Edward -

Instead of trying to specify a specific prepreg or laminate style for PCB
construction give you vendor a nominal layer separation with applicable
tolerance and required dielectric range.  This will allow the fabricator to
make adjustments to the lay-up to meet their process as well as your
specification.  If the application is to be controlled impedance specify the
target impedance and its tolerance as well.  For general application I
specify only the overall board thickness and tolerance and a minimum
dielectric thickness for layer separation to allow my fabricator maximum
flexibility in processing.
Jeffrey A. McGlaughlin
Sr. PCB Designer
Battelle Memorial Institute
Columbus Ohio
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        -----Original Message-----
        From:   Brunker Ed [SMTP:[log in to unmask]]
        Sent:   Monday, 07 February, 2000 11:37
        To:     [log in to unmask]
        Subject:        [TN] PREPREG

        Is there anyone out there who can help me with understanding
prepreg. If we
        specify a given prepreg, (1080) does that give us any control over
board
        construction. I'm told that 1080 specifies a glass matt. So does
this mean
        that for a given glass matt the resin added to it can be as little
or as
        much as a supplier wants and the characteristics of that resin can
be
        whatever? So sheets of prepreg can be any thickness and have any
flow
        characteristics.
        Also for mobile phone usage what are people using in FR4 to achieve
        approriate dielectric characteristics? Are there a range of prepregs
being
        used or just 1080?

        Regards
        Edward Brunker

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