Hactar wrote:

In article ,
Michael A. Terrell wrote:
George wrote:

RickH wrote:

China can make things real cheap and fast, but they dont believe in QA
departments.

Don't kid yourself. They are quite capable of making quality stuff. Its
the "Walmart mentality" buyers who keep on insisting on even cheaper
prices so then the quality falls as expected.

There was some ass on sci.electronics.design a while back trying to
sell his company's SMD crap and bragging, "It only has a 1% failure
rate".

Think about this: If a board has 100 parts that means on average, you
have a 100% average failure rate for an assembled board. If it has more
parts, the rate goes up, as well.

How can it possibly go up? A basic course in probability would serve
you well.

"1% failure rate" means each part has a 99% probability of NOT failing
(in some unspecified timespan, maybe on delivery).

Their spec was at delivery.

Put 100 of these
together and (assuming the failures are independent) the assemblage has
a 0.99^100 = 0.366 = 36.6% probability of not failing (in the same
timespan). That means a 63.3% chance of failure.


How many products have you see with less than 100 components? The
last design I worked on had over 5,000 SMD components.


You've never met Mr. Murphy have you? Motorola had well over 100%
failure rate at the end of the production line on their TV sets when
they sold their consumer electronics division to Matsu****a. The
components they were using were well over .1% failure rate, yet they had
multiple defects in most sets, and very few that worked in final test.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida