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March 2001

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Subject:
From:
Yehuda Weisz <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 14 Mar 2001 23:30:56 +0200
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Hi James,
I don't claim to be an expert on the subject but I'll throw my 2 cents in.
I can think of several advantages to foil lamination (or disadvantages to
core lamination):

Dimensional stability: When you do core lamination usually the two
outerlayers are only "half processed". During innerlayer phase  only layers
2 and "n-1" are imaged and etched on the innerlayers, while the CS and PS
are still full copper. This results usually in a layer that is less
mechanically stable, has a tendency to "curl up" (a real fun in conveyorized
machines). It is a potential source for misregistration.

Extra layers : If you count the number of physical layers (i.e - layer
pairs) you need with core lamination vs. foil lam. you'll find that with
core lamination you need and extra layer for each panel. It might not be the
end of the world and its relative importance depends on your layer count but
there is a difference.

However, if you have a tight specification for the dielectric distance
between the two outerlayers (controlled impedance for example) than having a
core in there is much more exact than relying on the final thickness the
prepreg will receive after lamination.

I know that there are manufacturers who will use core lamination for the
higher layer count boards. They claim that it gives more reliability to the
PTH. I have never experienced this difference myself but it might be true.

I hope it helps a little.

Best regards,
Yehuda Weisz
----- Original Message -----
From: Marsico, James <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, March 13, 2001 5:53 PM
Subject: [TN] PWB FABRICATION


> Could anyone (I'm sure a lot of you can...) explain the pros and cons
> regarding foil lamination vs. the conventional core lamination for
> multilayer boards?  I'm not just looking for cost, but engineering,
> performance and reliability considerations.
> Thanks,
> Jim Marsico
> Senior Engineer
> Production Engineering
> AIL/Electronics Systems Group
> An EDO Company
> [log in to unmask] <mailto:[log in to unmask]>
>
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