On Sun, 30 Jun 2013 07:34:04 +0000 (UTC), "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?

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?

Geoff.
One of the most difficult parametrs to evaluate is life expectancy.
It's trivial to test a lot of caps and determine if they meet
capacity, ESR, and leakage specs. Note that even high end (Panasonic)
caps have a rated life expectancy of less than 10,000 hours at rated
temperature, surge, etc. That's less than 14 months. Calculting a
probable life expectancy at the much lower temperature and surge they
nrmally operate at would be difficult. Still, it is obvious that some
brands (Capxon, Elite Lelon) consistently fail much earlier than
others.

PlainBill