder that is deformed aroundthe wire(s).dark (or Townsend) dischargea discharge
25、 which may ormay not be self-sustaining. It is characterized by a uniformfield, current in the microampere range, and a nonluminousinter-electrode space.electromigration(1) Current-induced atomic diffusion in asolid metal due to electron momentum and the potentialgradient, (2) electrochemical proces
26、s of growth of metallicpath across an insulating surface under imposed electricfield.DISCUSSIONThe solid state process may cause significant materialtransport in regions of high current density such as a-spots in contacts.In devices with electrical contacts, the electrochemical process mayform short
27、s between conductors under certain environmental condi-tions.film resistancethat portion of the contact resistance that isdue to the presence of contaminants on one or both of thecontact members.fine transfersee material transfer, bridge.fretting, nsmall amplitude oscillatory motion, usually tan-gen
28、tial, between two solid surfaces in contact.DISCUSSIONHere the term fretting refers only to the nature of themotion without reference to the wear, corrosion, or other damage thatmay ensue. The term fretting is often used to denote fretting corrosionand other forms of fretting wear. Usage in this sen
29、se is discouragedbecause of the ambiguity that may arise.fretting corrosiona form of fretting wear in which corrosionplays a significant role.DISCUSSIONIn electrical contact interfaces involving non-noblemetals, fretting corrosion can cause rapid and substantial increases incontact resistance as a r
30、esult of localized appearance of insulatingoxides and oter corrosion products at the interface.fretting wearwear arising as a result of fretting. Seefretting.friction polymerizationthe process by which organic com-pounds (such as adsorbed air pollutants) on mating surfacesthat move relative to each
31、other polymerize to yield com-pounds of high molecular weight.NOTE 2When this occurs on electrical contacts and the materialsformed remain on the surface, contact resistance may increase substan-tially. The solid materials that are produced by the polymerization processare called “friction polymers”
32、 or “frictional polymers.”fritting (A-fritting)an electric breakdown between matingmetallic contacts, separated by an insulating film, whichoccurs when the field strength exceeds approximately1 000 000 V/cm. Metallic bridges are produced through thefilm if the fritting voltage is above the contact m
33、eltingvoltage.fritting voltagethe voltage at which fritting occurs.glow dischargea self-sustaining discharge characterized byessentially symmetrical electrodes, low current density, anda high cathode fall of about 200 V.high resistancecontact resistance exceeding an arbitrary,specified limit.inrush
34、currenta transient current that exists at the instant ofcontact closure and persists for a relatively short time.insertion forcethe force required to mate two connectorhalves.material transfera general term to describe the carry-overof material from one electrical contact to another.NOTE 3When the d
35、iscussion becomes specific, the term “gain” or “loss” is used with respect to a particular contact (for d-c application, anodeor cathode; for a-c application, stationary contact or movable contact). Forexample, anode gain, anode loss, stationary contact gain.material transfer, negativesee material t
36、ransfer.material transfer, positivesee material transfer.B542072material transfer, bridgematerial transfer that occurs with-out the presence of a gaseous electric discharge. The filamentof molten contact material that connects the two separatingcontacts does not rupture in the middle; thus there is
37、a gainof material on one contact and a loss of material from theother.material transfer, cathodemovement of contact metal fromthe cathode by means of a cathode arc.material transfer, needlematerial transfer that results in abuildup with a smaller diameter and a relatively great length.noiseSee conta
38、ct noise.normal forcethat component of the force between contact-ing bodies perpendicular to their interface.opening forcethe force available to open the contacts.plasmaa partially or totally ionized gas or vapor.porosityin metallic coatings, the presence of any disontinu-ity, crack, or hole in the
39、coating that exposes a differentunderlying metal.positive columnthat region of an electric discharge betweenthe cathode and anode falls.screw contactsee contact, screw.self-sustaining dischargea discharge in which all carriersnecessary for the transport of current in the discharge areproduced by thi
40、s discharge itself.showeringa particular form of corona discharge character-ized by strongly ionized streamers or streams of luminousplasma. It generally occurs at a field value just below thatwhich is required for a complete breakdown.sliderthat member of a sliding contact pair, normally thesmaller
41、, which may be moved through a range of locationson the opposing member.sliding electrical contactscontacting members that performtheir function while undergoing relative tangential motion.slip ringa continuous metal ring by means of which electri-cal current can be conducted to or from brush contac
42、ts. Oneelectrical contact member is designed to rotate with respectto the other.slip ring assemblytwo or more slip rings with connectingleads or terminals that have been mounted to a commonstructure.slip ring capsulean assembly that includes a slip ringassembly, brushes, and bearings for conducting
43、current onmultiple circuits from a stationary body to one that mayrotate.spark, dischargea non-self-sustaining discharge character-ized by high luminosity and a ratio of lateral dimension tolength that is substantially smaller than unity.sulfide creepin electrical contacts, spontaneous migration ofa
44、 sulfide based corrosion product that occurs at elevatedhumidity across a gold rich surface.DISCUSSIONThis process often involves copper sulfide produced bycorrosion on a copper alloy spring that, under severe conditions, cancompletely cover a gold contact mounted on the spring.tarnishthe chemical c
45、ompound on the surface of a contactresulting from the reaction of the contact material and theinorganic constituents of the surrounding atmosphere.tweakto make a mechanical adjustment of a spring arm of anelectrical contact assembly to adjust the force or position ofthe contact.wipersee slider. The
46、term “wiper” is sometimes used inter-changeably with the more preferred term “slider.”withdrawal forcethe force required to separate two matedconnector halves.B5420734. Terminology Defined In Individual Standards ForElectric Contact Test Methods And Electric ContactMaterialsThe following terms are d
47、efined in the terminology sectionsof indicated standards.Aluminum B 812Bulk Resistance B 539, B 812Conductor B 868Connectability B 896Connection Resistance B 539Contact Noise B 615Contact Performance B 868Contact Resistance B 667Contact Resistance Probe B 667Corrosion Products B 735, B 799, B 920Cri
48、mp B 913Crimp Barrel B 913Crimped Connection B 913Crimp Tab B 913Crimp Terminal B 913Decorations B 741, B 798Dry Circuit B 539Edge Noise B 615Edgecard Connector B 885Event B 878Fretting B 896Intermittence B 854Lot B 476Measurement Area B 735, B 741, B 798, B 799Metallic Coatings B 735, B 741, B 798,
49、 B 799, B 920Mixed Flowing Gas Test B 845Open-Circuit Voltage B 539Porosity B 735, B 741, B 798, B 799, B 920Pressure Connection System B 812Printed Wiring Board (Pwb)ContactsB 885Printed Wiring Board (Pwb)FingersB 885Rated Current B 539Reference Conductor B 812Residential Applications B 812Significant Surface B 735, B 741, B 798, B 799Standard Test Current B 539Static Contacts B 539Switching Noise B 615Underplate B 735, B 741, B 798, B 799, B 9205. Index Of Keywords Used In Individual Standards ForElect
