Steve

To add more fuel to the fire, I would say this was caused by entrapped air
bubbles in the electroless process. This could be related to drilling as
well since poor drilling can increase the likelihood of entrapped air
bubbles. I would look at both processes.

Best regards

Lee

J. Lee Parker, Ph.D.
JLP Consultants LLC
804 779 3389


----- Original Message -----
From: "Robert Lazzara" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, December 14, 2006 4:54 PM
Subject: Re: [TN] How does this happen?




In a message dated 12/14/2006 4:24:06 P.M. Eastern Standard Time,
[log in to unmask] writes:

Further  still, how does one panel get screwed-up like this and not  the
others?



____________________________________


Hi Steve:

That's an interesting picture. I decided it might be best to look at the
photo from the perspective of a client asking me to deliberately create
that
particular effect (and with a gun pressed firmly to my head).

For me, it keeps coming back to drill. I could create something like that
through controlled depth drilling. And it can also be done accidentally.
Here's
1-way how:

Most low(er) tech PCB designs permit stacked mechanical drilling. Typically
on .062" material a Fabricator can drill 3-high (.062" x 3) with reasonable
results. However, if the drill bit were to slip in the collet it's possible
the
 drill might not penetrate through all three stacked PCBs. If it went
through
the  first two PCBs but only partially through the bottom PCB, the effect
would be a  partially drilled exit aperture with a pronounce lip.

This theory also offers an answer to your question, "...how does  one panel
get screwed-up like this and not the others? By only affecting the  bottom
panel, most of the product continues unaffected. As for it being only
1-panel
(so-far) it's possible that the Fabricator actually caught the  error and
reworked all but 1 panel (the notorious "escapee").

It's required to note that E/T wouldn't catch this as the  PTH is likely
fully functional electrically.

It may also be interesting to note that while most drill machines have
devices or sensors for detecting broken or missing drill bits, not all have
the
ability to critically monitor drill bit length.

While I may be way-out with my suggestion, I'll hang onto it  until a few
more pictures show different angles (or folks more sane and  experienced
have
time to respond).

Until then -

Bob

ROBERT LAZZARA
VP, Business Development
T: (800) 560-9457
F:  (800) 878-5566 (y servicio de mensaje español)
E:  [log in to unmask]
W:_  www.CircuitConnectUSA.com_ (http://www.circuitconnectusa.com/)



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