Reliability

If 10,000 parts with a failure rate of 100 FIT are used for one year (about 8,760 hours), which is closest to the expected number of failures? (1 FIT = 1 failure per 10⁹ hours)

  1. AAbout 900
  2. BAbout 9
  3. CAbout 0.009
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Answer: B. About 9

100 FIT means 100 failures per 10⁹ hours, or 10⁻⁷ failures per hour. 10,000 parts × 8,760 hours = 8.76 × 10⁷ part-hours, so the expected number of failures is 8.76 × 10⁷ × 10⁻⁷ ≈ 8.8, about 9.

  • A. About 900 is 100 times too large.
  • B. Correct. 8.76 × 10⁷ × 10⁻⁷ ≈ 9.
  • C. About 0.009 results from an order-of-magnitude error.
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More Reliability questions

  1. On printed circuit boards and similar, what is the phenomenon called in which, under humid conditions, metal (such as silver or copper) dissolves as ions between biased electrodes, migrates and deposits in tree-like forms, causing a short?
  2. In high-k/metal gate nMOS transistors, what is the degradation called in which the threshold voltage shifts when positive gate voltage and high temperature are applied continuously?
  3. In leading-edge LSI design, what is the practice called of anticipating transistor degradation from BTI and HCI over the usage period and checking that timing is met even with degraded characteristics?
  4. When estimating field lifetime from temperature-humidity test results, which model is commonly used to express the effect of humidity as a power of relative humidity?
  5. For gate insulator breakdown lifetime, why must the difference between the area of test devices and the total gate area on an actual chip be considered?