Russell,

        In response to your question related to individual rigid flex
circuits that are fabricated in arrays or panelized and the techniques used
for separating them following assembly to prevent tearing of the flex
sections:
        We have never tried to panelize nest a Rigid Flex Design for
Assembly.  Most of our design configurations do not lend themselves to this
technique such as you would find in small rigid arrays.  We build dedicated
support fixtures to nest the individual parts in to help rigidized the
assembly for component population and soldering. The manufacturing
techniques used to fabricate the rigid flex do not always lend themselves to
your requested method. The lamination techniques employed to facilitate the
"breakaway" of rigid areas from the flex areas could be compromised and made
more complicated which would drive up cost.  The number of circuits designs
stepped and repeated on the manufacturing level panel could also become a
factor that could drive up cost.  If the number of circuits you could
produce on one panel at a time is greatly reduced in order to orientated an
assembly array you would need to do a careful cost trade off study to see if
you were saving anything.  Typically, the panelization of rigid flexes at
the manufacturing level are nested for best material utilization and are
rotated and turned all different methods depending on the profile.
        If you have a design that would be suited for the proposed method
then here are some general guidelines to consider.  Also get with the flex
manufacturer to discuss the panelization.

        Tab configurations "breakaway" - Best to keep limited to rigidized
section because the flexible material does easily tear.  The width of the
holding tab should be small enough to perform the break or clip out after
assembly. Typically, a 1/8 inch wide tab should work.  I've mostly only seen
the removal performed manually because of low volume and short runs.

        Tab positioning - Positioning would  be design dependent related to
the profile of the Flex Assembly.  You would have to look at the assembly
method, the overall size of the nested array, etc.  You would either have a
very specific detailed fab drawing with everything locked in or use
generalized notes to address the method on the drawing and give the
fabricator the flexibility to place the tabs to best rigidize the array.

        Designs techniques - If tabs are required at the flex areas to keep
support over a long flex run then you could design in some localized copper
tear guards that would stop a tear from propagating at the cut-away.
Another technique would be to locally laminate internal at tab areas a glass
supported adhesive button pad to provide tear resistance.

        Anyway that's a couple of thoughts on the subject that may answer
your interest.

Best regards,

Don Dupriest
Lockheed Martin Vought Systems
Ph. 972/603-7724 fax: 972/603-0043
[log in to unmask]


        ----------
        From:  Russell W. Furumasu [SMTP:[log in to unmask]]
        Sent:  Wednesday, August 12, 1998 7:48 AM
        To:  [log in to unmask]
        Subject:  [TN] Separating Flex Circuits

        Just a general question for the Forum.

        When individual rigid flex circuits are fabricated in arrays or
panelized,
        what are some of the techniques (manual vs machine) used for
separating
        them following assembly to prevent tearing of the flex sections?
Are any
        particular "breakaway" tab configuratons, or designs, recommended?
Any
        recommendations on positioning such tabs?  Flex core would be either
FR-4
        or polyimide; hardboard sections would be four-layer, 0,062in thick.
Any
        guidance would be appreciated.
        Thanks

        Russ Furumasu
        Rockwell Automation

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