Hi Leo, and IPC LF Listservers,

To add a little to what you and Werner said about low stress levels,
probably low creep, and short life of some of these products.

Some of these products for compactness purposes; as well as 3D design, are
designed with flexible circuits, polyimide mostly, yet there are other
materials). This material is quite compliant if designed reasonably thus
extending life around the solder joint.

As Werner noted, and I think I noted back awhile ago on elevator
electronics, no one really does a failure analysis tree (prato, prade-oh)
of why these products stopped working so the data is lost. Unless we in
engineering get lucky and a big boo boo or medical or liability claim
occurs the data can be lost for years if not forever.

For Autos, since it is a longer life product, we get lucky since many
independent groups track relative reliability and give reports so this
forces this industry group to do a bit better work to come up above the
bottom of the relative reliability reports.

Most manufacturers copy others and some do have stress tests like dropping
something onto a metal plate from 5 feet several times, or going from hot
to cold fast to see if the product will survive infantile mortality type
failures. Yet most usually stop at this point UNLESS they have warranties
that will cost them big bucks (dollars, pounds, euros, yen, --)


Yours in Engineering, Dave
YiEngr, MA/NY DDave

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