1、Designation: F 1896 98 (Reapproved 2004)Test Method forDetermining the Electrical Resistivity of a PrintedConductive Material1This standard is issued under the fixed designation F 1896; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, 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 the determination of the elec-trical resistivity of a conductive material as u
3、sed in themanufacture of a membrane switch.1.2 This test method is not suitable for measuring forcesensitive conductive materials.1.3 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.1.4 This standard does not purport to
4、 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 membrane switcha
5、 momentary switching device inwhich at least one contact is on, or made of, a flexiblesubstrate.2.1.2 circuit/test pattern resistanceelectrical resistance asmeasured between two terminations of a circuit trace.2.1.3 squareA geometric unit of a printed conductivecircuit trace/pattern obtained by divi
6、ding the length (L)oftheprinted conductive circuit trace/pattern by its width (W).2.1.4 resistivityohms per square per mil of a conductivematerial.3. Significance and Use3.1 Resistivity is useful to suppliers and manufacturers asfollows:3.1.1 when designing membrane switch interface circuitry,3.1.2
7、when selecting the appropriate conductive material,3.1.3 for conductive material quality verification, and3.1.4 for conductive material cure optimization and qualitycontrol.4. Apparatus4.1 Resistance Measuring Device, (that is, ohm meter)equipped with test leads and probes. The device should becapab
8、le of measuring resistances up to 100 MV with anaccuracy of greater than 1.5 % of full scale reading. Test probesshould have tips that are 25 to 250 % of the width (W)oftheprinted conductor test pattern.4.2 Test Surface, to be flat, smooth, unyielding and largerthan switch under test.4.3 Thickness M
9、easuring Device, capable of measuring tothe nearest 0.00005 in. (1.25 m).4.4 Dimensional Measuring Device, capable of measuringto the nearest 0.001 in. (25 m).5. Test Specimen5.1 A resistance test strip of printed and cured conductivematerial with a minimum length (L) to width (W) ratio of 50:1(equa
10、l to or greater than 50 squares). A pattern of membraneswitch circuitry is sufficient if a straight measurable strip, witha minimum length (L) to width (W) ratio of 50:1 (equal to orgreater than 50 squares), is available. The accuracy of theresistivity determination will be improved as the number of
11、squares of the resistance test strip is increased.6. Procedure6.1 Pre-Test Setup:6.1.1 Secure switch/test pattern (that is, printed and curedconductive material) on the test surface.6.1.2 Measure the geometry of the test pattern as follows:6.1.2.1 Measure the length (L) of the printed test pattern.6
12、.1.2.2 Measure the width (W) of the printed test pattern.6.1.2.3 Divide the length (L) by the width (W) to calculatethe number of squares of the printed test pattern. Should be$50 squares.NOTE 1Measuring the length (L) and width (W) of the actual printedpattern checks the accuracy of the actual numb
13、er of squares printed versusthe artwork.6.2 In-Process Test:1This test method is under the jurisdiction of Committee F01 on Electronics ,and is the direct responsibility of Subcommittee F01.18 on Membrane Switches.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1998.
14、 Last previous edition approved in 1998 as F 1896-98.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2.1 Using the resistance measuring device (that is, ohmmeter), measure the resistance of the printed test pattern. Placeprobes at
15、ends of measured length of the test pattern as shownin Fig. 1.6.2.2 Record resistance in ohms.6.2.3 Using the thickness measuring device, measure thethickness (t) of the printed test pattern in mils, measure in aminimum of three locations across the test pattern.6.2.4 Record average thickness (t) in
16、 mils (1 mil = 25 m).6.3 Calculations:6.3.1 Determine the number of squares of the printed testpattern by dividing the length (L) by the width (W). Record thenumber of squares.6.3.2 Determine the ohms per square by dividing the mea-sured resistance (in ohms) by the number of squares. Recordthe ohms
17、per square.6.3.3 Determine the resistivity (ohms per square per mil) ofthe conductive material by multiplying the ohms per square bythe measured thickness (t) in mils. Record the resistivity of theconductive material (ohms per square per mil).6.3.4 Examples:6.3.4.1 Example No. 1 is as follows:Resist
18、ance Measurement: 3.0 VThickness (t) Measurement: 0.50 mils (12.5 m)Number of Squares: 100 squaresOhms per square = 3.0 V/100 squaresOhms per square = 0.03 V per squareResistivity (ohms per square per mil) = 0.03 V per square 3 0.50 milsResistivity (ohms per square per mil) = 0.0156.3.4.2 Example No
19、. 2 is as follows:Resistance Measurement: 3.0 VThickness (t) Measurement: 12.5 mNumber of Squares: 100 squaresOhms per square = 3.0 V/100 squaresOhms per square = 0.03 V per squareResistivity (ohms per square per inch) = 0.03 V per square 3 0.0005in.Resistivity (ohms per square per inch) = 0.000015R
20、esistivity (ohms per square per mil) = 0.000015 3 1000 mils per inchResistivity (ohms per square per mil) = 0.0157. Report7.1 Report the following information:7.1.1 Temperature,7.1.2 Humidity,7.1.3 Barometric pressure,7.1.4 Resistance (ohms),7.1.5 Number of squares,7.1.6 Thickness (t) of the test pa
21、ttern,7.1.7 Resistivity (ohms per square per mil),7.1.8 Part number or description, or both, of the testpattern/switch,7.1.9 Identify termination points, and7.1.10 Date of test.8. Precision and Bias8.1 The precision and bias of this test method are underinvestigation. The accuracy of the resistivity
22、 determination willbe improved as the number of squares of the resistance teststrip is increased. The accuracy of the resistivity determinationwill be improved as the width (W) of the circuitry test patternis increased, with 500 to 1000 m being recommended whilethe precision and bias are being inves
23、tigated. Some conductivematerials resistivity are sensitive to temperature and thetemperature of the test specimen should be noted and recorded.9. Keywords9.1 conductive material; membrane switch; resistivityFIG. 1 Resistance Measurement Test Set-UpF 1896 98 (2004)2ASTM International takes no positi
24、on 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
25、.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
26、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 sh
27、own below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F 1896 98 (2004)3
