# ASTM F205-94 (Reapproved 2015)

Designation F205 94 Reapproved 2015Standard Test easuring Diameter of Fine Wire by Weighing1This standard is issued under the fixed designation F205; 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 covers the measurement of the averagediameter of fine wire by weighing a known length; it appliesparticularly to sizes up to 0.13 mm used in electron devices andlamps.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. Referenced Documents2.1 ASTM Standards2F180 Test for Density of FineWire and RibbonWirefor Electronic Devices3. Apparatus3.1 The apparatus shall consist of a suitable torsion or otherdirect-reading balance capable of reading to 0.002 mg or 0.1 of the weight to be weighed whichever is larger, with anaccuracy of 0.004 mg or 0.2 whichever is larger. The rangeof the balance or the size of the specimen shall be such thatthe reading will lie within the upper half of the scale.4. Test Specimens4.1 Test specimens shall be selected at least 1 m from theend of a spool or sufficiently far from the end to be free fromkinks or other damage resulting in lack of straightness of thecut length.4.2 The wire shall be drawn from the spool under a loweven tension so that no elongation of the wire takes place.4.3 Each test specimen shall be cut to a length of 200 6 0.1mm. To prevent stretching, care shall be taken so that thetension is just sufficient to eliminate the sag and curl. Anydisagreement concerning the amount of tension to be used incutting shall be resolved between the manufacturer and thepurchaser.4.4 The test specimen shall be folded upon itself severaltimes and twisted to make a compact bundle with loopconsisting of a single strand for hanging it on the balancebeam. In the case of multiple specimens, all specimens shall betwisted together and hung by a loop consisting of a singlestrand. The specimen shall be handled as little as possible. Theoperators hands shall be clean and dry.5. Number of Specimens5.1 Weigh a single specimen if its weight lies within theupper half of the scale of the instrument. When the weight isless than half of the scale of the instrument, weigh a sufficientnumber of specimens, 200 mm in length, simultaneously sothat the total weight will register in the upper half of the scale,preferably as close to the limit of the balance as possible. Usethe lowest range instrument compatible with the weight of the200-mm weight specimen to reduce the number of 200-mmlengths that must be weighed together.6. Repetition of Weighing6.1 If the corrected weight of a single specimen lies within60.5 of either the minimum or the maximum limit specifiedfor the wire weight, cut and weigh two more specimens of wirein a similar manner. When two or more lengths of wire havebeen weighed simultaneously to produce a reading in the upperhalf of the scale because of the small size of the wire, cut andweigh two more sets of specimens in a similar manner.7. Calibration and Checking of the Balance7.1 Check the balance regularly in accordance with therecommendations of the manufacturer.7.2 If a variety of weights are to be determined, calibrate thebalance at five major points on the scale and at zero bydetermining the weights of calibrated check weights. If anypoint is in error by more than 1 , remove the balance from1This test is under the jurisdiction of ASTM Committee F01 onElectronicsand is the direct responsibility of Subcommittee F01.03 on MetallicMaterials, Wire Bonding, and Flip Chip.Current edition approved July 1, 2015. Published September 2015. Originallyapproved in 1945 as B205 45 T. Last previous edition approved in 2010 as F205 942010. DOI 10.1520/F0205-94R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume ination, 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 States1service and repair it.Apply corrections determined by checkingto the apparent readings to obtain corrected weights. Obtaincorrections applied to apparent weights by interpolation be-tween the closest calibrated points, one above and one belowthe reading.7.3 If the amount of work to be weighed at one point on thescale justifies it, the balance may be calibrated with a standardweight or combination of weights deviating by not more than10 from that of the weight to be determined. In this case,adjust the balance so that the balance reads the known weightof the check weight correctly when it is in balance, therebyreducing the correction to zero.7.4 Calibrate the balance, at zero under no load, or atpositive values when loaded to check weights, by using theaverage of three consecutive readings, taken under conditionsspecified in 7.2 or 7.3, whichever is applicable.8. Calibration with Standard Weights8.1 Check weights are subject to change of mass due towear from handling and use, and from chemical action result-ing from exposure. Depending on use, but not less than twicea year, compare the calibrated check weights with the primaryweights, calibrated by the National Institute of Standards andTechnology, and apply the necessary corrections.8.2 The primary standard check weights shall be NISTClass M, or equivalent, for weight determinations of 2.00 mgor less, and Class S, or equivalent, for weight determinationsover 2.00 mg.9. Procedure9.1 Handle and use the balance as recommended by themanufacturer. Direct particular attention to requirements forcareful handling, protection from vibration and atmosphericdust, errors induced by temperature changes, and the necessityfor avoiding paralax in reading.10. Calculation10.1 Calculate the average diameter of the wire from thefollowing equation see Appendix X1D 5 3.1413/ 3 W,whereD average diameter of wire, mils mils 0.0254 mm, density of wire, g/cm3see Note 1,W weight of wire, mg/200 mm,Also, letK 5 3.1413/,thenD 5 K W see Note 2.NOTE 1The density of wire for alloys not found in Table 1 may bedetermined at or near the finished size and the finished condition inaccordance with Test F180.NOTE 2Values for density and the constant K for several alloys aregiven in Table 1.11. Interpretation of Results11.1 If a single specimen or a single set of specimens isweighed, and its corrected weight, or average weight whenmultiple specimens are used, is found to lie between the point0.5 above the minimum limit and 0.5 below the maximumlimit, the wire shall be considered to meet the specified limits.11.2 If the corrected wire weight is under 0.5 below theminimum limit or over 0.5 above the maximum limit, thewire is considered not to meet the specified limits.11.3 If the corrected weight of a single specimen, or theaverage weight when multiple specimens are used, lies withinthe range of 6 0.5 of the maximum or 60.5 of theminimum limit, exactly three specimens or three sets ofspecimens shall be weighed, and the average corrected valuecompared with the maximum and minimum limits. If theaverage of the three readings lies between the maximum limitand the minimum limit, the weight of the wire is considered tolie within these limits.NOTE 3The following is an example of the uation of results. If aspecified weight of 8.00 mg/200 mm and a specified tolerance of 6360.24, mg/200 mm is assumed, the range determined by these specifi-cations must be 7.76 to 8.24 mg/200 mm. The working zones for weighingwill beMinimum limit 0.5 , 7.76 0.04 7.80 mg/200 mm0.5 , 7.76 0.04 7.72 mg/200 mmMaximum limit0.5 , 8.24 0.04 8.20 mg/200 mm 0.5 , 8.24 0.04 8.28 mg/200 mmThe corrected weight of a single cut length of wire found to lie between7.80 and 8.20 mg/200 mm will suffice to accept the wire. The correctedweight on a single cut length of wire found to be less than 7.72 mg/200mm or more than 8.28 mg/200 mm will suffice to reject the wire as outsidethe specified limits.If the corrected weight of a single cut length is found to be betweeneither 7.72 and 7.80 mg/200 mm, or 8.20 and 8.28 mg/200 mm, two morepieces shall be cut, weighed, and averaged with the first weight. If theaverage of the three weights lies between 7.76 and 8.24 mg/200 mm,inclusive, the wire is considered to meet the specified range; if outsidethese limits, it is considered not to meet it.12. Dimensions, Mass, and Permissible Variations12.1 Permissible variations from the specified weight shallbe designated by maximum and minimum weights, or as aplus-and-minus percentage tolerance to be applied to thenormal weight.TABLE 1 Density and Constant K for Diameter CalculationsAlloyDensity,Agcm3ConstantKAluminum 1 magnesium 2.7 1.912Aluminum 1 silicon 2.7 1.912Gold 19.32 0.71585 nickel, 15 chromium 8.47 1.07958 nickel, 20 molybdenum, 20 iron, 2 manganese8.78 1.06095 nickel, 5 manganese 8.74 1.063Permanickel 8.77 1.061Monel 8.81 1.058Molybdenum 10.14 0.986Tantalum 16.59 0.771Tungsten 19.17 0.717AThe density values in this table have been determined by ASTM Test F180.F205 94 2015213. Report13.1 The report shall consist of the number of readings, andthe average corrected weight of the wire to three significantfigures in milligrams per 200 mm, except that for sizes under1.00 mg/200 mm only two significant figures shall be reported.The value reported shall be the weight of the outside end of thespool unless it shall have been agreed otherwise between themanufacturer and the purchaser.14. Precision and Bias14.1 PrecisionThe precision of this test has notbeen ally uated using an interlaboratory testing pro-gram. However, it is possible to uate the standard deviationof the wire diameter, D, for a given experimental setup,using the following equation which is based on propagation oferrorsD 5D/22 5 D/W22W1D/L22L.where each of the partial derivative terms are obtained fromappropriate differentiation of the definition of specimen wirediameter, D, shown in 10.1 and L is the wire length.14.2 BiasProper measurement technique for all the vari-ables shown in the equation which defines Din14.1 shouldeliminate bias from this test .15. Keywords15.1 electronic devices; fine wire; wire bondingAPPENDIXNonmandatory InationX1. DERIVATION OF DIAMETER CALCULATION EQUATIONX1.1 The diameter calculation equation in Section 10 wasderived as followsWire weight 5 x sectional area 3length 3density, orW 5 D2/4 3L 3,whereW wire weight,D wire diameter,L wire length, and wire density.Rearranging,D25 4W/ LorD 5 4W/ L 5 1.1284 W/L.LetW 5 W/L,thenD 5 1.1284 W /.Correcting for unitW weight in mg/200 mm or mg/20 cm, density in gm/cm3or 1000 mg/cm3, andD diameter in mils where 1 mil 0.00254 cm,thenD 5 1.1284W mg/20 cm 1000 mg/cm3/0.00254 cmmil,orD 5 1.1284 W /cm2/20000/0.00254 cm,orD 5 1.1284 cm/141.42 W //0.00254 cm,orD 5 3.1413 W /.Other useful equationsW 5 0.10134 D2, and 5 9.868 W/D2.ASTM 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 determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. 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