ASTM_F_204_-_76_2013.pdf

Designation:F20476(Reapproved 2013)Standard Test Method forSurface Flaws in Tungsten Seal Rod and Wire1This standard is issued under the fixed designation F204;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 test method covers the determination of the pres-ence of surface flaws in tungsten-seal rod and wire of randomor cut lengths,and in the tungsten section of multiple-piece-through leads used in electronic devices,by means of exami-nation of a glass bead sealed to the tungsten.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 use.2.Terminology2.1 Definitions:2.1.1 beaded lengththe actual length through which aglass-to-tungsten seal exists as evidenced by the color of theinterface.2.1.2 faulta tungsten-glass seal in which a fissure,eitherdelineated by a line of bubbles or in itself clearly discernible,is observed when inspected as prescribed in this test method.2.1.3 fissureany narrow opening or cleft in the surface ofthe tungsten.2.1.4 line of bubblesone long or several small bubbles soarranged in the otherwise substantially bubble-free glass beadthat they are in an almost straight line immediately adjacent tothe tungsten-glass interface.3.Apparatus3.1 Beading EquipmentSuitable beading equipment ca-pable of producing glass-to-tungsten seals as prescribed inSection 4.3.2 MicroscopeA low-power microscope capable of mag-nification up to 30 diameters,preferably of the binocular type.3.3 Light Source A suitable white light source,preferablydiffuse for illumination of the bead under the microscope.4.Preparation of Test Specimen4.1 The test specimen shall be a beaded tungsten rodprepared in the following manner:4.1.1 Clean the surface to be beaded in the usual manneremployed by the user of the tungsten.4.1.2 Alternative Methods of Specimen PreparationIncase of disagreement between the manufacturer and thepurchaser,substitute one of the following alternative methodsof preparing the tungsten rod for that in 4.1.1.4.1.2.1 Boil the tungsten for 2 min in a 5%solution of 27%hydrogen peroxide.Pour off the hydrogen peroxide and rinsethe tungsten twice in distilled water.Dry rapidly with purealcohol or in an oven heated to 100C.4.1.2.2 Place the tungsten in a solution(20 weight%)ofsodium hydroxide or potassium hydroxide and pass sufficientelectrical current through it to induce electrolytic actionsufficient to clean the specimen.4.2 Bead the cleaned tungsten rod over the area to beexamined with glass,of the type and wall thickness commonlyused for beading,to a length of not less than 5 mm bead length.4.3 To permit examination of the glass-tungsten interface,the bead shall be substantially free from bubbles,from causesother than the tungsten defects,and shall have been so preparedthat the surface of the tungsten is clearly visible through thebead.4.4 The color of the glass-to-tungsten seal shall be such asto indicate the proper application of heat to the bead to obtaina satisfactory seal.NOTE1The usual preferred seal color shall be a golden-yellow hue.5.Procedure5.1 Hold the beaded tungsten in focus under the microscopein such a manner that the beaded length may be observed.5.2 Rotate the specimen through 360 on its axis so that theentire surface of the tungsten-glass interface may be examined.5.3 Observe whether fissures or lines of bubbles are presentin the seal.If either are present,record the seal as a fault.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.03 on MetallicMaterials.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1946.Last previous edition approved in 2009 as F204 76(2009).DOI:10.1520/F0204-76R13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.Report6.1 Report the following information:6.1.1 Purchase order number,6.1.2 Diameter of specimens,6.1.3 Number of specimens examined,6.1.4 Magnification used,6.1.5 Cleaning procedure used,6.1.6 Type and nominal wall thickness of glass bead used.6.1.7 Nominal beaded length,6.1.8 Color of seal,and6.1.9 Number of faults observed.7.Keywords7.1 glass bead;glass-to-metal seals;tungsten-glass sealsASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.Users of this standard are expressly advised that determinat