MTBF PREDICTION REPORT

Transcription

1 MTBF PREDICTION REPORT PRODUCT NAME: BLE112-A-V2 Issued date: Rev:1.0 Bluegga Technologes. All rghts reserved. 1

2 MTBF PREDICTION REPORT... 1 PRODUCT NAME: BLE112-A-V Introducton and summary Method of analyss MTBF and Falure Rate Defned Envronmental factors and assumptons Results Sources... 5 Copyrght@2015 Bluegga Technologes. All rghts reserved. 2

3 1.0 Introducton and summary Relablty s defned as the probablty that a devce wll perform ts requred functon under stated condtons for a specfc perod of tme. Predctng wth some degree of confdence s very dependent on correctly defnng a number of parameters. The followng report follows the MIL-217F Techncal Reference Relablty Predcton Procedure for Electroncs Equpment, paragraph 2.4 of Task 100 of MIL-STD-756B; and the Parts Count Analyss method of MIL-HDBK-217F(N1/2), Appendx A. Smulated envronment: Ground Bengn(GB), 30 Celsus degrees. Predcton results: Model: BLE112-A-V2 Falure Rate: Fts MTBF: Hours 2.0 Method of analyss Falure rates for ndvdual parts n the product have been establshed based upon hstorcal data. Generally, falure rates are expressed n terms of the numbers of falure n 1,000,000,000(1 x 10^9) hours of operaton. The prmary sources of ths falure rate data s Mltary Hand Book, Relablty Predcton of Electronc Equpment; MIL-HDBK-217F and Bellcore Techncal Reference, Relablty Predcton Procedure for Electronc Equpment ; TR-332(Issue 6, December 1997) along wth relablty data gven by the component manufacturers. Varous factors such as temperature, humdty, vbraton shock, power levels, voltage stress, cycle rates, constructon characterstcs, etc., all affect the predcted falure rate for a part or devce. Wthn ths reference, all the factors are taken nto account accordng wth the models that MIL- 217F provdes. The method that was used to determne the falure rate s based solely on the Parts Count procedure. The baselne falure rates for Method I calculatons are derved from telecommuncatons and other ndustry feld data. The results of the MTBF analyss were then sorted n descendng order, to determne whch components account for the majorty of the falures. The detaled results are shown n Table 1. The relablty model descrbed only consders unt falures caused by devce hardware falures; falures due to programmng errors on software are not consdered. 3.0 MTBF and Falure Rate Defned The Mean Tme between Falure (MTBF) s a measure of the average tme nterval between successve random falures of a product (or devce). Ths assumes that the product(or devce) s operatng n the Mature Relablty perod of ts operatng lfe. Hgh falure rates normally assocated wth the Infant Mortalty perod are assumed to have been elmnated by testng. Durng the Mature Relablty perod, falures are generally of a random nature and on the Copyrght@2015 Bluegga Technologes. All rghts reserved. 3

4 average, relatvely constant n rate. Such falures are the result of nherent lmtatons n the desgn as well as accdents caused by usage. A correct understandng of MTBF s mportant. For example: A devce wth an MTBF of 40,000 hours does not mean that the devce should last for an average of 40,000 hours. Accordng to the theory behnd the statstcs of confdence ntervals, the statstcal average becomes the true average as the number of samples ncrease. Sometmes falure rates are measured n percent faled per bllon hours of operaton nstead of MTBF. The FIT s equvalent to one falure per bllon devce hours, whch s equvalent to a MTBF of 1,000,000,000 hours. The formula for calculatng the MTBF s θ T / Where θ MTBF, T tme and F number of falures durng that tme. Once MTBF has been calculated, what s the probablty that any one partcular BLE112-A-V2 wll be operatonal at tme equal to the MTBF? The dstrbuton of tme between falures statstcally defnes the probablty of falure free operaton over a specfed perod of tme. Therefore the followng equaton can calculate the probablty: R ( t) e F t / MTBF Where R (t) s the probablty of falure free operaton for a tme perod equal to or greater than tme t. The mathematcal Model used for determnng the BLE112-A-V2 relablty s known as the seres model. Ths model s based on the equaton: r( t) e λt Where r (t) s the relablty of BLE112-A-V2, t Elapsed operaton tme n hours and λ BLE112-A-V2 falure rate n parts per bllon hours. The assumpton s that f any part fals durng operaton, BLE112-A-V2 s consdered to have faled as a whole, and mantenance s requred. The relablty of the BLE112-A-V2, r (t) s also the combned probablty of the ndvdual parts relablty, where the unt contans quantty n parts: Where r ( t) relablty of part, over tme t, n r ( t) r( t) 1 e λt. The parts count relablty predcton method reflects the generc part types, quanttes and qualtes used, and consder the operatonal envronment mpact. These factors are combned n the followng mathematcal model: Copyrght@2015 Bluegga Technologes. All rghts reserved. 4

5 λ n ( λ π ) A N G Q 1 Where λ A Total falure rate of (parts per bllon hours) of BLE112-A-V2, λ G generc falure rate for a gven envronment for :th generc part of assembly, π Q qualty factor for the :th generc part of assembly, N quantty of the th generc part of assembly and n number of dfferent generc part categores. The falure rate model modfers, quantty, qualty factor and generc falure rate are lsted under ther respectve columns n the appendx tables. 4.0 Envronmental factors and assumptons Every parts generc falure rate ncludes the effects of envronment factors. The approprate envronment factor for the BLE112-A-V2 s Ground Bengn (GB). For GB the semconductor juncton temperature, TJ, s 50 degrees Celsus, and the other parts ambent temperature, TA, s 30 degrees Celsus. No temperature rse above ambent s assumed for any part. For most of the crtcal ICs relablty data was obtaned from the devce manufacturer. However, dfferent manufacturers specfy relablty data dfferently. Most test ther parts for a short perod of tme and then apply mathematcal formulas to dscern FITs or MTBF number. The mathematcal assumptons (Confdence level, temperature, EA energy, etc.) dffer across manufacturers. Operaton duty s assumed to be 100%. 5.0 Results Falure Rate n Parts Per Mllon Hours Assembly/Parts Lst Quantty Total Quantty x Total BLE112-A-V2/Bluegga Technologes Inc Sources -Mltary Hand Book, Relablty Predcton of Electronc Equpment; MIL-HDBK-217F -Practcal Relablty of Electronc Equpment, Products - E. Hnatek (Marcel Dekker, 2003) WW -Manufacturer provded relablty data - Bellcore Techncal Reference, Relablty Predcton Procedure for Electronc Equpment ; TR- 332(Issue 6, December 1997) Copyrght@2015 Bluegga Technologes. All rghts reserved. 5