The surface flatness is really the issue here and somewhere the design
activity picked up from a PC house that they use a fine glass against
the foil layers to ensure good circuit development. The idea that a
laminate supplier can produce a smoother surface because of lam
technology may be true for some, but not for most. Good lamination
technologies will product similar surfaces, with differences not large
enough to impact subsequent imaging processes. We actually see that the
more resin in the package has an adverse impact on stability, which
given the current design technologies has a much higher control priority
than surface geometry from glass type. A good Copper/Aluminum/Copper
build technology will produce very flat surfaces with all glass styles,
which provide a latitude of build options and package control for the PC
fabricator.
Jeffrey Bush
Director, Quality Assurance and Technical Support
76 Technology Drive - POB 1890
Brattleboro, Vermont 05302-1890
Tel. 802.257.4571.21 Fax. 802.257.0011
[log in to unmask]
http://www.vtcircuits.com
-----Original Message-----
From: Tom Burek [mailto:[log in to unmask]]
Sent: Thursday, April 08, 2004 4:34 PM
To: [log in to unmask]
Subject: [TN] PCB Laminate/Stackup question
Hello Technetters,
I have a question about layer stack-ups. Some time ago a respected
contributor to this forum presented us with some valuable information in
the form of a specification he developed. In this specification, under
the title, MASTER DRAWING NOTES 1.0 Laminate, Core and Prepreg Material,
section 1.9 states,"There shall be no 7628 glass style prepreg used
facing copper. If required, single ply or multi-ply 7628 core material
may be used. If used as prepreg, 7628 only may be used between two
other more resin rich glass styles." My question is what does this mean
to the stack-up? Why should you not use 7628 facing copper? Does it
have to do with the amount of resin not present in 7628 and may not bond
to the copper sufficiently? What should be used? and Why?
I hope this question is not too imposing.
Thank you in advance.
Tom Burek, CID+
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