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PCB failure rate distribution
medini_1053080245
Hello, Considering a Bill of material composed by components and one PCB, what is the right way to deal with PCB failure rate? I have assigned part type to every component in order to set the raw failure rate coming from external sources. But how can I split to every component a part of the PCB's failure rate (using %) as additional failure rate ? If not possible what is the method proposed by MEDINI to deal with component and PCB failure rates? Thx
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medini_1050701002
Assuming you're talking about predictive reliability: If you're using FIDES you have to model the PCB as an extra component in Medini (this is what we do where I work). If you're using another method (MIL-HDBK-217F, Telcordia...) the PCB failure rate is often already modeled in the components failure rates.
medini_1023909254
Thanks Gerard, and in addition: also for IEC62380 you would add an entry for the <?WORD FLAGGED?> board as stated in the standard: Please note - for FMEDA this is often omitted as the failure modes of the individual components are the ones which you already check for the detailed effects of Open/Short and associated safety mechanisms . It is not so easy for the board failure modes: Yo may again have the two failure modes Open and Short but it is hard to associate direct effects and safety mechanisms with them. A typical justification to omit this is to refer to the DFMEA/PFMEA where sufficient measures are indicated that prevent board failures at all (and the failure rate of the board may be neglectable due to the copper wiing being not so much exposed to aging). However, if you prefer also to include the <?WORD FLAGGED?> board, the formula given in IEC62380 can be applied: Best regards, Eckhardt
medini_1053080245
Hello, Thank you both for your answers. I have already calculated PCB failure rate through FIDES (but externally). Meanwhile to have time to re-compute all the components (and PCB) through medini I use it as "user defined". So I understand that you have no specific recommendations to split it on every component (as I can see sometimes) but to use it as an additional component and/or follow-up PCB design through DFMEA.
medini_1053080245
Hello, IEC62380 normally propose a PCB failure rate calculation in part 6. As far I can see, the part 6 is not available in MEDINI for the IEC62380. Do you confirm it is not possible within MEDINI? What are our options: Calculate it outside and bring the value into MEDINI? ... Thx
medini_1023909254
Hello Romain, As IEC62380 is withdrawn by IEC some time ago, we will not put much effort in extending it -and as mentioned above, usually most customers do consider the board in (qualitative) D-FMEA but not in FMEDA/DC Concerning the point: Calculate it outside and bring the value into MEDINI? Actually I would highly recommend to use the medini scaling expression (of a type/element with prediction mode Userdefined) for the formula and not to calculate it outside. If it is done in medini, the calculation would always be able to take into account the mission profile - which significantly would impact the calculation (all the pi_n and delta_Ti are coming from the mission profile). When calculating outside you would always have to make sure that you use the same mission profile data inside and outside of medini. If you define this as a type, track-width, number of holes, Board Surface ... could all be defined as variables for the type and should be set to derive to enable adjustment for each individual instance of that type. Best regards, Eckhardt
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