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August 2000

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Subject:
From:
Paul Fly <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 9 Aug 2000 14:35:45 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (374 lines)
From: Paul M Fly

Hi again,

It is interesting that Mike sent this note today, because this issue raised
its head around here
just this morning. We recently had a board built using a high dielectric
constant material between
the planes (a lot of capacitance). The board became an issue because of
$$$, it turned out to be
much more expensive than the project management thought it should be.

The vendor who built this board told us that the use of "Buried
Capacitance" which I understand
to be a name for a licensed process, adds between $1.50 and $2.00 per
square inch to the boards cost.
In this particular case that translated to $135 to $180 cost per board
added to what some people said
should be a $200 dollar board (bare board cost).

I know it seems obvious that a rather specialised process would add cost,
but I just saw a case where
this caught someone completely by surprise!

*********************************
          Paul Fly

Eastman Kodak Company
Engineering Technology Center
901 Elmgrove Rd.
Rochester, New York 14653-5313
Phone: (716) 726-5670
Fax: (716) 726-0275
E-mail: [log in to unmask]
*********************************





"Mcmaster, Michael" <[log in to unmask]> on 08/09/2000 01:43:54 PM

Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
      to "Mcmaster, Michael" <[log in to unmask]>

To:   [log in to unmask]
cc:    (bcc: Paul M Fly/243609/EKC)
Subject:  Re: [TN] Plane Capacitors




Paul and Bill

No offense taken.  The improved performance realized from building the
capacitors into the stackup is one of the reasons Merix joined the NCMS
Embedded Decoupling Capacitance (EDC) project.  The project is evaluating
various materials that have (Warning - Pun Alert!) the potential to be the
next generation replacement for the ZBC cores currently in use.  The
materials are not only thinner, but also have higher dielectric constants
resulting in much higher capacitance/area values.  The preliminary results
look very promising.  As you would expect the materials can be very
difficult to process.  And if you've ever been shocked picking up a
power/ground floor on the production floor, you can appreciate the concern
about processing materials with much higher capacitance potential.  If
you'd
like more information, I'm sure that the engineer at Merix on the
consortium
team, John Davignon, can provide you with more details.

> ----------
> From:         Brooks Bill[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Brooks Bill
> Sent:         Thursday, July 27, 2000 10:31 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Plane Capacitors
>
> Thanks Paul and Mike, I appreciate your responses...
> Has anyone ever tried using a different dielectric between the layers to
> get
> a better capacitance? Are there known problems with doing something like
> this?
> - Bill Brooks
>
>
> -----Original Message-----
> From: Paul Fly [mailto:[log in to unmask]]
> Sent: Wednesday, July 26, 2000 9:22 AM
> To: [log in to unmask]
> Subject: Re: [TN] Plane Capacitors
>
>
> From: Paul M Fly
>
> Hi gang,
>
>   I work for an OEM and not a board fabricator, so I would like to add a
> different twist to what
> Mike had to say.
>
>   Being able to put power and ground planes very close together (without
> shorting!) also builds
> a nice capacitor into your board. With materials that have higher
> dielectric constants comes even
> more capacitance! This is a great benefit in todays world of extremely
> fast
> edge rates. No offense
> to Mike ar any other fabricators reading this but that built in bypass
> capacitance is more of a
> benefit (to us at least) than being able to squeeze 16 layers into an
> 0.062" thick board!
>
>   The reason why is simple. We want to provide low impedance return paths
> for all that high frequency
> energy todays ICs spit out. Having discrete capacitors sprinkled around
> has
> two disadvantages, first
> no matter how small the footprint of those parts take up valuable real
> estate. Second is those capacitors
> may have been chosen without regard to the inductance in the routing to
> them. Which means the
> low impedance return path may not be as low as you would like, or need.
> With the power and ground
> planes configured as a "capacitor" inside the board the situation
improves
> a lot! Now that unwanted
> high frequency noise has a place to go.
>
>   My explanation is a little on the crude side, but I think any EE's
> reading this will understand.
>
> Just my $0.02,
> *********************************
>           Paul Fly
>
> Eastman Kodak Company
> Engineering Technology Center
> 901 Elmgrove Rd.
> Rochester, New York 14653-5313
> Phone: (716) 726-5670
> Fax: (716) 726-0275
> E-mail: [log in to unmask]
> *********************************
>
>
>
>
>
> "Mcmaster, Michael" <[log in to unmask]> on 26/07/2000 10:53:41
>
> Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please
> respond
>       to "Mcmaster, Michael" <[log in to unmask]>
>
> To:   [log in to unmask]
> cc:    (bcc: Paul M Fly/243609/EKC)
> Subject:  Re: [TN] Plane Capacitors
>
>
>
>
> Bill
>
> I'm running a little behind in reading my Technet.  I'm busy trying to
> keep
> our lead times down to 6 weeks :-).  I noticed you haven't gotten a
> response
> on this so I thought I'd still post a reply to your question.
>
> We build boards with standard cores as thin as 2.5 mils (single-ply 1080
> prepreg).  These can be signal/signal, signal/plane or plane/plane.  Of
> course there is also the ZBC 2.0 mil core, but it's pretty limited to
> plane/plane applications.  The challenges are about what you'd expect,
> handling, handling and handling.
>
> We also fabricate prepreg openings down to around 3 mils in thickness,
> too.
> Most of these are single-ply applications of 2313 (or similar) style
> prepreg.  The challenges here are optimizing both process and design to
> avoid low pressure areas which could result in voids and entrapped air.
> Cleanliness can also be an issue, at the material supplier and in the
> board
> fabrication process.  We and our suppliers had to invest a lot of effort
> in
> cleaning up our material handling areas to avoid shorts due to
> contamination
> from conductive particles.
>
> The benefits are fairly obvious.  How else are you going to fit 16 layers
> in
> an 0.62" thick board or maintain "reasonable" PTH aspect ratios for 26
> layer
> boards with BGAs that require .012" drilled holes unless you have
> dielectric
> openings this thin?
>
>
>
> > ----------
> > From:         Brooks Bill[SMTP:[log in to unmask]]
> > Reply To:     TechNet E-Mail Forum.;Brooks Bill
> > Sent:         Thursday, July 13, 2000 8:37 AM
> > To:   [log in to unmask]
> > Subject:      [TN] Plane Capacitors
> >
> >
> >
> >
> >
> >
> >
> >
> > To: PCB guys and gals...
> >
> > Plane Capacitors... it was the topic for discussion at PCB West in
Santa
> > Clara... have any of you had experience with manufacturing boards with
a
> 4
> > mil gap between the gnd plane and the signal layer?
> > What are the challenges you see... and did you realize any benefits
from
> > the
> > exercise?
> >
> > Bill Brooks
> > Senior PCB Designer -  <mailto:[log in to unmask]>
> [log in to unmask]
> > Zoneworx, Inc.
> > 40925 County Center Drive, STE 200
> > Temecula, CA 92591
> >  <http://www.zoneworx.com/> http://www.zoneworx.com
> > Tel: (909) 296-1226 x 1037
> > Co-Director / Education Officer / Webmaster
> > for the San Diego Chapter of the IPC Designers Council
> >  <http://www.ipc.org/SanDiego/index.html>
> > http://www.ipc.org/SanDiego/index.html
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > Thanks,
> >
> >
> >
> > Bill Brooks
> > Senior PCB Designer - [log in to unmask] <mailto:[log in to unmask]
>
> > Co-Director / Education Officer / Webmaster
> > for the San Diego Chapter of the IPC Designers Council
> > http://www.ipc.org/SanDiego/index.html
> > <http://www.ipc.org/SanDiego/index.html>
> >
> >
> >
> > Expand Your Domain!
> >   _____
> >
> >
> >
> >
> > Zoneworx, Inc.
> > 40925 County Center Dr., Suite 200
> > Temecula, CA 92591-6037
> >
> >
> > Ph: 909.296.1226 (x1037)
> > Fx: 909.296.1227
> > Visit us on the Web: zoneworx.com <http://www.zoneworx.com>
> >
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