ASTM E493-97

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Designation:E493–97
Standard Test Methods for
Leaks Using the Mass Spectrometer Leak Detector in the
Inside-Out Testing Mode
This standard is issued under the fixed designation E493; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Terminology
1.1 These test methods cover procedures for testing de- 3.1 Definitions—For definitions of terms used in this stan-
vices that are sealed prior to testing, such as semiconductors, dard, see Terminology E1316, Section E.
hermetically enclosed relays, pyrotechnic devices, etc., for
4. Summary of Test Methods
leakage through the walls of the enclosure. They may be used
with various degrees of sensitivity (depending on the internal 4.1 These test methods require that the test part contain
helium at some calculable pressure at the time of test. If the
volume, the strength of the enclosure, the time available for
preparation of test, and on the sorption characteristics of the device cannot be sealed with a known pressure of helium
inside, it is necessary to “bomb” the part in a helium pressure
enclosure material for helium). In general practice the sensi-
−15 −11 −9
tivity limits are from 4.4 310 to 4.4 310 moles/s (10 chamber in order to introduce helium into the test part if a leak
3 −5 3
exists.
standard cm /s to 10 standard cm /s at 0°C) for helium,
although these limits may be exceeded by several decades in 4.2 After the test part has been subjected to helium pressur-
izing means, it is placed in an enclosure which is then
either direction in some circumstances.
1.2 Two test methods are described: evacuatedandcoupledtoamassspectrometerleak detector. In
the event of a leak, an output signal will be obtained from the
1.2.1 Test Method A—Test part preparation by bombing.
1.2.2 Test Method B—Test part preparation by prefilling. leak detector. If the actual leak rate of the test part must be
known, this must then be calculated from the output reading
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the and the test parameters.
responsibility of the user of this standard to establish appro-
5. Personnel Qualification
priate safety and health practices and determine the applica-
5.1 It is recommended that personnel performing leak test-
bility of regulatory limitations prior to use.
ing attend a dedicated training course on the subject and pass
2. Referenced Documents
a written examination.The training course should be appropri-
2.1 ASTM Standards: ate for NDT level II qualification according to Recommended
Practice No. SNT-TC-1A of the American Society for Nonde-
E1316 Terminology for Nondestructive Examinations
2.2 Other Documents: structive Testing or ANSI/ASNT Standard CP-189.
SNT-TC-1A Recommended Practice for Personnel Qualifi-
6. Significance and Use
cation and Certification in Nondestructive Testing
6.1 MethodsAorBareusefulintestinghermetically-sealed
ANSI/ASNT CP-189 ASNT Standard for Qualification and
devices with internal volumes. Maximum acceptable leak rates
Certification of Nondestructive Testing Personnel
have been established for microelectronic devices to assure
performance characteristics will not be affected by in-leakage
ofair,watervapororothercontaminantsovertheprojectedlife
These test methods are under the jurisdiction of ASTM Committee E-7 on
NondestructiveTestingandarethedirectresponsibilityofSubcommitteeE07.08on
expected. Care must be taken to control the bombing pressure,
Leak Testing.
bombing time and dwell time after bombing or the results can
Current edition approved May 10, 1997. Published February 1998. Originally
vary substantially.
published as E493–73. Last previous edition E493–94.
Theinside-outtestingmodeischaracterizedbyanexternalvacuumandinternal
7. Interferences
pressure. This document covers “evacuated,” “sealed with tracer,” and “air-sealed”
testing procedures shown in Terminology E1316.
7.1 Surface fissures, paint, dirt, polymer seals, etc., can all
Annual Book of ASTM Standards, Vol 03.03.
4 sorb helium during the bombing procedure and will contribute
Available from American Society for Nondestructive Testing, 1711 Arlingate
Plaza, P.O. Box 28518, Columbus, OH 43228-0518. to the output signal on the leak detector. Unless this process is
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E493–97
uniform and consistent, such that nonleaking test parts always 11.1.6 Remove the test parts from the pressure vessel and
give the same helium signal, the test sensitivity is limited by flush with helium-free dry air or nitrogen to remove sorbed
the background signal from sorbed helium. Either one or both helium from the surface. The flush time can be determined
procedures of nitrogen “washing” or baking parts for 30 min experimentally.
between bombing and testing will sometimes help to reduce
11.1.7 Placetheobjectstobetestedsinglyorinmultiplesin
this background signal.
the MSLD test enclosure and test.
7.2 In the case of large leaks or very small internal volumes
11.1.8 Record the indicated leak rate of each part and the
in the test parts, the helium presumably sealed or bombed into
length of time in seconds that the part has been out of the
the test part may have escaped prior to testing on the mass
pressure vessel. (If multiple parts have been tested simulta-
spectrometer leak detector. The test must be made for large
neouslyandtheMSLDindicatesaleak,testthepartsindividu-
leaks within a few seconds after removing the parts from the
ally and note the leak rate of each part and the time in seconds
bomb or an alternate te
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