My first trip to China I visited a factory that made communication systems
used in mines. While there I saw 100s of operators reworking gold contacts
by peeling off the fingers and riffeting gold ribbon onto the boards. This
was being done because the fingers were not matching up with the plug in
connectors. There stated yields were 100%. What you asked is not common
practice at a good shop and that is why I have always looked at first pass
yields. I would no think that they monitor those numbers. It is not uncommon
to do some rework on inner layers by picking off extraneous copper but if it
is the norm it tells me that process control is weak.

Scott B. Westheimer

 ----- Original Message -----
From: "Jack C. Olson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, September 16, 2005 8:48 AM
Subject: [TN] Bare-Board Inner-Layer Fab Quality


> 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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