Traditional electronics reliability engineering began during the period of infancy in solid state electronic hardware. The first comprehensive guide to Failure Prediction Methodology (FPM) premiered in 1956 with the publication of the RCA release TR-1100: "Reliability Stress Analysis for Electronic Equipment" presented models for computing rates of component failures. "RADC Reliability Notebook" emerged later in 1959, followed by the publication of a military handbook know as that addressed reliability prediction known as Military Handbook for Reliability Prediction of Electronics Equipment (MIL HNBK 217) . All of these publications and subsequent revisions developed the FPM based on component failures in time for deriving a system MTBF as a reference metric for estimating and comparing the reliability of electronics systems designs. At the time these documents were published it was fairly evident that the reliability of an electronics system was dominated by the relatively short life entitlement of a key electronics component, vacuum tubes.
In the 21st century, active components have significant life entitlements if they had been correctly manufactured and applied in circuit. Failures of electronics in the first five or so years are almost always a result of assignable causes somewhere between the design phase and mass manufacturing process. It is easy to verify this from a review of root causes of verified failures of systems returned from the field . Almost always you will find the cause an overlooked design margin, an error in system assembly or component manufacture, or from accidental customer misuse or abuse. These causes are random in occurrence and therefore do not have a consistent failure mechanism. They are not in general capable of being modeled or predicted.
There is little or no evidence of electronics FPM correlating to actual electronics failure rates over the many decades it has been applied. Despite the lack of supporting correlating evidence, FPM and MTBF is still used and referenced for a large number of electronics systems companies. FPM has shown little benefit in producing a reliable product, since there has been no correlation to actual causes of field failure mechanisms or rates of failure. It actually may result in higher product costs as it may lead to invalid solutions based on invalid assumptions (Arrhenius anyone?) regarding the cause of electronics field failures.
It’s time for a new frame of reference, a new paradigm, for measurement for confirming and comparing the capability of electronics systems to meet their reliability requirements. The new orientation should be based on the stress-strength interference perspective, the physics of failures, and material science of electronics hardware.
The new metric and relationship to reliability is illustrated in a stress-strength graph as shown in figure 1. This graphic shows the relationship between a systems strength and the stress or load it is subjected to. As long as the load is less than the strength, no failures occur.