Selecting the Correct ALT
Abstract
Adam and Fred discuss the criticality of selecting the correct ALT for the product to be tested.
Key Points
Join Adam and Fred as they discuss the different types of ALT models and some common pitfalls when selecting the correct one
- Don’t just blindly use a model that worked on a previous product even if it’s a legacy product.
- Does your team understand the primary wear-out failure mechanism? Is it fatigue from temperature cycling, chemical reaction based on temperature level, or other modes?
- Creating the correct model for your product is a large investment but it can be used for many product iterations if applied correctly. Building an ALT is a long term returns initiative.
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SOR 036 Selecting the Correct Acceleration Test ModelAdam Bahret
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Accelerated tests are performed primarily to (a) identify or conform marginal design or manufacturing areas or (b) estimate product life. Prior to initiating accelerated testing, weak links should be investigated and potential failure modes eliminated
The most widely used model is the modified Coffin-Manson (Norris-Landzberg) Equation. This can be used to determine a Acceleration Factor for the thermal test condition and product environment. It uses: (1) an Arrhenius Term; (2) Temperature Cycling Frequency; (3) Maximum Temperature reached in a Cycle; (4) Temperature Range during a Cycle.
thanks for the comment Hilaire, and yes there are many models for acceleration factors out there – and one should be careful when adopting a particular models as it has to reasonably accurately describe the time to failure behavior changes due to changes in stress for your situation.
Always check, recheck and verify any assumptions lest you make decisions based on faulty or misleading conclusions.
Cheers,
Fred