Qualification and Reliability “Exploit the Acceleration of Time”

Semiconductor Consultant, Automotive Reliability. Qualification, AEC Qualification

Qualification timescales as part of a new product implementation or Change evaluation is significant, potentially leading to some products late release or release prior to full qualification.

A product expected to have a lower than 1 PPM (Parts Per Million) failure rate, cannot feasibly wait until the first few million units have been tested. Similarly, impractical for a product with a lifespan of 10 years to undergo a decade of testing, prior to release to the market.

Use accelerated methods to reduce both time and testing, thereby enabling an acceptable “Time to Market”.

Accelerated life testing is a concept that, while straightforward at its core, becomes more complex in application. A product designed to withstand 1,000 hours could be tested in half the time with twice the stress applied.

The process involves testing a product by subjecting it to stress conditions such as temperatures, voltage, vibration, and pressure that preferably exceed its normal service parameters. This is done in an effort to uncover faults and fail modes, in a shorter amount of time.

Many mechanical properties of polymers, such as creep, stress relaxation, and tensile properties, exhibit an Arrhenius-type relationship, with time and temperature. This is one of the reasons the Arrhenius equation is so frequently cited.

Shorter tests at elevated temperatures can be used to extrapolate the behaviour of the polymer at room temperature over a longer periods. For example a product with a life cycle of 10yrs @ 60C would be the equivalent of 1626Hrs @125C (10 weeks) or 487hrs @150C (3Wks).

Attached to this post is a spreadsheet often used to calculate HTOL (High-Temperature Operating Life) test points and provide customers with a basis for determining test times.

Can also be used for HTSL (High-Temperature Storage Life) timescale equivalents and calculating timescales to evaluate suspect risk lots (although eV value should be considered).

Additional Important Notes:

It is possible to either increase or decrease test stress (temperature) to speed up the testing or reduce stress during test, however it is necessary to note.

  • It is crucial to consider the other test board components that will be subjected to increased temperatures.
  • Elevating the temperature beyond the absolute maximum rating of either the fabrication or assembly process may invalidate the results.

Semicons-Global Ltd is here to help you plan for your components qualification, optimize conditions to complete qualification within your products needs and to provide our clients with the best consultancy support.

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