This is a question for anyone who is intimately familiar with bare-board
fabrication.

I've recently returned from a trip to China and Taiwan to visit five fab
vendors.
During one of the tours, I noticed people doing a lot of rework on inner
layers,
scraping metal flecks off with screwdrivers and scrubbing crud off of
conductors
with this black (alcohol?) stuff. I asked the tour guide what their
inner-layer
yield was, and he said 99.5%

huh?

Is that how people do it? I've only been on maybe two board tours in the
states
in the last couple of years, and that issue never came up. So maybe that's
just the
way it is done, but what BUGS me about it is they don't record how many
repairs
they are doing on each layer, and it looked like different operators had
different
criteria for what constitutes a reject, and by claming such a high yield
no one
ever looks at the process right before it that is putting all the crud and
metal flecks
on the layers to begin with!

Jack (the "I thought I'd seen everything" guy)



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