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.

Figure 1. Bathtub Curve Showing Different Stages of Reliability

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