ASTM_F_44_-_95_2011.pdf

Designation:F4495(Reapproved 2011)Standard Specification forMetallized Surfaces on Ceramic1This standard is issued under the fixed designation F44;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This specification covers requirements for powderedrefractory metal coatings produced with or without additives.These coatings are applied to ceramic bodies in order to joinceramic bodies to metals or to other metallized ceramics bymeans of brazing or soldering.Included in this specification arerequirements for a secondary metallic layer which is usuallyapplied over the refractory metal layer.1.2 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.3 The values stated in inch-pound units are to be regardedas the standard.The values given in parentheses are forinformation only.2.Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensF19 Test Method for Tension and Vacuum Testing Metal-lized Ceramic Seals3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 ceramicsas referred to in this specification areunderstood to be inorganic,nonmetallic materials,the majorphase of which must be crystalline.A glassy intercrystallinematrix may be present as one of the minor phases.3.1.2 metallizing on a ceramic,is a process whereby asintered matrix of metal particles firmly adheres to the ceramic.3.1.3 refractory metalsthose metals with melting pointsequal to or higher than that of chromium.Therefore,this groupincludes chromium,columbium,molybdenum,rhenium,tanta-lum,and tungsten.4.Ordering Information4.1 The manufacturer and purchaser shall agree upon spe-cific quality levels as outlined in the following sections:4.1.1 Uniformity of metallizing(Section 5),4.1.2 Thickness of metallizing(Section 6),4.1.3 Secondary metal layer on the metallizing(Section 9),4.1.4 Values for bond strength(Section 10),and4.1.5 Vacuum tightness of brazed metallized ceramic as-semblies(dependent on allowable use of manufacturers prod-uct)(Section 11).5.Uniformity of Metallizing5.1 Either of the following two levels of quality may beagreed upon between manufacturer and purchaser,dependingupon end use,seal area,and geometry.5.2 Level ALess Demanding Application:5.2.1 Thin areas where the ceramic substrate can usually beseen without magnification through the metallizing will beacceptable only if all of the following conditions are met:5.2.1.1 There are no more than two such areas on any onecoated band,spot,or pattern detail.5.2.1.2 Their extremities are no closer than 10%of the totalband length to each other.5.2.1.3 They are no wider than 10%of the width of theband but not exceeding 1 mm.5.2.1.4 Their cumulative length does not exceed 25%of thetotal band length.5.2.2 Defects such as brush marks,screen marks,marks inthe metallizing left by foreign matter such as lint,dust,etc.,andpits or blisters,will be acceptable if they meet the fourconditions outlined in 5.2.1.1 through 5.2.1.4.Such defectswill also be acceptable if their raised edges do not interferewith proper assembly of the joint.5.2.3 Projections on metallized surfaces,such as oversizedparticles or agglomerates will be objectionable if they interferewith assembly.5.2.4 Continuous coatings over sharp edges or corners witha radius less than132in.(0.8 mm)will not be required unlessby specific agreement between manufacturer and purchaser.5.3 Level BDemanding Application:5.3.1 Thin areas will be unacceptable where the ceramicsubstrate can be seen through the metallizing when examinedat 40 magnification.1This specification is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.03 on MetallicMaterials.Current edition approved June 1,2011.Published June 2011.Originallyapproved in 1968.Last previous edition approved in 2006 as F44-95(2006).DOI:10.1520/F0044-95R11.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.3.2 Defects through which the underlying ceramic can beobserved,such as brush or screen marks,marks left by foreignmatter such as lint or dust,and pits or chips,will be acceptableonly if all of the following conditions are met:5.3.2.1 There are no more than two such defects on anycoated band,spot,or pattern detail.5.3.2.2 Their extremities are not closer together than 10%of the length of the met