1、Designation: E 493 06Standard Test Methods forLeaks Using the Mass Spectrometer Leak Detector in theInside-Out Testing Mode1This standard is issued under the fixed designation E 493; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods2cover procedures for testing de-vices that are sealed prior to testing, such as semico
3、nductors,hermetically enclosed relays, pyrotechnic devices, etc., forleakage through the walls of the enclosure. They may be usedwith various degrees of sensitivity (depending on the internalvolume, the strength of the enclosure, the time available forpreparation of test, and on the sorption charact
4、eristics of theenclosure material for helium). In general practice the sensi-tivity limits are from 4.4 3 1015to 4.4 3 1011moles/s (109standard cm3/s to 105standard cm3/s at 0C) for helium,although these limits may be exceeded by several decades ineither direction in some circumstances.1.2 Two test
5、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 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
6、 appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E 1316 Terminology for Nondestructive Testing2.2 Other Documents:SNT-TC-1A Recommended Practice for Personnel Qualifi-cation and Certification
7、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 Certification and Qualification of NondestructiveTest Personnel63. Terminology3.1 Defi
8、nitionsFor definitions of terms used in this stan-dard, see Terminology E 1316, Section E.4. Summary of Test Methods4.1 These test methods require that the test part containhelium at some calculable pressure at the time of test. If thedevice cannot be sealed with a known pressure of heliuminside, it
9、 is necessary to “bomb” the part in a helium pressurechamber in order to introduce helium into the test part if a leakexists.4.2 After the test part has been subjected to helium pressur-izing means, it is placed in an enclosure which is thenevacuated and coupled to a mass spectrometer leak detector.
10、 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 agreement, personnelperfor
11、ming examinations to these test methods shall be quali-fied in accordance with a nationally-recognized NDTpersonnelqualification practice or standard, such as ANSI/ASNT CP-189, SNT-TC-1A, MIL-STD-410, NAS-410, or a similardocument and certified by the employer or certifying agency,as applicable. The
12、 practice or standard used and its applicablerevision shall be identified in the contractual agreement be-tween the using parties.6. Significance and Use6.1 MethodsAor B are useful in testing hermetically-sealeddevices with internal volumes. Maximum acceptable leak rates1These test methods are under
13、 the jurisdiction of ASTM Committee E07 onNondestructive Testing and are the direct responsibility of Subcommittee E07.08 onLeak Testing Method.Current edition approved Feb. 1, 2006. Published February 2006. Originallyapproved in 1973. Last previous edition approved in 1997 as E 493 - 97.2The inside
14、-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 E 1316.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service
15、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. Box28518, 1711 Arlingate Ln., Columbus, OH 43228-0518.5Available from Standardization Docume
16、nts Order Desk, DODSSP, Bldg. 4,Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.6Available from Aerospace Industries Association of America, Inc. (AIA), 1250Eye St., NW, Washington, DC 20005.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,
17、 United States.have been established 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 bomb
18、ing or the results canvary 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
19、 alwaysgive the same helium 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
20、or very small internal volumesin 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 meth
21、od for large leaks must beemployedbubble 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
22、 from the test enclosure inwhich 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 pres
23、sure containersmust meet applicable 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
24、.1 Calibrate the mass spectrometer 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.1
25、1.1.2 Then either flush the 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) andpres
26、sure.11.1.5 Release the helium 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 o
27、r nitrogen to remove sorbedhelium 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 bee
28、n out of thepressure vessel. (If multiple parts have been tested simulta-neously and the MSLD indicates a leak, test the parts individu-ally and note the leak rate of each part and the time in secondsthat it has been out of the pressure vessel.)11.1.9 To find the actual leak rate of a given part, th
29、efollowing simplified equation 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 pressur
30、e of helium (in kPa (psia),Po= 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).11.1.9.1 The actual leak rate thu
31、s 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 MSLD leak rate indication (St) may becalculated by using the e
32、quation 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 with helium at a known pressureprior to sealing.7For further
33、information on leak-testing terminology, see Terminology E 1316.8Atable 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.E49
34、306211.2.2 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 repetitive process anda desired maximum l
35、eak 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. Precision and Bias12.1 PrecisionReplicate tests by the same operator withthe same equipment should be considered suspect if more
36、than.1 % of the devices previously accepted are found to be rejects.The test results for this method need not be considered suspectif less than 1 % of the devices are found to be rejects onsubsequent tests by another facility.12.2 BiasThe bias of the test is on the order of 625 %.The commercially av
37、ailable calibrated leaks have stated uncer-tainties of 610 % of their rated values. This test is not intendedto be a measurement of actual leak rate but a determination ofa leak rate in excess of a specified allowable leak rate.13. Keywords13.1 bell jar leak test; bomb mass spectrometer leak test;he
38、lium leak test; helium 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 expre
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41、ttend. 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 19428-2959,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).E493063
