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

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=20

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Tuesday, August 23, 2005 5:48 PM
To: Larry.Smith@xxxxxxx
Cc: ray.anderson@xxxxxxxxxx; adsurevv@xxxxxxxxx; si-list@xxxxxxxxxxxxx
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=20
>flexible, almost like saran wrap.  The 3M material is good for hard=20
>boards but is about as flexible as a potato chip.  Snaps like one too,=20
>I tried it..
>
>regards,
>Larry
>
>steve weir wrote:
> > Larry, DuPont and 3M both have thin dielectric with elevated Ers=20
> > that is nice stuff.
> >
> > Some caution is warranted though depending on the specific=20
> > application.  High Er material can do good things as you said.  For=20
> > a
> given
> > skin and dielectric loss, the peak magnitude of the parallel=20
> > 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,=20
> > potentially bad if too low 2. Reduced board to discrete capacitor=20
> > 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=20
> > 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=20
> >>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=20
> >>lower impedance.  The lower power plane impedance produces more=20
> >>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=20
> >>the capacitance available to a power consumer with in a given time=20
> >>frame (i.e. 1 nSec) is the same.  This is because the velocity of=20
> >>electromagnetic propagation goes down with increasing dielectric. =20
> >>The cylindrical wavefront that goes out from a disturbance=20
> >>"uncovers" the same amount of capacitance per time, independent of=20
> >>the dielectric constant.
> >>
> >>So if you are looking for high frequency capacitance to satisfy=20
> >>those fast edges, thin dielectric is good, high dielectric constant=20
> >>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=20
> >>>thin dielectric material (~2 mil thick) to achieve the higher than=20
> >>>usual capacitance.
> >>>
> >>>Most hi-k materials are loaded with some sort of ceramic material=20
> >>>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=20
> >>>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@xxxxxxxxxxxxx=20
> >>>[mailto:si-list-bounce@xxxxxxxxxxxxx]
> >>>On Behalf Of Virendra
> >>>Sent: Tuesday, August 23, 2005 12:11 PM
> >>>To: si-list@xxxxxxxxxxxxx
> >>>Subject: [SI-LIST] [SI-LIST]: Embedded capacitance on Flex..??
> >>>
> >>>Hello All,
> >>>Does anyone have experience with embedded capacitance (wih high K)=20
> >>>on a flex circuit board? If yes, are there any issues with bending=20
> >>>the part of the flex with the high k material..?
> >>>
> >>>thanks in advance,
> >>>
> >>>virendra
> >>>
> >>>__________________________________________________
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