Burn in is that process by which components of a system are exercised prior to being placed in service (and often, prior to the system being completely assembled from those components).

The intention is to detect those particular components that would fail as a result of infant mortality, that is, during the initial, high-failure rate portion of the bathtub curve of component reliability. If the burn in period is made sufficiently long (and, perhaps, artificially stressful), the system can then be trusted to be mostly free of further early failures once the burn in process is complete. For early system failures, see failure rate. ... Exponential failure density functions A failure rate is the average frequency with which something fails. ... Reliability concerns quality or consistency. ...

A precondition for a successful burn in is a bathtub-like failure rate, i.e. there are noticeable early failures with a decreasing failure rate following that period. By stressing all devices for a certain burn in time the devices with the highest failure rate fail first and can be taken out of the cohort. The devices that survive the stress have a later position in the bathtube with a lower failure rate.

Thus by applying a burn in, an increased (early) failure rate can be reduced with the trade-off of an also reduced yield.

When the equivalent life time of the stress is extended into the increasing part bathtube-like faiure rate, the positive effect of the burn in is inverted. In a mature production it is not easy to determine whether there is a decreasing failure rate. To determine the failure time distribution for a very low percentage of the production, one would have to destroy a very large number of devices.

When possible, it is better to eliminate the root cause of early failures than doing a burn in. Because of this, a process that initially uses burn in may eventually phase it out as the various root causes for failures are identified and eliminated.

For electronic components, burn in is frequently conducted at elevated temperature and perhaps elevated voltage. This process may also be called heat soaking. The components may be under continuous test or simply tested at the end of the burn in period. Electronics is the study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... This article may be too technical for most readers to understand. ...

See also

• Failure rate
• Reliability theory
• Survival analysis

Exponential failure density functions A failure rate is the average frequency with which something fails. ... Reliability theory developed apart from the mainstream of probability and statistics, and was used originally as a tool to help nineteenth century maritime insurance and life insurance companies compute profitable rates to charge their customers. ... Survival analysis is a branch of statistics which deals with death in biological organisms and failure in mechanical systems. ...

External links

Burn in and reliability