I don't believe the difference in reliability between core and foil
construction is significant but you should know that core layers are
less prone to reliability failures than foil layers. This is because of
the nature of the semi-cured b-stage and multilayer fabrication.
Cores are uniform and well cured by the laminator, any construction
using a b-stage (glue) layer are subject to the vagrancies of the
fabricators lamination process. B-stage layers have to conform to the
topography of the image that is being laminated so you expect resin rich
and resin starved areas within the dielectric plane. Those variations
may be expressed as a reliability failure (copper or dielectric) invoked
by the thermal excursions of assembly and the end use environment.
Material damage, when present, is usually in the b-stage areas.
Thicknesses between layers vary greater in the b-stage layers. These
variations are inherent in the lamination process, they cannot be
avoided but they can be mediated by construction methods. We measure the
capacitance between ground planes and plot a construction profile of
each board (coupon). We have found, as was anticipated, more core layers
there are in a construction the greater consistency the "capacitance
profile" of the board.
At best core verses foil construction is a fourth level influence in PWB
reliability, but it is a measurable variable.
Sincerely,
Paul Reid
Program Coordinator
PWB Interconnect Solutions Inc.
235 Stafford Rd., West, Unit 103
Nepean, Ontario
Canada, K2H 9C1
613 596 4244 ext. 229
Skype paul_reid_pwb
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Marsico, James - ES
Sent: May 17, 2011 10:40 AM
To: [log in to unmask]
Subject: [TN] Core vs Foil Lamination
Good Day Technet:
We have a heritage PWB design for a space application where our drawing
requires a core laminating process. One of our suppliers is requesting
using foil lamination in lieu of core lamination for registration
issues. Since we qualified the original core lamination, can foil
lamination be a direct substitute?
Thanks in advance,
Jim Marsico
ITT Corporation
1500 New Horizons Blvd.
North Amityville, NY 11701
631-630-5079
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