RELIABILITY ANALYSIS ON THE PRODUCT
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RELIABILITY AND SAFETY
The techniques used by our experts allow to reduce the risk of releasing products not in compliance with the market expectations and standards.
The reliability has a crucial role in the client’s satisfaction and deep impacts on the safety of several products released on the market (automotive, medical, etc.)
GESTLABS supports the client by providing with a rigorous and scientific approach, which requires the ability to identify the stress tests and the lab analysis suitable to the identified specific failure mechanisms. Our personnel can support the client in all the phases of the product life cycle, from the design to the prototyping and the production qualifying with the identification and performance of the reliability tests.
Our technicians use the following methods to guarantee that the products released to the clients assure the most reliability.
MTBF Calculation and the failure rate
The MTBF (Mean Time Between Failures) calculation is one of the cornerstones of reliability and it has the aim to predict the failure of a device during it useful life, so that before the wear out. The MTBF and the failure rate, which is the contrary of MTBF, can be determined by the experimental tests or, in case of electronic sheets, by specific standards. The MTBF value is an essential requirement for the customer, and it is necessary in many fields like Automotive, Medical, Aerospace etc.
The Useful Life is the period when the device works optimally, and it is not affected by wear yet. This period goes usually beyond the warranty period, and it corresponds to the duration expectation by the client. It can be identified through accelerated stress conditions or, in the designing phase of electronic sheets, through specific calculations in compliance with specific standards.
Distributions for reliability
The statistical distributions (chi-squared, Weibull, exponential, etc.) are necessary to accurately perform the reliability predictions starting from the data obtained by the tests. Through these statistical distributions, it is possible to determine the MTTF (Mean Time To Failure) and the MTBF (Mean Time Between Failures) with confidence ranges based on the numerousness of the used sample.
Accelerated stress tests and acceleration factors
For the reliability predictions it is often necessary not to limit to theoretical calculations, but to perform specific stress tests whose aim is to accelerate specific failure mechanisms. The accelerated tests involve accelerating factors like temperature, humidity, power, voltage, etc. It is mandatory being able to link the most suitable accelerating factors and values to the different failure mechanisms to avoid the activation of abnormal failure mechanisms or to have insufficient acceleration factors. The acceleration factors can be determined by experimental data or specific models coming from experimental tests.
Setting of testing plans
The setting of most suitable tests depends on the phase at which the development product is (the product can be a device or a material).
During the prototyping phase, the use of HALT (Highly Accelerated Life Tests) Tests is suitable. The aim of these tests is to verify the strength of the product subjected to different stress conditions (temperature, humidity, voltage, etc.) They are usually brief but with intensive stress.
HASS and Burn-in Tests
During the production, it is often necessary to perform stress tests to identify and remove those products (devices or materials) whose failures will be showed over time and are not identifiable through the common check tests in the production. These products are the weak population, and they can be identified by specific stress tests called HASS (Highly Accelerated Stress Screening) and known as burn-in test in the past.
The qualification tests are those on which are based the reliability evaluations of the device (MTTF, MTBF, useful life). They are usually accelerated tests because their aim is to accelerate one or more failure mechanisms. It is particularly essential being able to link the qualification tests to the specific failure mechanisms into which the product runs during its real application by the client. It is also important to set the test parameters to avoid the activation of abnormal failure mechanisms or, on the contrary, to have too low acceleration factors.