Burn in
Encyclopedia
Burn-in is the 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 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.
A precondition for a successful burn-in is a bathtub-like failure rate, that is, 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 bathtub curve (with an appropriately lower ongoing failure rate).
Thus by applying a burn-in, early in-use system failures can be avoided at the expense (tradeoff) of a reduced yield caused by the burn-in process.
When the equivalent lifetime of the stress is extended into the increasing part of the bathtub-like failure-rate curve, the effect of the burn-in is a reduction of product lifetime. 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 component
s, 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.
There is another use of the term by some audiophile
s, who leave new audio equipment turned on for multiple days or weeks, to get the components to achieve optimal performance. However, many debates have arisen about the benefits of this practice.
The intention is to detect those particular components that would fail as a result of the initial, high-failure rate portion of the bathtub curve
Bathtub curve
The bathtub curve is widely used in reliability engineering. It describes a particular form of the hazard function which comprises three parts:*The first part is a decreasing failure rate, known as early failures....
of component reliability
Reliability engineering
Reliability engineering is an engineering field, that deals with the study, evaluation, and life-cycle management of reliability: the ability of a system or component to perform its required functions under stated conditions for a specified period of time. It is often measured as a probability of...
. 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.
A precondition for a successful burn-in is a bathtub-like failure rate, that is, 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 bathtub curve (with an appropriately lower ongoing failure rate).
Thus by applying a burn-in, early in-use system failures can be avoided at the expense (tradeoff) of a reduced yield caused by the burn-in process.
When the equivalent lifetime of the stress is extended into the increasing part of the bathtub-like failure-rate curve, the effect of the burn-in is a reduction of product lifetime. 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 component
Electronic component
An electronic component is a basic electronic element and may be available in a discrete form having two or more electrical terminals . These are intended to be connected together, usually by soldering to a printed circuit board, in order to create an electronic circuit with a particular function...
s, burn-in is frequently conducted at elevated temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and perhaps elevated voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
. 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.
There is another use of the term by some audiophile
Audiophile
An audiophile is a person who enjoys listening to recorded music, usually in a home. Some audiophiles are more interested in collecting and listening to music, while others are more interested in collecting and listening to audio components, whose "sound quality" they consider as important as the...
s, who leave new audio equipment turned on for multiple days or weeks, to get the components to achieve optimal performance. However, many debates have arisen about the benefits of this practice.
See also
- Burn-in ovenBurn-in ovensBurn-in ovens are designed for dynamic and static burn-in of integrated circuits and other electronic devices. Typical sizes are from under ten to over , with air or nitrogen configurations...
- Failure rateFailure rateFailure rate is the frequency with which an engineered system or component fails, expressed for example in failures per hour. It is often denoted by the Greek letter λ and is important in reliability engineering....
- Reliability theoryReliability theoryReliability theory describes the probability of a system completing its expected function during an interval of time. It is the basis of reliability engineering, which is an area of study focused on optimizing the reliability, or probability of successful functioning, of systems, such as airplanes,...
- Survival analysisSurvival analysisSurvival analysis is a branch of statistics which deals with death in biological organisms and failure in mechanical systems. This topic is called reliability theory or reliability analysis in engineering, and duration analysis or duration modeling in economics or sociology...