The techniques used by our experts reduce the risk of releasing products that do not comply with market expectations and standards.
Reliability has a crucial role in client satisfaction and a deep impact on the safety of many products released on the market (automotive, medical, etc.).
Gestlabs supports the client with a rigorous, scientific approach — identifying the stress tests and laboratory analyses suited to the specific failure mechanisms. Our personnel can support the client in all phases of the product life cycle, from design to prototyping and production qualification, with the identification and performance of the reliability tests.
Methods
Our technicians use the following methods to guarantee the reliability of the products released to clients:
MTBF calculation and the failure rate
The MTBF (Mean Time Between Failures) calculation is one of the cornerstones of reliability; it aims to predict the failure of a device during its useful life, before wear-out. The MTBF and the failure rate (its inverse) can be determined by experimental tests or, for electronic sheets, by specific standards. The MTBF value is an essential requirement for the customer and is necessary in many fields such as automotive, medical and aerospace.
Useful life
The useful life is the period when the device works optimally and is not yet affected by wear. It usually extends beyond the warranty period and corresponds to the client's duration expectation. It can be identified through accelerated stress conditions or, in the design phase of electronic sheets, through specific calculations in compliance with specific standards.
Distributions for reliability
Statistical distributions (chi-squared, Weibull, exponential, etc.) are necessary to accurately perform reliability predictions from the data obtained by the tests. They allow the MTTF (Mean Time To Failure) and MTBF to be determined with confidence ranges based on the size of the sample used.
Accelerated stress tests and acceleration factors
For reliability predictions it is often necessary to go beyond theoretical calculations and perform specific stress tests that accelerate specific failure mechanisms. Accelerated tests involve accelerating factors such as temperature, humidity, power and voltage. It is essential to link the most suitable accelerating factors and values to the different failure mechanisms, to avoid activating abnormal failure mechanisms or having insufficient acceleration. Acceleration factors can be determined from experimental data or from specific models derived from experimental tests.
Setting of testing plans
The setting of the most suitable tests depends on the phase the product (device or material) is in during its development.
HALT Tests
During the prototyping phase, HALT (Highly Accelerated Life Tests) are suitable. They verify the strength of the product subjected to different stress conditions (temperature, humidity, voltage, etc.) and are usually brief but with intensive stress.
HASS and Burn-in Tests
During production, stress tests are often necessary to identify and remove products (devices or materials) whose failures would appear over time and are not identifiable through common production checks. These products are the weak population, and can be identified by specific stress tests called HASS (Highly Accelerated Stress Screening), formerly known as burn-in tests.
Qualification Tests
Qualification tests are the basis of the device's reliability evaluations (MTTF, MTBF, useful life). They are usually accelerated tests aimed at accelerating one or more failure mechanisms. It is essential to link them to the specific failure mechanisms the product encounters in real application, and to set the test parameters to avoid activating abnormal failure mechanisms or having too-low acceleration factors.