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July 2004

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Subject:
From:
"COOKE, ROBERT W. (JSC-NX) (WGI)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 13 Jul 2004 08:38:47 -0500
Content-Type:
text/plain
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text/plain (132 lines)
Roger,

Any change of the stack order has the potential to change the conducted and
radiated emission signature.

A significant investment ($$$$) was made through the FCC and CE testing to
get the design "qualified", which technically means that the design at that
point is "locked" and cannot change. Changing a qualified design invalidates
that qualification.

Unless the customer specifically authorized a change in the "qualified"
design, the new board house should either assemble the board as originally
designed and qualified, or foot the bill to have the new stack design tested
and requalified.

And yes, the layer stack drawing should have been part of the original
qualification submittal.

Bob Cooke

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Stoops
Sent: Tuesday, July 13, 2004 8:05 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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