2 Stages of Reliability and Useful Life Period

When considering ‘reliability’, three phases of lifetimes are considered:

• Early life – declining failure rate where failures are due to random defects.
• Useful life – the steady state period where failure rate is relatively constant.
• Wear-out – stage where end of life mechanisms start to occur and failure rate increases.

Figure 1 illustrates this as a “bathtub curve” profile where the edges of the curves reflect the shape of a bath.

The focus of electronics reliability is the useful life period and also referred to as steady-state period where it is expressed in Failure in Time (FIT): # of failures/10⁹ hours.

Many industrial systems require useful lifetimes of 10 years or less but recent examples of reliability profiles modeled by TI that go above that include:

• Telecommunication equipment: 15 years continuous operation
• Industrial controllers in factory electrical supply system: 15 years continuous operation
• Solar invertor: 15 years continuous operation
• Water meter: 15 years continuous operation
• Electronic Meter: 20 years continuous operation