It's unlikely that you can get a core or prepreg that will yield 0.016" with
only two plies or prepreg.  You're going to have to use three plies to meet
that thickness.  Using a prepreg/laminate combination doesn't make sense.
Your board will be built as a 12 layer construction, you'll probably be
charged more for that reason.  You'll also be paying for two pieces of
copper foil that will be etched away.

        Mike McMaster
        RF Product Engineer
        Merix Corporation
        503-992-4263


        ----------
        From:  KK Chin [SMTP:[log in to unmask]]
        Sent:  Monday, November 22, 1999 11:50 AM
        To:  [log in to unmask]
        Subject:  [TN] Multilayer PCB with re-inforced insulation

        Dear PCB experts,

        We are designing a 10-layer PCB for a lethal voltage application.
For safety
        regulatory compliance, 2 of the insulation layers must be either
double-layer
        prepreg of any thickness or a prepreg/core of at least 0.4mm
(0.016") pressed.
        Their locations are between layer 3&4 and between layer 7&8. Can you
tell me
        whether the double-prepreg or the 0.4mm prepreg/core is more
economical to make?

        As additional information, all laminates are FR4. All inner layer
circuits are
        of 1oz copper while the 2 outer layers are of 2oz copper. The board
size of
        4"x8". Overall lay-up thickness must be within 0.090".

        Thanks!

        K.K. Chin
        Artesyn Technologies,
        Fremont, CA

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