Much has been written on what to do in HALT and HASS. What not to do should also be discussed in order to enforce the positive. Some of the most commonly occurring mistakes will be discussed and it will be pointed out why each is a mistake. The mistake is first stated in bold type and then is discussed very briefly. All of these are covered in more detail in my textbook, HALT and HASS, Accelerated Reliability Engineering, which is
sold through Hobbs Engineering.
Not performing Safety of HASS.
This is one of the worst possible mistakes that can be made and is somewhat equivalent to playing Russian Roulette with several cylinders loaded. Highly Accelerated Stress Screens are quite capable of reducing the usable field life of good hardware if the stresses are chosen to be too high for the design and processes under which it is built. If HALT has been properly done, then this rarely occurs. If HALT has not been done at all or if the margins attained are not high enough, then field life reduction may occur. The only way to reasonably prove that the screens are safe to use in production is to run Safety of HASS. If this is not done, then the field
failures will determine if the HASS has been proper or not. Clearly, this wait and see approach is not a good way to find out if the screens are too intense as, by the time it is recognized that the screens are too intense,
substantial numbers of reduced life units will have been shipped. Safety of HASS is mandatory for proper technique.
For the complete paper click here pitfalls-to-avoid-in-hh
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