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September 2005

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Subject:
From:
Jeffrey Bush <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Jeffrey Bush <[log in to unmask]>
Date:
Wed, 14 Sep 2005 07:34:00 -0400
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Appear to be normal epoxy fill of the blind via to the surface copper.
The center via shows the epoxy above the surface plane.  Poor sealing of
the via at lamination coupled with inadequate resin removal
post-lamination appears to have created the bumps.  The extent of epoxy
bumps would have required some mechanical planarization, which is not
needed in this design if the correct materials and process are used to
dam the resin from flowing topside at lamination.  We use Paco-Via which
results in a slight dimple as the material conforms the via during
lamination.  Other materials like copper foil are used which do result
in a larger bump that could required planarization.  

Very good Okie microsection - comparable to any Yankee attempt!  

Jeffrey Bush
Director, Quality Assurance and Technical Support

VERMONT CIRCUITS INCORPORATED
  76 Technology Drive - POB 1890
    Brattleboro, Vermont 05302
      Voice: 802.257.4571.21 Fax: 802.257.0011
           http://www.vtcircuits.com
 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, September 13, 2005 5:44 PM
To: [log in to unmask]
Subject: Re: [TN] raised vias...I did a "Okie" cross-section

Hi All!

I have a local shop here do a lot of cross-sections for us, but I
couldn't
take
the board over to them until tommorrow. But I was so curious to take a
look
at the bumps, or "raised vias", I decided to do what I could, to see
what I
could.

We're not set-up to do cross-sections here (that may change in the
future),
but I took a dremel tool and got close to where I wanted to look, then
started
using finer and finer grit wheels. Then I used an exacto knife and
carefully
scraped material away until I was able to see how things looked at the
raised vias. This was done under a microscope, and I mean it was done
carefully.

I know it's not as good looking as what a real cross section would look
like,
but it does give an idea of how things look. Go to:

http://www.stevezeva.homestead.com  and look at "Okie Cross-section".

I still don't know why I have the bumps...they look like they're solid
copper.

Kind regards,

-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
__________________________________________________________________
This message may contain information that is privileged and confidential
to
LaBarge, Inc.  It is for use only by the individual or entity named
above.
If you are not the intended recipient, you may not copy, use or deliver
this message to anyone.  In such event, you should destroy the message
and
kindly notify the sender by reply e-mail.

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