[SI-LIST] Re: [SI-LIST]: Embedded capacitance on Flex..??

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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