ASTM_B_741_-_95_2000.pdf

Designation:B 741 95(Reapproved 2000)Standard Test Method forPorosity In Gold Coatings On Metal Substrates By PaperElectrography1This standard is issued under the fixed designation B 741;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers equipment and techniques fordetermining porosity in gold coatings,particularly electrode-posits and clad metals used on electrical contacts.1.2 This test method is designed to show whether theporosity level is less or greater than some value which byexperience is considered by the user to be acceptable for theintended application.1.3 This test method is suitable for flat surfaces,or withappropriate fixtures,for gently curved surfaces.1.4 Avariety of other porosity testing methods are describedin Guide B 765 and in the literature.Detailed critical reviewsof porosity testing are also available.2,3,4Other porosity testmethods are B735,B798,B799,and B809.1.5 This test method is specifically designed for use withgold coatings(95%gold)on substrates of copper and nickeland their alloys.Although not covered in this standard,variations of this test method may be found useful in evaluatingcoatings other than gold.1.6 The values stated in SI units are to be regarded asstandard.The values in parenthesis are for information only.1.7 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to its use.For a specificprecautionary statement,see Note 1.2.Referenced Documents2.1 ASTM Standards:B 276 Test Method for Apparent Porosity in CementedCarbides5B 374 Terminology Relating to Electroplating6B 537 Practice for Rating of Electroplated Panels Subjectedto Atmospheric Exposure5B 542 Terminology Relating to Electrical Contacts andTheir Use5B 735 Test Method for Porosity in Gold Coatings on MetalSubstrates by Nitric Acid Vapor6B 765 Guide for Selection of Porosity Tests for Electrode-posits on Related Metallic Coatings5B 798 Test Method for Porosity in Gold or PalladiumCoatings on Metal Substrates by Gel-Bulk Electrography6B 799 Test Method for Porosity in Gold and PalladiumCoatings by Sulfurous Acid/Sulfur-Dioxide Vapor6B 809 Test Method for Porosity in Metallic Coatings byHumid Sulfur Vapor(“Flowers-of-Sulfur”)53.Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminology B 542 and terms relating to metalliccoatings are defined in Terminology B 374.3.2 Definitions of Terms Specific to This Standard:3.2.1 decorationsthose reaction products emanating fromthe pores that provide visual contrast with the paper.3.2.2 measurement area(or 88significant surface)thesurface that is examined for the presence of porosity.Thesignificant surfaces or measurement areas of the part to betested shall be indicated on the drawing of the part or byprovision of suitably marked samples.3.2.3 DiscussionFor specification purposes,the signifi-cant surfaces or measurement areas are often defined as thoseportions of the surface that are essential to the serviceability orfunction of the part,such as its contact properties,or which canbe the source of corrosion products or tarnish films thatinterfere with the function of the part.1This test method is under the jurisdiction of ASTM Committee B02 onNonferrous Metals and Alloys and is the direct responsibility of SubcommitteeB02.11 on Electrical Contact Test Methods.Current edition approved April 15,1995.Published June 1995.Originallypublished as B 741 85.Last previous edition B 741 90.2For example:Nobel,F.J.,Ostrow,B.D.,and Thompson,D.W.,“PorosityTesting of Gold Deposits,”Plating,Vol 52,1965,p.1001.3Clarke,M.,in“Properties of ElectrodepositsTheir Measurement and Signifi-cance,”Edited by Sard,R.,Leidheiser,H.,and Ogburn,F.The ElectrochemicalSociety,Princeton,NJ,1975.4Krumbein,S.J.,“Porosity Testing of Contact Platings,”Proceedings,Connec-tor and Interconnection Technology Symposium,Oct.1987,Phila.,PA,p.47.5Annual Book of ASTM Standards,Vol 02.05.6Annual Book of ASTM Standards,Vol 02.04.1Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959,United States.3.2.4 metallic coatingsinclude platings,claddings,orother metallic layers applied to the substrate.The coating cancomprise a single metallic layer or a combination of metalliclayers.3.2.5 porositythe presence of any discontinuity,crack,orhole in the coating that exposes a different underlying metal.3.2.6 underplatea metallic coating layer between thesubstrate and the topmost layer or layers.The thickness of anunderplate is usually greater than 0.8 m(30 in.).4.Summary of Test