Jack, it sounds to me like they have extraneous copper from the etching
process. Handling the inners and using screw drivers to scrape the surface
is certainly way out there beyond the norm. Were the inner layers already
processed through the oxide? The black solution they were washing the
circuitry with is also mysterious. I would run, not walk, away from any
shop that was reworking inner layers like that.


At 06:48 AM 09/16/2005, you wrote:
>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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