, Wearout. A Comprehensive Review of Hard-Disk Drive Reliability. I i \I b 2 $!

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1 A Comprehensive Review of Hrd-Disk Drive Relibility Jimmy Yng 0 Quntum Corportion Milpits Feng-Bin Sun 0 Quntum Corportion Milpits Key Words: Hrd disk drive, Relibility ssessment, Relibility prediction, Design stress nlysis, Relibility growth nlysis, Relibility demonstrtion testing, Field performnce trcking. SUMMARY & CONCLUSIONS A shorter development cycle (i.e months on verge), shorter life cycle in the field (i.e. - 3 yers on verge); s well s higher relibility requirements (i.e. specified minimum MTTF of 400,000 hours), ll present new chllenges to the hrd-disk drive mnufcturer (Refs. 1- ). In order to meet nd exceed the ever- incresing customer expecttions, systemtic pproch needs to be tken beginning with the erly design stge, through preproduction, nd mss production, nd finlly through to field opertion. This pper presents Quntum's current effort in chieving this gol. 1. INTRODUCTION A hrd disk drive (HDD) is very complicted dynmic system tht consists of electricl, electronic nd mechnicl components. It my fil due to vrious components nd mechnisms, such s hed, medi, hed-medi interfce, firmwre, pckging, hndling dmge, etc. Vrious filuregoverning stresses including temperture, humidity, ltitude, vibrtion, contct-strt-stop (CSS) frequency, duty cycle (both for power-on nd functionl),cn ll ffect the hrd disk drive. Field HDD filure rte typiclly enters stedystte round 1 yer nd strts wer-out round 5-7 yers s shown in Fig To understnd, quntify, evlute nd improve the relibility performnce of HDD requires systemtic pproch from design to field opertion trcking. Quntum Corportion hs long been n industry leder of qulity nd relibility in the DPSG (Desktop PC Storge, *.r $!.r( A Erly- w 1-1 4, Werout -life period I perio I / \ I I i \I b 0 Cumultive operting time Grwp) mrket. This pper will present n extensive review bout Quntum's efforts in chieving high relibility nd customer stisfction, especilly its Relibility Assessment Progrm. The fllowing will be covered in this pper: (1) Erly Relibility Prediction (ERP) () Design for Relibility (DFR) (3) Design Stress Anlysis (DSA) nd Highly Accelerted Life Test (HALT) (4) Relibility Growth Anlysis (RGA) (5) Relibility Demonstrtion Testing (RDT) for field relibility projection prior to mss production. (6) IDEMA's (Interntionl Disk Drive Equipment nd Mterils Assocition) sttus in Relibility Stndrds. (7) Field Performnce Trcking nd Evlution. QUANTUM'S APPROACH ON QUALITY AND RELIABILITY PROGRAM PLANS The following digrm is pictoril depiction of the Quntum Relibility Progrm covering the entire supply chin from product definition through volume rmp nd from suppliers to customers. Relibility mngement t Quntum requires concentrted ctivities in ech of the steps indicted in this flow digrm. Ech product will hve its own relibility progrm tht covers, mong other items, Design For Relibility Checklist, Consolidted Test Strtegy, Relibility Growth nd Demopstrtion Testing nd Field Relibility Trcking. The relibility testing is complementry to Quntum's comptibility testing, which hs primry function of checking for interfce nd functionl comptibility with different customers' pltforms. Quntum Q/R Progrm Fig. 1. I Field filure rte pttern of HDD. Figure.1 Quntum Q/R Progrm Pln /99/$ IEEE 1999 PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium 403

2 3. EARLY RELIABILITY PREDICTION 3. I Objective of Relibility Prediction The objective of erly relibility prediction is to show the difference between the current design estimte nd the trget relibility (MTTF). Also the relibility prediction provides the quntittive bseline needed to ssess the progress in relibility during the design phse to fcilitte (1) fesibility evlution. () the chievement of MTTF trgets. (3) the trde-off nlysis for compring competing designs nd selecting the most vible design ltemtives. (4) identifiction of potentil relibility problems. (5) the evlution of the impct of design chnges. (6) providing relibility input to other Relibility / Mintinbility tsks. (7) estblishment of stndrds for fctory relibility tests nd field performnce. 3. Methods, Procedures nd Dt Sources of Relibility Prediction The following two methods re used in Quntum for HDD relibility prediction: (1) Prt count prediction method. () Prt stress prediction method. As used throughout most of the computer industry, the Bellcore prediction procedure is the min tool nd dt source for Quntum s HDD relibility predictions. However, we lso hve our own dtbse which covers hed, medi, specific ASIC, red chnnel integrted circuit, nd other components. The dt for these components re minly from our supplier s life testing, on-going relibility testing, internl qulifiction such s RDT, nd most importntly from the field trcking dt. Over the lst 3 yers, Quntum shipped nerly 7.5 million drives to the field. Figure 3.1 is grphicl illustrtion of the dtbse for Quntum s relibility predictions. 4. DESIGN FOR RELIABILITY (DFR) DFR is generlized methodology of efficiently chieving relible new product design. DFR ctivities re typiclly conducted erly in the design cycle (before nd during the Engineering builds), when designs re reltively flexible. Relibility Improvement Tem (RIT), ctivities re continution nd refinement of the DFR work undertken s the design moves into Pilot nd erly Mss Production builds. Vrious engineering representtives from severl cross fimctionl disciplines typiclly prticipte during both DFR nd RIT including representtive engineers from (1) Design Engineering; () Product Engineering; (3) Commodity Engineering; (4) Process Engineering; (5) Relibility Engineering. The expected contributions of ech member re s follows: 0 Design Engineering: Provides the design nd is the mjor contributing member of the DFR tem in the res of identifying high relibility risks nd lterntives in the drive s design. Also the member who estblishes the first DFR tem meeting. Product Engineering: Member of the DFR tem whose mjor contribution is to identify sources, root cuses, nd ctions of mjor relibility problems on current products. 0 Commodity Engineering: Member of the DFR tem whose mjor contribution is in the re of component prts to be used nd specified in mnner which is comptible with the suppliers bility to mnufcture the prts with minimum of inducedinfncy defects. Process Engineering: Member of the DFR tem whose mjor contribution is to identify those res of the product s design which re not comptible with mnufcturer s cpbility to mnufcture the design with minimum of inducedinfncy defects. Relibility Engineering: Member of the DFR tem whose mjor contribution is in the re of field relibility dt on existing products, itertive relibility prediction modeling nd RDT test results. This member compiles the preliminry, ny interim, nd finl reports. Typiclly, the emphsis on tsks s well s the responsibility nd ownership of the tsks, will shift s the design mtures. The erly-build phse is very criticl period in the DFR methodology. Once functionlity hs begun to be estblished on the new design, ny significnt chnges which my impct the new design s relibility will become very difficult to implement within the typiclly very tight time restrictions of the new product design nd strt-up progrm. Hence if criticl DFR work cn not be ccomplished t this erly stge, it my not be prcticl to integrte the concepts lter. A WlTS - World ridr TrsoWns Sisirm FA fdlurr Annlpb CW - Cvslnnnrr Supplrt Csnvp Fig. 3.1 Dtbse for Quntum relibility prediction. The Preliminry DFR report should be delivered by the end of E builds, while the Interim DFR report submitted by the end of P builds. The Finl DFWRIT report should be redy t the completion of RDT PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium

3 ~ ~ 5. DSA AND HALT 5. I Purposes Design Stress Anlysis (DSA) is performed t subssembly nd component levels. Highly Accelerted Life Tests (HALT) re conducted t system or HDD levels. The purposes for conducting DSA nd HALT re to chieve: (1) Verifiction of design cpbility & mrgin of components () Erly identifiction of design, component, & process defects (3) Evlution of initil supplier prts for fitness for use & robustness (4) Provision of n erly indiction of suppliers process cpbility (5) Provision of informtion for DFR & relibility predictions (6) Continuous process improvement nd lessons lerned 5. Typicl Stress Prmeters The following stresses will be pplied to the Drives during DSA nd HALT tests. These re the most effective stresses nd hve the potentil to expose wide rnge of filure modes nd mechnisms inherent in the product: (1) Voltge extremes () Temperture extremes (3) Temperture chnge rtes (4) Vibrtion extremes (5) Mechnicl opertion extremes (6) Any combintion of one or more of the bove stresses 5.3 DSA & HALTStress Testing Processes DSA nd HALT tests will consist of the following tests nd process steps undertken either t the component or sub-ssembly level or t fully functionl drive level: (1) Therml Chrcteriztion of IC Components nd the Drive Assembly () Pckging (such s solder joints) Process Evlution (3) Vibrtion Stress (4) Combined Therml nd Electricl Stresses (5) Temperture nd Humidity Stress 5.4 DSA & HALTStress Profiles The profile prmeters my vry depending upon the product s chrcteristic response to ech type of stress, nd to the mgnitude of stress levels, product mteril nd functionl specifictions. The highest filure modes nd mechnisms will be obtined from the product bseline tests, nd bill of mteril nlysis nd yield informtion. The design, mteril, technology, nd yield informtion obtined will guide you in optimizing profiles to chieve the highest probbility of filure under the ppliction of given stress type nd mgnitude. Figure 5.1 illustrtes n exmple of HALT stress profile. 6. RELIABILITY GROWTH ANALYSIS (RGA) 6. I Introduction The RGA is the monitoring of the relibility, MTTF, or filure rte dt of the system or equipment to estblish trends - increses in relibility, or MTTF, or the decrese of filure rtes with engineering, reserch, development, Test, Anlyze, nd Fix (TAAF) until it chieves the specified gol before its cceptnce test, or before delivery. The Relibility Growth Anlysis consists of discreet tests required nd described by the reference test plns, s pplicble. For the purpose of evluting nd reporting the relibility growth chieved, the tests re divided into three phses which re: (1) The Design Verifiction Test. (DVT) () The Design Mturity Test. (DMT) (3) Relibility Demonstrtion Test (RDT). 6. Growth Models Used Relibility growth ssessment methodologies must ccount for dynmic environment due to modifictions being incorported into the drive. For exmple, in the presence of relibility growth the dt from the erlier prt of the testing phse would not be representtive of the current configurtion. Becuse of this sitution, vrious growth models or methods re often employed for ssessing drive relibility during the development test phse. Dune nd Crow/AMSAA Models (Refs. 3-4) re the most populr methods pplied in Quntum: Figure 5.1 A smple HALT stress profile PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium 405

4 (1) Dune MTTF Growth Model m (T >=m (T l c l m (T ) = cumultive MTBF t T, c T m (T)=c N (T 1' f T = totl ccumulted units hours of test nd / or development time, N (T,) = totl number of filures in time T, f m = cumultive MTBF t T = 1, 1 = growth fctor, () Crow/AMSAA Growth Model,r h. (T ) = instntneous filure rte t T, i T = cumultive test nd / or development time, p = shpe prmeter of the Weibull distribution, o<p<1, = scle prmeter of the Weibull distribution, q > 0. Quntum, in joint co-opertion with the University of Arizon nd the ReliSoft Corportion, hs developed the Relibility Growth Softwre to utomte nd speed up the dt nlysis procedure. 6.3 Wht the Growth Models Are Used For The growth models re used minly for the following purposes in Quntum: (1) To determine the relibility growth rte in the field. It is ssumed tht the field MTTF nd the filure rte improvement follows the sme pttern s observed during DVT, DMT nd RDT. () To determine the expected number of filures. For exmple, bsed on Crow/AMSSA model, the expected number of filures in the field between tl nd t cn be estimted by t N (t,t )= jh(t)dt = q-' f 1 t 1 L -I 7. RELIABILITY DEMONSTRATION TESTING (RDT) 7. I Introduction The objective of conducting relibility demonstrtion test is to demonstrte tht specified MTTF gol under stted conditions hs been chieved within given confidence level. Quntum's MTTF demonstrtion pproch is to test certin number of drives under n ccelerted test condition for 0% to 30% of the trgetkpecified MTTF. (Note: This is the totl ccumulted test time of ll drives under test). Prior to the demonstrtion test, ll to-be-tested drives should go through n IDEMA Bseline test t 35 "C for 4 hours to precipitte ny process infncy. According to the Bellcore prt stress nlysis, disk drive is ssumed to ttin 1.5 to.5 times higher MTTF t 5 C thn t 50 C mbient temperture under continuous opertion. For exmple, demonstrted MTTF of 80,000 hours t 50 C is pproximtely equivlent to 160,000 hours MTTF t 5 C. 7. Test Pln nd Anlysis A three-phse RDT is used t Quntum: (I) Erly Relibility Test (ERT); () First-phse RDT; nd (3) Second-phse RDT. The IO duty cycle on RDT is higher thn IDEMA's requirement (-3 times), while the environment conditions re consistent to the typicl user environment in the field. A typicl smple size for MTTF demonstrtion test is 00-1,000 units, depending upon the product. Ech drive test will run for pproximtely 1,000 hours mximum. After the demonstrtion test is conducted, the dt cn be nlyzed using the Exponentil, the Weibull (if 3 or more filures re observed), or the Bthtub-curve (if 3 or more filures re observed). Life distribution pproches to evlute the relibility chrcteristics, such s MTTF, nnul filure percentge (AFR) etc. s well s test results from ERT nd first-phse RDT re used to conduct field AFR projections. The trget minimum MTTF to be demonstrted prior to mssproduction is 150,000 hours (point estimte). 7.3 Test Conditions Environmentl: 35 C +3"C; 50% RH ; Nominl voltge. Opertionl: All drives will be run with the ltest Pentium PCs using Quntum RDT test script. The drive will operte red, write, sequentil compre, spindle idle nd stndby functions t levels which hve been selected to simulte typicl desktop opertions. The power will be cycled once per dy. 8. IDEMA RELIABILITY STANDARDS IDEMA stnds for the Interntionl Disk Drive Equipment nd Mterils Assocition n orgniztion responsible for estblishing the relibility stndrds within the hrd disk drive industry including relibility metrics, test procedures, test criteri, etc. Currently there re two IDEMA relibility stndrds: (1) IDEMA HDD Relibility Specifiction, nd () Benchmrk Test Specifiction (Ref. 5-6). The following two tbles summrize the ltest informtion on these two stndrds PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium

5 Summry Informtion Of IDEMA HDD Relibility Specifiction Purpose: Provide common methods for chrcterizing (1) HDD relibility with time dependent filure rte; () HDD sensitivity to temperture nd ltitude. Ctegorize dt sources for relibility projection. Relibility Metric: filure rte in 1-3 month; 4-6 month; 7-1 month; 13-EODL*. Duty Cycle Assumption: 100% Environmentl & Functionl Stress Fctors (1) Temperture (required for both server nd desktop); () Altitude (required for server clss; optionl for desktop); (3) SDindle strt/stod filure rte dder. Dt Presenttion -Engineering Dt Sheet (1) Required Dt 0 Bse filure rte in ll 4 time intervls for t lest one vintge in the chrt or tbulr formt. 0 Lbel the filure rte for ech time intervl with DER* or FOR*. 0 Units for filure rte is %0/1,000 hr. 0 Temperture environmentl fctor chrt. 0 Altitude environmentl fctor chrt (for server clss products only). Spindle stdstop dder chrt. () Optionl Dt 0 Filure rte presented in br chrt. Filure rte for more thn one vintge. 0 Benchmrk Test results per IDEMA Stndrd. Dt Sources for DER* 0 Pper studies: MIL 17, Bellcore, etc. 0 Inference from previous product performnce 0 Bum-in nd run-in results 0 Pre-production ORT 0 Engineering prototypes nd development mterils 0 DVT/DMT 0 RDT 0 Process mturity tests 0 Line yields 0 Control chrt results 0 HALT/HASS 0 Out-of-Box qulity udits Dt Sources for FOR* Field dt 0 Benchmrk test results for generlly- vilble (GA) relese level hrdwre On-going relibility test (ORT) (sme revision level s product relesed for generl vilbility) Field Relibility Reporting 0 metric to be used: X-month rolling verge filure rte 0 unit for the metric: %/K-POH (% Der 1.OOO Dower- * ** on-hours) lgorithm: X-month rolling verge monthly filure rte = (sum of returns from ll X months)/[sum of (countble running drives -totl number of countble return drives) from ech month within X months] EODL = end of design life; DER = development estimted relibility; FOR = field observed relibility. Summry Informtion Of IDEMA HDD Benchmrk Test Specifiction (Server Clss Only for Now) Purpose: Provide sttisticl verifiction on the first 3- month relibility level Who Does the Test: 3rd prty or mnufcturer itself Test Durtion: 6 weeks to 3 months Test Conditions: Section 5 of Stndrd Environmentl Conditions (1) Temperture 35OC () Altitude L Se level (3) Power on hours: see test profile Dt Presenttion Totl drive test hours Totl number of incidents Totl number of filures. Cuses of filures Demonstrted filure rte in terms of 60% upper 1-sided confidence limit using the chi-squre distribution: Filure Rte(l-3month) = x,+, CL/~T~, T, = totl drive test hours, r = number of filures, CL = confidence level (one-sided), nd x,+,cl = CL percentile of Chi-Squred distribution with DOF=r+. Actul temperture t 1" from the drive Actul ir flow Method of Filure Counts (1) Filures in Phse I (Integrtion Fllouts**) do not count ginst filure rte clcultion. () Filures in Phse I1 (Relibility Test***) do count for filure rte clcultion. EODL = end of design life; DER = development estimted relibility; FOR = field observed relibility. ** Plese refer to the Stndrd for test durtion nd procedure. *** Plese refer to the Stndrd for test procedure PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium 407

6 9. PRODUCT FIELD PERFORMANCE TRACKING 9. I Introduction Feedbck informtion from system customers concerning their pltform qulifiction sttus hs lwys been given high priority for filure nlysis to identify root cuse of the filures. These feedbck dt, long with field returns for repir or upgrde dt ll provide vluble informtion to better understnd drive design, nd mnufcturing fults in field ppliction use. One quick mesure of field performnce nd field MTTF is bsed on customer field return numbers or the percentge, nd power-on hours (duty cycles), known s the Annulized Filure Rte (AFR). Quntum hs well-defined seriliztion nd trcking system in both it s Configurtion Center nd its Repir Center for ccurtely recording drive mnufcturing lots, dte codes nd other sub-ssembly lot codes. For exmple, Quntum s DPSG product hs shipped 7 million drives in the lst13 yers. By trcking ech customer s shipment quntity, totl returns for repir, nd repir detil dt ech month with FA detil results, the monthly percent return rte my be used for monitoring overll field performnce. 9. Purpose The purpose for relibility field trcking is s follows: 1. To ssess product performnce in user environment nd compre tht with prediction, relibility growth nlysis nd relibility demonstrtion results conducted erlier in the development cycle.. To ugment nd updte our relibility dtbse by nlyzing the dt for root cuse. 3. Feedbck to Engineering groups nd criticl suppliers on key component performnce. 4. To provide historicl dt reference for future predictions on similr or new technology prts. 9.3 Methodology nd Dt Source The Annulized Filure Rte (AFR), is bsed on the monthly totl number of field filure returned units divided by the totl cumultive instlled bse nd multiplied by 1 to nnulize the filure rte. The MTTF vlue cn then be estimted from verge nnul drive operting hours or ssumed Power On Hours (Duty Cycle ) divided by the AFR rte. The MTTF derived from the AFR model cn lso be used to compre ccumulted run time MTTF models for ccurcy. 3 - Month Rolling Averge AFR r =I 1 Sum of FR for Months (i - ). (i - I), nd i Sum of CI for Upto Months (i - 4), (i - 3), nd (i - ) FR = field returns nd CI = cumultive instllments. MTTF clculted from the Annul Filure Rte (AFR) (Quntum): power on hours (POH) divided by AFR Averge nnul Power On Hours (POH) MTBF = AFR 9.4 Assumptions (1) Quntum ssumes two months lg for both DPSG nd WSSG drives. This is bsed on empiricl dt which llows time for shipment between our configurtion center to mjor OEM customers, integrtion & testing in OEM customer s system boxes, nd shipment & opertion t the end user. () The Averge Power On Hours (POH) used for AFR model is bsed on the drive duty cycle. The drive duty cycle which is Averge Power On Hours per yer in system environment tht my be defined in three ctegories s follows: 0 100% Duty Cycle, POH 8,736 hours primrily in Worksttion or Network server. 0 71% Duty Cycle, POH 6,40 hours primrily in PC or in smll network environment 10. ACKNOWLEDGMENT We wish to express our pprecition to ll of our collegues who hve mde mny constructive suggestions t vrious stges of this reserch. Specil thnks go to Gry Neher, Mnger of RDT, for his inspiring inputs, to Shms Jwid, DSA Mnger, for his inputs, nd to Jill Kenrick for her editing comments. We would lso like to express our thnks to Seifi Zki, Director of Comptibility nd Relibility Engineering, nd to John Hrting, Vice President of DPSG Customer Engineering for their consistent support nd encourgement. The dt source for AFR is the following: (1) Monthly returns nd cumultive instllments informtion from customer service group (CSG) (Strting from April 1998, new Dt bse, KARMNRTNDB, will be used). () WITS nd FA informtion from repir. The dt nlysis nd report re conducted monthly. The 3-month rolling verge AFR is recommended by IDEMA s the field AFR mesurement: PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium

7 REFERENCES I Yng, J. nd Zunznyik, K., Field Relibility Projection During New Product Introduction (NPI) Process, Proceedings of the Institute of Environmentl Sciences, pp , Zunznyik, K. nd Yng, J., Simultneous Development & Qulifiction in the Fst-Chnging 3.5 Hrd-Disk-Drive Technology, Proceedings of the Annul Relibility nd Mintinbility Symposium, pp. 7-3, Kececioglu, D., Relibility Engineering Hndbook, Vol. I, Prentice Hll, Upper Sddle River, New Jersey, 688 pp., Quntum Relibility Assessment Progrm, IDEMA, Specijktion of Hrd Disk Drive Relibility, 1998 IDEMA, Hrd Disk Drive Relibility Benchmrk Test Specifiction, BIOGRAPHIES Jimmy Yng Component & Product Relibility Engineering Quntum Corportion 500 McCrthy Blvd. Building # 1 P.O. Box 111 Milpits, CA U.S.A. Emil: jimmv.vng@untum.com Mr. Jimmy Yng, both CRE nd CQE, is Senior Relibility Engineering Mnger in the Component & Product Relibility Engineering Deprtment of Quntum s DPSG Customer Engineering Group. He hs over 18 yers of Qulity nd Relibility experience in the computer industry. He holds BSME degree from Feng-Chi University, Tiwn, R.O.C., nd n MS degree in Mnufcturing Engineering from Pittsburgh Stte University nd n MS Cndidte in Mnufcturing System Engineering from Ntionl Technology University. He hs written mny Q&R technicl ppers in IEEE, ASQC, NEPCON, ISSAT, RAMS. He is senior member of ASQC, SME, IES nd member of IEEE orgniztions. Feng-Bin Sun, Ph.D. Component & Product Relibility Engineering Quntum Corportion 500 McCrthy Blvd. Building # 1 P.O. Box Milpits, CA U.S.A. Emil: frnk.sun~guntum.com Dr. Feng-Bin Sun received his B.S.M.E. specilizing in Electro-mechnicl Structurl Design from the Southest University, Nnjing, Chin, in He erned his M.S.M.E. specilizing in Relibility Engineering from Shnghi University of Technology, Shnghi, Chin, in He received his Ph.D. in Relibility Engineering from The University of Arizon in He is currently Senior Relibility Engineer in the Corporte Relibility Engineering Deprtment of Quntum Corportion, Milpits, Cliforni. He hs uthored nd co-uthored three books nd numerous scientific ppers in Relibility Engineering. His min interests include Bum-in, ESS, relibility modeling nd life dt nlysis, optimum mintennceheplcement decision mking, mechnicl relibility, qulity loss functions, etc. He is member of IEEE, IEST, ASME, ASQC, nd SRE orgniztions PROCEEDINGS Annul RELIABILITY nd MAINTAINABILITY Symposium 409