1、Designation: F 1263 99 (Reapproved 2005)Standard Guide forAnalysis of Overtest Data in Radiation Testing of ElectronicParts1This standard is issued under the fixed designation F 1263; 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 This guide covers the use of overtesting in order toreduce the required number of parts that must be tes
3、ted to meeta given quality acceptance standard. Overtesting is testing asample number of parts at a stress higher than their specifica-tion stress in order to reduce the amount of necessary datataking. This guide discusses when and how overtesting may beapplied to forming probabilistic estimates for
4、 the survival ofelectronic piece parts subjected to radiation stress. Someknowledge of the probability distribution governing the stress-to-failure of the parts is necessary though exact knowledgemay be replaced by over-conservative estimates of this distri-bution.2. Referenced Documents2.1 Military
5、 Standards:MIL-PRF 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 ac
6、tualservice; since 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 lot willbe rejected based on destructive tests of selected specimens ifmore than a s
7、pecified fraction P of the parts in the lot will failin 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 part
8、s is less thanprobability, 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 la
9、rge number of 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
10、typified by Lot 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
11、a necessary survival 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
12、 with sufficient 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 str
13、ess to failure 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 bipol
14、ar transistors 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 Quality and HardnessAssurance.Current edition approved Jan. 1, 2005. Published Janua
15、ry 2005. Originallyapproved in 1989. Last previous edition approved in 1999 as F 1263 99.2Available 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 SemiconductorDevices
16、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 good.4For more complex electronics and other kinds ofradiation stress, the lognormal distribution is
17、 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, even if the lognorm
18、al 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 and rebound effects c
19、an affect the results.7. Equations and Tabulations for Overtesting7.1 Let RTand RSbe the respective overtest and specifica-tion stresses. Let sln(max) be an estimated maximum standarddeviation in the natural logarithms of the stress to failure, andlet PTand PSbe the respective survival probabilities
20、 withconfidence, C, at the overtest and stress levels. Then,PS5 FFFPT! 1lnRT/RS!slnmax!G, (1)where:F = the cumulative standard normal distribution, andF= the anti-function of the cumulative standard normaldistribution.Most probability texts tabulate the cumulative standardnormal distribution functio
21、n, F, and its antifunction (some-times 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).67.2.1 Example:Suppose bipolar transistors are tested at a neutron fluencethree times the specifi
22、cation 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 survival probability isas follows:PS5 FF1 ln 3! / 0.5 5 F0.84 1 2.20 5 0.999,where we used the fol
23、lowing facts governing the normaldistribution:(a) The 80 percentile point of the distribution is 0.84standard deviations above the mean of the distribution (80 % ofthe distribution is below 0.84 standard deviations above themean).(b) The number 3.04 is approximately the 99.9 percentileof the distrib
24、ution.7.3 Table 1 gives examples of 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 w
25、ith R = 1.5, and if it is knownthat 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 41.5= 8 times the specificationlevel. If it were determined that with confidence, C, 80 % of theparts would
26、survive the overtest level, then since the tableshows that at the specification level, with confidence, C,anestimated 99 % of the parts would survive. Alternatively, giventhe data at the specification level, the desired part survivabilityand a factor that bounds the variability of the parts, this ta
27、blecan be used to determine an overtest level.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 higherlevel of overtest than the one indicated i
28、n the table. In general,very high probabilities of survival should not be taken literallybecause errors in the assumed probability distribution, sur-prises, maverick parts, simulation fidelity, and human error, allaffect a practical situation. An experienced user would havesome idea of the maximum c
29、redible survivability for theparticular application. It is suggested here that probabilities ofover 0.999999 are not credible unless massive experienceshows that tests, part processing, and the personnel are reliableto at least that level of confidence. Nevertheless, if a very highlevel of survival
30、is predicted, the information suggests that anyweak point in a system is most likely somewhere else.8. Keywords8.1 confidence; rejection; overtest data; statistical analysis4Stanley, A. G., Martin, K. E., and Price, W. E., “Hardness Assurance for TotalDose RadiationFinal Report, No. 730-2, Jet Propu
31、lsion 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 NS-26, 1979, p. 133.TABLE 1 Sur
32、vival 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 0.967235 0.990400 0.997756 0.99993
33、9 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 1.000000F 1263 99 (2005)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of th
34、is standard 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 ye
35、ars 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 at a meeting of theresponsible technical commi
36、ttee, 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 19428-2959,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).F 1263 99 (2005)3
