1、Designation: F1263 11Standard Guide forAnalysis of Overtest Data in Radiation Testing of ElectronicParts1This standard is issued under the fixed designation F1263; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers the use of overtesting in order toreduce the required number of parts that must be tested to meeta given qu
3、ality acceptance standard. Overtesting is testing asample number of parts at a stress level higher than theirspecification stress in order to reduce the amount of necessarydata taking. This guide discusses when and how overtestingmay be applied to forming probabilistic estimates for thesurvival of e
4、lectronic piece parts subjected to radiation stress.Some knowledge of the probability distribution governing thestress-to-failure of the parts is necessary, although exactknowledge may be replaced by over-conservative estimates ofthis distribution.2. Referenced Documents2.1 Military Standards:MIL-PR
5、F 19500 Semiconductor Devices, General Specifi-cations for2MIL-PRF 38535 Integrated Circuits (Microcircuit Manu-facturing)23. Terminology3.1 Description of Term:3.1.1 Confidencethe probability, C, that at least a fraction,P, of the electronic parts from a test lot will survive in actualservice; sinc
6、e radiation testing of electronic parts is generallydestructive, this probability must be calculated from tests onselected specimens from the lot.3.1.2 Rejection Confidencethe probability, R, that a lotwill be rejected based on destructive tests of selected speci-mens if more than a specified fracti
7、on, P, of the parts in the lotwill fail in actual service.3.1.3 Discussion of Preceding TermsStrictly speaking,most lot acceptance tests (be they testing by attributes orvariables) do not guarantee survivability, but rather that infe-rior lots, where the survival probability of the parts is less tha
8、nprobability, P, will be rejected with confidence, C. In order toinfer a true confidence, it would require a Bayes Theoremcalculation. In many cases, the distinction between confidenceand rejection confidence is of little practical importance.However, in other cases (typically when a large number of
9、 lotsare rejected) the distinction between these two kinds ofconfidence can be significant. The formulas given in this guideapply whether one is dealing with confidence or rejectionconfidence.4. Summary of Guide4.1 This guide is intended to primarily apply to sampling byattribute plans typified by L
10、ot Tolerance Percent Defective(LTPD) tables given in MIL-PRF 38535 and MIL-PRF 19500,and contains the following:4.1.1 An equation for estimating the effectiveness of over-testing in terms of increased probability of survival,4.1.2 An equation for the required amount of overtestinggiven a necessary s
11、urvival probability, and4.1.3 Cautions and limitations on the method.5. Significance and Use5.1 Overtesting should be done when (a) testing by vari-ables is impractical because of time and cost considerations orbecause the probability distribution of stress to failure cannotbe estimated with suffici
12、ent accuracy, and (b) an unrealisticallylarge number of parts would have to be tested at the specifi-cation stress for the necessary confidence and survival prob-ability.6. Interferences6.1 Probability DistributionsIn overtesting, a knowledgeof the probability distribution governing stress to failur
13、e isrequired, though it need not be specified with the sameaccuracy necessary for testing by variables. For bipolar tran-sistors exposed to neutron radiation, the failure mechanism isusually gain degradation and the stress to failure is known tofollow a lognormal distribution.3For bipolar transistor
14、s ex-posed to total dose the use of the lognormal distribution is also1This guide is under the jurisdiction of ASTM Committee F01 on Electronicsand is the direct responsibility of Subcommittee F01.11 on Nuclear and SpaceRadiation Effects.Current edition approved June 1, 2011. Published July 2011. Or
15、iginally approvedin 1989. Last previous edition approved in 2005 as F1263 99(2005). DOI:10.1520/F1263-11.2Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.3Messenger, G. C., Steele, E. L., “Statistical Modeling of Semic
16、onductorDevices for the TREE Environment, Transactions on Nuclear Science NS-15,1968, p. 4691.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.fairly accurate.4For more complex electronics and other kindsof radiation stress, the logno
17、rmal distribution is widely used inestimating the failure probabilities of electronic piece parts,and therefore this standard governs the use of a lognormaldistribution. However, caution should be exercised when theprobability distribution of stress to failure is not well estab-lished. Nevertheless,
18、 even if the lognormal distribution doesnot strictly apply, the equations given in Section 7 will hold aslong as a sufficiently conservative estimate was made of thevariability of the parts within the stress range of interest.56.2 Time Dependent Post Radiation EffectsIn total dosetesting annealing a
19、nd rebound effects can affect the results.7. Equations and Tabulations for Overtesting7.1 Let RTand RSbe the respective overtest (radiation levelat which the test is performed) and specification stresses(specification radiation level). Let sln(max) be an estimatedmaximum standard deviation in the na
20、tural logarithms of thestress to failure, and let PTand PSbe the respective survivalprobabilities with confidence, C, at the overtest and stresslevels. Then,PS5 FFFPT! 1lnRT/RS!slnmax!G, (1)where:F = the cumulative standard normal probability distribu-tion, andF= the anti-function of F where FF(X) =
21、 X.Most probability texts tabulate the cumulative standardnormal probability distribution function, F, and its antifunction(sometimes denoted by Zp).7.1.1 When PSis given and PTis known, the overtest factoris:RT/RS5 exp$slnmax! FPS! 2 FPT!#% (2)7.2 For neutrons, 0.5 is a good estimate of sln(max).5,
22、67.2.1 Example:Suppose bipolar transistors are tested at a neutron fluencethree times the specification fluence and it is determined thatwith 90 % confidence, at least 80 % of the transistors willsurvive the overtest fluence. Then from Eq 1, at the specifica-tion fluence, with 90 % confidence, the s
23、urvival probability isas follows:PS5 FFPT! 1 ln 3! / 0.5 5 F0.84 1 2.20 5 F3.04 5 0.999,where we used the following facts governing the normaldistribution:Standard probability tables such as those shown in M.G.Natrella, “Experimental Statistics,” NBS Handbook 91, U.S.Dept. of Commerce (1966) shows t
24、hat F(0.8) = 0.84. The 80percentile point of the distribution is 0.84 standard deviationsabove the mean of the distribution (80 % of the distribution isbelow 0.84 standard deviations above the mean).The number 3.04 is approximately the 99.9 percentile ofthe distribution. This result means that lots
25、will be rejected with90 % confidence unless 99.9 % of these parts survive one timesthe specification fluence. The three times overtest has thusraised the requirement on the lot quality to a value whichwould otherwise require testing an excessively large number ofparts.57.3 Table 1 gives examples of
26、the estimated survival prob-ability as a function of R, where R depends on the overtestfactor and the estimated maximum logarithmic standard devia-tion in stress-to-failure as follows:R 5lnRT/RS!slnmax!(3)7.3.1 Sample Use of Table 1:If an overtest were performed with R = 1.5, and if it is knownthat
27、a certain part type has stresses-to-failure that never vary upor down by more than a factor of 4, that is sln(max) = ln(4),then the overtest level would be 1.5 =ln(RT/RS)ln4 and RT/RS=e1.5ln4= 8 or 41.5= 8 times the specification level. If it weredetermined that with 90 % confidence, C, 80 % of the
28、partswould survive the overtest level, then since the table shows thatat the specification level, with confidence, C, the table showsthat 0.990400 or an estimated 99 % of the parts would survive.Alternatively, given the data at the specification level, thedesired part survivability and a factor that
29、 bounds the variabil-ity of the parts, this table can be used to determine an overtestlevel.7.3.2 Cautions for Using Table 1:Be aware that clearly a survival probability of 1.0 isunrealistic, and where it appears, the table should be inter-preted to mean that there would be no point in going to a hi
30、gherlevel of overtest than the one indicated in the table. In general,very high probabilities of survival should not be taken literallybecause errors in the assumed probability distribution, unex-pected results, maverick parts, simulation fidelity, and humanerror, all affect a practical situation.An
31、 experienced user wouldhave some idea of the maximum credible survivability for theparticular application. It is suggested here that probabilities ofover 0.999999 are not credible unless massive experience4Stanley, A. G., Martin, K. E., and Price, W. E., “Hardness Assurance for TotalDose RadiationFi
32、nal Report, No. 730-2, Jet Propulsion Laboratory, Pasadena,CA 1977.5Namenson, A. I., “Hardness Assurance and Overtesting, IEEE Transactionson Nuclear Science NS-29, 1982, p. 1821.6Namenson, A. I., “Statistical Treatment of Damage Factors for SemiconductorDevices, IEEE Transactions on Nuclear Science
33、 NS-26, 1979, p. 4691.TABLE 1 Survival Probability at Specification Level Versus R and Survival Probability at Overtest LevelSpecification Level Probability for:Overtest LevelProbabilityR =0.5 R =1.0 R =1.5 R =2.0 R =3.0 R =5.00.50 0.691462 0.841345 0.933193 0.977250 0.998650 1.0000000.80 0.910140 0
34、.967235 0.990400 0.997756 0.999939 1.0000000.90 0.962588 0.988742 0.997295 0.999484 0.999991 1.0000000.95 0.984016 0.995913 0.999169 0.999866 0.999998 1.000000F1263 112shows that tests, part processing, and the personnel are reliableto at least that level of confidence. Nevertheless, if a very highl
35、evel of survival is predicted, the information suggests that anyweak point in a system is most likely somewhere else.8. Keywords8.1 confidence; rejection; overtest data; statistical analysisASTM International takes no position respecting the validity of any patent rights asserted in connection with
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37、al 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 for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration
38、 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 known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbo
39、r 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).F1263 113
