Thanks for writing back.

the board is 5" x 6" x .062"
ENIG finish
larger head driver M4 screws
7 mounting holes around perimeter with large through-hole mil circular
connector
copper annular ring on all 8 layers
one assembler
vibe and thermal stress for many years
this is a new design
someone was just *WONDERING* out loud if the QFP was too close to the
mounting hole, *no failures*
(Now it is up to me to prove it is ok)

Here is a partial picture:
http://frontdoor.biz/PCBportal/QFP144mtg.gif

thanks
Jack


On Mon, Jan 14, 2013 at 11:36 AM, <[log in to unmask]> wrote:

> Jack,
>
> A few questions to start the brainstorming process:
>
> How large is your board and the spacing between mounting screws?  What
> is the board thickness and plating finish?  Any mounting screws in the
> middle of the board?  What size/type of hardware?  How is hardware being
> installed - larger head driver or screwdriver.  More than one assembler?
> Has the board seen any vibration or thermal stress after mounting?  Does
> the mounting screw area have top layer clad?  What percentage have
> exhibited this failure mode?
>
> 100 mils is too close for my liking, but I don't have a good rule of
> thumb for you though.
>
> Jim Carlson
> Quality/Configuration Manager
> L-3 Communications
> Applied Signal & Image Technology
> 443-457-1111 Ext. 238
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Monday, January 14, 2013 11:36 AM
> To: [log in to unmask]
> Subject: [TN] Mounting Hardware to QFP Component Lead
>
> To the assembly professionals out there:
>
> Have you ever had reliability issues with mounting screws if they are
> near a Quad Flat-Pack? My 144 pin land pattern is pretty close (100mils)
> but we are mounting the board into a very flat structure (no bowing) I
> can't imagine the compression of the board material could affect
> gull-wing style lead connections (maybe BGA?) but I don't know...
>
> thanks,
> Jack
>
>
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