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July 2004

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Subject:
From:
Jeffrey Bush <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 13 Jul 2004 10:15:02 -0400
Content-Type:
text/plain
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text/plain (134 lines)
If needed for performance, the stackup on the drawing should only
specify the required dielectric thickness and finished copper weights.
The PCB can be constructed in many several methods to obtain the desired
end thickness.  If, for example, you spec out some plies of 2116 glass
in an opening, and supplier B only uses 2165, this becomes an issue.  If
signal/performance integrity is not an issue in the design, leave it up
to the PCB fab house and the compliance testing to your drawing
requirement to ensure thermal and mechanical integrity is there.  



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: Roger Stoops [mailto:[log in to unmask]] 
Sent: Tuesday, July 13, 2004 9:05 AM
To: [log in to unmask]
Subject: [TN] Board Stack geometry


This brings up a question I have had bumping around in my head for a
while, for example:

A pcb has been designed, assembled, tested, and now goes through FCC and
CE emissions and susceptibility testing.  The board stack was determined
by the pcb vendor.  The assembly passes first time.  Purchasing or the
EMS finds a less expensive yet reliable board house and buys production
boards from this new house.  The new house changes the board stack to
their preferred lay-up.

Would not this board need re-testing for FCC/CE
emissions/susceptibility?  For boards requiring this type of testing,
would not a board stack specified on the print be required?

TIA and much appreciated,

Roger Stoops


-----Original Message-----
From: Jeffrey Bush [mailto:[log in to unmask]]
Sent: Monday, July 12, 2004 8:40 AM
Subject: Re: 7628 prepreg?


Common type, stable, low resin content and likely predicable thickness
is this is important.  Otherwise PCB house should be left to determine
the optimal stack for the board geometry and end use.



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: Brooks,Bill [mailto:[log in to unmask]] 
Sent: Friday, July 09, 2004 5:08 PM
To: [log in to unmask]
Subject: [TN] 7628 prepreg?


Bill Brooks
PCB Design Engineer , C.I.D., C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 http://pcbwizards.com

Why would a designer specify 7628 prepreg in the construction of a
board? What characteristics are unique to it? Bill Brooks, CID

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