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April 2002

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Subject:
From:
"Marsico, James" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 29 Apr 2002 15:18:00 -0400
Content-Type:
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text/plain (78 lines)
Dwight, just out of curiosity, why not plate ALL of the vias with 3 mils of
copper.  Wouldn't this be cheaper than drilling, plating, drilling and
plating again?

Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879


        -----Original Message-----
        From:   Dwight Mattix [SMTP:[log in to unmask]]
        Sent:   Monday, April 29, 2002 1:26 PM
        To:     [log in to unmask]
        Subject:        Re: [TN] Via Plug

        At 11:29 AM 4/24/2002 -0700, John Foster wrote:
        >Thanks Jim
        >
        >Did you do this extra plating selectively. Or did you just
overplate the
        >whole PCB.

        We have a lot of applications where we spec thermal vias to be
selectively
        plated to a minimum of 3 mils annular copper.
        The fabricator drills the thermal vias and selectively plates to 2
        mils.  Then they drill and (plate the rest of the board to 1 mil
(adding to
        thermal via copper as well).

        It's way more effective at heat transfer than any conductive epoxy
we've
        tried.   This approach is also very effective at controlling solder
wicking
        to the bottom of the board -- we'll use it sometimes when we don't
have a
        thermal problem but just want to control solder flow into unplugged
fields
        of gnd vias (saves masking backside).

        Dwight


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