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

Ideal Uses

HALT: Examining prototypes for weak spot identification during the product design process
HALT: Defining the MPOSL (Maximum Practical Over Stress Limit)
HALT & MEOST: Suitable for the study of complete systems, subsystems or just parts
MEOST: Investigation of intermittent failures, e.g. for examination of products that apparently failed in the field but get a diagnosis of ‘no failure found’ when returned for repair.
HALT & MEOST: Useful for comparison of current generation versus future proposed generations of the product

Strengths

A complete facility with integrated logging service and multiple channel dataloggers for user definable signal measurement
Software controlled AC and DC power supplies can be integrated into the testing set-up if needed
A master control program is available that can control the chamber and the power supplies to run automated and cyclic programs
Expert in-house analytical staff and instrumentation available for failure investigations
HALT engineers directly available to support customers hands-on during the design and execution of HALT testing and can give advice to get the best and maximum use from the results of HALT testing

Limitations

Less successful for pure mechanical product testing
Not suitable for lifetime prediction
Only random vibration, the frequency spectrum is not adjustable
No controlled humidity

Technical Specifications

Chamber temperature range: -100°C to +200°C
Temperature change rate: 60°C /min
Fast temperature cycling
Random vibration in three axes up to 70 g (rms)
Combined stress of temperature and vibration
Vibration table size 75 cm × 75 cm
Maximum table load 300 kg