1、Designation: E493/E493M 11 (Reapproved 2017)Standard Practice forLeaks Using the Mass Spectrometer Leak Detector in theInside-Out Testing Mode1This standard is issued under the fixed designation E493/E493M; the number immediately following the designation indicates the yearof original adoption or, i
2、n the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope
3、1.1 This practice2covers procedures for testing devices thatare sealed prior to testing, such as semiconductors, hermeti-cally enclosed relays, pyrotechnic devices, etc., for leakagethrough the walls of the enclosure. They may be used withvarious degrees of sensitivity (depending on the internalvolu
4、me, the strength of the enclosure, the time available forpreparation of test, and on the sorption characteristics of theenclosure material for helium). In general practice the sensi-tivity limits are from 1010to 106Pa m3/s (109standardcm3/s to 105standard cm3/s at 0C) for helium, although theselimit
5、s may be exceeded by several decades in either directionin some circumstances.1.2 Two test methods are described:1.2.1 Test Method ATest part preparation by bombing.1.2.2 Test Method BTest part preparation by prefilling.1.3 UnitsThe values stated in either SI or std-cc/sec unitsare to be regarded se
6、parately as standard. The values stated ineach system may not be exact equivalents: therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This standard does not purport to address all of thesafety conce
7、rns, 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.1.5 This international standard was developed in accor-dance with internationally r
8、ecognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3E1316 Terminology
9、 for Nondestructive Examinations2.2 Other Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification in Nondestructive Testing4ANSI/ASNT CP-189 ASNT Standard for Qualification andCertification of Nondestructive Testing Personnel4MIL-STD-410 Nondestructive Testing Personn
10、el Qualifica-tion and Certification5NAS-410 Certification and Qualification of NondestructiveTest Personnel63. Terminology3.1 DefinitionsFor definitions of terms used in thispractice, see Terminology E1316, Section E.4. Summary of Practice4.1 The test methods covered in this practice require that th
11、etest part contain helium at some calculable pressure at the timeof test. If the device cannot be sealed with a known pressure ofhelium inside, it is necessary to “bomb” the part in a heliumpressure chamber in order to introduce helium into the test partif a leak exists.4.2 After the test part has b
12、een subjected to helium pressur-izing means, it is placed in an enclosure which is thenevacuated and coupled to a mass spectrometer leak detector. In1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.08 on Le
13、akTesting Method.Current edition approved June 1, 2017. Published July 2017. Originally approvedin 1973. Last previous edition approved in 2011 as E493 - 11. DOI: 10.1520/E0493_E0493M-11R17.2The inside-out testing mode is characterized by an external vacuum and internalpressure. This standard covers
14、 “evacuated,” “sealed with tracer,” and “air-sealed”testing procedures shown in Terminology E1316.3For referenced 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 Docu
15、ment Summary page onthe ASTM website.4Available fromAmerican Society for Nondestructive Testing (ASNT), P.O. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518, http:/www.asnt.org.5Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 1
16、9111-5098, http:/dodssp.daps.dla.mil.6Available from Aerospace Industries Association of America, Inc. (AIA), 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United S
17、tatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to
18、Trade (TBT) Committee.1the event of a leak, an output signal will be obtained from theleak detector. If the actual leak rate of the test part must beknown, this must then be calculated from the output readingand the test parameters.5. Personnel Qualification5.1 If specified in the contractual agreem
19、ent, personnelperforming examinations to this practice shall be qualified inaccordance with a nationally-recognized NDT personnel quali-fication practice or standard, such as ANSI/ASNT CP-189,SNT-TC-1A, MIL-STD-410, NAS-410, or a similar documentand certified by the employer or certifying agency, as
20、 appli-cable. The practice or standard used and its applicable revisionshall be identified in the contractual agreement between theusing parties.6. Significance and Use6.1 MethodsAor B are useful in testing hermetically-sealeddevices with internal volumes. Maximum acceptable leak rateshave been esta
21、blished for microelectronic devices to assureperformance characteristics will not be affected by in-leakageof air, water vapor or other contaminants over the projected lifeexpected. Care must be taken to control the bombing pressure,bombing time and dwell time after bombing or the results canvary su
22、bstantially.7. Interferences7.1 Surface fissures, paint, dirt, polymer seals, etc., can allsorb helium during the bombing procedure and will contributeto the output signal on the leak detector. Unless this process isuniform and consistent, such that nonleaking test parts alwaysgive the same helium s
23、ignal, the test sensitivity is limited bythe background signal from sorbed helium. Either one or bothprocedures of nitrogen “washing” or baking parts for 30 minbetween bombing and testing will sometimes help to reducethis background signal.7.2 In the case of large leaks or very small internal volume
24、sin the test parts, the helium presumably sealed or bombed intothe test part may have escaped prior to testing on the massspectrometer leak detector. The test must be made for largeleaks within a few seconds after removing the parts from thebomb or an alternate test method for large leaks must beemp
25、loyedbubble testing,7liquid bombing and weightchange. If the method for finding large leaks uses a liquid itmust be performed after the helium leak test to avoid sealingthe fine leaks.8. Apparatus8.1 Mass Spectrometer Leak Detector (MSLD).8.2 Roughing Pump, to remove air from the test enclosure inwh
26、ich the test part is placed together with pressure-measuringmeans and suitable valving to connect the test enclosure to theleak detector after evacuating the test enclosure.8.3 Pressure Vessel, capable of safely withstanding thedesired helium “bombing” pressure. The pressure containersmust meet appl
27、icable safety codes for pressure vessels.9. Materials9.1 Helium supply from a regulated source.9.2 Liquid Nitrogen supply (if required by mass spectrom-eter leak detector).9.3 Dry Air or Nitrogen (if required) for washing surfacehelium from test objects.10. Calibration10.1 Calibrate the mass spectro
28、meter leak detector (MSLD)with a calibrated leak to read directly in Pa m3/s or standardcm3/s of helium in accordance with the manufacturers instruc-tions.11. Procedure11.1 Test Method A (Bombing):11.1.1 Place a quantity of sealed parts to be tested in apressure vessel.11.1.2 Then either flush the p
29、ressure vessel with helium orevacuate the vessel (the latter is preferred).11.1.3 Seal and pressurize the vessel with helium to thespecified pressure.11.1.4 Hold at the specified pressure for the time, T,required to give the desired test sensitivity (see 11.1.10) andpressure.11.1.5 Release the heliu
30、m at a considerable distance fromthe leak detector. (It may be piped out of the building orreleased into a holding tank to avoid raising the ambient heliumpressure in the test area.)11.1.6 Remove the test parts from the pressure vessel andflush with helium-free dry air or nitrogen to remove sorbedhe
31、lium from the surface. The flush time can be determinedexperimentally.11.1.7 Place the objects to be tested singly or in multiples inthe MSLD test enclosure and test.11.1.8 Record the indicated leak rate of each part and thelength of time in seconds that the part has been out of thepressure vessel.
32、(If multiple parts have been tested simultane-ously and the MSLD indicates a leak, test the parts individuallyand note the leak rate of each part and the time in seconds thatit has been out of the pressure vessel.)11.1.9 To find the actual leak rate of a given part, thefollowing simplified equation
33、can be used, assuming molecularflow:indicated leak rate = bombing pressure % entering in bomb-ing % of this remaining actual leak rate, more formallydefined as:St5PePo1 2 e23600aT!e2at!Lwhere:St= indicated leak rate (Pa m3/s or standard cm3/s),Pe= bombing pressure of helium in kPa (psia),Po= atmosph
34、eric pressure in kPa (psia),T = bombing time (h),t = waiting time (s) between bombing and testing,L = actual leak rate (Pa m3/s or standard cm3/s) (Note 1),a = L/V where V = internal volume (cm3), and7For further information on leak-testing terminology, see Terminology E1316.E493/E493M 11 (2017)2e =
35、 2.71 (natural logarithm).11.1.9.1 The actual leak rate thus calculated will in no casebe smaller than the actual leak, hence a safety factor is built in.811.1.10 If Peis known, T can be kept constant in a repetitiveprocess, and a desired maximum leak level L is known, a safereject point for the MSL
36、D leak rate indication (St) may becalculated by using the equation in 11.1.9. The maximum valueof t should be used.NOTE 1The value that would be measured if the cavity contained100 % trace gas at atmospheric pressure.11.2 Test Method BFilling with helium prior to sealing:11.2.1 Fill the test part wi
37、th helium at a known pressureprior to sealing.11.2.2 Seal the test parts to be tested.11.2.3 Same as 11.1.7.11.2.4 Same as 11.1.8.11.2.5 To find the actual leak rate of a given part, omit thefirst bracket of the equation shown in 11.1.9 as follows:St5PePoe2at!L11.2.6 If a and Pe/Poare constants in a
38、 repetitive processand a desired maximum leak level L is known, a safe rejectpoint for the MSLD leak rate indication (St) may be calculatedby using the equation in 11.2.5. The maximum value of tshould be used.12. Keywords12.1 bell jar leak test; bomb mass spectrometer leak test;helium leak test; hel
39、ium leak testing; leak testing; massspectrometer leak testing; sealed object mass spectrometer leaktestASTM 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 d
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43、ts (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). Permission rights to photocopy the standard may also be secured from the Copy
44、right Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ of computer solutions to the equation given in 11.1.9 for various valuesof V, L, T and t commonly encountered in practice is available on request fromVarian Vacuum Division/NRC Operation, 160 Charlemont St., Newton, MA 02161.E493/E493M 11 (2017)3
