Accelerated Life Testing (ALT)

ALT is performed to gauge the products useful life time, or to provide statistical confidence in the specified MTBF figure. ALT is quantitative in nature, and usually consists of running tests at higher than normal stress levels to accelerate the time to failure, or time to qualification.

ALT can also be conducted for one of two goals: qualitative testing and quantitative life testing.

Qualitative testing means we are attempting to identify failures without consideration for calculating the standard unit life in ambient operating conditions. Quantitative testing refers to using and ALT to predict the useful life of the product to gauge confidence in the units ability to survive a stated MTBF at ambient operating conditions.

Acceleration Methods

There are a wide range of acceleration methods available for use. Selecting the most appropriate stress to apply is done by evaluating the product's application and expected stresses that will be encountered during day to day use.

Some common models for calculating acceleration factor include:

• Arrhenius
• Eyring
• Coffin-Mansen
• Norris-Landzberg
• Inverse Power Law

When to Perform an ALT

ALT's are ideally performed when the product is nearing it's final design changes. This ensures that the test is conducted on mass production quality samples and will provide the most accurate results.

Approximate Costs

Costs to conduct an ALT range greatly, due to the variance in stress types that can be applied, and the levels of these stresses. Other considerations include number of units, confidence level, and distribution type. All of these aspects must be considered prior to constructing an ALT plan.

As an example, a product may be tested at elevated temperature for a number of days in order to qualify whether it is ready for mass production, and will not fail within the warranty period.

Contact us for further information on conducting an ALT on your product.