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November 1998

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Wed, 4 Nov 1998 14:08:27 -0600
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     Dennis,

     I agree with Steve's comment on the maximum layer counts for the
     specified thicknesses.  However, it goes several steps further.
     The key to having more than the noted layer count is the PCB facility
     you use or plan to use and the H/W they have to facilitate such
     non-standard recipes.

     1. Not all shops can process cores around .004 to .006 mil range.
        Even if they claim to do so, they will have a high scrap rate
        processing the thin core material.  In-turn, this cost is passed
        onto the customer.  The chemistries are not the limitations, but
        the mechanics.

     2. You may end up using .5oz Cu on all layers, which may not work
        into your Voltage requirements (2.5, 3.3, 5 VDC).n

     3. The capital equipment needed at Lamination may not be available.
        You need proper temperature, pressure and vacuum controls
        to ensure minimal mis-registration.  If using 1-ply constructions,
        you may be faced with resin starvation, in turn showing up as
        delamination in your PCA processes.

     Again, I'm only touching the surface of what needs to be looked at.
     There are numerous variables that play into how many layers can be
     achieved with standard thicknesses.

     Try to deviate outside the normal .028, .062, .093, .125 mil finished
     thicknesses.  Nothing says you can not use .070, .075, etc.  Again,
     this issue is based on what standards you are designing to, ISA, PCI,
     VXI, etc.

     The key is the PCB facilities you end up using.

     Call me should you have further questions.

     John Gulley
     Inet Technologies Inc
     972-578-3928









______________________________ Reply Separator _________________________________
Subject: <no subject>
Author:  Dennis Ward <[log in to unmask]> at Internet
Date:    11/4/98 1:28 PM


Good afternoon,

Quick question. What is the maximum amount of layers an
.062" thick boad can contain? What about .093" thick?

Thanks
Dennis Ward
Net to Net Technologies

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