adequately with technical uncertainties
& Quality Management
calculation with MIL-HDBK-217
As of 2015, updates are not planned. Taking into account that
reliability prediction standards are based upon field failure data
collected over many years, we can conclude that Mil-HDBK-217F notice 2
reflects the electronic status quo of the late 1980s.
It is obvious that using the Mil-HDBK-217F notice 2 in its original
manner would yield results that don't have any reasonable relationship
with today's electronics.
Despite the RoHS directive, today's commercial electronic components
are beyond any doubt more reliable than military grade components have
been in the 1990s.
This problem has been addressed by a consortium of military and
aviation companies by developing the ANSI/VITA 51.1 in 2008.
can be perceived as an
add-on for the Mil-HDBK-217.
Members of the
consortium were Boeing, Northrop Grumman, GE, Honeywell, just to
mention a few, as well as former Relexsoftware company, whose
reliability software suite Relex has been taken over by PTC and renamed
Quality Solutions in 2010.
recommendations for quality factor assessment for today's commercial
electronic components. By applying ANSI/VITA 51.1, Mil-HDBK-217 results
on component level would improve by a factor between 1 (switches,
connectors, quartz, fuse) and 100 (birdseed like R and C), depending on
the component type. On PCB level, results would improve by a factor of
3 to 5, which is still pessimistic.
factor = 1 means no
improvement at all. For whatever reason, the consortion has recommended
that for switches and connectors, quality factors shall be
assessed in the original Mil-HDBK-217 manner, and for fuses and
quartzes, there is no recommendation at all.
As a result,
switches and connectors
have become the key contributors in MTBF calculations if the ANSI/VITA
51.1 recommendations are strictly followed.