[SI-LIST] Re: [SI-LIST]: Embedded capacitance on Flex..??
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "johnandresakis" <john.andresakis@xxxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Thu, 25 Aug 2005 14:52:15 -0700
Earlier, I referred to GR-86-CORE. I used the wrong number. The spec I
should have mentioned was GR-78-CORE. In Issue 1, Sept 1997, I cannot find
a later version, Section 6.2 Multilayer PWBs- General Requirements
paragraph OC-168 it states that the minimum thickness between core
metalization layers of a multilayer PWB should be a minimum of 0.004
inches. This objective appleis between conductor layers, and between
plated though holes and conductors.
There is no breakdown voltage specification. Is there a later version that
alters this? We have not been able to find one.
There is an exception clause below this (CR6-169) that allows 0.002 mils,
but only with annual requalification by each supplier and 1 PWB from each
panel verified with 1000 VDC applied for one minute. This not done by the
fabricators I am familiar with.
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: johnandresakis <john.andresakis@xxxxxxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 8/25/2005 8:56:45 AM
> Subject: [SI-LIST] Re: [SI-LIST]: Embedded capacitance on Flex..??
>
> The issue of getting people to utilize thin dielectrics (1 mil and
> under) is to make them understand that these materials have been
> engineered to provide the necessary minimum break down voltage, both
> during initial testing and in the long term. They are not like
> typical FR4 laminates. The PCB shops test the power/ground inner
> layers at 500 volts before putting them in the boards and again at
> final electrical test. Additionally the material suppliers have
> done significant testing on the long term reliability of these thin
> dielectrics. Also, Sanmina-SCI has done extensive testing to insure
> the reliability of the products made under their license (this is
> one of the benefits of using licensed products and fabricators).
>
> As for the issue of Er versus dielectric strength, there is a
> tradeoff as was mentioned. The BC12TM material from Oak-Mitsui
> (www.oakmitsui.com) balances the properties and obtains a product
> with an Er of 10 and a dielectric strength over 6000 V/mil.
> Dupont's HK-11 is similar. These types of materials also are easier
> to process as they can flex and won't snap like a "potato chip".
> Products like Oak-Mitsui's BC16T (Er of 30) and 3M's C-Ply (Er of
> 16) could be used for distributed capacitance in backpanels,
> motherboards and cards, but I feel they are best suited
> as "singulated" (a term we are kicking around in the IPC for
> discrete capacitors formed inside the board) capacitors (and tested
> at voltages similar to discretes) or as distributed capacitance in a
> module (which typically see lower voltages).
>
> Finally, another reason why it is hard to get people to evaluate the
> technology is that the ones who are currently using it (and there
> are several) are not talking about it. They are keeping it as a
> competitive advantage and do not want to share their experiences at
> conferences or in published papers. Most of the literature is from
> academia or the material suppliers.
>
>
>
> ---
> In si-list@xxxxxxxxxxxxxxx, steve weir <weirsi@xxxx> wrote:
> > Zhiping, static applications where flex is used to make non-planar
> shapes
> > are fine with solid planes.
> >
> > Regards,
> >
> >
> > Steve.
> > At 06:10 PM 8/23/2005 -0700, Zhiping Yang \(zhiping\) wrote:
> > >Hi,
> > >
> > >I had an impression that the planes on flex are not really solid
> plane.
> > >It is more like a mesh with small holes. Is it also true for
> embedded
> > >capacitance on flex? If so, I assume it will reduce the total
> available
> > >capacitance. Can someone confirm it? Thanks.
> > >
> > >Best regards,
> > >
> > >Zhiping
> > >
> > >-----Original Message-----
> > >From: si-list-bounce@xxxx [mailto:si-list-bounce@xxxx]
> > >On Behalf Of steve weir
> > >Sent: Tuesday, August 23, 2005 5:48 PM
> > >To: Larry.Smith@xxxx
> > >Cc: ray.anderson@xxxx; adsurevv@xxxx; si-list@xxxx
> > >Subject: [SI-LIST] Re: [SI-LIST]: Embedded capacitance on Flex..??
> > >
> > >Larry, they are fun materials, aren't they?
> > >
> > >Best Regards,
> > >
> > >Steve.
> > >At 05:42 PM 8/23/2005 -0700, Larry SMITH wrote:
> > > >Steve - Yes, we have sampled both DuPont and 3M. Dupont is very
> > > >flexible, almost like saran wrap. The 3M material is good for
> hard
> > > >boards but is about as flexible as a potato chip. Snaps like
> one too,
> > > >I tried it..
> > > >
> > > >regards,
> > > >Larry
> > > >
> > > >steve weir wrote:
> > > > > Larry, DuPont and 3M both have thin dielectric with elevated
> Ers
> > > > > that is nice stuff.
> > > > >
> > > > > Some caution is warranted though depending on the specific
> > > > > application. High Er material can do good things as you
> said. For
> > > > > a
> > > > given
> > > > > skin and dielectric loss, the peak magnitude of the parallel
> > > > > resonant peak falls approximately as the inverse square root
> of Er.
> > >
> > > > > It tends to be even better than that as higher dielectric
> loss pulls
> > >
> > > > > down the peak as well. But there are some potential rocks
> in that
> > >stream:
> > > > >
> > > > > 1. Reduced board modal resonant frequencies, good for
> damping,
> > > > > potentially bad if too low 2. Reduced board to discrete
> capacitor
> > > > > parallel resonant
> > > > frequency. Can be
> > > > > a good or bad thing. Introduces more variables to discrete
> bypass
> > >design.
> > > > > 3. Increased risk of quarter wave resonance within power
> delivery
> > > > > band between discrete caps and IC die.
> > > > > 4. Much higher material cost.
> > > > >
> > > > > Best Regards,
> > > > >
> > > > >
> > > > > Steve.
> > > > > At 01:24 PM 8/23/2005 -0700, Larry Smith wrote:
> > > > >
> > > > >>Virendra - I believe that Dupont has some thin, flexible
> dielectric
> > > > >>that can be loaded with ceramic to bump up the dielectric
> constant.
> > > > >>
> > > > >>We have found that the best value comes from thin dielectric
> because
> > >
> > > > >>it both reduces inductance and increases capacitance
> resulting in
> > > > >>lower impedance. The lower power plane impedance produces
> more
> > > > >>damping, which is a good for reducing power plane resonances.
> > > > >>
> > > > >>By increasing the dielectric constant alone (no dimensional
> changes)
> > >
> > > > >>the capacitance per square area is increased but it turns
> out that
> > > > >>the capacitance available to a power consumer with in a
> given time
> > > > >>frame (i.e. 1 nSec) is the same. This is because the
> velocity of
> > > > >>electromagnetic propagation goes down with increasing
> dielectric.
> > > > >>The cylindrical wavefront that goes out from a disturbance
> > > > >>"uncovers" the same amount of capacitance per time,
> independent of
> > > > >>the dielectric constant.
> > > > >>
> > > > >>So if you are looking for high frequency capacitance to
> satisfy
> > > > >>those fast edges, thin dielectric is good, high dielectric
> constant
> > > > >>is neutral.
> > > > >>
> > > > >>regards,
> > > > >>Larry Smith
> > > > >>Sun Microsystems
> > > > >>
> > > > >>Ray Anderson wrote:
> > > > >>
> > > > >>>Typically the way I've seen it done in the past is to use a
> very
> > > > >>>thin dielectric material (~2 mil thick) to achieve the
> higher than
> > > > >>>usual capacitance.
> > > > >>>
> > > > >>>Most hi-k materials are loaded with some sort of ceramic
> material
> > > > >>>which tends to make them somewhat less than flexible which
> could be
> > >
> > > > >>>an issue with a flex board.
> > > > >>>
> > > > >>>Note that the materials people are always developing new and
> > > > >>>innovative solutions, so what was true a couple of years
> ago when I
> > >
> > > > >>>looked at the issue may no longer be the case.
> > > > >>>
> > > > >>>-Ray
> > > > >>>
> > > > >>>-----Original Message-----
> > > > >>>From: si-list-bounce@xxxx
> > > > >>>[mailto:si-list-bounce@xxxx]
> > > > >>>On Behalf Of Virendra
> > > > >>>Sent: Tuesday, August 23, 2005 12:11 PM
> > > > >>>To: si-list@xxxx
> > > > >>>Subject: [SI-LIST] [SI-LIST]: Embedded capacitance on
> Flex..??
> > > > >>>
> > > > >>>Hello All,
> > > > >>>Does anyone have experience with embedded capacitance (wih
> high K)
> > > > >>>on a flex circuit board? If yes, are there any issues with
> bending
> > > > >>>the part of the flex with the high k material..?
> > > > >>>
> > > > >>>thanks in advance,
> > > > >>>
> > > > >>>virendra
> > > > >>>
> > > > >>>__________________________________________________
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