"Geoffrey S. Mendelson" wrote:

Michael A. Terrell wrote:

They were still substandard, but for the all too well know industrial
espionage. The companies stuffing the motherboards bought them because
they were the cheapest crap they could find.

Ok, a matter of semantics. When I think of substandard I think of
someone selling parts that are not manufactured to spec, for example,
a 50C (yes, I know no one sells them as such) cap labeled 85C.

Or a 33mf capacitor that is really 25mf.

These really were up to standards, they had the correct capacitance
and were properly temperature rated. The failure was due to them being unable
to age, which may be considered a manufacturing error, or a design flaw,
planned obsolecence, or outright fraud.

I guess the standard they failed to perform to was MTBF, but was it specified?


Only a fool would buy caps without a rated lifetime. In most places,
engineering has to approve components before they can be placed in the
system. An 'Item Master' is generated, which has all the
specifications, and should include a datasheet that was in effect at the
time the part was evaluated. Any company that ignores the approval
process is crooked, or incompetent.

The first step is being placed on the 'AVL', or 'Approved Vendors
Lists'. Then each and every component has to be tested & approved. The
testing will depend on the level the company builds to. I approved some
Hitachi and Bourns parts to replace EOL Motorola & Beckman ten turn pots
with an unacceptable failure rate of over 1% due to a manufacturing flaw
caused by their using undersized 'O-rings'. The Bourns had a zero fail
rate for the thousands we used, per year. I also found and added some
'Capstore' RAM to replace the lithium battery powered 2K * 8 we used.
They were not allowed aboard the shuttle or space station, and early
EEPROM was too flaky for the application. The maximum write cycles
would have given too short of a useful lifetime and it's expensive to
service something in orbit.


Is there a standard for capacitors? Or is that something you compute based
upon temperature rating, expected operating temperature etc, and there
is no standard at all, beyond your calculations?