First, I am no expert on accelerated life testing. However,
I do know that life testing depends a good deal on the nature
of the product. In other words, how will it be used, how often
will it be used, and what are its failure modes?
An electric pencil sharpener may be used only five to ten times
a day for about five seconds each time, and has as much mechanical
content as electrical content. An electronic control system may
have no mechanical failure modes, but run continuously (24/7).
I do recall from the early days of solid state electronics that
there were three principle aging factors: (1) on-off cycles,
(2) power on hours, and (3) calendar hours. On-off cycles
cause heat expansion/contraction at all of the electrical
interfaces (e.g. solder joints) that lead to stress fractures
due to differing thermal coefficients of expansion in the joint
materials. Power on hours "age" the solid state junctions at a
temperature dependent rate (each 10oC halves the lifetime).
The "calendar" age of the electronics, whether ever powered on
or not, will result in some "natural death" failures of the
components.
Since most products can be repaired (if they are worth it), each
repair extends the useful life of the product. Think about your
automobile. Extreme rusting of the chassis is about the only
failure that cannot be easily repaired.
George Alspaugh
-------------------------------------------
This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.
Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/
To cancel your subscription, send mail to:
[email protected]
with the single line:
unsubscribe emc-pstc
For help, send mail to the list administrators:
Michael Garretson: [email protected]
Dave Heald [email protected]
For policy questions, send mail to:
Richard Nute: [email protected]
Jim Bacher: [email protected]
All emc-pstc postings are archived and searchable on the web at:
No longer online until our new server is brought online and the old
messages are imported into the new server.
