IPC-TM-650 TEST METHODS MANUAL N/A - gmsystems.com

1 PurposeThis test method covers procedures for deter-mining the electrical resistivity of copper foil. It provides for anaccuracy of percent of test specimens having a resis-tance of ohm (10 microhms) or DefinitionResistivity is the electrical resistance of abody of unit length and unit cross-sectional area or unitweight. Volume resistivity is commonly expressed in ohms fora theoretical conductor of unit length and cross-sectionalarea; in English units in ohm circular mil/ft and in metric unitsin ohm mm2/meter. It may be calculated by the following for- :p. = volume resistivity in ohm circular mil/ft or ohm mm2/meter,A = cross-sectional area in circular mils, or sq mm,L = gauge length, used to determine R, in ft, or m, andR = measured resistance in resistivity is commonly expressed in ohms for a theo-retical conductor of unit length and weight.

2 The method forcalculating weight resistivity, based on resistance, length, andweight measurements, of a test specimen is given in Note Applicable Test SpecimenThe test specimen must have the fol-lowing resistance of at least ohm (10 microhms) inthe test length between potential contacts, test length of at least 1 ft or 30 cm, thickness, width or other dimension suitable to the limi-tations of the resistance measuring instrument, surface cracks or defects visible to the unaided nor-mal eye, and substantially free from surface oxide, dirtand grease, joints or Kelvin-type double bridge or a potentiometer, if theresistance of the specimen is below 1 ohm, 1 ohm or more, a Wheatstone bridge may be applicable, a Hoopes conductivity bridge maybe ConditionsWhen the measurement is made at anyother than a reference temperature, the resistance may becorrected for moderate temperature differences to what itwould be at the reference temperatures as follows:RT=Rt1+ T(t T)where.

3 RT= resistance at reference temperature T,Rt= resistance as measured at temperature t, T = known or given temperature coefficient of resistanceof the specimen being measured at reference tempera-ture T,T = reference temperature, andt = temperature at which measurement is :The parameter T, in the above equation, varies withconductivity and temperature. For copper of 100 percent con-ductivity and a reference temperature of 20 C, its value Table 2 lists temperature coefficients for determinations of the dimensions and weight of thetest specimen must be accurate within Sanders RoadNorthbrook, IL 60062-6135 IPC-TM-650 TEST METHODS of Copper FoilDate8/76 RevisionAOriginating Task GroupN/AMaterial in this Test METHODS MANUAL was voluntarily established by Technical Committees of the IPC.

4 This material is advisory onlyand its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of thismaterial. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent referenced is for the convenience of the user and does not imply endorsement by the CONNECTINGELECTRONICS cross-sectional dimensions of the specimen maybe determined by micrometer measurements, and a sufficientnumber of measurements shall be made to obtain the meancross section to within case any dimension of the specimen is less in. and cannot be measured to the required accuracy,the cross section shall be determined from the weight, den-sity, and length of the the density is unknown, it shall be determinedby weighing a specimen first in air and then in a liquid ofknown density at the test temperature, which shall be at roomtemperature to avoid errors due to convection the density from the following formula: =WaXdWa WIwhere.

5 = density of the specimen, grams per cu cm,Wa= weight of the specimen in air, grams,WI= weight of the specimen in the liquid, grams, andd= density of the liquid at the test temperature, grams percu potential leads are used, the distance betweeneach potential contact and the corresponding current contactshall be at least equal to 1-1/2 times the cross-sectionalperimeter of the yoke resistance (between reference standard andtest specimen) shall be appreciably smaller than that of eitherthe reference standard or the test specimen unless a suitablelead compensation method is used, or it is known that the coiland lead ratios are sufficiently balanced so that variation inyoke resistance will not decrease the bridge accuracy belowstated resistance measurements to an accuracy of all resistance measurements, the measuring currentraises the temperature of the specimen above that of the sur-rounding medium.

6 Therefore, care shall be taken to keep themagnitude of the current low, and the time of its use shortenough so that the change in resistance cannot be detectedwith the eliminate errors due to contact potential, two read-ings, one direct and one with current reversed, must be takenin direct tests are recommended whereby the specimenis turned end for end, and the test cleaning of the specimen at current andpotential contact points may be necessary to obtain goodelectrical Reference TestsFor reference tests, the reportshould include the of test specimen, of material, temperature, length of specimen, of obtaining cross-sectional area: the average val-ues of micrometer readings, or, if by weighing a record oflength, weight, and density determinations that may bemade, and calculated cross-sectional , if used, of measuring resistance, of resistance, temperature, value of resistivity at the reference temperature, mechanical and thermal treatments.

7 (Since theresistivity of a material usually depends upon them, theseshall be stated whenever the information is available. ) Routing TestsFor routine tests, only such of theitems in paragraph as apply to the particular case, or aresignificant, shall be of Copper FoilDate8 Volume ResistivityVolume resistivity is used in placeof weight resistivity and percent conductivity. The valueof ohm circular mil/ft at 20 C (68 F) is the volumeresistivity equivalent to the International Annealed CopperStandard (IACS) for 100 percent conductivity. This termmeans that a wire 1 ft in length and 1 cir mil in cross-sectionalarea would have a resistance of a wire1minlength, and 1sq mm in cross-sectional Weight ResistivityWeight resistivity is expressed inEnglish units in ohm-pound/mile2and in metric units in ohm gram/meter2.

8 It may be calculated as follows: w=WL1L2 Rwhere: w = weight resistivity in ohm-pound/mile2, or ohm-gram/meter2,W = weight of the test specimen in lb, or gm,L2= length of the test specimen in miles, or m, andL1= gauge length, used to determine R, in. miles or m, andR = measured resistance in 1 Equivalent Resistivity Values For CopperConductivity at 20 C (68 F), percent RESISTIVITYOhm-Circular mil/f .. RESISTIVITY0hm ConversionResistivity and Conductivity Conversion Conversion of the various units of volume resistivity, weightresistivity, and conductivity, may be facilitated by employingformulas and factors. Table 2 lists values of density, for thecommon electrical conductor DensityFor the purpose of resistivity and conductivityconversion, the density of copper materials may be taken asshown in Table 2, based on a temperature of 20 C (68 F).

9 Table 2 Density and Temperature Coefficient ofResistance for Electrical MaterialsDensityat 20 C, gmper cu cmTemperatureCoefficient ofResistanceat 20 CCopper, % of Copper FoilDate8/76 RevisionAPage3of3