NEMA WC 65-1995 Reasoned Approach to Solving Solderability Problems with Tin-Coated and Nickel Coated Stranded Conductors in High Performance Wire and Cable Applications《高性能电线和电缆应用.pdf

1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA WC 65-1995 (R2003)A Reasoned Approach to Solving Solderability Problems with Tin-Coated Nickel-Coated Stranded Conductors in High Performance Wire and Cable ApplicationsNEMA Standards Publication No. WC 65-1995 (R2003) A Rea

2、soned Approach to Solving Solderability Problems with Tin-Coated Nickel-Coated Stranded Conductors in High Performance Wire and Cable Applications Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, VA 22209 www.nema.org Copyright 2003 by the Natio

3、nal Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. NOTICE AND DISCLAI

4、MER The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the dev

5、elopment of this document. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out

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13、 in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. NENA WCrb5 95 6470247 0508483 854 B WC 65-1 995 Page i Table of Contents Page Foreword ii Section 1 GENERAL 1.1 scope 1-1 1.2 Referenced Standards 1-1 1.3 Other Referenced

14、 Publications . 1-2 Section 2 A REASONED APPROACH TO SOLVING SOLDERABILITY PROBLEMS HIGH PERFORMANCE WIRE AND CABLE APPLICATIONS 2.1 Introduction . 2-1 2.2 Discussion 2-1 2.2.1 Basics of Solderability 2-1 2.2.2 Conductor Coatings . 2-2 2.2.3 2.2.4 Solderability Test Methods and Performance Standards

15、 2-3 2.2.5 Solder Fluxes . 2-4 2.3 Conclusions 2-5 2.4 Recommendations 2-5 WITH TIN-COATED AND NICKEL-COATED STRANDED CONDUCTORS IN The Effect of Processing History and Storage on Solderability . 2-3 NENA WCXh5 95 6470247 0508484 790 WC 65-1 995 Page ii Foreword This standards publication has been a

16、pproved as authorized engineering information. This standard publication was prepared by the NEMA High Performance Wire Bum, J.H.; Busch, G.A.; Larson, D.J. Effect of Thema1 Aging on the Flexibility and Conductivity of Plated and Unplated Copper Conductors, 28th IWC Symposium November 1979, Inagaki,

17、 T. NEMA WC*85 75 6470247 0508487 4TT WC 65-1 995 Page 2-1 Section 2 A REASONED APPROACH TO SOLVING SOLDERABILITY PROBLEMS HIGH PERFORMANCE WIRE AND CABLE APPLICATIONS WITH TIN-COATED AND NICKEL-COATED STRANDED CONDUCTORS IN 2.1 INTRODUCTION Although crimp connections are the predominant method empl

18、oyed for terminating stranded conductors in high performance applications, soldered connections are still required and used in certain areas. Traditionally silvercoated copper conductors have been used in these high performance applications and because of its excellent characteristics, solderability

19、 has not been a problem. However in recent yearc, with the increasing use of tincoated and nickelcoated copper conductors, significant solderability problems have been reported. Focusing primarily on wire quality and conformance as the cause, substantial efforts have been made to review, modify and

20、apply existing solderability requirements to address the problem. Consequently, stringent standards have been applied which were developed for use with terminal lugs and boards and not applicable to small diameter stranded wire constructions. Instead of solving the problem, this has further aggravat

21、ed the situation by addressing the symptoms rather than the root causes. This report is intended to clany the fundamental root causes of solderability problems through a review of the metallurgy of conductors, test methods and requirements leading to recommendations and solutions. 2.2 DISCUSSION The

22、 reported problems with tincoated and nickelcoated copper stranded conductors range from large visible pinholes in the solder coverage to a total dewetting at the solder joints resulting in mechanically weak and unreliable joints and high termination resistance. These problems have been observed bot

23、h during soldering and pretinning operations. In some cases, visual examination prior to these operations did not reveal a potential for poor solderability. Further, these problems have been found to occur both beniveen and within lots of wire and generally become worse with extended age. Similar so

24、lderability problems have also been reported during termination of tincoated and nickelcoated copper braid shields. To address this problem, reviews of existing solderabili requirements and their application to stranded wire have been initiated. This effort was based on the assumption that the probl

25、ems were due to manufacturing defects in the tin-coated and nickelcoated copper conductors and, therefore, the incorporation of solderability test requirements to insure product conformance became the primary focus of efforts towards a solution. Some solderability problems can and do occur as a resu

26、it of improperly manufactured conductors. However, the fundamental root cause of most problems is a result of the basic metallurgical limitations of the conductor systems and the application of inappropriate solderability requirements for the specific conductor coatings employed. 29.1 Basics of Sold

27、erability The objective of soldering is to obtain a joint termination which does not electrically or mechanically degrade the interconnect system. For this purpose the solder must wet the conductor and terminal surfaces creating a good metallurgical bond and avoid discontinuities which would increas

28、e electrical resistance and lower the mechanical strength. In a soldering operation the conductor and terminal is heated to a temperature above the melt point of the solder material. The solder is then placed in contact with the surfaces and allowed to melt. A good metallurgical bond is formed when

29、the solder material (tin, tin-lead, silver, silver-tin, etc.) is able to form a thin alloy or compound layer with these surfaces. In their pure state most metal and alloy surfaces can be readily joined in this fashion. However, metals in general have an affinity for oxygen and readily form oxide lay

30、ers. NEMA WC*b5 75 = 6470247 0508488 336 WC 65-1 995 Page 2-2 These oxide layers inhiba the formation of a metallurgical bond and require fluxes which contain reducing agents to break down the oxide surfaces and allow soldering. The degree and tenacity of the oxides vary with the metal or alloy. In

31、the noble metals, such as silver, gold, and platinum, the oxides are extremely thin and are readily soldered without the use of fluxes. For this reason gold and silver coatings are used extensively for terminations in the electronics industry. Note however that gold has some drawbacks in that it may

32、 cause embrittlement of the solder connection. Intermetallic compounds, which are discussed later in this document, tend to form the most stable oxides and therefore require the most active fluxes with stronger reducing agents to obtain good solderability. 2.2.2 CONDUCTOR COATINGS In high performanc

33、e applications, silver-coated copper stranded conductors manufactured in accordance with ASTM B 298 have traditionally been used. With its high conductivity and resistance to oxidation, the silver-coating not only provides low termination resistance but excellent solderability over extended time. Ho

34、wever in recent years stringent solderability requirements have been applied to tincoated and nickel- coated stranded conductors. Due to the fundamental metallurgical differences in these conductors, similar solderability characteristics cannot be obtained utilizing the same soldering requirements w

35、hich were appropriate for silver. These differences significantly affect solderability and must be considered in establishing appropriate solderability standards for the different conductor systems. 2.2.2.1 lin-Coated Copper Stranded Conductors manufactured in accordance with ASIM B33. Unlike silver

36、-coated copper, tin-coated copper oxidizes readily with the reaction proceeding quickly under noml storage conditions (50 - 100F) and less than 90% RH. Visual examination of the surface can reveal the degree of oxidation present. Prior to significant oxidation (bright metallic to light gray), the ti

37、n coating can generally be soldered using a rosin (type R) flux. However, within 6 months to one year depending upon storage conditions, a mildly activated rosin (type RMA) flux is required to obtain acceptable solder joints. In the later stages of oxidation (gray to dark gray) a fully activated ros

38、in (type RA) flux becomes necessary to remove the oxidation. Note however, that type RA flux is not recommended for use on stranded wires, rather, one of the more active (but easier to clean) water soluble fluxes (WSF) should be considered. A complete description of the aforementioned fluxes can be

39、found in MIL-F-14256. The degree of oxidation becomes a significant consideration because the wire being soldered and installed is frequently over one year old due to the many levels of manufacturing , distribution , and storage. Tincoated copper stranded conductors currently being employed in high

40、performance applications are In addition to oxide formation, tin-coated copper is also susceptible to intermetallic diffusion reactions which significantly affect solderability. These reactions documented and published in the proceedings of the 1970 IWCS (International Wire iICimiiuive vote of at Ic

41、ast two-thirds of thc Subdivision volts cast in tbc affrmiativc of negative. (Srandtvdkatwn PoliciCr and Proccdwu. pp. 5) Identification of Status - . HIGH PERFORMANCE WIRE & CABLE SECTION OF THE NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION NEMBER COMPANIES AmaicanElsctricCabiecampenY AstroIndustri

42、es.nic. Dayton, OH AT&T BeSkeIeyHei*NJ Belden Wire & Cable Company Rium =-Tek, Inc. New Hoiiand, PA BICC Brand-Rw W-CT BICC Industrial We York, PA CommScopeNaworkCflblC- Ciaremont, NC c NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION 1300 NORTH 17TH STREET, SUITE 900 ROSSLYN. VA 22209www.NEMA.orgTO ORDER ADDITIONAL NEMA STANDARDS VISITWWW.GLOBAL.IHS.COM OR CALL 1-800-854-7179/1-303-397-79565612_0514TB