1、Designation: F 2750 09Standard Test Method forDetermining the Effects of Bending a Membrane Switch orAssembly1This standard is issued under the fixed designation F 2750; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method establishes a method for the bending ofany part of a membrane switch with conductive circuits.1.1.1 Th
3、e values given in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.2 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-pria
4、te safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Terminology2.1 Definitions:2.1.1 bendto force from a straight form into a differentand especially a curved one.2.1.1.1 DiscussionIn this case, no “hard” or angled creaseor fold is to occur. The
5、substrate will only be formed into aradius.2.1.2 bend cyclea bend of a sample around a specifiedmandrel which is “rolled” in one direction, followed by rollingin the opposite direction, returning the sample to its originalposition (see Fig. 1).2.1.3 mandrela cylindrically shaped metal rod, such as a
6、brazing or drill rod.2.1.4 membrane switcha momentary switching device inwhich at least one contact is on, or made of, a flexiblesubstrate.2.1.5 membrane switch taila flexible portion of a mem-brane switch used for input/output connection.3. Significance and Use3.1 Bending of membrane switches or th
7、eir components canaffect their visual appearance, mechanical integrity or electricalfunctionality. This test method simulates conditions that maybe seen during manufacture, installation or use.3.2 Bend testing may be destructive, therefore any samplestested should be considered unfit for future use.
8、3.3 Specific areas of testing include, but are not limited to:3.3.1 Membrane switch flex tails, and3.3.2 Any component of a membrane switch that may besubjected to bending.4. Interferences4.1 The following parameters may affect the results of thistest:4.1.1 temperature,4.1.2 humidity, and4.1.3 orien
9、tation of the conductor (either extension or com-pression) could have significant impact on the results.NOTE 1Experience has shown that some conductors recover theirconductive properties if allowed to stabilize after the dynamic portion ofthe test. Therefore, continuous monitoring is recommended.5.
10、Apparatus5.1 Mandrel, allowed to rotate smoothly around its longitu-dinal axis, rigid, low friction smooth surface. Diameter to bespecified.5.2 Fixture to hold test sample securely in place in a verticalmanner (refer to Fig. 1).5.3 Mechanism capable of providing a consistent force andrate of pull to
11、 the sample.5.4 Equipment for the monitoring and recording of resis-tance.NOTE 2Experience has shown that some conductors recover theirconductive properties if allowed to stabilize after the dynamic portion ofthe test. Therefore, continuous monitoring is recommended.6. Test Samples6.1 The test sampl
12、es may be components, tail assembles orfinished switches. If the sample length is too short for the testfixture, a sample coupon of the same construction (layer tolayer) must be provided (minimum; 250 mm length by 25 mmwidth).1This test method is under the jurisdiction of ASTM Committee F01 onElectr
13、onics and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved June 15, 2009. Published July 2009. Originallyapproved in 2008. Last previous edition approved in 2008 as F 2750-08.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
14、ohocken, PA 19428-2959, United States.6.2 The width of the test sample must not exceed the lengthof the mandrel.7. Procedure7.1 Clamp one end of the test sample to the test fixture thisis the static end of the test sample.7.1.1 Compression Conductor Testingconductor side ofthe test sample faces the
15、mandrel.7.1.2 Extension Conductor Testingconductor side of thetest sample faces away from the mandrel.7.2 Loop the unsecured end of the test sample around themandrel this later becomes the dynamic end of the testsample.7.3 Clamp the unsecured end of the test sample to the liftingmechanism (no tensio
16、n).7.3.1 Ensure that both ends of the test sample remainparallel during motion of test.7.4 Connect to the test sample so that circuit resistance canbe monitored.NOTE 3Experience has shown that some conductors recover theirconductive properties if allowed to stabilize after the dynamic portion ofthe
17、test. Therefore continuous monitoring is recommended.7.4.1 Verify test sample is functional and being monitored.7.5 Apply the minimum tension load of sufficient magnitudesuch that the test sample contacts 50 % of the circumferencesurface of the mandrel. (Typically, this is a kg mass providingthe ten
18、sion load.)7.6 Adjust the test fixture to achieve maximum travel of themandrel by pulling the unsecured end (dynamic end) of the testsample while maintaining 50 % contact with the mandrel.7.7 Start test.7.7.1 Record the closed loop resistance (Ri) - measurementmade on the first test cycle. At the en
19、d of the test, the “Rmaximum” value, which is the largest value using a timeconstant chosen appropriately for the measurement, is re-corded.7.7.2 A cycle is defined as travel from maximum extensionto minimum extension and back to maximum extension.7.7.3 The linear speed of the dynamic end of the tes
20、t sampleshould not exceed 25.4 mm/s.7.8 Repeat cycles until resistance increases by 30 % or moreof Ri for 10 consecutive cycles or the specified number ofcycles are completed. Resistance is to be continuously moni-tored or measured within3sofcycling. Time between cyclesshall not exceed 3 s.7.9 Remov
21、e test sample from test fixture.8. Report8.1 Report the following information:8.1.1 Temperature,8.1.2 Humidity,8.1.3 Resistance measurements, Ri, R maximum,8.1.4 Number of cycles per specimen,8.1.5 Part number or description of specimen,FIG. 1 Test Fixture SetupF27500928.1.6 Date of test,8.1.7 Orien
22、tation of test sample (compression, extension, orboth),8.1.8 Diameter of mandrel, and8.1.9 Load weight.9. Precision and Bias9.1 PrecisionIt is not possible to specify the precision inTest Method F 2750 for measuring bend because inter-laboratory studies have proven inconclusive due to insufficientpa
23、rticipating laboratories with the appropriate equipment.9.2 BiasNo information can be presented on the bias ofthe procedure in Test Method F 2750 for measuring bendbecause no standard sample is available for this industry.10. Keywords10.1 bend; mandrel; membrane switch; tail assemblyASTM Internation
24、al 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
25、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
26、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,
27、 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. 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).F2750093
