1、Designation: F 1996 06Standard Test Method forSilver Migration for Membrane Switch Circuitry1This standard is issued under the fixed designation F 1996; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A n
2、umber 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 is used to determine the susceptibilityof a membrane switch to the migration of the silver betweencircuit traces under
3、 dc voltage potential.1.2 Silver migration will occur when special conditions ofmoisture and electrical energy are present.2. Referenced Documents2.1 ASTM Standards:2F 1596 Practice for Exposure of Membrane Switches toTemperature and Relative HumidityF 1689 Test Method for Determining the Insulation
4、 Resis-tance of a Membrane Switch3. Terminology3.1 Definitions:3.1.1 silver migrationA process by which silver, when incontact with insulating materials under electrical potential, isremoved ionically from its original location, and is redeposit asa metal (silver dendrite) at some other location.4.
5、Significance and Use4.1 The effects of silver migration are short circuiting orreduction in insulation resistance. It is evidenced by staining ordicoloration between the cathode and anode conductive traces.4.2 Accelerated testing may be accomplished by increasingthe voltage over the specified voltag
6、es. (Atypical starting pointwould be 5Vdc 50mA).5. Interferences5.1 The following parameters may affect the results of thistest:5.1.1 Temperature.5.1.2 Relative Humidity.5.1.3 Electrical Load (that is, current and voltage).5.1.4 Test surface.5.1.5 Flex tail connector area may be susceptible to silve
7、rmigration which may or may not be a part of the scope of thistest. If the flex tail is to be excluded from the test it should besealed with an inert compound that has no influence on the testor switch materials.5.1.6 Post test handling may damage or destroy silverdendrites.5.1.7 Dendrites normally
8、grow from the cathode conductorto the anode. To test both electrodes of a switch design connectreplicate specimens so that current flows through them inopposite directions.5.1.8 Without limited current, the migration could occur,causing a short and a dramatic current surge, which thendestroys the sh
9、ort and returns the circuit to a nonstandard, butfunctional condition. If an observer was not present (or thedetails were not continuously recorded) this most dramaticfailure might go unnoticed.6. Apparatus6.1 Closed Environmental System, with temperature andhumidity control (see Practice F 1596).6.
10、2 Current-Limiting DC Power Source. (Series currentlimiting resistor may be used with dc power supply).6.3 Milliamp Meter (see Test Method F 1689).6.4 Megohm Meter.6.5 Test Surface, flat, smooth, unyielding, nonporous, andlarger than switch under test.7. Procedure7.1 Pretest Setup:7.1.1 Test specime
11、n(s) shall be permitted to stabilize at 20 to25C and 40 to 60 % relative humidity (RH) for a minimum of24 h.7.2 Test Setup (Fig. 1):7.2.1 Secure switch on test surface and measure initialinsulation resistance between test points and record results.Protect connector as necessary (see 5.1.5).7.2.2 Ori
12、ent switch and flex tail in positions that simulatethe end use application positions unless otherwise specified.The flex tail orientation (bent down, up or back) may differfrom the orientation of the switch (horizontal, vertical orangled).7.2.3 Connect power supply leads to test points.1This test me
13、thod is under the jurisdiction of ASTM Committee F01 onElectronics , and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved July 1, 2006. Published July 2006. Originally approvedin 1999. Last previous edition approved in 2001 as F 199601.2For referenced
14、ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Consh
15、ohocken, PA 19428-2959, United States.7.3 In Process Test:7.3.1 Apply voltage to the test points. Limit the current toprevent high current from disintegrating the dendrites causedby silver migration. Use a current limiting resistor to limit thecurrent to 2 milliamps or less. (See Fig. 1)7.3.2 Expose
16、 test specimen(s) to specified temperature andhumidity while under electrical load for a specified duration,(for example, 10 days at 55C/85 % RH). The ramp rate to thespecified test set points (temperature and humidity) should bechosen to maintain a non-condensing environment.7.3.3 After specified d
17、uration disconnect power supply andremove from chamber. Allow to stabilize following 7.1.1.7.4 Post Test:7.4.1 Measure final insulation resistance between test pointsand record results.7.4.2 An insulation resistance measurement below specifiedvalue constitutes a failure of this test.7.4.3 If a failu
18、re, inspect visually (without magnification)for staining or discoloration.8. Report8.1 Report the following information:8.1.1 Humidity,8.1.2 Temperature,8.1.3 Voltage,8.1.4 Current limit value,8.1.5 Specified duration,8.1.6 Schematic of unit under test indicating circuit connec-tions and polarity,8.
19、1.7 Initial insulation resistance, final insulation resistance,pass/fail,8.1.8 Results of visual inspection,8.1.9 Mounting substrate and orientation of switch and flexduring test, and8.1.10 Note if flex tail connector is sealed and with whatpotting material.9. Keywords9.1 membrane switch; silver den
20、drite; silver migrationASTM 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 infringem
21、ent 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
22、 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 kn
23、own 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. 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).FIG. 1 Test SetupF1996062
