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The Arrhenius Equation is widely used and accepted by reliability and validation engineers from many industries to develop accelerated life tests (ALT) for thermal aging environments.
The general form of the equation describes the reaction rate of a process as a function of temperature (K), the Boltzmann constant (8.617E-5 eV/K) and two empirical factors. It can be written as:
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An example of an automotive validation test reliability target is R97C50. In this case, the objective of the validation effort would be to demonstrate at one life on test, with 50% confidence, that the product has a reliability of 97% or better.
Does this mean that a field failure rate of 3% can be expected?
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As you begin design validation (DV) and product validation (PV) testing you are entering the more formal phase of a test program. Usually, you are working to internal and/or customer test specs with timelines that are critical and little margin for error. If you’ve conducted adequate design verification testing and given your parts a chance to fail on test exposures that are similar to those your product will see in the field, you have reason to expect to be successful in validation [see previous article outlining accelerated test methods: Expect to Pass Validation].
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Product Validation Testing is a critical and expensive endeavor. The part build process must align with the latest prototype process (for Design Validation (DV)) or production process (for Product Validation (PV)) and be fully documented for posterity. Depending on the product and application, the validation test plan consists of a battery of tests, some of which are lengthy – often six months or more. Because of this, DV and PV test plans are invariably on the critical path for a customer program. Test failures that require fixing the design and repeating DV or PV jeopardize project timing and company profits. Further, they jeopardize the customer program along with your company’s reputation.
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