Highly Accelerated Life Testing (HALT and MEOST)
HALT (Highly Accelerated Life Testing) is an accelerated product reliability test method focused on finding design or component weaknesses in a product. Incorporating HALT testing during development helps to shorten the total product development time and failures can be found and fixed before they become expensive field issues after product launch. During a HALT test a product is subjected to a series of overstresses to accelerate fatigue in the part of interest. The samples are tested far outside the normal operating conditions. HALT testing supports design verification in a fast and efficient way and can reveal failure mechanisms in a few days instead of weeks or months.
HALT testing is based on stressing the product via a range of different potential parameters. A HALT test is typically based on the following five tests:
- Temperature Step Testing: In order to determine the lowest and highest operational temperatures
- Rapid Temperature Cycling: The product is submitted to fast temperature changes with boundary conditions previously determined during Temperature Step Testing
- Vibration Step Testing: The product is submitted to an increasing level of vibration until the products fails in relation to the operational functionality
- Combined Testing: A combination of the tests described above
- Destructive Testing: In order to determine the lower and higher destructive temperatures and the destructive vibration level
MEOST (Multiple Environment Overstress Testing) is used to prove the robustness of the product of interest before it is taken to the market. MEOST is a testing methodology that stresses the product as far as possible beyond the design specifications, but within the known destructive limits (defined or previously determined via HALT testing). A combination of stresses is applied to create interactions that can lead to product failures. MEOST makes use of environmental stresses in combination with dynamic electrical input and output parameters.
MEOST testing is based on exposing the product to a combination of environmental and use-case scenarios that the product would be exposed to during typical use. For MEOST testing the following guidelines are followed.
- Use practical stressors such as input voltages and frequencies, and use variations of these
- Use practical output stressors such as different loads and changes in load
- Define user case handling sequences, such as on/off switching and different typical operating modes
- Select several relevant stress conditions and combine them in a test profile. Apply these stress conditions simultaneously and run a sequence of these repetitively
- Use overstresses and high stress rates