ASTM_F_2750_-_09.pdf

Designation:F275009Standard Test Method forDetermining the Effects of Bending a Membrane Switch orAssembly1This standard is issued under the fixed designation F2750;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last 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 The 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-priate 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 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 abrazing 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 their 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.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 orientation of the conductor(either extension or com-pression)could have significant impact on the results.NOTE1Experience has shown that some conductors recover theirconductive properties if allowed to stabilize after the dynamic portion ofthe test.Therefore,continuous monitoring is recommended.5.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 the sample.5.4 Equipment for the monitoring and recording of resis-tance.NOTE2Experience 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 samples 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).6.2 The width of the test sample must not exceed the lengthof the mandrel.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics 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 F2750-08.DOI:10.1520/F2750-09.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 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 Testing conductor side ofthe test sample faces the mandrel.7.1.2 Extension Conductor Testing conductor 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 tension).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.NOTE3Experience has shown that some conductors recover theirconductive properties if allowed to stabilize after the dynamic portion ofthe 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.(T