14 March 2016
manufacturers accomplish an accelerated component
burn-in by placing the components into an oven and
operating the parts.
I once visited a plant manufacturing computer control
systems, and they put ICs in operating/measuring circuits
into a heated oven and operated them for a period of time
with the failed parts being rejected.
Check out Paul Verhage’s Near Space columns in
Nuts & Volts to see some of the methods of burn-in testing
which are available to and doable by hobbyists without
breaking the piggy banks. Due to the loss of the least
reliable components, the components that pass the burn-in
are much more expensive.
The longest portion of the failure rate curve is
the “useful life,” which is the time during which the
component operates as designed in the device into which
it is inserted. The useful life is a statistical value determined
by measuring hundreds of components until they fail.
The useful life is also called the service life, which is often
expressed as mean time before failure (MTBF).
In the real world, reliability was well described by the
Yankees great, Yogi Berra: “It ain’t over ‘til it’s over.” Or,
in electronics terms, no matter how reliable thousands of
components have been, the one you have could fail at any
The “wear out” period of the failure rate curve
for most electronic devices is flat, and the curve ends
when the component does. Mechanical devices and
components with heated filaments (vacuum tubes and
incandescent lamps) will experience the wear out shown in
Reliability of electronic devices is related to the “stress”
placed on the component. If we use a 1/2 watt resistor in a
circuit in which the resistor only has to dissipate 0.1 watts,
the resistor will last much longer than the same resistor
used in a circuit in which it must dissipate 0.499 watts.
Even this approach has its drawbacks, such as the size of
In our example circuit, a 1/4 watt resistor may fit, but
the 1/2 watt one may be too large. Using capacitors rated
at higher working voltages can increase their reliability, and
operating transistors at lower temperatures will increase
their reliability. Protecting a circuit from overvoltage or
overcurrent will usually increase its life time. However,
n FIGURE 7. Applications Of Reliability Technology
System Reliability vs. Parts And Part Reliability
n FIGURE 6.