原則上，ISO 26262-11:2018 認為 EOS 為系統性失效模式，因此不納入 PMHF 之計算式中。
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溫度影響因子 (influencing factor) 或溫度加速因子，π[sub]T[/sub]
T[sub]ref[/sub] = 55 °C = 328 K
T[sub]str[/sub] = 125 °C = 398 K
π[sub]T[/sub] = 78.6
作者: hlperng 時間: 2019-8-25 13:31:31
本帖最後由 hlperng 於 2019-8-25 13:49 編輯
ISO 26262-5 第 8.4.3 節規定，安全性目標訂定車輛安全完整性等級 (ASIL) 為 B、C、D 三個等級的電子產品必須決定硬體零件的失效率推定值。這是車用電子產品必須執行可靠度預估作業的主要依據章節。
8.4.3 This requirement applies to ASIL (B), C, and D of the safety goal. The estimated failure rates for hardware parts used in the analyses shall be determined:
a) using hardware part failure rate data from a recognized industry souorce, or
b) using statistics based on field returns. In this case, the estimated failure rate should have a comparable confidence level at least 70 %, or
c) using expert judgement founded on an engineering approach based on quantitative and qualitative arguments. Expert dudgement shall be exercised in accordance with structured criteria as a basis for this judgement. These criteria shall be set before the estimation of failure rates is made.
EXAMPLE 1. Commonly recognized industry sources to determine the hardware part failure rates and the failure mode distributions include SN 29500, IEC 61709, MIL-HDBK-217F Notice 2, RIAC-HDBK-217 Plus, UTE C80-811, NPRD-2016, EN 50129:2003, Annex C, RIAC-FMD:2016, MIL-HDBK-338, and FIDES 2009 Ed. A. The failure mode distributions e.g. those defined by "Alessandro Birolini - Reliability Engineering" can be used.
NOTE 1. The failure rate values given in these databases are generally considered to be conservative.
NOTE 2. In applying a selected industry source the following considerations are appropriate to avoid artificial reduction of the calculated base failure rate:
- the mission profile;
- tha applicability of the failure modes with respect to the operating conditions; and
- the failure rate unit (per operating hour or per canlendar hour).
NOTE 3. If the confidence level for the failure rate of different hardware parts used in the SPFM and LFM evaluation is significantly different, the metrics will be biased.
NOTE 4. It may still be necessary to scale these statistics-based data from field retruns before using them together with values from other data sources with different confidence levels. See also NOTE 2.
NOTE 5. Failure rates based on field returns can be calculated as described in ISO 26262-8:2018, Clause 14 (Proven in use).
NOTE 6. The criteria for expert judgement can include a combination of heuristic information supported by a combination of field data, testing, reliability analysis and physics-of-failure based simulation approaches while considering the novelty of the design.
NOTE 7. Informative references from international reliablity expert bodies can be used: SAE J1211 "Robustness Validation" - Analysis, Modeling and Simulation provides physical-of-failure (PoF) based failure mechanism models, JEDEC-JESD 89, JEDEC JESD 91, JEDEC JESD 94, JEDEC JEP 143, JEDE JESD 148.
NOTE 8. If failure rates from multiple data sources (as listed in 8.4.3) are combined e.g. in the case the failure rate of different parts are not available from the same source, the failure rate can be scaled using a scaling factor such that the quality of prediction of the different failure rates is equivalent. This scaling can be used if a rationale for the scaling factor between two failure rate sources is available.
EXAMPLE 2. An element failure rate is found only in one source whereas a similar element is available in that and another source. The scaling factor is the ratio of the failure rate from these two sources utilising the same mission profile.
EXAMPLE 3. Failure rates from data handbooks are generally considered to be conservative. If a random hardware failure target value consistent with the use of handbook data is chosen, failure rate derived from field returns can be used by applying an appropriate scaling factor (corresponding to a confidence level more conservative than usual, for example).
NOTE 9. If a suitable scaling factor is not available, separate target values compliant with the SPfM and LFM requirements can be assigned to the different elements under consideration (analogues to 8.4.4).
NOTE 10. For semiconductors, see ISO 26262-11:2018, 4.6 for guidance.