ISO INTERNATIONAL STANDARD

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1 INTERNATIONAL STANDARD ISO Second ediion Imaging maerials Recordable compac disc sysems Mehod for esimaing he life expecancy based on he effecs of emperaure and relaive humidiy Maériaux pour image Sysèmes de CD enregisrables Méhode d'esimaion de l'espérance de vie basée sur les effes de la empéraure e de l'humidié relaive Reference number ISO 2008

2 Provläsningsexemplar / Preview PDF disclaimer This PDF file may conain embedded ypefaces. In accordance wih Adobe's licensing policy, his file may be prined or viewed bu shall no be edied unless he ypefaces which are embedded are licensed o and insalled on he compuer performing he ediing. In downloading his file, paries accep herein he responsibiliy of no infringing Adobe's licensing policy. The ISO Cenral Secrearia acceps no liabiliy in his area. Adobe is a rademark of Adobe Sysems Incorporaed. Deails of he sofware producs used o creae his PDF file can be found in he General Info relaive o he file; he PDF-creaion parameers were opimized for prining. Every care has been aken o ensure ha he file is suiable for use by ISO member bodies. In he unlikely even ha a problem relaing o i is found, please inform he Cenral Secrearia a he address given below. COPYRIGHT PROTECTED DOCUMENT ISO 2008 All righs reserved. Unless oherwise specified, no par of his publicaion may be reproduced or uilized in any form or by any means, elecronic or mechanical, including phoocopying and microfilm, wihou permission in wriing from eiher ISO a he address below or ISO's member body in he counry of he requeser. ISO copyrigh office Case posale 56 CH-1211 Geneva 20 Tel Fax copyrigh@iso.org Web Published in Swizerland ii ISO 2008 All righs reserved

3 Conens Page Foreword...iv 1 Scope Normaive references Terms and definiions Purpose and assumpions Purpose Assumpions Measuremens Summary Block error rae (BLER) Tes equipmen Tes specimen Acceleraed sress es plan General Sress condiions Acceleraed es cell sample populaion Time inervals Tes plan Measuremen condiions Daa evaluaion Lognormal disribuion model Eyring acceleraion model Acceleraion facors Survivor analysis Aids Disclaimer...13 Annex A (informaive) Sep analysis ouline...14 Annex B (informaive) Example of es plan and daa analysis...15 Bibliography...27 ISO 2008 All righs reserved iii

4 Provläsningsexemplar / Preview Foreword ISO (he Inernaional Organizaion for Sandardizaion) is a worldwide federaion of naional sandards bodies (ISO member bodies). The work of preparing Inernaional Sandards is normally carried ou hrough ISO echnical commiees. Each member body ineresed in a subjec for which a echnical commiee has been esablished has he righ o be represened on ha commiee. Inernaional organizaions, governmenal and non-governmenal, in liaison wih ISO, also ake par in he work. ISO collaboraes closely wih he Inernaional Elecroechnical Commission (IEC) on all maers of elecroechnical sandardizaion. Inernaional Sandards are drafed in accordance wih he rules given in he ISO/IEC Direcives, Par 2. The main ask of echnical commiees is o prepare Inernaional Sandards. Draf Inernaional Sandards adoped by he echnical commiees are circulaed o he member bodies for voing. Publicaion as an Inernaional Sandard requires approval by a leas 75 % of he member bodies casing a voe. Aenion is drawn o he possibiliy ha some of he elemens of his documen may be he subjec of paen righs. ISO shall no be held responsible for idenifying any or all such paen righs. ISO was prepared by Technical Commiee ISO/TC 42, Phoography. This second ediion cancels and replaces he firs ediion (ISO 18927:2002), of which i consiues a minor revision. The following changes have been made o he firs ediion: modificaion of definiion 3.10 (life expecancy); modificaion of 5.2 on block error rae; updaing of normaive and bibliographical references; removal of he original Annex A. iv ISO 2008 All righs reserved

5 INTERNATIONAL STANDARD Imaging maerials Recordable compac disc sysems Mehod for esimaing he life expecancy based on he effecs of emperaure and relaive humidiy 1 Scope This Inernaional Sandard specifies a es mehod for esimaing he life expecancy of informaion sored on recordable compac disc sysems. Only he effecs of emperaure and relaive humidiy on he media are considered. This Inernaional Sandard does no cover he effecs of ligh, air polluion, or ime-dependen flow phenomena. 2 Normaive references The following referenced documens are indispensable for he applicaion of his documen. For daed references, only he ediion cied applies. For undaed references, he laes ediion of he referenced documen (including any amendmens) applies. ISO/IEC ), Informaion echnology Daa inerchange on read-only 120 mm opical daa disks (CD-ROM) IEC 60908:1999, Audio recording Compac disc digial audio sysem Experimenal saisics, U.S. Naional Bureau of Sandards Handbook 91, Terms and definiions For he purposes of his documen, he following erms and definiions apply. 3.1 baseline condiion represening he disc a ime of manufacure NOTE This is cusomarily he iniial parameer measuremen aken prior o any applicaion of sress. The designaion is usually = 0 for a sress ime equal o zero hours. 3.2 block error rae BLER raio of erroneous blocks o oal blocks measured a he inpu of he firs (C1) decoder (before any error correcion is applied) 1) Equivalen o ECMA 130. ISO 2008 All righs reserved 1

6 Provläsningsexemplar / Preview NOTE The more commonly repored value for BLER is he number of erroneous blocks per second measured a he inpu of he C1-decoder during playback a he sandard (1X) daa rae. [IEC 60908:1999] maximum block error rae max BLER maximum BLER measured anywhere on a disc 3.3 compac disc-recordable CD-R recordable opical disc in which informaion can be recorded o cerain areas in compac disc forma NOTE 1 NOTE 2 Informaion can be recorded once and read many imes. The erm compac disc-wrie once (CD-WO) has also been used o describe his ype of disc. 3.4 cumulaive disribuion funcion F() probabiliy ha a random uni drawn from he populaion fails by ime, or he fracion of all unis in he populaion which fails by ime lognormal cumulaive disribuion funcion F() cumulaive disribuion funcion in which he logarihm of he relevan parameer, in his Inernaional Sandard he disc lifeime, has a normal disribuion and is defined by he following equaion: where 0 lx 1 ln( x) µ l 2 ( ) 2 σ l 1 1 F() = e dx 2π σ x σ l is he ime; is a variable represening disc lifeime; is he log sandard deviaion; µ l is he log mean; ln(x) is he naural logarihm of x µ NOTE When = e 1, he lognormal cumulaive disribuion funcion evaluaes o 0,5. In oher words, he model predics ha half he samples have failed a ha ime. 3.5 disc-a-once recording mehod of recording a CD-R disc whereby he enire CD is recorded in one pass wihou urning off he laser 3.6 end-of-life occurrence of any loss of informaion 2 ISO 2008 All righs reserved

7 3.7 exended-erm sorage condiions sorage condiions suiable for he preservaion of recorded informaion having permanen value 3.8 glass ransiion reversible change in an amorphous polymer from, or o, a viscous or rubber condiion o, or from, a hard and relaively brile one glass ransiion emperaure T g approximae mid-poin of he emperaure range over which glass ransiion akes place NOTE 1 T g can be deermined readily only by observing he emperaure a which a significan change akes place in a specific elecrical, mechanical, or oher physical propery. NOTE 2 T g can also be sensiive o he moisure conen of he polymer. 3.9 informaion signal or image recorded using he sysem 3.10 life expecancy LE lengh of ime ha informaion is prediced o be accepable in a sysem afer dark sorage a 23 C and 50 % relaive humidiy (RH) sandardized life expecancy SLE minimum life span, prediced wih 95 % confidence, of 95 % of he produc sored a a emperaure no exceeding 25 C and a relaive humidiy (RH) no exceeding 50 % RH 3.11 rerievabiliy abiliy o access informaion as recorded 3.12 sress experimenal variable o which he specimen is exposed for he duraion of he es inerval NOTE In his Inernaional Sandard, he sress variables are confined o emperaure and relaive humidiy survivor funcion R() probabiliy ha a random uni drawn from he populaion survives a leas ime, or he fracion of all unis in he populaion which survive a leas ime NOTE R() = 1 F() sysem combinaion of maerial, hardware, sofware and documenaion necessary for recording and/or rerieving informaion ISO 2008 All righs reserved 3

8 Provläsningsexemplar / Preview 3.15 es cell device ha conrols he sress o which he specimen is exposed 3.16 rack-a-once recording mehod of recording a CD-R disc whereby each rack is recorded individually wih 150 empy secors immediaely preceding i and wo run-ou secors immediaely following 3.17 uncorrecable error error in he playback daa ha is no correcable by he cross inerleave Reed-Solomon code defined in IEC as implemened in a sysem 4 Purpose and assumpions 4.1 Purpose The purpose of his Inernaional Sandard is o esablish a mehodology for esimaing he life expecancy of informaion sored on recordable compac disc sysems. This mehodology provides a echnically and saisically sound procedure for obaining and evaluaing acceleraed es daa. The mehodology deals only wih he effecs of emperaure and humidiy on he rerievabiliy of sored informaion. For his reason, his Inernaional Sandard is primarily direced o hose sorage applicaions, e.g. libraries and archives, in which exposure o oher influences poenially derimenal o informaion life expecancy, such as chemical agens, inense ligh sources and improper handling, is conrolled and minimized. 4.2 Assumpions The validiy of he procedure defined by his Inernaional Sandard relies on hree assumpions: specimen life disribuion is appropriaely modelled by he lognormal disribuion; he kineics of he dominan failure mechanism is appropriaely modelled by an Eyring acceleraion model; he dominan failure mechanism acing a he usage condiion is he same as ha a he acceleraed condiions. Publicaions by Hamada and Sinson provide daa indicaing ha hese assumpions are applicable o compac disc-recordable (CD-R) sysems (see references [5] and [6] in he Bibliography). 5 Measuremens 5.1 Summary A sampling of 80 recorded discs shall be divided ino five groups according o a specified plan. Each group of discs (es cell) shall be subjeced o one of five es sresses, combinaions of emperaure and relaive humidiy. Periodically during he sress condiions, all discs from each sress group shall have heir block error rae (BLER) measured. Daa colleced a each ime inerval for each individual disc are hen used o deermine a lifeime for ha disc. The disc lifeimes a each sress level are fied o a lognormal disribuion o deermine a mean lifeime for he sress. The resuling five mean lifeimes are regressed agains emperaure and relaive humidiy according o an Eyring acceleraion model. This model is hen used o esimae he disribuion of lifeimes a a usage condiion. 4 ISO 2008 All righs reserved

9 5.2 Block error rae (BLER) End-of-life is he occurrence of any loss of informaion. Ideally, each specimen is esed unil he firs loss of informaion occurs. Realisically, his is impracical. This Inernaional Sandard considers max BLER o be a high-level esimae of he performance of he sysem. The objecive of measuring BLER is o esablish a pracical esimaion of he sysem's abiliy o read recorded daa wihou uncorrecable errors. A change in max BLER in response o he ime a an acceleraed emperaure and humidiy is he principal qualiy parameer. IEC saes ha he BLER averaged over any 10 s shall be less han A he sandard (1X) daa rae, he oal number of blocks per second enering he C1-decoder is Thus, an equivalen limi on BLER is 220 blocks per second. A BLER of 220 is an arbirary level chosen as a predicor of he onse of uncorrecable errors and hereby end-of-life. A BLER of 220 corresponds o an upper limi for error correcion. As a resul, lower BLER discs are recommended o use for long-erm sorage. 5.3 Tes equipmen General requiremens A compac disc player ha conforms o ISO/IEC and sofware capable of producing a display of max BLER. If i becomes necessary o replace he es equipmen, he US Naional Bureau of Sandards Handbook 91 shall be followed for correlaing es equipmen oupus. The make, model and version of he es equipmen (including sofware) shall be repored wih he es resuls Calibraion and repeaabiliy Calibraion according o he eser manufacurer's procedure shall be performed prior o any measuremen daa being colleced. A calibraion disc shall be available from an accredied source. In addiion o he calibraion disc, one conrol disc shall be mainained a ambien condiions and is max BLER measured before and afer each daa collecion inerval. A conrol char shall be mainained for his conrol disc. The mean and sandard deviaion of he conrol disc shall be esablished by collecing a leas five measuremens. Should any individual max BLER reading differ from he mean by more han hree imes he sandard deviaion, he problem shall be correced and all daa colleced since he las valid conrol poin shall be remeasured. 5.4 Tes specimen General requiremens A es specimen is any disc ha, afer recording, mees ISO/IEC specificaions and conains represenaive daa exending o wihin 2 mm of he maximum recording diameer Specimen selecion All discs shall be nominally idenical wih regard o subsrae groove srucure, layer srucure, coaing composiion, recording capaciy, and age prior o es iniiaion. I is preferred ha he CD-R media be chosen from differen los and producion lines in order o be represenaive of normal process variaions. All discs shall be mainained in he manufacurer's ransporaion and sorage condiions prior o recording. ISO 2008 All righs reserved 5

10 Provläsningsexemplar / Preview The nominal disc capaciy shall be repored wih he es resuls Recording sysem Specimen discs may be recorded in any appropriae recording device. Since he exrapolaed lifeime is a funcion of he sysem including he CD-R media, all discs shall be recorded idenically o he exen possible. Similar recording devices shall be used, as well as similar sofware and recording condiions. Discs recorded on differen physical devices shall be disribued as equally as possible across he es cells. The make and model of he recording device, he linear velociy employed during recording and he sofware used in he recording sysem shall be repored wih he es resuls Ambien recording condiions Ambien condiions during recording shall be wihin he following limis: emperaure: 15 C o 35 C; relaive humidiy: 45 % o 75 %. During recording, he recording sysem shall be isolaed from exernal vibraions Recording mehod I is srongly recommended ha all discs be recorded using he "disc-a-once" mehod. If discs are recorded using he "rack-a-once" mehod, all errors occurring a he gap beween racks shall be ignored for he purpose of his Inernaional Sandard. Packe wriing (in which several wrie evens are allowed wihin a rack) shall no be employed. Independen of he wriing mehod, he specimen discs shall be recorded as a single session and finalized. 6 Acceleraed sress es plan 6.1 General Informaion properly recorded in a CD-R sysem of good manufacure should have a life of several years or even decades. Consequenly, i is necessary o conduc acceleraed ageing sudies in order o develop a life expecancy esimae. The key is conducing a es plan ha will provide he informaion necessary o saisfacorily evaluae he paricular sysem. Many acceleraed life es plans follow a raher radiional approach in specimen selecion, experimenaion and daa evaluaion. These radiional plans share he following characerisics: a) he oal number of specimens is evenly divided amongs all he acceleraed sresses; b) each sress is evaluaed a he same ime incremens; c) he Arrhenius relaionship is used as he acceleraion model; d) he leas squares mehod is used for all regressions; e) he calculaed life expecancy is for he mean or median life raher han for he firs few failure perceniles. On he oher hand, opimum es plans have been proposed which differ in significan aspecs from radiional plans. These plans have he following characerisics: wo and only wo acceleraion levels for each sress; 6 ISO 2008 All righs reserved

11 a large number of specimens disribued mosly in he lowes sress levels; he need o know he failure disribuion, a priori, in order o develop he plan. The maximum effeciveness of a plan can eiher be esimaed before he es sars or deermined afer he resuls have been obained. As each CD-R sysem will have differen characerisics, a specific, deailed opimum plan is impossible o forecas. This es plan borrows from he opimum plan, he radiional plan and previous experience wih he sysems, es equipmen and acceleraed es sresses o pu ogeher a compromise es plan. Modificaions of his plan will be required o design he bes plan for oher applicaions. The mehodology shall be applicable o all CD-R media assessmens. 6.2 Sress condiions Levels As menioned in 6.1, an opimum es plan uilizes only wo sress levels for each parameer evaluaed. This is because, in an ideal case, he relaionship beween changes in he parameer invesigaed and changes in sress are known. The compromise es plan, documened in his Inernaional Sandard, does no make such an assumpion; herefore, hree differen sress levels per parameer shall be used so ha he lineariy of he parameer funcion versus he sress level may be demonsraed. The es plan shall have he majoriy of es specimens placed a he lowes sress condiion. This minimizes he esimaion error a his condiion and resuls in he bes esimae of he degradaion rae a a level close o he usage condiion. The greaer number of specimens a he lower sress condiion also ends o equalize he number of failures observed by es compleion Condiions For implemening he es plan documened in his Inernaional Sandard, five sress condiions shall be used. The minimum disribuion of specimens among he sress condiions ha shall be used is shown in Table 1. Addiional specimens and condiions may be used if desired for improved precision. Table 1 Summary of sress condiions Tes cell number Tes sress T(inc) a RH(inc) a C % Number of specimens Incubaion duraion Minimum oal ime Inermediae RH RH(in) b h h % h Minimum equilibrium duraion a T(inc) and RH(inc) are he sress incubaion emperaure and relaive humidiy. b RH(in) is he inermediae relaive humidiy ha a T(inc) suppors he same equilibrium moisure absorpion in polycarbonae as ha suppored a room ambien emperaure and relaive humidiy. ISO 2008 All righs reserved 7