Speaking from experience, life on the edge...edge of a
facility's manufacturing capability is not a fun edge on which to teeter.
There is a cliff on one side of that edge and an unpleasant fall when pushed
over that edge by unpredictable yields, low yields, deviations requiring
engineering time to determine acceptability and flat out non-delivery. Do
your company a favor and take as many steps back from that edge as you
can.
Best
Regards,
Jana
Carraway
Thank you Boston Brad,
this is some great information. My engineer seems to only be thinking on
the level of what the flex manufacturer capabilities are and not actual usage
of the part. This will help me in my arguments against his will to go as
small as the shops are boasting because he can.
Thank
you,
Dee Stover [log in to unmask]
Associate Technician
Design
National Optical Astronomy Observatory
950 N Cherry
Ave
Tucson, AZ 85719
www.noao.edu
520-318-8489
FAX
520-318-8303
At 09:43 AM 7/12/2002 -0400, you wrote:
Dee,
Trace width
is a function of risk. A happy face button with blinking eyes; 2mil
line. A Defense Missile; 8 mil line. The 2mil very short
distance like <.2 inch, the 8mil, on flex, about 8 inches. The
length on the 2mil is function of PCB process wherein the 8 is more end
configuration/usage of part.
Many, many more complexities come to the
table; dielectric callouts, robust design, Supplier selection, and the
like. Personally I still believe it comes down to annular ring for the
process and limiting the number of flexures prior to install. The
number of flex layers also plays a large roll in reliability.
I have
done sub .005 widths on flex. It is flex-flex not rigid-flex and for
short distance, even the cable itself is small and limited layers. To
predict your situation: based on 5mil in the flex, the designer didn't
have correct input and the vias are to close to the rigid flex area, you
have a less than optimum stack up, probably a thickness issue and the pad to
PTH size combined with a >90 degree flexure is giving you some
intermittent opens.
I would look at the entire configuration from a
systems approach perspective, it is probably not one item.
Good
luck,
Boston Brad
Bradford Saunders
Packaging
Consultant
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in the
BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send
e-mail to [log in to unmask]: SET Technet Digest Search the archives of
previous posts at: http://listserv.ipc.org/archives Please visit IPC web
site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
---------------------------------------------------------------------------------
---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To
unsubscribe, send a message to [log in to unmask] with following text in the
BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or
(re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet
NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail
to [log in to unmask]: SET Technet Digest Search the archives of previous posts
at: http://listserv.ipc.org/archives Please visit IPC web site
http://www.ipc.org/html/forum.htm for additional information, or contact Keach
Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------