1、Designation: E493/E493M 11Standard 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, in the case of revi
2、sion, 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 Department of Defense.1. Scope*1.1 This practice2cove
3、rs 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 internalvolume, the strength of th
4、e 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 theselimits may be exceeded by s
5、everal 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 separately as standard.
6、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 concerns, if any, associate
7、d 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. Referenced Documents2.1 ASTM Standards:3E1316 Terminology for Nondestructive Examinations2.2 Other Doc
8、uments: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 Personnel Qualifica-tion and Certification5NAS-410 C
9、ertification and Qualification of NondestructiveTest Personnel63. Terminology3.1 DefinitionsFor definitions of terms used in this prac-tice, see Terminology E1316, Section E.4. Summary of Practice4.1 The test methods covered in this practice require that thetest part contain helium at some calculabl
10、e 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 been subjected to helium pressur-izing means
11、, it is placed in an enclosure which is then1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.08 on LeakTesting Method.Current edition approved July 1, 2011. Published July 2011. Originally approvedin 1973.
12、Last previous edition approved in 2006 as E493 - 06. DOI: 10.1520/E0493_E0493M-11.2The inside-out testing mode is characterized by an external vacuum and internalpressure. This standard covers “evacuated,” “sealed with tracer,” and “air-sealed”testing procedures shown in Terminology E1316.3For refer
13、enced 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.4Available fromAmerican Society for NondestructiveTesting (ASNT), P.O.
14、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 19111-5098, http:/dodssp.daps.dla.mil.6Available from Aerospace Industries Association of America, Inc. (AIA),
15、 1000Wilson Blvd., Suite 1700,Arlington, VA22209-3928, http:/www.aia-aerospace.org.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.evacuated and coupled to a mass spec
16、trometer leak detector. Inthe 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 agr
17、eement, 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,
18、 as 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 e
19、stablished 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
20、 substantially.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 heliu
21、m signal, 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 vol
22、umesin 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 be
23、employedbubble 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 i
24、nwhich 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 a
25、pplicable 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 spec
26、trometer 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 th
27、e pressure 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 he
28、lium 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 sorbe
29、dhelium 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 vesse
30、l. (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 equati
31、on can be used, assuming molecularflow:indicated leak rate = bombing pressure 3 % entering in bomb-ing 3 % of this remaining 3 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
32、= atmospheric 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), ande = 2.71 (natural logarithm).7For further information on leak-testing terminology, see Term
33、inology E1316.E493/E493M 11211.1.9.1 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 M
34、SLD 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
35、with 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
36、 a repetitive process anda desired maximum leak level L is known, a safe reject pointfor the MSLD leak rate indication (St) may be calculated byusing the equation in 11.2.5. The maximum value of t shouldbe used.12. Keywords12.1 bell jar leak test; bomb mass spectrometer leak test;helium leak test; h
37、elium leak testing; leak testing; massspectrometer leak testing; sealed object mass spectrometer leaktestSUMMARY OF CHANGESCommittee E07 has identified the location of selected changes to this standard since the last issue (E493 - 06)that may impact the use of this standard. (July 1, 2011)(1) Change
38、d type of standard from Test Method to Practice.(2) Added combined units statement in 1.3.(3) Changed SI units of mol/s to Pa m3/s in 1.1.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this st
39、andard 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.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years a
40、ndif 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 International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee,
41、 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 shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
42、59,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). Permission rights to photocopy the standar
43、d may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).8Atable 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 113
